A low pressure hydroisomerization / cracking process for the production of bio-based aviation fuels

Abstract

The application provides a low-pressure hydrogenation isomerization / cracking process for preparing bio-based aviation fuel and relates to the technical field of biomass energy. A three-stage hydrogenation process is adopted; in the first stage (1) and the second stage (2), a low-temperature and low-pressure homogeneous hydrogenation method combining an oil-soluble catalyst and a suspension bed reactor A and a suspension bed reactor B is adopted to perform low-cost hydrogenation upgrading pretreatment on high-silicon and high-metal biomass inferior grease; the middle stage is deep fixed bed hydrogenation refining; in order to improve the yield of light oil, a fixed bed hydrogenation isomerization reactor is additionally arranged in the rear stage to perform isomerization / cracking processing on heavy components.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass energy, and in particular to a low-pressure hydroisomerization / cracking process for preparing bio-based aviation fuel. Background Art

[0002] Biojet fuel is a sustainable aviation fuel with great development potential. Composed primarily of a mixture of hydrocarbons with a carbon number distribution of C8 to C16, primarily paraffins, it has high calorific value and a low pour point. It can reduce CO2 emissions by up to 80% over its life cycle, making it a key step in the development of low-carbon aviation fuels worldwide. According to statistics from the International Civil Aviation Organization, between 2008 and 2018, over 165,000 manned commercial flights worldwide used jet fuel containing biojet fuel, with this figure increasing annually. Global consumption of sustainable aviation fuel (biojet fuel) has soared from 8 million liters in 2016 to 100 million liters in 2021, but still represents only 0.02% of total demand, far from enough to meet the 2050 carbon reduction targets, leaving significant room for development.

[0003] Since the American Society for Testing and Materials (ASTM) first certified biojet fuel in 2009, six technology routes have been certified according to the ASTM D7566 standard: Fischer-Tropsch synthesis (FT-SPK), hydrodeoxygenation of oils and fatty acids (HEFA), sugar fermentation and hydrogenation (SIP), light aromatics alkylation (SPK / A), lower alcohols (ATJ-SPK), and catalytic aquathermolysis (CHJ). Considering factors such as feedstock availability, operating costs, and technological maturity, continuous catalytic hydrogenation of oils and fatty acids (HEFA) remains the preferred route for producing oil-based biojet fuel.

[0004] At present, the main production process of biojet fuel is the serial fixed-bed catalytic hydrogenation process, which mainly uses a supported sulfide hydrodeoxygenation catalyst in combination with a precious metal hydrocracking / isomerization catalyst, such as the NExBTL process developed by Finland's Neste Oil Company (US Patent: 7232935) and the Econfining process jointly developed by the US UOP Company and Italy's ENI Company (US Patent: 20060264684). The domestic production process is similar to that of foreign countries. This process has many technical problems: (1) The raw material adaptability of the fixed-bed hydrogenation process is relatively low, and the waste oil raw material needs to undergo strict pretreatment, which is a complicated process; (2) Since the oil hydrodeoxygenation process produces about 12wt.% of water, it will corrode the carrier such as alumina under high temperature and high pressure environment, destroying the structure of the catalyst and causing catalyst pulverization in severe cases; (3) Under high temperature environment, water will also destroy the structure of the sulfide active component. Although the addition of sulfiding agent can restore some of the active structure, it cannot fundamentally prevent the deactivation of the catalyst.

[0005] To reduce the impact of water in high-temperature, high-pressure environments, patent CN201510263141.7 discloses a method for producing aviation biofuel from waste animal and vegetable oils. This method consists of a pretreatment unit, a hydrotreating unit, a degassing and dehydration unit, a hydroconversion unit, and a distillation unit. The process is complex, requiring the addition of a protective agent to the hydrotreating unit and a specialized catalyst grading process to prevent the impact of water generated during oil hydrogenation on catalyst activity. Despite this, the impact of water cannot be fundamentally eliminated.

[0006] Patent 202010821754.9 discloses a method for hydrogenating waste animal and vegetable oils to produce bio-jet fuel and renewable alkanes. This method mixes waste oils with renewable alkanes and then hydrogenates them, hoping to reduce the amount of water generated by reducing the oxygen content in the raw materials. However, the process used in this method is still the traditional fixed-bed hydrogenation process, and the hydrogenation catalyst is also based on activated alumina as a carrier, so it is difficult to use for a long time in a high-temperature and high-pressure hydrothermal environment. In addition, the process uses multiple hydrogen compressors, which is bound to increase the investment cost of the device and the energy consumption during actual production.

[0007] In the conventional process described above, the raw materials are typically heated indirectly using specialized equipment such as furnaces and heat exchangers. Indirect heating utilizes furnace tubes or heat exchangers with excellent thermal conductivity to transfer heat, eliminating direct contact between the heat source and the material being heated. To ensure efficient heating, a temperature gradient must be maintained between the heat source and the material being heated to enhance heat transfer. Consequently, the heat source temperature often exceeds the thermal decomposition temperature of the colloid. Due to its high viscosity, poor thermal conductivity, and strong thermal sensitivity, the colloid easily adheres to the heat transfer surfaces of the heating equipment, along with other oil components. This hinders the timely transfer of heat from the heat source via convection, leading to overheating of the heating surface. When overheating exceeds the thermal decomposition temperature of the colloid or other oil, it triggers thermal decomposition, forming coke. Furthermore, the unsaturated molecules in the material are polymerizable, and excessively high temperatures can trigger and accelerate thermal polymerization reactions. Furthermore, intermediate products from the thermal decomposition of the oil molecules can undergo polycondensation. Both thermal polymerization and thermal polycondensation directly increase the viscosity of the heated material, accelerating the coking process. The polymeric unsaturated structure and heat-sensitive colloidal components of the oil molecules are intrinsic factors in the formation of coking, while the excessively high heat source temperature, exceeding the pyrolysis temperature of the oil molecules, is the direct cause of coking in the raw materials. Coking is primarily destructive to the raw materials. Coking occurs within the equipment, increasing heat energy consumption and shortening equipment operating cycles. In severe cases, it can cause overheating and damage, making normal production difficult. Therefore, if the raw material properties cannot be changed, changing the heating method is a breakthrough approach to resolving the problem of heated coking.

[0008] At the same time, the current process still has some problems: (1) The degree of deterioration of low-quality oil is high, and the processing is difficult, and the industry is not willing to process it; (2) Due to coking and carbon deposition, the heating furnace tubes or related heat exchanger components are blocked, which leads to problems such as deterioration of process operation and shortening of equipment service life; (3) The low-quality biomass oil is highly rancid and has a high acid value. In the conventional treatment process, alkaline substances need to be added to neutralize it to prevent acid corrosion of metal equipment, but the carboxylate produced will bring cost investment and environmental burden to subsequent treatment. (4) For low-quality biomass oils rich in elements such as silicon, calcium, and sodium, a large amount of impurities can cause poisoning of hydrogenation catalysts, and can also cause oil coking, blockage of reaction equipment, and threaten the safe operation of the equipment. Summary of the Invention

[0009] In order to solve the above problems, a low-pressure hydroisomerization / cracking process for preparing bio-based aviation fuel is provided, which is suitable for high-silicon, high-sodium and high-calcium content biomass inferior oil, and first performs grading pretreatment, and then performs hydro-upgrading and hydroisomerization / cracking to produce renewable oil. The technology is simple in operation, can efficiently remove silicon elements and metal impurity elements in the raw material, and then produce high-quality renewable oil, and has good environmental protection significance and economic benefits.

