Method for producing low freezing point hydrocarbon bio-diesel by hydrogenation of oil

Abstract

The application discloses a method for producing low-freezing hydrocarbon biodiesel by oil hydrogenation, and belongs to the technical field of biomass renewable energy. The method comprises the following steps: oil and hydrogen enter a hydrogenation deoxidization unit to react, and then the product is separated by an oil-water-gas separation unit to obtain mixed long-chain normal alkanes; the mixed long-chain normal alkanes are sequentially introduced into a hydrogenation isomerization unit to be converted, and then the product is separated by a fractionation unit to obtain bio-naphtha and hydrocarbon biodiesel. In the hydrogenation deoxidization unit, a graded water-resistant hydrogenation catalyst is used, and in the hydrogenation isomerization unit, a deep hydrogenation isomerization catalyst is used. In addition, part of the mixed long-chain normal alkanes produced by the hydrogenation deoxidization unit is recycled to the hydrogenation deoxidization unit. By using the high-efficiency catalyst and process, the application relieves the reaction heat release in the hydrogenation deoxidization unit, maintains the long-period activity of the catalyst, realizes efficient hydrogenation deoxidization of the oil, inhibits cracking in the hydrogenation isomerization unit, realizes deep hydrogenation isomerization of the mixed normal alkanes, and realizes stable and high-yield production of low-freezing hydrocarbon biodiesel in the whole process.

Description

Technical Field

[0001] This application relates to a method for producing low-pour-point hydrocarbon biodiesel by hydrogenating oils and fats, belonging to the field of biomass renewable energy technology. Background Technology

[0002] With continuous economic and social development, the dwindling availability of primary energy sources such as oil and coal has led to energy shortages, causing crude oil and coal prices to rise steadily in recent years, which has also impacted motor fuel prices. Furthermore, since both oil and coal are carbon-containing resources and contain elements such as nitrogen and sulfur, their conversion and the use of their products inevitably produce carbon dioxide and other toxic gases harmful to the environment. These factors have prompted researchers to seek new energy alternatives to fossil fuels. Biomass energy is the only naturally occurring carbon-containing renewable energy source. The carbon dioxide produced during its utilization can be consumed through plant photosynthesis, causing minimal environmental impact. From this perspective, developing production technologies for biomass-based liquid fuels such as biodiesel and bio-aviation kerosene is of great significance for environmental protection, adapting to the current energy consumption structure, and maintaining national energy security.

[0003] Hydrocarbon biodiesel is a type of renewable liquid fuel produced by converting biomass feedstocks into long-chain alkanes. Its chemical composition is highly similar to traditional petroleum diesel, and it can be used directly as a substitute for or blended with fossil diesel. Compared to first-generation fatty acid methyl ester (FAME) biodiesel, hydrocarbon biodiesel (such as hydrogenated vegetable oil HVO and biosynthesized paraffinic diesel) has higher oxidation stability, lower temperature fluidity, and higher energy density. It is also fully compatible with existing diesel engines and distribution systems, and is considered a more competitive second-generation biofuel.

[0004] Biomass containing fatty acid glycerides, fatty acid esters, and fatty acids, such as animal and vegetable oils, can be directly converted into hydrocarbon compounds through hydrogenation and deoxygenation. The fatty acid chains in animal and vegetable oils have 12–24 carbon atoms (most commonly 16 and 18). After complete hydrogenation and deoxygenation, they mainly produce alkanes with 11–24 carbon atoms, similar in carbon chain length to those found in petrochemical jet fuel and diesel fuel. However, the carbon chains generated after direct hydrogenation and deoxygenation... 11 ~C 24 n-Alkanes have high freezing points and cannot be used directly as liquid fuels. These hydrodeoxygenation products must undergo a hydroisomerization process to convert n-alkanes into isoalkanes, thereby lowering their freezing points and improving their low-temperature performance (for example, heptadecane has a freezing point of approximately 22°C, while one of the isomerization products, 3-methyl-hexadecane, has a freezing point of approximately -15°C), thus enabling them to be used as biodiesel.

[0005] The hydroconversion process of oils and fats is a strongly exothermic reaction. Taking soybean oil as an example, thermodynamic analysis of the reactions involved in the formation of isoalkanes from soybean oil shows that the total enthalpy changes are -1562 kJ / mol (hydrodeoxygenation), -1150 kJ / mol (hydrocarbonylation), and -1247 kJ / mol (hydrocarboxylation). If the heat cannot be removed in time during the reaction, the active metal components of the catalyst may sinter, significantly reducing the catalyst's lifespan. In the second step of hydroisomerization of deoxygenated oil, low-pour-point hydrocarbon biodiesel often requires a pour point below -35°C, necessitating deep isomerization. However, cracking is a sequential reaction following hydroisomerization. Therefore, avoiding excessive cracking while performing deep isomerization of deoxygenated oil is crucial for obtaining high-yield, high-quality low-pour-point hydrocarbon biodiesel. Thus, high-yield production of low-pour-point hydrocarbon biodiesel from oils and fats requires innovation in both catalysts and processes. Summary of the Invention

[0006] To address the challenges in existing technologies for producing low-pour-point hydrocarbon biodiesel via oil hydrogenation, which struggle to balance service life, efficient deep hydrodeoxygenation, and hydroisomerization, this application proposes a highly efficient technical solution for producing low-pour-point hydrocarbon biodiesel via oil hydrogenation.

[0007] The technical solution adopted in this application is as follows:

[0008] According to a first aspect of this application, a method for producing low-pour-point hydrocarbon biodiesel by hydrogenating oils and fats is provided, characterized by comprising the following steps:

[0009] S1. A mixture containing oil raw materials and hydrogen is passed into a hydrodeoxygenation reaction unit to carry out a hydrodeoxygenation reaction, generating mixed product I;

[0010] The hydrodeoxygenation reaction unit includes a hydrodeoxygenation reactor.

[0011] The hydrodeoxygenation reactor includes six catalyst beds, each filled with an active metal-supported hydrodeoxygenation catalyst, and the loading of active metal on the hydrodeoxygenation catalyst in each catalyst bed increases sequentially along the direction of mixture flow.

[0012] S2. The mixed product I is fed into an oil-water-gas separation unit to separate hydrogen I, gaseous hydrocarbons, hydrogen sulfide, carbon monoxide, carbon dioxide, water and mixed long-chain n-alkanes.

[0013] S3. The mixture of the mixed long-chain n-alkane and hydrogen is passed into the hydroisomerization reaction unit to carry out the hydroisomerization reaction and generate mixed product II;

[0014] The hydroisomerization reaction unit includes one hydroisomerization reactor, which is filled with a deep hydroisomerization catalyst.

[0015] S4. The mixed product II is fed into the gas-liquid separation unit to separate hydrogen II, liquefied gas and mixed long-chain isoalkanes;

[0016] S5. The mixed long-chain isoalkanes are fed into the fractionation unit and precisely fractionated according to the distillation range to obtain bio-naphtha and low-pour-point hydrocarbon biodiesel.

[0017] Optionally, in step S1, the oil raw material is at least one of animal or vegetable oils and waste cooking oil;

[0018] The animal and vegetable oils are selected from at least one of soybean oil, peanut oil, olive oil, corn oil, rapeseed oil, almond oil, sunflower seed oil, palm oil, acidified palm oil, cottonseed oil, coconut oil, rice bran oil, jatropha oil, saxifrage oil, microalgae oil, lard, beef tallow, chicken fat, and mutton fat.

[0019] Optionally, the waste cooking oil is used as an oil raw material after being processed through processes such as filtration, electro-desalination, particle adsorption, static stratification and dehydration to remove mechanical impurities, chlorine, metals and water.

[0020] Optionally, in step S1, the oil raw material further includes a vulcanizing agent.

[0021] Optionally, the vulcanizing agent is carbon disulfide and / or dimethyl disulfide.

[0022] Optionally, the content of carbon disulfide and / or dimethyl disulfide in the oil raw material is 0.02 wt% to 0.5 wt%.

[0023] Optionally, in step S1, the active metal-supported hydrodeoxygenation catalyst includes an inorganic heat-resistant oxide support and a non-precious metal supported on the inorganic heat-resistant oxide support.

[0024] The active metal is selected from at least one of Ni, Co, Mo, and W;

[0025] The inorganic heat-resistant oxide is selected from at least one of aluminum oxide, silicon oxide, zirconium oxide, titanium oxide, zinc oxide, and manganese oxide.

[0026] Optionally, the inorganic heat-resistant oxide is aluminum oxide and / or silicon oxide.

