High-density paraffinic kerosene compositions and methods

Abstract

A composition and method for making a synthetic paraffinic composition with at least 35 wt % C17 and higher carbon number paraffins having an iso / normal ratio between 100 and 500 is described.

Description

Atty. Docket No. T-12678-WO01HIGH-DENSITY PARAFFINIC KEROSENE COMPOSITIONS AND METHODSCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application No.63 / 723,380, filed November 21, 2024, which is incorporated by reference herein in its entirety.FIELD

[0002] The present technology relates generally to hydrocarbon fuels comprising renewable content. More particularly, the technology relates to production of jet fuel blend components from renewable feedstock.SUMMARY

[0003] This invention describes Synthetic Paraffinic Kerosene (SPK) compositions suitable for use as aviation turbine fuels (jet fuel). Unlike other SPK compositions disclosed in the prior art, the compositions of the present technology meet the low freezing point and distillation end point specifications of jet fuel despite inclusion of a high percentage of C17 and higher carbon number paraffins. Due to the presence of these higher carbon number paraffins, the SPK is characterized by relatively high mass density and volumetric energy density. In embodiments, the SPK composition is at least 35 wt % C17 and higher carbon number paraffins having an iso / normal ratio between 100 and 500.

[0004] Methods for the production of the SPK composition are described. In one embodiment, a lipid is (1) hydrotreated to provide a lipid-derived paraffin stream, (2) the lipidderived paraffin stream is subjected to hydroisomerization in a hydroisomerization reactor at conditions that produce a highly isomerized hydroizomerizate, and (3) the hydroisomerizate is stripped of light hydrocarbons to yield the SPK composition. In embodiments, the SPK is subjected to Organic Solvent Nanofiltration (OSN) or similar membrane separation to remove C19 and higher carbon number components from the SPK.Atty. Docket No. T-12678-WO01

[0005] In another embodiment, the hydroisomerizate is fractionated into a light hydrocarbon fraction, the SPK composition, and a bottoms fraction. In this embodiment, at least 90 vol % of the bottoms fraction is recycled to the hydroisomerization reactor at hydroisomerization conditions that prevent buildup of heavy components in the recycle stream.Atty. Docket No. T-12678-WO01BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG 1 is a schematic of the processing of a lipid feedstock to a paraffinic kerosene composition.

[0007] FIG 2 is a schematic of an alternative process stream for generating a paraffinic kerosene composition from a lipid feedstock.

[0008] FIG 3 is a graph of a composition of hydtrotreated FOG for Examples 2 and 3 experiments.

[0009] FIG 4 is a graph of a composition of hydtrotreated canola oil for Examples 2 and 3 experiments; and

[0010] FIG 5 is a graph of the GCxGC analysis of feed, permeate, and retentate, the % Cl 9 paraffin reduction at each test condition was calculated and plotted as bar graph Example 4.BACKGROUND

[0011] SPK compositions for use as jet fuel blendstock have been disclosed in the prior art. Such compositions may be produced by a number of processes including Fischer-Tropsch (FT), Alcohol -to- Jet (ATJ), and Hydroprocessing of Esters / Fatty Acids (HEFA). Due to absence of aromatic hydrocarbons, SPK jet fuels are associated with better thermal stability and lower particulate exhaust emissions than petroleum kerosene jet fuels. A disadvantage of SPK jet fuels is their lower densities which translates to lower volumetric energy content.

[0012] The specifications for commercial jet fuel are given by ASTM D1655, while synthetic hydrocarbons for blending with jet fuel (including FT, ATJ, and HEFA) are defined in ASTM D7566. The final boiling point for jet fuel is specified as 300 C (572 F) maximum.

[0013] Table I provides a list of different n-paraffins and their corresponding properties. As observed from the table, the 300 C max boiling point translates to a max carbon number between C16 and C17. Not surprisingly, the SPK jet fuel blendstock of the prior art are mainly in the C9-C16 carbon number range.Atty. Docket No. T-12678-WO01

[0014] In case of HEFA production, since the prevalent fatty acid chain length in most lipids is C18, production of a C9-C16 SPK has meant that the hydrocarbon stream from lipid hydrotreating has to either be hydrocracked during the isomerization step and / or a heavy (C16+) fraction separated as a bottoms diesel coproduct. In either case, HEFA production according to method of prior art corresponds to lower yields for the desired renewable jet fuel blendstock.Table I. Boiling Point and Lower Heating Value for C9-C 18 n-Paraffins Volumetric Heat Paraffin Carbon Boiling Point Density at 20 C Heat of CombustionName of Combustion No. (°C) (kg / L) (kJ / kg)(a)(kJ / L) C9 Nonane 151 0.718 44.324 31,825 CIO Decane 174 0.730 44,241 32,296 Cll Undecane 196 0.740 44,171 32.686 C12 Dodecane 216 0.749 44,122 33.047 C13 Tridecane 235 0.756 44,066 33.314 C14 Tetradecane 253 0.763 44,024 33.590 C15 Pentadecane 271 0.768 43,987 33.782 C16 Hexadecane 287 0.773 43,957 33.979 C17 Heptadecane 302 0.777 43,929 34.133 C18 Octadecane 317 0.777 43,903 34,113Notes:(a) Lower heat of combustion values from R. N. Robinson, Chemical Engineering Reference Manual, Belmont. CA: Professional Publications, Inc., 1996; Chapter 4, Appendix I.

[0015] Table I also provides the lower heating values (i.e., heat of combustion for generating water vapor and CO2 gas) for C9-C18 paraffins. As observed, the paraffin volumetric energy content given in the last column of the table increases with carbon number. As such, despite boiling point limitation, there is a desire to include more C17 and higher carbon number paraffins in SPK. As elaborated in the following paragraphs, the prior art does not offer a solution to this problem.