[0010] In a first aspect, the application provides a low-pressure hydroisomerization / cracking process for preparing bio-based aviation fuel, which comprises the following steps:

[0011] (1) The circulating oil is heated to 380-420℃, mixed with the biomass inferior oil, and after mixing with 500-5000ppm of oil-soluble catalyst, it is introduced into a solid catalyst-unloaded suspended bed reactor A for reaction.

[0012] Specifically, the biomass inferior oil raw material can be selected from any one or several of swill-cooked oil, hogwash oil and animal fat. In the treatment process, the raw material and the oil-soluble catalyst are first placed in separate storage tanks. They can be added into the system by pumping. The biomass inferior oil raw material is first preheated to improve its fluidity, filtered to remove mechanical impurities, and the pressure is increased by a pressure pump. Then, it is mixed and uniformly heated with the circulating oil to increase the temperature of the cold feed by the heat carried by the circulating oil. The circulating oil is first heated to 380-420℃ by a heating furnace before being mixed with the raw material feed, and then mixed with no more than 50% of the biomass inferior oil raw material. After mixing the raw material, a certain amount of hydrogen is mixed to form a hydrogenated feed. Before entering the suspended bed reactor A, the hydrogenated feed can be mixed with 500-5000ppm of oil-soluble catalyst by a catalyst charging pump to form a hydrogenated mixed feed. The hydrogenated mixed feed enters the reactor A for hydroprocessing. Under this condition, the reactor A performs conversion, removal pretreatment and double bond saturation, and cracking treatment of excessive alkanes on various functional groups, gum, silicon and metal components in the feed characterized by homogeneous catalysis.

[0013] (2) The return oil is directly mixed with the effluent of the suspended bed reactor A without heat exchange, and is introduced into a solid catalyst-unloaded suspended bed reactor B at a temperature of 320-360℃ for reaction.

[0014] Specifically, the effluent of the suspended bed reactor A is mixed with the bottom oil component from the light component distillation after the back-end process through a pressurized pump before entering the reactor B, and the mixing ratio is not less than 50% of the effluent of the suspended bed reactor A. The mixing temperature is controlled at 320-360°C, and after mixing, the mixture is used as the feed of the suspended bed reactor B and enters the reactor B. Due to the high performance of the oil-soluble catalyst, the reactor B does not need to add the oil-soluble catalyst again, and further hydroprocessing of the raw material can be achieved to further remove elements such as silicon and metal.

[0015] (3) The top effluent of the suspended bed reactor B enters a fixed bed reactor C filled with solid catalysts for hydrofining; the bottom oil of the suspended bed reactor B is separated to obtain heavy oil A and oil residue, and the oil residue is discharged for treatment, and the heavy oil A is returned to the feed end to be mixed with the biomass inferior oil or treated as oil residue.

[0016] Specifically, the top effluent of the suspended bed reactor B directly enters a fixed bed reactor C filled with solid catalysts, and the feed is further subjected to impurity removal and hydrogenation for saturation of unsaturated bonds in the reactor C.

[0017] (4) The effluent of the fixed bed reactor C is divided into two parts, one part is separated to obtain gas phase A and liquid phase A; the other part is separated to obtain heavy oil B and oil residue, and the oil residue is discharged for treatment, and the heavy oil B is returned to the feed end to be mixed with the biomass inferior oil or treated as oil residue;

[0018] (5) Part of the liquid phase A is used as a circulating oil, and the other part is subjected to vacuum separation to obtain gas phase B and liquid phase B, and the liquid phase B is subjected to vacuum distillation tower treatment to obtain side oil and bottom oil, and the bottom oil is separated to obtain heavy oil C and oil residue, and the heavy oil C is used as a return oil; the side oil enters an atmospheric distillation tower for fractionation to obtain light distillate, bio aviation kerosene, low-condensation diesel oil, and high-condensation diesel oil;

[0019] (6) Part of the bottom oil of the atmospheric distillation tower is mixed with hydrogen and enters a hydrogen isomerization reactor D filled with reduced solid catalysts at a certain temperature for reaction, the effluent of the hydrogen isomerization reactor D is mixed with the gas phase A to obtain a hydrocracking material, the hydrocracking material is cooled and enters a high-pressure separator of refined isomerization material to obtain gas phase C and liquid phase C, the liquid phase C enters a low-pressure separator of refined isomerization material and a stripping stabilizer tower to obtain gas phase D and liquid phase D, and the liquid phase D enters the atmospheric distillation tower for separation to obtain light distillate, bio aviation kerosene, low-condensation diesel oil, and high-condensation diesel oil. Another part of the bottom oil of the atmospheric distillation tower can be used as high-condensation diesel oil, and another part can continue to enter the vacuum distillation tower for fractionation treatment or continue to be subjected to hydrogen isomerization treatment.

[0020] Specifically, the effluent of the hydroisomerization reactor D is mixed with the gas phase A to obtain a hydrocracking material, the hydrocracking material is cooled and enters a high-pressure separator of refined isomerization material to obtain a gas phase C and a liquid phase C, the gas phase C mainly contains excess hydrogen, and the hydrogen can be compressed by a recycle hydrogen compressor and returned to the feed end as hydrogen mixing circulating material. The liquid phase C can enter a low-pressure separator of refined isomerization material after decompression, and the gas components dissolved in the liquid phase are separated, and then enter a stripping stabilizer column, and water vapor is used for stripping treatment to further remove the non-ideal components in the liquid phase material, i.e. another part of the gaseous compounds converted from the above-mentioned sulfur, nitrogen, oxygen, phosphorus and other elements in the raw material by hydrogenation, and short-chain hydrocarbons affecting the stability of the product oil, etc. The material after stripping is heated and enters an atmospheric distillation column, and the atmospheric distillation column separates to obtain a side oil and a column bottom oil, and the side oil is cut to obtain a light distillate, a bio-jet fuel and a low-condensation diesel.

[0021] The application adopts a three-stage hydrogenation process, the low-temperature and low-pressure homogeneous hydrogenation method of the oil-soluble catalyst combined with the suspension bed reactor A and the suspension bed reactor B is adopted in the first-stage step (1) and the second-stage step (2) to perform low-cost hydrogenation upgrading pretreatment on the high-silicon and high-metal biomass poor oil, the middle stage is deep fixed-bed hydrofining, and the fixed-bed hydroisomerization reactor is additionally arranged at the rear stage to improve the yield of light oil products, and heavy components are cracked.

[0022] In the above method, the oil-soluble catalyst is used for catalytic hydrogenation pretreatment of the raw material, the oil-soluble catalyst can be uniformly dispersed in the raw material oil, on the one hand, most of the oil-soluble silicon, calcium, sodium and other organic salts are converted into inorganic metals through the catalytic hydrogenation process and are transferred from the raw material to the catalyst; on the other hand, a small amount of inorganic salts are separated from the raw material through the adsorption of the catalyst itself, and then the silicon and other metal elements in the biomass poor oil are efficiently removed. The oil-soluble catalyst can improve the catalytic efficiency while removing the silicon, calcium, sodium and other impurities in the oil-soluble catalyst to obtain high-quality oil products.

