Process for producing biomass-based diesel from feedstocks containing olefin oligomers - Patent Application 20070122999

Abstract

This technology relates to biofuels, and more particularly to biomass-based diesel from olefin oligomers. By blending hydrocarbons produced by olefin oligomerization with renewable diesel, diesel fuel with a cetane number of 49 or higher is prepared, resulting in a blended fuel with a cloud point lower than that of the renewable diesel. Another aspect relates to an integrated process for lipid HDO and olefin oligomerization, in which the propane co-product of lipid HDO is subjected to dehydrogenation to produce a vapor stream containing propylene and hydrogen. The propylene is then oligomerized into isoolefins, and the isoolefins are combined with the lipid feedstock for hydrogenation in the HDO reactor.

Description

[Technical Field]

[0001] This technology relates to biofuels, and more particularly to biomass-based diesel fuels. [Background technology]

[0002] This application claims priority to U.S. Provisional Application No. 63 / 378,193, filed October 3, 2022, the entire contents of which are incorporated herein by reference.

[0003] Hydroprocessing of lipids for the production of renewable diesel (RD) fuels has been described in the prior art, such as U.S. Patent Nos. 8,026,401 and 7,968,757, which are incorporated herein by reference. As described in these and several other references, RD is typically produced in two conversion steps. In the first step, a hydrodeoxygenation (HDO) reaction converts lipid fatty acid / glyceride molecules into hydrocarbons, including diesel-boiling range n-paraffins and propane. Water, CO, and CO are the primary by-products of HDO. In a second step, linear n-paraffins in the HDO product are converted to primarily methyl-branched paraffins to convert C n-paraffin "wax" and improve cloud point and other cold flow properties. This second step is called "catalytic dewaxing" or "hydroisomerization" (HI).

[0004] HDO reactors typically operate with a partial recycle of the hydrocarbon product. The recycle hydrocarbon acts as a solvent to dilute the lipid feedstock. Dilution provides many benefits to HDO performance, including controlling the heat release associated with the exothermic reaction, improving hydrogen solubility, and minimizing undesirable side reactions. Some prior art documents teach a hydrocarbon-to-lipid dilution ratio of at least 5:1. High dilution and recycle rates often require the use of large reactors and recycle pumps. This means that capital and operating costs per unit of RD produced are correspondingly higher.

[0005] RD is considered a premium diesel fuel due to the substantial absence of aromatics in its paraffinic hydrocarbon composition. Depending on the lipid feedstock, RD typically has a carbon intensity in the range of 30–40 gCO2e / MJ. Carbon intensity is a measure of lifecycle greenhouse gas (GHG) emissions, expressed as grams of CO2 equivalents per megajoule of combustion energy supplied by the fuel. Quoted RD carbon intensity values ​​are 60–70% lower than those reported for petroleum-based diesel fuel. Therefore, RD production has rapidly increased over the past decade as a response to climate change. With further increases in production capacity announced, the availability of lipid feedstock for RD production has emerged as a long-term concern.

[0006] Sugars are another type of biofuel feedstock. They can be fermented and converted into alcohol, which can be used directly in gasoline engines. Ethanol and isobutanol are examples of such alcohols. Currently, corn and sugarcane are commonly used for bioalcohol production, but fermentable sugars can also be produced by hydrolysis of cellulose and hemicellulose from woody biomass. Therefore, sugars and starches have the potential to be abundant sources of low-carbon-intensity renewable biofuel feedstocks.

[0007] To utilize these feedstocks for the production of middle distillate fuels (i.e., kerosene and diesel), the alcohols are first converted to olefins by catalytic dehydration. The olefins (e.g., ethylene and butene) are then oligomerized to produce primarily branched olefin dimers, trimers, tetramers, and pentamers, and, under certain conditions, even larger molecules (called isoolefins). Oligomerization, like all polymerization reactions, produces a range of hydrocarbon molecular weights that follow a Schultz-Flory distribution. In most cases, these isoolefins are highly branched, with substantially no linear hydrocarbons in the product composition. These isoolefins can be hydrogenated and fractionated to obtain isoparaffinic middle distillate cuts. U.S. Patent No. 8,975,461 describes such a process. U.S. Patent Application Publication No. 2017 / 0260548 discloses the production of isobutene directly from fermentation (without first producing alcohol).

[0008] Due to the highly branched nature of the oligomeric molecules (containing multiple tertiary and quaternary carbons in the hydrocarbon chain), the corresponding fuels generally have very low cetane numbers. For example, the aforementioned '461 patent indicates that C12 and C16 hydrocarbons from the oligomerization / hydrogenation of isobutene include 2,2,4,6,6-pentamethylheptane (isododecane) and 2,2,4,4,6,8,8-heptamethylnonane (isohexadecane). These compounds have cetane numbers of 9 and 15, respectively, as reported in the "Compendium of Experimental Cetane Numbers" (National Renewable Energy Laboratory; 2017). The minimum cetane numbers specified for diesel fuel according to industry standards ASTM D975 and EN 590 are 40 and 49, respectively, suggesting that olefin oligomerization is not a suitable method for producing diesel fuel products.

