Method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fat

Abstract

The application discloses a method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal oil and fat, and belongs to the technical field of animal oil and fat recycling. The method comprises the following steps: (1) preheating the high-acid-value animal oil and fat, then mixing the high-acid-value animal oil and fat with an ionic liquid catalyst in a suspension bed reactor to perform primary hydrogenation, and obtaining a primary hydrogenation product after separation; (2) adding the primary hydrogenation product into a fixed bed reactor containing a carbon-based catalyst to perform secondary hydrogenation and obtain a secondary hydrogenation product; and (3) obtaining bio-jet fuel by fractionating the secondary hydrogenation product. The method adopts ionic liquid catalysts and carbon-based catalysts to perform hydrogenation treatment on the high-acid-value animal oil and fat, can adapt to the complex components of the high-acid-value animal oil and fat, improve the tolerance of the catalysts to reduce catalyst deactivation, perform efficient catalytic hydrogenation conversion on the high-acid-value animal oil and fat, and thus improve the selectivity and yield of bio-jet fuel fractions.

Description

Technical Field

[0001] This application relates to a method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats, belonging to the field of animal fat recycling technology. Background Technology

[0002] Animal fats (such as beef tallow, mutton tallow, lard, and poultry fat) are byproducts of slaughtering and meat processing. In recent years, with the advancement of the aviation industry's carbon neutrality goals, animal fats have become one of the important raw materials for the production of biofuel. Their application is mainly based on mature conversion processes and good fuel compatibility. Currently, the mainstream processes for producing biofuel from animal fats include hydrogenation, gas-fired Fischer-Tropsch synthesis, and bioconversion. Among these, hydrogenation is the most widely used. Through steps such as hydrodeoxygenation, hydrocracking, and hydroisomerization, fats can be converted into hydrocarbon fuels that meet aviation standards, as illustrated by patents US11549062B2, KR102487444B1, and CA2670985A1.

[0003] In practical applications, animal fats, represented by waste animal fats, have already achieved commercial test flights and applications. For example, China has successfully conducted commercial passenger flights fueled by bio-jet fuel converted from waste animal fats. This fuel can be mixed with traditional petrochemical jet fuel at a ratio of 5%-50%, requiring no modifications to aircraft engines or fuel supply systems. It is "ready to use immediately after refueling" and its performance indicators fully meet civil aviation airworthiness requirements, reducing carbon emissions by 50%-80% compared to traditional jet fuel. Furthermore, regulations in regions such as the EU explicitly support the application of animal fats in aviation and maritime fuels, providing policy guarantees for their large-scale promotion.

[0004] High-acid-value animal fats typically refer to fats with an acid value greater than 10 mg KOH / g. They are mostly derived from spoiled waste oils and processing byproducts. Although their sources are more widespread and their costs are lower, they face numerous technical bottlenecks in the production of bio-jet kerosene. The core issue stems from their high content of free fatty acids. The following problems exist when hydrogenating such high-acid-value animal fats to produce bio-jet kerosene: 1) High risk of equipment corrosion Free fatty acids are highly corrosive and can cause damage to reaction equipment, pipelines, and catalysts. The corrosive effect is even more pronounced in high-temperature and high-pressure hydrogenation processes, requiring the use of special materials such as corrosion-resistant ceramics and super duplex stainless steel, which significantly increases investment costs.

[0005] 2) Short catalyst lifespan Free fatty acids readily interact with hydrogenation catalysts (such as noble metals, metal oxides, and molecular sieve supports), leading to catalyst structure damage, pulverization, poisoning, and occupation of active sites. At the same time, soaps generated during the reaction can also cover the surface of the solid catalyst support, reducing catalytic efficiency and lifespan, and increasing process operating costs.

[0006] 3) Decreased reaction efficiency and product quality High-acid-value oils have a more complex composition. In addition to free fatty acids, they may contain more impurities (such as protein residues and metal ions). These impurities can affect the performance and reaction process of hydrodeoxygenation, hydrocracking, and hydroisomerization catalysts, leading to a decrease in oil conversion rate and a reduction in the selectivity of biofuel fractions. They may also introduce harmful substances, affecting the stability and safety of the target fuel.

[0007] To address the corrosiveness of high-acid-value animal fats in existing technologies, pretreatment agents are typically added to neutralize and lower the acid value. For example, CN119351132A discloses the use of Group IIA or Group IV metal oxides or hydroxides as a deacidification pretreatment, which significantly reduces the acid value of the animal fats after pretreatment, resulting in a higher yield of bio-jet fuel fractions. However, current acid-value reduction methods suffer from low reaction efficiency and long processing times, increasing the cost of producing bio-jet fuel from animal fats. Furthermore, this acid-value reduction process cannot remove impurities from the raw materials, and the presence of these impurities can affect the efficiency of subsequent hydrogenation reactions.

[0008] The applicant discovered that ionic liquid catalysts can rapidly dissolve in animal fats, enabling efficient catalytic hydrogenation for the production of bio-jet kerosene. However, existing ionic liquid catalysts still suffer from low catalytic efficiency, insufficient selectivity in subsequent hydroisomerization, and high product freezing points when catalyzing high-acid-value animal fats. For example, the ionic liquid catalysts disclosed in patents CN119680635B and CN120662370A exhibit the aforementioned limitations, which severely restricts the large-scale application of high-acid-value animal fats in bio-jet kerosene production.