[0027] Optionally, the active metal-supported hydrodeoxygenation catalyst further includes an auxiliary metal supported on the inorganic heat-resistant oxide support, wherein the auxiliary metal is selected from at least one of Fe, Zn, Si, Ce, P, Ca, K, and Mg.

[0028] Optionally, the active metal-supported hydrodeoxygenation catalyst is a graded water-resistant hydrodeoxygenation catalyst, in which the oil feedstock and hydrogen undergo hydrosaturation and hydrodeoxygenation reactions on multiple bed-graded catalysts.

[0029] Optionally, the six catalyst beds in the multi-bed gradation are sequentially filled with hydrogenation catalyst A, hydrogenation catalyst B, hydrogenation catalyst C, hydrogenation catalyst D, hydrogenation catalyst E, and hydrogenation catalyst F;

[0030] In hydrodeoxygenation catalyst A, the active metal loading is 1 wt% to 4 wt%;

[0031] In hydrodeoxygenation catalyst B, the active metal loading is 4wt% to 8wt%.

[0032] In hydrodeoxygenation catalyst C, the active metal loading is 8wt% to 12wt%.

[0033] In hydrodeoxygenation catalyst D, the active metal loading is 12wt% to 16wt%.

[0034] In hydrodeoxygenation catalyst E, the active metal loading is 16 wt% to 21 wt%.

[0035] In the hydrodeoxygenation catalyst F, the active metal loading is 21 wt% to 40 wt%.

[0036] Optionally, the loading of the promoter metal in the active metal supported hydrodeoxygenation catalyst is 1 wt% to 10 wt%.

[0037] Optionally, in step S1, the loading amount of hydrogenation catalyst in the hydrodeoxygenation reactor, distributed according to bed height, is:

[0038] Hydrodeoxygenation catalyst A, with a loading amount of 0% to 15%;

[0039] Hydrodeoxygenation catalyst B, with a loading amount of 0% to 20%;

[0040] Hydrodeoxygenation catalyst C, with a loading amount of 0% to 50%;

[0041] Hydrodeoxygenation catalyst D, with a loading amount of 0% to 50%;

[0042] Hydrodeoxygenation catalyst E, with a loading amount of 0% to 40%;

[0043] Hydrodeoxygenation catalyst F, with a loading of 0% to 40%.

[0044] Optionally, the hydrodeoxygenation reactor is a fixed-bed reactor.

[0045] A multi-bed gradation hydrodeoxygenation catalyst can be located in a single hydrodeoxygenation reactor or in multiple reactors connected in series.

[0046] Optionally, the hydrodeoxygenation reaction unit includes a first hydrodeoxygenation reactor and a second hydrodeoxygenation reactor arranged in series, wherein the first hydrodeoxygenation reactor is filled with hydrodeoxygenation catalyst A, hydrodeoxygenation catalyst B, and hydrodeoxygenation catalyst C, and the second hydrodeoxygenation reactor is filled with hydrodeoxygenation catalyst D, hydrodeoxygenation catalyst E, and hydrodeoxygenation catalyst F.

[0047] Optionally, in step S1, the conditions for the hydrodeoxygenation reaction include: a reaction temperature of 200℃~400℃, a pressure of 2.0MPa~8.0MPa, and a feed volume hourly space velocity of 0.2h. -1 ~2.0h -1 The hydrogen-to-oil ratio is 200:1 to 2000:1.

[0048] Optionally, in step S1, the temperature of each catalyst bed in the hydrodeoxygenation reactor increases in a gradient.

[0049] Alternatively, the conditions for the hydrodeoxygenation reaction include:

[0050] The temperature of the catalyst bed containing hydrodeoxygenation catalyst A is 200℃~240℃;

[0051] The temperature of the catalyst bed containing hydrodeoxygenation catalyst B is 220℃~260℃;

[0052] The temperature of the catalyst bed containing hydrodeoxygenation catalyst C is 240℃~280℃;

[0053] The temperature of the catalyst bed containing hydrodeoxygenation catalyst D is 260℃~340℃;

[0054] The temperature of the catalyst bed containing hydrodeoxygenation catalyst E is 280℃~360℃;

[0055] The temperature of the catalyst bed containing hydrodeoxygenation catalyst F is 280℃~400℃.

[0056] Optionally, in step S2, the mixed long-chain n-alkane is C 12 ~C 24 A mixture of n-alkanes;

[0057] Optionally, in step S3, a portion of the mixed long-chain n-alkanes is returned to the hydrodeoxygenation reaction unit in step S1 as a component of the mixture (mixed with fresh oil raw materials to continue the reaction), and another portion of the mixture of mixed long-chain n-alkanes and hydrogen is passed into the hydroisomerization reaction unit to carry out the hydroisomerization reaction, generating mixed product II;

[0058] Optionally, in step S3, the mass ratio of the mixed long-chain n-alkane to the oil raw material in the mixture is 1:2 to 10:1.

[0059] Optionally, in step S3, the mass ratio of the mixed long-chain n-alkane to the oil raw material in the mixture is 1:1 to 5:1.

[0060] Optionally, the oil-water-gas separation unit includes a gas-liquid separator I, an oil-water separator, and a stripping tower connected in series;

[0061] The mixed product I enters the gas-liquid separator I and is separated into hydrogen I, gaseous hydrocarbons, carbon monoxide, carbon dioxide and liquid product I. The hydrogen I is returned to the hydrodeoxygenation reaction unit in step S1 to replenish hydrogen (the hydrogen obtained after separation by the oil-water-gas separation unit is used as circulating hydrogen and mixed with new hydrogen before entering the hydrodeoxygenation unit). The liquid product I enters the oil-water separator to separate water and then enters the stripping tower to separate hydrogen sulfide and mixed long-chain n-alkanes.

[0062] Optionally, in step S3, the deep hydroisomerization catalyst is a catalyst with a noble metal supported on a molecular sieve.

[0063] The molecular sieve is selected from at least one of the molecular sieves having the structures AEL, AFO, AFI, ATO, *BEA, *MRE, MTT, MTW, and TON.

[0064] The precious metal is selected from at least one of Pt, Pd, and Ir;

[0065] The molecular sieve is also loaded with an auxiliary metal, which is selected from at least one of K, Ca, Na, Mg, Al, Cu, Fe, Sn, Zn, Ba, and Ce.

[0066] Optionally, the loading of the auxiliary metal on the molecular sieve is 0 wt% to 20 wt%.

[0067] Optionally, the molecular sieve with the AEL type structure is one or more of SAPO-11 and MeAPO-11 (Me = one or more of Zn, Mg, Mn, Co, Cr, Cu, Cd or Ni, with a mass content of 0.05 to 5 wt.%).

[0068] Optionally, the molecular sieve with the AFO-type structure is one or more of SAPO-41 and MeAPO-41 (Me = one or more of Zn, Mg, Mn, Co, Cr, Cu, Cd or Ni, with a mass content of 0.05 to 5 wt.%).

[0069] Optionally, the molecular sieve with the AFI type structure is one or more of SAPO-5 and MeAPO-5 (Me = one or more of Zn, Mg, Mn, Co, Cr, Cu, Cd or Ni, with a mass content of 0.05 to 5 wt.%).

[0070] Optionally, the molecular sieve with the ATO-type structure is one or more of SAPO-31 and MeAPO-31 (Me = one or more of Zn, Mg, Mn, Co, Cr, Cu, Cd or Ni, with a mass content of 0.05 to 5 wt.%).

[0071] Optionally, the molecular sieve with the *BEA type structure is one or more of BETA, Me-BETA (Me = one or more of Zn, Mg, Mn, Co, Cr, Cu, Fe, Cd or Ni), CIT-6, etc.

[0072] Optionally, the molecular sieve with the *MRE type structure is one or more of ZSM-48, Me-ZSM-48 (Me = one or more of Zn, Mg, Mn, Co, Cr, Cu, Fe, Cd or Ni).

[0073] Optionally, the molecular sieve with the MTT-type structure is one or more of ZSM-23, Me-ZSM-23 (Me = one or more of Zn, Mg, Mn, Co, Cr, Cu, Fe, Cd or Ni), EU-13, KZ-1 and ISI-4.

[0074] Optionally, the molecular sieve with the MTW type structure is one or more of ZSM-12, Me-ZSM-12 (Me = one or more of Zn, Mg, Mn, Co, Cr, Cu, Fe, Cd or Ni), NU-13, CZH-5, TPZ-12, VS-12, and Theta-3.