[0016] US Patent 7,846,323 describes a method for producing a paraffinic kerosene from renewable feedstock comprising triglycerides and free fatty acids. The renewable feedstock is hydrotreated to produce an n-paraffinic fraction that is then hydroisomerized to an isoparaffinic fraction and a heavy fraction. The heavy fraction is recycled to the hydroisomerization step.Atty. Docket No. T-12678-WO01Specifications and examples show that the isoparaffinic fraction has a carbon number range of C8-C16 with an iso / normal ratio of 6.6.

[0017] US Patent Publication 2023 / 0416619 describes a similar process without separation of the heavy fraction. The isomerization / dewaxing operating conditions are defined by a severity index tied to temperature and space velocity. The working examples for the isomerization / dewaxing step use a model feed made of C15-C18 paraffins instead of an actual product derived from hydrotreating of lipids or fatty acid / esters. No information about the carbon number distribution or iso / normal ratio is provided for the paraffinic kerosene / jet fuel product is provided.

[0018] US Patent 11,859,143 discloses isomerized paraffin compositions for use as jet fuel blendstock. The average carbon number is said to be between 14.3 and 15.1. A comparative example is provided with a paraffinic composition having an average carbon number of 15.6. This higher average carbon number composition is shown to have relatively high freezing point and a final boiling point that exceeds the 300 C specification limit. No information about the iso / normal ratio of the isomerized paraffins is provided.

[0019] There thus remains an unmet need for higher density SPK compositions that conform to the 300 C distillation end point specification and for methods of manufacturing same. In particular, the remains a need for higher yield HEFA production processes from lipids rich in Cl 8 and longer fatty acids.DETAILED DESCRIPTION

[0020] We have discovered that higher density paraffinic kerosene compositions having a final boiling point less than 300 C can be produced by hydroisomerization of n-paraffins while maintaining at least 40 wt % C17 and higher carbon number paraffins in the paraffinic kerosene. In such high-density paraffinic kerosene compositions, the C17 and C18 paraffins have an iso / normal ratio between 100 and 500. Embodiments that are exemplary but not limited to high density include 0.770 g / ml or higher, preferably 0.770 - 0.777 g / ml (or kg / L).

[0021] 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 broaderAtty. Docket No. T-12678-WO01aspects 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).

[0022] As used herein, “about” will mean up to plus or minus 10% of the particular term. 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 nonclaimed element as essential.Definitions

[0023] As used herein, “alkyl” groups include straight chain and branched alkyl groups. Examples of straight chain alkyl groups include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, and n-octyl groups. Examples of branched alkyl groups include, but are not limited to, isopropyl, sec-butyl, t-butyl, neopentyl, and isopentyl groups. It will be understood that the phrase “C / -C / alkyl,” such as C1-C4 alkyl, means an alkyl group with a carbon number falling in the range from i to j.

[0024] The term “aromatics” as used herein is synonymous with "aromates" and means both cyclic aromatic hydrocarbons that do not contain heteroatoms as well as heterocyclic aromatic compounds. The term includes monocyclic, bicyclic and polycyclic ring systems. The term also includes aromatic species with alkyl groups and cycloalkyl groups. Thus, aromatics include, but are not limited to, benzene, azulene, heptalene, phenylbenzene, indacene, fluorene, phenanthrene, triphenylene, pyrene, naphthacene, chrysene, anthracene, indene, indane, pentalene, and naphthalene, as well as alkyl and cycloalkyl substituted variants of theseAtty. Docket No. T-12678-WO01compounds. In some embodiments, aromatic species contains 6-14 carbons, and in others from 6 to 12 or even 6-10 carbon atoms in the ring portions of the groups. The phrase includes groups containing fused rings, such as fused aromatic-aliphatic ring systems (e.g., indane, tetrahydronaphthene, and the like).

[0025] “Oxygenates” or an “oxygenated hydrocarbon” as used herein means carbon-containing compounds containing at least one covalent bond to oxygen. Examples of functional groups encompassed by the term include, but are not limited to, carboxylic acids / esters, carboxylates, acid anhydrides, aldehydes, esters, ethers, ketones, and alcohols. Oxygenates may also be oxygen containing variants of aromatics, cycloparaffins, and paraffins as described herein. Fatty acids / glycerides are naturally occurring carboxylic acids / esters that define lipids.

[0026] The term “paraffins” as used herein means non-cyclic, branched or unbranched alkanes. An unbranched paraffin is an n-paraffin; a branched paraffin is an iso-paraffin.“Cycloparaffins” are cyclic, branched or unbranched alkanes.

[0027] The term “paraffinic” as used herein means both paraffins and cycloparaffins as defined above as well as predominantly hydrocarbon chains possessing regions that are alkane, either branched or unbranched.

[0028] The term “olefin” as used herein means non-cyclic, branched or unbranched alkenes. The term “olefinic” as used herein means both mono- or di-unsated (i.e., one or two double bonds) hydrocarbons, either cyclic, branched or unbranched.

[0029] Hydroprocessing as used herein describes the various types of catalytic reactions that occur in the presence of hydrogen without limitation. Examples of the most common hydroprocessing reactions include, but are not limited to, hydrogenation, hydrodesulfurization (HDS), hydrodenitrogenation (HDN), hydrotreating (HT), hydrocracking (HC), aromatic saturation or hydrodearomatization (HD A), hydrodeoxygenation (HDO), decarboxylation (DCO), hydroisomerization (HI), hydrodewaxing (HDW), hydrodemetallization (HDM), decarbonylation, methanation, and reforming. Depending upon the type of catalyst, reactor configuration, reactor conditions, and feedstock composition, multiple reactions can take place that range from purely thermal (i.e., do not require catalyst) to catalytic. In the case ofAtty. Docket No. T-12678-WO01describing the main function of a particular hydroprocessing unit, for example an HDO reaction system, it is understood that the HDO reaction is merely one of the predominant reactions that are taking place and that other reactions may also take place.

