Method for synthesizing aviation fuel based on biomass pyrolysis oil

Abstract

The invention relates to a method for synthesizing aviation fuel, in particular to a method for synthesizing aviation fuel based on biomass pyrolytic oil by using a specific catalyst combination and a multi-step catalytic reaction, and belongs to the field of green chemistry and energy engineering. The method comprises the following steps: S1, biomass liquefaction; S2, hydrodeoxygenation; and S3, hydroisomerization. According to the method, the biomass pyrolytic oil is converted into the aviation fuel by using a specific catalyst combination and a multi-step catalytic reaction, so that the preparation cost of the catalyst is reduced, the catalytic efficiency of the catalyst in the reaction process is improved, the performance of the biomass pyrolytic oil in the hydrogenation and isomerization reaction processes is optimized, and the yield of the aviation fuel is improved. The reaction rate of the catalyst in the hydrogenation process is improved, the carbon deposition phenomenon on the surface of the catalyst is reduced, and the service life, stability, anti-coking performance and other properties of the catalyst are improved.

Description

Technical Field

[0001] The present invention relates to a method for synthesizing aviation fuel, in particular a method for synthesizing aviation fuel based on biomass pyrolysis oil by using a specific catalyst combination and multi-step catalytic reactions, belonging to the fields of green chemistry and energy engineering. Background Art

[0002] Biomass pyrolysis oil is a liquid product obtained by the fast pyrolysis of biomass (wood chips, straw, waste agricultural residues), which has a high oxygen content and complex chemical composition, including organic acids, phenols and other oxygen-containing compounds. However, due to the high viscosity, low calorific value and instability of biomass pyrolysis oil, biomass pyrolysis oil cannot be directly used as high-quality fuel, such as aviation fuel. Therefore, improving its quality, removing the oxygen content and increasing the fuel calorific value are the current research focuses.

[0003] In the prior art, most processes improve the quality of biomass pyrolysis oil and increase its utilization rate by hydrogenation or coking treatment of biomass pyrolysis oil, such as the Chinese patent application for invention "A processing method of biomass pyrolysis oil (201911056761.8)". At present, multi-step hydrogenation and hydrodeoxygenation reactions are carried out on biomass pyrolysis oil to achieve the upgrading of biomass oil. However, due to the easy blockage of the reactor and the inactivation of the catalyst, the process continuity is limited. Therefore, it is extremely important to improve the reaction efficiency, anti-carbon deposition performance and other properties of biomass pyrolysis oil during the reaction process. Summary of the Invention

[0004] The present invention aims at the defects of the prior art mentioned in the background art, and provides a method for converting biomass pyrolysis oil into aviation fuel by using a specific catalyst combination and multi-step catalytic reactions, that is, a method for synthesizing aviation fuel based on biomass pyrolysis oil.

[0005] To achieve the above technical purpose, the technical solution adopted by the present invention is: A method for synthesizing aviation fuel based on biomass pyrolysis oil is carried out according to the following steps: S1. Biomass liquefaction S1-1. Crush, dry and screen the biomass raw material; S1-2. Add a solvent for pyrolysis; at the beginning of pyrolysis, the biomass raw material is rapidly heated to 200-250 °C under a negative pressure environment; S1-3. Add an oxidation catalyst accounting for 0.1-0.5% of the mass of the biomass raw material to promote the reaction and generate biomass pyrolysis oil with a low oxide content; S2. Hydrodeoxygenation S2-1. Catalyst preparation: Prepare a palladium and platinum bimetallic catalyst supported on carbon; S2-2 Hydrodeoxygenation reaction: The biomass pyrolysis oil generated in step S1-3 is subjected to hydrodeoxygenation treatment for 1-4 hours using a bimetallic catalyst at an environment of 125-250 °C. After treatment, the water phase of the biomass oil is removed by liquid separation to obtain hydrotreated biomass pyrolysis oil; S3. Hydroisomerization S3-1 Catalyst preparation: Prepare a composite metal catalyst composed of lanthanum, nickel, titanium, and cerium supported on alumina after fluorination treatment; S3-2 Hydroisomerization reaction: At an environment of 200-450 °C, use the composite metal catalyst to perform hydroisomerization reaction on the hydrotreated biomass pyrolysis oil generated in step S2-2, collect the reactants, and obtain isomerized biomass pyrolysis oil as aviation fuel.