[0075] Optionally, the molecular sieve with the TON type structure is one or more of ZSM-22, Me-ZSM-22 (Me = one or more of Zn, Mg, Mn, Co, Cr, Cu, Fe, Cd or Ni), Theta-1, KZ-2, ISI-1 and NU-10.

[0076] Optionally, in step S3, the deep hydroisomerization catalyst is selected from at least one of hydroisomerization catalyst G, hydroisomerization catalyst H, and hydroisomerization catalyst I;

[0077] Optionally, in step S3, the acidity of the hydroisomerization catalyst G, hydroisomerization catalyst H, and hydroisomerization catalyst I increases sequentially.

[0078] Optionally, in the hydroisomerization catalyst G, the loading of noble metal is 0.1wt% to 0.3wt%, and the acidity is 0.8mmol(NH3) / g to 1.2mmol(NH3) / g;

[0079] In the hydroisomerization catalyst H, the loading of noble metals is 0.2wt% to 0.4wt%, and the acidity is 1.2mmol(NH3) / g to 1.6mmol(NH3) / g;

[0080] In hydroisomerization catalyst I, the loading of noble metals is 0.3wt% to 0.6wt%, and the acidity is 1.6mmol(NH3) / g to 2.0mmol(NH3) / g.

[0081] Optionally, in the hydroisomerization reactor, the loading amount of the hydroisomerization catalyst, distributed according to the bed height, is as follows:

[0082] In the hydroisomerization catalyst G, the loading amount is 0% to 100%;

[0083] The loading amount in hydroisomerization catalyst H is 0% to 100%;

[0084] In hydroisomerization catalyst I, the loading amount is 0% to 100%.

[0085] The three catalysts, G, H, and I, can be used individually or loaded in a certain proportion. Each hydrogen isomer catalyst can be located in a single hydrogen isomer reactor or in multiple hydrogen isomer reactors connected in series.

[0086] Optionally, the hydroisomerization reactor is a fixed-bed reactor.

[0087] Optionally, in the hydroisomerization reactor, a mixture of long-chain n-alkanes and hydrogen undergoes a hydroisomerization reaction on a multi-bed-graded hydroisomerization catalyst.

[0088] This application only limits the selection range or parameters of the catalyst support, loaded metal, and auxiliary metal used in the hydrodeoxygenation reactor and the hydroisomerization reactor. It does not strictly limit the preparation method of the catalyst. Those skilled in the art can prepare the catalyst or select commercial catalysts based on existing technology.

[0089] Optionally, key information about the catalysts used in the hydrodeoxygenation reactor and the hydroisomerization reactor is as follows:

[0090] (1) Hydrodeoxygenation catalyst A: Prepared by impregnation method. The catalyst consists of heat-resistant inorganic oxides alumina and / or silica as supports, one or more metals selected from Co, Ni, Mo and W supported on the supports, and one or more promoters selected from Fe, Zn, Si, Ce, P, Ca, K and Mg.

[0091] Preferably, based on the weight percentage of the catalyst, the total content of Co, Ni, Mo and W is 3 wt%, the total content of Fe, Zn, Si, Ce, P, Ca, K and Mg is 1.2 wt%, and the remainder is alumina and / or silicon oxide.

[0092] (2) Hydrodeoxygenation catalyst B: Prepared by impregnation method. The catalyst consists of heat-resistant inorganic oxides alumina and / or silica as a support, one or more metals selected from Co, Ni, Mo and W supported on the support, and one or more promoters selected from Fe, Zn, Si, Ce, P, Ca, K and Mg.

[0093] Preferably, based on the weight percentage of the catalyst, the total content of Co, Ni, Mo and W is 6 wt%, the total content of Fe, Zn, Si, Ce, P, Ca, K and Mg is 1.5 wt%, and the remainder is alumina and / or silicon oxide.

[0094] (3) Hydrodeoxygenation catalyst C: Prepared by impregnation method. The catalyst consists of heat-resistant inorganic oxides alumina and / or silica as supports, one or more metals selected from Co, Ni, Mo and W supported on the supports, and one or more promoters selected from Fe, Zn, Si, Ce, P, Ca, K and Mg.

[0095] Preferably, based on the weight percentage of the catalyst, the total content of Co, Ni, Mo and W is 10 wt%, the total content of Fe, Zn, Si, Ce, P, Ca, K and Mg is 1.8 wt%, and the remainder is alumina and / or silicon oxide.

[0096] (4) Hydrodeoxygenation catalyst D: Prepared by impregnation method. The catalyst consists of heat-resistant inorganic oxides alumina and / or silica as supports, one or more metals selected from Co, Ni, Mo and W supported on the supports, and one or more promoters selected from Fe, Zn, Si, Ce, P, Ca, K and Mg.

[0097] Preferably, based on the weight percentage of the catalyst, the total content of Co, Ni, Mo and W is 15 wt%, the total content of Fe, Zn, Si, Ce, P, Ca, K and Mg is 2.2 wt%, and the remainder is alumina and / or silicon oxide.

[0098] (5) Hydrodeoxygenation catalyst E: Prepared by impregnation method. The catalyst consists of heat-resistant inorganic oxides alumina and / or silica as supports, one or more metals selected from Co, Ni, Mo and W supported on the supports, and one or more promoters selected from Fe, Zn, Si, Ce, P, Ca, K and Mg.

[0099] Preferably, based on the weight percentage of the catalyst, the total content of Co, Ni, Mo and W is 18 wt%, the total content of Fe, Zn, Si, Ce, P, Ca, K and Mg is 3.0 wt%, and the remainder is alumina and / or silicon oxide.

[0100] (6) Hydrodeoxygenation catalyst F: Prepared by impregnation method. The catalyst consists of heat-resistant inorganic oxides alumina and / or silica as supports, one or more metals selected from Co, Ni, Mo and W supported on the supports, and one or more promoters selected from Fe, Zn, Si, Ce, P, Ca, K and Mg.

[0101] Preferably, based on the weight percentage of the catalyst, the total content of Co, Ni, Mo and W is 32 wt%, the total content of Fe, Zn, Si, Ce, P, Ca, K and Mg is 4.0 wt%, and the remainder is alumina and / or silicon oxide.

[0102] (7) Hydroisomerization catalyst G: Prepared by impregnation method. The catalyst consists of one or more molecular sieves selected from those with AEL, AFO, AFI, ATO, *BEA, *MRE, MTT, MTW, and TON structures as a support, and Pt, Pd, and Ir noble metals supported thereon, as well as K, Ca, Na, Mg, Al, Cu, Fe, Sn, Zn, Ba, and Ce promoters.

[0103] Preferably, the precious metal content is 0.15 wt%, the additive content is 0.2 wt%, and the remainder is a molecular sieve support. The catalyst acidity is 1.0 mmol (NH3) / g.

[0104] (8) Hydroisomerization catalyst H: Prepared by impregnation method. The catalyst consists of one or more molecular sieves selected from those with AEL, AFO, AFI, ATO, *BEA, *MRE, MTT, MTW, and TON structures as a support, and Pt, Pd, and Ir noble metals supported thereon, as well as K, Ca, Na, Mg, Al, Cu, Fe, Sn, Zn, Ba, and Ce promoters.

[0105] Preferably, the precious metal content is 0.30 wt%, the additive content is 1.5 wt%, and the remainder is a molecular sieve support. The catalyst acidity is 1.5 mmol (NH3) / g.

[0106] (9) Hydroisomerization catalyst I: Prepared by impregnation method. The catalyst consists of one or more molecular sieves selected from those with AEL, AFO, AFI, ATO, *BEA, *MRE, MTT, MTW, and TON structures as a support, and Pt, Pd, and Ir noble metals supported thereon, as well as K, Ca, Na, Mg, Al, Cu, Fe, Sn, Zn, Ba, and Ce promoters.

[0107] Preferably, the precious metal content is 0.45 wt%, the additive content is 3.2 wt%, and the remainder is a molecular sieve support. The catalyst acidity is 1.8 mmol (NH3) / g.

[0108] Optionally, in step S3, the conditions for the hydroisomerization reaction include: a reaction temperature of 260℃~420℃, a pressure of 1.0MPa~8.0MPa, and a feed volume hourly space velocity of 0.2h. -1 ~3.0h -1 The hydrogen-to-oil ratio is 200:1 to 2000:1.

[0109] Optionally, in step S4, the gas-liquid separation unit includes a gas-liquid separator. The mixed product II enters the gas-liquid separator and is separated to obtain hydrogen II, liquefied gas, and mixed long-chain isoparaffins. The hydrogen II is returned to the hydroisomerization reaction unit in step S3 to replenish hydrogen. A portion of the gas obtained after separation by the gas-liquid separation unit is discharged to the pipeline network as exhaust gas.