[0009] When ethylene (from ethanol dehydration) is used to produce middle distillate fuels, the oligomerization reactor system is typically operated so that the ethylene is first dimerized to butenes, which are then oligomerized to higher-boiling hydrocarbons. Thus, similar branched isoparaffinic hydrocarbons are produced. According to examples in U.S. Patent Application Publication No. 2017 / 02188283, linear hydrocarbon products from ethanol-based ethylene oligomerization are only 0.2-0.3%.

[0010] The present invention addresses at least two of the aforementioned unmet needs. First, it provides a method for producing high-cetane, drop-in renewable hydrocarbon diesel from sugar-based feedstocks. Second, it provides a method for operating a renewable diesel reactor without recycle of the hydrocarbon product, thus allowing for more productive utilization of reactor assets. Summary of the Invention

[0011] In one aspect of the present technology, a diesel fuel having a cetane number of 49 or greater is prepared by blending hydrocarbons produced by olefin oligomerization with renewable diesel, resulting in a blended fuel with a cloud point lower than that of the renewable diesel.

[0012] In a different aspect of the present technology, olefin oligomers (isoolefins) are hydrogenated to isoparaffins in a lipid hydrodeoxygenation (HDO) reactor, with a volumetric ratio of isoolefins to lipid feedstock ranging from about 1:5 to 5:1. In embodiments, the olefins are derived from ethanol and / or isobutanol. In other embodiments, the HDO reaction is carried out without solvent or product recycle. In further embodiments, the HDO product is used as renewable diesel fuel without a subsequent isomerization step. In yet further embodiments, the HDO product has a cloud point below 0°C and a cetane number of 49 or greater.

[0013] A different aspect of the present technology relates to an integrated process for lipid HDO and olefin oligomerization. In some embodiments, the propane co-product of lipid HDO is dehydrogenated to produce a vapor stream containing propylene and hydrogen. The propylene is then oligomerized into isoolefins, and the isoolefins are combined with the lipid feedstock for hydrogenation in the HDO reactor. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a process flow diagram illustrating a process for producing renewable diesel according to one embodiment of the present technology. [Figure 1A] FIG. 1A is a process flow diagram illustrating an alternative embodiment for producing biomass-based diesel according to the present technology. [Figure 2] FIG. 2 is a process flow diagram illustrating an alternative embodiment of the present technology for dehydrogenating propane from lipid HDO to propylene for oligomerization. DETAILED DESCRIPTION OF THE INVENTION

[0015] In this disclosure, the term hydrodeoxygenation or HDO is used to describe a reaction in which feedstock deoxygenation (e.g., removal of oxygen heteroatoms from feed materials such as fatty acid glycerides) is carried out under hydrogen pressure in the presence of a catalyst. HDO specifically refers to the removal of oxygen with hydrogen in the form of water, but the reaction is typically accompanied by decarboxylation (removal of oxygen as CO) and decarbonylation (removal of oxygen as CO) and saturation of carbon-carbon double bonds. HDO products are hydrocarbons rich in normal paraffins (n-paraffins).

[0016] The term hydroisomerization or HI is used herein to describe the partial conversion of the HDO product to a mixture of normal and methyl-branched paraffins. As used herein, the term paraffins includes both n-paraffins and methyl-branched paraffins produced by hydroisomerization.

[0017] As used herein, the term oligomeric isoolefin refers to a branched hydrocarbon distribution produced by the oligomerization of olefins such as propylene or butene. The term oligomeric isoparaffin refers to the saturated product corresponding to the isoolefin, i.e., the product of isoolefin hydrogenation.

[0018] Conversion of Alcohols to Olefins: The conversion of alcohols to olefins is given by Equation 1, where n has a value of 2 or greater. C n H (2n+1) OH→C n H 2n +H2O(1)

[0019] Common fermentation-derived alcohols include ethanol (C2H5-OH) and butanol (C4H7-OH), although bio-based processes for propanol and pentanol (also known as amyl alcohol) have also been disclosed and are known to those skilled in the art (e.g., U.S. Patent Application Publication No. 2009 / 0014689).

[0020] Equation 1 is known as alcohol dehydration and can be carried out using both heterogeneous and homogeneous catalysts. Examples of heterogeneous catalysts include various acid-treated and untreated alumina and silica catalysts and clays. These include zeolites (e.g., ZSM-5), fluoride-treated clay catalysts, and sulfonic acid resins. Because the dehydration reaction produces water as a by-product, the catalyst used in the reaction generally must be water-resistant. Homogeneous catalysts for alcohol dehydration include phosphoric acid, sulfuric acid, and Lewis acids such as aluminum trichloride and boron trifluoride.

[0021] Alcohol dehydration reactions are generally carried out at temperatures of about 450 to about 650°F under pressures ranging from 0 to 100 psig. A typical commercial embodiment involves introducing the alcohol in the vapor phase into a fixed-bed reactor containing a zeolite catalyst. A process for converting Fischer-Tropsch alcohols to olefins is described in U.S. Patent No. 6,939,999.