[0009] Therefore, it is necessary to further develop low-cost hydrogenation catalysts and high-efficiency acid-resistant catalysts to improve economic efficiency and promote the large-scale application of animal fats in aviation decarbonization. Summary of the Invention

[0010] To address the aforementioned issues, a method for producing bio-jet fuel using catalytic hydrogenation of high-acid-value animal fats is provided. This method employs both ionic liquid catalysts and carbon-based catalysts to hydrogenate the high-acid-value animal fats, adapting to the complex composition of high-acid-value fats, improving catalyst tolerance to reduce catalyst deactivation, and enabling efficient catalytic hydrogenation conversion of high-acid-value fats, thereby improving the selectivity and yield of bio-jet fuel fractions.

[0011] This application provides a method for producing bio-jet fuel using high-acid-value animal fats via catalytic hydrogenation, comprising the following steps: (1) The high-acid-value animal fats are preheated and then mixed with an ionic liquid catalyst in a suspended bed reactor for primary hydrogenation. The primary hydrogenation product is obtained after separation. (2) The primary hydrogenation product is added to a fixed-bed reactor containing a carbon-based catalyst to carry out secondary hydrogenation to obtain the secondary hydrogenation product; (3) Bio-jet fuel is obtained by fractionating the secondary hydrogenation product; The preparation method of the ionic liquid catalyst is as follows: S1: N (2,3-epoxypropyl)phthalimide (CAS: 161596-47-0) and phytic acid (CAS: 83-86-3) react to obtain reactive monomer A; S2: Reacting and processing monomer A with haloalkane monomers yields intermediate B, which is then treated with a strongly basic anion exchange resin to obtain intermediate C. S3: Add the metal salt to intermediate C, mix and heat to react, then dry to obtain the final product.

[0012] This application adopts N The reaction of (2,3-epoxypropyl)phthalimide with phytic acid yields a novel monomer A. The tertiary amine in monomer A reacts with a haloalkane to give intermediate B, which is then treated with a strongly basic anion exchange resin and a metal acid salt to obtain the final ionic liquid catalyst. The structure of monomer A can form a steric barrier around the nitrogen atom, allowing H atoms under acidic conditions to... + The difficulty in approaching the N atom reduces the probability of protonation and improves the acid resistance of the ionic liquid catalyst. On the other hand, the phytic acid structure increases the steric hindrance of the reactant monomer A, which can hinder the contact between impurity molecules and active sites, reduce impurity adsorption, and thus improve the impurity tolerance of the ionic liquid catalyst.

[0013] Phytic acid contains phosphate groups that have a charge-dispersing effect, which can uniformly disperse the positive charge of cations throughout the molecular framework, avoiding acid corrosion or impurity adsorption caused by localized charge concentration. Furthermore, it can form an "anchoring" effect with cations, enhancing the overall acid resistance of the ionic liquid structure and thus resisting H+ under acidic conditions. +The dissociation of ion pairs maintains the structural integrity of the ionic liquid catalyst. Meanwhile, the adsorption of metal ions by traditional ionic liquid catalysts prepared from tertiary amines is irreversible, leading to permanent blockage of active sites. In contrast, the reaction monomer A prepared in this application replaces the traditional tertiary amine. Its phytic acid structure contains phosphate groups, and the chelates formed by these groups with metal ions are easily desorbed during the reaction. Therefore, the ionic liquid catalyst possesses a "self-cleaning" ability to resist the erosion of impurities.

[0014] Optionally, the N The molar ratio of (2,3-epoxypropyl)phthalimide to phytic acid is 1:(1-1.2).

[0015] The above molar ratio can achieve N The epoxy group in (2,3-epoxypropyl)phthalimide reacts with a phosphate group in phytic acid, resulting in a reactive monomer A molecule containing only one phytic acid structure. Only reactive monomer A with this structure can achieve a dual improvement in acid resistance and impurity tolerance.

[0016] Optionally, the reaction temperature in step S1 is 40-50℃, the reaction time is 4-6h, and triethylamine is added at 3-5wt% of the mass of phytic acid.

[0017] The above-mentioned reaction temperature and reaction time can improve the production efficiency of reactant monomer A and reduce production costs.

[0018] Optionally, the metal salt is a trimetallic acid salt, which is selected from at least one of molybdenum nickel cobaltate, molybdenum nickel manganate, and molybdenum nickel zincate; Optionally, the preparation method of the trimetallic acid salt is as follows: Hydrogen peroxide, nickel sulfate, and a third metal sulfate are added to deionized water and then slowly added dropwise to a boiling ammonium molybdate solution. The ammonium molybdate solution is kept boiling during the dropwise addition. After the dropwise addition is complete, boiling is continued for 1-2 hours to obtain the trimetallic acid salt. The third metal sulfate is selected from one of cobalt sulfate, manganese sulfate, or zinc sulfate.

[0019] Optionally, the molar ratio of nickel sulfate to ammonium molybdate is (0.5-0.8):1, the molar ratio of cobalt sulfate, manganese sulfate or zinc sulfate to ammonium molybdate is (0.3-0.4):1, the hydrogen peroxide accounts for 8-10 wt% of the mass of ammonium molybdate, and the concentration of hydrogen peroxide in the hydrogen peroxide is 30 wt%.

