Systems and methods for producing carboxylic acids and hydrocarbons

Abstract

A method of producing hydrocarbons includes acidifying and extracting fatty acids from a feed solution that includes fatty acid salts using carbon dioxide (CO2); separating CO2 from the extracted fatty acids; recycling at least a portion of the separated CO2 to be used as the extractant; contacting at least a portion of the extracted fatty acids with a ketonization catalyst to produce ketones; contacting at least a portion of the ketones with a hydrodeoxygenation catalyst in the presence of hydrogen to produce n-paraffins. The n-paraffins may be subjected to hydrocarbon refining to produce hydrocarbons suitable for use as a sustainable aviation fuel, a sustainable diesel fuel, or a sustainable marine fuel.

Description

SYSTEMS AND METHODS FOR PRODUCING CARBOXYLIC ACIDSAND HYDROCARBONSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of, and priority to, U.S. Provisional Patent Application Nos. 63 / 638,523, filed on April 25, 2024, and 63 / 773,880, filed March 18, 2025, the contents of which are incorporated herein by reference in their entirety.TECHNOLOGY

[0002] Provided herein are systems and methods for recovering carboxylic acids, mainly medium-chain fatty acids, using extraction from fatty acids and fatty acid salts solutions produced from buffered or unbuffered mixed-acid fermentation of organic materials and their conversion to hydrocarbons for fuel or chemical applications. Embodiments of the disclosure pertain to acidifying and / or extracting medium-chain fatty acids using gaseous, supercritical, or subcritical liquid carbon dioxide followed by conversion of the fatty acids to hydrocarbons.BACKGROUND

[0003] Organic acids such as acetic acid, propionic acid, butyric acid, lactic acid, citric acid, levulinic acid, and succinic acid, are common metabolites from bioconversion processes, in particular fermentation. The feedstocks are typically renewable resources, which represent an alternative to the chemical synthetic processes that employ fossil sources such as petroleum or natural gas. The fermentation processes, which usually take advantage of specific microorganisms or enzymes to convert carbon sources into desired organic acids, generally require neutralization with buffering agents such as caustic to control pH for optimal organism activity. Although under certain cases they can operate at low pH, the fermentation efficiency tends to be lower as the pH is reduced. Hydrolysis of complex molecules such as starches or cellulose, generally occurs at neutral pH. The produced fermentation broth is usually an aqueous stream, which consists of the desired acid product in the acid or salt form at dilute concentrations of 1-10%. If the acid products are in the saltform in this stream, they need to be converted back into the acid and recovered to produce the desired final acid product.

[0004] Productions of renewable chemicals and fuels have traditionally had a hard time competing with their petroleum-based counterparts. However, the unavoidable depletion of fossil sources along with increasing social awareness on environmental and climate effects has continuously driven the development of biotechnologies to make such renewable products from green sources. The separation technologies to recover organic acid products from fermentation broth have seen much progress with various techniques and designs studied and tested, and tremendous efforts have been pushed to advance the technologies towards more sustainable and cost-effective separations processes. For example, various methods have been reported to recover lactic acid from fermentation broth, such as reactive extraction, adsorption, electrodialysis, esterification and reactive distillation.

[0005] Efficient and cost-effective extraction processes strive to achieve several goals when performing the recovery of the acids. For example, when converting the salts to the acids through acidification (i.e., addition of acid), the methods avoid the use of certain acids, such as mineral acids, which generate salts that would then need to be disposed of and that do not allow the recovery of the buffering agent. This represents both an operating cost and an environmental concern, negatively affecting the sustainability of the process. Additionally, the methods avoid the use of extraneous extracting solvents that contaminate the product and result in raffinate losses . Such issues result in low quality products and in increased operating expenses and environmental concerns.

[0006] Mixed-culture fermentation from renewable biomass resources is an economically competitive method to convert biomass materials to renewable chemicals and fuels. Microorganisms generally produce mixtures of organic carboxylic acids such as short-chain fatty acids (SCFAs) and medium-chain fatty acids (MCFAs). The microorganisms may also produce other acids such as succinic, lactic and formic acids;, as well as alcohols such as ethanol, propanol, 1,2-propane diol and 1,3-propane diol. SCFAs are typically defined as fatty acids with carbon chain length ranging from 2 carbons (C2) to four carbons (C4), (i.e., acetic, propionic and butyric and isobutyric acids) although sometimes formic acid (Cl) is considered an SCFA. MCFAs are typically defined as fatty acids ranging from 5 carbons (C5) to 12 carbons (C12) (e.g., valeric, isovaleric, 2-methylbutyric, caproic, heptanoic, caprylic, nonanoic, decanoic, undecanoic and dodecanoic acids). The SCFAs and MCFAs may also collectively be known as volatile fatty acids (VFAs). VFAs are valuable chemical products used in food, feed, cosmetics, paints, plastics and other industries. VFAs can be chemically converted to alcohols, esters, ketones, dicarboxylic acids, and triglycerides, as well as fuel products such as gasoline, diesel, and jet fuel (sustainable aviation fuel or “SAF”). Thus, a cost-effective separation process is desired to recover high-quality VFAs from fermentation effluents.

[0007] An advantageous characteristic of mixed-culture fermentation is that it can be driven to biologically elongate the SCFAs into the MCFAs. Unextracted SCFAs and even unextracted MCFAs in the low end of the range, which are recycled with the raffinate from an MCFA extraction process may be biologically elongated into MCFAs (or longer MCFAs in the case of the unextracted MCFAs in the low end of the range) in mixed-culture fermentations.

[0008] Specifically for producing drop-in hydrocarbon biofuels (e.g., gasoline, diesel, SAF), MCFAs are preferred over SCFAs. Although it is possible to convert SCFAs to drop-in hydrocarbon biofuels, extra steps to catalytically elongate the SCFAs are necessary. Such catalytic elongation may occur using catalysts such as H-ZSM-5 zeolites to elongate alcohols or ketones produced from the SCFAs, or catalytic elongation may also occur by aldol condensation of the ketones using appropriate carbon-carbon coupling catalysts. Such catalytic elongations are cumbersome and difficult to control. On the other hand, U.S. Patent Application No. 14 / 267,841 describes simpler processes for converting medium-chain fatty acids to hydrocarbon biofuels without the need for elongation, other than ketonization of the acids or dimerization of the alcohols produced from the acids. Such processes are catalytic and occur in appropriate catalytic bed reactors. The resulting ketones or alcohols during dimerization are deoxygenated in the presence of hydrogen (i.e., hydrodeoxygenation - HDO) or without hydrogen and then further refined to produce different cuts with the required properties (e.g., higher octane, lower freezing point, viscosity) of the desired hydrocarbon products such as gasoline, jet fuel (or sustainable aviation fuel - SAF), diesel, marine fuels, and other heavies. Some gases may also be produced.SUMMARY

[0009] In one aspect, a method for extracting fatty acids from a feed solution including fatty acid salts, includes contacting the feed solution with an extractant stream including gaseous CO2, liquid CO2 or supercritical CO2 to form a mixture of extracted fatty acids and CO2; separating the CO2 from the mixture to form a separated CO2 stream; recycling at least a portion of the separated CO2 stream to the extractant stream; and contacting at least a portion of the extracted fatty acids with a ketonization catalyst to produce ketones.

[0010] In some embodiments, at least a portion of the ketones are contacted with a hydrodeoxygenation catalyst in the presence of hydrogen to produce hydrocarbons. In some embodiments, the hydrocarbons are n-paraffins. In some embodiments, the method includes refining the hydrocarbons to produce a product including C8-C16 hydrocarbons.

[0011] In some embodiments, the extracting is performed at a pressure of about 300 psig or greater. In some embodiments, the extracting is performed at a pressure of about 800 psig to about 1500 psig. In some embodiments, the extracted fatty acids include C2-C9 fatty acids. In some embodiments, the ketones include C3-C17 ketones.

[0012] In some embodiments, the method includes separating a first ketone fraction including C7-C17 ketones from the ketones, wherein the at least a portion of the ketones contacted with a hydrodeoxygenation catalyst are the first ketone fraction. In some embodiments, contacting the feed solution with the extractant stream also produces a raffinate stream, and wherein the method further includes recovering CO2 from the raffinate stream and recycling at least a portion of the recovered CO2 to the extractant stream.

[0013] In some embodiments, the method includes separating a first fatty acid fraction from the extracted fatty acids, the first fatty acid fraction including C5-C9 fatty acids, wherein the at least a portion of the extracted fatty acids contacted with a ketonization catalyst includes the first fatty acid fraction. In some embodiments, the method includes removing heavy impurities from the first fatty acid fraction prior to contacting the first fatty acid fraction with the ketonization catalyst. In some embodiments, removing the heavy impurities from the first fatty acid fraction includes using one or more of a distillation column, a falling-film evaporator, a wiped-film evaporator, a thin-film evaporator, aseparation vessel, a flash vessel, a filter, a membrane filter, and a guard bed including media for removal of nitrogen- and sulfur-containing impurities.

[0014] In some embodiments, the method is performed continuously.

[0015] In some embodiments, the method also includes: fermenting a biodegradable feedstock to produce a raw fermentation broth including the fatty acid salts; clarifying the raw fermentation broth to produce a clarified fermentation broth including the fatty acid salts; and providing the clarified fermentation broth as the feed solution.

[0016] In another aspect, provided herein is a sustainable aviation fuel including C8- C16 hydrocarbons prepared by the method.

[0017] In some embodiments, the method also includes: extracting fatty acids from a feed solution including fatty acid salts by contacting the feed solution with an extractant stream including gaseous, liquid, or supercritical CO2 to form a mixture of extracted fatty acids and CO2; separating the CO2 from the mixture to form a separated CO2 stream; recycling at least a portion of the separated CO2 stream to the extractant stream; and contacting at least a portion of the extracted fatty acids with a hydrogenation catalyst in the presence of hydrogen to produce primary alcohols.

[0018] In some embodiments, the method also includes contacting at least a portion of the primary alcohols with a dimerization catalyst to produce hydrocarbons. In some embodiments, contacting the feed solution with the extractant stream is performed at a pressure of about 300 psig or greater. In some embodiments, contacting the feed solution with the extractant stream is performed at a pressure of about 800 psig to about 1500 psig. In some embodiments, the extracted fatty acids include C2-C9 fatty acids. In some embodiments, the hydrocarbons include n-alkenes, iso-alkenes, n-paraffins, iso-paraffins, or combinations of any two or more thereof.

[0019] In some embodiments, the method further includes refining the hydrocarbons to produce a product including C8-C16 hydrocarbons. In some embodiments, the pressure is not decreased from extraction to hydrogenation to dimerization and to refining.

[0020] In some aspects, provided herein is a sustainable aviation fuel including C8- C16 hydrocarbons prepared according to the methods provided herein.

[0021] In an aspect, provided herein is a method of producing hydrocarbons, the method including: fermenting a biodegradable feedstock to produce a raw fermentation broth including fatty acid salts including a carbon chain length of C2-C9; clarifying the raw fermentation broth to produce a clarified fermentation broth including the fatty acid salts; contacting at least a portion of the clarified fermentation broth with an extractant including gaseous, liquid, or supercritical CO2 to form a first fatty acid fraction including fatty acids including a carbon chain length of C5-C9, water, and residual CO2 and an aqueous raffinate stream including unextracted fatty acid salts including a carbon chain length of C2-C4 and carbonate and bicarbonate salts; recovering the residual CO2 from the first fatty acid fraction and recycling at least a portion of the recovered CO2 to the extractant; converting an MCFA fraction into hydrocarbons including n-paraffins and / or iso-paraffins, wherein the MCFA fraction includes at least a portion of C5-C9 fatty acids of the first fatty acid fraction; and refining the hydrocarbons to form refined hydrocarbons suitable for use in a sustainable aviation fuel, marine fuel, naphtha, or diesel fuel.

[0022] In some embodiments, the method also includes stripping ammonia from the clarified fermentation broth. In some embodiments, the method also includes concentrating the clarified fermentation broth by removing water. In some embodiments, the method also includes stripping ammonia from the removed water, and recovering the stripped ammonia with an acid to produce ammonium salts. In some embodiments, the method also includes separating fatty acids having a carbon chain length of C2-C4 from the first fatty acid fraction. In some embodiments, the method also includes removing other heavy compounds or impurities from the first fatty acid fraction.

[0023] In some embodiments, the aqueous raffinate stream is recycled to the fermentation. In some embodiments, fermenting the biodegradable feedstock and neutralizing the fatty acids produced in the fermentation also produces a fermentation gas including CO2, hydrogen, and other gases, and wherein the fermentation gas is purified to produce a purified fermentation CO2 stream and wherein at least a portion of the extractant includes the purified fermentation CO2 stream. In some embodiments, converting the MCFA fraction into hydrocarbons includes: contacting the MCFA fraction with a ketonization catalyst to produce a ketonization product including C9-C17 ketones; and contacting at least a portion of the ketonization product with a hydrodeoxygenation catalyst in the presence of hydrogen to produce hydrocarbons including C9-C17 n-paraffins;wherein the refined hydrocarbons include hydrocarbons suitable for use in a sustainable aviation fuel, marine fuel, naphtha, diesel fuel, or combinations of any two or more thereof. In some embodiments, contacting the MCFA fraction with a ketonization catalyst also produces a ketonization gas including CO2, and wherein the ketonization gas is purified to produce a purified ketonization CO2, and wherein the extractant includes the purified ketonization CO2.

[0024] In some embodiments, fermenting the biodegradable feedstock also produces a fermentation gas including CO2, hydrogen, and other gases, and the fermentation gas is purified to produce a purified fermentation CO2 stream, the fermentation gas and the ketonization gas are purified in the same purification system to produce a combined purified CO2, and the extractant includes the combined purified CO2. In some embodiments, excess purified fermentation CO2 and purified ketonization CO2 not used as extractant is stored or sequestered underground or utilized for other purposes to decrease the carbon intensity of the process.

[0025] In some embodiments, contacting the MCFA fraction with a ketonization catalyst to produce a ketonization product also includes introducing a sweep or carrier gas together with the MCFA fraction. In some embodiments, the sweep or carrier gas includes CO2 or a combination of CO2 and hydrogen obtained from the fermentation gas. In some embodiments, converting the MCFA fraction into hydrocarbons includes: contacting the MCFA fraction with a hydrogenation catalyst in the presence of hydrogen to produce primary alcohols; and contacting at least a portion of the primary alcohols with a dimerization or oligomerization catalyst to produce n-alkenes, iso-alkenes, n-paraffins, isoparaffins, or combinations of any two or more thereof and with a hydrotreating catalyst to hydrotreat the n-alkenes or iso-alkenes into n-paraffins or iso-paraffins, wherein the refined hydrocarbons include hydrocarbons suitable for use in a sustainable aviation fuel, marine fuel, naphtha, diesel fuel, base oil, or combinations of any two or more thereof.

[0026] In some embodiments, the contacting at least a portion of the clarified fermentation broth with the extractant is performed in a hollow fiber membrane extractor. In some embodiments, refining the hydrocarbons includes one or more of isomerization or hydroisomerization of the hydrocarbons in the presence of hydrogen, cyclization of the n- paraffins or iso-paraffins; aromatization of the n-paraffins or iso-paraffins; or and fractionation of the hydrocarbons using distillation to achieve desired hydrocarbonproperties. In some embodiments, the pressure is not decreased from extraction to hydrogenation to dimerization or oligomerization to hydrotreating and to further refining.

[0027] In another aspect, provided here herein is a method of recovering organic acids from an aqueous solution containing organic acids salts using carbon dioxide (CO2) as a gas, wherein the CO2 both acidifies the organic acid salts into corresponding organic acids and captures the organic acids to recover them from the aqueous solution.

[0028] In some embodiments, the organic acids salts are produced from fermentation of organic feedstocks. In some embodiments, the organic acid salts are fatty acid salts and the corresponding organic acids are corresponding fatty acids. In some embodiments, the fatty acid salts and fatty acids include a carbon chain length of C2-C9 or of C5-C9. In some embodiments, the recovery of the organic acids occurs in a contactor unit. In some embodiments, the contactor unit is a contactor column or an extraction column. In some embodiments, the contactor unit is a packed column containing structured packing or random packing, a mechanically agitated column separated in stages, a bubble column, or a foam fractionation column.

[0029] In some embodiments, an operating pressure of the contactor unit is 300 psig or greater. In some embodiments, an operating pressure of the contactor unit is 600 psig or greater. In some embodiments, the aqueous solution containing the organic acid salts enters at a top of the contactor unit, while the CO2 enters at a bottom of the contactor unit. In some embodiments, excess CO2 is captured at the top of the contactor unit, is recompressed, and is recycled to the bottom of the contactor unit. In some embodiments, the excess CO2 is recompressed using a blower, a fan, a compressor, an eductor, a venturi, or a combination of any two or more thereof. In some embodiments, the CO2 separates from the recovered organic acids in the contactor unit or in a separate knockout separator.

[0030] In some embodiments, the method also includes separating dissolved CO2 from the recovered organic acids by a stripper or a distillation column. In some embodiments, the CO2 separated from the recovered organic acids is recompressed and recycled to the contactor unit. In some embodiments, the separation of the dissolved CO2 is performed at a pressure that is greater than atmospheric pressure.

[0031] In some embodiments, the contactor unit is a bubble or foam fractionation column, and wherein the contactor unit includes at least one of a sparger, a distributor, aneductor, and a venturi used to deliver the CO2 at a bottom of the column, or the contactor unit is a bubble column and includes perforated spacers positioned along a length of the bubble column, the spacers optionally supporting heating or cooling tubing along the length of the column.

[0032] In another aspect, provided herein is a method that includes: feeding the aqueous solution including organic solutes to a foam fractionation column; and providing a carbon dioxide gas feed to the foam fractionation column to produce a foam within the foam fractionation column, wherein the carbon dioxide both acidifies and captures the organic solute as it is carried over with the foam to a foam separation and recovery section or vessel.

[0033] In some embodiments, the foam fractionation column is operated at an operating pressure greater than atmospheric pressure. In some embodiments, the method also includes: separating carbon dioxide from the foam in the foam separation and recovery section or vessel; and recirculating the separated carbon dioxide, wherein the foam is produced using an eductor or a venturi configured to entrain the separated carbon dioxide in the aqueous solution.

[0034] In another aspect, provided herein is a method of producing hydrocarbons, the method including: co-processing ketones produced from the ketonization of fatty acids produced and recovered from a fermentation process with long-chain lipidic feedstocks in a hydroprocessed esters and fatty acids process wherein the co-processing includes: hydrotreating or hydrodeoxygenating the ketones and the long-chain lipidic feedstocks in the same step; separating n-paraffins including carbon chain lengths of 16 carbons or smaller; allowing a long-chain fraction including n-paraffins having carbon chain lengths longer than 16 carbons to undergo mild hydrocracking to produce a hydrocracked fraction; recombining the n-paraffins including carbon chain lengths of 16 carbons or smaller with the hydrocracked fraction; optionally isomerizing or hydroisomerizing the combined fraction; optionally fractionating the resulting hydrocarbons by distillation and; producing a hydrocarbon product suitable for sustainable aviation fuel.

[0035] In another aspects, provided herein is a method of producing a hydrocarbon product suitable for use as a sustainable aviation fuel, the method including: co-processing ketones produced from the ketonization of fatty acids produced and recovered from afermentation process with a long-chain lipidic feedstock, wherein the co-processing includes: hydrotreating or hydrodeoxygenating the ketones and the long-chain lipidic feedstock in the same step to produce n-paraffins; separating the n-paraffins into a shortchain fraction including n-paraffins having carbon chain lengths of 16 carbons or smaller and a long-chain fraction including n-paraffins having carbon chain lengths larger than 16 carbons; performing mild hydrocracking on the long-chain fraction to produce a hydrocracked fraction; combining the short-chain fraction with the hydrocracked fraction to form a combined fraction; optionally isomerizing or hydroisomerizing the combined fraction to produce an isomerized fraction; and optionally fractionating at least one of the combined fraction and the isomerized fraction by distillation.

[0036] In another aspects, provided herein is a method of producing hydrocarbons, the method including: co-processing a product from the dimerization of primary alcohols produced from the hydrogenation of fatty acids produced and recovered from a fermentation process with long-chain lipidic feedstocks in a conventional hydroprocessed esters and fatty acids process wherein the co-processing includes: hydrotreating or hydrodeoxygenating the dimerized product and the long-chain lipidic feedstocks in the same step; separating the n- paraffins and iso-paraffins including carbon chain lengths of 16 carbons or smaller; allowing a long-chain fraction including n-paraffins longer than 16 carbons to undergo mild hydrocracking to produce a hydrocracked fraction; recombining the n-paraffins and isoparaffins 16 carbons of smaller with the hydrocracked fraction; optionally isomerizing or hydroisomerizing the combined fraction; optionally fractionating the resulting hydrocarbons by distillation and; producing a hydrocarbon product suitable for sustainable aviation fuel.

[0037] In another aspects, provided herein is a method of producing a hydrocarbon product suitable for use as a sustainable aviation fuel, the method including: co-processing a product from a dimerization of primary alcohols produced from a hydrogenation of fatty acids produced and recovered from a fermentation process with a long-chain lipidic feedstock, wherein the co-processing includes: hydrotreating or hydrodeoxygenating the dimerized product and the long-chain lipidic feedstock in the same step to produce a paraffinic product including n-paraffins and iso-paraffins; separating the paraffinic product into a short-chain fraction and a long-chain fraction, wherein the short-chain fraction includes n-paraffins and iso-paraffins having carbon chain lengths of 16 carbons or smaller and the long-chain fraction includes n-paraffins and iso-paraffins having chain lengths ofmore than 16 carbons; performing mild hydrocracking on the long-chain fraction to produce a hydrocracked fraction; combining the short-chain fraction with the hydrocracked fraction into a combined fraction; optionally isomerizing or hydroisomerizing the combined fraction to produce an isomerized fraction; and optionally fractionating the at least one of the combined fraction and the isomerized fraction by distillation.BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. l is a schematic of a process for the extraction of volatile fatty acids using carbon dioxide and conversion to hydrocarbons by ketonization and hydrodeoxygenation according to an embodiment, where no separation of the extracted SCFAs is performed prior to sending the SCFAs and MCFAs to hydrocarbon conversion and refinement.

[0039] FIG. 2 is a schematic of a process for the extraction of volatile fatty acids using carbon dioxide and conversion to hydrocarbons by ketonization and hydrodeoxygenation according to an embodiment, where separation of the extracted SCFAs is performed prior to sending the MCFAs to hydrocarbon conversion and refinement.

[0040] FIG. 3 is a schematic of a process for the extraction of fatty acids using carbon dioxide and conversion to hydrocarbons by ketonization and hydrodeoxygenation according to an embodiment, where separation of the extracted SCFAs is performed and further the MCFAs are purified to remove heavy impurities prior to sending the MCFAs to hydrocarbon conversion and refinement.

[0041] FIG. 4 is a schematic of a process for the extraction of fatty acids using carbon dioxide and conversion to hydrocarbons by hydrogenation and dehydration / dimerization according to an embodiment, where separation of the extracted SCFAs is performed and further the MCFAs are purified to remove heavy impurities prior to sending the MCFAs to hydrocarbon conversion and refinement.

[0042] FIG. 5 is a schematic of a process for the extraction of fatty acids using carbon dioxide and conversion to hydrocarbons optionally by ketonization and hydrodeoxygenation or optionally by hydrogenation and dehydration / dimerization according to an embodiment, where separation of the extracted SCFAs is performed andfurther the MCFAs are purified to remove heavy impurities prior to sending the MCFAs to hydrocarbon conversion and refinement.

[0043] FIG. 6 is a process flow diagram of an integrated process, according to an embodiment, including mixed-acid fermentation to produce fatty acids, fermentation broth conditioning prior to fatty acid extraction and recovery, further conversion of the fatty acids to hydrocarbons by ketonization and hydrodeoxygenation or by hydrogenation and dehydration / dimerization and, optionally, refinement of the hydrocarbons.

[0044] FIG. 7 is a schematic of an integrated process according to an embodiment, which includes mixed-acid fermentation to produce fatty acids, fermentation broth conditioning prior to fatty acid extraction using a hollow-fiber membrane extractor with energy recovery, separation of SCFAs, and purification of MCFAs prior to conversion to hydrocarbons and refinement.

[0045] FIG. 8 is a schematic of a process according to an embodiment that uses gaseous carbon dioxide to recover fatty acids from an aqueous feed solution that contains fatty acids salts, recycles the gaseous carbon dioxide using a booster fan, and uses high- pressure distillation to separate the recovered fatty acids.

[0046] FIG. 9 is a schematic of a process, according to an embodiment, which uses gaseous carbon dioxide to recover fatty acids from an aqueous feed solution that contains fatty acids salts, recovers and recycles the gaseous carbon dioxide using a booster fan, and then uses a carbon dioxide stripper to further separate the recovered acids and to recover the carbon dioxide as a gas from that stripper.

[0047] FIG. 10A is a schematic of an extraction or contactor column, according to an embodiment, which uses gaseous carbon dioxide and operates as a bubble column with an inset schematic illustrating how carbon dioxide bubbles scavenge and thus recover fatty acids

[0048] FIG. 10B is a schematic illustrating how carbon dioxide bubbles scavenge and thus recover fatty acids

[0049] FIG. 11 is a schematic of an extraction or contactor column, according to an embodiment, which uses gaseous carbon dioxide but operates as a bubble column, wherethe bulk separation of the carbon dioxide from the fatty acids occurs in the same extraction or contactor column.

[0050] FIG. 12 is a schematic of an extraction or contactor column, according to an embodiment, utilizing gaseous carbon dioxide and operating as a bubble column, where bulk separation of carbon dioxide from fatty acids occurs in the same extraction or contactor column and it includes spacers featuring holes along the column’s length to break up bubbles, prevent back-mixing, and create staging, resulting in a decreasing concentration of fatty acids from the top (inlet of feed solution) to the bottom (exit of raffinate), thereby facilitating countercurrent operation.

[0051] FIG. 13 is a schematic of an extraction or contactor column, according to an embodiment, utilizing gaseous carbon dioxide and operating as a bubble column, where bulk separation of carbon dioxide from fatty acids occurs, with spacers featuring holes along the column’s length for the same purposes as described for FIG. 12, and additionally, the spacers support cooling or heating tubes for temperature control of the extraction process.

[0052] FIG 14 is a schematic of a high-pressure foam fractionation column, according to an embodiment, which uses a high flow of carbon dioxide to both acidify and recover fatty acids from an aqueous feed solution containing fatty acid salts, where carbon dioxide produces carbonic acid to acidify the fatty acid salts, and the high gas flow causes foam that selectively captures the resulting fatty acids, with the foam carried over to a recovery and separation section where the captured fatty acids, carbon dioxide, and part of the aqueous solution are separated and thus recovered, and the carbon dioxide and aqueous solution are recycled back.

[0053] FIG. 15 is a schematic of a high-pressure foam fractionation column according to an embodiment, with a foam spraying system to aid in breaking the foam, which uses a high flow of carbon dioxide to both acidify and recover fatty acids from an aqueous feed solution containing fatty acid salts.

[0054] FIG. 16 is a schematic of an ambient-pressure foam fractionation system according to an embodiment, which uses a high flow of gas (e.g., air, carbon dioxide) to recover fatty acid salts from an aqueous feed solution containing fatty acid salts, where the high gas flow causes foam that selectively captures the fatty acid salts, with the foamcarried over to a recovery and separation section where the captured fatty acid salts, part of the aqueous solution, and the gas are separated, and the gas may be recycled back, resulting in a concentrated aqueous solution that is then acidified with carbon dioxide to form and phase separate the fatty acids for recovery.

[0055] FIG. 17 is a schematic of the different options for downstream ketonization process for tolling, hub-and-spoke, and integration with renewable diesel and hydroprocessed esters and fatty acid SAF processes, according to several embodiments.

[0056] FIG. 18A is a flowchart of a method making ketones from a feed solution having fatty acid salts, according to various embodiments.

[0057] FIG. 18B is a flowchart of a method making a hydrocarbon product from ketones obtained from the ketonization of fatty acids and long-chain lipidic feedstocks, according to various embodiments.

[0058] FIG. 18C is a flowchart of a method making primary alcohols from a feed solution having fatty acid salts, according to various embodiments.

[0059] FIG. 18D is a flowchart of a method making a hydrocarbon product from dimerized primary alcohols obtained from the dimerization of fatty acids and long-chain lipidic feedstocks, according to various embodiments.

[0060] FIG. 19 is a graph of extraction efficiency or recovery of butyric (C4), valeric (C5) and caproic (C6) acids extracted using gaseous CO2 from an aqueous solution of fatty acid salts as a function of CO2 flowrate / feed solution flowrate ratio in a Schiebel™ mechanically agitated column at 950 psig, according to the examples.

[0061] FIG. 20 is a graph of extraction efficiency or recovery of butyric (C4), valeric (C5) and caproic (C6) acids extracted using gaseous CO2 from an aqueous solution of fatty acid salts as a function of CO2 flowrate / Acid flowrate ratio in a Schiebel™ mechanically agitated column at 950 psig, according to the examples.

[0062] FIG. 21 is a graph of extraction efficiency or recovery of butyric (C4), valeric (C5) and caproic (C6) acids extracted using gaseous CO2 from an aqueous solution of fatty acid salts as a function of pressure in a Schiebel™ mechanically agitated column at a CO2 flowrate / feed solution flowrate ratio of about 1, according to the examples.DETAILED DESCRIPTION

[0063] Definitions

[0064] Various embodiments are described hereinafter. It should be noted that the specific embodiments are not intended as an exhaustive description or as a limitation to the broader aspects discussed herein. One aspect described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced with any other embodiment s).

[0065] As utilized herein with respect to numerical ranges, the terms “approximately,” “about,” “primarily,” “substantially,” “mostly,” and similar terms will be understood by persons of ordinary skill in the art and will vary to some extent depending upon the context in which it is used. If there are uses of the terms that are not clear to persons of ordinary skill in the art, given the context in which it is used, the terms will be plus or minus 10% of the disclosed values. When “approximately,” “about,” “primarily,” “substantially,” “mostly,” and similar terms are applied to a feature (e.g., to describe its shape, size, orientation, direction, composition, etc.), these terms are meant to cover minor variations in structure or composition that may result from, for example, the manufacturing or assembly process and are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the disclosure as recited in the appended claims.

[0066] The use of the terms “a” and “an” and “the” and similar referents in the context of describing the elements (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g.,“such as”) provided herein, is intended merely to better illuminate the embodiments and does not pose a limitation on the scope of the claims unless otherwise stated. No language in the specification should be construed as indicating any non-claimed element as essential.