[0022] Publications, patents, and patent applications are referenced throughout this disclosure. All references cited herein are incorporated by reference.

[0023] Paraffin dehydrogenation: Propane and n-butane / isobutane dehydrogenation are commercial processes licensed by companies such as UOP (OLEFLEX), CB&I McDermott / Clariant (CATOFIN), and Thyssenkrupp Industrial Solutions / Uhde (STAR). Unlike thermal cracking (e.g., steam cracking) of LPG / naphtha, which produces a large number of different olefins and diolefins, these selective catalytic reactions preserve the hydrocarbon structure of the feedstock while remaining unsaturated, as shown in Equation 2. C n H 2n+2 ⇔ C n H 2n +H2(2)

[0024] The dehydrogenation of paraffins is an endothermic reaction favored at high temperatures and low pressures (to drive the vapor-phase equilibrium reaction in Equation 2 to the right side of the equation). To achieve approximately 50–65% conversion per pass in this equilibrium-limited reaction, commercial dehydrogenation units operate at temperatures above 1,000°F to 1,200°F and pressures ranging from a slight vacuum to 40 psig. At such high operating temperatures, the catalyst tends to be deactivated by coking. Therefore, commercial reactor systems include provisions for catalyst regeneration by coke combustion. In some reactor systems, steam is introduced to mitigate carbon formation.

[0025] Catalysts used in commercial dehydrogenation processes are of two types: (1) noble metals (mainly Pt-Sn) supported on alumina or Zn and Mg aluminates with alkali metal oxide promoters, and (2) chromium oxides supported on alumina or zirconia and promoted with cesium, potassium, or rubidium.

[0026] Commercially available dehydrogenation unit designs include adiabatic fixed-bed reactors with reaction, purge, and / or regeneration cycles, isothermal top-fired multi-tube reactors, moving-bed reactors with interstage heaters, and fluidized-bed reactors with circulation through a regenerator (thus providing heat to the reaction).

[0027] Olefin Oligomerization: The conversion of light olefins to higher boiling range isoolefins is represented in the exemplary case of propylene by Equation 3. The value n represents the number of repeat units in the oligomer, with 2 corresponding to a dimer, 3 to a trimer, 4 to a tetramer, etc. nCH2=CH-CH3→CH3-[CH(CH3)-CH2] n-1 -CH=CH2(3)

[0028] Olefin oligomerization is a petroleum refining process dating back to the 1930s. It has been used to produce so-called "polymer gasoline" (propylene and / or butene dimers / trimers). This process has also been used to produce the chemical intermediates nonene and dodecene, as well as end products used as surfactants, plasticizers, and lubricants. This reaction has traditionally been carried out over a bed of solid phosphoric acid (SPA) catalyst at temperatures ranging from 300 to 1100°F under pressures ranging from near atmospheric to 2000 psig. The average molecular weight (or average carbon number) of the product is inversely proportional to temperature, with lower temperatures favoring the production of heavier hydrocarbons. To increase the yield of diesel boiling range fractions, a portion of the gasoline range hydrocarbons (i.e., propylene and butene dimers) is partially recycled to the reactor. This recycle is often in the form of a liquid quench between catalyst beds to mitigate the temperature increase associated with the exothermic oligomerization reaction. Acidic zeolite catalysts have been used in more recent commercial processes. Other catalysts reported in recent scientific and patent literature include zirconia, tungstated zirconia, sulfated titania, and nickel-modified tungstated zirconia, which are reported to be more active and water-resistant than SPA catalysts.

[0029] Hydrogenation and Hydrodeoxygenation: The isoolefins produced by oligomerization are hydrogenated to isoparaffinic kerosene. Hydrogenation is often carried out at temperatures ranging from 250 to 500°F and under relatively high pressures (100 to 2,000 psig). Preferred catalysts include palladium on alumina, or reduced nickel on the same support or as a sponge metal catalyst (e.g., Raney catalyst).

[0030] For lipid hydrodeoxygenation, hydrogenolysis-active molybdenum sulfide or tungsten sulfide catalysts are preferred. Promoters for HDO catalysts include nickel and cobalt. In the present invention, reactor conditions are selected so that isoolefin hydrogenation and lipid HDO occur simultaneously, as shown in Equation 4 below. Equation 4 occurs at temperatures ranging from 500 to 700°F under H2 partial pressures of about 500 to 2,500 psi. [ka]

[0031] Embodiments of the present technology: Referring to the process embodiment shown in FIG. 1 , lipid feedstock 101A, which includes naturally occurring fatty acids and fatty acid esters / glycerides, is combined with oligomer feedstock 101B in drum 10 to obtain composite feedstock 102 for transfer to HDO reactor 20.