[0023] Optionally, the preparation method of the oil-soluble catalyst comprises the following steps: two or more non-noble transition metals are first synthesized into a double-metal or triple-metal composite oxide precursor through a solvothermal process in a water-ethanol-toluene mixed solution, and then an oil-soluble catalyst is prepared through modification of an organic ion ligand in methanol.

[0024] Optionally, the non-noble transition metal is any two or more combinations of cobalt, nickel, molybdenum and tungsten, and the synthesis steps of the oil-soluble catalyst comprise:

[0025] (1) Take 0.1 mol of cobalt nitrate or nickel nitrate and dissolve it in 50 mL of ethanol to obtain solution A, take 0.1 mol of ammonium molybdate and / or ammonium metatungstate and dissolve it in 50 mL of deionized water to obtain solution B;

[0026] (2) Take 50 mL of toluene and add it to solution A to obtain solution C, then add solution B dropwise to solution C to obtain mixture D;

[0027] (3) Put mixture D into a 200 mL hydrothermal crystallization kettle with a polytetrafluoroethylene lining, seal it and put it in a 160°C oven for 2 hours;

[0028] (4) After taking out the crystallization kettle and naturally cooling it, the obtained product is filtered, washed and dried to obtain a double-metal or triple-metal composite oxide precursor;

[0029] (5) Take 0.4 mol of an organic ionic ligand and dissolve it in methanol, then add 0.1 mol of the double-metal or triple-metal composite oxide precursor, reflux at 60°C for 6 hours, then centrifugal separation to obtain an oil-soluble catalyst.

[0030] Optionally, the double-metal or triple-metal composite oxide precursor is one or more of ammonium cobalt molybdate hydroxide [(NH4)HCo2(OH)2Mo2O8], ammonium nickel molybdate hydroxide [(NH4)HNi2(OH)2Mo2O8], ammonium cobalt tungstate hydroxide [(NH4)HCo2(OH)2W2O8], ammonium nickel tungstate hydroxide [(NH4)HNi2(OH)2W2O8], ammonium cobalt molybdate tungstate hydroxide [(NH4)HCo2(OH)2MoWO8], and ammonium nickel molybdate tungstate hydroxide [(NH4)HNi2(OH)2MoWO8].

[0031] Optionally, the organic ionic ligand is one or more of dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, 1-butyl-3-methylimidazolium chloride, and 1-alkyl-2,3-dimethylimidazolium bromide.

[0032] Optionally, the silicon content in the biomass inferior oil is 20-100 ppm, the sodium content is 20-60 ppm, the calcium content is 40-200 ppm, and the sulfur content is 50-200 ppm.

[0033] Optionally, the silicon content in the biomass inferior oil is 40-100 ppm, the sodium content is 40-60 ppm, and the calcium content is 100-200 ppm.

[0034] Optionally, the mass ratio of the biomass inferior oil to the circulating oil in step (1) is 1:(1-5).

[0035] Optionally, the pressure of the ultra-low pressure condition in the suspended bed reactor A, the suspended bed reactor B, the fixed bed reactor C and the hydrogen isomerization reactor D is 3-8 MPa; preferably, the pressure of the ultra-low pressure condition is 4-6 MPa.

[0036] The above reactors are all low pressure, and the reaction condition of the low pressure is relatively mild, which is helpful to prolong the service life of the hydro-upgrading and oil-soluble catalysts; at the same time, the low pressure condition has low requirement on the reaction device, which can reduce the equipment investment cost and operation cost and improve the economic benefit.

[0037] Optionally, the temperature of the fixed bed reactor C is 260-320℃, and the temperature of the hydrogen isomerization reactor D is 240-340℃.

[0038] Preferably, the temperature of the fixed bed reactor C is 260-300℃, and the temperature of the hydrogen isomerization reactor D is 260-300℃.

[0039] Optionally, the hydrogen to oil ratio in the suspended bed reactor A is 400-1000, and the volume space velocity is 0.1-2.0 h -1 The hydrogen to oil ratio in the suspended bed reactor B is 200-500, and the volume space velocity is 0.1-2.0 h -1 The hydrogen to oil ratio in the fixed bed reactor C is 400-600, and the volume space velocity is 0.1-1.8 h -1 The hydrogen to oil ratio in the hydrogen isomerization reactor D is 400-800, and the volume space velocity is 0.1-1.5 h -1 .

[0040] Optionally, the solid catalyst used in the fixed bed reactor C is a catalyst in which nickel and molybdenum are supported on alumina, and the catalyst needs to be pre-sulfurized before use; the catalyst used in the hydrogen isomerization reactor D is a reduced non-noble metal bifunctional catalyst.

[0041] Optionally, the reduced non-noble metal bifunctional catalyst includes 20-40% Y zeolite, 10-20% ZSM-22 zeolite, 30-45% nickel metal, and γ-Al2O3, and the total mass fraction of the raw materials of the Y zeolite, the ZSM-22 zeolite, the nickel metal and the γ-Al2O3 is 100%.

[0042] Optionally, the preparation method of the reduced non-noble metal bifunctional catalyst includes the following steps:

[0043] S1: preparing Y zeolite seeds;

[0044] S2: embedding nickel metal nanoparticles into the Y zeolite seeds obtained in step S1 in situ to obtain a metal-Y zeolite composite;

[0045] S3: treating the metal-Y molecular sieve composite prepared in step S2 with inorganic acid, and then sequentially filtering, washing with water, drying, and calcining to obtain a metal-Y molecular sieve catalyst;

[0046] S4: adding ZSM-22 molecular sieve, aluminum hydroxide dry gel powder, dilute nitric acid solution, and sesbania powder to the metal-Y molecular sieve catalyst obtained in step S3, and then kneading, molding, drying, calcining, and reducing to obtain a reduced non-noble metal bifunctional catalyst.

[0047] Optionally, the method for preparing the metal-Y molecular sieve composite in step S2 comprises the following steps:

[0048] The Y molecular sieve seeds are dispersed in deionized water, a template agent is added, and after dissolution, a silicon source, an aluminum source, a nickel salt, and sodium hydroxide are added, and the reaction is carried out at 80-120 DEG C. The metal-Y molecular sieve composite with nickel metal nanoparticles in situ embedded in the Y molecular sieve seeds is obtained after sequentially filtering, washing, and drying.

[0049] Optionally, the template agent is one or a combination of pyrrolidine, ethylenediamine, n-butylamine, di-n-propylamine, tetrapropylammonium bromide, tetrapropylammonium hydroxide, and cetyltrimethylammonium bromide (CTAB).

[0050] In the preparation method of the reduced non-noble metal bifunctional catalyst, the Y molecular sieve seeds are used to in situ embed the non-noble active nickel metal nanoparticles in the Y molecular sieve through a co-crystallization process, the growth of the Y molecular sieve seeds is induced by nickel metal atoms, and the surface of the molecular sieve particles is modified to eliminate part of the acid centers, thereby forming a metal-Y molecular sieve catalyst with mild cracking performance. Then, the metal-Y molecular sieve catalyst is mixed with ZSM-22 molecular sieve with isomerization performance to form a bifunctional catalyst, which is used for the production of oil and fat-based bio-jet fuel and low freezing point biodiesel, and can improve the production efficiency and reduce the acid value of the oil product.