[0030] Decarboxylation (DCO) is understood to mean hydroprocessing of an organic molecule such that a carboxyl group is removed from the organic molecule to produce CO2, as well as decarbonylation which results in the formation of CO.

[0031] Hydrotreating (HT) involves the removal of elements from groups Illa, Va, Via, and / or Vila of the Periodic Table from organic compounds. Hydrotreating may also include hydrodemetallization (HDM) reactions. Hydrotreating thus involves removal of heteroatoms such as oxygen, nitrogen, sulfur, and combinations of any two more thereof through hydroprocessing. For example, hydrodeoxygenation (HDO) is understood to mean removal of oxygen by a catalytic hydroprocessing reaction to produce water as a by-product; similarly, hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) describe the respective removal of the indicated elements through hydroprocessing.

[0032] Hydrogenation involves the addition of hydrogen to an organic molecule without breaking the molecule into subunits. Addition of hydrogen to a carbon-carbon or carbon-oxygen double bond to produce single bonds are two nonlimiting examples of hydrogenation. Partial hydrogenation and selective hydrogenation are terms used to refer to hydrogenation reactions that result in partial saturation of an unsaturated feedstock. For example, vegetable oils with a high percentage of polyunsaturated fatty acids (e.g., linoleic acid) may undergo partial hydrogenation to provide a hydroprocessed product wherein the polyunsaturated fatty acids are converted to mono-unsaturated fatty acids (e.g., oleic acid) without increasing the percentage of undesired saturated fatty acids (e.g., stearic acid). While hydrogenation is distinct from hydrotreatment, hydroisomerization, and hydrocracking, hydrogenation may occur amidst these other reactions.

[0033] Hydrocracking (HC) is understood to mean the breaking of a molecule’ s carboncarbon bond to form at least two molecules in the presence of hydrogen. Such reactions typically undergo subsequent hydrogenation of the resulting double bond.Atty. Docket No. T-12678-WO01

[0034] Hydroisomerization (HI) is defined as the skeletal rearrangement of carbon-carbon bonds in the presence of hydrogen to form an isomer. Hydrocracking is a competing reaction for most HI catalytic reactions, and it is understood that the HC reaction pathway, as a minor reaction, is included in the use of the term HI. Hydrodewaxing (HDW) is a specific form of hydrocracking and hydroisomerization designed to improve the low temperature characteristics of a hydrocarbon fluid.

[0035] It will be understood that if a composition is stated to include “C / -C / hydrocarbons,” such as C7-C12 n-paraffins, this means the composition includes one or more paraffins with a carbon number falling in the range from i to j.

[0036] A “middle distillate” in general refers to a petroleum fraction in the range of about 200° F (93° C) to about 800° F (427° C). This includes kerosene (about 200-520° F), diesel and light gasoil (about 400 to 650° F), and heavy gasoil (about 610-800° F).

[0037] A “lipid” as used herein refers to fats, oils, and greases. Lipids comprise of saturated and unsaturated fatty acids in the C8-C24 range, wherein the fatty acids can be in the form of esters of glycerin (i.e., as mono-, di-, and triglycerides), fatty acid esters, or as free fatty acids (FFA).

[0038] It is to be understood that a “volume percent” or “vol.%” of a component in a composition or a volume ratio of different components in a composition is determined at room temperature (about 23° C) based on the initial volume of each individual component, not the final volume of combined components.

[0039] Iso / normal ratio as used herein refers to the ratio of isoparaffins to normal paraffin. For example, if a paraffin composition has 30 wt % iso-hexadecane (i.e., 2-methyl pentadecane, 3-methyl petadecane, 2,3-dimethyl tetradecane, etc.) and 3 wt % n-hexadecane, it has a C16 iso / normal ratio of 10. The concentration of the iso- and n-paraffins of different carbon numbers is measured by GC or GCxGC techniques.

[0040] Distillation end point (EP) or final boiling point (FBP) is defined as the temperature at which a fuel composition fully evaporates at atmospheric pressure. The value is measured andAtty. Docket No. T-12678-WO01reported according to ASTM standard test method D86. According to the test method, the distillation residue has to be 1.5% maximum for reporting the corresponding end point value.A First Embodiment of the Present Technology