[0020] Specifically, in step S2 of this application, the haloalkane monomer that reacts with reactant monomer A can be a conventional haloalkane in the prior art, such as an iodoalkane containing 1-14 carbon atoms, a bromoalkane containing 1-14 carbon atoms, or a chloroalkane containing 1-14 carbon atoms.

[0021] Preferably, the haloalkane monomer includes at least one selected from iodomethane, bromooctane, bromodecane, bromododecane, and bromotetradecane.

[0022] Optionally, the haloalkane monomer is obtained by reacting a carboxyl-containing haloalkane with a monohydroxy compound containing a thioether bond.

[0023] Based on the novel tertiary amine structure, the use of the aforementioned haloalkane in the ionic liquid catalyst allows it to possess a side chain containing a sulfide bond. This, on the one hand, promotes uniform charge distribution within the ionic liquid catalyst through electron-donating conjugation, avoiding the influence of acidic H+. + It can target and attack ionic liquids while reducing the adsorption sites of polar impurities (such as metal ions and polar small molecules); on the other hand, it can maintain the dispersibility and flowability of ionic liquid catalysts under the influence of their steric hindrance and hydrophobic properties, thus ensuring the stability of catalysis; furthermore, it can improve the integrity and antioxidant properties of the molecular skeleton of ionic liquid catalysts, thereby improving the acid degradation resistance of ionic liquid catalysts in high acid value animal fats and oils, improving their stability in complex environments, and thus improving the yield and quality of jet fuel.

[0024] Optionally, the monohydroxy compound containing a thioether bond includes at least one of ethyl 2-hydroxyethyl thioether (CAS: 110-77-0) and 2-methylthioethanol (CAS: 5271-38-5).

[0025] The selection of the above compounds can improve the reactivity with carboxyl-containing haloalkanes, thereby increasing the yield of haloalkanes and reducing production costs.

[0026] Specifically, the preparation method of the haloalkane monomer is as follows: A carboxyl-containing haloalkane and a thioether-containing monohydroxy compound in a molar ratio of 1:(1.1-1.2) were added to a solvent, concentrated sulfuric acid was added as a catalyst, and the reaction was carried out at 60-70℃ for 4-6 hours to obtain a crude product, which was then filtered, washed and dried to obtain the final product.

[0027] Optionally, the carboxyl-containing haloalkane is selected from at least one of 6-chlorohexanoic acid, 7-chloroheptanoic acid, 8-chlorooctanoic acid, 9-chlorononanoic acid, 10-chlorodecanoic acid, 11-chloro-undecanoic acid, 6-bromohexanoic acid, 7-bromoheptanoic acid, 8-bromooctanoic acid, 9-bromononanoic acid, 10-bromodecanoic acid, and 11-bromo-undecanoic acid.

[0028] Optionally, the carbon-based catalyst surface is modified with epoxy groups, and the carbon-based catalyst surface is loaded with an active metal component accounting for 10-25 wt% of the activated carbon support.

[0029] The carbon-based catalyst used in this application has stronger acid resistance and impurity tolerance than other solid catalysts (such as oxide-based or molecular sieve-based catalysts). It can exist stably in the acidic environment of high free fatty acids, and therefore can be used for multiple cycles of catalysis in high acid value animal fats and oils, while maintaining high catalytic activity.

[0030] The epoxy groups modified on the surface of the carbon-based catalyst can undergo ring-opening reactions with the remaining phosphate groups of the phytic acid structure in monomer A of the ionic liquid catalyst during catalytic hydrogenation. Therefore, the ionic liquid catalyst added in step (1) can be chemically linked with the carbon-based catalyst in step (2) to achieve the recovery of the ionic liquid catalyst. First, it can realize the reuse of the ionic liquid catalyst and reduce production costs; second, it can avoid the ionic liquid catalyst residue in the product and improve the product quality; third, the ionic liquid catalyst can assist the carbon-based catalyst in catalytic hydrogenation in step (2) to further improve the product yield and product quality.

[0031] Optionally, the carbon-based catalyst is prepared by: D1: Activated carbon is impregnated in a solution containing active metal components for at least 2 hours, filtered, dried, calcined in nitrogen, and reduced in hydrogen to obtain supported activated carbon; D2: The supported activated carbon is modified with an aminosilane coupling agent to obtain aminated activated carbon. Finally, the aminated activated carbon is added to the diepoxide compound and reacted at 20-40℃ for at least 0.5h. After filtration and drying, a carbon-based catalyst with surface-modified epoxy groups is obtained. The molar ratio of the diepoxide compound to the aminosilane coupling agent is (0.95-1):1.

[0032] In the above preparation method, after loading the metal active component, the activated carbon is then subjected to amination and epoxidation treatments in sequence. Under controlled reaction conditions and dosage, the amino groups on the surface of the amination activated carbon can undergo a ring-opening reaction with one of the epoxy groups in the double epoxy compound to form a chemical bond. Due to steric hindrance, the other epoxy group in the double epoxy compound will not react with the amination activated carbon. Therefore, the carbon-based catalyst surface can be modified with unreacted epoxy groups, thereby achieving the anchoring and recovery of the ionic liquid catalyst.

[0033] Optionally, the aminosilane coupling agent includes at least one of γ-aminopropyltriethoxysilane (CAS: 919-30-2) and 3-aminopropyl(diethoxy)methylsilane (CAS: 3179-76-8).