[0006] The solvent in step S1-2 is crude glycerol as a by-product of biodiesel.

[0007] The oxidation catalyst in step S1-3 is a mixture of alkali metal hydroxide and transition metal oxide, where the molar ratio of alkali metal hydroxide to transition metal oxide is 1:9 - 9:1.

[0008] In step S2-1, the raw materials of the bimetallic catalyst include activated carbon with a high specific surface area as the catalyst carrier, palladium chloride and chloroplatinic acid as the metal precursor solution, sodium borohydride or hydrogen as the reducing agent, and deionized water; the molar ratio range of palladium and platinum in the metal precursor solution is 1:1 - 1:3.

[0009] The preparation method of the bimetallic catalyst is as follows: (1) Pretreatment of activated carbon Ultrasonically clean the activated carbon in deionized water for 20-30 minutes to remove impurities; dry it at an environment of 100-120 °C for 2-3 hours to remove moisture; (2) Preparation of metal precursor solution Dissolve palladium chloride and chloroplatinic acid in deionized water respectively to prepare precursor solutions with the required concentrations; Mix the prepared precursor solutions of palladium and platinum evenly to obtain the metal precursor solution for use; (3) Preparation of initial catalyst Add the activated carbon treated in step (1) to the metal precursor solution in step (2), stir and impregnate the solution at room temperature for 2-4 hours, and let it stand overnight to obtain the initial catalyst; (4) Drying and calcination The next day, dry the initial catalyst at an environment of 100-120 °C for 6-12 hours; calcine the dried initial catalyst at 200-300 °C for 2 hours to remove the organic part in the precursor and form oxides; immerse the initial catalyst in NaBH 4In the solution, stir for 1 - 2 hours; (5)Reductive roasting Introduce hydrogen into the reduction furnace, and reduce the initial catalyst in step (3) at 300 - 400 °C for 2 - 3 hours; then wash with deionized water and dry at 100 - 120 °C to obtain the bimetallic catalyst.

[0010] Step S2 - 2 Hydrodeoxygenation reaction, the specific steps are as follows: (1)Load the bimetallic catalyst into the reactor and distribute it evenly; (2)After flushing the reactor with nitrogen, preheat the reactor to 125 - 250 °C; (3)After removing the moisture from the biomass pyrolysis oil generated in step S1 - 3, inject it into the reactor at a constant flow rate, and the flow rate is 1 - 10 ton / h; (4)Introduce high - purity hydrogen into the reactor, and control the hydrogen flow rate so that the molar ratio of hydrogen to biomass pyrolysis oil is 2:1 - 5:1; The reactor pressure is controlled at 20 - 100 bar; during the reaction, the stirring speed is maintained at 200 - 500 rpm; the temperature inside the reactor during hydrogenation is maintained between 125 - 250 °C; the hydrogenation treatment time is 1 - 4 hours; (5)Separate the water phase from the treated biomass pyrolysis oil by liquid - liquid separation to obtain hydrogenated biomass pyrolysis oil.