[0051] Compared with the prior art, the present application at least has one of the following beneficial effects:

[0052] (1) The low-pressure hydroisomerization / cracking process of the present application, after the oil material is subjected to hydrogenation, the oil material has undergone a quality modification process, and the unsaturation degree has been greatly improved. The oxygen element is converted into water by hydrogenation, so the instability of the oil material has been greatly improved. The thermal sensitivity of this modified oil material has been greatly reduced, and it can withstand higher heating temperatures without unacceptable coking. Therefore, the modified oil is further heated to carry enough heat, and then directly mixed with the cold oil material, that is, by homogenizing the two cold and hot materials, the feed oil can be uniformly heated. This heating method by homogenization to achieve uniform temperature is different from the conventional indirect conduction heating mechanism. Since there is no barrier of intermediate medium in the heat transfer process, the heat source and the heated body do not need to maintain a high temperature difference gradient to achieve efficient heat transfer, thus fundamentally eliminating the cause of coking of the raw material.

[0053] (2) The low-pressure hydroisomerization / cracking process of the present application uses a homogeneous hydrogenation method combining liquid catalysts with a suspended bed reactor to pretreat the raw material. The acid in the feed is removed by the hydrodecarboxylation chemical reaction process to reduce the acid value. The cumbersome process of neutralizing with alkali and then separating and removing carboxylate salt in the conventional process is omitted.

[0054] (3) The low-pressure hydroisomerization / cracking process of the present application uses the high-temperature intermediate material with improved thermal stability after pretreatment to heat the raw material by directly mixing and uniform temperature with the cold raw material feed, avoiding the problem of coking and plugging the heating equipment due to overheating of the raw material in the conventional process. In addition, the method of directly mixing and uniform temperature with the cold raw material feed to heat the raw material can promote catalyst dispersion and avoid the problem of catalyst deactivation and plugging of the heating equipment due to high heating temperature.

[0055] (4) The low-pressure hydroisomerization / cracking process of the present application can remove silicon, sodium, and calcium elements in the biomass inferior oil, thereby reducing their influence on subsequent reactions and improving the quality of the final product. BRIEF DESCRIPTION OF DRAWINGS

[0056] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0057] Figure 1 A process flow diagram of an exemplary embodiment of the low-pressure hydroisomerization / cracking process for preparing bio-based aviation fuel of the present application is shown.

[0058] The reference signs are explained as follows:

[0059] 1 - Biomass inferior oil buffer tank, 2 - Biomass inferior oil pressurizing pump, 3 - Recycle oil heating furnace, 4 - Oil-soluble catalyst storage tank, 5 - Oil-soluble catalyst pressurizing pump, 6 - Suspended bed reactor A, 7 - Refeed oil intermediate tank, 8 - Refeed oil pressurizing pump, 9 - Suspended bed reactor B, 10 - Fixed bed reactor C, 11 - Post-refining hot high-pressure separator, 12 - Recycle oil pump, 13 - Post-refining hot low-pressure separator, 14 - Vacuum distillation column, 15 - Atmospheric distillation column, 16 - Oil residue filtration machine, 17 - Isomerization reactor feed pressurizing pump, 18 - Isomerization reactor feed heating furnace, 19 - Hydroisomerization reactor D, 20 - Refined isomerization material cooler, 21 - Refined isomerization material high-pressure separator, 22 - Refined isomerization material low-pressure separator, 23 - Stripping stabilizer column, 24 - Recycle hydrogen compressor, 25 - Fresh hydrogen compressor, 26 - Oil residue separation tank. DETAILED DESCRIPTION

[0060] In order to more clearly illustrate the overall concept of the present application, a detailed description of the same will be made below with reference to the accompanying drawings.

[0061] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced without the specific details given herein. In other instances, well-known methods have not been described in detail in order to avoid unnecessarily complicating the present application. Accordingly, the scope of the present application is not intended to be limited by the specific representations of preferred embodiments described below.

[0062] Example 1

[0063] Reference Figure 1 The present embodiment relates to a hydroisomerization / cracking system for preparing bio-based aviation fuel, comprising: a biomass inferior oil feed group including a biomass inferior oil buffer tank 1, a biomass inferior oil pressurizing pump 2;

[0064] an oil-soluble catalyst feed group including an oil-soluble catalyst storage tank 4, an oil-soluble catalyst pressurizing pump 5, a suspended bed reactor A 6;

[0065] a hydroprocessing group including a recycle oil heating furnace 3, a refeed oil intermediate tank 7, a refeed oil pressurizing pump 8, a suspended bed reactor B 9, a fixed bed reactor C 10, a post-refining hot high-pressure separator 11, a recycle oil pump 12, a post-refining hot low-pressure separator 13, a vacuum distillation column 14, an atmospheric distillation column 15, an oil residue filtration machine 16, an isomerization reactor feed pressurizing pump 17, an isomerization reactor feed heating furnace 18, a hydroisomerization reactor D 19, a refined isomerization material cooler 20, a refined isomerization material high-pressure separator 21, a refined isomerization material low-pressure separator 22, a stripping stabilizer column 23, a recycle hydrogen compressor 24, a fresh hydrogen compressor 25, an oil residue separation tank 26.

[0066] The steps of the operation of the system are as follows:

[0067] (1) The circulating oil is heated by the circulating oil heating furnace 3, and the biomass inferior oil is injected from the biomass inferior oil buffer tank 1 through the biomass inferior oil pressure pump 2 to mix with the heated circulating oil. Then, the oil-soluble catalyst in the oil-soluble catalyst storage tank 4 is injected through the oil-soluble catalyst injection pump 5, and the mixed materials enter the suspended bed reactor A6 without solid catalyst loading to realize one-stage hydrogenation.

[0068] (2) The return oil is injected from the return oil intermediate tank 7 through the return oil pressure pump 8, mixed with the effluent of the suspension bed reactor A6, and then enters the suspension bed reactor B9 without solid catalyst loading to achieve re-hydrogenation.

[0069] (3) The top effluent of the suspended bed reactor B9 enters the fixed bed reactor C10 filled with a solid catalyst for hydrotreating. The bottom oil of the suspended bed reactor B9 is separated into heavy oil A and oil residue by the oil residue separator 26. The oil residue is discharged for treatment, and the heavy oil A is returned to the feed end to be mixed with biomass inferior oil or treated as oil residue.

[0070] (4) A portion of the effluent from the fixed bed reactor C10 enters the post-refining hot high-pressure separator 11 for separation of the gas phase and the liquid phase to obtain gas phase A and liquid phase A; the other portion passes through the oil residue separator 26 for separation to obtain heavy oil B and oil residue. The oil residue is discharged for treatment, and the heavy oil B is returned to the feed end to be mixed with biomass inferior oil or treated as oil residue.