[0034] Optionally, the amount of the aminosilane coupling agent added is 30-40 wt% of the activated carbon, the treatment temperature is 20-30℃, and the treatment time is 1-3 h.

[0035] Optionally, the biepoxide compound includes at least one of diepoxide glycerol ether (CAS: 2238-07-5), ethylene glycol diglycidyl ether (CAS: 2224-15-9), and 1,4-butanediol diglycidyl ether (CAS: 2425-79-8).

[0036] The two biepoxide compounds mentioned above can reduce the production cost of carbon-based catalysts, reduce the production difficulty of carbon-based catalysts, and increase the number of epoxy groups modified on the surface of carbon-based catalysts, thereby improving the recovery rate of ionic liquid catalysts.

[0037] Optionally, in step (1), the amount of ionic liquid catalyst added is 400-1000 ppm, the reaction temperature is 340-360℃, the pressure is 2-6 MPa, and the liquid hourly space velocity is 1.0-1.5 h⁻¹. -1 The hydrogen-to-oil ratio is (1000-1500):1.

[0038] Optionally, in step (2), the reaction temperature is 280-300℃, the pressure is 2-6MPa, and the liquid hourly space velocity is 1.0-1.5h. -1 The hydrogen-to-oil ratio is (1000-2000):1.

[0039] The reaction conditions in steps (1) and (2) above are set according to the properties of ionic liquid catalysts and carbon-based catalysts. Under the constraints of the above parameters, continuous production of bio-jet fuel from high-acid-value animal fats can be achieved, thereby improving production efficiency, product quality and raw material utilization.

[0040] The beneficial effects of this application include, but are not limited to: 1. The method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats according to this application employs a novel ionic liquid catalyst with high acid corrosion resistance and strong stability. It can withstand the reaction environment of high-acid-value fat treatment to reduce catalyst deactivation, and has both catalytic and solubilizing effects, thereby improving reaction catalytic efficiency and product quality, and further reducing the residence time of high-acid-value animal fats in the equipment and reducing equipment corrosion.

[0041] 2. According to the method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats in this application, the carbon-based catalyst used in the hydroisomerization process has strong acid resistance and impurity tolerance, can exist stably in an acidic environment with high free fatty acids, and can maintain high catalytic activity even after multiple cycles of use, significantly extending service life and reducing catalyst consumption costs; in addition, the catalytic active sites of the carbon-based catalyst are uniformly dispersed, which can accurately act on the hydrodeoxygenation and hydroisomerization reactions of free fatty acids, improve the fat conversion rate and bio-jet fuel fraction selectivity, and at the same time reduce the formation of soap substances and avoid the catalyst surface active sites being covered.

[0042] 3. The method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats according to this application utilizes both novel ionic liquid catalysts and carbon-based catalysts, which can function under relatively mild reaction conditions, reducing process energy consumption and further optimizing the economic and environmental benefits of producing bio-jet fuel from high-acid-value animal fats. Furthermore, it is highly compatible with existing hydrogenation processes, requiring no major modifications to the production process and facilitating industrial-scale promotion.

[0043] 4. According to the method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats in this application, the structure of the ionic liquid catalyst is improved so that, on the basis of improving its acid resistance and impurity resistance, it can be combined with the carbon-based catalyst to play a synergistic role, and can be recycled by relying on the carbon-based catalyst, thereby reducing the cost of catalyst use. Attached Figure Description

[0044] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 The reaction equation for monomer A involved in Example 1 of this application is shown. Detailed Implementation

[0045] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0046] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application were all purchased commercially.

[0047] Unless otherwise specified, the methods used in the embodiments and comparative examples of this application are conventional methods in the prior art. The high-acid-value animal fats used in the following embodiments and comparative examples are from the same batch and of the same nature, with an acid value of 45 mg KOH / g.

[0048] The silane coupling agent and diepoxide compound in the following examples and comparative examples are liquids. Therefore, the direct addition method described in the examples and comparative examples can also be used to dissolve the silane coupling agent and diepoxide compound in a solvent and then perform amination and epoxidation treatments to obtain the carbon-based catalyst of this application.

[0049] Example 1 This embodiment relates to a method for producing bio-jet fuel using high-acid-value animal fats via catalytic hydrogenation, comprising the following steps: (1) The high-acid-value animal fat was preheated to 60°C and then mixed with an ionic liquid catalyst. The amount of ionic liquid catalyst added was 1000 ppm. The mixture was heated at 340°C, 6 MPa, and a liquid hourly space velocity of 1.5 h⁻¹. -1Primary hydrogenation was carried out in a slurry bed reactor under a hydrogen-to-oil ratio of 1000:1, and the primary hydrogenation product was obtained after separation. (2) The primary hydrogenation product was added to a fixed-bed reactor containing a carbon-based catalyst and subjected to a reaction at 280°C, 6 MPa, and a liquid hourly space velocity of 1.5 h⁻¹. -1 Secondary hydrogenation is carried out under a hydrogen-to-oil ratio of 1000:1 to obtain the secondary hydrogenation product; (3) Fractionate the secondary hydrogenation product and collect the fraction at 130℃-300℃ to obtain bio-jet fuel.