[0067] As used herein, the terms “capture,” “extraction,” and “recovery” may be used interchangeably. For further clarity, as used herein, the terms “capturing,” “recovering,” and “extracting” and their related words or conjugations may be used interchangeably. The word “extractant” may be used to denote the component that is scavenging, capturing, recovering and / or extracting the substance of interest. As used herein, the word “scavenge” is herein understood as the action of attracting the substance of interest, which is then captured, recovered, and / or extracted.

[0068] Embodiments are often described in a stepwise manner (e.g., describing process flow step-by-step), but the disclosure should in no manner be so limited. Although flow streams or products are often described as ‘sent’ from one location to another, the disclosure encompasses use of any and all aspects of fluid / product handling and transport (e.g., pumps, piping, vessels, etc.). Finally, although any process stream may be shown as directed to a particular destination (e.g., unit operation, vessel, system, etc.), the destination and handling of the process stream are not limited to such a depiction and it should be understood that intermediate handling or process steps may be carried out even though not explicitly mentioned or illustrated. Thus, a process stream may be sent to a flash column, a flash tank, a distillation column, combinations thereof, etc.

[0069] It should be understood that, although example implementations of the disclosed embodiments are described herein, the systems, methods, and processes may be implemented using various techniques, whether currently known or not. The present disclosure should not be limited to the example implementations, drawings, and techniques illustrated below. Additionally, the drawings are not necessarily to scale and may not illustrate obvious equipment such as flow controllers, pumps, compressors, valves, piping, additional stages (as in distillation or extraction), and instrumentation. One of ordinary skill in the art would readily understand the difference between a general process flow diagram (PFD) or a block flow diagram (BFD) and the detailed aspects of an actual process. PFDs and BFDs are described in general detail for brevity.

[0070] Carboxylic acids are classified herein according to the number of carbon atoms associated with the acid. A subset of carboxylic acids, referred to herein as volatile fatty acids (VFAs), includes fatty acids that range from one-carbon chain length to eleven- carbon chain length. These VFAs are more specifically formic acid (Cl), acetic acid (C2), propionic acid (C3), butyric acid (C4), valeric acid (C5), caproic acid (C6), heptanoic acid (C7), caprylic acid (C8), nonanoic acid (C9), decanoic acid (CIO) and undecanoic acid (Cl 1) acids. Branched VFAs, e.g., isobutyric acid (iC4) and 2-methylbutyric and 3 -methylbutyric (isovaleric acids - iC5) acids, are also contemplated.

[0071] As used herein, medium-chain fatty acids (MCFAs) are individual or mixed fatty acids with carbon numbers ranging from C5-C12 or mixtures thereof. In the processes described, MCFAs are predominantly, but not necessarily limited to, C5-C9 fatty acids. It should be understood that small quantities of CIO, Cl 1, and C12 fatty acids may also be present. In fact, C9 is also produced in small quantities in fermentation. The MCFAs may be straight-chain or branched, for example, 2-methyl butyric, iso-valeric (3-methyl butyric) and 2-methyl pentanoic, 3-methyl pentanoic and iso-caproic (4-methyl pentanoic) acids. On the other hand, short-chain fatty acids (SCFAs) are individual or mixtures of fatty acids with carbon numbers ranging from C2-C4, straight-chain or branched, for example, isobutyric acid, or mixtures thereof. It should be understood that small quantities of the shortest VFA, formic acid (Cl), and other acids such as lactic and succinic acid, may also be present.

[0072] In one aspect, the integration of the extraction of medium-chain fatty acids (MCFAs) from fermentation broths with carbon dioxide (CO2) and their subsequent conversion to hydrocarbons is described for the use as fuels. In some embodiments, the fermentation producing the fermentation broth is also integrated into the process. Advantageously, CO2 may be used as both an acidification agent and an extracting solvent or agent. Subcritical gaseous CO2, subcritical liquid CO2, or supercritical CO2 is an effective solvent or agent to extract more MCFAs compared to more polar short-chain fatty acids (SCFAs), acetic, propionic, butyric acid, and also to other polar carboxylic acids, succinic and lactic acid, thus these shorter, more polar, acids, would remain in raffinate from the extraction. U.S. Patent No. 10,662,447 describes different ways to convert and extract volatile fatty acids (VFAs) from salt solutions or fermentation broths. In particular, acidification using CO2 is of great interest because it avoids the use of mineral acids, whichcan produce unwanted byproducts and may be difficult to regenerate for reuse. CO2 can also be used advantageously as an extractant, although it is substantially limited to MCFAs (VFAs larger than valeric acid, >C5), with SCFAs (i.e., VFAs smaller than valeric acid, <C5) remaining mostly unextracted. The methods and processes disclosed in U.S. Patent 10,662,447 effectively, greenly, efficiently, and cost-effectively recover high quality VFAs from mixed VFA salt solutions through acidification and extraction, including VFA salts generated from mixed-culture fermentation, by using CO2 as the acidification agent. These methods and processes make use of some of the medium-chain fatty acids (e.g., valeric, caproic, heptanoic, and larger acids) as extractants to increase the extraction or recovery efficiency of the short-chain fatty acids (e.g., acetic, propionic, butyric acids), when they are also a desired product, in a first extraction step. Other disclosures also use only CO2 to extract the medium-chain fatty acids in a second extraction step. The use of CO2 presents an additional advantage in that the buffering agent (i.e., bicarbonates and carbonates) may be recovered and recycled to the fermentation process, thereby helping to control the pH in the fermentation. Unextracted VFAs, mostly the SCFAs, can also be recycled to fermentation for chain elongation into MCFAs, which is a common metabolic pathway performed by many microorganisms known as reverse P-oxidation (rBOX).

[0073] The low extraction efficiency of CO2 for SCFAs like acetic (C2) and propionic (C3) acid is anticipated. The extraction efficiency for butyric (C4) and valeric (C5) is moderate, with the extraction efficiency of valeric acid being higher than for butyric acid. Beyond valeric, higher acids larger than C5 are efficiently extracted by CO2. The carbon lengths of the fatty acids that are selectively and advantageously extracted by CO2 are ideal when the final intended product are hydrocarbons, specifically those for producing drop-in hydrocarbon fuels in the carbon chain length range of gasoline (C5 to CIO), jet fuel (CIO to Cl 6) and diesel (>C14), but more preferably jet fuel (CIO to Cl 6).

[0074] The unextracted SCFAs, which remain in the raffinate of the extraction process, may be recycled back to the fermentation together with the buffer (i.e., bicarbonates, or carbonates, if the bicarbonates are first decomposed by heat) to control the pH of the fermentation and to produce fatty acid salts. The recycled SCFAs are elongated to MCFAs in the fermentation by various microorganisms using the metabolic pathway known as rBOX. Such microbial chain elongation process is well studied, and often occurs inmixed-culture fermentation by a stable, self-regulating consortium of microorganisms or microbiome.

[0075] Disclosed herein are novel apparatuses, systems, and methods for converting organic salts of MCFAs produced in buffered mixed-acid fermentation into their corresponding acids, simultaneously with their extraction and recovery using CO2, and integrating this process with both the preceding fermentation and subsequent conversion to hydrocarbons. This integration is advantageous because CO2 extraction not only recovers the buffering agent to control pH in the fermentation but also selectively extracts the MCFAs preferred for downstream conversion to hydrocarbon fuels. Meanwhile, the SCFAs remain unextracted and can be recycled back into the fermentation to be elongated through rBOX to the desired MCFA chain length.

[0076] It is also noted, and as would be apparent to one of skill in the art, “process streams” described herein need not be clean cut or pure. When referring to particular product streams herein, it should be understood that, although the primary product(s) may be described, other products may exist in the product stream. Thus, there may be quantities of the other compounds in such streams and / or other impurities. For example, if referred to as MCFAs, or even purified MCFAs, commonly C5-C9 acids are used, the bulk of the C5- C9 acids stream might comprise valeric, hexanoic, heptanoic, octanoic and nonanoic acid, individually or in combinations thereof, but it may also contain, in addition to some water, small quantities of lighter fatty acids (C1-C4), heavier acids (C10-C11), CO2, salt cations, alcohols, esters, and / or impurities. Similarly, if referred to SCFAs, commonly C2-C4 are used, the bulk of the C2-C4 acids stream might comprise, acetic, propionic and butyric acid, individually or in combination thereof, but it may also contain, in addition to some water, small quantities of the heavier fatty acids (C5-C9), but also formic acid (Cl), lactic acid, succinic acid, CO2, salt cations, and / or impurities. Similarly, for example, if referred to C9-C17 ketones, the bulk of the stream might comprise of C9-C17 ketones, or C9-C16 ketones, or C9-C15 ketones, or C9-C14 ketones, or C9-C13 ketones, or C9-C12 ketones, or C9-C11 ketones individually or combinations thereof, but it may also contain, in addition to some water, small quantities of lighter ketones (C3-C8, individually or combinations thereof), unreacted C4-C9 acids, hydrocarbons, and other impurities such as, but not limited to, sulfur, nitrogen impurities. Streams said to be a combination of SCFAs and MCFAs may contain C2-C9 acids, along with small amounts of the impurities listed. Itshould also be understood that carbon chain length ranges for fatty acids, fatty acid salts, ketones, hydrocarbons, alcohols, and other molecules are provided as a general description of the size of molecules that predominantly make up the described stream, fraction, or product. A stream said to comprise C2-C9 acids, for example, need not contain significant amounts of C2 or C9. A stream said to comprise C2-C9 acids may not contain, for example, C3 acids, and can still be rightly described as a C2-C9 acid stream.

[0077] Some embodiments provide conversion of fatty acid salts exiting a fermentation into corresponding fatty acids and the simultaneous or subsequent recovery of the MCFAs through extraction of the MCFAs from an aqueous phase using CO2 as an extractant or acid scavenger. Some embodiments integrate one or more process steps into an integrated process. For example, steps including the acidification of the fatty acid salts and extraction of the resulting MCFAs may be integrated with a fermentation step producing fatty acid salts and / or with steps including subsequent conversion of extracted MCFAs to hydrocarbons. In some embodiments, the CO2 extractant is high-pressure gaseous CO2 bubbles, liquid CO2, or supercritical CO2.

[0078] In some embodiments, the integrated process may be divided into three or more sub-processes including: 1. fermentation to produce fatty acid salts and / or fatty acids, 2. acidification of fatty acid salts and extraction of MCFAs with CO2 (high-pressure gaseous, liquid, or supercritical) and recovery of the MCFAs, and 3. conversion of the recovered MCFAs to hydrocarbons for use in fuels. In some embodiments, the integrated process may also include recycling unextracted SCFAs to the fermentation. The hydrocarbon conversion may occur through two chemical pathways. The first pathway uses ketonization, where the MCFAs are converted to ketones, in addition to CO2 and water, followed then by hydrodeoxygenation (HDO) where the oxygen in the ketones is removed and any olefins are fully hydrogenated. Further hydrocarbon refinement can take place, which could be further conversions through isomerization to cause branching in the presence of hydrogen (hydroisomerization) or without, cyclization and dehydrogenation to produce cyclic hydrocarbons (naphthenes) and aromatics, and / or fractionation of the hydrocarbons to obtain the different hydrocarbon cuts, such as biogasoline, SAF, and renewable diesel. Alternatively, the ketones may undergo aldol condensation to cause branching, followed then by HDO, and then fractionation to the proper carbon lengths toobtain the different hydrocarbon cuts mentioned above. Ketones may also be converted into aromatics using certain zeolites such as ZSM-5.

[0079] The second pathway relies on hydrogenation of the MCFAs to primary alcohols then dimerization of the primary alcohols to produce hydrocarbons. Hydrogenation of the MCFAs can be direct, where the MCFAs are directly hydrogenated under proper hydrogenation catalysts. Alternatively, hydrogenating fatty acids may be performed by reacting with the MCFAs with an alcohol or with an olefin and then hydrogenolyzing the resulting ester into two alcohols, with one of the alcohols recycled to esterification or to dehydration to produce the olefin that can then be recycled to esterification. In either case, the resulting alcohols are passed through dimerization catalysts such as Beta zeolites to obtain paraffins, in addition to water. Then further hydrocarbon refining can take place, which could be further conversion through isomerization in the presence or absence of hydrogen to cause branching, cyclization and / or aromatization to create cyclic hydrocarbons (naphthenes) or aromatics (catalytic reforming), and / or fractionation to obtain the different hydrocarbon cuts, such as biogasoline, SAF, and renewable diesel. It is worth mentioning that this process can also be tuned to produce hydrocarbons in the diesel range by allowing trimerization to occur. The process is similar, using more than likely zeolite catalysts that allow trimerization.

[0080] Some embodiments provided herein pertain to integrated processes and / or systems that include a fermentation or fermentation step. The fermentation includes the anerobic digestion or acidogenic fermentation and breakdown of a feedstock by a microbiome comprising microorganisms. The feedstock for the fermentation is at least partially biodegradable. The feedstock may be synthetic in nature, or may be derived from other processes such as hydrocarbon refining, but is more preferably derived from natural sources. In embodiments where the feedstock is naturally sourced, the feedstock may include materials such as, though not limited to: biomass (including vegetation such as grasses, leaves, and wood), agricultural waste or byproducts, lumber industry waste or byproducts, food industry waste or byproducts, dairy industry waste or byproducts, municipal solid or liquid wastes, including post-consumer food waste. In some embodiments, the byproduct or waste material includes, but is not limited to, by-products or wastes from the food and agricultural industry, such as, dairy sources (including milk, milk solids, whey, whey powder, acid whey, whey permeate, lactose, or yogurt), sugars(including those derived from com, beet, palm, or sugar cane), sugar sources (including maple syrup, molasses, caramel, or soda syrup), starch and fiber sources (including those from pea, oat, barley, corn, potato, rice, wheat, milo, malt, tapioca, pasta, or bread), fruit- and vegetable-based sources (including juices, pastes, or peels), vegetable-based oils (including canola oil, corn oil, peanut oil, soybean oil, palm oil, rapeseed oil, or their derived glycerol and fatty acids), vegetable-based proteins (including soy protein, pea protein, wheat protein, com protein, or their concentrates and isolates), other protein and nutrient sources (whey, soybean meal, corn steep liquor, yeast extract).

[0081] In some embodiments, the microorganisms in the fermentation microbiome may be naturally sourced. In other embodiments, the microorganisms may be commercially-sourced or sourced from a laboratory and may include genetic modifications directed toward increased efficiency and production of target fermentation products and other characteristics. The microorganisms are selected to produce fatty acids and fatty acid salts, preferably volatile fatty acids (VFAs), preferably salts of short- and medium-chain fatty acids (SCFA and MCFA salts). For example, in some embodiments, the fermentation produces a product stream including salts of volatile fatty acids ranging from 2 to 9 carbons, namely salts of acetic (C2), propionic (C3), iso-butyric (iC4), butyric (C4), iso-valeric (iC5), valeric (C5), iso-caproic (i-C6), caproic (C6), heptanoic (C7), caprylic (C8) and nonanoic (C9) acids. The salts of the shortest VFA, formic acid (Cl), and fatty acid salts having longer carbon chains, such as C10-C12, may also be present. The microorganisms of the fermentation microbiome may also be selected for their ability to elongate fatty acid carbon chains, for example, through the reverse 0 oxidation (rBOX) pathway.

[0082] In certain embodiments, gaseous CO2 is used to recover the acids from the aqueous solutions containing MCFA salts in a more efficient manner than with liquid-liquid extraction using subcritical liquid or supercritical CO2. The embodiments reflect the ease of separation of the gaseous CO2 from the recovered acids. Other embodiments also show that bubble columns could efficiently be used to recover the MCFAs from aqueous solutions containing MCFA salts with or without the need for typical internals required for liquidliquid extraction (e.g., structured packing, sophisticated mixing mechanisms). It is known that air bubbles, as a non-polar gas, can scavenge and capture surfactants from aqueous solutions because of the non-polar (hydrophobic) tail affinity with the gas. MCFAs and their salts are considered surfactants, which do exhibit this phenomenon and more importantly, ithas been demonstrated that the undissociated acid form (R-COOH) has over 200X more affinity to the gas interface than the salts, which ensures that the undissociated acids are scavenged instead of the salts. High-pressure CO2 acidifies the MCFA salts, converting them to their undissociated acid form, which, carried by the bubbles, accumulate on the surface of the aqueous solution, forming a separate acid phase, which can be separated from the aqueous solution. Certain embodiments show these bubble columns to not have any internals. Yet other embodiments use spacers to ensure the bubbles remain fine and broken up and to avoid back mixing so that a concentration gradient is maintained from the inlet to the outlet of the aqueous solution containing the MCFA salts.

[0083] To further take advantage of using gaseous CO2 to recover fatty acids from aqueous solutions containing MCFA salts as described previously, the concept of foam fractionation is employed, allowing a much larger CO2 flow and finer bubbles to be employed to enhance recovery. The foam fractionation techniques used by others to recover other solutes using foam fractionation (e.g., per- and polyfluoroalkyl substances) formed with air, are applied in some embodiments, where CO2 at high pressure is used to both acidify the fatty acids as well as form the foam that captures and recovers such fatty acids (mostly MCFAs). The foam being a combination of the scavenged or recovered fatty acids, aqueous phase, and gaseous CO2 is allowed to leave together to a foam collection area where it is allowed to break up thus separating all three phases, and recovering the fatty acids, while recycling the aqueous solution back to the foam column and the CO2 back to the foam formation area at the bottom of the column. In other embodiments, foam formation and recovery is done at low pressure using air or CO2 to concentrate and scavenge fatty acids salts, followed by sending the recovered foam with a higher concentration of the fatty acid salts, to a high-pressure CO2 column or vessel where the salts are acidified and the fatty acids form and phase separate to be recovered, while recycling the aqueous solution, still containing some fatty acid salts, back to the low-pressure foam recovery and separation.

[0084] Other embodiments detail how the VFAs, more properly MCFAs ranging substantially from C5-C8, after conversion to their corresponding ketones, can be further converted to SAF range hydrocarbons using hydrodeoxygenation (HDO) and isomerization (ISOM, to meet cold flow properties such as freezing point) using a dedicated process, or the ketones can be co-processed in renewable diesel (RD) processes or in hydroprocessedesters and fatty acids (HEFA) processes. In RD plants or facilities, HDO and ISOM are already performed on feedstocks mostly comprising waste fats, oils and grease (FOG), vegetable oils (VO), other lipids or derivatives of these feedstocks; thus, the ketones may be simply mixed with these lipidic feedstocks and co-processed. From this process, the RD from the lipids and the SAF from the ketones are separated at the end of the process using distillation, in addition to certain lights like naphtha that is also produced and separated. A third option is to process the ketones through a HEFA process, which is designed to produce synthetic paraffinic kerosene (SPK), which is a SAF-range hydrocarbon mixture (see ASTM D7566, Annex A2). The typical HEFA process uses waste FOG, VO, other lipids or derivatives of these feedstocks and typically carries out HDO first, followed then by mild hydrocracking (MHC) to get the diesel-range hydrocarbons into the SAF range before finally performing ISOM to achieve the proper cold flow properties. Because the ketones are already in the SAF range, they need to be separated after HDO so that they do not go through MHC and get cracked, so a splitting step, such as distillation is performed to remove the SAF-range n-paraffins generated from the ketones before MHC. After MHC, the cracked product and the SAF-range n-paraffins from the ketones may be rejoined for ISOM. The final step is distillation because HEFA still produces RD and because some lights like naphtha are also produced, thus so the different cuts are fractionated. The final SPK which ends up as SAF in part comes from the ketones and in part from the lipidic feedstock.

[0085] Integration of fatty acid extraction with Ketonization / HDO

[0086] In some embodiments, as shown in FIG. 1, a feed solution 100 containing short- and medium-chain fatty acid salts is fed to an extraction column 101 or contactor. The feed solution 100, may be, but is not limited to, a fermentation broth from a fermentation process that, produces SCFA and MCFA salts. For example, the feed stream may include salts of volatile fatty acids ranging from C2 to C8 and even C9 (i.e., C2-C8 or C2-C9). Some amount of CIO, Cl 1, and C12 fatty acid salts may also be present, as well as salts of other carboxylic acids such as lactic acid (lactate) and succinic acid (succinate). Prior to being incorporated into the feed stream 100, the fermentation broth may be conditioned to remove particulate matter and other solid contaminants, such as undigested fermentation feedstock and other mineral that are prone to precipitation (e.g., phosphate). Conditioning of the fermentation broth may include one or more conditioning processesincluding: solids separation, which may be performed by centrifuge or filtration processes; suspended solids removal, which may be performed by passing the broth through filters or via membrane filtration (i.e., microfiltration, ultrafiltration, nanofiltration); concentration of clarified fermentation broth through reverse osmosis (RO) or with evaporators (mechanical vapor recompression or multiple-effect evaporator); and removal of ammonia from the broth by any suitable means.

[0087] In the extraction column or contactor 101, the feed solution 100 containing the SCFA and MCFA salts ranging substantially from C2 to C9 is contacted by an extractant stream 102 containing CO2. The CO2 in the extractant stream may be supercritical or subcritical liquid CO2 (>900 psi), or high-pressure (>300 psi) gaseous CO2. As the CO2 contacts the feed solution within the extraction column 101, the CO2 both acidifies the fatty acids salts and recovers the fatty acids. The extracted fatty acids are primarily C5 through C8 fatty acids (MCFAs), but some C9 fatty acids may also be present and be extracted. C2, C3 and C4 fatty acids (SCFAs), as well as other carboxylic acids such as lactic acid and succinic acid, which may also be present in significant quantities in the feed solutions, are poorly extracted with CO2, but a small amount of these SCFAs may also be extracted (Note: If certain alcohols are also present, such as ethanol or propanol, those may also extracted, producing esters with the acids, e.g., ethyl caproate, at the end of the extraction process). An extract phase 109 comprising the extracted fatty acids and CO2 (supercritical, liquid or gaseous) exits the column or contactor 101. Meanwhile, the aqueous raffinate 103 exits the extraction column or contactor 101 carrying the unextracted SCFA salts (e.g., C2, C3, C4 and small quantities of C5 salts) and the bicarbonates that took the place of the extracted acids. In addition, the aqueous raffinate 103 will also contain other carboxylic acid salts, such as lactate and succinate which may have been present in the feed solution 100. This aqueous raffinate 103 is depressurized by going through a pressurereducing device 108, which can be a throttling valve or an energy recovery device such as a pressure-exchanger or a turbine, which may be coupled for energy savings with other mechanical devices, such as compressors or the pressurization pump (not shown in FIG. 1) used to feed the feed solution 100 into the extraction column or contactor 101 to bring this stream 100 up to the proper pressure for fatty acid extraction and recovery. The depressurized raffinate stream 103 may optionally undergo heating or steam stripping 105 to convert the bicarbonates to carbonates and recover some of the CO2. A portion of the raffinate stream 103 may be purged 104 before, as shown, or after stripping 105. Such purgemay be useful to avoid the accumulation of species (e.g., sodium, potassium, chlorides) given that at least a portion of the raffinate stream 107 is recycled to the fermentation, with the carbonates or bicarbonates, which serve as buffering agent in the fermentation for pH control and with the unextracted acids, including SCFAs and any lactic and succinic acids, which undergo chain elongation into MCFAs by microorganisms through the rBOX pathway.

[0088] The stream carrying the CO2 extract phase 109 exiting the extraction column or contactor 101 with the extracted acids is sent to a CO2 separator 110, which can be, but is not limited to, a flash tank or a distillation column with reflux. This CO2 separator 110 may separate the CO2 from the extracted acids (mostly MCFAs and C4 acids, but small quantities of C3 and C2 acids and water may be observed) at high pressure (>300 psi), thus avoiding depressurization of the CO2 down to atmospheric pressure and saving operating expenses on having to recompress the CO2 back to the required pressures in the extraction column or contactor 101. The separated CO2 stream 111 is joined with make-up CO2 114 into the CO2 stream 112. The CO2 stream is fed to a pump, blower or compressor 113 to be pumped (if a liquid or supercritical) or compressed (if a gas) to the required pressures for use in the extraction column or contactor 101. The resulting high-pressure CO2 stream is then ready to be used in the extraction column or contactor 101 as stream 102.

[0089] Referring again now to the CO2 separator 110, the extracted acids stream 115 containing mostly C5-C9 acids (but more specifically C5-C8, as C9 is not produced in significant quantities in fermentation), a small amount of C2, C3 and / or C4 acids, and a small quantity of water and CO2, exits the CO2 separator and is fed to a ketonization reactor 116. It may be advantageous to depressurize the extracted acids stream 115 before feeding to the ketonization reactor 116. This may be accomplished by a pressure-reducing device, for example, but not limited to, going through a throttling valve 133 or other pressure or energy recovery devices, such as, but not limited to, a pressure-exchanger or a turbine. Upon depressurization, some CO2 still solubilized or entrained in the acids will be given off and may be separated from stream 115 and recovered to be recycled (not shown in FIG. 1) or it can be fed together with the acids in stream 115 into a heating device 139, such as, but not limited to, a heat exchanger to heat up stream 115, or an evaporator, to vaporize this stream 115. Optionally, a carrier or sweep gas 137, such as, but not limited to, nitrogen, helium, argon, hydrogen or, preferably, CO2 itself, or combinations thereof, can be fedtogether with stream 115 into the heating device 139, forming stream 138. After the heating device 139, stream 138, which may be a heated liquid and / or a vaporized stream, is fed into the ketonization reactor 116. In this regard, the CO2 released from the acid stream 115 after depressurization with a pressure-reducing device 133 such as, but not limited to, a throttling valve or an energy recovery device such as a turbine or a pressure exchanger, can serve partly or wholly as the carrier or sweep gas if the option of not separating this CO2 is chosen. The carrier or sweep gas aids in moving the reactants and products along, which is important given that any water present in the feed 138 and further water produced in the ketonization reaction can cause reaction inhibition. The use of CO2 as the sweep or carrier gas has advantages as CO2 is produced within the ketonization reaction and, after purging the excess and some optional clean-up, can be directly recycled thus avoiding having to separate the CO2 produced in the ketonization from a different gas (see, e.g., U.S. Patent 10,968,398). In addition, some hydrogen (H2) may also be produced during ketonization, which has been shown to improve catalytic activity and can increase catalyst long-term stability by minimizing deactivation through inhibition of coke formation; thus, if the CO2 from ketonization is recycled, so will the H2, which can be supplemented with external H2 such as, but not limited to, from fermentation after H2 is separated from the fermentation gas or biogas after clean-up. This is possible as H2 is produced in acidogenic mixed culture fermentation where methane has been inhibited as it is proposed in this invention to preserve the VFAs from methanogenic degradation and to enhance chain elongation (i.e., rBOX). In fact, H2 in mixed culture fermentation under methane inhibition can reach levels above 30% with the remaining being mostly CO2, thus it could be advantageous, after removing any sulfur species (e.g., hydrogen sulfide, mercaptans) and other impurities from the fermentation gas, to use the clean fermentation gas containing CO2 and H2 as the sweep or carrier gas for ketonization (further description shown in reference to FIG. 6). CO2, unlike water, has not been observed to cause significant ketonization reaction inhibition in some catalysts but CO2 inhibition has been observed in others. It is hypothesized that the difference lies on the type of catalysts. More acidic catalysts such as zirconium oxide (ZrCh) do not tend to be inhibited by CO2 as much, but basic catalysts such as cerium oxide (CeCh) do because it is theorized that the acidic CO2 binds to the active sites of the basic catalysts. When CO2 inhibition is observed, it is possible to use the ketone product itself as the sweep or carrier gas in vapor phase ketonization, by recycling part of the produce ketones after separating the CO2 and water (not show in FIG. 1).

[0090] In the ketonization reactor 116, the extracted acids are converted to ketones, CO2, and water according to the following reaction scheme:Ri-COOH + R2-COOH Ri-C(O)-Ri + CO2 + H2O

[0091] In the above reaction scheme, Ri and R2 may be straight or, in minor quantity, branched carbon chains ranging from 1 to 7 (or 8) carbons in length. As a result, the ketones may include from C3-C17 ketones, inclusive. For example, C3 ketone (acetone), is produced when two acetic acids react, while C17 ketone (heptadecanone) is produced when two nonanoic acids react. The ketones may include straight chain and branched carbon chains as when some of the iso-acids (e.g., isobutyric acid, isovaleric acid) react to form ketones. During ketonization some small amount cracking, decarboxylation or dehydrogenation may occur, so some alkanes and alkenes may form. The catalyst employed in the ketonization reactor 116 may be, but it is not limited to, any of several types of metals oxides, such as, but not limited to, amphoteric (reducible) metal oxides, such as, but not limited to, cerium oxide (CeCh), titanium dioxide (TiCh), manganese (IV) dioxide (MnCh), zirconium oxide (ZrCh), pristine (unmodified) or modified in any suitable way necessary, for example, but not limited to, TiCh may be anatase, ZrCh may be sulfated, CeCh maybe combined with copper, binding agents, such as, but not limited to alumina (AI2O3) may be employed with these catalysts and any combination of any two or more of these metal oxides or modifications. The ketonization reactor 116 may be operated at temperatures >200°C and at atmospheric pressures, or at other temperatures and pressures adequate to result in the desired reaction ketone yields and rates. The ketone, water, and CO2 product stream 117 goes to a phase separator 118 (such as a knockout or three-phase separator) after optionally being cooled down by any suitable means (e.g., heat integration with heating device 139, where the product stream 117 is used to preheat the incoming feed stream 138, while allowing stream 117 to cool down - this optional cooling step is not shown in FIG. 1). In the phase separator 118, the ketone phase, the water phase, and the gas phase are separated from each other.

[0092] Short-chain ketones, such as those having a carbon length of C3 through C6, which are a result of the ketonization of the SCFAs (<C4), are at least somewhat soluble in water; therefore, some of the ketones of this size, if present, will end up in the water phase 123. If the ketone concentration in this water phase is significant, this water phase 123 can be sent to a system that can recover the ketones, such as a liquid-liquid extraction system,where ketones having a carbon chain length greater than C6, which are more insoluble in water, are used as the extractant (not shown in FIG. 1). Nevertheless, a small amount of SCFAs should be extracted in contactor 101; therefore, the resulting amount of short-chain ketones (C3-C6) would also be small thus minimizing the presence of ketones in water stream 123. The water phase 123 containing a small amount of short-chain ketones may be recycled to fermentation, where if such is a mixed cultured fermentation or anaerobic digestion, there will be microorganisms there that will be able to convert these ketones into acids. Alternatively, this water phase 123 can also be sent to a wastewater treatment process either anaerobic digestion for methanogenic biogas production or aerobic treatment or both.