[0032] Exemplary components of lipid feedstock 101A include, but are not limited to, animal fats, animal oils, microbial oils, vegetable fats, vegetable oils, vegetable fats, vegetable oils, vegetable oils, greases, or a mixture of any two or more thereof (broadly referred to as FOG). For example, lipid feedstock 101A can include vegetable oils and / or vegetable oils and / or microbial oils. These include, but are not limited to, corn oil, distiller's corn oil, non-edible corn oil, babassu oil, carinata oil, soybean oil, canola oil, coconut oil, rapeseed oil, tall oil, tall oil fatty acids, palm oil, palm oil fatty acid distillates, palm sludge oil, jatropha oil, palm kernel oil, shepherd's purse oil, sunflower oil, castor oil, camelina oil, archaeal oil, bacterial oil, fungal oil, protozoan oil, algae oil, seaweed oil, oils derived from halophilic bacteria, seed oils derived from wild shepherd's purse and other flowering plants, and mixtures or combinations of two or more thereof. These can be classified as crude, degummed, and RBD (refined, bleached, and deodorized) grades depending on the level of pretreatment and residual phosphorus and metal content. However, any of these grades may be used in the present technology. The animal fats and / or oils used above include, but are not limited to, inedible tallow, edible tallow, industrial tallow, floating tallow, bleachable premium tallow, lard, industrial lard, premium white grease, poultry fat, poultry oil, fish fat, fish oil, and mixtures of two or more thereof. Grease may include, but is not limited to, yellow grease, brown grease, waste vegetable oil, restaurant grease, trap grease from municipalities such as water treatment plants, used oil from industrial packaged food operations, and mixtures of two or more thereof.

[0033] The lipid feedstock 101A can include up to 90% free fatty acids (FFAs). Specifically, the renewable feedstock 101 can include about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90% by weight, or a range inclusive of and / or between any two of these values.

[0034] The lipid feedstock 101A may optionally be pretreated to remove phosphorus and metal contaminants to less than 10 wppm total, as disclosed in the prior art (e.g., U.S. Pat. No. 9,404,064 to Gay).

[0035] Oligomeric feedstock 101B is a hydrocarbon comprising isoolefins (branched hydrocarbon molecular structures with carbon-carbon double bonds) formed by the oligomerization of ethylene, propylene, and / or butenes (including 1-butene, 2-butene, and isobutene or isobutylene). In embodiments, the isoolefins are produced by the oligomerization of isobutene. In embodiments, the isobutene is the product of the dehydration reaction of isobutanol, and the isobutanol is bioisobutanol formed by the fermentation of sugars / starch.

[0036] The oligomer feedstock 101B has a carbon number ranging from C6 to C30, preferably C6 to C24. The ratio of oligomer feedstock 101B to lipid feedstock 101A can vary widely. In embodiments, the ratio of oligomer feedstock 101B to lipid feedstock 101A can range from about 5:1 to about 1:5, preferably from about 3:1 to about 1:3. In embodiments, the oligomer to lipid ratio is about 3:1 to about 5:1.

[0037] Feedstocks 101A and 101B are combined in surge drum 10 to form composite feedstock 102. Composite feedstock 102 is transferred to HDO reactor 20 using high-pressure pump 12 to form pressurized liquid feedstock 103. Pressurized liquid feedstock 103 is further combined with pressurized hydrogen 133 to form mixed-phase feedstock 118. Mixed-phase feedstock 118 is then heated by feed-effluent exchanger 30 to form partially heated feedstock 119. Partially heated feedstock 119 is further heated in reactor preheater 46 to provide reactor feedstock 107. Reactor feedstock 107 is maintained at a temperature between 420°F and 680°F, preferably between 450°F and 650°F.

[0038] HDO reactor 20 contains at least one bed of a sulfided catalyst, comprising molybdenum or tungsten. Preferred catalysts include sulfided nickel-molybdenum (NiMo), nickel-tungsten (NiW), or cobalt-molybdenum (CoMo) on an alumina or silica-alumina support. As described herein, those skilled in the art will appreciate that any catalyst or combination of catalysts may be used in the present invention, so long as the catalyst system functions in accordance with the present invention.

[0039] Despite the absence or very low (<40 wppm) concentrations of organic sulfur in most oligomeric and lipidic feedstocks, to maintain the functionality of the active metal sulfides of the catalyst, the composite feedstock 102 can be supplemented with sulfur compounds that decompose to hydrogen sulfide upon heating and / or contact with the catalyst. Two preferred sulfur compounds are dimethyl disulfide and carbon disulfide. Their preferred concentrations in the composite feedstock 102 are from about 100 to about 2,000 wppm sulfur. Alternatively, the feedstock 102 can include a petroleum fraction, which provides the sulfur.

[0040] Each catalyst bed in HDO reactor 20 can operate at a temperature ranging from about 450°F (232°C) to about 750°F (399°C). Weighted average bed temperature (WABT) is commonly used in fixed-bed adiabatic reactors to represent the "average" of the reactor, taking into account the nonlinear temperature profile between the reactor inlet and outlet, according to Equation 5.

number

[0041] In Equation 5, T i in and T i out and ω refer to the inlet and outlet temperatures of catalyst bed i, respectively. As shown, the WABT of a reactor system with N different catalyst beds is calculated by multiplying the WABT of each bed (WABT i ) and the weight fraction of catalyst in each bed (Wc i The WABT of the HDO reactor 20 is between 540°F and 680°F, preferably between 580°F and 650°F.