[0050] The preparation method of the ionic liquid catalyst is as follows: S1: Add 0.1 mol of N (2,3-epoxypropyl)phthalimide and 0.12 mol of phytic acid were added to a mixed solvent of ethanol and water (ethanol to water volume ratio 3:1), followed by the addition of triethylamine (3 wt% of phytic acid). The mixture was stirred at 40 °C for 6 h. The solvent was removed by filtration and rotary evaporation, and the mixture was extracted three times with a mixed solvent of diethyl ether and water (ether to water volume ratio 1:1). The reactants were dried to obtain the monomers. The reaction equation is detailed in [link to reaction equation]. Figure 1 ; S2: Dissolve 0.08 mol of reactant monomer A and 0.08 mol of iodomethane in a mixed solvent of ethanol and acetone (volume ratio of ethanol to acetone is 1:1), heat under reflux for 24 h, rotary evaporate, extract three times with a mixed solvent of diethyl ether and acetonitrile (volume ratio of 1:1), and then dry to obtain intermediate B. Dissolve intermediate B in ethanol and add it to an ion exchange column packed with OH- type strong basic anion exchange resin. Elute with ethanol, collect the strong basic eluent with pH>8, and dry at 80℃ for 24 h to obtain intermediate C. S3: 8 wt% hydrogen peroxide (30 wt% hydrogen peroxide concentration), 0.05 mol nickel sulfate, and 0.04 mol zinc sulfate were added to deionized water and then slowly added dropwise to a boiling 0.1 mol ammonium molybdate solution at a rate of 2 drops / second. The ammonium molybdate solution was kept boiling during the addition. After the addition was complete, boiling was continued for 1 hour to obtain the trimetallic acid salt. Intermediate C and the trimetallic acid salt were mixed in a molar ratio of 3:1, stirred at room temperature for 6 hours, heated to 60°C and reacted for 12 hours. Water was then removed by rotary evaporation, and finally dried under vacuum at 80°C for 24 hours to obtain the ionic liquid catalyst.

[0051] The preparation method of the carbon-based catalyst is as follows: D1: The activated carbon carrier was impregnated in a solution of cobalt nitrate hexahydrate, treated at 25°C for 2 hours, aged at room temperature for 12 hours, dried at 80°C for 12 hours, calcined at 500°C in nitrogen for 4 hours, and reduced at 450°C in hydrogen for 4 hours to obtain the supported activated carbon. The amount of cobalt nitrate hexahydrate added was 20 wt% of the mass of the activated carbon carrier, calculated based on cobalt. D2: The supported activated carbon was placed in a beaker, and γ-aminopropyltriethoxysilane (30 wt% of the activated carbon mass) was added. The mixture was shaken at 20°C for 3 h, filtered, and dried at 80°C for 6 h to obtain aminated activated carbon. Finally, the aminated activated carbon was added to diglycidyl ether, with a molar ratio of diglycidyl ether to γ-aminopropyltriethoxysilane of 0.95:1. The mixture was stirred at 20°C for 3 h, filtered, and dried at 80°C for 6 h to obtain a carbon-based catalyst.

[0052] Example 2 This embodiment relates to a method for producing bio-jet fuel using high-acid-value animal fats via catalytic hydrogenation, comprising the following steps: (1) The high-acid-value animal fat was preheated to 80°C and then mixed with an ionic liquid catalyst. The amount of ionic liquid catalyst added was 400 ppm. The mixture was prepared at 360°C, 2 MPa, and a liquid hourly space velocity of 1.0 h⁻¹. -1 Primary hydrogenation was carried out in a suspended bed reactor under a hydrogen-to-oil ratio of 1500:1, and the primary hydrogenation product was obtained after separation. (2) The primary hydrogenation product was added to a fixed-bed reactor containing a carbon-based catalyst and subjected to a reaction at 300°C, 2 MPa, and a liquid hourly space velocity of 1.0 h⁻¹. -1 Secondary hydrogenation was carried out under a hydrogen-to-oil ratio of 2000:1 to obtain the secondary hydrogenation product; (3) Fractionate the secondary hydrogenation product and collect the fraction at 130℃-300℃ to obtain bio-jet fuel.

[0053] The preparation method of the ionic liquid catalyst is as follows: S1: Add 0.1 mol of N (2,3-epoxypropyl)phthalimide and 0.1 mol of phytic acid were added to a mixed solvent of ethanol and water (volume ratio of ethanol to water: 3:1), followed by the addition of 5 wt% triethylamine. The mixture was stirred at 50 °C for 4 h, filtered, and the solvent was removed by rotary evaporation. The mixture was then extracted three times with a mixed solvent of diethyl ether and water (volume ratio of diethyl ether to water: 1:1) and dried to obtain the reactant monomer. S2: Dissolve 0.08 mol of reactant monomer A and 0.08 mol of bromooctane in a mixed solvent of ethanol and acetone (volume ratio of ethanol to acetone is 1:1), heat under reflux for 24 h, rotary evaporate, extract three times with a mixed solvent of diethyl ether and acetonitrile (volume ratio of 1:1), and then dry to obtain intermediate B. Dissolve intermediate B in ethanol and add it to an ion exchange column packed with OH- type strong basic anion exchange resin. Elute with ethanol, collect the strong basic eluent with pH>8, and dry at 80℃ for 24 h to obtain intermediate C. S3: 10 wt% hydrogen peroxide (30 wt% hydrogen peroxide concentration), 0.08 mol nickel sulfate, and 0.03 mol manganese sulfate were added to deionized water and then slowly added dropwise to a boiling 0.1 mol ammonium molybdate solution at a rate of 1 drop / second. The ammonium molybdate solution was kept boiling during the addition. After the addition was completed, boiling was continued for 2 hours to obtain the trimetallic acid salt. Intermediate C and the trimetallic acid salt were mixed in a molar ratio of 4:1, stirred at room temperature for 6 hours, heated to 70°C and reacted for 10 hours, then the water was removed by rotary evaporation, and finally the mixture was vacuum dried at 80°C for 24 hours to obtain the ionic liquid catalyst.