[0110] Optionally, in steps S1 and S4, the oil feedstock and hydrogen, as well as the mixed long-chain n-alkanes and hydrogen, are all mixed in a preheater.

[0111] Optionally, in step S5, the fractionation unit performs precision fractionation of the mixed long-chain isoalkanes according to the distillation range of <150℃ and >150℃ to obtain bio-naphtha with a <150℃ fraction and low-pour-point hydrocarbon biodiesel with a >150℃ fraction.

[0112] Optionally, in step S5, the fractionation unit is a fractionation column and / or a distillation column.

[0113] Optionally, in step S5, the fractionation unit includes one or more fractionation towers.

[0114] Optionally, in step S5, the fractionation unit includes one or more distillation columns.

[0115] The low-pour-point hydrocarbon biodiesel (>150℃ fraction) separated in step S5 is taken as the main product and bio-naphtha (<150℃ fraction) is taken as a by-product and exits the unit.

[0116] Optionally, based on the amount of fresh oilseed feedstock in step S1, the yield of low-pour-point hydrocarbon biodiesel in step S5 is greater than 70%.

[0117] Optionally, based on the amount of fresh oilseed feedstock in step S1, the yield of low-pour-point hydrocarbon biodiesel in step S5 is greater than 80%.

[0118] Optionally, the low-pour-point hydrocarbon biodiesel in step S5 has a pour point below -35°C and other properties that meet the standards of ASTM D975-20a and GB 19174-2016.

[0119] The beneficial effects of this application include:

[0120] (1) This application provides a highly efficient hydrodeoxygenation catalyst and its gradation method, and provides a process for segmented temperature control of the catalyst bed to achieve graded conversion of oils;

[0121] (2) This application alleviates the exothermic reaction in the hydrodeoxygenation unit, maintains the long-term activity of the catalyst, and achieves efficient hydrodeoxygenation of oils and fats;

[0122] (3) This application provides a highly efficient deep hydroisomerization catalyst that suppresses excessive cracking in the hydroisomerization unit and realizes deep hydroisomerization of mixed n-alkanes;

[0123] (4) The entire process of this application can achieve stable and high-yield production of low-condensation hydrocarbon biodiesel. Attached Figure Description

[0124] Figure 1 This is a process flow diagram for producing low-pour-point hydrocarbon biodiesel by hydrogenation of oils and fats, as described in this application.

[0125] Figure 2 This is another process flow diagram for the hydrogenation of oils to produce low-pour-point hydrocarbon biodiesel according to this application. Detailed Implementation

[0126] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0127] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0128] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0129] The term "grease" as used in this application is a general term for oils and fats, including any oily and fatty substances. The term "hydrocarbon" as used in this application refers to an organic compound composed essentially of hydrogen and carbon atoms; the target hydrocarbon product described in this application is composed entirely of hydrogen and carbon atoms. The term "liquid hydrocarbon" as used in this application refers to hydrocarbons that are liquid under the reaction or separation conditions described in this application; the boiling point of the liquid hydrocarbon described in this application refers to its boiling point under normal pressure.

[0130] The target product described in this application, hydrocarbon biodiesel, is composed of hydrocarbons. The target product, hydrocarbon biodiesel, refers to a liquid hydrocarbon product with a boiling point higher than 150°C.

[0131] In some embodiments, the gaseous phase of the reaction products of this application includes unreacted hydrogen and gaseous hydrocarbons with fewer than 5 carbon atoms.

[0132] The hydrodeoxygenation unit described in this application refers to the reaction unit in which fats and oils undergo hydrogenation and the removal of skeletal oxygen. The main components of fats and oils include unsaturated fatty acid glycerides, saturated fatty acid glycerides, and free fatty acids. Therefore, the specific reactions that occur include the hydrogenation saturation of C=C unsaturated bonds in the fat and oil molecules, the deoxygenation of ester groups (including three mechanisms: hydrodeoxygenation, decarboxylation, and decarbonylation), and the deoxygenation of carboxyl groups (including three mechanisms: hydrodeoxygenation, decarboxylation, and decarbonylation). The main chemical reaction equations are as follows:

[0133]

[0134] The hydroisomerization unit described in this application refers to the reaction unit in which the mixed n-alkanes generated from the hydrodeoxygenation unit of fats and oils continue to undergo hydroisomerization. The main chemical reaction equations are as follows:

[0135]

[0136] In some embodiments, the feed is added at a specific liquid hourly space velocity (LHSV) during the reaction steps of this application. The liquid hourly space velocity (LHSV) described in this application can be calculated using the following formula:

[0137]

[0138] The term "yield of hydrocarbon products" used in this application A It can be calculated using the following formula:

[0139]

[0140] In the above formula, "A" represents the hydrocarbon components collected by the oil-water-gas separation unit or the fractionation unit.

[0141] The performance analysis of hydrocarbon biodiesel in this application adopts national and industry standards, as detailed below:

[0142]

[0143] In the embodiments of this application, percentage / fraction refers to mass percentage / weight fraction, i.e., wt%, and temperature is expressed in degrees Celsius.

[0144] In this embodiment of the application, the process flow for producing low-pour-point hydrocarbon biodiesel by hydrogenation of oils is as follows: Figure 1 As shown, the system used in the process includes a hydrodeoxygenation reaction unit, an oil-water-gas separation unit, a hydroisomerization unit, a gas-liquid separation unit, and a fractionation unit arranged in series.

[0145] The hydrodeoxygenation reaction unit includes one hydrodeoxygenation reactor or two hydrodeoxygenation reactors arranged in series. Figure 2 The oil-water-gas separation unit includes a gas-liquid separator, an oil-water separator, and a stripping tower arranged in series; the hydroisomerization unit includes a hydroisomerization reactor; the gas-liquid separation unit includes a gas-liquid separator arranged in series; and the separation unit includes a fractionation tower.

[0146] The process for producing low-pour-point hydrocarbon biodiesel through oil hydrotreating involves mixing fresh oil and hydrogen at a specific hydrogen-to-oil ratio in a preheater before feeding them into a hydrodeoxygenation reactor. The mixture passes through multiple beds (each filled with a hydrodeoxygenation catalyst containing different active components). The reaction products are then fed into a gas-liquid separator to separate the gas phase (hydrogen, gaseous hydrocarbons, hydrogen sulfide, carbon monoxide, and carbon dioxide). The hydrogen is recycled back into the hydrodeoxygenation reactor. The separated liquid phase is fed into an oil-water separator to separate water, and the oil phase is fed into a stripping tower to separate hydrogen sulfide and mixed long-chain n-alkanes. A portion of the mixed long-chain n-alkanes is recycled back into the reactor. The mixture is fed into a hydrodeoxygenation reactor and mixed with fresh oil as feed for the hydrodeoxygenation reaction unit. The remaining mixed long-chain n-alkanes and hydrogen are fed into a hydroisomerization reactor (the reactor is filled with at least one hydroisomerization catalyst) at a certain hydrogen-to-oil ratio. The reaction products are fed into a gas-liquid separator to separate the gas phase (hydrogen and liquefied gas) and the liquid phase (mixed long-chain isoalkanes). The hydrogen is recycled back to the hydrodeoxygenation reactor, and the mixed long-chain isoalkanes enter a fractionation tower to be cut according to the distillation range of <150℃ and >150℃ to obtain bio-naphtha (<150℃ fraction) and low-pour-point hydrocarbon biodiesel (>150℃ fraction).

[0147] Key information regarding the catalysts used in the hydrodeoxygenation reactor and the hydroisomerization reactor is as follows:

[0148] (1) Hydrodeoxygenation catalyst A: Prepared by impregnation method. The catalyst consists of heat-resistant inorganic oxides alumina and / or silica as a support, one or more metals selected from Co, Ni, Mo, and W supported on the support, and one or more promoters selected from Fe, Zn, Si, Ce, P, Ca, K, and Mg. Based on the weight percentage of the catalyst, the total content of Co, Ni, Mo, and W is 3 wt%, the total content of Fe, Zn, Si, Ce, P, Ca, K, and Mg is 1.2 wt%, and the remainder is alumina and / or silica. In the embodiments of this application, the hydrodeoxygenation catalyst A is 1 wt% Ni - 2 wt% Mo - 0.5 wt% Ce - 0.7 wt% P / Al2O3.