[0042] 1 shows a reactor having two beds, an upper bed 22A and a lower bed 22B. Each bed 22A, 22B contains approximately half of the total catalyst mass in the reactor. In this embodiment, hydrogen quench gas 104 is introduced through a mixing box 23 between the two beds 22A, 22B.

[0043] In one embodiment, the upper bed 22A contains a size-graded inert medium to distribute the solid particles picked up and reduce pressure drop buildup. In another embodiment, the lower bed 22B contains a catalyst with isomerization activity. Examples of such catalysts include those with acid-functional supports such as NiW on silica-alumina. The supports can be crystalline or amorphous, the former containing zeolites.

[0044] The HDO reactor 20 operates at a pressure of 500 psig to 3,000 psig, preferably 1000 psig to 2000 psig. The liquid hourly space velocity through the HDO reactor 20 is about 0.2 to about 10 h -1 , preferably about 0.5 to about 5.0 hours -1 (volume flow rate of composite feed 102 per time per volume of catalyst). The ratio of hydrogen-rich treat gas 132 to composite feed 102 ranges from about 4,000 to about 15,000 SCF / bbl, preferably between 5,000 and 12,000 SCF / bbl. The hydrogen-rich treat gas 132 may contain from about 70 to about 100 mole percent hydrogen.

[0045] HDO reactor effluent 110 is partially cooled through feed effluent exchanger 30 to provide partially cooled HDO reactor effluent 111, and then further cooled through cooler 32 to provide cooled HDO reactor effluent 112. The cooled reactor effluent 112 contains a liquid hydrocarbon fraction and a vapor fraction containing unreacted hydrogen. The liquid contains primarily n-paraffins and isoparaffins in the C6 to C24 range, with up to 2% compounds heavier than C24. The hydrogen-rich vapor contains, in addition to hydrogen, C1 to C6 hydrocarbons, water, carbon oxides, ammonia, and hydrogen sulfide. The liquid and vapor in the two-phase cooled reactor effluent 112 are separated in high-temperature separator 34.

[0046] High temperature separator 34 operates at a temperature between 250-500°F and at the HDO reactor discharge pressure (about 500 to about 2,000 psig in a preferred embodiment).

[0047] Vapor stream 124 containing C1-C6 hydrocarbons, unreacted hydrogen, water, carbon oxides, ammonia, and hydrogen sulfide is cooled through cooler 40 to provide cooler effluent 126 containing condensed liquid. Cooler 40 is operated so that the temperature of cooler effluent 126 is between about 80°F and 150°F. Water stream 125 is introduced to wash cooler 140 and minimize the buildup of salts, such as salts containing ammonium and sulfide ions.

[0048] The cooler effluent 126 contains "sour" water, condensed hydrocarbons, and hydrogen-rich gas. These components are separated in the cryogenic separator 42 to produce sour water 128, a condensed hydrocarbon stream 128A, and a hydrogen-rich gas 129. The condensed hydrocarbon stream 128A contains the lighter fraction of the HDO reactor hydrocarbons, primarily hydrocarbons in the C3 to C18 range. In yet another embodiment, a gas absorption solvent 127 is introduced into the cryogenic separator 42 to facilitate removal of impurities such as CO2 and H2S from the hydrogen-rich gas absorption solvent 127. The gas absorption solvent 127 can be an amine or an alkaline aqueous solution, such as an alkaline aqueous solution containing sodium hydroxide.

[0049] In addition to hydrogen, the hydrogen-rich gas 129 contains propane and small amounts of other non-condensable hydrocarbons. The gas is mostly recycled to the HDO reactor as recycled hydrogen gas stream 130, but bleed gas 129A is removed from the HDO reactor system to prevent non-reactive components from accumulating in the recycled gas.

[0050] Recycled hydrogen gas stream 130 is combined with make-up hydrogen gas 131 to provide treat gas 131A, which is compressed in compressor 44. Compressor 44 pressurizes the treat gas to reactor pressure (500-3000 psig; preferably 1000-2000 psig) and provides pressurized hydrogen-rich treat gas 132 to HDO reactor 20, as previously described in the description of this embodiment.

[0051] Returning to the high-temperature separator 34, the hydrocarbon liquid 114, comprising C8 to C24 hydrocarbons with up to 3% hydrocarbons heavier than C24, is processed through a stripper column 50, where steam 121 serves as the vaporizer. Alternatively, column 50 can use a reboiler instead of steam to achieve the purpose of column 50. Condensed hydrocarbon stream 128A is also fed to stripper column 50 to provide stripped hydrocarbon product 122 and stripper overhead steam 123. Stripper column 50 operates at a lower pressure than high-temperature separator 34 and low-temperature separator 42. In an embodiment, stripper column 50 operates at a pressure between 50 psig and 500 psig, preferably between 60 psig and 200 psig. The purpose of stripper column 50 is to remove water, hydrogen sulfide, and ammonia from hydrocarbon product 122. Thus, hydrocarbon product 122 contains less than 100 wppm water, less than 5 wppm sulfur, and less than 5 wppm nitrogen. In an embodiment, stripper column 50 is operated to remove light hydrocarbons such that the hydrocarbon product 122 has a flash point of 38° C. or greater, preferably 52° C. or greater. In an embodiment, overhead vapor 123 comprises C8 or lighter hydrocarbons, including C6 and C8 isoparaffins.