[0054] The preparation method of the carbon-based catalyst is as follows: D1: The activated carbon carrier was impregnated in a solution of cobalt nitrate hexahydrate, treated at 25°C for 2 hours, aged at room temperature for 12 hours, dried at 80°C for 12 hours, calcined at 500°C in nitrogen for 4 hours, and reduced at 450°C in hydrogen for 4 hours to obtain the supported activated carbon. The amount of cobalt nitrate hexahydrate added was 20 wt% of the mass of the activated carbon carrier, calculated based on cobalt. D2: The supported activated carbon was placed in a beaker, and 40 wt% of 3-aminopropyl(diethoxy)methylsilane was added. The mixture was shaken at 30°C for 1 h, filtered, and dried at 80°C for 6 h to obtain aminated activated carbon. Finally, the aminated activated carbon was added to ethylene glycol diglycidyl ether, with a molar ratio of ethylene glycol diglycidyl ether to 3-aminopropyl(diethoxy)methylsilane of 1:1. The mixture was stirred at 40°C for 0.5 h, filtered, and dried at 80°C for 6 h to obtain a carbon-based catalyst.

[0055] Example 3 This embodiment relates to a method for producing bio-jet fuel using high-acid-value animal fats via catalytic hydrogenation, comprising the following steps: (1) The high-acid-value animal fat was preheated to 80°C and then mixed with an ionic liquid catalyst. The amount of ionic liquid catalyst added was 800 ppm. The mixture was prepared at 350°C, 4 MPa, and a liquid hourly space velocity of 1.5 h⁻¹. -1 Primary hydrogenation was carried out in a slurry bed reactor under a hydrogen-to-oil ratio of 1200:1, and the primary hydrogenation product was obtained after separation. (2) The primary hydrogenation product was added to a fixed-bed reactor containing a carbon-based catalyst and subjected to a reaction at 290 °C, 4 MPa, and a liquid hourly space velocity of 1.5 h⁻¹. -1 Secondary hydrogenation was carried out under a hydrogen-to-oil ratio of 1500:1 to obtain the secondary hydrogenation product; (3) Fractionate the secondary hydrogenation product and collect the fraction at 130℃-300℃ to obtain bio-jet fuel.

[0056] The preparation method of the ionic liquid catalyst is as follows: S1: Add 0.1 mol of N (2,3-epoxypropyl)phthalimide and 0.1 mol of phytic acid were added to a mixed solvent of ethanol and water (ethanol to water volume ratio of 3:1), followed by the addition of triethylamine at 4 wt% of the phytic acid mass. The mixture was stirred at 45 °C for 5 h, filtered, and the solvent was removed by rotary evaporation. The mixture was then extracted three times with a mixed solvent of diethyl ether and water (diethyl ether to water volume ratio of 1:1) and dried to obtain reactant monomer A. S2: Dissolve 0.08 mol of reactant monomer A and 0.08 mol of bromooctane in a mixed solvent of ethanol and acetone (volume ratio of ethanol to acetone is 1:1), heat under reflux for 24 h, rotary evaporate, extract three times with a mixed solvent of diethyl ether and acetonitrile (volume ratio of 1:1), and then dry to obtain intermediate B. Dissolve intermediate B in ethanol and add it to an ion exchange column packed with OH- type strong basic anion exchange resin. Elute with ethanol, collect the strong basic eluent with pH>8, and dry at 80℃ for 24 h to obtain intermediate C. S3: 10% hydrogen peroxide (30wt% hydrogen peroxide concentration), 0.06 mol nickel sulfate, and 0.04 mol cobalt sulfate (by mass of ammonium molybdate) were added to deionized water, and then slowly added dropwise to a boiling 0.1 mol ammonium molybdate solution at a dropping rate of 2 drops / second. The ammonium molybdate solution was kept boiling during the addition process. After the addition was completed, boiling was continued for 1.5 h to obtain the trimetallic acid salt. Intermediate C and the trimetallic acid salt were mixed in a molar ratio of 4:1, stirred at room temperature for 6 h, heated to 65 °C and reacted for 10 h, then the water was removed by rotary evaporation, and finally dried under vacuum at 80 °C for 24 h to obtain the ionic liquid catalyst.

[0057] The preparation method of the carbon-based catalyst is as follows: D1: The activated carbon carrier was impregnated in a solution of nickel nitrate hexahydrate, treated at 35°C for 2 hours, aged at room temperature for 12 hours, dried at 80°C for 12 hours, calcined at 500°C in nitrogen for 4 hours, and reduced at 450°C in hydrogen for 4 hours to obtain the supported activated carbon. The amount of nickel nitrate hexahydrate added was 20 wt% of the mass of the activated carbon carrier, calculated based on nickel content. D2: The supported activated carbon was placed in a beaker, and γ-aminopropyltriethoxysilane (35 wt% of the activated carbon mass) was added. The mixture was shaken at 30°C for 2 h, filtered, and dried at 80°C for 6 h to obtain aminated activated carbon. Finally, the aminated activated carbon was added to 1,4-butanediol diglycidyl ether, with a molar ratio of 1:1 between 1,4-butanediol diglycidyl ether and γ-aminopropyltriethoxysilane. The mixture was stirred at 30°C for 1.5 h, filtered, and dried at 80°C for 6 h to obtain a carbon-based catalyst.