[0093] Full conversion of the extracted acids fed into ketones is preferred. However, pushing for high conversion could be uneconomical as the kinetics are negatively affected as the partial pressure of the acids decreases and the inhibitory effects of water of reaction increases with increasing conversion; therefore, getting full conversion could require a very large, possibly uneconomical, reactor. Ketonization kinetics may be improved with increasing temperature. However, increasing temperature to increase conversion could also result in cracking and / or decarboxylation of the reactant acids or the ketones, thus producing short hydrocarbons (e.g., but not limited to, methane, ethane, propane, butane, pentane, hexane, and their corresponding alkenes) even though the acids are highly converted. The short hydrocarbons are considered losses when jet fuel range hydrocarbons (C8-C16) are the target for the hydrocarbon product, thus minimizing cracking and decarboxylation is important. Minimizing cracking and decarboxylation may involve lower reactivity by, for example, decreasing temperature, which could result in unconverted acids. Preferred conversions are such that the resulting yield of ketones is >95% of the stoichiometric yield, but more preferably >98%, and more preferably >99%. Any unconverted acids would remain in both the water 123 and the ketone phases 119.Unconverted MCFAs, which tend to be less-polar, will substantially dissolve into the ketone phase 119, whereas unconverted SCFAs will collect in the aqueous phase 123. The unconverted acids that remain in the water phase 123 may be recycled back to either the fermentation or to the acid extraction process, thus avoiding loss of the unconverted acids. However, the unconverted acids that are carried by the ketone phase 119 will be hydrodeoxygenated downstream and be converted into short-chain alkanes, which will likely fall in the low naphtha range (C4-C8). These short-chain alkanes may be of lower value compared to SAF. Optionally, the acids carried by the ketone phase 119 can berecovered by washing the ketones with caustic or alkali (e.g., but not limited to, sodium hydroxide, potassium hydroxide or their carbonates) and such that the acids are captured by a resulting water phase, allowing the resulting water phase to be recycled to the acid extraction process or to the fermentation. The expected ketones (z.e., >C7 for C4+ acids) are quite insoluble in water e.g., 4-heptanone is about 0.5% w / w soluble in water with solubility decreasing as molecular weight increases for larger ketones), thus an alkali wash of the ketone phase 119 would not be expected to cause much ketone losses into the alkali solution.

[0094] The CO2 formed 120 during ketonization together with the CO2 106 exiting the raffinate heater or steam stripper 105 and, optionally, the CO2 vented (not shown in FIG. 1) from stream 115 after it is depressurized, can be recycled back to a compressor (or compressors) 122. Make-up CO2 121 may be needed due to the consumption of CO2 into carbonates and bicarbonates leaving with the raffinate from the acidification / extraction process and other losses. Any needed make-up CO2 is provided to compressor 122 as well together with the CO2 recycle streams 106 and 120. The make-up CO2 may preferably come from the gas generated in the fermentation after appropriate cleanup or it may be externally purchased or procured. The pressurized CO2 stream 114 exits compressor 122 and is cooled to the proper temperatures (cooler or cooling heat exchanger not shown) prior to joining stream 111 to form stream 112, which is at the proper pressure to be then pumped or compressed by pump or compressor 113 to the proper pressure for acidification / extraction in extraction column or contactor 101.

[0095] The ketone phase 119 will contain most of the ketones having a carbon length of C7 through Cl 5 (or Cl 7) along with a small quantity of the C3 through C6 ketones. The ketone phase 119 is fed to a hydrodeoxygenation (HDO) reactor 124, where the ketones in the ketone phase are reacted with hydrogen provided by a hydrogen feed stream 125 in the presence of a hydrodeoxygenation catalyst. The ketones are hydrodeoxygenated to form stream 126, which comprises C7-C17 n-paraffins, a small quantity of C3-C6 n-paraffins and water. The HDO catalyst may be, but is not limited to, a sulfided hydrotreating catalyst, such as nickel-molybdenum on alumina (NiMo / AhOs) or cobalt-molybdenum on alumina (CoMo / AhOs), or precious metal catalysts, such as platinum on alumina (Pt / AhOi) or Pd of alumina (Pd / AhOi). A hydrotreating catalyst is preferably understood as a catalyst that is capable of converting unsaturated carbon-carbonbonds into saturated carbon-carbon bonds but these same types of catalysts may also effect hydrodeoxygenation as a catalyst that is capable of removing oxygen and other heteroatoms such as nitrogen and sulfur. In this case, any oxygen, and any nitrogen, and sulfur impurities will be removed. These impurities will leave as water in the case of oxygen, or as ammonia and hydrogen sulfide in the case of the nitrogen and sulfur impurities. For further clarity, a HDO catalyst is a hydrotreating catalyst that is performing deoxygenation (oxygen removal) while hydrotreating. Further separation in a phase separator 134 (e.g., a knockout separator, three-phase separator, or other separator) is needed for removal of the water 135, and / or ammonia and hydrogen sulfide removal (not shown in FIG. 1).

[0096] The HDO reactor 124 is operated at temperatures and pressures appropriate for the selected HDO catalyst. For example, the HDO reactor 124 may be operated at conditions above 900 psig and 200°C or at pressures above 400 psig and 300°C. In some embodiments, the HDO reactor 124 is operated at a temperature of about 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, or even greater than 500°C, and at a temperature less than 1000°CIn some embodiments, the HDO reactor 124 is operated at a pressure of about 50 psig, 100 psig, 150 psig, 200 psig, 250 psig, 300 psig, 350 psig, 400 psig, 450 psig, 500 psig, 550 psig, 600 psig, 650 psig, 700 psig, 750 psig, 800 psig, 850 psig, 900 psig, 950 psig, 1000 psig, 1050 psig, 1100 psig, 1150 psig, 1200 psig, 1250 psig, 1300 psig, 1350 psig, 1400 psig, 1450 psig, 1500 psig, or a pressure greater than 1500 psi. In some embodiments, the HDO reactor 124 is operated at a pressure of 2000 psig, 1900 psig, 1800 psig, 1700 psig, 1600 psig, 1500 psig, or less. Further separation equipment 134, such as a knockout phase separator or three-phase separator, may be required for removal of the water 135, ammonia and hydrogen sulfide (not shown in FIG. 1). The HDO theoretical reaction and the overall reaction with ketonization is as follows: ygenation)(Overall reaction)

[0097] In the equations, Ri- and R2- are each independently CH3-(CH2)n-, where n ranges from 2 to 6, if the fatty acid extraction system has selectively extracted mostly MCFAs ranging from C5 to C8 and a small quantity of C4. The n may range from 2 to 7 when C9 fatty acids are included in the feed.

[0098] Finally, a paraffin stream 136 containing the resulting n-paraffins can be separated using equipment such as, but not limited to, a distillation column or system 127 into the one or more cuts having the proper carbon length ranges according to the desired products, such as, but not limited to, heavies 128 which are mostly tars formed by the conversion from impurities, the C14-C17 cut 129, which will be the diesel cut, the C8-C16 cut 130, which will be the sustainable aviation fuel (SAF) cut, the C5-C10 cut 131, which will be the gasoline cut, and finally, the C3-C4 cut 132, which will be mostly gases which can be either processed (e.g., pressurized) to be sold as such, or used internally in the facility for heat or in a steam reformer to make hydrogen.

[0099] The resulting n-paraffins cuts can be blended into compositions suitable for use as biogasoline, diesel, and / or SAF. For biogasoline, the n-paraffins will require isomerization to produce branching, which is needed for increasing the octane value of the fuel. Production of SAF will also require conversion of a portion of the n-paraffins into branched iso-paraffins using isomerization. SAF may also require aromatics, which can be obtained via cyclization / dehydrogenation or similar reaction pathways. However, as a blendstock, the n-paraffins and the iso-paraffins after isomerization should suffice.

[0100] Also disclosed herein, although not shown in FIG. 1, is the hydrogenation of the acids in stream 115 to primary alcohols followed by dimerization / dehydration to paraffins. In this process, unlike ketonization that may occur at atmospheric pressure, hydrogenation and dimerization / dehydration occur at high pressures (e.g., >300 psi).Therefore, full pressure reduction to atmospheric pressure is not required after CO2 separation. This improves the efficiency of the process by avoiding pressure swings. In contrast, ketonization followed by HDO (as shown in FIG. 1) typically requires pressure reduction to atmospheric pressure for ketonization and then re-pressurization to high pressures for HDO. Also, unlike ketonization, the dimerization process can be tuned to go beyond dimers to trimerization, which would then produce diesel-range hydrocarbons or larger, such as carbon chain-lengths needed to produce marine oils and base oils.

[0101] Integration of fatty acid extraction, SCFAs recovery and ketonization / HDO

[0102] The embodiments illustrated in FIG. 1 have the drawback that some of the SCFAs that were extracted (i.e., small amounts of C3 and C2) may be lost. Firstly, the SCFAs may be lost as short-chain ketones in the water stream 123 and then, those short-chain ketones that make it to HDO, may also be lost as C3-C4 gases 132 after HDO and distillation. The extracted SCFAs are better utilized if they are instead separated first and potentially sold to other valuable markets, such as food and feed markets, or recycled to fermentation for chain elongation into MCFAs. In addition, in the embodiments illustrated in FIG. 1, some water is also captured with the acids during extraction which when fed to the ketonization reaction causes water inhibition, making the ketonization process less efficient and therefore requiring a larger / longer ketonization reactor 116. A process in which these SCFAs are recovered and the absorbed water is removed prior to ketonization is shown FIG. 2. The processes and systems illustrated in FIG. 2 are similar to those shown in FIG. 1, with most of the streams and equipment in FIG. 2 (labeled with a 100 number) corresponding to the streams and equipment of FIG. 2 (labeled with a corresponding 200 number). For example, the feed stream 100 in FIG. 1 corresponds to the feed stream 200 in FIG. 2. Descriptions of the streams, equipment, and processes previously described in relation to FIG. 1 apply to the corresponding streams, equipment, and processes illustrated in FIG. 2 except for the differences that are described below, specifically relating to the inclusion of a CO2 knockout separator or flash tank 240 and a water / acid separation step performed in a separation system 236 provided after the depressurization by pressure reducing / energy recovery device 233 of the acid stream 215 after exiting the high-pressure CCh / acid separation equipment 210. Additional differences will become apparent by the following description.

[0103] As illustrated in FIG. 2, in some embodiments a process may include an acid separation stream. In this step, an extracted acid stream 215 exiting the high-pressure CO2 separator 210 is depressurized by a pressure reducing or energy recovery device 233, such as, but no limited to a throttling valve or a pressure exchanger or turbine to recover energy. Upon depressurization, some CO2 still solubilized or entrained in the acids will be given off and may be separated from stream 115 using, for example, a knockout separator or flash tank 240, which may be recovered and recycled as stream 241. Optionally, heat may be provided to unit 240 to enhance CO2 release. The CO2-lean acid stream 242 leaving the knockout or flask tank unit 240 is sent to a water / acid separation system, such as, but not limited to, a distillation column, or an evaporator 236. The water / acid separation system 236 separates the SCFAs (C2-C4 acids) and the water into a light acid / water stream 234, the SCFAs of which may be then recovered. Alternatively, or in addition, the light acid / water stream 234 may be sent together with the raffinate stream 207 to the fermentation tocontinue to elongate through the rBOX pathway. As a result of the separation of the SCFAs in the water / acid separation system 236, a medium-chain fatty acid stream 235, which substantially consists of MCFAs (C5-C9 but more specifically C5-C8, as C9 is not produced in significant quantities in fermentation), is also produced. The medium-chain fatty acid stream 235 including C5-C9 MCFAs is sent into a heating device 245, such as, but not limited to, a heat exchanger to heat up stream 235, or an evaporator, to vaporize the MCFA stream 235. Optionally, a sweep gas 243, such as, but not limited to, nitrogen, helium, argon, hydrogen or, preferably, CO2 itself, or combinations thereof, can be fed together with the MCFA stream 235 into the heating device 245, forming heated MCFA stream 242. After the heating device 245, the heated MCFA stream 242, which may be a heated liquid and / or a vaporized stream, is fed into the ketonization reactor 216. As mentioned in the context of FIG. 1, which also applies to FIG. 2, the sweep gas aids in moving the reactants and products along, which is important given that any water present in the feed 235, which has been substantially reduced due to the water / acid separation step 236, and further water produced in the ketonization reaction can cause reaction inhibition. The use of CO2 as the sweep gas has advantages in that CO2 is produced within the ketonization reaction and, after purging the excess and some optional clean-up, can be directly recycled, thus avoiding having to separate the CO2 produced in the ketonization from a different gas before it goes to a ketonization reactor 216. Unlike water, CO2 has not been observed to cause significant ketonization reaction inhibition in some catalysts, though some inhibition by CO2 has been observed in other catalysts. It is hypothesized that the difference lies on the type of catalysts, but the present disclosure is in no way bound by this theory. Acidic catalysts such as zirconium oxide (ZrCh) do not tend to be inhibited by CO2, but basic catalysts such as magnesium oxide (MgO) do because, it is theorized, the acidic CO2 binds to the active sites of the basic catalysts. When CO2 inhibition is observed, it is possible to use the ketone product itself as the sweep or carrier gas in vapor phase ketonization, by recycling part of the produced ketones after separating the CO2 and water, an option not shown in FIG. 2. As mentioned above for FIG. 1, H2 from any source, including fermentation, may also be optionally included in the mix of sweep gases, which has the potential of minimizing catalyst deactivation caused by coking.

[0104] After undergoing the ketonization reactions in ketonization reactor 216 using catalysts and conditions similar to those prescribed earlier with reference to FIG. 1, the resulting ketonization product stream 217 is passed through a phase separator unit 218 (suchas, but not limited to, a knockout phase separator or a three-phase separator) after optionally being cooled down by any suitable means (e.g., heat integration with heating device 245, where the product stream 217 may be used to preheat the incoming feed stream 242 while cooling stream 217 - an optional step that is not shown in FIG. 2). In the phase separator unit 218, the CO2 gas phase, the ketone phase, and the water phase are separated from one another.

[0105] Similar to the processes and systems depicted in FIG. 1, the resulting CO2 phase 220 is sent together with the CO2 206 recovered from the raffinate and the vent CO2 stream 241 from the post-depressurization knockout separator or flash tank 240 to a compressor 222 to replenish some of the CO2 consumed in acidification / extraction process carried out in the extraction column or contactor 201. The ketone phase 219 will substantially consist of C9-C17 ketones with very little of the smaller ketones. Thus, the water phase 223 will also contain little to no dissolved ketones, as >C9 ketones are substantially insoluble in water. The water phase 223, which will not contain much of the short ketones, may be recycled to fermentation or to wastewater treatment steps.

[0106] The ketone phase 219 containing the C9-C17 ketones is sent to the HDO reactor 224, where hydrogen 225 is fed in the presence of an HDO catalyst as described earlier with reference to FIG. 1 to remove any oxygen, nitrogen, or sulfur present, and to saturate carbon-to-carbon bonds. The paraffin stream 226 carrying the resulting n-paraffins and water from hydrodeoxygenation is sent to a phase separator knockout 237 to remove any water 238. Further clean-up of ammonia and / or hydrogen sulfide may also take place. The separated n-paraffins 239 may then be sent to a separation system 227, such as, but not limited to, a distillation system, where the different cuts are separated to produce valuable product streams. A heavies stream 228, consisting mostly of tars formed from impurities, is removed from the bottoms of the separation system 227. Streams containing diesel (comprising primarily C14-C17 n-paraffins) 229 and SAF (comprising primarily C9-C16 n-paraffins) 230 are also obtained. Some minor amount of gases may also be produced and separated into a gas stream 232, which may be used to produce energy, reformed into hydrogen, or flared as needed.

[0107] The embodiment illustrated in FIG. 2 is intended to maximize the cuts most suitable for SAF, provide some for diesel production, and minimize or avoid the biogasoline cut. This embodiment also reduces the ketonization water inhibition and losses of theshorter ketones in the water phase after ketonization and losses as gases after HDO by preemptively separating in the water / acid separation system 236, the water and SCFAs, which would otherwise be present in the feed to ketonization; therefore, this system constitutes operational savings and increased efficiencies in processing when compared to the embodiment in FIG. 1, at a relatively small capital cost for the additional equipment.

[0108] Integration of fatty acids extraction, SCFA recovery and ketonization / HDO with additional purification ofMCFAs

[0109] As illustrated in FIG. 3, in some embodiments the process may include steps to purify the MCFAs before the ketonization reactions. Additional modifications to downstream process steps produce primarily hydrocarbons suitable for use as SAF. The first steps of the process depicted in FIG. 3, including the extraction of fatty acids by CO2 and the subsequent separation and recycle of the CO2, are similar to the embodiments illustrated in FIGS. 1 and 2, with streams and equipment 100-115 and 133 and 200-215 and 233, respectively corresponding to the streams and equipment 300-315 and 333 of FIG. 3. As such, the previous description of the streams and equipment 100-115 and 133 and 200-215 and 233 of the earlier processes and systems illustrated in FIG. 1 and 3 applies to the streams and equipment 300-315 and 333 of the process illustrated in FIG. 3 and so will not be repeated here. Additional similarities exist in the CO2 compressors 122, 222 and 322 and CO2 make-up 121, 221 and 321. Further, the CO2 separation after depressurization of acid stream 215 performed in FIG. 2 using the knockout separator or flash tank unit 240 and resulting in CO2 vent stream 241 and CCh-lean acid stream 242 is also similar and corresponds to the knockout separator or flash tank unit 340 and resulting CO2 vent stream 341 and CCh-lean acid stream, thus the description for 240, 241 and 242 above also applies to 340, 341 and 342.

[0110] According to FIG. 3, in some embodiments the extracted acid stream 315 exiting the CO2 separator 310 is fed to a water / acid separation unit 316, such as a distillation column, an evaporator, or other separation equipment. The extracted acid stream 315 may first be passed through a pressure-reducing device 333, such as a throttling valve or other pressure or energy recovery device, such as, but not limited to a pressure exchanger or a turbine, and then once depressurized, CO2 may be further removed 341 in knockout separator or flash tank 340 and recycled with stream 306 and 328 to compressor (or compressors) 322 in a manner similar to what was described for the corresponding streamsand equipment in FIGS. 1 and 2. Optionally, heat may be provided to unit 340 to enhance CO2 release. The CO2-lean acid stream 342 is then fed to water / acid separation unit 316. The water / acid separation unit 316 separates the water and light acids out to produce a water / light acid stream 317 that includes most of the extracted SCFAs. The water / light acid stream may be optionally sent to the fermentation for chain elongation using the rBOX pathway, or the light acids may be captured for other uses. A medium-chain fatty acid stream 318 is also produced at the water / acid separation unit 316, the medium-chain fatty acid stream primarily comprising MCFAs. The medium-chain fatty acid stream 318 is fed to a purifier 319, which may be, but is not limited to, one or more units in series or by itself, consisting of a distillation column, a falling-film evaporator, a wiped-film or thin-film evaporator to handle high viscosities, separation vessel, flash vessel, filter, membrane filter, a guard bed with proper media for removal of nitrogen- and sulfur-containing impurities or other equipment suitable for separating the heavy impurities from the MCFA stream to remove heavy impurities or other impurities that may be present in the stream 318 into a waste stream 320. Examples of heavy impurities that may be removed by this step include cations such as sodium and potassium with their MCFA counter anion (e.g., sodium and potassium salts of caproate, heptanoate, caprylate), longer chain fatty acids, long chain hydrocarbons, large-molecular-weight organic compounds such as fats and oils, and, although to a lesser extent, microbial debris from the fermentation, and inorganic compounds, such as other salts and minerals from the fermentation broth feed. Other nitrogen- or sulfur-containing impurities that are absorbed into certain media, which can become catalyst poisons may also be removed in a guard bed. This heavy impurity stream 320, which could contain MCFA salts, may be partly or wholly recycled back to the extraction column or contactor 301 with the feed solution 300 to recover at least part of the MCFAs and minimize losses.

[0111] The purified MCFA stream 323 is fed into a heating device 345, such as, but not limited to, a heat exchanger to heat up the purified MCFA stream, or an evaporator, to vaporize this stream if it is in a liquid form as it exited purifier 319. However, if the purified MCFA stream 323 is desired as a vapor, it is preferred for better energy efficiency to avoid condensation and obtain such stream directly as a vapor from the purifier unit 319. If the purifier unit 319 is a distillation column, a partial condenser may be employed at the top to allow reflux, while avoiding full condensation so that vapors may exit this unit and be sent directly without any condensation to heating device 345, which is then only used to bringthe vapors up to reaction temperature prior to feeding into ketonization reactor 324. If, on the other hand, the purifier unit 319 is an evaporator, vapors from the evaporator may be sent directly without any condensation to heating device 345. As another option, it may be desired to perform the ketonization reaction with the acid stream 323 fed in a liquid form, in which case condensation after the purifier unit 319 might be needed. Nonetheless, because ketonization is known to require temperatures above 200°C and preferably above 300°C, liquid-phase ketonization might need to be performed at higher pressures and a pressurization device (e.g., a pump) might also be needed to get the purified MCFA stream 323 to the proper pressure prior to feeding it to heating device 345 to heat it up to the proper reaction temperature. Optionally, a sweep gas 343, such as, but not limited to, nitrogen, helium, argon, hydrogen or, preferably, CO2, or combinations of these gases, can be fed together with the purified MCFA stream 323 into the heating device 345, forming heated MCFA stream 344. The heated MCFA stream 344, whether as a heated liquid and / or a vaporized stream, is fed into the ketonization reactor 324. As discussed in the context of FIG. 1 and FIG. 2, the sweep gas aids in moving the reactants and products along. This is important given that any water present in the feed 323, which has been substantially reduced due to the water / acid separation step 316, and further water produced in the ketonization reaction, can cause reaction inhibition. The use of CO2 as the sweep gas has advantages in that CO2 is produced within the ketonization reaction and, after purging the excess and some optional clean-up, can be directly recycled thus avoiding having to separate the CO2 produced in the ketonization from a different gas (see, e.g., U.S. Patent 10,968,398) before it goes to a ketonization reactor 324. And, as previously mentioned, CO2, unlike water, has not been observed to cause significant ketonization reaction inhibition in some catalysts. However, CO2 inhibition has been observed in other catalysts. When CO2 inhibition is observed, it is possible to use the ketone product itself as the sweep or carrier gas in vapor phase ketonization, by recycling part of the produced ketones after separating the CO2 and water, an option not shown in FIG. 2. As mentioned above for FIG. 1, H2 from any source, including fermentation, may also be optionally included in the mix of sweep gases, which has the potential of minimizing catalyst deactivation caused by coking.

[0112] In the ketonization reactor 324, the MCFAs undergo ketonization reactions to produce C9-C17 ketones, CO2, and water. The ketonization product stream 325 is then separated in a phase separator 326, such as, but not limited to, a knockout separator orthree-phase separator, after optionally being cooled down by any suitable means (e.g., heat integration with heating device 345, where the product stream 325 is used to preheat the incoming feed stream 344, while cooling the product stream 325. The phase separator 326 produces a gas phase 328 comprising CO2, an aqueous phase 327 comprising water, and a separated ketone phase 329 comprising the C9-C17 ketones. The CO2 may be recycled upstream to reduce the amount of makeup CO2 required by the process. The ketone phase 329 along with a hydrogen stream 331 is fed to an HDO reactor 330 having an HDO catalyst as previously described to hydrodeoxygenate the ketones and produce C9-C17 n- paraffins and water, which is HDO product stream 338. The HDO product stream 338 is then separated in a phase separator unit 332, such as a knockout phase separator, which produces another aqueous phase stream 339 comprising primarily water, and a hydrocarbon phase stream 334 that includes the C9-C17 n-paraffins. The hydrocarbon phase stream 334 carrying the C9-C17 n-paraffins is fed to hydrocarbon refining units 335 where, optionally branching of the n-paraffins may be induced to meet certain specifications for SAF, such as freezing point. Linear n-paraffins are converted to branched alkanes (isoparaffins) using isomerization. Isomerization may be performed in the presence of hydrogen, which is known as hydroisomerization; thus, an optional hydrogen stream 336 may be provided to the hydrocarbon refining units 335. In some operations, HDO and hydroisomerization may occur in the same reactor under the same conditions of temperature and pressure and with the same catalyst. Isomerization or hydroisomerization catalysts are catalysts capable of producing branching in linear alkanes or n-paraffins, such as though not limited to, platinum group metals on acidic supports, ZSM-zeolites, Beta-zeolites, Y-zeolites, mordenites, bimetallic catalysts, silica-supported metal catalysts, and alumina-supported metal catalysts, silicoaluminophosphates (SAPO), amorphous silica-alumina (MSA), super acid solids, and mesoporous material e.g., MCM-41 and A1MCM-41). Example of a catalyst suitable for isomerization and hydroisomerization may be platinum on SAPO-11 (Pt / SAPO-11. Further, product refining within hydrocarbon refining unit 335 might be needed, such as distillation to obtain the proper cuts that will meet the boiling point curve, freezing point, and other required specifications for SAF. Further conversions that could also be included within hydrocarbon refining units 335 to increase the blending percentage of the resulting paraffins include cyclization to produce cycloalkanes (naphthenes) and further aromatization (catalytic reforming). The immediate target product stream 337 after HDO and isomerization includes n-paraffins and isoparaffins, which can be considered synthetic paraffinic kerosene (SPK) and may be used as an adequate blendstock up to 50% afterqualifying through ASTM D4054. For increasing the blending level beyond SPK, the product stream 337 will need to also include some amount of naphthenes and aromatics; thus cyclization, dehydrocyclization, and aromatization, and / or catalytic reforming of the product stream are also contemplated as options within further hydrocarbon refining in units 335.

[0113] In another embodiment, the processes and systems illustrated in FIG. 3 can be used to co-process long-chain lipidic feedstocks with the ketones. For example, a process may include the steps and equipment required to produce the separated ketone phase 329. Rather than following the remaining process illustrated in FIG. 3, in a non-illustrated embodiment, the separated ketone phase comprising primarily C9-C17 ketones is mixed with a long-chain lipidic feedstock, such as processed vegetable oils, animal fats, algal oils, etc. The ketone and long-chain lipidic feedstock mixture are then hydrotreated or hydrodeoxygenated, which can be performed in a single step or in a single reactor / vessel, to create a paraffin stream. The paraffin stream can be fractionated to create a long-chain fraction comprising the paraffins having a carbon chain length of greater than 16 carbons (>C16) and a short-chain fraction having smaller paraffins (<C16). The long-chain fraction is then subjected to mild hydrocracking to reduce the average chain length of the paraffins. The hydrocracked paraffins are then recombined with the short-chain fraction, and the combined fraction, now consisting of primarily paraffins having a chain length of 16 or less, can then be further refined to generate a hydrocarbon product. For example, the combined fraction may be isomerized, aromatized, and / or fractionated. The final hydrocarbon product may thus be able to meet the requirements for use as a sustainable aviation fuel (SAF), either as a drop-in fuel or a blending agent. Alternatively, the ketones and the lipidic feedstocks may be hydrotreated or hydrodeoxygenated separately and then joined for further refining after the mild hydrocracking has decreased the carbon chain length of the long-chain fraction to 16 or less.

[0114] Integration of fatty acids extraction, SCFA recovery, MCFA purification, and hydrogenation / dimerization

[0115] As illustrated in FIG. 4, in some embodiments, the process may include the initial extraction and acidification of a stream 400 comprising fatty acid salts by supercritical, liquid, or gaseous CCh.to produce an extract phase 409 comprising residual supercritical, liquid, or gaseous CO2 and a mix of SCFAs and MCFAs. These initial stepsare similar to those already described for FIGS. 1, 2 and 3, and so will only be briefly explained here, but it should be understood that the previous discussion of the extraction and CO2 recovery and recycle steps also apply to the embodiments illustrated in FIG. 4.f

[0116] In the embodiments illustrated in FIG. 4, separation and purification of the medium-chain fatty acids is performed, similar to the process illustrated in FIGS. 2, 3 and 4 with streams and equipment 100-115, 121-122 and 133, 200-215, 221-222 and 233 and 300-315, 321-322 and 333, respectively corresponding to the streams and equipment 400- 415, 421-422 and 433 of FIG. 5 and streams and equipment 240-242 and 340-342 of FIGS. 2 and 3, respectively corresponding to the streams and equipment 440-442 of FIG. 4. Furthermore, streams and equipment 316-320 and 323 of FIG. 3 corresponds to the streams and equipment 416-420 and 423 of FIG. 4.

[0117] For clarity, the processes illustrated in FIGS. 1, 2, 3 and 4 may include the same streams and equipment (i.e., 100-115, 200-215, 300-315 and 400-415, respectively) needed to extract or recover MCFAs and some SCFAs from a feed solution that contains SCFA and MCFA salts, such as, but not limited to, a fermentation broth as described previously. Low-pressure make-up CO2 (121, 221, 321 and 421 in FIGS. 1, 2, 3 and 4, respectively), which may come from for example, but not limited to, cleaned-up fermentation gases are similarly pressurized, together with other recycled low-pressure CO2 streams, using a compressor (or a series of compressors) 122, 222, 322, and 432 in FIGS. 1, 2, 3 and 4, respectively. The illustrated processes of FIGS. 1-4 may also include the same pressure reduction by an energy recovery device or a throttling valve 133, 233, 333 and 433, respectively. Additionally, the depressurized streams (215, 315 and 415, in FIGS. 2, 3 and 4, respectively) may further be processed through similar equipment, e.g., a knockout separator or flash tank (240, 340, 440 in FIGS. 2, 3, and 4, respectively) to further separate CO2 from the recovered acids producing similar streams, i.e., a low-pressure CO2 stream (241, 341, 441 in FIGS. 2, 3, and 4, respectively), which may be recycled to be repressurized by a compressor (or compressors) 222, 322, 422 in FIGS. 2, 3, and 4, respectively and a CCh-lean acid stream (242, 342 and 442 in FIG. 1, 2, and 3, respectively). The CO2 separator 240, 340 and 440 in FIGS. 2, 3, and 4, respectively may also include some heat addition (not shown in figures) if necessary to enhance CO2 release. Moreover, the processes illustrated in FIGS. 3 and 4 may include the same streams and equipment (316-320 and 323 and 416-420 and 423 in FIGS. 3 and 4, respectively) toseparate water and SCFAs from the MCFAs from streams 342 and 442 of FIGS. 3 and 4, respectively, and to further purify the MCFAs before sending them downstream for further conversions; thus, the descriptions above for water / acid separation and for MCFA purification described for the processes of FIG. 3 also applies to the processes of FIG. 4.