[0011] In step S3 - 1, the preparation steps of the composite metal catalyst are as follows: (1)Fluorination treatment First, mix the high - specific - surface - area alumina support with ammonium fluoride solution, and the concentration of ammonium fluoride is 0.1 - 1M; under stirring conditions, the mixture reacts at room temperature for 2 - 4 hours; Then, filter the treated alumina and dry it at 100 - 120 °C for 6 - 12 hours; Finally, calcine it in air at 400 - 500 °C for 2 - 4 hours to complete the fluorination treatment; (2)Prepare the metal precursor solution Dissolve lanthanum nitrate, nickel nitrate, tetrabutyl titanate or titanium tetrachloride, and cerium nitrate as metal salts in equal amounts of deionized water respectively to form a 0.1 - 0.5M metal precursor solution; (3)Prepare the composite metal catalyst Immerse the alumina support after fluorination treatment in step (1) into the metal precursor solution prepared in step (2) to carry out co - impregnation of lanthanum, nickel, titanium and cerium in the required proportions; (4)Drying and calcination Stir for 2 - 4 hours at room temperature to ensure the uniform distribution of metal ions on the surface of the support; after impregnation, let the mixture stand overnight; the next day, dry the impregnated support in an environment of 100 - 120 °C for 6 - 12 hours; then calcine in air at 500 - 600 °C for 4 - 6 hours; (5) Reduction calcination Subsequently, reduce in hydrogen at 300 - 400 °C for 2 - 4 hours to partially reduce the metal oxide into the form of active metal, and obtain the composite metal catalyst.

[0012] In the S3 - 2 hydroisomerization reaction, a fixed - bed reactor is used for the hydroisomerization reaction, and the specific steps are as follows: (1) Load the prepared composite metal catalyst into the reactor and distribute it evenly (2) Flush the reactor with nitrogen and preheat it to the starting reaction temperature of 100 - 150 °C, (3) Pump the hydro - biomass pyrolysis oil generated in step S2 - 2 into the reactor, introduce high - purity hydrogen, and control the hydrogen flow rate so that the molar ratio of hydrogen to hydro - biomass pyrolysis oil remains at 2:1 - 5:1; Control the reaction temperature at 250 - 350 °C; maintain the reaction pressure at 20 - 50 bar; control the stirring speed at 200 - 500 rpm; (4) Regularly take samples for analysis using gas chromatography to verify the degree of hydrogenation and isomerization; (5) After the reaction is completed, turn off the hydrogen supply, gradually reduce the reaction temperature to room temperature, use a condenser to cool the product outflow; slowly release the reactor pressure, collect the reaction product, and obtain isomerized biomass pyrolysis oil as aviation fuel through fractional distillation.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: By using a specific catalyst combination and multi - step catalytic reactions, the present invention realizes the conversion of biomass pyrolysis oil into aviation fuel, not only reducing the production cost of the catalyst, but also improving the catalytic efficiency of the catalyst during the reaction process, optimizing the performance of biomass pyrolysis oil in the hydrogenation and isomerization processes, increasing the reaction rate of the catalyst during the hydrogenation process, reducing the carbon deposition phenomenon on the catalyst surface, and improving properties such as the service life, stability, and anti - coking performance of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a process flow block diagram of synthesizing aviation fuel from biomass pyrolysis oil in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following further describes the present invention in conjunction with the drawings and embodiments.

[0016] The method for synthesizing aviation fuel based on biomass pyrolysis oil disclosed in the present invention comprises the steps of biomass liquefaction - hydrodeoxygenation reaction - hydroisomerization reaction, and specifically proceeds according to the following steps.

[0017] S1. Biomass liquefaction S1 - 1. Crush, dry, and screen the biomass raw materials to reduce the water content and improve the reaction efficiency.

[0018] S1 - 2. Add a solvent for pyrolysis; at the beginning of pyrolysis, the biomass raw materials are rapidly heated to 200 - 250 °C under a negative pressure (pressure 0.08 - 0.09 Mpa) environment within a time node of 10 - 20 minutes; the solvent is crude glycerol, a by - product of biodiesel, to ensure heat conduction and uniform reaction during the liquefaction process.

[0019] S1 - 3. Add an oxidation catalyst accounting for 0.1 - 0.5% of the mass of the biomass raw materials to promote the reaction and generate biomass pyrolysis oil with a low oxide content.