[0052] The hydrocarbon product 122 has an isoparaffin to normal paraffin ratio of about 5:1 to 1:5, where the isoparaffins are hyperbranched. In other words, the isoparaffins have two or more alkyl substituents. In embodiments, the isoparaffin to normal paraffin ratio is about 3:1 to 1:3. Depending on the oligomeric feedstock and lipid fatty acid profile, the hydrocarbon product 122 has a carbon number ranging from C6 to C24, with about 2-3% of the hydrocarbons being heavier than C24. In embodiments, the hydrocarbon product 122 has a carbon number ranging from C8 to C24. In embodiments, the hydrocarbon product 122 has a cetane number of 49 or greater, a cloud point of 10°C or less, and a flash point of 52°C or greater. In embodiments, the hydrocarbon product 122 is used directly as a drop-in renewable diesel fuel conforming to ASTM D975 or EN 590 standards.

[0053] In some embodiments, especially when the ratio of isoparaffins to normal paraffins is less than 2:1, the hydrocarbon product 122 is hydroisomerized according to methods described in the prior art (e.g., U.S. Pat. No. 5,814,109) to further reduce the cloud point and other low temperature attributes of the renewable diesel product.

[0054] In other embodiments, the isoparaffinic kerosene (primarily the C9 to C15 fraction of the renewable diesel fuel described herein) is separated by distillation of the hydrocarbon product 122.

[0055] In FIG. 1A, selected elements of FIG. 1 are shown to highlight an alternative embodiment. In this embodiment, the lipid feedstock 101A and the oligomeric isoolefins 101B are not combined as a single reactor feed. Instead, the oligomeric isoolefins 101B are fed to the upper bed 22A of the HDO reactor 20, and the lipid feedstock is fed to the lower bed 22B (via a high-pressure pump, not shown). In the embodiment of FIG. 1A, the upper bed 22A contains a non-sulfided hydrotreating catalyst (e.g., reduced nickel or palladium on an alumina support), while the lower bed 22B contains a sulfided catalyst as previously described in the description of FIG. 1. In the embodiment of FIG. 1A, the hydrogen gas stream 130 is treated to be essentially free of HS or to reduce the HS content to a level that does not affect the performance of the non-sulfided catalyst in the upper bed 22B. Thus, the sulfur compounds specified in the description of FIG. 1 are introduced only to the lower bed 22B, which contains the sulfided catalyst.

[0056] In yet another embodiment, the propane co-product of the hydrodeoxygenation of mono-, di-, and triglycerides (corresponding to the glycerol component of the glyceride esters) is subjected to dehydrogenation. The propylene product of the dehydrogenation reaction is then oligomerized, and the oligomer product is sent to HDO reactor 20. This embodiment effectively converts biopropane to renewable diesel fuel and kerosene (e.g., for use as jet fuel blendstock) while achieving the benefits described herein, such as reducing the amount of hydrocarbon recycle for lipid dilution and providing HDO hydrocarbons containing highly branched isoparaffins. This embodiment is described through a discussion of Figure 2.

[0057] Referring to FIG. 2, bleed gas 129A from the HDO cryogenic separator gas described above with reference to the embodiment of FIG. 1 is directed to gas membrane 60, where the gas is split into permeate 202 and retentate 204. Smaller gas molecules are selectively enriched in the permeate, while larger gas molecules are enriched in the retentate. In an embodiment, the hydrogen concentration of bleed gas 129A is approximately 75-90 mol%. Permeate 202 is enriched to 92-96 mol% H2, with a propane content of 0.5 mol% or less. Retentate 204 is enriched to 30-50 mol% propane, with the hydrogen concentration reduced to 40-60%.

[0058] Retentate 204 is directed to dehydrogenation reactor system 70, where it is converted to propylene at a conversion of 50 to 65% under the low-pressure and high-temperature conditions previously described herein (under the prior art subsection on dehydrogenation). Dehydrogenator effluent 206, comprising propylene, propane, and hydrogen, is cooled and compressed in cooler / compression unit 80 to provide a gas stream compressed to a pressure ranging from 100 to about 1500 psig to provide compressed propylene-containing stream 208. In a preferred embodiment, cooler / compression unit 80 pressurizes the dehydrogenator effluent to a pressure similar to that of bleed gas 129A. Compressed propylene-containing stream 208 is subjected to an oligomerization reaction in oligomerization unit 90, operating under the conditions previously described herein (under the subsection on oligomerization).