[0071] (5) A portion of the liquid phase A is pressurized as circulating oil by the circulating oil pump 12, and then heated by the heating furnace 3, and returned to the feed end of the system to be mixed with the raw biomass inferior oil; the other portion of the liquid phase A is first separated from the dissolved gas component (gas phase B) by the refined hot low-pressure separator 13 to obtain a refined material (liquid phase B), and the refined material is heated by the heating furnace and enters the vacuum distillation tower 14. Through the fractionation operation under reduced pressure, the refined material is divided into light and heavy components. The heavy component at the bottom of the tower is separated by the oil residue filtering machine 16 to obtain heavy oil C and oil residue. The heavy oil C is used as the return oil, and the light component of the side line enters the atmospheric distillation tower 15 to obtain light fractions, bio-jet fuel, and low-condensation diesel; a portion of the heavy component of the tower bottom oil is used as high-condensation diesel, and the other portion of the tower bottom oil can continue to enter the vacuum distillation tower 14 for fractionation treatment or hydrogenation isomerization treatment.

[0072] (6) hydrogen is injected by fresh hydrogen compressor 25, part of the bottom oil of atmospheric distillation column 15 is mixed with the injected hydrogen by isomerization reactor feed pressurizing pump 17, heated by heating furnace 18, and then enters hydrogenation isomerization reactor D 19 filled with solid catalyst in reduced state to react, the effluent of hydrogenation isomerization reactor D 19 is mixed with gas phase A to obtain a hydrogenation cracking material, which enters refined isomerization material cooler 20 to cool, and then enters refined isomerization material high-pressure separator 21 to separate to obtain gas phase C and liquid phase C, the composition of gas phase C is mainly excess residual hydrogen, part of this hydrogen is returned to the feed end as a hydrogen mixing circulating material after being pressurized by circulating hydrogen compressor 24, and part of it is mixed with fresh hydrogen. Liquid phase C enters refined isomerization material low-pressure separator 22 to further separate the gas components dissolved in the liquid phase, and then enters stripping stabilizer column 23, which is treated by steam stripping to further remove the non-ideal components dissolved in the liquid phase material, i.e. another part of the gaseous compounds converted from the above-mentioned sulfur, nitrogen, oxygen, phosphorus and other elements in the raw material by hydrogenation and short-chain hydrocarbons affecting the stability of the product oil, etc. After stripping, acid gas D and liquid phase D are obtained, acid gas D is discharged as waste gas, and liquid phase D is heated and warmed to enter atmospheric distillation column 15 to separate to obtain light distillate, bio-jet fuel, low-condensation diesel and high-condensation diesel. The high-condensation diesel can continue to enter the vacuum distillation column 14 for fractionation treatment or hydrogenation isomerization treatment.

[0073] Through the system, high-quality regenerated oil products of light distillate, bio-jet fuel, low-condensation diesel and high-condensation diesel can be produced by processing biomass inferior oil, which has good environmental protection significance and economic benefits.

[0074] Example 2

[0075] This embodiment relates to a low-pressure hydrogenation isomerization / cracking process for preparing bio-based aviation fuel, which adopts the system and operation mode of example 1, and the low-pressure hydrogenation isomerization / cracking process comprises the following steps:

[0076] (1) The circulating oil is heated to 380-420℃ by a heating furnace, mixed with biomass inferior oil with silicon content of 20-100ppm, sodium content of 20-60ppm, calcium content of 40-200ppm, and sulfur content of 50-200ppm, and mixed with 500-5000ppm of oil-soluble catalyst, and then enters a suspended bed reactor A without solid catalyst loading for reaction;

[0077] (2) The return oil is mixed with the effluent of suspended bed reactor A without heat exchange, and enters suspended bed reactor B without solid catalyst loading at a temperature of 320-360℃ for reaction;

[0078] (3) The top effluent of the suspended bed reactor B enters the fixed bed reactor C filled with a solid catalyst for hydrotreating; the bottom oil of the suspended bed reactor B is separated to obtain heavy oil A and oil residue;

[0079] (4) The effluent from the fixed bed reactor C is divided into two parts. One part is separated to obtain gas phase A and liquid phase A; the other part is separated to obtain heavy oil B and oil residue;

[0080] (5) A portion of the liquid phase A is used as circulating oil, and the other portion is decompressed and separated to obtain gas phase B and liquid phase B. The liquid phase B is passed through a vacuum distillation tower to obtain side oil and bottom oil. The bottom oil is separated to obtain heavy oil C and oil residue. The heavy oil C is used as return oil; the side oil enters an atmospheric distillation tower for fractionation to obtain light fractions, bio-jet fuel, low-viscosity diesel and high-viscosity diesel.

[0081] (6) Part of the bottom oil of the atmospheric distillation tower is mixed with hydrogen and enters the hydroisomerization reactor D filled with a reduced solid catalyst for reaction at a certain temperature. The effluent of the hydroisomerization reactor D is mixed with the gas phase A to obtain a hydrocracking material. The hydrocracking material is cooled and enters the refined isomerization high-pressure separator to obtain a gas phase C and a liquid phase C. The liquid phase C enters the refined isomerization low-pressure separator and the stripping stabilization tower to obtain a gas phase D and a liquid phase D. The liquid phase D enters the atmospheric distillation tower for separation to obtain light fractions, bio-jet fuel, low-condensation diesel and high-condensation diesel. The high-condensation diesel can continue to enter the vacuum distillation tower or the hydroisomerization reactor D for hydrogenation and quality improvement.

[0082] Through this low-pressure hydroisomerization / cracking process, it is possible to process low-quality biomass oils and fats to produce high-quality recycled oil products such as light fractions, bio-jet fuel, low-viscosity diesel, and high-viscosity diesel, which has good environmental significance and economic benefits.

[0083] Example 3

[0084] This embodiment relates to a low-pressure hydroisomerization / cracking process for preparing bio-based aviation fuel. The low-pressure hydroisomerization / cracking process adopts the system and system operation mode of Example 1. The low-pressure hydroisomerization / cracking process includes the following steps:

[0085] (1) Circulating oil is heated to 380-420° C. in a heating furnace, mixed with low-quality biomass oil having a silicon content of 80 ppm, a sodium content of 60 ppm, a calcium content of 160 ppm, and a sulfur content of 100 ppm, and then mixed with 500-5000 ppm of an oil-soluble catalyst and then fed into a suspended bed reactor A without solid catalyst loading for reaction;

[0086] (2) The return oil is directly mixed with the effluent of the suspension bed reactor A without heat exchange, and then fed into the suspension bed reactor B without solid catalyst loading at a temperature of 320-360°C for reaction;

[0087] (3) The top effluent of the suspended bed reactor B enters the fixed bed reactor C filled with a solid catalyst for hydrotreating; the bottom oil of the suspended bed reactor B is separated to obtain heavy oil A and oil residue;

[0088] (4) The effluent from the fixed bed reactor C is divided into two parts. One part is separated to obtain gas phase A and liquid phase A; the other part is separated to obtain heavy oil B and oil residue;

[0089] (5) A portion of the liquid phase A is used as circulating oil, and the other portion is decompressed and separated to obtain a gas phase B and a liquid phase B. The liquid phase B is passed through a vacuum distillation tower to obtain a side oil and a bottom oil. The bottom oil is separated to obtain a heavy oil C and oil residue. The heavy oil C is used as a return oil. The side oil enters an atmospheric distillation tower for fractionation to obtain a light fraction, bio-jet fuel, low-freezing point diesel, and high-freezing point diesel.