[0041] Referring to Figure 1, a lipid feedstock 101 is directed to a surge drum 10 to provide the high-pressure pump feed 102 for hydroprocessing. Exemplary lipid feedstock includes, but are not limited to, an animal fat, animal oil, microbial oil, plant fat, plant oil, vegetable fat, vegetable oil, grease, or a mixture of any two or more thereof. Plant and / or vegetable oils and / or microbial oils include, but are not limited to, com oil, inedible corn oil, babassu oil, carinata oil, soybean oil, canola oil, coconut oil, rapeseed oil, tall oil, tall oil fatty acid, palm oil, palm oil fatty acid distillate, jatropha oil, pennycress oil, palm kernel oil, sunflower oil, castor oil, camelina oil, archaeal oil, bacterial oil, fungal oil, protozoal oil, algal oil, seaweed oil, oils from halophiles, and mixtures of any two or more thereof. These may be classified as crude, degummed, and RBD (refined, bleached, and deodorized) grade, depending on level of pretreatment and residual phosphorus and metals content. However, any of these grades may be used in the present technology. Animal fats and / or oils as used above includes, but is not limited to, inedible tallow, edible tallow, technical tallow, floatation tallow, lard, poultry fat, poultry oils, fish fat, fish oils, and mixtures of any two or more thereof. Greases may include, but are not limited to, yellow grease, brown grease, waste vegetable oils, restaurant greases, trap grease from municipalities such as water treatment facilities, and spent oils from industrial packaged food operations, and mixtures of any two or more thereof. Depending on level of pretreatment, such biorenewable lipid feedstock may contain between about 1 wppm and about 100 wppm phosphorus, and between about 1 wppm and about 100 wppm total metals (mainly sodium, potassium, magnesium, calcium, iron, and copper). The lipid may also contain up to 20 wt % free fatty acid (calculated from Total Acid Number or TAN according to various standard test methods such as AOCS Ca 5a-40). The lipid may also contain up to 2 wt % unsaponifiable matter as measured by standard test methods such as AOCS Ca 6a-40. Examples of compounds that are considered unsaponifiable include sterols and tocopherols.

[0042] Thus, the lipid feedstock of any embodiment herein may include corn oil, inedible corn oil, babassu oil, carinata oil, soybean oil, canola oil, coconut oil, rapeseed oil, tall oil, tall oilAtty. Docket No. T-12678-WO01fatty acid, palm oil, palm oil fatty acid distillate, jatropha oil, palm kernel oil, sunflower oil, castor oil, camelina oil, archaeal oil, bacterial oil, fungal oil, protozoal oil, pongamia oil, algal oil, seaweed oil, oils from halophiles, rendered fats, inedible tallow, edible tallow, technical tallow, floatation tallow, lard, poultry fat, poultry oils, fish fat, fish oils, frying oils, yellow grease, brown grease, waste vegetable oils, restaurant greases, trap grease from municipalities such as water treatment facilities, and spent oils from industrial packaged food operations, or a mixture of any two or more thereof.

[0043] The surge drum 10 provides a pump suction liquid 102 for pressurization and transfer via pump 12. The pressurized feedstock 103 is combined with heated diluent stream 107. The heated diluent stream 107 is a two-phase fluid comprising hydrogen and the hydrocarbon liquid from the hydrotreater (to be described later herein). A hydrocarbon diluted feedstock 108 enters hydrotreater reactor 20 at a temperature between 500 and 650 F. The hydrotreater reactor 20 is maintained under a pressure between 600 and 2500 psig, such that a hydrogen partial of at least 500 psia is maintained therein. The hydrotreater reactor 20 includes at least two different sulfided base metal catalysts of different activities. In a preferred embodiment, the hydrotreater reactor 20 includes a first catalyst bed 22A comprising a lower activity sulfided Mo catalyst, and a second bed 22B comprising a higher activity sulfided NiMo catalyst. To maintain sulfided catalyst activity despite relatively low (<50 ppm) organic sulfur content in most lipid feedstock, the lipid is preferably additized with an organosulfur compound such as dimethyl disulfide at 100-10,000 wppm sulfur

[0044] At the hydrotreater operating conditions, HDO, DCO, HDN, and hydrogenation reactions transform the lipid feedstock 101 into a paraffin composition comprising mainly of C15-C18 n-paraffins. Depending on the lipid type / fatty acid profile and reactor conditions / catalysts, shorter and longer paraffins and other hydrocarbons may also be produced. Depending on the extent of the DCO reactions, between about 10% and 50% of the naturally occurring even carbon-number fatty acids in the lipid feedstock are converted to odd carbon-number paraffins. Specifically, the DCO pathway converts C18 fatty acids (i.e., stearic, oleic, and linoleic acids) to heptadecane whereas direct HDO converts Cl 8 fatty acids to octadecane. Within the described range of temperatures, pressures, catalyst types, and sulfur addition, the DCO deoxygenation pathway is promoted by higher temperatures, lower pressure, high sulfurAtty. Docket No. T-12678-WO01addition, and use of NiMo catalyst. On the other hand, direct HDO is promoted by lower temperatures, higher pressures, lower sulfur addition, and Mo catalysts.

[0045] Hydrogenation and HDO are exothermic reactions. In order to mitigate adiabatic temperature-rise across the fixed-bed reactor system, a hydrogen quench 104 is injected between the two catalyst beds is a gas / liquid mixing assembly 23. The hydrogen quench 104 is used to ensure that the hot hydrotreater effluent 110 is maintained at a temperature between 620 and 750° F, preferably between 650 and 700° F. The hot reactor effluent 110 is cooled through a first feed-effluent exchanger 30 and a cooler 32 to provide a cooled hydrotreater effluent 112. The cooled hydrotreater effluent 112 is a two-phase fluid consisting of a gas / vapor and liquid with a temperature of 360-460° F.

[0046] The cooled hydrotreater effluent 112 enters a hot separator 34 where a gas / vapor 124 is separated from a hydrotreater liquid product 113. The hydrotreater liquid product includes the aforementioned C15-C18 n-paraffins. This hydrotreater liquid product is divided between a product recycle 115 and a HI feed 114. The product recycle 115 is transferred through pump 36 to provide a pumped product recycle 126 before it is combined with hydrogen 133 to provide a hydrogen-containing product recycle 118. This two-phase recycle stream is heated through the feed-effluent exchanger 30 and a heater 46 to provide the heated diluent stream 107 and the hydrocarbon diluted feedstock 108.