[0118] The downstream conversion of the purified MCFA stream 423 in FIG. 3 differs from the downstream conversion of the purified MCFA stream 323 illustrated in FIG. 3. The purified MCFA stream 423 is processed using the hydrogenation / dimerization pathway rather than ketonization / HDO. As in previous embodiments, the processes illustrated in FIG. 4 include integration with extraction of fatty acids by supercritical, liquid, or gaseous CO2, recovery of the CO2, and recycling of the CO2. Unlike ketonization, the hydrogenation / dimerization reaction pathway can be tuned beyond dimerization into trimerization, which can produce diesel-range hydrocarbons. Further oligomerization, which would produce long carbon chain length hydrocarbons, represents an opportunity to produce marine fuels and / or base oils.

[0119] The processes illustrated in FIG. 4 include a separated MCFA stream 418 exiting the water / acid separation unit 416 and being fed to a purification unit, 419. The purification unit serves to separate the MCFAs from heavy impurities and / or other impurities that may be present in the MCFA stream 418. The purification unit 419 may be, but is not limited to, one or more units in series or by itself, consisting of a distillation column, a falling-film evaporator, a wiped-film or thin-film evaporator to handle high viscosities, a separation vessel, a flash vessel, a filter, a membrane filter, a guard bed with proper media for removal of nitrogen- and sulfur-containing impurities, or other equipment suitable for separating the heavy impurities or other impurities from the MCFA stream 418. The impurities are removed through waste stream 420, and may include cations such as sodium and potassium with their MCFA counter anion (e.g., sodium and potassium salts of caproate, heptanoate, caprylate), longer chain fatty acids, long chain hydrocarbons, large- molecular-weight organic compounds such as fats and oils, and, to a lesser extent, microbial debris from the fermentation, and inorganic compounds, such as other salts and minerals from the fermentation broth feed. Other nitrogen- or sulfur-containing impurities that are absorbed into certain media, which can become catalyst poisons, may also be removed in a guard bed or similar equipment. The impurity stream 420, which could contain MCFA salts, may be partly or wholly recycled back to the extraction column or contactor 401 with thefeed solution 400 to recover at least part of the MCFAs and minimize losses of the fatty acids.

[0120] Purified MCFAs exit the purification unit 419 as a purified MCFA stream 423. The purified MCFA stream 423 is fed into a heating device 445, such as, but not limited to, a heat exchanger to heat up stream 423, or an evaporator, to vaporize the purified MCFA stream 423 if it is in a liquid form as it exited purifier 419. However, if the purified MCFA stream 423 is desired as a vapor, it is preferred for better energy efficiency to avoid condensation and obtain such stream directly as a vapor from the tops of the purification unit 419, which, as mentioned, can be, for example, but not limited to, a distillation column or an evaporator. If the former, a partial condenser may be employed at the top to allow reflux, while avoiding full condensation and if the latter the vapors from the purifier evaporator 419 may be sent directly without any condensation to heating device 445, which is then only used to bring the vapors up to reaction temperature prior to feeding into hydrogenation reactor 439. As another option, it may be preferred to perform the hydrogenation reaction with the acid stream 423 fed in a liquid form, in which case condensation after purifier 419 might be needed. Liquid feed is preferred because hydrogenation is known to require higher pressures above 200 psig and thus a better device to get the stream to such pressures would be a liquid pump. Stream 423 at the proper pressure is then fed to heating device 445 to heat it up to the proper reaction temperature for hydrogenation, which is typically above 100°C or above 200°C, thus obtaining stream 444. Rather than being converted to ketones at this point of the process (as is performed in the embodiments illustrated in FIG. 3), the heated or vaporized purified MCFA stream 444 is hydrogenated in a hydrogenation reactor 439, where the MCFAs are catalytically hydrogenated (reacted with hydrogen) to form the corresponding primary alcohols 435 (e.g., but not limited to, valeric acid becomes n-pentanol, caproic acid becomes n-hexanol, heptanoic acid becomes n-heptanol, octanoic acid becomes n-octanol). The hydrogenation reactions require a supply of hydrogen 434 and are performed in the presence of one or more hydrogenation catalysts, such as, but in no way limited to iridium-, nickel-, palladium- , platinum-, rhodium-, or ruthenium-based catalysts or combinations thereof.

[0121] In an alternative embodiment not illustrated in FIG. 4, hydrogenation to primary alcohols may be accomplished indirectly by first esterifying the MCFAs with an appropriate primary alcohol, such as, but not limited, ethanol. Then, the resulting esters(e.g., ethyl pentanoate, ethyl hexanoate, ethyl heptanoate, ethyl octanoate) can be hydrogenolysed in the presence of hydrogenation catalysts, such as, but in no way limited to, iridium-, nickel-, palladium-, platinum-, rhodium-, or ruthenium-based catalysts or combinations thereof. From the hydrogenolysis of the ester, the corresponding primary alcohol and water are formed, and the original alcohol used in the esterification is recovered to be recycled to esterification, thus this alcohol is known as the “recycling alcohol.” The advantage of this alternative process is that direct hydrogenation of primary alcohols tends to require higher pressures and temperatures and be more inefficient; thus, the indirect route through the esters is many times preferred. The esterification may also be performed by first dehydrating the recycling alcohol into the corresponding olefin or alkene (e.g., dehydrating ethanol into ethylene) and then reacting the olefin with the MCFAs to produce the esters. The advantage of the latter process is that separations are more energy efficient because olefins like ethylene are gases and they readily react with primary alcohols, whereas direct esterification of the recycling alcohol with the MCFAs requires the removal of water.

[0122] Regardless of which of the pathways described are used, a primary alcohol stream 435 comprising the resulting primary alcohols and water is then sent to a phase separator 436, such as a knockout separator, where the substantially insoluble primary alcohols 438 are separated from the water 437. The substantially water-free primary alcohols 438 are then passed through a dehydration / dimerization reactor 424. In the dehydration / dimerization reactor 424, the primary alcohols are first dehydrated into olefins and then dimerized into olefins or alkenes twice their original chain-length through dimerization catalysts such as, but not limited to, Beta zeolites. As the primary alcohols provided to dimerization reactor 424 have substantially carbon lengths of C4-C9 but more abundantly C5-C8 (n-pentanol through n-octanol), the resulting alkenes or olefins may have carbon lengths ranging from C8-C18, but more abundantly C10-C16. The hydrocarbon fraction resulting from the dimerization of the primary alcohols may include n-alkenes, isoalkenes, n-paraffins, iso-paraffins, or combinations of two or more thereof. Water is produced as a byproduct of the dimerization / dehydration reactions, and so the dimerization product stream 425, which is primarily comprised of C10-C16 (or C8-C18) n-alkenes or olefins and water, is then fed to a phase separator unit 426, such as a knockout phase separator, to separate the water phase 427 from the hydrocarbon phase 428. In another proposed embodiment (not shown in FIG. 4), the combined dehydration and dimerization step 424 is separated so that a portion of the resulting olefins from the dehydration of theprimary alcohols may be recycled upstream to esterify the incoming purified MCFA stream 423. This separation and recycling are advantageous as the esters may be more efficiently hydrogenolyzed into primary alcohols compared to their MCFA counterparts.

[0123] Continuing the processes illustrated in FIG. 4, the hydrocarbon phase 428 carrying the C10-C16 or C8-C18 n-alkenes is fed to a hydrocarbon refining unit 429. In the hydrocarbon refining step 429, additional conversion of the hydrocarbon phase 428 material to n-paraffins is carried out by hydrotreatment with hydrogen, optionally followed with fractionation, separation, and purification of the hydrotreated products. For example, the n- paraffins produced from the hydrotreating of the n-alkenes may undergo fractionation to separate the different cuts, such as a SAF cut 432 (consisting primarily of C9-C16 hydrocarbons) and sustainable or renewable diesel fuel cut 431 (consisting primarily of C14-C18).

[0124] The overall theoretical reactions of the processes illustrated in FIG. 4 are as follows: ation)reaction)In the above equations, R- is CH3-(CH2)n- with n ranging from 2 to 5 and R’- is CH3- (CH2)m- with m ranging from 7 to 13. Alternatively, n may range from 1 to 6 and m may range from 5 to 15, in some embodiments.

[0125] The SAF cut 432 may then optionally further undergo isomerization in the presence or absence of hydrogen (hydroisomerization) to cause further branching and / or cyclization / dehydrogenation of the hydrocarbons to form cyclic compounds (naphthenes) and aromatics (catalytic reforming) so as to obtain the desired hydrocarbon properties, such as lower freezing point, needed in the final SAF product 432. A hydrogen stream 430 is provided for the hydrotreating and optionally may be provided to the hydrocarbon refiningto facilitate the hydroisomerization reactions. The hydrocarbon refining reactions may occur in the presence of a hydrotreating catalyst, such as though not limited to, a sulfided hydrotreating catalyst, such as nickel-molybdenum on alumina (NiMo / AhCh) or cobaltmolybdenum on alumina (CoMo / AhOs), or precious metal catalysts, such as platinum on alumina (Pt / AhCh) or Pd of alumina (Pd / AhCh). Optionally an isomerization or hydroisomerization catalyst, such as though not limited to, platinum group metals on acidic supports, ZSM-zeolites, Beta-zeolites, Y-zeolites, mordenites, bimetallic catalysts, silica- supported metal catalysts, and alumina-supported metal catalysts, silicoaluminophosphates (SAPO), amorphous silica-alumina (MSA), super acid solids, and mesoporous material (e.g., MCM-41 and A1MCM-41). The hydrocarbon refining step 429 might also include separation, typically by distillation to obtain the proper cuts that will meet the boiling point curve, freezing point and other required specifications for SAF. Further conversions that could be included to increase the blending percentage of the resulting paraffins is cyclization to produce cycloalkanes (naphthenes) and further aromatization (catalytic reforming). The immediate target SAF product stream 432 includes paraffins and, isoparaffins, which can be considered synthetic paraffinic kerosene (SPK) and may be used as an adequate blendstock up to 50% after qualifying through ASTM D4054. For increasing the blending level beyond SPK, and naphthenes and aromatics will need to also be produced and are included as options within further hydrocarbon refining in units 429. Further separation in hydrocarbon refining step 429 might also include production of small quantities of gases, biogasoline (naphtha), and heavies (diesel and larger) (not shown in FIG. 4). It should be noted that if the dimerization is tuned to go beyond dimers into trimerization, diesel product, instead of SAF, can be maximized.

[0126] In another embodiment, the processes and systems illustrated in FIG. 4 can be used to co-process long-chain lipidic feedstocks with the dimerized alcohols (alkenes). For example, a process may include the steps and equipment required to produce the separated dimerized alcohols (alkenes) in the dimerization product stream 425, which primarily comprises C10-C18 alkenes. Rather than following the remaining process illustrated in FIG. 4, in a non-illustrated embodiment, the dimerization product is mixed with a long-chain lipidic feedstock, such as processed vegetable oils, animal fats, algal oils, etc. The dimerized alcohols and long-chain lipidic feedstock mixture is then hydrotreated or hydrodeoxygenated, which can be performed in a single step or in a single reactor / vessel, to create a paraffin stream. The paraffin stream can be fractionated to create a long-chainfraction comprising the paraffins having a carbon chain length of greater than 16 (>C16) and a short-chain fraction having paraffins with a carbon chain length of 16 carbons or shorter (<C16). The long-chain fraction is then subjected to mild hydrocracking to reduce the average chain length of the paraffins. The hydrocracked paraffins are then recombined with the short-chain fraction, and the combined fraction, now consisting of primarily paraffins having a chain length of 16 or less, can then be further refined to generate a hydrocarbon product. For example, the combined fraction may be isomerized, aromatized, and / or fractionated. The final hydrocarbon product may thus be able to meet the requirements for use as a sustainable aviation fuel, either as a drop-in fuel or a blending agent. Alternatively, the dimerized alcohols and the lipidic feedstocks may be hydrotreated or hydrodeoxygenated separately and then joined for further refining after the mild hydrocracking has decreased the carbon chain length of the long-chain fraction to 16 or less.

[0127] Details of pressure partitioning of the integrated processes

[0128] As illustrated in FIG. 5, some embodiments including an integrated process for producing hydrocarbons, similar to those shown in FIG. 3 and FIG. 4, may incorporate steps and equipment to enable the operation and to improve the overall efficiency of the system. FIG. 5 shows more details than FIG. 3 and FIG. 4 such as where pressure reduction (pressure portioning) occurs for reducing pressure losses and minimizing heat losses. To reduce energy losses due to decompression and recompression of the streams, the system may be considered to include a high-pressure boundary 516 encompassing the high-pressure steps and equipment of the fatty acids extraction process. Streams and equipment within the high-pressure boundary 516 are operated at high pressure, for example about 300 psig or greater. In some variations, the pressure of streams and equipment in the high-pressure boundary 516 may be greater than about 200 psig or greater than about 100 psi. In some variations, the pressure of streams and equipment in the high-pressure boundary 516 is greater than 300 psig, or greater than about 500 psig, or greater than about 900 psig or greater than 1200 psig. In some variations, the pressure of streams and equipment inside the high-pressure boundary 516 is operated at about 800 psig, 850 psig, 900 psig, 950 psig, 1000 psig, 1050 psig, or 1100 psig, or 1200 psig, or 1300 psig, or 1400 psig, or 1500 psig, or 1600 psig. In some embodiments, the equipment inside the high-pressure boundary 516 is operated at about 800 psig to about 1000 psig. Outside of the pressure boundary 516, the equipment and streams are operated at low pressure, which may be atmospheric pressure orany pressure that is below the high-pressure portions of the system, except for hydrogenation, HDO and dehydration / dimerization, which may occur at high pressures.

[0129] In FIG. 5, a feed solution stream 500a is pressurized to generate a high- pressure feed solution stream 500b. A suitable feed solution for the feed solution stream 500a, b is preferably obtained from a fermentation process as described in more detail above in the background section and with such fermentation stream conditioned and treated as described for feed solution stream 100 for FIG. 1 above, however, any source providing a mixture of fatty acid salts as described herewith may be used. If from a fermentation process, the feed solution of the feed solution stream 500a, b comprises fatty acid salts, mainly salts of SCFAs (C2-C4) and MCFAs (C5-C9 but more specifically C5-C8, as C9 is not produced in significant quantities in fermentation), though some shorter (Cl) and longer chain fatty acid salts (CIO and greater), as well as salts of other carboxylic acids such as lactic and succinic acid, may also be present.

[0130] Under high pressure, the feed solution stream 500b is fed to an extraction or, more generically, a contactor column 501 where the fatty acid salts of the feed solution are contacted with CO2, provided by a CO2 extractant stream 502. The CO2 as fed to the extraction column 501 may be supercritical CO2, subcritical liquid CO2 or gaseous CO2. The CO2 advantageously serves dual purposes, as both an extractant and an acidifier of the fatty acid salts fed into the extract! on / contactor column 501. An extract phase exits the extract! on / contactor column 501 as an extract phase stream 550. The extract phase stream 550 contains a majority of the MCFAs (converted from the MCFA salts) and CO2. A raffinate stream 503a containing the raffinate phase from the extract! on / contactor column 501 contains SCFAs, generally having carbon lengths ranging from C2-C4, though some MCFAs, mainly C5, may also be present. The raffinate phase also carries bicarbonates formed by reaction of the CO2 with the freed cations of the converted fatty acid salts, and other polar carboxylic acid salts, such as lactate and succinate, if applicable.

[0131] The raffinate stream 503a is depressurized by passing through a throttling valve or other pressure or energy recovery device (e.g., but not limited to a pressure exchanger or a turbine), resulting in a low pressure raffinate stream 503b. The low-pressure raffinate stream 503b is provided to a recovery unit 504, which may be a stripper or heating vessel, which removes any residual or entrained CO2 from the low-pressure raffinate stream 503b. In embodiments where the fatty acids salts are sourced from a fermentation process, aportion of the resulting raffinate stream 505, now substantially free of CO2 (other than what is still bound to carbonates and bicarbonates) may be recycled to the fermentation process for further elongation of the SCFAs in the raffinate stream. Another portion of the raffinate stream 505 is diverted to a purge stream 507, which goes to waste, which is required to avoid the buildup of metals (e.g., sodium, potassium) and other cationic and anionic (e.g., chlorides) species or other unextracted species in the fermentation system.

[0132] To increase material efficiency, CO2 is recovered at various steps of the process and recycled, thereby reducing the amount of CO2 make up 530 required. For example, the recovery unit 504 allows any entrained CCh in the low-pressure raffinate stream 503b to separate from fatty acids, carbonates, bicarbonates, and any other material present in the aqueous raffinate. Optionally, heat may also be provided in unit 504, which will convert bicarbonate into carbonates, further recovering CO2. The freed CO2 exits the recovery unit 504 and as a CO2 recycle stream 508. As shown in FIG. 5, the CO2 recycle stream also incorporates CO2 recovered from various other steps of the process. The recycled CO2 stream is supplemented with a makeup CO2 stream 530, which may be sourced at least in part from the fermentation process (not shown). A combined CO2 stream 509a is compressed using a compressor 514 or series of compressors, resulting in a high- pressure combined CO2 stream 509b. The high-pressure CO2 may be cooled using an optional heat exchanger and is fed to a high-pressure CO2 storage tank 512. Optionally, if a series of compressors are used, these may undergo cooling after every compressing stage. High-pressure CO2 is pumped from the high-pressure CO2 storage tank 512 using one or more pumps or compressors 513 into the extract! on / contactor column 501 as the extractant stream 502.

[0133] Referring again to the extract! on / contactor column 501, the resulting extract phase stream 550 leaving the column is provided to a CO2 separation column 510 at high- pressure, which may optionally include standard reflux condensation and bottoms reboiling loops. A substantially pure CO2 stream 511 exits from the top of the CO2 separation column and is sent to the CO2 storage tank 512 for later use as an extractant. The bottoms of the CO2 separation column 510 form a bottoms stream 515a comprising primarily the extracted fatty acids and water, which is depressurized using a throttling valve or other pressure or energy recovery device e.g., a pressure exchanger or turbine) into a low-pressure extract stream 515b. The pressure of the depressurized stream may be about atmospheric pressureor may still be elevated compared to atmospheric pressure. In some embodiments, the pressure of the low-pressure extract stream 515b is about atmospheric (ie., 0 psig), about 5 psig, about 10 psig, about 25 psig, about 100 psig, about 200 psig, about 300 psig, about 600 psig, or about 900 psig, or about 1000 psig.

[0134] Depending on the operating conditions of the system, a substantial amount of CCh may be entrained with the low-pressure extract stream 515b. As the extract stream 515a is reduced in pressure to form low-pressure stream 515b, CO2 entrained in the extract stream will begin to separate. The extract stream 515b may be sent to an optional low- pressure CO2 knockout separator or flash tank 517, such that an additional CO2 recovery stream 518 may be recovered and sent to the CO2 recycle and re-pressurization loop previously described. A CCh-lean acid stream 519 including the extracted fatty acids and water is then sent to a series of acid separation columns 520 523. In embodiments in which the low-pressure CO2 knockout separator or flash tank 517 is not implemented, the acid stream 519 is recovered acid stream 515b, with recovered acid stream 515b being fed directly to the series of separation columns 520 523.

[0135] The series of separation columns 520 523 may include two separation columns operating in series, as illustrated in FIG. 5. However, it should be understood that the separation process may also be carried out using a single separation column or more than two separation columns. The separation columns may be distillation columns, fractionation columns, evaporators, or other separation columns as known in the art. When multiple separation columns are used, they need not be of a uniform type. The columns may include reflux and bottoms recycling to maximize separation efficiency and heat recovery. As separation columns are well-known in the art, the detailed operation of the separation columns will not be discussed further than to disclose the desired fatty acid cuts from the column product streams.

[0136] In the embodiment illustrated in FIG. 5, the acid stream 519 is sent into a first acid separation column 520. A top stream 521 primarily comprising water and lighter fatty acids (such as C2-C4 fatty acids) is collected at the top of the first acid separation column 520. The top stream 521 may be recycled to the source fermentation process (not shown) if such a process is being used to supply the initial fatty acid salts or it may become a by-product from the process, as these shorter acids may be marketed or converted into other marketable derivatives. A bottom stream 522 comprising primarily MCFAs (such asC5-C9 fatty acids) is collected at the bottom of the first acid separation column 520, which is then fed to a second acid separation column 523. In lieu of a second separation column, besides a distillation column, other separation equipment may be used, such as, but not limited to, a falling-film evaporator, a wiped-film or thin-film evaporator to handle high viscosities, separation vessels, flash tanks, filters, membrane filters, etc., so long as the target product stream, i.e. a stream comprising purified MCFAs, is obtained. From the second acid separation column, which is in fact an acid purification column, a bottom stream 524 containing heavy impurities may be collected and sent to waste or, depending on the composition of the heavy impurities, the bottom stream 524 may serve as a valuable feedstock for other processes or might be partly or wholly recycled within the process. The heavy impurities may include MCFA salts, namely cations such as sodium and potassium with their MCFA counter anion (e.g., sodium and potassium salts of caproate, heptanoate, caprylate), longer chain hydrocarbons, fermentation feedstock or debris, carbonates / bicarbonates and inorganic compounds, such as other salts and minerals from the fermentation broth feed. Other nitrogen- or sulfur-containing impurities that are absorbed into certain media, which can become catalyst poisons may also be removed in a guard bed. This heavy impurity stream 524, which could contain MCFA salts, may be partly or wholly recycled back to the extraction column or contactor 501 with the feed solution 500a to recover at least part of the MCFAs and minimize losses. A purified acid stream 525 is collected from the top of the second acid separation column 523, the stream comprising primarily purified MCFAs.

[0137] The MCFAs of the purified acid stream 525 may be fed directly as a vapor leaving the top of the separation column or evaporator 523 or as a condensed liquid to either or both of two reaction pathways, ketonization followed by hydrodeoxygenation and hydrocarbon refining, or hydrogenation followed by dehydration / dimerization / hydrotreating and further hydrocarbon refining. Both reaction pathways have been previously described in connection with embodiments shown in FIG. 3 (ketonization to hydrodeoxygenation to refining) and FIG. 4 (hydrogenation to dehydration / dimerization and hydrotreating to refining). Previous descriptions of the feed and product streams and equipment associated with these processes apply to those shown in FIG. 5. The ketonization reaction pathway produces primarily a commodity stream 537 containing C9 to C17 hydrocarbons that could contain linear n-paraffins and branched alkanes (isoparaffins) or further also cycloalkanes (naphthenes), as previously described, which may be suitable for use in blending SAF. Thisreaction pathway also produces additional CO2 that can be collected into a recycle stream 529. The hydrogenation reaction pathway results in a first commodity stream 547 containing C14-C18 hydrocarbons, which are preferably paraffins with some branching with high cetane value, which may be used in diesel fuel blends. A second commodity product stream 548 is also produced, the stream containing C10-C16 hydrocarbons such as n-paraffins, iso-paraffins and naphthenes, which may be useful in SAF blends. It should be noted that if diesel product for terrestrial or marine use is preferred, the dimerization can be tuned to go beyond dimers and allow trimerization, which would cause the carbon-chain length to be C15 - C24, which falls right on the diesel range. Further oligomerization (>C24) can also performed, which would take us into C20 - C32, which falls in the base oil category, such as those used in lubricants and other viscosity, lubricity and thermal stability applications.

[0138] Integrated process incorporating fermentation, CO2 recycle, and multiple hydrocarbon pathways

[0139] As illustrated in FIG. 6, embodiments including an integrated method for producing refined hydrocarbons suitable for use in fuel blends is provided. FIG. 6 illustrates embodiments wherein the process steps are shown at high level so as to emphasize the integrated nature of the processes and underlying systems. A feedstock 600 is provided to a fermentation step 601 to convert the feedstock into organic acid salts. The fermentation step 601 may include a fermentor containing microorganisms that are able to convert the feedstock into organic acids, including mixed fatty acids, including volatile fatty acids (VFAs), including SCFAs and MCFAs. The feedstock includes biodegradable components that may be digested or fermented by the microorganisms present in the fermentor used in the fermentation 601. The feedstock may include biodegradable organic materials, such as, but not limited to, waste or grown biomass, such as, but not limited to starch-based biomass, lignocellulosic-based biomass, proteinaceous biomass, used oils, industry waste and byproducts, hydrocarbon refining waste or byproducts. As it is desirable to develop chemical pathways that utilize renewable feedstocks, in some embodiments the feedstock is a renewable feedstock. The feedstock 600 may be a naturally sourced feedstock, as previously described and may include certain nutrients necessary for the healthy growth of the desired microorganisms in fermentation step 601.

[0140] The fermentation step 601 produces a fermentation broth 603, comprising solids suspended in liquid, and fermentation gases 602, which consist of waste gases produced by the microbes performing the fermentation process and from the neutralization of the acids in the fermentation with the bicarbonate or carbonate buffer in the recycled raffinate 622, which produces carbon dioxide (CO2). The fermentation gases 602 are primarily carbon dioxide (CO2) and hydrogen (H2) though other species such as methane, water vapor, and small amounts of ammonia, hydrogen sulfide, mercaptans, may also be present. The fermentation gases 602 exit the fermentation step 601 and are sent to a gas clean up step 619 together with gases 621 coming from upstream ketonization step 629, which produces CO2, but also some hydrogen and hydrocarbons (e.g., but not limited to, alkenes and alkanes such as methane, ethane, ethylene, propylene, propane, butene, butane). If needed, excess gases 620 from the fermentation 601 may be removed or purged from the system at this point in the process. The gas clean-up step 619 may utilize a gas / liquid separator, knock-out drums, dehydrator, or other gas / liquid separation device used in the art. Also, it may further include a sulfur species scrubber or absorbent bed or other suitable equipment to remove such sulfur species or may include other purification systems, such as, but not limited to, an activated carbon bed to remove other impurities. When hydrogen and / or methane are present in the fermentation gas 602, the gas clean-up step 619 may include a methane and / or hydrogen recovery process to purify the CO2 and to also produce a methane- and / or hydrogen-rich stream 651. This hydrogen and / or methane recovery process can be, but it is not limited to, a distillation system for cryogenic distillation, or gas- selective membranes, or pressure-swing adsorption. The resulting methane- and / or hydrogen-rich stream 651 can be then partly 653 or fully be sent to be combusted to produce energy for the process or to be used as a hydrogen source in the HDO 632, hydrogenation 638, hydrotreating steps 642 or other hydrocarbon refining steps 636 or 645 downstream (e.g., but not limited to, hydroisomerization) by separating the hydrogen or sending the stream to steam reforming to further convert the methane into hydrogen. If, on the other hand, only small amounts of hydrogen and / or methane are present in the fermentation gas 602, a catalytic oxidation (CatOX) chamber or flare may be employed where oxygen is provided to convert such species into water and CO2.

[0141] Although pure H2 may be obtained with a purification step as described above, typical mixed-culture fermentation systems that are methane inhibited will produce mostly H2 together with the CO2. Upon purifying the CO2 in gas clean up step 619, a fairlypure H2 stream with small quantities of CO2 will be generated 651, which, as mentioned, can be sent to HDO 632, hydrogenation 638, hydrotreating 642_or other hydrocarbon refining steps 636 or 645 downstream (e.g., but not limited to, hydroisomerization) without much more clean up. The quantity of H2 required for these unit operations, however, is much higher than what the fermentation could produce. Nonetheless, this H2 stream 651 can be sent full or partly 652 to ketonization 629, which, as mentioned above, can benefit from a sweep or carrier gas containing H2, which has been shown to improve catalytic activity and can increase catalyst long-term stability by minimizing deactivation through inhibition of coke formation. This H2 stream 652 may be optionally mixed with some CO2 655 from the clean-up step 619 and fed 656 to ketonization 629 as sweep or carrier gas together with the MCFA feed 628. The resulting ketone products 631 and water 630 are then condensed and separated from the gases 621, which will be the CO2 and H2 from the incoming sweep or carrier gas 656 added to the CO2 and small quantity of H2 and hydrocarbons generated from the ketonization reaction 629. The gas stream 621 from ketonization 629, which may now also contain hydrocarbons in addition to CO2 and H2, may be partly recycled internally within ketonization 629 after purging the excess (not shown in FIG. 6) and / or may be sent back to gas clean-up 619 together with fermentation gases to be purified and to separate H2, hydrocarbons and CO2.

[0142] Finally, the CO2 stream 657 exiting the gas clean-up system 619 may or may not be at high pressure depending on the separation systems used in clean-up system 619. The ketonization sweep or carrier gas 656 does not necessarily require to be at high pressure to be fed into ketonization 629. But other uses of CO2, such as for acid extraction and recovery 617 do require clean and high-pressure CO2; therefore, stream 654 may be further dried and pressurized (not shown in FIG. 6) to produce a pure, dry and pressurized CO2 stream 618. The resulting CO2 stream 618 is then used as an extractant, described further below. Optionally, excess clean and pressurized CO2 649 is ready to be exported for carbon capture, utilization and / or storage (sequestration) (CCUS), which are processes, which consist of capturing CO2 and finding uses for it (e.g., producing other products, such as, but not limited to, methanol) or storing or sequestering it underground in injection wells. CCUS is practiced for reducing the carbon footprint (i.e., decreasing greenhouse gas emissions) in the life-cycle assessment of the final biofuels and bioproducts in biomanufacturing processes. CCUS can drastically reduce greenhouse gas emissions of processes that produce excess CO2, however, CCUS is known to require extra capital and operating expenses forcleaning up and pressurizing such excess CO2. Advantageously, the proposed process in FIG. 6, already requires cleaning and pressurizing CO2 for the acid extraction and recovery process 617; thus, implementation of CCUS would not constitute a high capital and operational expense burden compared to other processes.