[0090] (6) Part of the bottom oil of the atmospheric distillation tower is mixed with hydrogen and enters the hydroisomerization reactor D filled with a reduced solid catalyst for reaction at a certain temperature. The effluent of the hydroisomerization reactor D is mixed with the gas phase A to obtain a hydrocracking material. The hydrocracking material is cooled and enters the refined isomerization high-pressure separator to obtain a gas phase C and a liquid phase C. The liquid phase C enters the refined isomerization low-pressure separator and the stripping stabilization tower to obtain a gas phase D and a liquid phase D. The liquid phase D enters the atmospheric distillation tower for separation to obtain light fractions, bio-jet fuel, low-condensation diesel and high-condensation diesel. The high-condensation diesel can continue to enter the vacuum distillation tower or the hydroisomerization reactor D for hydrogenation and quality improvement.

[0091] According to the above steps, the same batch of biomass low-quality oil was processed, and different parameter conditions were set according to the numbers in Table 1 and Table 2. Among them, the “-” in Table 1 and Table 2 represents the same as method 3#:

[0092] Among them, method 1#

[0093] The preparation method of the oil-soluble catalyst in step (1) comprises the following steps:

[0094] a. Dissolve 0.1 mol of cobalt nitrate in 50 mL of ethanol to obtain solution A, and dissolve 0.1 mol of ammonium molybdate in 50 mL of deionized water to obtain solution B;

[0095] b. 50 mL of toluene was added to solution A to obtain solution C, and then solution B was added dropwise to solution C to obtain a mixture D;

[0096] c. Add mixture D to a 200 mL hydrothermal crystallization reactor lined with polytetrafluoroethylene, seal it, and place it in an oven at 160°C for 2 hours.

[0097] d. After the crystallization kettle is taken out and naturally cooled, the obtained product is filtered, washed, and dried to obtain a bimetallic composite oxide precursor (NH4) HCo2(OH)2Mo2O8.

[0098] e. 0.4 mol of hexadecyl trimethyl ammonium chloride is dissolved in methanol, and then 0.1 mol of (NH4) HCo2(OH)2Mo2O8 is added. Refluxing is performed at 60°C for 6 hours, and then centrifugal separation is performed to obtain a Co-Mo oil-soluble catalyst.

[0099] The solid catalyst in step (3) is a nickel-molybdenum catalyst supported on alumina, and the catalyst needs to be pre-sulfurized before use.

[0100] The reduced solid catalyst in step (6) is a nickel catalyst containing a molecular sieve, and the catalyst needs to be pre-reduced before use.

[0101] Method 2

[0102] The preparation method of the oil-soluble catalyst in step (1) includes the following steps:

[0103] a. 0.1 mol of nickel nitrate is dissolved in 50 mL of ethanol to obtain solution A, and 0.1 mol of ammonium molybdate is dissolved in 50 mL of deionized water to obtain solution B;

[0104] b. 50 mL of toluene is added to solution A to obtain solution C, and then solution B is added dropwise to solution C to obtain mixture D;

[0105] c. Mixture D is added to a 200 mL hydrothermal crystallization kettle with a polytetrafluoroethylene lining, and after being sealed, it is placed in a 160°C oven for 2 hours;

[0106] d. After the crystallization kettle is taken out and naturally cooled, the obtained product is filtered, washed, and dried to obtain a bimetallic composite oxide precursor (NH4) HNi2(OH)2Mo2O8.

[0107] e. 0.4 mol of hexadecyl trimethyl ammonium chloride is dissolved in methanol, and then 0.1 mol of (NH4) HNi2(OH)2Mo2O8 is added. Refluxing is performed at 60°C for 6 hours, and then centrifugal separation is performed to obtain a Ni-Mo oil-soluble catalyst.

[0108] The solid catalyst in step (3) is a nickel-molybdenum catalyst supported on alumina, and the catalyst needs to be pre-sulfurized before use.

[0109] The reduced solid catalyst in step (6) is a nickel catalyst containing a molecular sieve, and the catalyst needs to be pre-reduced before use.

[0110] Method 3

[0111] The preparation method of the oil-soluble catalyst in step (1) comprises the following steps:

[0112] a. Dissolve 0.1 mol of cobalt nitrate in 50 mL of ethanol to obtain solution A, and dissolve 0.1 mol of ammonium metatungstate in 50 mL of deionized water to obtain solution B;

[0113] b. 50 mL of toluene was added to solution A to obtain solution C, and then solution B was added dropwise to solution C to obtain a mixture D;

[0114] c. Add mixture D to a 200 mL hydrothermal crystallization reactor lined with polytetrafluoroethylene, seal it, and place it in an oven at 160°C for 2 hours.

[0115] d. After removing the crystallization reactor and cooling naturally, the resulting product was filtered, washed, and dried to obtain a bimetallic composite oxide precursor (NH4) HCo2 (OH) 2W2O8;

[0116] e. Take 0.4 mol of hexadecyltrimethylammonium chloride and dissolve it in methanol. Then add 0.1 mol of (NH4)HCo2(OH)2W2O8 and reflux at 60°C for 6 hours. Then centrifuge to obtain a Co-W oil-soluble catalyst.

[0117] The solid catalyst in step (3) is a catalyst in which nickel and molybdenum are supported on alumina, and the catalyst needs to be pre-sulfurized before use.

[0118] The reduced solid catalyst in step (6) is a nickel catalyst containing molecular sieves, and the catalyst needs to be pre-reduced before use.

[0119] Method 4#

[0120] Based on method 3#, the main difference is that the reduced non-precious metal bifunctional catalyst in the hydroisomerization reactor D includes 40% Y molecular sieve, 20% ZSM-22 molecular sieve, 30% nickel metal element and 10% γ-Al2O3.

[0121] The preparation method of the reduced non-noble metal bifunctional catalyst comprises the following steps:

[0122] S1: Sodium silicate, sodium metaaluminate and sodium hydroxide are dissolved in deionized water to obtain a viscous liquid with a feed ratio of SiO2:Al2O3:Na2O:H2O=30:1.5:30:800; then hydrothermal treatment is performed at 60°C for 2 days to obtain Y molecular sieve seed crystals.

[0123] S2: Disperse Y zeolite seeds into deionized water, add 2wt% CTAB, after dissolving, add sodium silicate, sodium aluminate, nickel nitrate and sodium hydroxide, crystallize at 100°C for 36 hours, and then filter, wash with deionized water until neutral and dry to obtain a metal-Y zeolite composite; the feeding ratio of Y zeolite seeds, sodium silicate, sodium aluminate, nickel nitrate, sodium hydroxide and water is 0.5:2.5:0.8:4:3.5:300 by mass of oxides.

[0124] S3: Add the metal-Y zeolite composite into a mixed solution of 0.15mol / L hydrochloric acid and phosphoric acid with a mass ratio of 1:1, and treat at 60°C for 6 hours; wash the acid-treated composite until neutral, and then dry, calcine at 450°C for 4 hours to obtain a metal-Y zeolite catalyst.

[0125] S4: Take 30g of the metal-Y zeolite catalyst, 6g of ZSM-22 zeolite, 4g of aluminum hydroxide dry gel powder, 2g of dilute nitric acid solution and 2g of sesbania powder, then mix, shape, dry, calcine at 500°C for 4 hours, and reduce at 500°C for 4 hours to obtain an isomerization catalyst with a nickel content of 30wt%.