[0059] The oligomerization reactor effluent 210 exiting the oligomerization unit 90 contains propylene oligomers, propane, and hydrogen. The propylene oligomers include isoolefins ranging from C6 to C24. The oligomerization reactor effluent 210 is separated in the separator unit 95 into an overhead vapor stream 214 and a liquid stream 212. The separation unit may be a flash drum or a column, as is well known to those skilled in the art. In a preferred embodiment, the overhead vapor stream 214 is recycled to the gas membrane 60 to separate the hydrogen and propane, with the hydrogen being recycled to the HDO unit and the propane being recycled to the propane dehydrogenation system 70.

[0060] Separator liquid stream 212 represents the isoolefins for combination with the lipid feedstock for HDO. Thus, the propane derived from the lipid hydrodeoxygenation is converted to isoparaffinic diesel fuel or kersone according to one aspect of the present technology. In an embodiment, the isoparaffinic kerosene (primarily the C9-C15 fraction of the diesel fuel described herein) is separated by distillation of the diesel product (stream 122 in Figure 1).

[0061] From the foregoing description, it is evident that the present invention is well adapted to carry out the objects and attain the advantages herein set forth, as well as those inherent therein. While presently preferred embodiments of the invention have been described for purposes of this disclosure, it will be understood that numerous modifications may be made which will readily suggest themselves to those skilled in the art and which are within the spirit of the invention as disclosed and claimed. The technology thus generally described will be more readily understood by reference to the following examples, which are provided by way of illustration and are not intended to be limiting of the technology.

[0062] example Example 1. Preparation of isoparaffin compositions to model isobutene oligomerization products Isododecane and isohexadecane were obtained from the commercial supplier Making Cosmetics. A blend of 85 wt. % isododecane and 15 wt. % isohexadecane was prepared to model the distribution of isobutene oligomerization products, as disclosed in the prior art (e.g., U.S. Patent Application Publication No. 2020 / 0010767, incorporated herein by reference). This isoparaffinic composition was labeled "oligomeric isoparaffin" for subsequent studies.

[0063] Example 2. Renewable diesel from lipids Renewable diesel samples produced by lipid hydroprocessing (hydrodeoxygenation of lipids to n-paraffins followed by hydroisomerization of n-paraffins) were analyzed for cloud point and the corresponding concentration of unconverted n-octadecane (nC18). Cloud point was measured using automated instruments such as Koehler and PhaseTech, as well as an older but official method described in ASTM D2500. nC18 content was measured using gas chromatography techniques (ASTM D2887), and values ​​were reported as GC peak area percentages (%). Various lipid feedstocks (e.g., used cooking oil, tallow, and distilled corn oil) were used in the production of these samples.

[0064] Hydrodeoxygenation (HDO) of the feedstock was carried out over a catalyst system containing NiMo at a pressure of 1700-1800 psig and a WABT of 600-660°F. The HDO reactor system was operated with a liquid product recycle. Dissolved gas-phase byproducts (e.g., hydrogen sulfide and ammonia) were removed from the HDO product and isomerized in a hydroisomerization (HI) reactor. The HI reactor contained a bifunctional precious metal catalyst (hydrogenation-dehydrogenation and acid functionality). The HI reactor was maintained at a pressure of approximately 970 psig, and the temperature was varied between a WABT of 600°F and 635°F to produce a variety of samples with different nC18 conversions and product cloud points.

[0065] Cloud points were plotted against nC18 content for 27 samples, ranging from -35°C for 1.8% nC18 to +12°C for 34% nC18. The results fell under a smooth curve given by Equation 6 (R 2 The correlation coefficient is 0.994). Cloud point (°C) = 15.5 ln(%nC18) - 43.0(6)

[0066] A sample of renewable diesel produced according to the method of this example was selected for blending studies with the oligomeric isoparaffin composition of Example 1. This sample was found to have a cloud point of -10°C (measured using the D2500 test method). Therefore, the %nC18 estimated using Equation 6 was 8.4%.

[0067] Example 3. Blending oligomeric isoparaffins with renewable diesel The oligomeric isoparaffin composition of Example 1 was blended with the -10°C cloud point renewable diesel (RD) of Example 2 in three different ratios as shown in Table I. The samples were analyzed using a Phase Technologies Dual Cloud Point and Freeze Point Analyzer (Model No. CPA-70Xi). The cloud point method is ASTM D5773.

[0068] [Table I]

[0069] Oligomeric isoparaffins lack nC18 and therefore function as diluents for this waxy paraffin. Therefore, the nC18 content of the RD blends diluted with 50% and 75% oligomeric isoparaffins is expected to be 4.2% nC18 (= 0.5 × 8.4%) and 2.1% nC18 (= 0.25 × 8.4%). If the oligomeric isoparaffin blends behaved like typical RDs with varying degrees of isomerization, the cloud points of the blends would be -20.7 °C and -31.5 °C, respectively, as predicted by Equation 6. However, these blends exhibit surprisingly low cloud points of -29 °C and -37 °C, or cloud points approximately 6 to 8 °C lower.