[0143] The fermentation broth 603 produced by the fermentation step 601 is sent to a solids removal or clarification step 604 for treatment. The solids removal step 604 may use one or more settling tanks, filtration systems, centrifuges, membrane filtration, such as microfiltration, ultrafiltration, nanofiltration and other solids removal processes generally known in the art, or combinations of two or more thereof. Solids 605, comprising of, for example, but not limited to, undigested feedstock or digestate, microbial biomass, precipitated phosphate (e.g., struvite) are separated during the solids removal step 604. To minimize losses of the fermentation products with these solids, a solid washing step, such as, but not limited to, diafiltration, may be implemented, with the resulting wash liquid being either recycled to fermentation or sent downstream with the clarified fermentation broth 606 (not shown in FIG. 6). Although not shown in FIG. 6, prior to solids removal, aeration to increase pH, or the addition of alkali to increase pH and / or heating may be applied to the raw broth 603 to cause phosphate precipitation (e.g., struvite or calcium phosphate depending on magnesium or calcium presence), which is removed by the solids removal step 604. These aeration, alkali addition and / or heating actions would also remove some CO2 and ammonia. The clarified fermentation broth 606 is sent to a broth concentration step 607, which may use a heater, an evaporator (such as, though not limited to, a mechanical vapor recompression or multiple-effect evaporator) or reverse osmosis (RO) filtration system, or other equipment that removes a portion of the water in the clarified fermentation broth, resulting in a concentrated broth 614 having a higher concentration of fatty acid salts. The broth concentration step 607 also results in a water stream 608 of the water removed from the broth, which may also include a significant amount of dissolved ammonia. The water 608 from the broth concentration step 607 and the concentrated broth 614 may both optionally be sent to ammonia removal steps 609 615, respectively. Ammonia removal may occur by various processes, such as, but not limited to, steam stripping, air stripping, aeration, gas-permeable membranes, RO filtration / concentration. Recovered ammonia 610a and 610b, which is typically recovered from a scrubber or from a gas-permeable membrane may be captured by sulfuric acid, resulting in ammonia sulfate, which may be used as a valuable feedstock for other processes(e.g., fertilizer). RO filtration / concentration of the water 608 will result in a concentrated ammonium carbonate solution. The removal of ammonia and any dissolved carbon dioxide from the fermentation broth 614 may cause electrolyte changes in the broth and may cause other species, such as phosphates (e.g., struvite or calcium phosphate depending on magnesium or calcium presence), to precipitate. Such precipitate must be filtered and removed with solids removal equipment such as, but not limited to, filters or membrane filtration (not shown in FIG. 6) or alternatively, as mentioned above, ammonia removal can also occur prior to solids removal 604 to use the same solid removal equipment to remove this precipitate. The ammonia-free water 611 removed from the broth during concentration step 607 may be sent back to the fermentation 601 (stream 612), though if the incoming feedstock 600 has a high-moisture content, excess water 613 will need to be bled off to maintain the proper amount of liquid in the fermentation step 601. If, on the other hand, feedstock 600 has a low-moisture content, external water might need to be added to fermentation.

[0144] The clarified broth 606, the concentrated broth 614 and the ammonia-lean concentrated broth 616 are similar in composition in accord to how they have been conditioned (e.g., clarified, concentrated, ammonia removed) to the feed solutions 100 through 500a / 500b, in FIGS. 1 through 5, respectively when derived from fermentation. The concentrated broth 614 (or 616 if the optional ammonia removal step is performed) is then fed to the acid extraction and recovery step 617. The acid extraction and recovery step 617 includes an extraction column or contactor and it also includes other equipment and processes for recovery of CO2 and recycle to the extraction column or contact, as described in previous embodiments. CO2 from the cleaned CO2 stream 618 coming from gas clean-up 619 and prior to that step from fermentation 601 and / or CO2 recovered 621 from ketonization 629 is used as the extractant in the acid extraction and recovery step 617 where, as previously described, the CO2 both acidifies the fatty acid salts and extracts the resulting fatty acids. The acid extraction and recovery step 617 generates a raffinate stream 622 comprising the buffer (carbonates and bicarbonates), which controls pH and the unextracted fatty acids, and which can be recycled back to the fermentor of the fermentation step 601. As the unextracted fatty acids include greater amounts of SCFAs, the recycle to fermentation provides an opportunity for the unextracted fatty acids to be elongated into MCFAs by microorganisms through the rBOX pathway. A portion of the raffinate 622 from the acid extraction and recovery step 617 may be purged 648 as needed to reduce systembuildup of metal cations, other anions and other unextracted species. Extracted and recovered fatty acids 623 from the acid extraction and recovery step 617 will primarily include MCFAs (C5-C9 but more specifically C5-C8, as C9 is not produced in significant quantities in fermentation), although small quantities of water, C2-C4 acids (SCFAs) and other impurities will also be present. An optional purification step 624 may be used to remove lighter species like water and SCFAs as well as other impurities from the resulting extracted and recovered fatty acids 623. The purification step 624 may first capture lighter species 625, including water, residual CO2 and SCFAs, primarily C2-C4 acids, which can be recovered as products 626 or may be recycled back to the fermentor of the fermentation step 601 for chain elongation as previously described. Such lighter species may be recovered using for example, but not limited to, a distillation column or an evaporator. Then, also in the optional purification step 624, heavy impurities 627, such as, but not limited to, MCFA salts (e.g., sodium or potassium caproate, heptanoate, caprylate), longer chain acids, long chain hydrocarbons, large-molecular-weight organic compounds such as fats and oils, and, although to a lesser extent, fermentation solids, and inorganic compounds, such as other salts and minerals and others may be removed by subjecting the extracted MCFAs to, for example, distillation, evaporation (e.g., but not limited to, falling film evaporator, wiped- or thin-film evaporator), centrifugation, filtration, or combinations thereof and other purification processes known in the art. The vaporized MCFAs during distillation or evaporation in purification step 624 may be directly fed to ketonization 629 or hydrogenation 638 without having to condense them first. The heavy impurities 627, which as mentioned could contain some MCFA salts, may be recycled partly or wholly to acid extraction and recovery 617 or to the fermentation 601 to minimize MCFA losses.

[0145] The extracted and recovered fatty acids 623 (or the purified fatty acids 628, if the optional purification step or steps are employed) can be processed into fuel grade hydrocarbons through either a ketonization pathway or a hydrogenation pathway, as has previously been described in reference to, for example, embodiments illustrated in FIGS. 4 and 5. Briefly, in the ketonization pathway 629, MCFAs are converted to ketones 631, in addition to CO2 and small quantities of H2 and hydrocarbons 621 and water 630. The CO2 and H2 stream 621, which is partly fed sweep or carrier gas, may be recycled within the ketonization process 629 as sweep or carrier gas and / or it may be sent together with the fermentation gases into the gas clean-up system 619 to be purified and to separate the CO2 from the H2 as described in more detailed above. As mentioned, some of the recovered CO2and H2 can be recycled back to the ketonization 629 as sweep or carrier gas 656. From the gas-clean up system 619, the recovered pure CO2 from both fermentation 601 and ketonization 629 is then pressurized and sent to other purposes such as acid extraction and recovery 617 or CCUS 649. The ketones 631 are then sent to hydrodeoxygenation (HDO) 632 where hydrogen 633 is fed to the ketonization reactor and the oxygen is removed from the ketones to produce n-paraffins 635 and water 634. The n-paraffins 635 are then subjected to further hydrocarbon refining 636 to produce fuel grade, refined hydrocarbons 637. Alternatively, in the hydrogenation pathway, the MCFAs are sent to a hydrogenation unit 638 with hydrogen 639 to produce primary alcohols 641 and water 640. The resulting primary alcohols 641 are further processed in a dehydration, dimerization and hydrotreating reaction step 642 (Note: these steps can occur in one reactor or separately), where hydrogen 647 is provided for hydrotreating and which also produces water 643 as a by-product. The dehydration, dimerization and hydrotreating of the primary alcohols 641 results in n- paraffins and some iso-paraffins 644 which, as previously described, can be subjected to a hydrocarbon refining step 645 to produce refined hydrocarbons 646 having chemical structures useful in fuel and fuel blends. These processes for converting MCFAs into useful hydrocarbon streams have been explained in greater detail previously in this disclosure, and the previous descriptions apply to the embodiment illustrated in FIG. 6 as well.

[0146] Integrated process incorporating fermentation, extraction with hollo -fiber membranes, CO2 recovery and hydrocarbon conversion.

[0147] FIG. 7 illustrates a process for the production of fuel-grade hydrocarbons utilizing hollow fiber membrane extractors. In FIG. 7, a feedstock 700 is provided to a fermentation unit 701 containing a microorganism culture or cultures that digests the feedstock to produce fatty acid salts. As previously described in reference to other embodiments, the feedstock 700 may be biodegradable and may optionally be naturally sourced. The general description of the feedstock and potential sources for the feedstock previously provided also apply to the present embodiment. The fermentation process results in a raw fermentation broth 705 that includes an initial concentration of mixed fatty acid salts dissolved in solution with water. The raw broth may also include entrained or suspended solids, such as undigested feedstock particles, microorganisms, and solid waste products produced by the fermentation process.

[0148] The raw fermentation broth carrying the dissolved fatty acid salts is sent to clarification 706 to remove solid materials in the raw broth. The clarification unit (or units)706 may include one or more pieces of equipment suitable for separating the liquid broth containing the dissolved fatty acid salts from the solids in the broth. As non-limiting examples, the clarification unit 706 may include one or more of a filter, a membrane, a centrifuge, a settling tank, a clarifier, or other device for the separation of the solids from the liquid broth medium. To increase efficiency of the processes, it may be desirable to further recover any liquid from the high-solid stream or retentate 708 produced by the clarification unit 706. The retentate 708 may be sent to a solids separation unit 709 for further processing and recovery of the liquid phase. The solids separation unit 709 may include further filters, membranes, settling tanks, spray dryers, rotary dryers, centrifuges, presses, or other devices capable of extracting the liquid phase from the retentate. Preferably this solid separation unit 709 is able to concentrate the solids further than clarification unit 706, or, optionally, fresh water can be added 756 to wash the solids or to effect diafiltration. The remaining solids, or digestate 710, can be sent to waste or used in other processes (e.g., but not limited to composting or methanogenic anaerobic digestion) as desired. The recovered liquid phase 711 from the retentate 708, which primarily comprises water and fatty acid salts, and that is potentially more diluted, can be recycled back to the fermentation unit 701, or, alternatively, it can also be joined with the permeate or filtrate707 exiting the clarification unit 706 (not shown).

[0149] The permeate or filtrate from the clarification unit 706 is a clarified fermentation broth 707 containing fatty acid salts and water. Depending on the fermentation conditions, ammonia may also be present dissolved in the clarified fermentation broth 707 and may be removed in an optional ammonia removal step. The removal of dissolved ammonia from the broth avoid ammonia reacting with acids and other compounds, thus forming nitrogen impurities and can reduce corrosion of valuable downstream equipment, which has additional cost due to the high-pressure operating requirements. In addition, ammonia may be used as a nitrogen source for other processes, such as agriculture fertilizer, thus it has other uses. In embodiments including the ammonia removal step, the clarified fermentation broth 707 is passed through an ammonia stripper 712, producing a dilute ammonia product 713, which can be sent to an ammonia recovery system, which can be, but is not limited to, a scrubber or ion exchange system (not shown). The substantially ammonia-free clarified fermentation broth 714 is produced and sent downstream. Theammonia stripper 712 may be any suitable equipment for removing dissolved ammonia from a liquid, including though not limited to cross-current and counter-current ammonia strippers using air or steam as the stripping agents.

[0150] The clarified broth 707 (or 714 if ammonia stripping is performed) is provided to a high-pressure pump 715 to produce a pressurized broth 760, pressurized at 300 psig or greater. In some embodiments, the broth is pressurized at a pressure ranging from 300 psig to 1500 psig, which includes pressurizing at 300 psig, 400 psig, 500 psig, 600 psig, 700 psig, 800 psig, 900 psig, 1000 psig, 1100 psig, 1200 psig, 1300 psig, or 1400 psig, or about 1500 psig. In some embodiments, the broth is pressurized to 1500 psig or greater and less than 2000 psig. The pressurized broth 760 may advantageously be subjected to an optional step to concentrate the broth in a dewatering unit 716. The dewatering unit 716 may be, for example, though not limited to, a reverse osmosis (RO) concentrator and / or an evaporator such as a mechanical vapor recompression or multiple-effect evaporator. The broth may be heated as part of the dewatering process. The dewatering unit 716 may also facilitate removal of excess dissolved carbon dioxide and ammonia from the broth, thus if an evaporator is used, more likely the ammonia removal step 712 will not be required, as opposed to when a RO unit is employed, which does not remove ammonia efficiently. Recovered water 717 may be recycled to the fermentation step 701, with any excess water 718 being purged from the system. Additional pressure step down equipment may be required to depressurize the recovered water 717 as needed, such as when using an evaporator as the dewatering unit 716, unlike when an RO unit is used, in which case the permeate exits such unit at a low pressure. Further ammonia removal from 717 (not shown) might also be required before recycling it to fermentation.

[0151] The pressurized broth 760 (or 720 if the optional dewatering step is performed) may optionally be sent to a polishing ammonia removal system 721 to further remove ammonia from the broth as ammonium salts 723. The ammonia removal system 721 may be performed, as a non-limiting example, in a hollow-fiber membrane contactor, which is permeable to ammonia, as shown in FIG. 7. Acid 722 is provided to the hollow-fiber membrane contactor to either the shell or the tube side, while the pressurized broth 760 (or 720) is fed to the other side of the membrane thus allowing ammonia to transfer from the broth to the acid stream thus ending up with the ammonium salts 723 in the acid side, which exits the ammonia removal system 723. The acid 722 provided to the membrane may be anysuitable acid for causing the formation of the ammonium salts, including but not limited, to hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and others. Combinations of acids may also be used. The substantially ammonia-free pressurized broth 724 can then be provided to the extraction step.

[0152] The broth 760, the concentrated broth 720 and the ammonia-lean concentrated broth 724 are similar in composition to the clarified broth 606, the concentrated broth 614 and ammonia-lean concentrated broth 616, respectively in FIG. 6. In addition, these streams are similar in composition in accord to how they have been conditioned (e.g., clarified, concentrated, ammonia removed) to the feed solutions 100 through 500a / 500b, in FIGS. 2 through 5, respectively when derived from fermentation. For the extraction step, the pressurized broth 760 (or 720 if the optional dewatering step is performed or 724 if the optional ammonia removal step is used) is provided to a hollowfiber membrane extractor 725, which is permeable to acids and to CO2. A CO2 phase 726 that includes gaseous, liquid or supercritical CO2 is also fed to the hollow fiber extractor 725 at the shell or tube side of the hollow-fiber membrane extractor 725, while the pressurized broth 760 (or 720 or 724) is fed to the other side of the membrane. Within the extractor, the CO2 phase 726 provides CO2, which transfers to the pressurized aqueous broth 760 (or 720 or 724) side, which form carbonic acid and serves to acidify the fatty acid salts. The now free fatty acids in the pressurized aqueous broth side transfer to the CO2 side and thus are extracted from the aqueous broth. The CO2 phase 735 now carrying the extracted fatty acids exits the hollow-fiber membrane extractor from the CO2 side while the aqueous phase 727 carrying the unextracted fatty acids, fatty acid salts, and bicarbonates exit the hollow-fiber membrane extractor from the other side. The unextracted fatty acids and fatty acid salts in the aqueous phase primarily comprise of SCFAs (i.e., C2-C4 fatty acids) and salts thereof, though smaller amounts of MCFAs and salts thereof may also be present in the aqueous phase. To reduce energy requirements associated with pressurizing the fermentation broth 707 (or 714), the aqueous phase 727 may be passed through a pressure exchanger or turbine 728 in communication 729 with the clarified high-pressure pump 715, which pressurizes the broth 707 (or 714), thereby at least partially recovering the energy used in high pressure pump 715. In this way, energy required to pressurize the clarified broth 707 714 can be substantially reduced.

[0153] A gas-liquid separation unit 730, which may be, but is not limited to, a stripper, may optionally be used to recover any entrained CO2 in the aqueous phase 727 leaving the hollow-fiber membrane extractor 725 after being depressurized 757 by passing through pressure exchanger or turbine 728. Heat may be optionally provided, which will convert bicarbonate into carbonate to further recover more CO2. The recovered free CO2 731 exits the gas-liquid separation unit 730 and is sent to the CO2 compressor 740 together with other CO2 streams as described below, to be repressurized and re-used in the hollowfiber membrane extraction process 725. The CCh-lean aqueous broth 732 exiting the gasliquid separation unit 730 (or the depressurized aqueous phase 757 if the CO2 is not separated) containing unextracted fatty acids and carb onate / bi carb onate may be recycled back to the fermentation step 701 for chain-elongation of the SCFAs and as buffering agent for pH control. To prevent buildup of cations, other metals, anions and other unextracted species in the fermentation, a portion of the recycled aqueous phase 732 (or 757) may be purged 734 from the system.

[0154] An extracted CO2 phase 735 exiting the hollow fiber membrane extractor 725 contains primarily CO2 and MCFAs (C5-C9 acids but more specifically C5-C8, as C9 is not produced in significant quantities in fermentation), though small quantities of C2, C3 and C4 acids and water may be observed. The extracted phase 735 is sent to a CO2 separation unit 736 to recover the CO2 for reuse as an extractant. The CO2 separation unit may include, though is not limited to, a flash tank or a distillation column with reflux. The CO2 separation unit 736 separates the CO2 extractant from the extracted acids at high pressure (>300 psi).

[0155] The extracted fatty acids 743 may be passed through a pressure-reducing device 761, such as a throttling valve or other energy recovery device. The pressure of the fatty acids may be reduced to less than 300 psig, less than 200 psig, less than 100 psig, less than 50 psig, or to about atmospheric pressure. The extracted fatty acids 743 may be subjected to optional separation and purification steps. In the separation step, the extracted fatty acids 743 are fed into a separation or distillation column 744, which may be operated at atmospheric pressure or at a vacuum. The relatively light fraction, comprising SCFAs (i.e., C2-C4 acids) and water 745, is recovered from the top of the column, while the heavier fraction comprising primarily MCFAs 746 (i.e., C5-C9 acids, but more specifically C5-C8, as C9 is not produced in significant quantities in fermentation) is recovered fromthe bottom of the column. The recovered light fraction containing SCFAs and water may be optionally recycled to fermentation 701 for chain-elongation of the SCFAs (not shown in FIG. 7) or they may be exported and marketed as separate products.

[0156] The extracted fatty acids 743 (or 746 if the optional separation step 744 is employed) can also be subjected to an optional purification step. In the purification step, the extracted fatty acids 743 or 746 are fed to a separation, distillation column or evaporator operated at atmospheric pressure or at a vacuum. Heavy impurities 748, such as MCFA salts, longer chain fatty acids (i.e., >C10), heavy oils, or other salts and high-molecular weight impurities are optionally removed from the MCFAs 749 (C5-C9).

[0157] The extracted fatty acids 743 (or 746 or 749 if optional separation / purification steps are taken) can be converted into fuel grade hydrocarbons 754 through processes previously described (i.e., ketonization, HDO, and refining, or hydrogenation, dehydration / dimerization / hydrotreating, and refining, or a combination of both pathways). Previous descriptions of these pathways also apply to the embodiment illustrated in FIG. 7. Additional hydrogen 751 is required in either the HDO or hydrogenation and hydrotreating or refining steps (e.g., during hydroisomerization). Products of the hydrocarbon refining also include water 753, gases 755, which may be used as energy source or to make hydrogen within the process or simply flared and heavies 752, comprising tars and hydrocarbons that have carbon chains that are too long for use in a fuel blend. The resulting hydrocarbons 754 are suitable for use in diesel and / or SAF blends.

[0158] The process illustrated in FIG. 7 includes integration of CO2 capture and recycle pathways so as to reduce of even eliminate the amount of make-up CO2 required by the process. At least a portion of the CO2 for the extraction process is provided by the fermentation of the feedstock 700 in the fermentation process 701. Fermentation gases 702 produced as a byproduct of the fermentation process from microorganism metabolism may include CO2, H2, water vapor, and methane, with other minor species, such as hydrogen sulfide and mercaptans, also possible. In addition, from the neutralization of the acids in the fermentation with the carbonates and bicarbonates used as buffering agents to control pH, CO2 is also released and recovered as part of the fermentation gases 702. The fermentation gases 702 may optionally be sent to a gas clean up unit 704, which may be optionally comprised of, but not limited to, a scrubber, a nitrogen- or sulfur-containing species removal bed, a compressor followed by distillation to separate other components such ashydrogen and methane or alternatively a gas-permeable membrane may be used to separate methane and hydrogen and purify the CO2. Additionally, if the methane and hydrogen are not to be recovered to be used as energy sources or for hydrogen production, a catalytic converter to convert these flammable species to water and CO2, respectively, a knockout drum and a gas dryer to remove water, etc. may also be implemented. The gas clean-up process 704 should produce a substantially pure CO2 stream 741. Excess fermentation gases may be purged 703 either before entering the optional gas clean up unit 704 as shown or as a product stream of the gas clean up unit 742. If instead of having excess CO2, additional CO2 is required, make-up CO2 may be added to the system although such is unlikely given that fermentation will always produce excess CO2, especially if some of the CO2 is obtained from ketonization, if such is the pathway chosen for conversion of the recovered MCFAs (743 746 749)

[0159] The clean CO2 741 stream from the fermentation, the recycled CO2 731, any CO2 from downstream ketonization if applicable and any required makeup CO2 may be pressurized via one or more compressors 740 to generate a pressurized CO2 stream 739. A side stream 758 of this pressurized CO2, if in excess, may optionally be sent directly to carbon captured for utilization and / or storage (sequestration) (CCUS), which are known processes employed to improve the carbon emissions footprint (ie., decrease greenhouse gas emissions) in the life-cycle assessment of the final biofuel product. Now, once at or above the higher operating pressure of the upstream process, the pressurized CO2 stream may be merged with other high pressure CO2 sources, such as the high-pressure CO2 recycle streams 737 recovered from the CO2 separation unit 736. The merged CO2 streams may be re-pressurized using a compressor, a blower or pump 738 back up to the required high pressure to form the supercritical, liquid or gaseous CO2 extractant 726 for use in the extractor 725.

[0160] In all these embodiments, the use of CO2 (gaseous, liquid or supercritical) makes separation simple because of the large differences in boiling point between the extracted acids and CO2. Specifically, gaseous CO2 separation is more efficient because the extracted MCFAs form a separate phase with the CO2 and the need for a larger amount of cooling to cause the CO2 to condense may be avoided. Although the equipment layout in the previous embodiments for separating and recovering CO2 do apply to gaseous CO2 as well, the above-mentioned advantages of gaseous CO2 over supercritical and liquid CO2 providefurther opportunities for improvements towards making the process more efficient. Innovative details of these improvements on how to handle gaseous CO2 and further insights are provided.

[0161] Fatty acids extraction with gaseous CO2 and improvements on recovery and recycle of such gaseous CO2

[0162] FIGS. 8 and 9 show embodiments where a mix of liquid and gaseous CO2 or only gaseous CO2 is employed to extract or recover fatty acids and an efficient recovery and recycle of the CO2 as a liquid or gas is implemented. Firstly in the embodiments illustrated in FIG. 8, the feed solution 800, which can be sourced from fermentation and has been further conditioned (e.g., clarified, concentrated, ammonia removed), is similar in composition to the feed solutions 100 through 500a / 500b in previous embodiments discussed in reference to FIGS. 2 through 5, and other streams (e.g., 616 and 724) in embodiments in FIGS. 6 and 7. Therefore, the description and conditioning of those feed solutions and streams as previously presented with reference to FIGS. 2 through 7, also apply to the feed solution 800 in FIG. 8 and so will not be repeated in detail here. With reference to FIG. 8, in some embodiments, an aqueous feed solution 800 containing fatty acid salts (SCFAs and MCFAs) is sent to extraction or contactor column 801, which can be, but is not limited to, a packed column with structured packing or random packing, a mechanically agitated column separated in stages, or a bubble column as described below in FIGS. 10 through 13, or a foam fractionator system as described below for FIGS. 14 and 16. The feed solution 800 fed to extraction or contactor column 801 is contacted with gaseous or liquid CO2 at the desired pressure to effect acidification, which can be 200 psig, 300 psig, 400 psig, 500 psig, 600 psig, 700 psig, 800 psig, 900 psig, 950 psig, 1000 psig, or 1100 psig, or 1200 psig, or 1300 psig, or 1400 psig, or 1500 psig, or 1600 psig, or greater and at a pressure less than 2000 psig. The extraction or contactor column, in some embodiments, is operated at a pressure of about 800 psig to about 1000 psig. The column is preferably operated at a temperature sufficient for at least a portion of the CO2 to be in a gaseous or vapor state, although the column may also be operated in such conditions that the CO2 is in a fully gaseous or fully liquid state. The CO2 extracts, or perhaps more accurately, scavenges the aqueous feed solution 800 for fatty acids, being substantially selective towards MCFAs, and captures them and thus recovers them, while substantially leaving behind in the aqueous solution or raffinate the SCFA salts (i.e., C2 - C4 fatty acids saltsalong with some small quantities of MCFAs), and also other polar carboxylate salts that may be present, such as formate, lactate, or succinate. The raffinate 802 leaves the bottom of the extraction or contactor column 801 with the unextracted fatty acid salts and sodium and potassium bicarbonate or carbonate. The raffinate stream 802 is depressurized by going through a pressure-reducing device 826, which can be a throttling valve or an energy recovery device such as a pressure-exchanger or a turbine. If the pressure-reducing device 826 is an energy recovery device, for energy savings, it may be coupled with other mechanical devices, such as compressors or the pressurization pump (not shown in FIG. 8) used to feed the feed solution 800 into the extraction column or contactor 801. Raffinate stream 802 may be recycled to fermentation to allow the unextracted SCFA salts to chain elongate into MCFAs and to provide the bicarbonates / carbonates to the fermentation to serve as the buffering agent to control the fermentation pH.

[0163] The CO2 and the recovered fatty acids (mostly MCFAs) 803 leave through the top of the extraction or contactor column 801 and may be passed through an optional overhead heater 804, which will ensure that the CO2 will be fully in gaseous state, if it was not already. Then, the heated CCh+recovered acids stream 803 is sent to a high-pressure knockout separator or flash tank 805 to allow the bulk of the gaseous CO2 806 to separate from the acids 811. The gaseous CO2 806 is then recompressed using a pressure boosting device 807, such as, but not limited to, a compressor, , a blower, or a booster fan 807 to the raise the CO2 pressure back to a sufficient pressure for reinjection into the extraction or contactor column 801. The pressure boosting device may alternatively be an eductor or a venturi configured to use a circulation loop of at least some of the aqueous liquid from the bottom of the contactor bubble column 801 as the motive fluid to entrain the CO2. The higher-pressure gaseous CO2 808 leaving the pressure boosting device, illustrated as a booster fan 807 in FIG. 8, is then passed through an optional cooler 809, which illustratively in FIG. 8 is an air cooler, but it is not limited to such; thus other types of cooling equipment or methods known in the art, such as a water cooler or a chiller, may also be used. The higher-pressure and cooled liquid or gaseous CO2 stream 810 leaving the cooler 809 can then be recycled to extraction or contactor column 801.

[0164] The acid stream 811 leaving the knockout separator or flash tank 805may still contain an appreciable amount of CO2 dissolved in the acids; therefore, it is sent to a high-pressure distillation system 812 where heat is applied to further remove the CO2 fromthe acids. The separated CO2 813 leaves through the tops of distillation column 812. The CO2 813 is condensed using condenser 814 and converted to a liquid 815, which can then be recycled to the extraction or contactor column 801. Any makeup CO2 819 required to replenish the CO2 that leaves with the raffinate 802 as bicarbonates and carbonates and other losses may be delivered to the system using makeup CO2 pump 820 and joined with recovered liquid CO2 815 to form one stream 821, which is then pumped into the extraction or contactor column 801 at sufficient pressure using booster pump 822. In the column, the CO2 may partly remain as a liquid or become fully gaseous. The amount of makeup CO2 819 to be delivered to the system may be set by pressure control (not shown in FIG. 8) of the extraction column or contactor 801. The separated fatty acid stream 818 from the distillation column 812 leaves through the bottoms where it recirculates 816 through reboiler 817, which provides the energy for driving the separation process. As mentioned, these fatty acids in stream 818 are mostly MCFAs, i.e., fatty acids >C5, which would be mostly C5-C9 fatty acids but more precisely C5-C8 fatty acids as C9 is not produced in the fermentation in significant quantity. Stream 818 is then passed through a pressure-reducing device 821, which can be a throttling valve or an energy recovery device such as a pressureexchanger or turbine, which would allow for some of the energy to be recovered for use elsewhere in the process, such as, but not limited to, powering the CO2 makeup pump 820. Finally, the depressurized acid stream 822 is sent to a knockout separator or flash tank 823, which will further allow the release of any CO2 824 still present from the MCFAs 825. Some heating may be provided for the knockout separator or flash tank 823 to improve the separation. CO2 stream 824 may be recycled to a compressor to become part of the makeup CO2 819 together with other sources of CO2, such as cleaned-up fermentation gas. The MCFA stream 825 may then be sent downstream for conversion into other products, such as ketones or primary alcohols, and drop-in hydrocarbon fuels.

[0165] FIG. 9 shows another process according to an embodiment that takes advantage of the efficiencies of being able to use gaseous CO2 for extraction. In this case, CO2 is recovered and recycled always as a gas, which is advantageous due to the fact that phase changes from liquid to gas or vice versa require the exchange of a large amounts of energy. Thus allowing the CO2 to remain as a gas throughout the process improves the energy usage and efficiency of the process. A feed solution 900 may be sourced from fermentation and is similar in composition and has been conditioned in similar ways as presented for feed solutions 100 through 500a / 500b in the embodiments illustrated in FIGS.1 through 5, respectively, and other streams (e.g., 616 and 724) in embodiments illustrated in FIGS. 6 and 7. Therefore, the description of the composition and conditioning of those feed solutions and streams as previously presented for FIGS. 2 through 7 also apply to the feed solution 900 in FIG. 9.