[0047] The ratio of pumped recycle product 126 to pressurized lipid feedstock 103 is between 2:1 to 5:1, preferably between 2.5:1 and 4:1. The ratio of hydrogen 133 to lipid feedstock 103 is between 5,000 SCF / Bbl to 20,000 SCF / Bbl. The pressurized feedstock 103 is introduced to the reactor system at a liquid hourly space velocity (LHSV) between 0.3 and 6.0 h-1(vol / h of feedstock 103 per vol of total hydrotreater catalyst).

[0048] The heater 46 is preferably a shell and tube exchanger with the reactor feed flowing through the tubes and a heat transfer fluid flowing through the shell side. Although a shell and tube heat exchanger is described for the first feed-effluent exchanger 30 and heater 46 in this embodiment of the process, those skilled in the art recognize that other types of heat exchanger or heating methods may be employed to meet the desired heated reactor feed temperatures. For example, in a preferred embodiment the pumped product recycle stream 126 may be heated in aAtty. Docket No. T-12678-WO01fired heater (not shown) to a temperature that when combined with pressurized feedstock 103 achieves the heated reactor feed temperatures described herein.

[0049] Returning to FIG. 1, the gas / vapor phase 124 is combined with a wash water 125 before entering a condenser 40 wherein hydrocarbon vapor and water is condensed to provide a three-phase condenser product 210. The condenser product 210 is directed to three-phase separator 42 where an aqueous phase 128, a light hydrocarbon product 128A, and a gas 129 exit. In embodiments, the separator 42 also serves as a gas scrubber where the gas 129 is contacted with a scrubbing solvent 129 to remove gas phase byproducts of the DCO and HDN reactions such as CO2 and NH3.

[0050] The aqueous phase 128, mainly consisting of H2S, CO2, and NH3 dissolved in water, is directed to a sour water stripper (not shown), while the light hydrocarbon product 128A (mainly comprising of C16 and lighter paraffins) is directed to HI Feed Stripper 50 described later herein.

[0051] The gas phase 129 is split into a bleed gas 129A and a recycle gas 232. The purpose of the bleed is to mitigate buildup of propane, CO, and other non-condensed gas phase byproducts from building up in the recycle hydrogen treat gas. The ratio of bleed stream 129A to recycle stream 232 depends in part on the DCO reactions and target hydrogen content for the treat gas.

[0052] In preferred embodiments, a bleed gas 129A is directed to a sponge oil absorber for recovery of lipid hydrotreating coproduct propane from the gas 129. The recycle gas 232 comprising mainly of hydrogen is combined with makeup hydrogen 233 (compressed through makeup compressor 44 A) in recycle compressor 44B to provide a recycle treat gas 235 with at least 80 mol % hydrogen. The recycle treat gas may be further compressed in compressor stage 44C before to provide the hydrogen for the hydrotreater 20.

[0053] The HI feed 114 is combined with light hydrocarbon fraction 128A in HI feed stripper 50. The HI feed stripper 50 is a column that provides counter-current contacting between a stripping gas 121 and the HI feed 114 / light hydrocarbons 128A. The dissolved gas phase hydroprocessing byproducts such as ammonia, hydrogen sulfide, and water are thus removed from the hydrotreated lipid product. The stripping gas 121 may be nitrogen, steam, hydrogen, orAtty. Docket No. T-12678-WO01natural gas. The stripper column 50 operates at conditions of temperature and pressure to promote removal of ammonia, hydrogen sulfide, and water such that a stripped hydrocarbon product 122 has a total nitrogen content of 2 ppm or less. In embodiments, the stripper column operates at a temperature range between 240 and 400 F under a pressure between 50 and 1000 psig. In embodiments, the stripped hydrocarbon composition is a C11-C24 range paraffinic hydrocarbon with at least 90 wt % n-paraffins, an acid number of 0.10 mg KOH / g or less, a water content of 100 wppm or less, and a sulfur content of 2 wppm or less.

[0054] The stripped hydrocarbon 122 is transferred though a hydroisomerization (HI) reactor system via pump 60. A pumped HI fresh feed 211 is combined with HI recycle 236 to provide a combined HI feed 238. The HI feed 238 is heated through a second feed-effluent exchanger 62 and combined with hydrogen 236 A to provide a hydrogen containing HI feed 213. The hydrogen-containing HI feed 213 is heated in HI feed heater 64 to provide a heated HI feed 214.

[0055] The ratio of hydrogen 236A to HI feed 238 is between 2,000 SCF / Bbl and 8,000 SCF / Bbl. The temperature HI feed is between 640 and 680 F. The HI reactor 70 operates at a pressure between 300 psig and 1400 psig, preferably between 600 and 1200 psig. In embodiments, the HI reactor 70 comprises of a plurality of catalyst beds 72, with hydrogen quench 236B between the beds. The hydrogen quench 236 B is used to ensure a relatively low total temperature rise across the reactor, for mitigation of hydrocracking, and for controlling target Catalyst Average Temperature (CAT). The CAT of each bed is given by Eq 1.CAT = [ (avg Inlet T) + (avg outlet T) ] / 2 (1)For a reactor with n beds, the CAT for the reactor is thus given by Eq 2.CAT = [(vol Bed 1)( CAT Bed 1) + (vol Bed 2)(CAT Bed 2) + (vol Bed M)(CAT Bed w)] / (vol Bed 1 + vol Bed 2 + vol Bed n) (2)

[0056] Each bed volume contains a bifunctional catalyst of the type described in US Patent 11,987,757. These catalysts have a hydrogenation-dehydrogenation functionality provided by platinum or platinum and palladium, and an acid functionality provided by a zeolite The CAT for HI reactor 70 is maintained at a temperature between 640° F and 680° F. For example, theAtty. Docket No. T-12678-WO01CAT may be 642 F, 644 F, 646 F, 648 F, 650 F, 652 F, 654 F, 656 F, 658 F, 660 F, 662 F, 664 F, 666 F, 668 F, 670 F, 672 F, 674 F, 676 F, 678 F, or in a range between any two of these values

[0057] We have discovered that during recycle of the bottoms fraction of the product to the HI reactor (described in more detail later), a CAT of 650° F or higher is required to prevent buildup of heavy component in the recycle stream. As such, for the recycle-to-extinction embodiment of the present invention, a CAT of 650° F or higher is desired. For example, in a preferred recycle-to-extinction operation, the HI CAT is in the 652-670° F range.