[0149] (2) Hydrodeoxygenation catalyst B: Prepared by impregnation method. The catalyst consists of heat-resistant inorganic oxides alumina and / or silica as a support, one or more metals selected from Co, Ni, Mo, and W supported on the support, and one or more promoters selected from Fe, Zn, Si, Ce, P, Ca, K, and Mg. Based on the weight percentage of the catalyst, the total content of Co, Ni, Mo, and W is 6 wt%, the total content of Fe, Zn, Si, Ce, P, Ca, K, and Mg is 1.5 wt%, and the remainder is alumina and / or silica. In the embodiments of this application, the hydrodeoxygenation catalyst B is 2 wt% Ni - 4 wt% Mo - 0.5 wt% Ce - 1 wt% P / Al2O3.

[0150] (3) Hydrodeoxygenation catalyst C: Prepared by impregnation method. The catalyst consists of heat-resistant inorganic oxides alumina and / or silica as a support, one or more metals selected from Co, Ni, Mo, and W supported on the support, and one or more promoters selected from Fe, Zn, Si, Ce, P, Ca, K, and Mg. Based on the weight percentage of the catalyst, the total content of Co, Ni, Mo, and W is 10 wt%, the total content of Fe, Zn, Si, Ce, P, Ca, K, and Mg is 1.8 wt%, and the remainder is alumina and / or silica. In the embodiments of this application, the hydrodeoxygenation catalyst C is 2 wt% Ni - 4 wt% Mo - 4 wt% W - 0.5 wt% Ce - 1.3 wt% P / Al2O3.

[0151] (4) Hydrodeoxygenation catalyst D: Prepared by impregnation method. The catalyst consists of heat-resistant inorganic oxides alumina and / or silica as a support, one or more metals selected from Co, Ni, Mo, and W supported on the support, and one or more promoters selected from Fe, Zn, Si, Ce, P, Ca, K, and Mg. Based on the weight percentage of the catalyst, the total content of Co, Ni, Mo, and W is 15 wt%, the total content of Fe, Zn, Si, Ce, P, Ca, K, and Mg is 2.2 wt%, and the remainder is alumina and / or silica. In the embodiments of this application, the hydrodeoxygenation catalyst D is 3 wt% Ni - 8 wt% Mo - 4 wt% W - 0.6 wt% K - 1.6 wt% P / SiO2.

[0152] (5) Hydrodeoxygenation catalyst E: Prepared by impregnation method. The catalyst consists of heat-resistant inorganic oxides alumina and / or silica as a support, one or more metals selected from Co, Ni, Mo, and W supported on the support, and one or more promoters selected from Fe, Zn, Si, Ce, P, Ca, K, and Mg. Based on the weight percentage of the catalyst, the total content of Co, Ni, Mo, and W is 18 wt%, the total content of Fe, Zn, Si, Ce, P, Ca, K, and Mg is 3.0 wt%, and the remainder is alumina and / or silica. In the embodiments of this application, the hydrodeoxygenation catalyst E is 4 wt% Ni - 8 wt% Mo - 6 wt% W - 0.5 wt% Ce - 2.5 wt% P / Al2O3.

[0153] (6) Hydrodeoxygenation catalyst F: Prepared by impregnation method. The catalyst consists of heat-resistant inorganic oxides alumina and / or silica as a support, one or more metals selected from Co, Ni, Mo, and W supported on the support, and one or more promoters selected from Fe, Zn, Si, Ce, P, Ca, K, and Mg. Based on the weight percentage of the catalyst, the total content of Co, Ni, Mo, and W is 32 wt%, the total content of Fe, Zn, Si, Ce, P, Ca, K, and Mg is 4.0 wt%, and the remainder is alumina and / or silica. In the embodiments of this application, the hydrodeoxygenation catalyst F is 10 wt% Ni - 15 wt% Mo - 5% Co - 0.8 wt% Mg - 3.2 wt% P / Al2O3.

[0154] (7) Hydroisomerization catalyst G: Prepared by impregnation method. The catalyst consists of one or more molecular sieves selected from those having AEL, AFO, AFI, ATO, *BEA, *MRE, MTT, MTW, and TON structures as a support, and Pt, Pd, and Ir noble metals supported thereon, as well as K, Ca, Na, Mg, Al, Cu, Fe, Sn, Zn, Ba, and Ce promoters. The noble metal content is 0.15 wt%, the promoter content is 0.2 wt%, and the remainder is the molecular sieve support. The catalyst acidity is 1.0 mmol (NH3) / g. In the embodiments of this application, the hydroisomerization catalyst G is 0.15 wt% Pt-0.2 wt% K / SAPO-11 (having an AEL structure).

[0155] (8) Hydroisomerization catalyst H: Prepared by impregnation method. The catalyst consists of one or more molecular sieves selected from those having AEL, AFO, AFI, ATO, *BEA, *MRE, MTT, MTW, and TON structures as a support, and Pt, Pd, and Ir noble metals supported thereon, as well as K, Ca, Na, Mg, Al, Cu, Fe, Sn, Zn, Ba, and Ce promoters. The noble metal content is 0.30 wt%, the promoter content is 1.5 wt%, and the remainder is the molecular sieve support. The catalyst acidity is 1.5 mmol (NH3) / g. In the embodiments of this application, the hydroisomerization catalyst H is 0.3 wt% Pd-1.5 wt% Ce / ZSM-12 (with MTW structure).

[0156] (9) Hydroisomerization catalyst I: Prepared by impregnation method. The catalyst consists of one or more molecular sieves selected from those having AEL, AFO, AFI, ATO, *BEA, *MRE, MTT, MTW, and TON structures as a support, and Pt, Pd, and Ir noble metals supported thereon, as well as K, Ca, Na, Mg, Al, Cu, Fe, Sn, Zn, Ba, and Ce promoters. The noble metal content is 0.45 wt%, the promoter content is 3.2 wt%, and the remainder is the molecular sieve support. The catalyst acidity is 1.8 mmol (NH3) / g. In the embodiments of this application, the hydroisomerization catalyst I is 0.45 wt% Pt-3.0 wt% Ce-0.2 wt% Na / ZSM-23 (with MTT structure).

[0157] Example 1

[0158] Using waste cooking oil as raw material, low-pour-point hydrocarbon biodiesel is produced using the technology described in this application.

[0159] After removing mechanical impurities, chlorine, metals, and water, waste cooking oil was used as fresh feed. Its fatty acid composition was as follows: lauric acid (12:0, where 12 represents the number of carbon atoms and 0 represents the number of carbon-carbon unsaturated double bonds in the fatty acid) 0.1%, myristic acid (14:0) 0.1%, palmitic acid (16:0) 21.2%, stearic acid (18:0) 18.7%, oleic acid (18:1) 42.3%, linoleic acid (18:2) 11.2%, linolenic acid (18:3) 1.4%, arachidic acid (20:0) 1.3%, behenic acid (22:0) 2.5%, ligninic acid (24:0) 1.2%, total fatty acid ester content 99.9 wt%, free fatty acid content 0.1 wt%, and acid value 0.8 mg KOH / g. -1 The added carbon disulfide vulcanizing agent accounts for 0.1 wt% of the above-mentioned oil raw materials.

[0160] Two fixed-bed reactors are used as hydrodeoxygenation reactors in the hydrodeoxygenation reaction unit. Each hydrodeoxygenation reactor has three catalyst beds. The first hydrodeoxygenation reactor is filled with three types of hydrodeoxygenation catalysts, namely hydrodeoxygenation catalysts A, B, and C. The second hydrodeoxygenation reactor is filled with three types of hydrodeoxygenation catalysts, namely hydrodeoxygenation catalysts D, E, and F. The loading amounts of the six catalysts according to the bed height ratio are 5%, 12%, 18%, 20%, 30%, and 15 wt%, respectively.

[0161] The reaction pressure of the hydrodeoxygenation reactor is 4.0 MPa, and the feed volume hourly space velocity is 1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600:1, and the content of dimethyl disulfide in the oil raw material is 0.1 wt%.

[0162] The temperature of catalyst bed A in the hydrodeoxygenation reactor is 205℃;

[0163] The temperature of catalyst bed B in the hydrodeoxygenation reactor is 225℃;

[0164] The temperature of the C catalyst bed in the hydrodeoxygenation reactor is 245℃;

[0165] The temperature of catalyst bed D in the hydrodeoxygenation reactor is 310℃;

[0166] The temperature of the E catalyst bed in the hydrodeoxygenation reactor is 320℃;

[0167] The temperature of the F catalyst bed in the hydrodeoxygenation reactor is 325℃.