[0058] Example 4 The difference between this embodiment and Example 3 is that a haloalkane containing a carboxyl group is reacted with a monohydroxy compound containing a thioether bond to replace bromooctane. The specific preparation method is as follows: 0.1 mol of 6-chlorohexanoic acid and 0.11 mol of 2-hydroxyethyl sulfide were added to a mixed solvent of dimethylformamide and ethanol (volume ratio of dimethylformamide to ethanol was 1:1). Concentrated sulfuric acid, accounting for 2 wt% of 6-chlorohexanoic acid, was added as a catalyst. The mixture was then reacted at 60 °C for 6 h to obtain a crude product. The crude product was filtered, washed three times with ethanol, and dried to obtain the final product.

[0059] Example 5 The difference between this embodiment and Example 3 is that a haloalkane containing a carboxyl group is reacted with a monohydroxy compound containing a thioether bond to replace bromooctane. The specific preparation method is as follows: 0.1 mol of 11-bromo-undecanoic acid and 0.12 mol of 2-methylthioethanol were added to a mixed solvent of dimethylformamide and ethanol (volume ratio of dimethylformamide to ethanol was 1:1). Concentrated sulfuric acid, accounting for 2 wt% of 11-bromo-undecanoic acid, was added as a catalyst. The mixture was then reacted at 70 °C for 4 h to obtain the crude product. The crude product was filtered, washed three times with ethanol, and dried to obtain the final product.

[0060] Example 6 The difference between this embodiment and embodiment 3 is that N The molar ratio of (2,3-epoxypropyl)phthalimide to phytic acid is 1:2, i.e., using 0.1 mol of N2O3. (2,3-epoxypropyl)phthalimide and 0.2 mol of phytic acid.

[0061] Example 7 The difference between this embodiment and Example 3 is that step D2 is not performed in the preparation of the carbon-based catalyst.

[0062] Example 8 The difference between this embodiment and Example 3 is that in step D2 of the preparation of the carbon-based catalyst, the amount of γ-aminopropyltriethoxysilane added is 20 wt% of the activated carbon mass.

[0063] Example 9 The difference between this embodiment and Example 3 is that in step D2 of the preparation of the carbon-based catalyst, the molar ratio of 1,4-butanediol diglycidyl ether to γ-aminopropyltriethoxysilane is 0.5:1.

[0064] Example 10 The difference between this embodiment and Embodiment 3 is that molybdate is used instead of trimetallic acid salt.

[0065] Comparative Example 1 The difference between this comparative example and Example 3 is that pyridine is used as the reaction monomer A.

[0066] Comparative Example 2 The difference between this comparative example and Example 3 is that the ionic liquid catalyst 3# of Example 2 in patent CN119680635B is used as the ionic liquid catalyst.

[0067] Comparative Example 3 The difference between this comparative example and Example 3 is that 1-decyl-3-methylimidazolium phosphomolybdate prepared in Example 4 of patent CN120662370A is used as an ionic liquid catalyst.

[0068] Test Example 1 The bio-jet fuels obtained by the above examples and comparative examples were analyzed using an Agilent 7890A-5975C gas chromatography-mass spectrometry (GC-MS) system with an HP-5-MS column. The isomer selectivity and jet fuel yield were calculated, and the freezing point and thermal oxidation stability of the bio-jet fuels were tested. The test results are shown in Table 1.

[0069] Where isomer selectivity = [(C6-C18) peak area ratio of isomer products / peak area ratio of all products] × 100%, in units of 100%.

[0070] Aviation kerosene yield = [(130℃-300℃) fraction mass / total oil product mass] × liquid phase yield × 100%, in units of 100%.

[0071] Thermal oxidative stability was determined according to national standard GB / T 9169-2023.

[0072] Table 1

[0073] Test Example 2 The carbon-based catalysts prepared in each example and comparative example were continuously used for 720 hours to catalyze high-acid-value animal fats of the same quality. The carbon-based catalysts were not replaced in the cyclic experiment of this test example, but the same amount of ionic liquid catalyst was added every 24 hours. The decrease rate of bio-jet fuel isomer selectivity and the decrease rate of bio-jet fuel yield were tested. The test results are shown in Table 2.

[0074] The rate of decrease in heteroselectivity is calculated as follows: [(heterogeneity in the first hour - heterogeneity in the 720th hour) / heterogeneity in the first hour] × 100%, with units of 1.

[0075] Aviation kerosene yield decline rate = [(aviation kerosene yield in hour 1 - aviation kerosene yield in hour 720) / aviation kerosene yield in hour 1] × 100%, unit is .

[0076] Table 2

[0077] Based on the above test results, it can be seen that the combination of ionic liquid catalyst and carbon-based catalyst in this application can achieve the catalytic production of bio-jet fuel from high-acid-value animal fats, which is suitable for industrial-scale application.

[0078] A comparison of Examples 4 and 5 with Example 3 shows that the side-chain ionic liquid catalyst containing sulfide bonds can further improve the acid degradation resistance and stability of the ionic liquid catalyst under complex environments, thereby improving the yield and quality of jet fuel.