[0020] Biomass liquefaction is the process of converting solid biomass into liquid fuel. The core of the present invention is to break the polymer structure of biomass through solvent liquefaction under a specific catalyst to convert it into pyrolysis oil in liquid form. Biomass raw materials include wood chips, rice straw, waste agricultural residues, etc.

[0021] The oxidation catalyst in step S1 - 3 is a mixture of alkali metal hydroxides and transition metal oxides, such as KOH and MoO 3 mixture. The molar ratio of the alkali metal hydroxide to the transition metal oxide is 1:9 - 9:1. The alkali metal hydroxide promotes the degradation and alcoholysis reactions of biomass, and the transition metal oxide improves the deoxygenation efficiency of bio - oil. The negative pressure condition helps to produce low - oxygen pyrolysis oil, which is beneficial for post - treatment and refining.

[0022] S2. Hydrodeoxygenation S2 - 1. Catalyst preparation: Prepare a bimetallic catalyst of palladium and platinum supported on carbon.

[0023] S2 - 2. Hydrodeoxygenation reaction: The biomass pyrolysis oil generated in step S1 - 3 is subjected to hydrodeoxygenation treatment for 1 - 4 hours using the bimetallic catalyst at 125 - 250 °C. After treatment, the water phase of the biomass oil is removed by liquid separation to obtain hydrotreated biomass pyrolysis oil.

[0024] The raw materials of the bimetallic catalyst include activated carbon with a high specific surface area (Vulcan XC - 72) as the catalyst support, palladium chloride (PdCl 2 ) and chloroplatinic acid (H 2 PtCl 6), sodium borohydride or hydrogen (either one can be chosen) as a reducing agent, and deionized water; the molar ratio of palladium to platinum in the metal precursor solution ranges from 1:1 to 1:3. The synergistic effect between palladium (Pd) and platinum enhances the hydrogenation and deoxygenation activities of the catalyst while reducing the amount of precious metals used.

[0025] The preparation method of the bimetallic catalyst is as follows: (1)Activated carbon pretreatment Ultrasonically clean the activated carbon in deionized water for 20 - 30 minutes to remove impurities; dry it in an environment of 100 - 120 °C for 2 - 3 hours to ensure complete removal of moisture.

[0026] (2)Preparation of metal precursor solution Dissolve palladium chloride and chloroplatinic acid in deionized water respectively to prepare precursor solutions with a concentration of 0.1 - 0.5 M.

[0027] Mix the prepared precursor solutions of palladium and platinum evenly, where the molar ratio of palladium to platinum is 1:1 - 1:3, to obtain the metal precursor solution for later use.

[0028] (3)Preparation of the initial catalyst Add the activated carbon treated in step (1) to the metal precursor solution in step (2), stir and impregnate the solution at room temperature for 2 - 4 hours to ensure that the metal precursor is evenly adsorbed on the surface of the activated carbon, and let it stand overnight to further enhance the binding of the metal precursor to the carrier, obtaining the initial catalyst; (4)Drying and calcination The next day, dry the initial catalyst in an environment of 100 - 120 °C for 6 - 12 hours; calcine the dried initial catalyst at 200 - 300 °C for 2 hours to remove the organic part in the precursor and form oxides; immerse the initial catalyst in the NaBH 4 solution (0.05 - 0.1 M), stir for 1 - 2 hours until the metal oxides are completely reduced to the metal state.

[0029] (5)Reductive calcination Pass hydrogen into the reduction furnace, and reduce the initial catalyst in step (3) at 300 - 400 °C for 2 - 3 hours, so that the metal oxides are completely reduced to metals; then wash with deionized water and dry in an environment of 100 - 120 °C to obtain the bimetallic catalyst.

[0030] The hydrogenation equipment selects a continuous flow fixed - bed reactor, and the specific steps of the hydrodeoxygenation reaction are as follows: (1)Load the bimetallic catalyst into the reactor, ensure uniform distribution of the catalyst layer, and avoid blockage and pressure drop.