[0168] The mixed products generated in the hydrodeoxygenation reactor enter the oil-water-gas separation unit, where hydrogen, gaseous hydrocarbons, hydrogen sulfide, carbon monoxide, carbon dioxide, and water are separated to obtain mixed long-chain n-alkanes. Half of the mixed long-chain n-alkanes is returned to the hydrodeoxygenation reaction unit and mixed with fresh oil as feed for the hydrodeoxygenation reaction unit. The other half of the mixed long-chain n-alkanes enters the hydroisomerization unit for reaction.

[0169] Based on fresh oil feed, the yield of mixed long-chain n-alkanes is shown in Table 1, and the oil conversion rate after 1000 hours of operation is shown in Table 1.

[0170] In the hydroisomerization unit, a fixed-bed reactor is used as the hydroisomerization reactor, and two hydroisomerization catalysts, G and H, are loaded in a weight ratio of 50% and 50%, respectively.

[0171] The hydroisomerization reactor operates at a reaction pressure of 4.0 MPa, a reaction temperature of 318 °C, and a feed volume hourly space velocity of 1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 500:1.

[0172] The mixed products generated in the hydroisomerization reactor enter the gas-liquid separation unit, where hydrogen and gaseous hydrocarbons are separated to obtain mixed long-chain isoalkanes. The mixed long-chain isoalkanes then enter the fractionation unit, where they are cut according to boiling ranges of <150℃ and >150℃ to obtain bio-naphtha (<150℃ fraction) and low-pour-point hydrocarbon biodiesel (>150℃ fraction).

[0173] Based on mixed long-chain n-alkanes, the selectivity of low-pour-point hydrocarbon biodiesel is shown in Table 1.

[0174] Based on fresh oil feedstock, the yield of low-pour-point hydrocarbon biodiesel products is shown in Table 1, and the properties of low-pour-point hydrocarbon biodiesel products are shown in Table 2.

[0175] Example 2

[0176] Low-pour-point hydrocarbon biodiesel is produced using palm acidified oil as raw material and the technology described in this application.

[0177] Palm oil, after being treated to remove mechanical impurities, chlorine, metals, and water, is used as fresh feedstock. Its fatty acid composition is as follows: lauric acid (12:0, where 12 represents the number of carbon atoms and 0 represents the number of carbon-carbon unsaturated double bonds in the fatty acid) 0.1%, myristic acid (14:0) 0.7%, palmitic acid (16:0) 36.5%, stearic acid (18:0) 6.6%, oleic acid (18:1) 46.5%, linoleic acid (18:2) 8.6%, linolenic acid (18:3) 0.4%, arachidic acid (20:0) 0.4%, behenic acid (22:0) 0.1%, ligninic acid (24:0) 0.1%, total fatty acid ester content 98.8 wt%, free fatty acid content 1.2 wt%, and acid value 83 mg KOH / g. -1 The added carbon disulfide vulcanizing agent accounts for 0.1 wt% of the above-mentioned oil raw materials.

[0178] Two fixed-bed reactors are used as hydrodeoxygenation reactors in the hydrodeoxygenation reaction unit. Each hydrodeoxygenation reactor has three catalyst beds. The first hydrodeoxygenation reactor is filled with three types of hydrodeoxygenation catalysts, namely hydrodeoxygenation catalysts A, B, and C. The second hydrodeoxygenation reactor is filled with three types of hydrodeoxygenation catalysts, namely hydrodeoxygenation catalysts D, E, and F. The proportions of the six catalysts according to the bed height are 5%, 10%, 20%, 20%, 30%, and 15 wt%, respectively.

[0179] The reaction pressure of the hydrodeoxygenation reactor is 5.0 MPa, and the feed volume hourly space velocity is 1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600:1, and the content of dimethyl disulfide in the oil raw material is 0.1 wt%.

[0180] The temperature of catalyst bed A in the hydrodeoxygenation reactor is 206℃;

[0181] The temperature of catalyst bed B in the hydrodeoxygenation reactor is 228℃;

[0182] The temperature of the C catalyst bed in the hydrodeoxygenation reactor is 247℃;

[0183] The temperature of catalyst bed D in the hydrodeoxygenation reactor is 309℃;

[0184] The temperature of the E catalyst bed in the hydrodeoxygenation reactor is 318℃;

[0185] The temperature of the F catalyst bed in the hydrodeoxygenation reactor is 321℃.

[0186] The mixed products generated in the hydrodeoxygenation reactor enter the oil-water-gas separation unit, where hydrogen, gaseous hydrocarbons, hydrogen sulfide, carbon monoxide, carbon dioxide, and water are separated to obtain mixed long-chain n-alkanes. Half of the mixed long-chain n-alkanes is returned to the hydrodeoxygenation reaction unit and mixed with fresh oil as feed for the hydrodeoxygenation reaction unit. The other half of the mixed long-chain n-alkanes enters the hydroisomerization unit for reaction.

[0187] Based on fresh oil feed, the yield of mixed long-chain n-alkanes is shown in Table 1, and the oil conversion rate after 1000 hours of operation is shown in Table 1.

[0188] In the hydroisomerization unit, a fixed-bed reactor is used as the hydroisomerization reactor, and two hydroisomerization catalysts, H and I, are loaded, with the weight ratio of the two catalysts being 50% and 50%, respectively.

[0189] The hydroisomerization reactor operates at a reaction pressure of 4.0 MPa, a reaction temperature of 310 °C, and a feed volume hourly space velocity of 1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 500:1.

[0190] The mixed products generated in the hydroisomerization reactor enter the gas-liquid separation unit, where hydrogen and gaseous hydrocarbons are separated to obtain mixed long-chain isoalkanes. The mixed long-chain isoalkanes then enter the fractionation unit, where they are cut according to boiling ranges of <150℃ and >150℃ to obtain bio-naphtha (<150℃ fraction) and low-pour-point hydrocarbon biodiesel (>150℃ fraction).

[0191] Based on mixed long-chain n-alkanes, the selectivity of low-pour-point hydrocarbon biodiesel is shown in Table 1.

[0192] Based on fresh oil feedstock, the yield of low-pour-point hydrocarbon biodiesel products is shown in Table 1, and the properties of low-pour-point hydrocarbon biodiesel products are shown in Table 2.

[0193] Example 3

[0194] Low-pour-point hydrocarbon biodiesel is produced using cottonseed oil as raw material and the technology described in this application.

[0195] Cottonseed oil, after being cleaned of mechanical impurities, chlorine, metals, and water, was used as fresh feedstock. Its fatty acid composition was as follows: lauric acid (12:0, where 12 represents the number of carbon atoms and 0 represents the number of carbon-carbon unsaturated double bonds) was 0%, myristic acid (14:0) was 0.8%, palmitic acid (16:0) was 22.9%, stearic acid (18:0) was 3.6%, oleic acid (18:1) was 18.5%, linoleic acid (18:2) was 54.2%, linolenic acid (18:3) was 0%, arachidic acid (20:0) was 0%, total fatty acid ester content was 98.7 wt%, free fatty acid content was 1.3 wt%, and acid value was 85 mg KOH / g. -1 The added dimethyl disulfide vulcanizing agent accounts for 0.2 wt% of the above-mentioned oil raw materials.

[0196] Two fixed-bed reactors are used as hydrodeoxygenation reactors in the hydrodeoxygenation reaction unit. Each hydrodeoxygenation reactor has three catalyst beds. The first hydrodeoxygenation reactor is filled with three types of hydrodeoxygenation catalysts, namely hydrodeoxygenation catalysts A, B, and C. The second hydrodeoxygenation reactor is filled with three types of hydrodeoxygenation catalysts, namely hydrodeoxygenation catalysts D, E, and F. The proportions of the six catalysts according to the bed height are 5%, 15%, 25%, 20%, 20%, and 15 wt%, respectively.

[0197] The reaction pressure of the hydrodeoxygenation reactor is 5.0 MPa, and the feed volume hourly space velocity is 1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600:1, and the content of dimethyl disulfide in the oil raw material is 0.1 wt%.

[0198] The temperature of catalyst bed A in the hydrodeoxygenation reactor is 203℃;

[0199] The temperature of catalyst bed B in the hydrodeoxygenation reactor is 223℃;

[0200] The temperature of the C catalyst bed in the hydrodeoxygenation reactor is 242℃;

[0201] The temperature of catalyst bed D in the hydrodeoxygenation reactor is 308℃;

[0202] The temperature of the E catalyst bed in the hydrodeoxygenation reactor is 317℃;

[0203] The temperature of the F catalyst bed in the hydrodeoxygenation reactor is 321℃.