[0079] A comparison of Example 6 and Example 3 shows that when the ionic liquid catalyst contains too much phytic acid structure, the catalytic activity of the ionic liquid will decrease, resulting in a decrease in isomer selectivity and biofuel yield.

[0080] A comparison of Examples 7-9 with Example 3 shows that the absence of step D2 prevents the carbon-based catalyst from anchoring with the ionic liquid catalyst, thus hindering the ionic liquid catalyst's function in the secondary hydrogenation process. Consequently, the isomer selectivity and product yield are the lowest. The reduced amounts of γ-aminopropyltriethoxysilane and 1,4-butanediol diglycidyl ether result in fewer anchored ionic liquid catalysts, which in turn affects the isomer selectivity and jet fuel yield, leading to a greater decrease in isomer selectivity and jet fuel yield after 20 cycles.

[0081] A comparison of Example 10 and Example 3 shows that the trimetallic salt has better catalytic performance and can further improve isomer selectivity and jet fuel yield.

[0082] A comparison of Comparative Example 1 and Example 3 shows that conventional pyridine, as reactant monomer A, has poor catalytic effect on high-acid-value animal fats, resulting in reduced isomer selectivity and jet fuel yield, and a higher freezing point. This demonstrates that the proposed method utilizes N... The reaction monomer A obtained by reacting (2,3-epoxypropyl)phthalimide with phytic acid is more suitable for hydrogenation catalysis of high-acid-value animal fats.

[0083] Based on the comparison of Comparative Examples 2 and 3 and Example 1, it can be seen that conventional ionic liquid catalysts have problems such as low catalytic efficiency, insufficient selectivity of subsequent isomerization, and high freezing point of products when catalyzing high acid value animal fats, making them difficult to use for industrial catalytic applications of high acid value animal fats.

[0084] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats, characterized in that, Includes the following steps: (1) The high-acid-value animal fats are preheated and then mixed with an ionic liquid catalyst in a suspended bed reactor for primary hydrogenation. The primary hydrogenation product is obtained after separation. (2) The primary hydrogenation product is added to a fixed-bed reactor containing a carbon-based catalyst to carry out secondary hydrogenation and obtain the secondary hydrogenation product; (3) Bio-jet fuel is obtained by fractionating the secondary hydrogenation product; The preparation method of the ionic liquid catalyst is as follows: S1: N (2,3-epoxypropyl)phthalimide reacts with phytic acid to give reactant monomer A; S2: Reacting and processing monomer A with haloalkane monomers yields intermediate B, which is then treated with a strongly basic anion exchange resin to obtain intermediate C. S3: Add the metal salt to intermediate C, mix and heat to react, then dry to obtain the final product.

2. The method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats according to claim 1, characterized in that, The N The molar ratio of (2,3-epoxypropyl)phthalimide to phytic acid is 1:(1-1.2).

3. The method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats according to claim 2, characterized in that, The reaction temperature in step S1 is 40-50℃, the reaction time is 4-6h, and triethylamine is added at 3-5wt% of the mass of phytic acid.

4. The method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats according to claim 1, characterized in that, The haloalkane monomers include at least one of iodoalkanes containing 1-14 carbon atoms, bromoalkanes containing 1-14 carbon atoms, and chloroalkanes containing 1-14 carbon atoms.

5. The method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats according to claim 1, characterized in that, The carbon-based catalyst is modified with epoxy groups on its surface, and the surface of the carbon-based catalyst is loaded with an active metal component accounting for 10-25 wt% of the activated carbon support.

6. The method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats according to claim 5, characterized in that, The preparation method of the carbon-based catalyst is as follows: D1: Activated carbon is impregnated in a solution containing active metal components for at least 2 hours, filtered, dried, calcined in nitrogen, and reduced in hydrogen to obtain supported activated carbon; D2: The supported activated carbon is modified with an aminosilane coupling agent to obtain aminated activated carbon. Finally, the aminated activated carbon is added to the diepoxide compound and reacted at 20-40℃ for at least 0.5h. After filtration and drying, a carbon-based catalyst is obtained. The molar ratio of the diepoxide compound to the aminosilane coupling agent is (0.95-1):

1.

7. The method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats according to claim 6, characterized in that, The amount of aminosilane coupling agent added is 30-40 wt% of the activated carbon mass, the treatment temperature is 20-30℃, and the treatment time is 1-3 h.

8. The method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats according to claim 6, characterized in that, The biepoxide compound includes at least one of diepoxide glycerol ether, ethylene glycol diglycidyl ether, and 1,4-butanediol diglycidyl ether.

9. The method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats according to claim 1, characterized in that, The amount of the ionic liquid catalyst added in step (1) is 400-1000 ppm, the reaction temperature is 340-360°C, the pressure is 2-6 MPa, the liquid hourly space velocity is 1.0-1.5 h -1 , and the hydrogen to oil ratio is (1000-1500):

1.

10. The method for producing bio-jet fuel by catalytic hydrogenation of high-acid-value animal fats according to claim 1, characterized in that, In step (2), the reaction temperature is 280-300℃, the pressure is 2-6MPa, and the liquid hourly space velocity is 1.0-1.5h. -1 The hydrogen-to-oil ratio is (1000-2000):1.

Images