[0166] The feed solution 900 is an aqueous solution containing fatty acid salts (SCFAs and MCFAs). The feed solution 900 is sent to extraction or contactor column 901, which can be, but is not limited to, a packed column with structured packing or random packing, a mechanically agitated column separated in stages, or a bubble column as described below in reference to FIGS. 11 through 13, or a foam fractionator system as described below for FIGS. 14 and 15. In the extraction or contactor column 901, the feed solution 900 is contacted with gaseous CO2 at sufficient pressure to effect acidification of the fatty acid salts, which can be 200 psig, 300 psig, 400 psig, 500 psig, 600 psig, 700 psig, 800 psig, 900 psig, 950 psig, 1000 psig, 1100 psig, 1200 psig, 1300 psig, 1400 psig, 1500 psig, 1600 psig, or greater and, in some embodiments, less than 2000 psig. In some embodiments, the extraction or contactor column 901 is operated at a pressure of about 800 psig to about 1000 psig. The extraction or contactor column 901 is operated at sufficient temperature to have the CO2 in a gaseous state. The gaseous CO2 extracts or scavenges the aqueous solution for fatty acids, selectively the MCFAs present in the aqueous solution, and captures them and thus recovers them, while leaving behind in the aqueous solution or raffinate SCFA salts (C2 - C4 fatty acids salts), but also other polar carboxylate salts that may be present, such as formate, lactate and succinate. The raffinate 902 leaves the bottom of the extraction or contactor column 901 with the unextracted fatty acid (SCFA and some MCFA) salts and, mostly, sodium and potassium bicarbonate or carbonate. The raffinate stream 902 is depressurized by going through a pressure-reducing device 926, which can be a throttling valve or an energy recovery device such as a pressure-exchanger or a turbine. When an energy recovery device is used as the pressure reducing device 926, for energy savings it may be coupled with other mechanical devices, such as compressors or the pressurization pump (not shown in FIG. 9) used to feed the feed solution 900 into the extraction column or contactor 901 to bring this stream 900 up to required pressure for fatty acid extraction and recovery. The raffinate stream 902 may be recycled to fermentation to allow the unextracted SCFA salts to chain elongate into MCFAs and to provide the bicarbonates / carbonates to the fermentation, which serve as a buffering agent to control the fermentation pH.

[0167] The CO2 and the recovered fatty acids 903 (mostly MCFAs) leave through the top of the extraction or contactor column 901. The CO2 and recovered fatty acids stream 903 may go through an optional heating device (not shown). The CO2 and recovered acids stream 903 is sent to a high-pressure knockout separator or flash tank 904 to allow the bulk of the gaseous CO2 905 to separate from the acids 906. The acid stream 906 leaving the knockout separator or flash tank 904 still has an appreciable amount of CO2 dissolved in the acids; therefore, it is sent to a high-pressure stripper system 907 where heat is applied to further remove the dissolved CO2 from the acids. The stripped off CO2 908 that was dissolved in the acids 906 leaves as a gas through the top of the high-pressure stripper 907. This stripped off CO2 908 is joined with the bulk of the gaseous CO2 905 leaving the high- pressure knockout separator or flash tank 904 and the joined stream is then recompressed using a pressure boosting device, such as, but not limited to, a compressor, , a blower, or a booster fan 909 to a pressure sufficient for reintroduction into the extraction or contactor column 901. Alternatively, the pressure boosting device 909 may be an eductor or venturi that uses a circulation loop of at least some of the aqueous liquid from the bottom of the contactor bubble column 901 as the motive fluid to entrain the CO2. Before reintroduction into the column, the higher-pressure gaseous CO2 910 leaving the pressure boosting device, illustrated as booster fan 909 in FIG. 9, may be passed through an optional cooler 911, which illustratively in FIG. 9 is an air cooler, but it is not limited to such, thus other types of cooling equipment or methods, such as a water cooler or a chiller may also be used. The higher-pressure and cooled gaseous CO2 stream 912 leaving the cooler 911, can then be recycled to extraction or contactor column 901. Makeup CO2 916 is required to replenish the CO2 that leaves with the raffinate 902 as bicarbonates and carbonates and other losses. The makeup CO2 916 may be delivered to the system using makeup CO2 pump 917 and joined with recovered higher-pressure cooled gaseous CO2 912 to form one stream 918, which is then delivered to extraction or contactor column 901 at sufficient pressure. The amount of makeup CO2 916 to be delivered to the system may be set by pressure control (not shown in FIG. 9) of the extraction column or contactor 901.

[0168] The CO2 stripper 907 separates the dissolved CO2 in the acids as gaseous CO2 908, which leaves through the tops of the CO2 stripper 907. The separated CCh-leaner fatty acid stream 915 leaves through the bottoms of this same CO2 stripper 907. This CO2- leaner fatty acid stream 915 recirculates 913 through reboiler 914, which provides the energy for driving the separation process. As mentioned, these fatty acids in the CCh-leanerfatty acid stream 915 are mostly MCFAs, i.e., fatty acids >C5, which would be mostly C5- C9 fatty acids but more precisely C5-C8 fatty acids as C9 may not be produced in the fermentation in significant quantity. The CCh-leaner fatty acid stream 915 is then passed through a pressure-reducing device 921, which can be a throttling valve or an energy recovery device such as a pressure-exchanger or turbine. Such an energy recovery device would allow for some of the energy to be recovered and be used somewhere else in the process, such as, but not limited to, powering the CO2 makeup pump 917. Finally, the depressurized acid stream 922 is sent to a knockout separator or flash tank 923, which will further allow the release of any minor amount of CO2 still present 924 from the MCFAs 925. Some heating may be provided for the knockout separator or flash tank 923 to improve the separation. The CO2 stream 924 may be recycled to a compressor to become part of the makeup CO2 916 together with other sources of CO2, such as cleaned-up fermentation gas. The MCFA stream 925 may then be sent downstream for conversion into other products, such as ketones or primary alcohols, and drop-in hydrocarbon fuels.

[0169] It should be noted that these processes and systems depicted in FIG. 8 and 9 may also apply to subcritical liquid and supercritical CO2 employed as the extracting agent or solvent in the extraction or contactor columns 801 and 901, respectively, as long as sufficient energy is provided or removed in the proper heating or cooling devices to convert the CO2 into a gas as necessary for its handling, separation, recovery, and recycling. In fact, the processes and systems illustrated in FIG. 8 are especially suited for recycling liquid CO2. However, as expected, energy consumption will be higher because of the need to provide the latent heat of vaporization, thus it may be advantageous to keep CO2 operating as gas.

[0170] Use of bubble columns for extraction and recovery of fatty acids with gaseous carbon dioxide

[0171] Liquid-liquid extraction, as indicated by its name, typically refers to the contacting of two liquids to exchange the solutes that are intended to be extracted from one liquid to the other. Nonetheless, liquid-liquid extraction processes may employ either subcritical liquids or supercritical fluids to recover the solutes from the other liquid solutions. Gases, on the other hand, may be employed at times to strip volatile compounds from a liquid, which is a common and established process known as stripping. Stripping may occur in columns or towers with internals such as trays and random or structuredpacking, or in open columns with spray nozzles or liquid trays along the column’s length, known as spray towers. In addition, bubble columns have also been employed for stripping and recovery of volatile compounds from liquids. However, it is unusual to have the ability to use a gas to extract or scavenge non-volatile solutes present in a liquid phase, although it is a concept employed by foam fractionation removal of many solutes, as will be discussed later. In this regard, it is an interesting, but known phenomenon, that anionic surfactants, such as medium- and long-chain fatty acids, when found in water solutions, adsorb and get enriched at the air (z.e., non-polar gas) / water interface. Such adsorption occurs because of the affinity of the non-polar (hydrophobic) tail of the surfactant with the non-polar gas, which causes the surfactant molecules to be attracted and align with the non-polar tails towards the gas phase. In addition, due to such adsorption at the gas / water interface, the surfactants are able to be “scavenged” and captured by rising air (gas) bubbles. Furthermore, literature also shows that when it comes to MCFAs and their salts, such as C9 (nonanoic acid / nonanoate salt), the affinity of the undissociated acid towards the gas / water interface is >200X stronger compared to the salts when the gas is air. Similar results would be expected with other non-polar gases. Such facts allow the development of an innovative gas-liquid recovery process for fatty acids using bubble columns.

[0172] FIG. 10A shows a contactor bubble column 1001, which is being fed a feed solution 1000. Feed solution 1000 may be sourced from fermentation and is similar in composition and has been conditioned in a similar way as presented for feed solutions 100 through 500a / 500b in embodiments in FIGS. 1 through 5, respectively, and other streams (e.g., 616 and 724) in embodiments in FIGS. 6 and 7. Therefore, the description and conditioning of those feed solutions and streams as previously presented for FIGS. 1 through 7, also apply to the feed solution 1000 in FIG. 10A. Feed solution 1000 containing fatty acid salts (SCFAs and MCFAs) enters contactor column 1001, which is a bubble column and is contacted with bubbles of gaseous CO2 at a sufficient pressure to effect acidification, at a pressure from about 200 psig to 1000 psig. This may include pressures such as 200 psig, 300 psig, 400 psig, 500 psig, 600 psig, 700 psig, 800 psig, 900 psig, 950 psig, 1000 psig, 1100 psig, 1200 psig, 1300 psig, 1400 psig, 1500 psig, 1600 psig, or greater and, in some embodiments, less than 2000 psig. In some embodiments, the contactor column 1001 is operated at a pressure of about 800 psig to about 1000 psig. The column is operated at a temperature sufficient to have CO2 in gaseous state. The high-pressure gaseous CO2 1007 is delivered into the contactor bubble column 1001 using a bubble-generatingdevice, such as, but not limited to, an eductor or a venturi that uses a circulation loop of at least some of the liquid 1009 from the bottom of the contactor bubble column 1001 as the motive fluid to entrain CO2 (not shown in FIG. 10 A) or a sparger 1008 located at the bottom of contactor bubble column 1001. As the rising CO2 bubbles contact the aqueous solution or aqueous liquid phase 1009 containing the fatty acids salts, the CO2 does double duty of both acidifying the fatty acids salts and scavenging and capturing the recoverable fatty acids. The acidification is done by the CO2 being converted to carbonic acid in the aqueous solution, which gives off hydrogen ions and converts the fatty acid salts into acids leaving behind bicarbonate salts. At the same time, the rising CO2 bubbles scavenge and capture the more non-polar fatty acids, which have an adequate non-polar hydrocarbon tail to take advantage of the gas / water interface adsorption phenomenon alluded to above. As previously mentioned, the fatty acids that are extracted using this process would be mainly MCFAs (mostly C5-C8 as those are the MCFAs most commonly produced in fermentation, but any C9 or longer acids present would also be extracted), while the SCFAs (C2-oneC4) and other polar carboxylate salts, which might also be present (such as lactate and succinate), will remain mostly unextracted. As the aqueous feed solution 1001 enters the contactor bubble column 1001 becomes part of the aqueous liquid phase 1009. As the aqueous liquid phase 1009 makes its way down the contactor bubble column 1001, it becomes leaner on the MCFAs which the CO2 is able to recover, while the SCFA salts, cations (e.g., sodium and potassium), other polar carboxylate salts and bicarbonates remain in this solution and exit the contact bubble column 1001 through the bottom 1002. This bottom stream 1002 may be depressurized to recover CO2, which may be re-pressurized and recycled to contactor bubble column 1001, and the remaining aqueous stream may be recycled to fermentation to allow the SCFAs to chain elongate to MCFAs and to provide the buffering agent for fermentation pH control as described in previous embodiments.

[0173] As the rising bubbles carrying the captured or scavenged MCFAs reach the surface of the aqueous solution phase, they deposit the MCFAs and begin accumulating them into a separate phase. This phase will be mostly MCFAs with a portion of CO2 dissolved in it. The CO2 gas remains mostly separate showing as large bubbles making its way through the MCFA phase, thus this CCh / MCFAs stream 1003 leaving the contactor bubble column 1001 through the top, is directed to a knockout separator or flash tank 1004 to allow the bulk of the gaseous CO2 1005 to separate from the MCFAs 1006. Optionally, some heat might be applied to the knockout separator or flash tank 1004 to enhance CO2release. The released CO2 1005 may be recycled by boosting it back to the required pressure of the contactor bubble column 1001 and delivered as part of the gaseous CO2 feed 1007 to the contactor column 1001 through the bubble-generating device 1008. The pressure boosting device can be, but is not limited to, a compressor, a blower, a fan (such as what was described for booster fan 807 and 909 in FIGS. 8 and 9, respectively), or an eductor or venturi, if such is used as the bubble-generating device mentioned above, which would use a circulation loop of at least some of the liquid 1009 from the bottom of the contactor bubble column 1001 as the motive fluid to pull the CO2 1007 and entrain it into 1009. Although the bulk of the CO2 removal would occur in the knockout separator or flash tank 1004, the MCFA stream 1006, which still contains some CO2 dissolved in it, is sent to other recovery devices, such as a distillation column (812 in FIG. 8) or a stripper (907 in FIG. 9) to further recover and recycle CO2 and to obtain a CCh-lean MCFA stream in a manner previously described for previous embodiments (see FIG. 8 and 9), which also applies to this embodiment in FIG. 10A.

[0174] The inventors do not wish to be bound by any particular theory of how the CO2 bubbles acidify the fatty acid salts and scavenge the resulting fatty acids. However, to aid in understanding the disclosure as a whole, the inventors provide the following theory of operation. It should be noted that the functionality of the systems and processes otherwise described herein are not dependent on the theory that follows. FIG. 10A also shows a theoretical illustration (Y) of the zoomed in details of the interaction of the CO2 bubbles with the acidified MCFAs and other species in the contactor bubble column 1001, as is presently understood. For reference to the species, please see the legend next to illustration Y in FIG. 10A. Illustration Y in FIG. 10A zooms in on the interface between the aqueous liquid phase 1009 and the MCFAs phase 1010 with the CO2 bubbles 1012 rising and making their way through the aqueous phase 1009 and into the MCFAs phase 1010 becoming bigger bubbles 1011. Illustration Y in FIG. 10A also shows the interactions of the different ions involved and how the CO2 reacts with water to make carbonic acid to acidify the MCFA salts (R-COO ), thus producing undissociated MFCAs (R-COOH) and bicarbonate ions ( HCO3). Additionally, it shows, as per the theory proposed by Stefan and Szeri (1999) on air bubbles, how the rising bubbles 1012 scavenge and capture the undissociated MCFAs (R-COOH) through adsorption of these molecules at the gas / liquid interface around the bubble 1012 by aligning the MCFA molecules non-polar (hydrophobic) hydrocarbon tail (R-) towards the interior of the bubble, while the carboxyl head (-COOH),which is more polar (hydrophilic), remains in contact with the aqueous liquid phase 1009. Moreover, based on the measurements from Badban et al. (2017), who, as mentioned, found that the undissociated acids have a much greater affinity (>200X for C9 with air) for adsorption in the gas / liquid interface than their corresponding salts, it is expected, as depicted in illustration Y in FIG. 10 A, that most of the captured molecules will be the undissociated MCFAs, which is desired. As the rising bubbles 1012 reach the interface between the aqueous solution 1009 and the MCFAs 1010, they should be highly saturated with the MCFA molecules, which they deposit on the interface accumulating the MCFAs onto their separate phase 1010 and the bubbles transition from the aqueous phase 1009 to the MCFA phase 1010. The bulk of the CO2 is still observed as bubbles 1011 as they rise through the MCFA phase 1010. However, CO2 is also dissolved in the MCFA phase 1010, which avoids the salts from entering the MCFA phase in a substantial amount, as they would immediately be converted to carbonate / bicarbonates and migrate back to the aqueous phase 1009, which keeps the cation concentration low (<500 ppm) in the MCFA phase 1010. An experimental observation of this process was captured in a snapshot of the aqueous phase 1009 / MCFAs phase 1010 interface seen through a sight glass in a high- pressure column operating as a bubble column, which can also be seen in FIG. 10B as illustration Z. Illustration Z in FIG. 10B shows a schematic depiction of the CO2 bubbles 1012 in a column rising through the aqueous phase 1009 at the bottom and into the MCFA phase 1010 at the top with CO2 bubbles 1011 also observed in this MCFA phase at the top.

[0175] Other embodiments are also provided for contactor bubble columns. FIG. 11 shows a contactor bubble column 1101, which is similar to contactor bubble column 1001 shown in FIG. 10A processing a similar feed solution 1100 as the feed solution 1000 specified for FIG. 10 A, so most of the descriptions and applications for the embodiment in FIG. 10A, including the details of illustrations Y and Z, also apply to the embodiment in FIG. 11 with most items labeled 10XX (where XX is any number) in FIG. 10A corresponding with most items labeled 11XX in FIG. 11 (e.g., rising CO2 bubbles 1012 in aqueous solution 1009 in FIG. 10A corresponds to rising CO2 bubbles 1112 in aqueous solution 1109 in FIG. 11). A difference between FIG. 10A and FIG. 11 lies in that the knockout separator 1004 in FIG. 10A is integrated into the contactor bubble column 1101 in FIG. 11 at the top, thus allowing the bulk separation of the CO2 stream 1105 directly through the top of the contactor bubble column 1101. This bulk CO2 stream 1105 can then be boosted back to the necessary pressure and recycled back to the contactor bubbleseparator 1101 as part of the high-pressure gaseous CO2 1107 fed at the bottom of the contactor bubble column 1101 through the bubble-generating device 1108. The bubblegenerating device may be, but is not limited to, an eductor or a venturi that uses a circulation loop of liquid 1109 from the bottom of the contactor bubble column 1101 as the motive fluid to entrain CO2 (not shown in FIG. 11) or a sparger 1108 located at the bottom of contactor bubble column 1101 (as also described for stream 1005 and 1007 in FIG. 10A). The description and applications of the aqueous liquid raffinate 1102 leaving through the bottom of contactor bubble column 1101 is the same as the description and applications of the liquid raffinate 1002 leaving through the bottom of the contactor bubble column 1001 in FIG. 10 A; therefore, the description and applications of that stream 1002 in FIG. 10A fully applies to stream 1102 in FIG. 11. The MCFA phase 1110 leaves the contactor bubble column 1101 through a separate outlet and this MCFA stream 1106, which still contains some CO2 dissolved in it, is sent to other recovery devices, such as a distillation column (e.g., 812 in FIG. 8) or a stripper (e.g., 907 in FIG. 9) to further recover and recycle CO2 and to obtain a CCh-lean MCFA stream in a manner previously described for previous embodiments (see FIG. 8 and 9), which also applies to stream 1006 in FIG. 10A. The advantage of having the knockout separator 1004 of FIG. 10A integrated onto the top of the contactor bubble column 1101 in FIG. 11 is that it constitutes capital expense savings, however, it may also offer less flexibility, such as making it more difficult to provide heat to enhance CO2 release as it may be done with the knockout separator or flash tank 1004 in FIG. 10 A.

[0176] Another embodiment of a contactor bubble column for recovery of fatty acids from fatty acid salts solutions is shown in FIG. 12. FIG. 12 shows a contactor bubble column 1201, which is similar to the contactor columns 1001 1101 shown in FIGS. 10 and 11, respectively. A feed solution 1200 similar to the feed solution 1000 specified for FIG. 10A and the feed solution 1100 specified for FIG 11 is provided to the contactor column 1201, so most of the descriptions and applications for the embodiments in FIG 10A and FIG. 11, including the details of illustrations Y and Z in FIGS. 10A and 10B, also apply to the embodiment in FIG. 11. Most items labeled 10XX in FIG. 10 and 11XX in FIG. 11 correspond with most items labeled 12XX in FIG. 12, where XX are the corresponding two- digit numbers (e.g., rising CO2 bubbles 1012 and 1112 in aqueous solution 1009 and 1109 in FIG. 10A and 11, respectively correspond to rising CO2 bubbles 1212 in aqueous solution 1209 in FIG. 12). As in the embodiment in FIG. 11, FIG. 12 also integrates the knockoutseparator 1004 of the embodiment of FIG. 10A at the top of contactor bubble column 1201; therefore, all descriptions and applications above for FIG. 11 regarding this integration also apply to FIG. 12 and will not be repeated here. A difference between the embodiments illustrated in FIG. 11 and FIG. 12 lies specifically in the addition of spacers 1213 along the length of the contactor bubble column 1201 in FIG. 12. These spacers 1213 can be any type of separation device or fitting with the dual purpose of avoiding back mixing and of breaking up the rising bubbles to improve mass transfer. Avoiding back mixing is important to have adequate staging along the length of the column with concentration gradients from one stage to the next, which would result in a proper countercurrent extraction as it is typically desired to enhance recovery. For efficient extraction, the aqueous phase 1209 should become leaner of the MCFAs being extracted by the CO2 as the aqueous phase 1209 travels from the inlet of the feed solution 1200 at the top to the bottom of contactor bubble column where the raffinate 1202 exits, which cannot be efficiently accomplished if a high degree of back mixing were to occur within the column. Although, as mentioned, any suitable device or fitting that can serve the dual purpose of avoiding back mixing and bubble breakup can be used as spacers, details of an example of such spacers 1213 are also shown in FIG. 12. As illustrated, the spacers 1213 may be plates with perforations, which are simple and inexpensive but can efficiently accomplish the tasks. Multi-stage bubble columns using perforated plates as spacers are not a new concept and they have been proposed for bubble column reactors, such as in Fischer-Tropsch conversion of synthesis gas (CO + H2) to paraffins.

[0177] FIG. 13 shows almost the same embodiment as that of FIG. 12, so all the details, descriptions and applications mentioned above in reference to FIG. 12, including how it relates to FIG. 10A and FIG. 11 and other embodiments, also apply to FIG. 13 and will not be repeated. Similarly, all items labeled 13XX (with XX being some number) in FIG. 13, correspond to items labeled 10XX, 11XX and 12XX in FIGS. 10, 11 and 12, respectively (e.g., rising CO2 bubbles 1012, 1112, 1212 in aqueous solution 1009, 1109 and 1209 in FIGS. 10, 11 and 12, respectively correspond to rising CO2 bubbles 1312 in aqueous solution 1309 in FIG. 13). Illustrations A and B in FIG. 13 show the same embodiment from two different angles. A difference between the embodiment illustrated in FIG. 12 and that illustrated in FIG. 13 is that in the embodiment illustrated in FIG. 13 one or more cooling tubes 1314 are added to allow temperature control of the extraction process by passing a cooling or heating fluid 1315 through these tubes. The perforated plates 1313used as spacers can also serve as support for these cooling tubes 1314 running along the column 1301. The spacer plate 1313 detail shows the holes 1316 used to allow the aqueous liquid phase and bubbles to go through and the holes 1317 that serve for the cooling tubes 1314 to go through and provide support for them. The concept of the cooling tubes has also been proposed for bubble column reactors.

[0178] Use of foam fractionation for recovery of fatty acids with gaseous carbon dioxide

[0179] As with bubble columns discussed in the embodiments illustrated in FIGS. 10 through 12, foam fractionation also relies on the affinity of a target compound to adhere to a bubble surface in a column with bubbles rising up through an aqueous phase. In foam fractionation, the carrier gas flowrate is adjusted sufficiently high such that a foam layer is produced on top of the aqueous layer and then carried overhead and away from the aqueous layer into a foam recovery section that is separated from the bulk aqueous solution. In the foam recovery and separation section, the foam is allowed to settle and break, releasing the gas inside of the bubbles and allowing the liquid from the “broken” bubble surface and the interstitial liquid between bubbles to flow down and collect at the bottom of the foam recovery and separation section. Inside the foam, the liquid at the bubble surface, and to a lesser extent the interstitial liquid, has a higher concentration of the targeted compound due to the affinity of the targeted compound for the bubble surface; therefore, the liquid collected in the foam recovery and separation section is enriched in the targeted compound. At the bottom of the system, a “quiet” section allows the liquid with a low concentration of the extracted or recovered targeted compound to exit the system as raffinate. Similar equipment to the one employed in other foam fractionation systems, as explained above, having a foam formation section, an overhead foam recovery and separation section, and an aqueous phase quiet section, is depicted in FIGS. 14 and 15 and are described in detail below.

[0180] Foam fractionation systems conventionally use air as the sparging or bubbling gas and operate at or near atmospheric pressure. In contrast, FIG. 14 shows an embodiment in which a foam fractionation system uses CO2 as the main gas and operates at a high pressure to cause acidification of fatty acid salts and to capture and recover the resulting fatty acids. This foam fractionation system has three sections: A foam formation section 1435, a foam recovery and separation section 1434, and an aqueous phase quietsection 1436. As mentioned, in most conventional foam fractionators, when the foam breaks in the overhead foam recovery section, the liquid collected forms a single phase or an aqueous slurry of the target compound. The liquid or slurry is removed from the overhead recovery section as a single stream or a multitude of similar streams. In the present embodiments, the target fatty acids will form a distinct second phase 1410 after enrichment similar to the formation of the fatty acid or organic phase in the bubble column systems described for FIGS. 10 through 13. While in principle, it may be possible that all the aqueous material may drain from the foam back down the column before the foam spills into the overhead recovery section, in practice there will be some aqueous material entrained on the bubble surfaces or in the interstitial liquid in the foam. With proper design of the overhead recovery and separation section, the fatty acid phase 1410 separates from the aqueous phase 1427 and exits the overhead recovery and separation section as a separate fatty acid stream 1406, separate from the aqueous phase 1427. The fatty acid stream 1406 will still contain a small amount of dissolved water, CO2, and other small quantities of impurities, such as cations, as in the case of the organic stream recovered in the bubble column systems.

[0181] In the embodiments illustrated in FIG. 14, a foam fractionation column 1401 is fed a feed solution 1400 that enters at the top of the foam formation section 1435. Feed solution 1400 may be sourced from fermentation and is similar in composition and has been conditioned in a similar way as discussed for feed solutions 100 through 500a / 500b for the embodiments illustrated in FIGS. 1 through 4, respectively, and other streams (e.g., 616 and 724) in embodiments in FIGS. 6 and 7; therefore, the description of the origin, composition, and conditioning of those feed solutions and streams as previously presented for FIGS. 1 through 7 also apply to the feed solution 1400 in FIG. 14 and are not repeated here. As the feed solution 1400 containing fatty acid salts (SCFAs and MCFAs) enters column 1401, it is contacted with bubbles of CO2 at the desired pressure to effect acidification, the desired pressure being from about 200 psig to about 1000 psig. This pressure may include 200 psig, 300 psig, 400 psig, 500 psig, 600 psig, 700 psig, 800 psig, 900 psig, 950 psig, 1000 psig, 1100 psig, 1200 psig, 1300 psig, 1400 psig, 1500 psig, 1600 psig, or greater and, in some embodiments, less than 2000 psig. In some embodiments, the column 1401 is operated at a pressure of about 800 to about 1000 psig. The column 1401 is operated at a sufficient temperature to have CO2 in gaseous state at the selected operating pressure. In other embodiments, the foam fractionation system is operated with subcritical liquid orsupercritical CO2. The pressure may be controlled using pressure control 1424 together with signal 1423 and control valve 1422, which controls the amount of makeup high- pressureCCh 1407 delivered to the foam fractionation column 1401. This makeup high- pressure CO2 1407 is joined to the CO2 1405 that is leaving the foam recovery and separation section 1434 of the foam fractionation column 1401 and this combined CO2 stream 1419 is delivered into the bottom of the column 1401 in the foam formation section 1435 to form the foam. For this purpose, the combined CO2 stream 1419 may be intimately mixed with an aqueous liquid stream 1404 from the bottom of the column 1401, aqueous phase quiet section 1436. This aqueous liquid 1404, which is part of the bubble-free aqueous liquid 1409 that leaves through the bottom of aqueous phase quiet section 1436 as raffinate 1403, should have a relatively low concentration of the fatty acids being extracted, and should be high in carbonates / bicarbonates, which take the place of the extracted fatty acids as acidification occurs. The intimate mixing of the aqueous liquid 1404 and the combined CO2 1409 mentioned above is done using a bubble- or foam-generating device 1418, such as, but not limited to, an eductor or a venturi. When the bubble- or foamgenerating device 1418 is a venturi, as illustrated in FIG. 14, the aqueous liquid 1404 is pumped 1416 and becomes the motive stream 1417 that drives the venturi and that also intimately mixes or entrains the combined CO2 stream 1419, such that the liquid / gas mix 1420 exiting the venturi 1418 carries a large quantity of entrained CO2. This liquid / gas mix 1420 is delivered at the bottom of the foam formation section 1435 using a distributor 1408 to ensure even distribution of the liquid / gas mix over the cross-sectional area of the column 1401. As with the bubble column contactor previously described for FIGS. 10 through 13, the rising CO2 bubbles 1412 contact the aqueous solution or aqueous liquid phase containing the fatty acids salts and making its way downwards within the foam fractionation column 1401. The CO2 does double duty of both acidifying the fatty acids salts into fatty acids, and scavenging and capturing the recoverable fatty acids (primarily MCFAs). The final raffinate 1402, which is lean in recoverable fatty acids but is substantially comprised of unextracted fatty acids (primarily SCFAs or salts thereof) and carbonates / bicarbonates, exits the bottom of the foam fractionation column 1401 at the aqueous phase quiet section 1436. A level control system 1413 with signal 1414 may be implemented to maintain the aqueous phase level at the top of the foam formation section 1435 by controlling valve 1415, which allows the final raffinate 1402 to flow out of the system. Similar to the raffinate in previous embodiments described for previous figures, the final raffinate 1402 is substantially rich in the unextracted SCFA salts (C2-C5 fatty acid salts) andsodium / potassium carbonate and bicarbonate, this final raffinate 1402 may be treated in a manner similar to previous embodiments, such as being recycled to fermentation to allow the SCFA salts to biologically elongate using the rBOX metabolic process.

[0182] In contrast to the bubble column, the fatty acid phase in the foam fractionation column 1401 does not accumulate on top of the aqueous phase in the column but rather carries over the top of the foam fractionation section 1435 through conduit 1421 as foam 1411 and spills over to the foam recovery and separation section 1434. The top foam recovery and separation section 1434 of the fractionation column is contained in an enlarged separation vessel to allow the foam ample surface area to break. The CO2 gas 1405 released from the breaking foam continues to rise and exits the top or near the top of the foam recovery and separation section 1434 so as not to disturb the separation of the two liquid phases below and is recycled back to the bottom of the foam formation section 1435 as described above. The liquid released from the breaking foam 1411 collects in the bottom of the separation vessel where ample residence time is provided to allow the fatty acid phase 1410 to separate from any aqueous phase 1427 that was entrained in the foam. The material 1427 of the aqueous phase that collects in the separation vessel drains back into the fractionation column 1401 as an aqueous phase recycle stream 1432 through a first outlet and a control valve 1431 with a check valve 1437 to avoid backflow from the column. Meanwhile, the fatty acids from the fatty acid phase 1410 are removed through a second outlet with control valve 1428 as a recovered fatty acid stream 1406. The recovered fatty acids 1406 still contain CO2 dissolved in them, which could be removed at high pressure in a separate high-pressure device, such as, but not limited to, a distillation column or a CO2 stripper as described for streams 811 and 906 in FIGS. 8 and 9, respectively, to recover high-pressure CO2 for recycle to the fractionation column 1401 as part of make-up CO2 1407. Level control within the column 1401 is provided to maintain the fatty acid / organic phase interface 1433 and the CCh / fatty acid phase interface 1430 within narrow vertical ranges using the control valves 1431 and 1428, respectively. Furthermore, with proper baffling 1426, the foam may be directed to an area of separation sufficiently far away from the level measurement such that the level measurement occurs in a relatively undisturbed area of the vessel.