[0204] The mixed products generated in the hydrodeoxygenation reactor enter the oil-water-gas separation unit, where hydrogen, gaseous hydrocarbons, hydrogen sulfide, carbon monoxide, carbon dioxide, and water are separated to obtain mixed long-chain n-alkanes. Half of the mixed long-chain n-alkanes is returned to the hydrodeoxygenation reaction unit and mixed with fresh oil as feed for the hydrodeoxygenation reaction unit. The other half of the mixed long-chain n-alkanes enters the hydroisomerization unit for reaction.

[0205] Based on fresh oil feed, the yield of mixed long-chain n-alkanes is shown in Table 1, and the oil conversion rate after 1000 hours of operation is shown in Table 1.

[0206] In the hydroisomerization unit, a fixed-bed reactor is used as the hydroisomerization reactor, and three hydroisomerization catalysts G, H and I are loaded, with the weight ratios of the two catalysts being 30%, 40% and 40%, respectively.

[0207] The hydroisomerization reactor operates at a reaction pressure of 4.0 MPa, a reaction temperature of 315 °C, and a feed volume hourly space velocity of 1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 500:1.

[0208] The mixed products generated in the hydroisomerization reactor enter the gas-liquid separation unit, where hydrogen and gaseous hydrocarbons are separated to obtain mixed long-chain isoalkanes. The mixed long-chain isoalkanes then enter the fractionation unit, where they are cut according to boiling ranges of <150℃ and >150℃ to obtain bio-naphtha (<150℃ fraction) and low-pour-point hydrocarbon biodiesel (>150℃ fraction).

[0209] Based on mixed long-chain n-alkanes, the selectivity of low-pour-point hydrocarbon biodiesel is shown in Table 1.

[0210] Based on fresh oil feedstock, the yield of low-pour-point hydrocarbon biodiesel products is shown in Table 1, and the properties of low-pour-point hydrocarbon biodiesel products are shown in Table 2.

[0211] Comparative Example 1

[0212] Using the same raw materials as in Example 1, two fixed-bed reactors were used as hydrodeoxygenation reactors in the hydrodeoxygenation reaction unit. Each hydrodeoxygenation reactor had three catalyst beds, and each reactor was filled with only one type of catalyst, namely catalyst A.

[0213] The reaction pressure of the hydrodeoxygenation reactor is 5.0 MPa, and the feed volume hourly space velocity is 1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600:1, and the content of dimethyl disulfide in the oil raw material is 0.1 wt%.

[0214] The catalyst bed in the hydrodeoxygenation reactor is exothermic through cold hydrogen control, and the bed temperature is 348℃.

[0215] The mixed products generated in the hydrodeoxygenation reactor enter the oil-water-gas separation unit, where hydrogen, gaseous hydrocarbons, hydrogen sulfide, carbon monoxide, carbon dioxide, and water are separated to obtain mixed long-chain n-alkanes. Half of the mixed long-chain n-alkanes is returned to the hydrodeoxygenation reaction unit and mixed with fresh oil as feed for the hydrodeoxygenation reaction unit. The other half of the mixed long-chain n-alkanes enters the hydroisomerization unit for reaction.

[0216] Based on fresh oil feed, the yield of mixed long-chain n-alkanes is shown in Table 1, and the oil conversion rate after 1000 hours of operation is shown in Table 1.

[0217] In the hydroisomerization unit, a fixed-bed reactor is used as the hydroisomerization reactor, and only the hydroisomerization catalyst G is loaded.

[0218] The hydroisomerization reactor operates at a reaction pressure of 5.0 MPa, a reaction temperature of 320 °C, and a feed volume hourly space velocity of 1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 500:1.

[0219] The mixed products generated in the hydroisomerization reactor enter the gas-liquid separation unit, where hydrogen and gaseous hydrocarbons are separated to obtain mixed long-chain isoalkanes. The mixed long-chain isoalkanes then enter the fractionation unit, where they are cut according to boiling ranges of <150℃ and >150℃ to obtain bio-naphtha (<150℃ fraction) and low-pour-point hydrocarbon biodiesel (>150℃ fraction).

[0220] Based on mixed long-chain n-alkanes, the selectivity of low-pour-point hydrocarbon biodiesel is shown in Table 1.

[0221] Based on fresh oil feedstock, the yield of low-pour-point hydrocarbon biodiesel products is shown in Table 1, and the properties of low-pour-point hydrocarbon biodiesel products are shown in Table 2.

[0222] Comparative Example 2

[0223] Using the same raw materials as in Example 2, two fixed-bed reactors were used as hydrodeoxygenation reactors in the hydrodeoxygenation reaction unit. Each hydrodeoxygenation reactor had three catalyst beds, and each reactor was filled with only one type of catalyst, namely catalyst C.

[0224] The reaction pressure of the hydrodeoxygenation reactor is 5.0 MPa, and the feed volume hourly space velocity is 1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600:1, and the content of dimethyl disulfide in the oil raw material is 0.1 wt%.

[0225] The catalyst bed in the hydrodeoxygenation reactor is heat-released by cold hydrogen control, and the bed temperature is 338℃.

[0226] The mixed products generated in the hydrodeoxygenation reactor enter the oil-water-gas separation unit, where hydrogen, gaseous hydrocarbons, hydrogen sulfide, carbon monoxide, carbon dioxide, and water are separated to obtain mixed long-chain n-alkanes. The yields of the mixed long-chain n-alkanes based on fresh oil feed are shown in Table 1, and the oil conversion rate after 1000 hours of operation is also shown in Table 1.

[0227] In the hydroisomerization unit, a fixed-bed reactor is used as the hydroisomerization reactor, which contains three catalyst beds and is only filled with hydroisomerization catalyst H.

[0228] The hydroisomerization reactor operates at a reaction pressure of 5.0 MPa, a reaction temperature of 316 °C, and a feed volume hourly space velocity of 1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 500:1.

[0229] The mixed products generated in the hydroisomerization reactor enter the gas-liquid separation unit, where hydrogen and gaseous hydrocarbons are separated to obtain mixed long-chain isoalkanes. The mixed long-chain isoalkanes then enter the fractionation unit, where they are cut according to boiling ranges of <150℃ and >150℃ to obtain bio-naphtha (<150℃ fraction) and low-pour-point hydrocarbon biodiesel (>150℃ fraction).

[0230] Based on mixed long-chain n-alkanes, the selectivity of low-pour-point hydrocarbon biodiesel is shown in Table 1.

[0231] Based on fresh oil feedstock, the yield of low-pour-point hydrocarbon biodiesel products is shown in Table 1, and the properties of low-pour-point hydrocarbon biodiesel products are shown in Table 2.

[0232] Comparative Example 3

[0233] Using the same raw materials as in Example 3, two fixed-bed reactors were used as hydrodeoxygenation reactors in the hydrodeoxygenation reaction unit. Each hydrodeoxygenation reactor had three catalyst beds, and each reactor was filled with only one type of catalyst, namely catalyst E.

[0234] The reaction pressure of the hydrodeoxygenation reactor is 5.0 MPa, and the feed volume hourly space velocity is 1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600:1, and the content of dimethyl disulfide in the oil raw material is 0.1 wt%.

[0235] The catalyst bed in the hydrodeoxygenation reactor is heat-released by cold hydrogen control, and the bed temperature is 336℃.

[0236] The mixed products generated in the hydrodeoxygenation reactor enter the oil-water-gas separation unit, where hydrogen, gaseous hydrocarbons, hydrogen sulfide, carbon monoxide, carbon dioxide, and water are separated to obtain mixed long-chain n-alkanes. The yields of the mixed long-chain n-alkanes based on fresh oil feed are shown in Table 1, and the oil conversion rate after 1000 hours of operation is also shown in Table 1.

[0237] In the hydroisomerization unit, a fixed-bed reactor is used as the hydroisomerization reactor, which contains three catalyst beds and is only filled with hydroisomerization catalyst I.

[0238] The hydroisomerization reactor operates at a reaction pressure of 5.0 MPa, a reaction temperature of 313 °C, and a feed volume hourly space velocity of 1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600:1.

[0239] The mixed products generated in the hydroisomerization reactor enter the gas-liquid separation unit, where hydrogen and gaseous hydrocarbons are separated to obtain mixed long-chain isoalkanes. The mixed long-chain isoalkanes then enter the fractionation unit, where they are cut according to boiling ranges of <150℃ and >150℃ to obtain bio-naphtha (<150℃ fraction) and low-pour-point hydrocarbon biodiesel (>150℃ fraction).

[0240] Based on mixed long-chain n-alkanes, the selectivity of low-pour-point hydrocarbon biodiesel is shown in Table 1.