[0070] The derived cetane numbers in Table I are well above the minimum specification limits for diesel fuel of 40 (ASTM D975) and 49 (EN 590), despite the very low cetane numbers of the highly branched isobutene oligomerization products.

[0071] Example 4. Blends of oligomeric isoparaffins and HDO paraffins The cloud point of the stripped, unisomerized HDO product (produced according to the HDO conditions described in Example 1) was measured and found to be greater than 20° C. This HDO product was blended with the oligomeric isoparaffins of Example 2. Three blends were prepared with varying ratios of oligomeric isoparaffins to HDO product. The cloud points of the three blends are shown in Table II.

[0072] [Table II]

[0073] The results suggest that the bio-based hydrocarbons, including the HDO products and isoparaffin oligomers, are suitable for use as diesel fuels for climates where the 10th percentile minimum temperature (as set forth in ASTM D975 Section X5) is above 10° C. (50 / 50 blend) or above 0° C. (75 / 25 blend). Such fuels can be produced by HDO using a feedstock comprising olefin oligomers as described in this disclosure.

[0074] While the present invention has been described in relation to its preferred embodiments, it will be apparent to those skilled in the art that various modifications can be made to the preferred embodiments described herein without departing from the spirit and scope of the invention. However, all such modifications and variations apparent to those skilled in the art are intended to be included within the scope of the following claims.

Claims

1. 1. A method for producing a biomass-based diesel fuel, comprising: a. producing paraffins by hydrodeoxygenation of a lipid feedstock; b. A process for producing isoparaffins from sugars, comprising: i. fermenting the sugars to alcohol; ii. Dehydrating the alcohol to an olefin; iii. Oligomerizing the olefins to a distribution of isoolefins; and iv. Hydrogenating the isoolefins to isoparaffins producing isoparaffins by c) blending the paraffins and the isoparaffins to produce the biomass-based diesel fuel; d. the isoparaffins have a derived cetane number (DCN) of less than 40; e. The method, wherein the biomass-based diesel fuel has a DCN of 49 or greater.

2. 10. The method of claim 1, wherein the biomass-based diesel fuel has a DCN greater than 55.

3. 10. The method of claim 1, wherein the biomass-based diesel fuel has a cloud point below 0°C.

4. 10. The method of claim 1, wherein the biomass-based diesel fuel has a cloud point below -10°C.

5. 2. The method of claim 1, wherein the alcohol is ethanol or isobutanol.

6. 2. The process of claim 1, wherein the olefin is propylene or butene.

7. 10. A biomass-based diesel fuel product produced by the method of claim 1.

8. 1. A method for producing renewable diesel fuel, comprising: a. combining lipids with a hydrocarbon liquid to obtain a composite feedstock; b. hydrodeoxygenating and hydrogenating the composite feedstock in a hydrodeoxygenation reactor to obtain a reactor effluent comprising C3 to C24 hydrocarbons; c) separating a C9 to C24 hydrocarbon fraction from the reactor effluent; the C9 to C24 hydrocarbon fraction has a derived cetane number of 49 or greater and a cloud point of less than 0°C; The method wherein the hydrocarbon liquid comprises an isoolefin produced by olefin oligomerization.

9. 9. The process of claim 8, further comprising producing the isoolefin by oligomerization of isobutene.

10. 10. The method of claim 9, wherein the isobutene is a dehydration product of isobutanol.

11. 11. The method of claim 10, further comprising preparing the isobutanol by fermentation of sugars.

12. 10. The method of claim 9, further comprising producing the isoolefin by oligomerization of propylene.

13. 13. The process of claim 12, wherein the propylene is the product of propane dehydrogenation.

14. 9. The method of claim 8, wherein the product from the hydrodeoxygenation reaction is not used as a diluent in a reactor feed.

15. 1. A method for producing renewable diesel fuel, comprising: a. combining lipids with a hydrocarbon liquid to obtain a composite feedstock; b. hydrodeoxygenating and hydrogenating said composite feedstock in a hydrodeoxygenation reactor to obtain a reactor effluent comprising hydrocarbons, said hydrocarbons comprising propane co-product; c) separating a C9 to C24 hydrocarbon fraction from the reactor effluent; d. dehydrogenating the propane co-product to produce a vapor stream comprising propylene and hydrogen; e. oligomerizing the propylene to form isoolefins; The method wherein said C9 to C24 hydrocarbon fraction has a derived cetane number of 49 or greater and said hydrocarbon liquid comprises said isoolefin.

16. 16. The method of claim 15, further comprising producing the isoolefin by oligomerization of butenes.

17. 17. The process of claim 16, wherein the butenes are derived from ethanol and / or isobutanol.

18. 10. The method of claim 9, further comprising producing the isoolefin by oligomerization of propylene.

19. 9. The method of claim 8, wherein the product from the hydrodeoxygenation reaction is not used as a diluent in a reactor feed.

20. 16. The method of claim 15, wherein the C9 to C24 hydrocarbon fraction is distilled to obtain a C9 to C15 fraction kerosene.

21. 21. The method of claim 20, wherein the C9 to C15 fraction kerosene is used as a jet fuel blendstock.

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