[0031] (2)Use nitrogen (N 2After flushing the reactor, remove the oxygen in the system to prevent oxidation. Preheat the reactor to 125 - 250 °C to shorten the heating-up time.

[0032] (3) The bio - pyrolysis oil generated in step S1 - 3 is injected into the reactor at a constant flow rate of 1 - 10 ton / h after removing moisture by slight heating (50 - 70 °C).

[0033] (4) Introduce high - purity hydrogen into the reactor, and control the hydrogen flow rate so that the molar ratio of hydrogen to bio - pyrolysis oil is 2:1 - 5:1; The reactor pressure is controlled at 20 - 100 bar; during the reaction, the stirring speed is maintained at 200 - 500 rpm to ensure sufficient contact between the bio - oil and the catalyst. The temperature during hydrogenation is maintained between 125 and 250 °C; the low - temperature range (125 - 180 °C) helps with preliminary hydrogenation and reduces the oxide content; the high - temperature range (180 - 250 °C) is used for further hydrogenation and deoxygenation. Ensure that the system pressure is stable at 20 to 100 bar to increase the solubility of hydrogen and the reaction rate; the hydrotreating time is 1 - 4 hours, depending on the raw material characteristics and the target conversion rate.

[0034] (5) After the reaction, turn off the hydrogen supply, gradually lower the reactor temperature to room temperature, slowly release the reactor pressure, and remove the aqueous phase by liquid separation from the treated bio - pyrolysis oil to obtain hydrogenated bio - pyrolysis oil.

[0035] S3. Hydroisomerization S3 - 1 Catalyst preparation: Prepare a composite metal catalyst composed of lanthanum, nickel, titanium, and cerium supported on alumina after fluorination treatment.

[0036] S3 - 2 Hydroisomerization reaction: Carry out a hydroisomerization reaction on the hydrogenated bio - pyrolysis oil generated in step S2 - 2 using the composite metal catalyst in an environment of 200 - 450 °C, collect the reactants, and obtain isomerized bio - pyrolysis oil as aviation fuel.

[0037] The preparation steps of the composite metal catalyst are as follows: (1) Fluorination treatment First, mix the high - specific - surface - area alumina (γ - Al 2 O 3 ) support with ammonium fluoride (NH 4 F) solution, and just complete the soaking. The concentration of ammonium fluoride is 0.1 - 1 M; under stirring conditions, the mixture reacts at room temperature for 2 - 4 hours; Then, filter the treated alumina and dry it at 100 - 120 °C for 6 - 12 hours; Finally, calcine it in air at 400 - 500 °C for 2 - 4 hours to complete the fluorination treatment.

[0038] (2) Preparation of metal precursor solution Take lanthanum nitrate (La(NO 3 ) 3 ), nickel nitrate (Ni(NO 3 ) 2 ), tetrabutyl titanate (Ti(OBu) 4 ), or titanium tetrachloride (TiCl 4 ) (either one can be chosen), and cerium nitrate (Ce(NO 3 ) 3 ), and dissolve them separately in equal amounts of deionized water to form metal precursor solutions with a concentration of 0.1 - 0.5 M respectively.

[0039] (3) Preparation of composite metal catalyst Immerse the fluorinated alumina support prepared in step (1) into the metal precursor solution prepared in step (2) to perform co - impregnation of lanthanum, nickel, titanium, and cerium in the required proportions. The total amount of the whole mixture is 100 parts, and the molar amount of each metal varies in the range of 5 - 35 parts.

[0040] (4) Drying and calcination Stir at room temperature for 2 - 4 hours to ensure that metal ions are evenly distributed on the surface of the support; after impregnation, let the mixture stand overnight; the next day, dry the impregnated support at 100 - 120 °C for 6 - 12 hours to remove the solvent; then calcine in air at 500 - 600 °C for 4 - 6 hours to decompose the metal salt and form metal oxides.

[0041] (5) Reduction calcination Subsequently, burn in a reduction furnace under a hydrogen atmosphere, reduce at 300 - 400 °C for 2 - 4 hours to partially reduce the metal oxides into the form of active metals. After slowly cooling to room temperature, the catalyst is completed and stored in a desiccator to obtain the composite metal catalyst.