[0058] HI reactor effluent 216 is cooled through the second feed-effluent exchanger 62 and cooler 80 before separation through high pressure separator 82. The high-pressure separator gas phase 231 is directed to the compressor 44 B for recycle, while an isomerized liquid product 222 is directed to a fractionation train. The fractionation train comprises a product fractionator 84, a debutanizer 86, and a jet fuel tower 88 The product fractionator 84 separates a light hydrocarbon stream 226 that includes mainly C3-C8 hydrocarbons. The light hydrocarbon stream 226 is subsequently distilled in the debutanizer 86 to provide an overhead LPG stream 239 (consisting mainly propane, n-butane, and isobutane) and a naphtha fraction 228 (consisting mainly of C5-C8 n-paraffins and isoparaffins).

[0059] A product fractionator bottoms 224 is directed to the jet fuel tower 88 where the fraction a 572 F-cut (300 C) is distilled overhead to provide a synthetic paraffinic kerosene (SPK) 232, The SPK 232 has a freeze point of -40 C or less. The SPK has a 15° C density of at least 0.765 g / mL (as measured by ASTM DI 298, D4052, or similar). In embodiments, the SPK has a density between 0.765 and 0.776. For example, the SPK has a density of 0.766, 0.767, 0.768, 0.769, 0.770, 0.771, 0.772, 0.773, 0774, 0 775, or a density between any two of these values. For example, in a preferred embodiment, the SPK has a density between 0.770 and 0.772 In embodiments, the SPK 232 conforms to ASTM D7566 specifications for HEFA.

[0060] Returning to the jet fuel tower 88, a jet tower bottoms 234 is recycled to the HI reactor 70 via pump 90. A pumped bottoms recycle 236 is thus combined with the pumped fresh HI feed 211 to provide the HI reactor feed 238. The HI feed includes between 10% and 40% jet tower bottoms 234.Atty. Docket No. T-12678-WO01

[0061] The HI reactor 70 LHSV based on volumetric flow rate of combined HI reactor feed 238 divided by total catalyst volume is between 0.5 / h and 5.0 / h, preferably between 0.7 / h and 3.0 / h.

[0062] The yield of the SPK 232 on HI feed 211 mass basis is between 84 and 94%. The SPK has a combined C17 and C18 paraffin content between 35 and 65 wt %, preferably between 40 and 60 wt %. The iso / normal ratio of the C17 and C18 paraffins is between 100 and 500. The SPK has a C17 and C18 cycloparaffin content between 0.5 and 2.0 wt %, with no detectable aromatics or oxygenates. The high C17 and Cl 8 paraffin content at very high iso / normal ratios suggests a very high isomerization selectivity vs. hydrocracking side reactions. It was therefore surprising to observed that at HI reactor CAT values of 650 F or higher, no buildup of heavy components in the jet tower bottoms recycle 234 occurs enabling the “recycle to extinction operation” providing high SPK yields and without heavy diesel and minimal light naphtha coproduction. An optional jet tower bottoms purge 235 may be used if necessary (e.g., if HI reactor CAT needs to be lowered).A Second Embodiment of the Present Technology

[0063] The SPK compositions of the present invention may also be produced by a different method as depicted in FIG. 2. The process streams 222, 224, 236, 228, 230, and equipment reference numbers 84 and 86 are as described for FIG. 1. In embodiments where the fatty acid profile of the lipid feedstock includes less than 0.1 wt % C24 fatty acids, and includes less than 0.5 wt % unsaponifiable matter, the product fractionator bottoms 224 is a paraffinic kerosene suitable for use as a jet fuel blendstock.

[0064] In alternative embodiments, the product fractionator bottoms 224 is pressurized through pump 92 to provide a membrane feed 302. The membrane feed 302 is processed through an Organic Solvent Nanofiltration (OSN) unit 94. The OSN 94 separates the C19 and heavier hydrocarbons from the product fractionator bottoms to provide a “Cl 9 plus” retentate and SPK permeate 303. The SPK permeate has a final boiling point of 300 C or less as measured by ASTM D86. The SPK has a combined C17 and Cl 8 paraffin content between 35 and 65 wt %, preferably between 40 and 60 wt %. The iso / normal ratio of the C17 and C18 paraffins is between 100 and 500.Atty. Docket No. T-12678-WO01

[0065] The retentate 304 includes a portion of the Cl 7 / CI 8 paraffins in addition to the Cl 9 and heavier hydrocarbons. This retentate represents less than 10% of the membrane feed 302 and may be used a diesel blendstock or as a specialty fluid.

[0066] From the above description, it is clear that the present invention is well adapted to carry out the objects and to attain the advantages mentioned herein as well as those inherent in the invention. While presently preferred embodiments of the invention have been described for purposes of this disclosure, it will be understood that numerous changes may be made which will readily suggest themselves to those skilled in the art and which are accomplished within the spirit of the invention disclosed and claimed.EXAMPLESExample 1. Preparation of Paraffins for Hydroisomerization Experiments

[0067] A blend of low-value fats, oils, and greases (FOG) comprising used cooking oil and bleachable fancy tallow (a low-value inedible animal fat) was processed through a feed pretreatment unit. This included citric-acid treatment and centrifugation, followed by adsorption by amorphous silica and pressure leaf filtration as generally described in US Patents 9,404,064, 11,183,133 and 11,459,523.