[0126] Method 9#

[0127] On the basis of method 3#, the main difference is that the preparation method of the oil-soluble catalyst in step (1) comprises the following steps:

[0128] a. Take 0.1mol of nickel nitrate and dissolve it in 50mL of ethanol to obtain solution A, and take 0.1mol of ammonium metatungstate and dissolve it in 50mL of deionized water to obtain solution B;

[0129] b. Take 50mL of toluene and add it to solution A to obtain solution C, and then add solution B dropwise to solution C to obtain mixture D;

[0130] c. Put mixture D into a 200mL hydrothermal crystallization kettle with a polytetrafluoroethylene liner, seal it and put it in a 160°C oven for 2 hours;

[0131] d. After taking out the crystallization kettle and naturally cooling it, the obtained product is filtered, washed and dried to obtain a bimetallic composite oxide precursor (NH4)HNi2(OH)2W2O8;

[0132] e. Take 0.4mol of hexadecyltrimethylammonium chloride and dissolve it in methanol, and then add 0.1mol of (NH4)HNi2(OH)2W2O8, and reflux at 60°C for 6 hours, and then centrifugalize to obtain a Ni-W oil-soluble catalyst.

[0133] Method 10#

[0134] On the basis of method 3#, the main difference is that the preparation method of step (1) of the oil-soluble catalyst comprises the following steps:

[0135] a. Take 0.1 mol of cobalt nitrate and dissolve it in 50 mL of ethanol to obtain solution A, and dissolve 0.05 mol of ammonium molybdate and 0.05 mol of ammonium metatungstate together in 50 mL of deionized water to obtain solution B;

[0136] b. Take 50 mL of toluene and add it to solution A to obtain solution C, and then add solution B dropwise to solution C to obtain mixture D;

[0137] c. Add mixture D to a 200 mL hydrothermal crystallization kettle with a polytetrafluoroethylene lining, seal it, and then place it in a 160°C oven for 2 hours;

[0138] d. After taking out the crystallization kettle and naturally cooling it, the obtained product is filtered, washed, and dried to obtain a trimetallic composite oxide precursor (NH4)HCo2(OH)2MoWO8;

[0139] e. Take 0.4 mol of hexadecyltrimethylammonium chloride and dissolve it in methanol, then add 0.1 mol of (NH4)HCo2(OH)2MoWO8, and reflux at 60°C for 6 hours, and then centrifugally separate to obtain a Co-Mo-W oil-soluble catalyst.

[0140] Method 11

[0141] On the basis of method 3#, the main difference is that the preparation method of step (1) of the oil-soluble catalyst comprises the following steps:

[0142] a. Take 0.1 mol of nickel nitrate and dissolve it in 50 mL of ethanol to obtain solution A, and dissolve 0.05 mol of ammonium molybdate and 0.05 mol of ammonium metatungstate together in 50 mL of deionized water to obtain solution B;

[0143] b. Take 50 mL of toluene and add it to solution A to obtain solution C, and then add solution B dropwise to solution C to obtain mixture D;

[0144] c. Add mixture D to a 200 mL hydrothermal crystallization kettle with a polytetrafluoroethylene lining, seal it, and then place it in a 160°C oven for 2 hours;

[0145] d. After taking out the crystallization kettle and naturally cooling it, the obtained product is filtered, washed, and dried to obtain a trimetallic composite oxide precursor (NH4)HNi2(OH)2MoWO8;

[0146] e. 0.4 mol of cetyltrimethylammonium chloride was dissolved in methanol, and then 0.1 mol of (NH4)HNi2(OH)2MoWO8 was added, and refluxed at 60°C for 6 hours, and then centrifuged to obtain a Ni-Mo-W oil-soluble catalyst.

[0147] Table 1

[0148]

[0149]

[0150] Note: "-" in the table represents the same as method 3#

[0151] Table 2

[0152]

[0153]

[0154] Note: "-" in the table represents the same as method 3#

[0155] Test Example 1

[0156] The top effluent of the suspended bed reactor A prepared by the above method of Example 3 was tested, and the content of silicon element, sodium element and calcium element was determined by elemental analysis, and the test results are shown in Table 3.

[0157] Table 3

[0158]

[0159] Test Example 2

[0160] The performance of the bio-jet fuel, low freezing point diesel and high freezing point diesel prepared by the above method of Example 3 was tested, and the results are shown in Table 4.

[0161] Table 4

[0162]

[0163] Comparative Example 1

[0164] The process of Example 2 was changed, and the raw material did not need to be treated by a suspended bed hydrogenation, but directly entered a fixed bed hydrogenation reactor, including the following steps:

[0165] (1) The circulating oil was heated to 380°C by a heating furnace, mixed with biomass inferior oil with a silicon content of 80 ppm, a sodium content of 60 ppm, and a calcium content of 160 ppm, and rapidly passed through the suspended bed reactor A;

[0166] (2) The return oil is directly mixed with the effluent from the slurry bed reactor A without heat exchange, and is rapidly passed through the slurry bed reactor B at a temperature of 320°C;

[0167] (3) The top effluent of the slurry bed reactor B is introduced into the fixed bed reactor C packed with solid catalyst for hydrodeoxygenation;

[0168] (4) The effluent of the fixed bed reactor C is divided into two parts, one part is separated to obtain gas phase A and liquid phase A; the other part is separated to obtain heavy oil B and oil residue;

[0169] (5) Part of the liquid phase A is used as a circulating oil, and the other part is subjected to vacuum separation to obtain gas phase B and liquid phase B, the liquid phase B is subjected to vacuum rectification tower to obtain side oil and bottom oil, the bottom oil is separated to obtain heavy oil C and oil residue, and the heavy oil C is used as a return oil; the side oil is introduced into the atmospheric rectification tower for fractionation to obtain light distillate, bio-jet fuel, low-condensation diesel and high-condensation diesel;

[0170] (6) Part of the bottom oil of the atmospheric rectification tower is mixed with hydrogen and introduced into the hydrogen isomerization reactor D packed with reduced solid catalyst at a certain temperature for reaction, the effluent of the hydrogen isomerization reactor D is mixed with the gas phase A to obtain a hydrocracking material, the hydrocracking material is cooled and introduced into the high-pressure separator of refined isomerization material to obtain gas phase C and liquid phase C, the liquid phase C is introduced into the low-pressure separator of refined isomerization material and the stripping stabilizer tower to obtain gas phase D and liquid phase D, the liquid phase D is introduced into the atmospheric rectification tower for separation to obtain light distillate, bio-jet fuel, low-condensation diesel and high-condensation diesel, and the high-condensation diesel can continue to be introduced into the vacuum rectification tower or the hydrogen isomerization reactor D for hydro-upgrading.

[0171] In the comparative example 1, the raw material is not subjected to slurry bed hydrogen treatment, but is directly introduced into the fixed bed hydrogenation reactor, and the conventional full fixed bed hydrogenation process cannot adapt to the high impurity content of the biomass inferior oil, and the hydrogenation refining catalyst will be deactivated due to the deposition of heteroatoms, coking and water-soluble etching in a short time. In addition, the raw material is not subjected to slurry bed hydrogen treatment at the temperature of the present application for hydrocracking, and without oil-soluble catalyst, the raw material will coking at such a high temperature, which is more unfavorable for the subsequent fixed bed hydrogenation reaction.