[0183] Alternatively, if a sufficient foam layer does not form such that the fatty acid phase does not carry over, the fatty acid phase will form at the top of the foam formationsection 1435 as in the embodiments using a bubble column, as described in reference to FIGS. 10 through 14. In this case, as the rising CO2 deposits more fatty acid into the fatty acid phase 1410, excess fatty acid will separate from the CO2 bubbles at the top of the foam formation section 1435 and spill over through conduit 1421 into the foam recovery and separation section. As the fatty acid accumulates in the liquid collection area, a fatty acid phase 1410 will be formed, and any entrained aqueous phase 1427 will separate as described previously.

[0184] The benefit of the described foam fractionation equipment concept over the previously described bubble column of FIGS. 10 through 13 is that the overhead separation equipment allows for separation of a relatively large volume of CO2 gas away from the two liquid phases. Such separation occurs before the liquid / liquid phase interface is measured for level control. This separation section 1434 allows for higher CO2 flowrates to be employed, which is advantageous as the recovery of fatty acids from the aqueous feed increases with increasing CO2 flowrates (see Example 6 below, which shows a positive correlation between extraction efficiencies or recoveries and CO2 flowrate / feed solution flowrate ratios). If a foam layer 1411 can form as described, it may provide additional separation of the fatty acid 1410 and aqueous phases 1427 in the fractionation column, such that less entrained aqueous material carries over into the foam recovery and separation section 1434 or it may prevent re-absorption of fatty acids into the aqueous phase at the top of aqueous phase.

[0185] Further advantages can be realized by the common feature implemented in the embodiments using a foam fractionator, typically seen for protein removal (z.e., protein skimmers), which is the use of an eductor or venturi 1418 to pull the CO2 gas 1405 from the headspace down to the bottom of the foam formation section 1435. The motive stream 1417 used in the eductor or venturi 1418 is some of the free aqueous liquid 1409, thereby efficiently recirculating and entraining the gas used to form bubbles instead of having to supply all the gas for the bubbles with more expensive compressors or blowers. The use of the eductor / venturi 1418 allows for a relatively high, but economic, CO2 gas flow rate. As shown in FIG. 14, a small amount of makeup high-pressure CO2 1407 will need to be supplied to replenish the dissolved CO2 that leaves with the raffinate, the CO2 that leaves with the raffinate as carbonates / bicarbonates, and the dissolved CO2 that leaves with the recovered fatty acids.

[0186] FIG. 15 shows embodiments including a foam fractionation system similar to the embodiments illustrated in FIG. 14. Like the embodiments illustrated in FIG. 14, those illustrated in FIG. 15 also include a foam fractionation column 1501 having a foam formation section 1535, an aqueous phase quiet section 1536 at the bottom, and a foam separation and recovery section 1534 attached at the top of the column. A feed solution1500 containing fatty acid salts (SCFA and MCFA salts) enters near the top of the foam formation section 1535 of the foam fractionation column 1501. Feed solution 1500 may be sourced from fermentation and is similar in composition and has been conditioned as presented for feed solutions 100 through 500a / 500b in the embodiments described in reference to FIGS. 1 through 5, respectively, and other streams (e.g., 616 and 724) in embodiments described in reference to FIGS. 6 and 7; therefore, the description and conditioning of those feed solutions and streams as previously presented for FIGS. 1 through 7 also apply to the feed solution 1500 in FIG. 15. As the feed solution 1500 containing fatty acid salts (SCFA and MCFA salts) enters column 1501, it is contacted with bubbles of CO2 at a pressure selected to effect acidification, such as from about 200 psig to about 2000 psig. This may include pressures of about 200 psig, 300 psig, 400 psig, 500 psig, 600 psig, 700 psig, 800 psig, 900 psig, 950 psig, 1000 psig, 1100 psig, 1200 psig, 1300 psig, 1400 psig, 1500 psig, 1600 psig, or greater and, in some embodiments, less than 2000 psig. In some embodiments, the fractionation column 1501 is operated at a pressure of about 800 to about 1000 psig. In some embodiments, the fractionation column 1501 is operated at a temperature sufficient to have CO2 in gaseous state for the selected operating pressure. In some embodiments, the fractionation column 1501 is operated with subcritical liquid or supercritical CO2.

[0187] Compared to the system in FIG. 14, the system in FIG.15 has other features that allow for improved process control. Specifically, the level of column 1501 is maintained by controlling the aqueous liquid level 1527 in the foam recovery and separation section 1534. The makeup CO2 1507 is added directly to the foam recovery and separation section 1534 and a spray system to control the foam is implemented in the foam recovery and separation section 1534. The pressure may be controlled using pressure control 1524 together with signal 1523 and control valve 1522, which delivers more CO2 1507 to the system in the foam recovery and separation section (1534). The CO2 1519 in the foam recovery and separation section 1534 is delivered into the bottom of the contactor column1501 in the foam formation section 1535 to form the foam. For this purpose, the CO2 stream1519 may be intimately mixed with the liquid 1504 from the bottom of the column 1501, aqueous phase quiet section 1536. This aqueous liquid 1504, which is part of the bubble- free aqueous liquid 1509 that leaves through the bottom of aqueous phase quiet section 1536 as raffinate 1502 should have a relatively low concentration of the fatty acids being extracted, but should be high in carbonates / bicarbonates, which take the place of the extracted fatty acids as acidification occurs. The intimate mixing of the aqueous liquid and the CO2 mentioned above is done using a bubble- or foam-generating device, such as, but not limited to, an eductor or a venturi 1518. The liquid 1504 is pumped 1516 and becomes the motive stream 1517 that drives the venturi 1518 and that also intimately mixes or entrains the CO2 stream 1519, such that the liquid / gas mix 1520 exiting the venturi 1518 carries a large quantity of entrained CO2. This liquid / gas mix 1520 is delivered at the bottom of the foam formation section 1535 using a distributor 1508 to ensure even distribution of the liquid / gas mix over the cross-sectional area of the column 1501. As with the bubble column contactor previously described for FIGS. 10 through 13, the rising CO2 bubbles 1512 contact the aqueous solution or aqueous liquid phase making its way downwards containing the fatty acids salts, and the CO2 does double duty of both acidifying the fatty acids salts and scavenging and capturing the recoverable fatty acids. The final raffinate 1502, which is lean in recoverable fatty acids but is substantially comprised of unextracted fatty acids and carbonates / bicarbonates, exits the bottom of the foam fractionation column 1501 at the aqueous phase quiet section 1536. A level control system 1533 with signal 1514 may be implemented to maintain the aqueous phase level at the top of the foam formation section 1435 but also the overall aqueous liquid level of the foam fractionation column 1501. The level control opens or closes the valve 1515, which allows the final raffinate 1502 to flow out of the system. Similar to the raffinate in previous embodiments described for other figures, the raffinate 1502 is substantially rich in the unextracted SCFA salts (C2 - C5 fatty acid salts) and sodium / potassium carbonate and bicarbonate, and this raffinate may be treated in a manner similar to previous embodiments and recycled to fermentation to allow the SCFA salts to biologically elongate using the rBOX metabolic process.

[0188] In contrast to the bubble columns, the fatty acid phase in the foam fractionation column 1501 does not accumulate on top of the aqueous phase in the column but rather carries over the top of the foam fractionation section 1535 through conduit 1521, which can be observed in FIG. 15 on the side view as well. Foam 1511 rises and spills overthrough conduit 1521 to the foam recovery and separation section 1534. The top foam recovery and separation section 1534 of the fractionation column is contained in an enlarged separation vessel to allow the foam ample surface area to break. The CO2 gas released from the breaking foam continues to rise and exits 1519 the foam recovery and separation section 1534 so as not to disturb the separation of the two liquid phases below, and is recycled back to the bottom of the foam formation section 1535 as described above. The liquid released from the breaking foam 1511 collects in the bottom of the separation vessel where ample residence time is provided to allow the fatty acid phase 1510 to separate from any aqueous phase 1527 that was entrained in the foam. Aqueous material 1527 that collects in the separation vessel drains back into the fractionation column through a first outlet and valve 1531 as aqueous stream 1532 with a check valve 1537 to avoid backflow. The drain rate is also controlled by the raffinate outlet valve 1515 as it allows raffinate 1502 leave the system. Meanwhile, the fatty acids from the fatty acid layer 1510 are removed through another outlet with control valve 1528 as a fatty acid stream 1506. The fatty acid stream 1506 still contains dissolved CO2 , which could be removed at high pressure in a separate high-pressure device, such as, but not limited to, a distillation column or a CO2 stripper as described for streams 811 and 906 in FIGS. 8 and 9, respectively to recover such high-pressure CO2 for recycle to the foam fractionation column 1501 as part of make-up CO2 1507. Level control 1530 is also provided to maintain the fatty acid / organic phase 1510 level within selected narrow vertical ranges using the control valve 1528 while allowing the fatty acids 1506 to leave the system. Furthermore, with proper baffling 1526, the foam may be directed to an area of separation sufficiently far away from the level measurement such that the level measurement occurs in a relatively undisturbed area of the vessel. The baffling 1526 can also be observed in the side view of FIG. 15 and it is shown to expand the whole width of the foam recovery and separation section 1534, not allowing the foam to ever move into the foam-free area where level control is performed. Studies of CO2 foam stability at high pressures have shown that CO2 foam is more stable at high pressures than at lower pressures and more stable than nitrogen gas (N2) foams, which would suggest that CO2 foam is more stable than air (78% N2) foam. To ensure that the foam breaks properly and in a timely manner, part of the organic phase 1510 or of the aqueous phase 1527 in the foam recovery and separation section 1534 is pumped 1543 and recirculated to a spray nozzle 1545 as foam level is detected with a level sensor 1541 and signal 1542. The level sensor 1541 may toggle operation of the pump 1543 to provide part of the organic phase1510 or of the aqueous phase 1527 in the foam recovery and separation section 1534 to the spray nozzle 1545.

[0189] The systems and processes in FIGS. 14 and 15 employ high-pressure systems to be able to both acidify and recover the fatty acids using foam fractionation. FIG. 16 shows a more conventional foam fractionation system and process where the MCFA salts are removed from the incoming feed solution at atmospheric pressure using either air, CO2, or other gas, but preferably air. Because the MCFAs are in their salt form and are not acidified yet, the salts are removed and the foam with the MCFA salts is sent to the foam recovery and separation section where it is allowed to settle and break. This results in a concentrated MCFA salts solution, which may then be pressurized and acidified with CO2.

[0190] In an embodiment, a feed solution 1600 containing fatty acid salts (SCFA and MCFA salts) enters near the top of the foam formation section of the foam fractionation column 1601. Feed solution 1500 may be sourced from fermentation and is similar in composition and has been conditioned in a similar way as presented for feed solutions 100 through 500a / 500b in embodiments in FIGS. 1 through 5, respectively, and other streams (e.g., 616 and 724) in embodiments in FIGS. 6 and 7; therefore, the description of the origin, composition, and conditioning of those feed solutions and streams as previously presented for FIGS. 1 through 7, also apply to the feed solution 1600 in FIG. 16 and will not be repeated here. As the feed solution 1500 containing fatty acid salts (SCFAs and MCFAs) enters column 1401, it is contacted with bubbles of air, CO2ior other gas at ambient pressure. The air, CO2 or other gas 1602 is delivered at the bottom of the foam fractionation column 1601. As in previous embodiments, a blower, compressor, or a venturi or eductor can by employed to deliver the air, CCC or other gas 1602 to the bottom of the foam fractionation column 1601. A distributor 1608 is used to deliver the gas. Below the distributor, the aqueous quiet zone lies, where MCFA-lean aqueous liquid 1609 that has descended below the distributor is directed to the outlet as raffinate 1602. The same description for the raffinate as in previous embodiments described for previous figures applies here, where the raffinate 1602 is substantially rich in the unextracted SCFA salts (C2 - C5 fatty acid salts) and sodium / potassium carbonate and bicarbonate. This raffinate 1602 may be treated in a manner similar to previous embodiments and recycled to fermentation to allow the SCFA salts to biologically elongate using the rBOX metabolic pathway.

[0191] The foam 1611 exits the foam formation section of the foam fractionation column 1601 and the foam stream 1621 is directed to the foam recovery and separation section or vessel 1625. This foam recovery and separation section can be incorporated on the top of the foam fractionation column 1601 as in the embodiments previously discussed with reference to FIGS. 14 and 15, or it can be a separate vessel as shown in FIG. 16. In this foam recovery and separation section / vessel 1625, the foam settles and breaks separating the gas (e.g., air, CO2) 1619 and a concentrated aqueous solution of the MCFA salts 1627 forms, which exits this unit as stream 1646 (note: the gas stream 1619 might require recycling if the gas is CO2 or other non-air pure gas). The concentrated MCFA salts aqueous stream 1646 is then pumped using high-pressure pump 1647 and sent to a high- pressure vessel 1649 where high-pressure CO2 1650 is added at a pressure selected to cause acidification of the fatty acid salts and may be from about 200 psig to 2000 psig. This pressure may include 200 psig, 300 psig, 400 psig, 500 psig, 600 psig, 700 psig, 800 psig, 900 psig, 950 psig, 1000 psig, , 1100 psig, 1200 psig, 1300 psig, 1400 psig, 1500 psig, 1600 psig, or greater and, in some embodiments, less than 2000 psig. In some embodiments, the high-pressure CO2 is added at a pressure of less than 500 psig or in the range or 800 to 1000 psig. In some embodiments, the high-pressure vessel 1649 is operated at a temperature sufficient to have CO2 in a gaseous state at the selected pressure. In other embodiments, the high-pressure vessel 1649 is operated at a temperature and pressure such that the CO2 is in a subcritical liquid or supercritical state. The acidified mixture 1651 is sent through a coalescing section and an optional heater may be used to increase the temperature of the acidified mixture to allow more efficient separation of any dissolved or entrained CO2 (not shown in FIG. 16). The acidified mixture then enters a phase separation vessel 1652 where the acids are allowed to phase separate from the aqueous liquid. If present, CO2 gas 1654 will also separate from the liquid phases, and may be recycled to the high-pressure CO2 vessel 1649 by recompressing it and processing it in a manner similar to what was described for streams 806 or 905 in the embodiments described with reference to FIGS. 8 and 9, respectively. Similarly, the separated acids 1606, which still contain some dissolved CO2, are also treated in a manner similar to streams 811 or 906 in FIGS. 8 and 9, respectively to recover the dissolved CO2 (i.e., the separated acid stream may be depressurized and provided to a phase separator (not shown)). The aqueous phase 1653 from phase separation vessel 1652, which might still contain some recoverable MCFAs, is depressurized by going through pressure reducing device 1655, which can be, but is not limited to, a throttling valve. In other embodiments, the pressure reducing device 1655 may be an energy recoverydevice such as, but not limited to, a turbine or a pressure exchanger, which can be coupled to the pressure boosting pump 1647, for example, thus providing at least a portion of the energy for the pump. Finally, the pressure-reduced aqueous stream 1632, containing the unconverted or unacidified MCFA salts and carbonates / bicarbonates is recycled back to the front of the foam fractionation column 1601, where it is mixed with the feed solution 1600 as it is fed to the foam fractionation column 1601. The use of CO2 in vessel 1601 to form the foam and the recycle of the partially acidified aqueous stream 1632 might have advantages over using air because results have shown that lower pH, which can be achieved by carbonation, allows better foam formation than higher pHs.

[0192] It is also important to mention that, as observed in DAF processes, particles are also carried over by foam, thus another advantage of the foam fractionation processes and systems described with reference to figures FIGS. 14, 15, and 16 is that these processes and systems may avoid the formation of rag layers that are hard to deal with in conventional liquid-liquid separators.

[0193] To summarize, the concept of using a CCh-based fatty acid recovery system to recover fatty acids from aqueous feed solutions containing fatty acid salts, as described in all the above embodiments, and the subsequent use of the recovered fatty acids to produce hydrocarbon biofuels or other valuable products provides multiple benefits:

[0194] 1. It selectively recovers the desired MCFAs (e.g., C5-C8 acids), whose chain length is ideal for hydrocarbon production and allows recycle of the fatty acids falling outside of the ideal carbon chain length range (e.g., SCFAs, C2-C4 acids) to fermentation for biological elongation to the desired MCFAs.

[0195] 2. CO2 recovery and recycle is the main energy consumer but this consumption is low compared to the distillation energy requirements in other alternative process, such as ethanol production, and its conversion to jet fuel (alcohol -to-jet or ATJ), especially if gaseous CO2 is employed.

[0196] 3 The recovered acid product is relatively pure and only requires simple purification to remove the small amounts of water, SCFAs, and heavy impurities (e.g., MCFA salts) present in the recovered acid product before the subsequent conversion to hydrocarbons.

[0197] 4. The fermentation and acidification processes can be tightly integrated to efficiently use CO2. The CO2 consumed in a CO2 fatty acid recovery process becomes a fermentation buffer, which can recycled with the raffinate to fermentation, thus providing the buffering agent required for fermentation pH control and then later such CO2 can be recovered from the fermentation gases for re-use in the CO2 fatty acid recovery process.

[0198] 5. CO2 recovery from fermentation can provide all the CO2 necessary in theCO2 fatty acid recovery process with excess (especially if downstream ketonization is employed). And, because CO2 recovery, clean-up, and recompression is already part of the process, the CO2 excess may be used in carbon capture, utilization, and / or storage (CCUS) to further decrease the carbon intensity of the process without a large burden in capital or operating expenses.

[0199] Tolling, hub-and-spoke and integration with renewable diesel and hydroprocessed esters and fatty acids SAF production facilities

[0200] As disclosed herein, further conversion of MCFAs to hydrocarbons has two main pathways described previously in embodiments with reference to FIGS. 1 through 7. These pathways include: 1. ketonization + hydrodeoxygenation + hydrocarbon refining (ketonization route), and 2. hydrogenation + dehydration / dimerization + hydrotreating + hydrocarbon refining (primary alcohol route). As already stated, hydrocarbon refining may potentially include isomerization, cyclization, aromatization, catalytic reforming, distillation, and other processes needed to get the final hydrocarbon product to meet the necessary specifications for a marketable product. In general, both processes have feasibility, and both have advantages and disadvantages over one another. For example, the ketonization route loses one carbon as CO2 for every two molecules of MCFAs processed, which means yields are lower with that route. However, the primary alcohol route, which loses no carbon, requires 2.5X more hydrogen than the ketonization route. In an economy where hydrogen, especially if it needs to be green hydrogen, is expensive, it may be preferred to choose the ketonization route, despite lower yields due to carbon losses.

[0201] Regardless of whether the ketonization or the primary alcohol route are chosen, one of the latter steps will include HDO or hydrotreating to make paraffins. Further hydrocarbon refining, likely including isomerization and distillation steps, will also be required. All steps after ketonization or after dimerization are, in general, well-established.HDO and isomerization are known, robust, widely practiced, and mature conversion processes, with understood catalysts and reaction conditions. In the biofuel industry, renewable diesel (RD) and synthetic paraffinic kerosene (SPK) producers using the ASTM D7566 Annex A2 pathway known as hydroprocessed esters and fatty acids (HEFA) convert lipidic feedstocks such as, but not limited to, natural oils and fats from vegetable or animal origin, such as waste fats, oil and grease (FOG), vegetable oil (VO), and other lipidic feedstocks using HDO, and they also perform isomerization (ISOM, for meeting cold flow specifications) as part of the conversion process. Such familiar and proven processes open the possibilities for tolling as well as hub-and-spoke opportunities by either dedicated tolling options or by co-processing ketones or dimerized alcohols with the lipidic feedstocks mentioned above. Furthermore using ketones or dimerized alcohols represent a better feedstock for RD and HEFA as the process becomes advantaged relative to RD and HEFA when using conventional feedstocks and the ketones or dimerized alcohols will not require pretreatment, in the case of HEFA no hydrocracker is required, it uses less hydrogen requiring an up to 50% smaller hydrogen plant, and has a simplified final product separation and recovery (no heavies).

[0202] FIG. 17 illustrates this dedicated tolling and co-processing option, where ketones from the ketonization of C5-C8 VFAs, which fall in the proper C9-C15 SAF range, are sent to a separate dedicated tolling facility or co-processed in RD and HEFA facilities. VFAs 1701 undergo ketonization in a ketonization step 1702. This may occur at the same site where the VFAs, namely MCFAs substantially in the C5-C8 range, are generated by fermentation as described in FIG. 6 or 7, for example. For ketonization, this is especially convenient because the ketonization process does not require much hydrogen other than potentially a small amount for improving the reaction and for catalyst life that can be procured from the fermentation as described for the processes and systems previously illustrated in FIG. 6. The resulting ketones, which unlike the VFAs are neutral molecules, can be safely transported off-site to the tolling site or to the hub of a hub-and-spoke system, where several fermentation / acid recovery / ketonization sites serve one larger hub that converts the ketones into the final hydrocarbon fuel product.

[0203] As mentioned, there are three different options for further conversion. The first option is to transport the ketones to a dedicated tolling or hub site where HDO 1703, ISOM 1704, and distillation steps 1705 are performed only on the ketones to produce a SAFproduct 1706, in addition to small amount of gases and naphtha lights. This will require capital to build this new infrastructure, including green hydrogen production, for lower carbon intensity.

[0204] The second alternative is to send the ketones to a conventional RD plant, where HDO 1707, ISOM 1708, and distillation steps 1709 are already being done. The ketones are co-processed with the lipidic feedstocks and finally separated during distillation 1709, thus the RD facility would not only produce diesel 1711, as it might be currently doing, but also SAF 1710.

[0205] The third option would be to send the ketones to a HEFA facility, which already produces SAF using, as mentioned, the HEFA-SPK pathway (see ASTM D7566 Annex A2). This conventional system includes HDO 1712, however, to shorten the carbon chain lengths of the lipidic feedstock it typically handles and to get them into the SAF range, this process also includes mild hydrocracking (MHC) 1714. Because the ketones are already in the SAF range, they do not need to be cracked and in fact going through MHC 1714 would cause yield losses; therefore, a splitter unit 1713, such as, but not limited to, a distillation system, is placed after HDO to separate the SAF-range n-paraffins that came from the ketones from the longer paraffins that resulted from the lipidic feedstock. The SAF-range n-paraffins are by-passed 1715 and sent directly to ISOM 1716, while the longer paraffins undergo MHC 1714 to shorten the carbon chain length into the SAF range before also undergoing ISOM 1716. Finally, distillation 1717 is performed to separate the different cuts (light gases, naphtha, SAF and diesel). In HEFA facilities, little diesel is produced and most of the final product will be SAF 1718, but in HEFA / RD facilities, a larger proportion of the lipidic feedstocks end up as diesel 1719. The capital for these RD, HEFA or HEFA / RD facilities is already in place and the availability of clean ketones would be an important opportunity for these facilities as their conventional feedstocks become scarcer.

[0206] It is important to mention that the above co-processing model using ketones may also be practiced with primary alcohols after they undergo dimerization. The same description above will apply to these C10-C16 hydrocarbons derived from the hydrogenation of C5-C8 VFAs into primary alcohols and their subsequent dimerization using, for example, 0 zeolite catalysts.

[0207] General Methods of Producing Hydrocarbons from Fatty Acid Salts

[0208] Provided herein are methods and systems to produce useful and valuable hydrocarbons, such as those suitable for use in fuels, from feeds containing fatty acid salts, such as those obtainable from the fermentation of biomass. In some embodiments, the methods include converting the fatty acid salts to fatty acids, and then on to ketones. With reference to FIG. 18 A, a method of producing ketones 1800 from a feed that contains fatty acid salts includes a step 1801 of contacting the feed with CO2 to acidify the fatty acid salts into the corresponding fatty acids and to extract these resulting fatty acids with the CO2; and a step of 1804 contacting the resulting fatty acids with a ketonization catalyst to produce the ketones. The fatty acids extracted by the CO2 may be produced as a mixture with the CO2, thus the method may optionally include a step 1802 of separating the CO2 from the fatty acids. In another step 1803, that could be seen as optional, this CO2 can be recycled back to be used again as an acidification agent / extractant. Additional details of how these steps are taken and the equipment that may be used to do so are provided above, for example in the discussion in reference to FIGS. 1-3 and 5-7.

[0209] As shown in FIG. 18B, a method of producing hydrocarbons from the ketones 1820 may include an optional step of 1821 of obtaining ketones produced from the ketonization of fatty acids produced and recovered from a fermentation process, as discussed above. The method includes co-processing the ketones with long-chain lipidic feedstocks in a conventional hydroprocessed esters and fatty acids process wherein coprocessing includes: a step 1822 of hydrotreating or hydrodeoxygenating the ketones and the long-chain lipidic feedstocks; a step 1823 of separating the n-paraffins having carbon chain lengths of 16 carbons or smaller (<C16) and a long-chain fraction (a fraction including n-paraffins having carbon chain lengths of greater than 16 carbons (>C16)); a step 1824 of allowing the long-chain fraction to undergo mild hydrocracking; and a step 1825 of recombining the n-paraffins having carbon chain lengths of 16 carbons or smaller with the hydrocracked fraction. In some embodiments, the ketones and lipidic feedstock is hydrotreated or hydrodeoxygenated in the same step. In order to meet the required product specifications (such as, cold flow properties or freeze point requirements), the combined material can be subjected to a step 1826 of additional hydrocarbon refining, which may include isomerization, aromatization, and / or fractionation of the combined product. In some embodiments, this method may be used to produce hydrocarbons suitable for use as a sustainable aviation fuel or fuel additive. Additional details on the process and equipment for carrying out this method is provided above.

[0210] In other embodiments, the methods include converting the fatty acid salts to fatty acids, and then on to primary alcohols. With reference to FIG. 18C, a method of producing primary alcohols 1830 from a feed that contains fatty acid salts includes a step 1831 of contacting the feed with CO2 to acidify the fatty acid salts into the corresponding fatty acids and to extract these resulting fatty acids with the CO2; and a step of 1834 contacting the resulting fatty acids with a hydrogenation catalyst to produce the primary alcohols. The alcohols may be produced as a mixture with the CO2, and so the method 1830 may include an optional step 1832 of separating the CO2 from the primary alcohols and another optional step 1833 of recycling all or part of the CO2 for reuse as an acidification agent / extractant in the contacting step 1831. Details on the equipment and process for carrying out this method are provided above, for example in the discussion with reference to FIGS. 1, 4-6.

[0211] As shown in FIG. 18D, a method of producing hydrocarbons from the primary alcohols 1840 may include an optional step of 1841 of obtaining primary alcohols produced from the hydrogenation of fatty acids produced and recovered from a fermentation process, as discussed above, and an optional step 1842 of dimerizing the primary alcohols. The method includes co-processing the ketones with long-chain lipidic feedstocks in a conventional hydroprocessed esters and fatty acids process wherein co-processing includes: a step 1843 of hydrotreating or hydrodeoxygenating the dimerized alcohols and the long- chain lipidic feedstocks; a step 1844 of separating the n-paraffins having a carbon chain length of 16 carbons or less (<C16) from a long-chain fraction (including paraffins having a carbon chain length of more than 16 carbons (>C16)) to form a hydrocracked fraction; a step 1845 of allowing the long-chain fraction to undergo mild hydrocracking; and a step 1846 of recombining the n-paraffins having a chain length of 16 carbons or less with the hydrocracked fraction. In order to meet the required product specifications (such as, cold flow properties or freeze point), the combined material can be subjected to a step 1847 of additional refining, which may include isomerization, aromatization, and / or fractionation of the combined product. In some embodiments, the dimerized alcohols and lipidic feedstock is hydrotreated or hydrodeoxygenated in the same step. In some embodiments, this method may be used to produce hydrocarbons suitable for use as a sustainable aviation fuel or fuel additive. Additional details on the process and equipment for carrying out this method is provided above.EXAMPLES

[0212] The following examples more specifically illustrate the acidification of fatty acid salts and extraction of the resulting fatty acids by CO2 according to various embodiments described above. These examples should in no way be construed as limiting the scope of the present technology.

[0213] Example 1. In Table 1 results from an extraction of carboxylic acids, specifically, VFAs (SCFA and MCFA) salts from a sample solution using supercritical CO2 are shown. The fatty acid concentration in a solution sample were analyzed by GC-FID using a HP-FFAP column and reported by carbon chain length, i.e., C2 (acetic acid), C3 (propionic acid), iC4 (isobutyric acid), C4 (butyric acid), iC5 (isobutyric acid), C5 (valeric acid), C6 (hexanoic acid), C7 (heptanoic acid), and C8 (caprylic acid) and overall. The concentration of each fatty acid and for the fatty acids overall was determined by analyzing the aqueous solution before and after extraction (raffinate). A 500-mL sample of the sample solution containing the fatty acids was contacted with 500-mL of supercritical CO2 (33°C, and 1550 psig, density 757 kg / m3) in a well-mixed high-pressure Parr reactor. The sample of the aqueous raffinate phase was collected from the Parr reactor at the given temperature and pressure after about 2 hours to ensure equilibrium was reached, and the concentration of each fatty acid in the raffinate was measured and compared to the concentration of the initial solution. For each sample, the partition coefficient or equilibrium constant, Keq(CCh / Aq), of the fatty acids in the CO2 and aqueous phases was determined according to the equation:Keq = ([Acids]init - [Acids]raff) / ([Acids]raff)xVaq / VCCh wherein [Acids]init is the concentration of the fatty acids in the initial solution and [Acids]raff is the concentration of the fatty acids in the raffinate. VCO2 is the volume of CO2 phase and Vaq is the volume of the aqueous phase. Because it was not possible to directly measure the fatty acid concentration in the CO2, it was determined from the difference of the concentration in the aqueous phase.

[0214] The extraction equilibrium constant was calculated for each fatty acid and for the solution overall. The volumetric extraction or recovery efficiency as estimated when the volumetric solvent-to-feed ratio (VCCh / Vaq, i.e., CCh-to-feed ratio) is equal to 1, wasalso calculated for each acid and the solution overall. The volumetric extraction efficiency at solvent-to-feed (S / F) ratio = 1 was calculated as follows:T|v—Keq / (1 +Keq)Table 1. Extraction of fatty acid by supercritical CO2 at 1550 psig and 33°C

[0215] The data illustrates that CO2 is more effective at extracting longer chain fatty acids. The effectiveness of the CO2 extraction increased as the length of the fatty acids carbon chains also increased. While extraction of short chain acids (C2-C4) was relatively low, ranging from just 1-19%, the CO2 extraction was more efficient for the longer chain fatty acids with a high partition coefficient of 22.1 and achieving a 96% extraction efficiency or % recovery of C8 fatty acids (caprylic acid) in only one liquid-liquid extraction stage. A notable increase in effectiveness of the extraction is shown for valeric acids (C5, iC5) and caproic acids (C6).