[0068] The pretreated FOG, with a phosphorus, iron, sodium, potassium, calcium and magnesium content less than 8 wppm, was subjected to hydrotreating in a fixed-bed reactor system comprising sulfided Mo and NiMo catalysts. The hydrotreating was performed according to the conditions described earlier in this disclosure.

[0069] The product was analyzed by a GCxGC method and confirmed to be mainly a C14-C20 paraffin composition a C15-C18 n-paraffin composition with about 0.2 wt % C36 n-paraffins. No oxygenates of aromatics were detected. C16-C18 n-paraffins made up 86 wt % of the composition, (see Figure 3).

[0070] Separately, store-bought canola oil was hydrotreated with a NiMo catalyst according to conditions disclosed in the specifications. The GCxGC composition of the paraffinic product is presented in Figure 4. In addition to higher C18 paraffin content (87 wt % total Cl 8, and 83Atty. Docket No. T-12678-WO01wt % nCl 8), the canola oil also shows 0.28 wt % C24 n-paraffin that was not detected in the FOG HDO product. This C24 paraffin is believed to be the direct product of the hydrodeoxygenation of C24:0 / C24: 1 fatty acids that are observed in canola oil but not in FOG lipid constituents.Example 2, Recycle-to-Extinction Hydroisomerization

[0071] An integrated hydroprocessing and product fractionation pilot unit was used for these experiments. The reactor was loaded with an ISODEWAXING catalyst as described in US Patent US Patent 11,987,757, herein incorporated by reference. The hydrotreated lipid product described in Example 1 was used as fresh feed for hydroisomerization (HI) in the reactor system described below.

[0072] The reactor system was set up such that after separation of liquid from gas in a high-pressure separator, the effluent from the hydroisomerization (HI) reactor was directed to a fractionation train including a distillation column for stripping light hydrocarbons (mainly C8 and lighter) from the hydroisomerizate before distillation in a different column immediately downstream. The overhead distillate from this second column was evaluated as paraffinic kerosene for use as jet fuel blend component. In the “Recycle-to-Extinction" mode, the bottoms fraction from this column was combined with fresh feed and recycled back to the HI reactor.

[0073] The HI reactor was operated at a pressure of 970 psig under hydrogen flow conditions at a hydrogen gas-to-oil ratio of 2500 SCF / Bbl. The reactor CAT, LHSV, and bottoms fraction recycle rate were varied for different experiments. Table II summarizes the operating conditions and corresponding product yields, and kerosene product properties. Each run condition for Examples 2a, 2b, 2c, and 2d was maintained for several days (4-8 days) to confirm whether steady-state operation was reached for the bottoms recycle stream.Atty. Docket No. T-12678-WO01Table II. Recycle to Extinction HI Reactor Operation for Paraffinic Kerosene ProductionOperating Conditions Example 2a Example 2b Example 2c Example 2d Lipid source of fresh feed FOG FOG FOG Canola oil CAT (‘F) 645 653 653 650 Fresh feed LHSV (1 / h) 1.0 1.1 1.1 0.81 Overall LHSV (1 / h) 1.3 1.7 1.4 1.0 % Recycle = 1-(FF LHSV / overall 23% 35% 21% 19% LHSV)YieldsLight gases (%) 3.1-3.2 4.3-4.5 4.5-5.1 5.8-6.1 Naphtha (%) 3.1-3.3 5.3-5.4 2.2-4.0 6.7-6.9 Kerosene (%) 91-92 89 90-91 86-87 Kerosene Physical PropertiesFlash point (‘C) 41-44 40-46 37-39 45 Freeze point (‘C) -41 to -43 -52 to -53 -48 to -52 <-60 D86 distillation end point (‘F) 560-562 556-557 560-561 558-560 Density (g / mL) 0.772-0.773 0.771 0.772 0.772 Kerosene CompositionC17+C18 isoparaffins (wt %) 52 47 48 60 C17+C18 n-paraffins (wt %) 0.50 0.20 0.35 0.12 C17+C18 cycloparaffins (wt %) 1.39 0.81 1.34 1.41 C17+C18 iso / normal ratio 104 235 137 500 Properties of Bottoms RecycleBuildup of C35+ heavies? Yes No No No

[0074] As observed from Table II, at 645 F reactor temperature (Example 2a), the bottoms recycle continued to show buildup of heavy components. According to GCxGC analysis, the C35 and C36 isoparaffins in that recycle stream increased in concentration from about 4.3% to 16% over a period of 8 days.

[0075] For Examples 2b-2d, higher HI reactor temperatures were used. At these conditions, the recycle-to-extinction operation achieved steady-state bottoms recycle composition with no increase in C36 or other heavy components. It thus appears that 645 F is too low of a CAT for recycle-to-extinction operation without a purge stream.Atty. Docket No. T-12678-WO01In Example 2d, the hydrotreated canola oil referenced in Example 1 was used as fresh feed to the HI reactor system. The C18 paraffin content of the feed was 86.7 wt % compared to 57.6 wt % for Example 2a-2c. In all cases, the paraffinic kerosene D86 end point values were well below the 572 F upper specification limit despite high density values of 0.770 g / mL and greater, and C17+C18 paraffin content in the 48-61 wt % range. No aromatics or oxygenates were detected in any of the SPK products.Example 3, Distillation Bottoms SPK