[0172] Comparative example 2

[0173] On the basis of the comparative example 1, the main difference is that the biomass inferior oil is pretreated according to the method of comparative example 1 in the reference patent CN202410206993.1 (a waste oil pretreatment method) before being mixed with the circulating oil and introduced into the slurry bed reactor A.

[0174] In the comparative example 2, the use of the traditional pretreatment process will cause a loss of about 10% of the raw material, affecting the overall yield of the product.

[0175] Test Example 3

[0176] The performance of the bio-jet fuel, low freezing point diesel, and high freezing point diesel prepared by the above method of Comparative Examples 1 and 2 was tested, and the results are shown in Table 5.

[0177] Table 5

[0178]

[0179] In summary, the low-pressure hydroisomerization / cracking process of the present application can be used to treat low-quality biomass oil with high silicon, sodium, and calcium contents to produce high-quality regenerated oil products, such as light distillate, bio-jet fuel, low freezing point diesel, and high freezing point diesel, which has good environmental significance and economic benefits. Preferably, after the suspended bed hydroprocessing, the silicon content in the raw material oil is not higher than 3 ppm, the sodium content is not higher than 3 ppm, the calcium content is not higher than 3 ppm, the sulfur content is not higher than 20 ppm, and the oxygen content is not higher than 3 wt%. The synergistic effect of the hydroisomerization / cracking process and the catalyst can effectively reduce the risk of deactivation of the downstream fixed bed reaction catalyst, and prolong the overall operation time of the device. At the same time, the suspended bed hydroprocessing process can replace the traditional pretreatment process, which can avoid the loss of oil raw materials and improve the product yield.

[0180] The above only describes the embodiments of the present application and is not intended to limit the present application. The present application can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the scope of the claims of the present application.

Claims

1. A low-pressure hydroisomerization / cracking process for preparing bio-based aviation fuel, characterized in that: The low-pressure hydroisomerization / cracking process comprises the following steps: (1) The circulating oil is heated to 380-420°C, mixed with low-quality biomass oil, and then mixed with 500-5000ppm of oil-soluble catalyst and then enters a suspended bed reactor A without solid catalyst loading for reaction; (2) The return oil is directly mixed with the effluent of the suspension bed reactor A without heat exchange, and then enters the suspension bed reactor B without solid catalyst loading at a temperature of 320-360°C for reaction; (3) The top outflow of the suspended bed reactor B enters the fixed bed reactor C filled with solid catalyst for hydrotreating; the bottom oil of the suspended bed reactor B is separated to obtain heavy oil A and oil residue; (4) The effluent from the fixed bed reactor C is divided into two parts. One part is separated to obtain gas phase A and liquid phase A; the other part is separated to obtain heavy oil B and oil residue; (5) A portion of the liquid phase A is used as circulating oil, and the other portion is decompressed and separated to obtain gas phase B and liquid phase B. The liquid phase B is treated in a vacuum distillation tower to obtain side oil and bottom oil. The bottom oil is separated to obtain heavy oil C and oil residue. The heavy oil C is used as return oil. The side oil enters the atmospheric distillation tower for fractionation to obtain light fractions, bio-jet fuel, low-condensation diesel and high-condensation diesel. (6) Part of the bottom oil of the atmospheric distillation tower is mixed with hydrogen and enters the hydroisomerization reactor D filled with a reduced solid catalyst for reaction at a certain temperature. The effluent of the hydroisomerization reactor D is mixed with the gas phase A to obtain a hydrocracked material. The hydrocracked material is cooled and enters the refined isomerized material high-pressure separator to obtain a gas phase C and a liquid phase C. The liquid phase C enters the refined isomerized material low-pressure separator and the stripping stabilizer to obtain a gas phase D and a liquid phase D. The liquid phase D enters the atmospheric distillation tower for separation to obtain light fractions, bio-jet fuel, low-condensation diesel and high-condensation diesel. The suspended bed reactor A, the suspended bed reactor B, the fixed bed reactor C and the hydroisomerization reactor D are all under ultra-low pressure conditions, with a pressure of 3-8 MPa; The biomass inferior oil has a silicon content of 20-100 ppm, a sodium content of 20-60 ppm, a calcium content of 40-200 ppm, and a sulfur content of 50-200 ppm; The preparation method of the oil-soluble catalyst comprises the following steps: firstly synthesizing a bimetallic or trimetallic composite oxide precursor containing two or more non-noble transition metals through a solvothermal process in a water-ethanol-toluene mixed solution, and then modifying the precursor with an organic ion ligand in methanol to obtain an oil-soluble catalyst; The bimetallic or trimetallic composite oxide precursor is one or more of basic ammonium cobalt molybdate [(NH4)HCo2(OH)2Mo2O8], basic ammonium nickel molybdate [(NH4)HNi2(OH)2Mo2O8], basic ammonium cobalt tungstate [(NH4)HCo2(OH)2W2O8], basic ammonium nickel tungstate [(NH4)HNi2(OH)2W2O8], basic ammonium cobalt molybdenum tungstate [(NH4)HCo2(OH)2MoWO8], and basic ammonium nickel molybdenum tungstate [(NH4)HNi2(OH)2MoWO8]; The organic ion ligand is one or more of dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, 1-butyl-3-methylimidazolium chloride, and 1-alkyl-2,3-dimethylimidazolium bromide.

2. The low-pressure hydroisomerization / cracking process according to claim 1, characterized in that: The oil-soluble catalyst synthesis steps include: (1) Dissolve 0.1 mol of cobalt nitrate or nickel nitrate in 50 mL of ethanol to obtain solution A, and dissolve 0.1 mol of ammonium molybdate and / or ammonium metatungstate in 50 mL of deionized water to obtain solution B; (2) 50 mL of toluene was added to solution A to obtain solution C, and then solution B was added dropwise to solution C to obtain mixture D; (3) Add mixture D into a 200 mL hydrothermal crystallization reactor lined with polytetrafluoroethylene, seal it, and place it in an oven at 160°C for 2 hours; (4) After the crystallization kettle is taken out and cooled naturally, the obtained product is filtered, washed, and dried to obtain a bimetallic or trimetallic composite oxide precursor; (5) 0.4 mol of organic ionic ligand was dissolved in methanol, and then 0.1 mol of bimetallic or trimetallic composite oxide precursor was added. The mixture was refluxed at 60°C for 6 hours, and then centrifuged to obtain an oil-soluble catalyst.

3. The low-pressure hydroisomerization / cracking process according to claim 1, characterized in that: The mass ratio of the biomass inferior oil to the recycled oil in step (1) is 1:(1-5).

4. The low-pressure hydroisomerization / cracking process according to claim 1, characterized in that: The ultra-low pressure condition is 4-6 MPa.

5. The low-pressure hydroisomerization / cracking process according to claim 1, characterized in that: The temperature of the fixed bed reactor C is 260-320°C, and the temperature of the hydroisomerization reactor D is 240-340°C.

6. The low-pressure hydroisomerization / cracking process according to claim 1, characterized in that: The solid catalyst used in the fixed-bed reactor C is a nickel-molybdenum-supported alumina catalyst, which needs to be presulfurized before use; the catalyst used in the hydroisomerization reactor D is a reduced non-precious metal bifunctional catalyst.

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