[0216] Example 2. Table 2 shows the results of subcritical liquid CO2 extraction of a second carboxylic acid (fatty acid) salt solution. A 500-mL sample of an aqueous phase solution containing fatty acid salts was contacted with 124 mL of a subcritical CO2 stream at about 1000 psig and 28 °C. The fatty acids in a solution sample were analyzed by GC-FID using a HP-FFAP column and reported by carbon chain length in a similar manner as in Example 1. The relative concentration of each fatty acid and for the fatty acids overall was determined by analyzing the aqueous solution before and after extraction (raffinate).Table 2. Extraction of fatty acid salts by liquid CO2 at 28°C

[0217] Similar trends to those seen in Example 1 are repeated here, with improving extraction percentage as a function of the chain length of the fatty acid salts. The CO2 extracted a majority portion of the fatty acid salts having carbon chains C5 and longer. Overall volumetric extraction efficiency when solvent-to-feed (SZF) ratio is 1 was improved for all fractions and thus for the overall acid salts as well, with about 60% of the fatty acid salts present in the solution being extracted. Extraction efficiencies for medium-chain fatty acids were above 55% with C8 being close to 97% with only one extraction stage.

[0218] Example 3. A pilot-scale system was used to recover fatty acids from an aqueous feed solution of fatty acid salts ranging from C2 through C8 (acetic acid / acetate through caprylic acid / caprylate). This feed solution was a mixed culture fermentation effluent from a fermentation feedstock of com dextrose, corn steep liquor and other nutrients. Fermentation pH was controlled at about 6.5 by adding sodium and potassium hydroxide, thus obtaining fatty acid salts. This mixed culture fermentation was operated to maximize the rBOX chain elongation process into MCFAs (C5 through C8). After fermentation, the fermentation effluent was degassed by recirculating through a spray nozzle to remove dissolved CO2 and ammonia, which caused the pH to increase, and then clarified using nanofiltration membranes to remove precipitates (mostly phosphate) and any undigested solids, such as microbial biomass. The clarified broth, which had a fatty acid concentration of 25 to 30 g / L, was then concentrated using RO to a concentration of 69 g / L. The clean concentrated broth was then fed at the top of a Scheibel™ column, which is a mechanically agitated column (mixing speed 200 RPM), which has many extraction stages along the column separated by perforated plates or baffles, while the aqueous raffinate leftthrough the bottom of the column. CO2, on the other hand, was fed at the bottom and left through the top with the extracted acids. At the given temperature (73°F or 22.7°C) and pressure (950 psig), the CO2 is a subcritical liquid within the Scheibel™ extraction column. The CO2 leaving through the top with the extracted acids was then sent to a CO2 recovery column, which was a distillation column operating at a lower pressure (665 psig), where the CO2 was separated through the distillate of this column and was recycled, while the extracted acids with any dissolved CO2 left through the bottom of this CO2 recovery column. Table 3 shows the summary of this pilot run giving details of the operation of both the Scheibel™ extraction column and the CO2 recovery column.

[0219] Table 3. Extraction of fatty acids from a mixed culture fermentation effluent by liquid CO2 in a mechanically agitated Scheibel™ ColumnScheibel ColumnMixer Speed 200 rpmPressure 950 psigFeed SolutionRate 53 Ib / hAcid concentration 69 g / L pH 6.3Temp 73 °FCO2Rate 72 Ib / h (gas)ExtractantRate 68 Ib / hTemp 72 °FRaffinateRate 54 Ib / h pH 7.2CCh / Feed ratio (Ib / lb) 1.36CO2 / Acid flow ratio (lb / lb) 20.8CO2 recovery columnPressure 665 psigBottom temp 270 °FOH temp 56 °FCO2 recycle rate 53 Ib / hC200 Bottoms rate 1.43 Ib / hVFAs RecoveryC2 0.6 %C3 9.5 %IC4 3.9 %C4 20 %IC5 55.9 %C5 67.8 %C6 97.9 %C7 100 %C8 99.2 %

[0220] Extraction efficiencies shown in Table 3 were calculated by mass balance from the difference of the amount of each acid entering with the feed solution and the amount of each acid leaving with the raffinate divided by the amount of each acid entering with the feed solution. These values were determined according to the mass flow rates and density of the incoming feed solution and of the outgoing raffinate and the fatty acids concentration of both streams, which were also analyzed by GC-FID using a HP-FFAP column and reported by carbon chain length (i.e., C2 (acetic acid), C3 (propionic acid), iC4 (isobutyric acid), C4 (butyric acid), iC5 (isobutyric acid), C5 (valeric acid), C6 (hexanoic acid), C7 (heptanoic acid), and C8 (caprylic acid)) as in previous examples. The solvent-to- feed ratio (a.k.a. CCh / Feed ratio) is given on a weight basis (Ib / lb) instead of a volumetric basis as in Examples 1 and 2. In addition a CCh / Acid flow ratio (Ib / lb) is also reported, which is the mass flow of CO2 divided by the mass flow of acids entering the extraction system calculated from the volumetric flow of the feed solution (mass flow x density) and the acid concentration in the feed solution measured with GC-FID as mentioned above. Similarly, as with Examples 1 and 2, the CO2 extraction efficiency or recovery increases with increasing carbon chain length, with C5+ having extraction efficiencies >55%, which confirms their selective extraction as desired for further dimerization through ketonization or through hydrogenation / dimerization into the SAF range.

[0221] Example 4. A similar test as in Example 3 was performed with the same feed solution obtained from mixed culture fermentation of com dextrose, com steep liquor and other nutrients cleaned up and concentrated using the same equipment and using the same Scheibel™ extraction column but with the mixer turned off. In addition, a sparger was installed at the bottom of the Scheibel™ extraction column to feed the CO2 and test the effect of a bubble column in the extraction although the temperature (54-57°F or 12-14°C) and pressure (950 psi) suggest that the CO2 was in liquid form. The partitions of the Scheibel™ with the mixer turned off are expected to have a similar effect to having spacers as shown in FIG. 12. The average results from three runs are shown in Table 4.

[0222] Table 4. Extraction of fatty acids from a mixed culture fermentation effluent by gaseous CO2 in a bubble columnScheibel Column using SpargerMixer Speed OFF rpmPressure 950 psigBrothRate 45 Ib / hAcid concentration 53 g / L pH 8.7Temp 57 °FCO2Rate 80 Ib / hExtractantRate 79 Ib / hTemp 54 °FRaffinateRate 43 Ib / hCO2 / Feed ratio 1.78CO2 / Acid flow ratio 35.4CO2 recovery columnPressure 682 psigBottom temp 289 °FOH temp 56 °FCO2 recycle rate 61 Ib / hC200 Bottoms rate 1.1 Ib / hVFAs RecoveryC2 - %C3 7.5 % iC4 13.8 %C4 4.1 % iC5 37 %C5 37.9 %C6 92.3 %C7 100 %C8 100 %

[0223] Extraction efficiencies or % recoveries shown in Table 4 were calculated in the same way as described for Example 3. Similarly, the acid concentrations in the feed solution and the raffinate were also analyzed using GC-FID with a HP-FFAPP column with the carbon chain length for each acid as listed for Examples 1, 2 and 3. The same trend was observed with higher extraction efficiencies with increasing carbon chain length, and specifically C5+ hadextraction efficiencies above 35%. However, even though the CCh / Feed ratio and the CCh / Acid flow ratio, calculated as described above for Example 3, were higher in Example 4, the extraction efficiencies were found to be lower.

[0224] Example 5. A similar pilot-scale test to what was performed for Example 3 and 4 was carried out with a Scheibel™ extraction column operating with the mixer on as in Example 3. The aqueous feed solution was a synthetic mix of reagent-grade VFAs, which were neutralized with sodium and potassium hydroxide. The temperature (80-89°F or 27-32°C) and pressure (950 psig) suggests that the CO2 was in gas form.

[0225] Table 5. Extraction of fatty acids from a mixed culture fermentation effluent by gaseous CO2 in a mechanically agitated Scheibel™ ColumnScheibel ColumnMixer Speed 200 rpmPressure 950 psigFeed SolutionRate 15.9 Ib / hAci d concentrati on 108.16 g / L pH 7.7Temp 89.2 °FCO2Rate 30.1 Ib / h (gas)ExtractantRate 30.1 Ib / hTemp 80.4 °FRaffinateRate 13.9 Ib / h pH 7.8CCh / Feed ratio 1.89CO2 / Acid flow ratio 18.7CO2 recovery columnPressure 651 psigTemp 273 °FOH temp 56.7 °FCO2 recycle rate 45.6 Ib / hC200 Bottoms rate 2.28 Ib / hVFAs RecoveryC2 - %C3 3.2 %IC4 26.7 %C4 19.1 %IC5 62.3C5 64.2C6 99.7C7 100C8 100

[0226] Extraction efficiencies or % recoveries and the CCh / Feed and CCh / Acid flow ratios shown in Table 5 were calculated in the same way as described for Example 3 and 4. Similarly, the acid concentrations in the feed solution and the raffinate were also analyzed using GC-FID with a HP-FFAPP column with the carbon chain length for each acid as listed for Examples 1, 2, 3 and 4. The same trend was observed with higher extraction efficiencies with increasing carbon chain length, and specifically C5+ had extraction efficiencies above 60%. CCh / Feed ratio was higher than in Example 3, but CCh / Acid flow ratios were similar. Similar extraction efficiencies or recoveries were observed between Example 3, which used liquid CO2, and Example 5, which used gaseous CO2.

[0227] Example 6. A series of pilot-scale tests similar to what was performed for Examples 3, 4 and 5 were carried out with a Scheibel™ extraction column operating with the mixer on at 200 rpm as in Example 3 and 5. The aqueous feed solution was a synthetic mix of reagent-grade VFAs, which were neutralized with sodium and potassium hydroxide as in Example 5. The temperature of the incoming feed solution was at an average of 89.6°F±2.8°F (32.0°C±1.6°C), while the incoming CO2 entering the extraction column was at an average temperature of 80.9°F±0.74°F (27.2°C±0.41°C) and all these pilot-scale tests were run at a pressure of 950 psig as in Example 5. In fact, one of the data points in this Example 6 is Example 5. Under these conditions of temperature and pressure, the CO2 was in gaseous state. As mentioned, the incoming feed solution contained VFAs as neutral sodium and potassium salts, but on a VFA basis, they ranged from about 60 to 148 g VFA / L. The different tests were run at different CCh / Feed ratios calculated as described for Examples 3, 4 and 5. CCh / Acid flow ratios were also calculated as described in Examples 3, 4 and 5. FIG. 19 shows C4 (butyric), C5 (valeric) and C6 (caproic) acids extraction efficiencies or recoveries as a function of CCh / Feed ratios. The graph of FIG. 19 seems to indicate that there is a positive correlation between the extraction efficiencies or recoveries and CCh / Feed ratios, and such observable positive correlation is confirmed by statistical regression, which shows the p-values for C4, C5 and C6 recoveries are <0.05 at 0.023, 0.0008 and 0.0035, respectively. Conversely, FIG. 20 shows C4, C5 and C6 acids extraction efficiencies or recoveries as a function of CCh / Acidflow ratios. The graph of FIG. 20 does not seem to suggest any correlation between the extraction efficiencies or recoveries and the CCh / Acid flow ratios with this lack of correlation confirmed by statistical regression, which shows the p-values for C4, C5 and C6 recoveries are >0.05 at 0.38, 0.65 and 0.75, respectively.

[0228] Example 7. A series of pilot-scale tests similar to what was performed for Examples 3, 4, 5 and 6 were carried out with a Scheibel™ extraction column operating with the mixer on at 200 rpm as in Example 3, 5 and 6. The aqueous feed solution was a synthetic mix of reagent-grade VFAs, which were neutralized with sodium and potassium hydroxide to form sodium and potassium salts as in Example 5 and 6, but on a VFA basis, this aqueous feed solution ranged from about 60 to 107 g VFA / L. The temperature of the incoming feed solution was at an average of 92.0°F±5.7°F (33.3°C±3.2°C), while the incoming CO2 entering the extraction column was at an average temperature of 85.0°F±3.4°F (29.5°C±1.9°C) and all these pilot-scale tests were run at varying pressures of 900 psig, 950 psig, 1000 psig and 1050 psig. Under these conditions of temperature and pressures, the CO2 was in gaseous state. The CCh / feed ratios, calculated as described for Examples 3, 4, 5 and 6, were kept close to 1 (0.96, 1.06, 0.97 and 1.01 for the tests run at 900, 950, 1000 and 1050 psig, respectively). The CCh / feed ratios were close enough that allows comparison of the effect of pressure on extraction efficiencies or recoveries. FIG. 21 shows C4, C5 and C6 acids extraction efficiencies or recoveries as a function of pressure. The graph of FIG. 21 does not seem to suggest any correlation between extraction efficiencies or recoveries and the pressures tested with this lack of correlation confirmed by statistical regression, which shows the p-values of C4, C5 and C6 recoveries are > 0.05 at 0.75, 0.45 and 0.75, respectively.

[0229] While certain embodiments have been illustrated and described, it should be understood that changes and modifications can be made therein in accordance with ordinary skill in the art without departing from the technology in its broader aspects as defined in the claims.

[0230] The embodiments, illustratively described herein may suitably be practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed herein. Thus, for example, the terms “comprising,” “including,” “containing,” etc. shall be read expansively and without limitation. Additionally, the terms and expressions employed herein have been used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the claimed technology. Additionally, the phrase “consisting essentially of’ will be understood to include those elements specifically recited and those additional elements that do not materially affect the basic and novel characteristics of the claimed technology. The phrase “consisting of’ excludes any element not specified.

[0231] The present disclosure is not to be limited in terms of the particular embodiments described in this application. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and compositions within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is to be understood that this disclosure is not limited to particular methods, reagents, compounds, compositions, or biological systems, which can of course vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0232] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.

[0233] As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a nonlimiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” “greater than,” “less than,” and the like, include the number recited and refer to ranges which can be subsequently broken down into subrangesas discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member.

[0234] All publications, patent applications, issued patents, and other documents referred to in this specification are herein incorporated by reference as if each individual publication, patent application, issued patent, or other document was specifically and individually indicated to be incorporated by reference in its entirety. Definitions that are contained in text incorporated by reference are excluded to the extent that they contradict definitions in this disclosure.

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[0273] Other embodiments are set forth in the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method comprising: extracting fatty acids from a feed solution comprising fatty acid salts by contacting the feed solution with an extractant stream comprising gaseous CO2, liquid CO2, or supercritical CO2 to form a mixture of extracted fatty acids and CO2; separating the CO2 from the mixture to form a separated CO2 stream; recycling at least a portion of the separated CO2 stream to the extractant stream; and contacting at least a portion of the extracted fatty acids with a ketonization catalyst to produce ketones.

2. The method of claim 1, wherein at least a portion of the ketones are contacted with a hydrodeoxygenation catalyst in the presence of hydrogen to produce hydrocarbons.

3. The method of claim 2, wherein the hydrocarbons are n-paraffins.

4. The method of claim 2 or 3, further comprising refining the hydrocarbons to produce a product comprising C8-C16 hydrocarbons.

5. The method of any one of claims 1-4, wherein the extracting is performed at a pressure of300 psig or greater.

6. The method of any one of claims 1-5, wherein the extracting is performed at a pressure of about 800 psig to about 1500 psig.

7. The method of any one of claims 1-6, wherein the extracted fatty acids comprise C2-C9 fatty acids.

8. The method of any one of claims 1-7, wherein the ketones comprise C3-C17 ketones.

9. The method of any one of claims 1-8 further comprising separating a first ketone fraction comprising C7-C17 ketones from the ketones, wherein the at least a portion of the ketones contacted with a hydrodeoxygenation catalyst are the first ketone fraction.

10. The method of any one of claims 1-9, wherein contacting the feed solution with the extractant stream also produces a raffinate stream, and wherein the method furthercomprises recovering CO2 from the raffinate stream and recycling at least a portion of the recovered CO2 to the extractant stream.

11. The method of any one of claims 1 to 8 further comprising separating a first fatty acid fraction from the extracted fatty acids, the first fatty acid fraction comprising C5-C9 fatty acids, wherein the at least a portion of the extracted fatty acids contacted with a ketonization catalyst comprises the first fatty acid fraction.

12. The method of claim 11 further comprising removing heavy impurities from the first fatty acid fraction prior to contacting the first fatty acid fraction with the ketonization catalyst.

13. The method of claim 12, wherein removing the heavy impurities from the first fatty acid fraction comprises using one or more of a distillation column, a falling-film evaporator, a wiped-film evaporator, a thin-film evaporator, a separation vessel, a flash vessel, a filter, a membrane filter, and a guard bed comprising media for removal of nitrogen- and sulfur-containing impurities.

14. The method of any one of claims 1-13, wherein the method is performed continuously.

15. The method of any one of claims 1-14 further comprising: fermenting a biodegradable feedstock to produce a raw fermentation broth comprising the fatty acid salts; clarifying the raw fermentation broth to produce a clarified fermentation broth comprising the fatty acid salts; and providing the clarified fermentation broth as the feed solution.

16. A sustainable aviation fuel comprising C8-C16 hydrocarbons prepared by the method of any one of claims 1-15.

17. A method comprising: extracting fatty acids from a feed solution comprising fatty acid salts by contacting the feed solution with an extractant stream comprising gaseous, liquid, or supercritical CO2 to form a mixture of extracted fatty acids and CO2; separating the CO2 from the mixture to form a separated CO2 stream; recycling at least a portion of the separated CO2 stream to the extractant stream; andcontacting at least a portion of the extracted fatty acids with a hydrogenation catalyst in the presence of hydrogen to produce primary alcohols.

18. The method of claim 17 further comprising contacting at least a portion of the primary alcohols with a dimerization catalyst to produce hydrocarbons.

19. The method of claim 17 or 18, wherein contacting the feed solution with the extractant stream is performed at a pressure of 300 psig or greater.

20. The method of any one of claims 17-19, wherein contacting the feed solution with the extractant stream is performed at a pressure of about 800 psig to about 1500 psig.

21. The method of any one of claims 17-20, wherein the extracted fatty acids comprise C2-C9 fatty acids.

22. The method any one of claims 18-21, wherein the hydrocarbons comprise n-alkenes, iso-alkenes, n-paraffins, iso-paraffins, or combinations of any two or more thereof.

23. The method of either one of claims 18 or 22 further comprising refining the hydrocarbons to produce a product comprising C8-C16 hydrocarbons.

24. A sustainable aviation fuel comprising C8-C16 hydrocarbons prepared according to the method of any one of claims 17-23.

25. The method of claim 24, wherein the pressure is not decreased from extraction to hydrogenation to dimerization and to refining.

26. A method comprising: fermenting a biodegradable feedstock to produce a raw fermentation broth comprising fatty acid salts comprising a carbon chain length of C2-C9; clarifying the raw fermentation broth to produce a clarified fermentation broth comprising the fatty acid salts; contacting at least a portion of the clarified fermentation broth with an extractant comprising gaseous, liquid, or supercritical CO2 to form a first fatty acid fraction comprising fatty acids comprising a carbon chain length of C5-C9, water, and residual CO2 and an aqueous raffinate stream comprisingunextracted fatty acid salts comprising a carbon chain length of C2-C4 and carbonate and bicarbonate salts; recovering the residual CO2 from the first fatty acid fraction and recycling at least a portion of the recovered CO2 to the extractant; converting an MCFA fraction into hydrocarbons comprising n-paraffins and / or isoparaffins, wherein the MCFA fraction comprises at least a portion of C5-C9 fatty acids of the first fatty acid fraction; and refining the hydrocarbons to form refined hydrocarbons suitable for use in a sustainable aviation fuel, marine fuel, naphtha, or diesel fuel.

27. The method of claim 26 further comprising stripping ammonia from the clarified fermentation broth.

28. The method of claim 26 or 27 further comprising concentrating the clarified fermentation broth by removing water.

29. The method of any one of claims 26-28 further comprising stripping ammonia from the removed water, and recovering the stripped ammonia with an acid to produce ammonium salts.

30. The method of any one of claims 26-29 further comprising separating fatty acids having a carbon chain length of C2-C4 from the first fatty acid fraction.

31. The method of any one of claims 26-30 further comprising removing other heavy compounds or impurities from the first fatty acid fraction.

32. The method of any one of claims 26-31, wherein the aqueous raffinate stream is recycled to the fermentation.

33. The method of any one of claims 26-32, wherein fermenting the biodegradable feedstock and neutralizing the fatty acids produced in the fermentation also produces a fermentation gas comprising CO2, hydrogen, and other gases, and wherein the fermentation gas is purified to produce a purified fermentation CO2 stream and wherein at least a portion of the extractant comprises the purified fermentation CO2 stream.I l l34. The method of any one of claims 25-33, wherein converting the MCFA fraction into hydrocarbons includes: contacting the MCFA fraction with a ketonization catalyst to produce a ketonization product comprising C9-C17 ketones; and contacting at least a portion of the ketonization product with a hydrodeoxygenation catalyst in the presence of hydrogen to produce hydrocarbons comprising C9-C17 n-paraffins; wherein the refined hydrocarbons comprise hydrocarbons suitable for use in a sustainable aviation fuel, marine fuel, naphtha, diesel fuel, or combinations of any two or more thereof.

36. The method of claim 35, wherein contacting the MCFA fraction with a ketonization catalyst also produces a ketonization gas comprising CO2, and wherein the ketonization gas is purified to produce a purified ketonization CO2, and wherein the extractant comprises the purified ketonization CO2.

36. The method of claim 35, wherein: fermenting the biodegradable feedstock also produces a fermentation gas comprising CO2, hydrogen, and other gases, and the fermentation gas is purified to produce a purified fermentation CO2 stream; the fermentation gas and the ketonization gas are purified in the same purification system to produce a combined purified CO2; and the extractant comprises the combined purified CO2.

37. The method of claim 36, wherein excess purified fermentation CO2 and purified ketonization CO2 not used as extractant is stored or sequestered underground or utilized for other purposes to decrease the carbon intensity of the process.

38. The method of claim 36 or 37, wherein contacting the MCFA fraction with a ketonization catalyst to produce a ketonization product also comprises introducing a sweep or carrier gas together with the MCFA fraction.

39. The method of claim 38, wherein the sweep or carrier gas comprises CO2 or a combination of CO2 and hydrogen obtained from the fermentation gas.

40. The method of any one of claims 25-39, wherein converting the MCFA fraction into hydrocarbons includes: contacting the MCFA fraction with a hydrogenation catalyst in the presence of hydrogen to produce primary alcohols; and contacting at least a portion of the primary alcohols with a dimerization or oligomerization catalyst to produce n-alkenes, iso-alkenes, n-paraffins, isoparaffins, or combinations of any two or more thereof and with a hydrotreating catalyst to hydrotreat the n-alkenes or iso-alkenes into n- paraffins or iso-paraffins, wherein the refined hydrocarbons comprise hydrocarbons suitable for use in a sustainable aviation fuel, marine fuel, naphtha, diesel fuel, base oil, or combinations of any two or more thereof.

41. The method of any one of claims 25-40, wherein the contacting at least a portion of the clarified fermentation broth with the extractant is performed in a hollow fiber membrane extractor.

42. The method of any one of claims 25-41, wherein refining the hydrocarbons includes one or more of: isomerization or hydroisomerization of the hydrocarbons in the presence of hydrogen, cyclization of the n-paraffins or iso-paraffins; aromatization of the n-paraffins or iso-paraffins; or and fractionation of the hydrocarbons using distillation to achieve desired hydrocarbon properties.

43. The method of any one of claims 40-42, wherein the pressure is not decreased from extraction to hydrogenation to dimerization or oligomerization to hydrotreating and to further refining.

44. A method of recovering organic acids from an aqueous solution containing organic acids salts using carbon dioxide (CO2) as a gas, wherein the CO2 both acidifies the organic acid salts into corresponding organic acids and captures the organic acids to recover them from the aqueous solution.

45. The method of claim 44, wherein the organic acids salts are produced from fermentation of organic feedstocks.

46. The method of claim 44 or 45, wherein the organic acid salts are fatty acid salts and the corresponding organic acids are corresponding fatty acids.

47. The method of claim 46, wherein the fatty acid salts and fatty acids comprise a carbon chain length of C2-C9 or of C5-C9.

48. The method of any one of claims 44-47, wherein the recovery of the organic acids occurs in a contactor unit.

49. The method of claim 48, wherein the contactor unit is a contactor column or an extraction column.

50. The method of claim 48, wherein the contactor unit is a packed column containing structured packing or random packing, a mechanically agitated column separated in stages, a bubble column, or a foam fractionation column.

51. The method of any one of claims 44-50, wherein an operating pressure of the contactor unit is 300 psig or greater.

52. The method of any one of claims 44-51, wherein an operating pressure of the contactor unit is 800 psig to about 1500 psig.53 . The method of any one of claims 48-50, wherein the aqueous solution containing the organic acid salts enters at a top of the contactor unit, while the CO2 enters at a bottom of the contactor unit.

54. The method of claim 53, wherein excess CO2 is captured at the top of the contactor unit, is recompressed, and is recycled to the bottom of the contactor unit.

55. The method of claim 54, wherein the excess CO2 is recompressed using a blower, a fan, a compressor, an eductor, a venturi, or a combination of any two or more thereof.

56. The method of claim 54 or 55, wherein the CO2 separates from the recovered organic acids in the contactor unit or in a separate knockout separator.

57. The method of any one of claims 54-56, further comprising separating dissolved CO2 from the recovered organic acids by a stripper or a distillation column.

58. The method of claim 57, wherein the CO2 separated from the recovered organic acids is recompressed and recycled to the contactor unit.

59. The method of claim 57 or 58, wherein the separation of the dissolved CO2 is performed at a pressure that is greater than atmospheric pressure.

60. The method of claim 50, wherein: the contactor unit is a bubble or foam fractionation column, and wherein the contactor unit comprises at least one of a sparger, a distributor, an eductor, and a venturi used to deliver the CO2 at a bottom of the column; or the contactor unit is a bubble column and comprises perforated spacers positioned along a length of the bubble column, the spacers optionally supporting heating or cooling tubing along the length of the column.

61. A method comprising: feeding an aqueous solution comprising organic solutes to a foam fractionation column; and providing a carbon dioxide gas feed to the foam fractionation column to produce a foam within the foam fractionation column; wherein the carbon dioxide both acidifies and captures the organic solute as it is carried over with the foam to a foam separation and recovery section or vessel.

62. The method of claim 61, wherein the foam fractionation column is operated at an operating pressure greater than atmospheric pressure.

63. The method of claim 61 or 62, further comprising: separating carbon dioxide from the foam in the foam separation and recovery section or vessel; and recirculating the separated carbon dioxide; wherein the foam is produced using an eductor or a venturi configured to entrain the separated carbon dioxide in the aqueous solution.

64. A method of producing hydrocarbons, the method comprising: co-processing ketones produced from the ketonization of fatty acids produced and recovered from a fermentation process with long-chain lipidic feedstocks in ahydroprocessed esters and fatty acids process wherein the co-processing includes: hydrotreating or hydrodeoxygenating the ketones and the long-chain lipidic feedstocks in the same step; separating n-paraffins comprising carbon chain lengths of 16 carbons or smaller; allowing a long-chain fraction comprising n-paraffins having carbon chain lengths longer than 16 carbons to undergo mild hydrocracking to produce a hydrocracked fraction; recombining the n-paraffins comprising carbon chain lengths of 16 carbons or smaller with the hydrocracked fraction; optionally isomerizing or hydroisomerizing the combined fraction; optionally fractionating the resulting hydrocarbons by distillation; and producing a hydrocarbon product suitable for sustainable aviation fuel.

65. A method of producing a hydrocarbon product suitable for use as a sustainable aviation fuel, the method comprising: co-processing ketones produced from the ketonization of fatty acids produced and recovered from a fermentation process with a long-chain lipidic feedstock; wherein the co-processing includes: hydrotreating or hydrodeoxygenating the ketones and the long-chain lipidic feedstock in the same step to produce n-paraffins; separating the n-paraffins into a short-chain fraction comprising n-paraffins having carbon chain lengths of 16 carbons or smaller and a long-chain fraction comprising n-paraffins having carbon chain lengths larger than 16 carbons; performing mild hydrocracking on the long-chain fraction to produce a hydrocracked fraction; combining the short-chain fraction with the hydrocracked fraction to form a combined fraction; optionally isomerizing or hydroisomerizing the combined fraction to produce an isomerized fraction; and optionally fractionating at least one of the combined fraction and the isomerized fraction by distillation.

66. A method of producing hydrocarbons, the method comprising:co-processing a product from the dimerization of primary alcohols produced from the hydrogenation of fatty acids produced and recovered from a fermentation process with long-chain lipidic feedstocks in a conventional hydroprocessed esters and fatty acids process wherein the co-processing includes: hydrotreating or hydrodeoxygenating the dimerized product and the long-chain lipidic feedstocks in the same step; separating the n-paraffins and iso-paraffins comprising carbon chain lengths of 16 carbons or smaller; allowing a long-chain fraction comprising n-paraffins longer than 16 carbons to undergo mild hydrocracking to produce a hydrocracked fraction; recombining the n-paraffins and iso-paraffins 16 carbons of smaller with the hydrocracked fraction; optionally isomerizing or hydroisomerizing the combined fraction; optionally fractionating the resulting hydrocarbons by distillation; and producing a hydrocarbon product suitable for sustainable aviation fuel.

67. A method of producing a hydrocarbon product suitable for use as a sustainable aviation fuel, the method comprising: co-processing a product from a dimerization of primary alcohols produced from a hydrogenation of fatty acids produced and recovered from a fermentation process with a long-chain lipidic feedstock, wherein the co-processing includes: hydrotreating or hydrodeoxygenating the dimerized product and the long- chain lipidic feedstock in the same step to produce a paraffinic product comprising n-paraffins and iso-paraffins; separating the paraffinic product into a short-chain fraction and a long-chain fraction, wherein the short-chain fraction comprises n-paraffins and isoparaffins having carbon chain lengths of 16 carbons or smaller and the long- chain fraction comprises n-paraffins and iso-paraffins having chain lengths of more than 16 carbons; performing mild hydrocracking on the long-chain fraction to produce a hydrocracked fraction; combining the short-chain fraction with the hydrocracked fraction into a combined fraction;optionally isomerizing or hydroisomerizing the combined fraction to produce an isomerized fraction; and optionally fractionating the at least one of the combined fraction and the isomerized fraction by distillation.

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