[0076] A bench scale hydroisomerization reactor was loaded with the same catalyst described in the previous example. The reactor operated without product recycle. As such, the SPK product was the bottoms of distillation column to strip the light hydrocarbons / naphtha, as described in the second embodiment of the present technology. Experiments were conducted using both feeds described in Examples 1 and 2: (a) hydrotreated FOG and (b) hydrotreated canola oil. The HI reactor operating conditions and corresponding SPK product (distillation bottoms fraction) are presented in Table III.Table III. HI Conditions for Production of Bottoms SPK and Corresponding Properties of the SPKHI ConditionsFeed Hydrotreated Canola Hydrotreated FOGCAT (‘F) 676 680 678 670 675 675 680 LHSV 1.0 1.0 1.0 1.1 1.1 1.4 1.4 Pressure (psig) 970 970 970 970 970 970 970 Gas / oil ratio (SCFB) 2500 2500 2500 2500 2500 2500 2500 Yields (% weight feed basis)C1-C4 11.0 12.8 12.5 6.7 7.4 6.2 6.9 Naphtha 17.7 21.6 20.9 12.7 14.4 11.5 13.5 Kerosene 72.1 66.6 67.5 81.2 78.8 82.9 80.2 Kerosene PropertiesD86 End Point (‘F) 578 563 565 575 570 580 573 Density (g / mL) 0.7629 0.7533 0.7489 0.7665 0.7650 0.7684 0.7668 <-60 <-60 <-60 -58.3 -58 -53 -57Freezing Pt (‘C)Atty. Docket No. T-12678-WO01

[0077] As observed from Table Til, to achieve a D86 end point value of 572 F (300 C) or lower, the HI reactor needs to operate at temperature and LHSV conditions that result in relatively low yields of around 67%. By contrast, with hydrotreated FOG as HI feed, the reactor may be operated at less severe conditions (lower CAT and higher LHSV) to conform to the 572 F max end point specification. As a result, a higher yield of around 79% is achieved for the bottoms SPK product. Without being bound to theory, it is believed that the presence of C24 paraffins in the canola-based feed (absent in FOG) may be impacting conformance to the 572 F end point specification.

[0078] Use of membrane nanofiltration as described in the second embodiment of the present technology provides a low-energy method to remove these larger, high boiling components from the SPK. In order to meet the max end point for the bottoms product, more sever HI conditions (higher CAT / lower LHSV) and thus more hydrocracking and lower yields are observed.Example 4, Membrane Separation of Distillation Bottoms SPKA distillation bottoms SPK as described in Example 3 was subjected to Organic Solvent Nanofiltration Membrane separation using two different membranes, (1) Sol Sep NF030606 and (2) Solsep NF030501, denoted as Ml and M2 respectively. Each membrane was run at conditions of varying pressure at constant temperature (20, 30, and 40 barg at 40 C) or varying temperature at constant pressure (30, 40, and 56 C at 30 barg). The flux achieved at each condition was reported and the permeate and retentate samples collected. Based on GCxGC analysis of feed, permeate, and retentate, the % C19 paraffin reduction at each test condition was calculated and plotted as bar graph in FIG 5. The y-axis in FIG 5 is the change in C19 in the permeate compared to the feed. The results from the different constant pressure experiments are summarized there, results for the constant pressure experiments are presented as a bar graph in FIG 5.As observed from FIG. 5, membranes Ml and M2 reduced the C19-+ paraffin content of the distillation bottoms SPK by about 0.8 to 1.3%. This level of reduction is expected to achieve D86 end point conformance without need for increasing HI reactor operating severity and consequent distillation bottoms SPK yield loss.

Claims

Atty. Docket No. T-12678-WO01CLAIMS:

1. A synthetic paraffinic kerosene composition produced by hydrotreating and hydroisomerization of a lipid feedstock, the composition comprising(a) between 35 and 65 wt % C17 and C18 paraffins(b) between 0.5 and 2.0 wt % C17 and C18 cycloparaffins(c) no detectable oxygenates or aromaticswherein the composition has a final boiling point of 300° C or less and a 15° C density greater than 0.765 g / mL.

2. The composition of Claim 1 wherein the Cl 7 and C18 iso / normal ratio is between 100 and 500.

3. A method for producing a paraffinic kerosene comprising the steps:(a) hydrotreating a lipid to provide a paraffinic hydrocarbon composition(b) subjecting the paraffinic composition to hydroisomerization in a hydroisomerization reactor at a catalyst average temperature to provide an isomerizate(c) fractionatating the isomerizate to provide a paraffinic kerosene with 35-65 wt % C17 and Cl 8 paraffins and a bottoms fraction(d) recycling the bottoms fraction to the hydroisomerization reactorwherein the catalyst average temperature is at least 650 F and the bottoms fraction recycle is between 10 and 40% of the hydroisomerization reactor feed.

4. The method of Claim 3 wherein the C17 and C18 paraffins have an iso / normal ratio between 100 and 500.

5. The method of Claim 3 wherein the paraffinic kerosene yield is between 85 and 94%.Atty. Docket No. T-12678-WO016. A method for producing a paraffinic kerosene comprising the steps:(a) hydrotreating a lipid with less than 0.1 wt % C24 fatty acids and less than 0.5 wt % unsaponifiable matter to provide a paraffinic hydrocarbon composition(b) subjecting the paraffinic kerosene to hydroisomerization in a hydroisomerization reactor at a catalyst average temperature to provide an isomerizate(c) stripping the isomerizate of light hydrocarbon in a distillation column to yield the paraffinic kerosene as the distillation column bottoms fraction wherein the paraffinic kerosene has a D86 end point of 300 C or less.

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