[0241] Based on fresh oil feedstock, the yield of low-pour-point hydrocarbon biodiesel products is shown in Table 1, and the properties of low-pour-point hydrocarbon biodiesel products are shown in Table 2.

[0242] Table 1. Yields of mixed long-chain n-alkanes, selectivity and yield of low-pour-point hydrocarbon biodiesel products.

[0243]

[0244] Table 2 Main Properties of Low-Pour-Out Hydrocarbon Biodiesel Products

[0245] Example Pour point (°C) Cold filter plugging point (°C) Flash point (°C) cetane number Density (g / mL) Example 1 -42 -35 62 75 0.776 Example 2 -40 -32 63 77 0.777 Example 3 -39 -31 64 78 0.778 Comparative Example 1 -40 -32 62 77 0.778 Comparative Example 2 -41 -33 61 77 0.776 Comparative Example 3 -39 -30 64 78 0.777

[0246] As shown in Tables 1 and 2, based on obtaining similar low-pour-point hydrocarbon biodiesel performance, the technology described in this application can achieve a higher yield of mixed long-chain n-alkane products in the hydrodeoxygenation stage. Furthermore, the process is stable, and the catalyst maintains good activity over a long period, with the oil conversion rate remaining at 100% after 1000 hours of operation. In the hydroisomerization stage, extremely high selectivity for low-pour-point hydrocarbon biodiesel can be obtained, exceeding the comparative example by more than 20 percentage points. The overall low-pour-point hydrocarbon biodiesel yield is above 80%, also exceeding the comparative example by more than 20 percentage points.

[0247] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for producing low-pour-point hydrocarbon biodiesel by hydrogenating oils and fats, characterized in that, Includes the following steps: S1. A mixture containing oil raw materials and hydrogen is passed into a hydrodeoxygenation reaction unit to carry out a hydrodeoxygenation reaction, generating mixed product I; The hydrodeoxygenation reaction unit includes a hydrodeoxygenation reactor; The hydrodeoxygenation reactor includes six catalyst beds, each filled with an active metal-supported hydrodeoxygenation catalyst, and the amount of active metal loaded on the hydrodeoxygenation catalyst in each catalyst bed increases sequentially along the direction of the mixture flow. S2. The mixed product I is fed into an oil-water-gas separation unit to separate hydrogen I, gaseous hydrocarbons, hydrogen sulfide, carbon monoxide, carbon dioxide, water and mixed long-chain n-alkanes. S3. The mixture of the mixed long-chain n-alkane and hydrogen is passed into the hydroisomerization reaction unit to carry out the hydroisomerization reaction and generate mixed product II; The hydroisomerization reaction unit includes one hydroisomerization reactor, which is filled with a deep hydroisomerization catalyst. S4. The mixed product II is fed into the gas-liquid separation unit to separate hydrogen II, liquefied gas and mixed long-chain isoalkanes; S5. The mixed long-chain isoalkanes are fed into the fractionation unit and precisely fractionated according to the distillation range to obtain bio-naphtha and low-pour-point hydrocarbon biodiesel.

2. The method according to claim 1, characterized in that, In step S1, the active metal-supported hydrodeoxygenation catalyst includes an inorganic heat-resistant oxide support and a non-precious metal supported on the inorganic heat-resistant oxide support. The active metal is selected from at least one of Ni, Co, Mo, and W; Preferably, the six catalyst beds are sequentially filled with hydrogenation catalyst A, hydrogenation catalyst B, hydrogenation catalyst C, hydrogenation catalyst D, hydrogenation catalyst E, and hydrogenation catalyst F; In hydrodeoxygenation catalyst A, the active metal loading is 1 wt% to 4 wt%; In hydrodeoxygenation catalyst B, the active metal loading is 4wt% to 8wt%. In hydrodeoxygenation catalyst C, the active metal loading is 8wt% to 12wt%. In hydrodeoxygenation catalyst D, the active metal loading is 12wt% to 16wt%. In hydrodeoxygenation catalyst E, the active metal loading is 16 wt% to 21 wt%. In the hydrodeoxygenation catalyst F, the active metal loading is 21 wt% to 40 wt%.

3. The method according to claim 2, characterized in that, In step S1, the loading amount of hydrogenation catalyst in the hydrodeoxygenation reactor, distributed according to bed height, is as follows: Hydrodeoxygenation catalyst A, with a loading amount of 0% to 15%; Hydrodeoxygenation catalyst B, with a loading amount of 0% to 20%; Hydrodeoxygenation catalyst C, with a loading amount of 0% to 50%; Hydrodeoxygenation catalyst D, with a loading amount of 0% to 50%; Hydrodeoxygenation catalyst E, with a loading amount of 0% to 40%; Hydrodeoxygenation catalyst F, with a loading of 0% to 40%.

4. The method according to claim 2, characterized in that, In step S1, the conditions for the hydrodeoxygenation reaction include: a reaction temperature of 200℃~400℃, a pressure of 2.0MPa~8.0MPa, and a feed volume hourly space velocity of 0.2h. -1 ~2.0h -1 The hydrogen-to-oil ratio is 200:1 to 2000:

1.

5. The method according to claim 4, characterized in that, The conditions for the hydrodeoxygenation reaction include: The temperature of the catalyst bed containing hydrodeoxygenation catalyst A is 200℃~240℃; The temperature of the catalyst bed containing hydrodeoxygenation catalyst B is 220℃~260℃; The temperature of the catalyst bed containing hydrodeoxygenation catalyst C is 240℃~280℃; The temperature of the catalyst bed containing hydrodeoxygenation catalyst D is 260℃~340℃; The temperature of the catalyst bed containing hydrodeoxygenation catalyst E is 280℃~360℃; The temperature of the catalyst bed containing hydrodeoxygenation catalyst F is 280℃~400℃.

6. The method according to claim 1, characterized in that, In step S2, the mixed long-chain n-alkane is C 12 ~C 24 A mixture of n-alkanes; Preferably, in step S3, a portion of the mixed long-chain n-alkanes is returned to the hydrodeoxygenation reaction unit in step S1 as a component of the mixture, and another portion of the mixture of mixed long-chain n-alkanes and hydrogen is introduced into the hydroisomerization reaction unit to carry out the hydroisomerization reaction, generating mixed product II; Preferably, in the mixture, the mass ratio of the mixed long-chain n-alkane to the oil raw material is 1:2 to 10:

1.

7. The method according to claim 1, characterized in that, In step S3, the deep hydroisomerization catalyst is a catalyst with noble metal supported on a molecular sieve; The molecular sieve is selected from at least one of the molecular sieves having the structures AEL, AFO, AFI, ATO, *BEA, *MRE, MTT, MTW, and TON. The precious metal is selected from at least one of Pt, Pd, and Ir; The molecular sieve is further loaded with an auxiliary metal, which is selected from at least one of K, Ca, Na, Mg, Al, Cu, Fe, Sn, Zn, Ba, and Ce. Preferably, the deep hydroisomerization catalyst is selected from at least one of hydroisomerization catalyst G, hydroisomerization catalyst H, and hydroisomerization catalyst I; Preferably, in the hydroisomerization catalyst G, the loading of noble metal is 0.1wt% to 0.3wt%, and the acidity is 0.8mmol(NH3) / g to 1.2mmol(NH3) / g; In the hydroisomerization catalyst H, the loading of noble metals is 0.2wt% to 0.4wt%, and the acidity is 1.2mmol(NH3) / g to 1.6mmol(NH3) / g; In hydroisomerization catalyst I, the loading of noble metals is 0.3wt% to 0.6wt%, and the acidity is 1.6mmol(NH3) / g to 2.0mmol(NH3) / g.

8. The method according to claim 7, characterized in that, In the hydroisomerization reactor, the loading amount of hydroisomerization catalyst, distributed according to bed height, is as follows: In the hydroisomerization catalyst G, the loading amount is 0% to 100%; The loading amount in hydroisomerization catalyst H is 0% to 100%; In hydroisomerization catalyst I, the loading amount is 0% to 100%.

9. The method according to claim 1, characterized in that, In step S3, the conditions for the hydroisomerization reaction include: a reaction temperature of 260℃~420℃, a pressure of 1.0MPa~8.0MPa, and a feed volume hourly space velocity of 0.2h. -1 ~3.0h -1 The hydrogen-to-oil ratio is 200:1 to 2000:

1.

10. The method according to claim 1, characterized in that, In step S5, the fractionation unit performs precision fractionation of mixed long-chain isoalkanes according to the distillation range of <150℃ and >150℃ to obtain bio-naphtha with a <150℃ fraction and low-pour-point hydrocarbon biodiesel with a >150℃ fraction.

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