[0042] In the hydroisomerization reaction, a fixed - bed reactor is used for the hydroisomerization reaction. This fixed - bed reactor is connected in series with the fixed - bed reactor in the hydrodeoxygenation process and is used independently. The specific steps of hydroisomerization are as follows.

[0043] (1) Load the prepared composite metal catalyst into the reactor, ensure that the catalyst is evenly distributed, and the packing density is appropriate to avoid problems of uneven flow and pressure drop.

[0044] (2) Use nitrogen (N 2 ) to flush the reactor to remove oxygen in the system and prevent the catalyst from being oxidized. Heat the reactor to the reaction starting temperature (100 - 150 °C) to ensure that the reaction system reaches a thermally stable state.

[0045] (3) Pump the hydrotreated biomass pyrolysis oil generated in step S2-2 into a reactor, introduce high-purity hydrogen, and control the hydrogen flow rate so that the molar ratio of hydrogen to hydrotreated biomass pyrolysis oil is maintained at 2:1 - 5:1; the hydrogen flow rate should be adjusted according to the reactor scale and the required conversion rate.

[0046] Control the reaction temperature at 250 - 350 °C. A lower temperature (250 - 300 °C) is used to promote the hydrogenation reaction, while a higher temperature (300 - 350 °C) helps with isomerization; maintain the reaction pressure at 20 - 50 bar to ensure that the solubility of hydrogen is high enough to promote the hydroisomerization reaction; use a distributor in the reactor to maintain the uniformity of the reaction fluid flowing through the catalyst bed; control the stirring speed at 200 - 500 rpm to ensure sufficient contact between the raw material and the catalyst.

[0047] (4) Regularly take samples for analysis using gas chromatography (GC) to verify the degree of hydrogenation and isomerization; according to the monitoring results, adjust the pressure to ensure the optimal degree of isomerization.

[0048] (5) After the reaction is completed, turn off the hydrogen supply, gradually lower the reaction temperature to room temperature, and use a condenser to cool the product stream; slowly release the reactor pressure, collect the reaction products, and obtain isomerized biomass pyrolysis oil as aviation fuel and non-isomerized hydrotreated biomass pyrolysis oil through fractional distillation.

[0049] In the composite metal catalyst, the main functions of each component are as follows: The alumina after fluorination treatment has strong acidity, which helps with the isomerization reaction. It is used in the isomerization reaction of straight-chain alkanes and can effectively increase the branched-chain structure. Lanthanum not only increases the oxygen vacancies to enhance the deoxidation ability but also prevents the agglomeration of metal particles, thereby improving the stability of the catalyst under high-temperature conditions and extending the catalyst life. Nickel is a hydrogenation catalyst. It acts as a hydrogenation active site in the catalyst, enabling the oxygen-containing compounds in the biomass pyrolysis oil to be hydrogenated and reduced. Moreover, nickel is cheaper than platinum and palladium, so using it as a catalyst helps reduce the overall cost. Titanium can work synergistically with other metal oxides to adjust the electron density, enhance the hydrogenation performance of the catalyst, and can also promote the dispersion of metal particles. When combined with lanthanum or cerium, it forms a strong supporting effect, which helps improve the thermal stability and anti-coking performance of the catalyst.

[0050] Cerium is an important redox regulator in the catalyst. Its oxide has good oxygen storage and release capabilities, which can reduce the carbon deposition phenomenon on the catalyst surface, thereby improving the stability and service life of the catalyst.

[0051] The combination of lanthanum and cerium helps to form a more stable mixture in the catalyst, enhancing the redox performance and anti-coking property; the combination of nickel and titanium can improve the hydrogenation reaction. The combination of these metals and the fluorinated alumina provides abundant active sites and a stable structure, while optimizing the hydrogenation, isomerization, and anti-carbon deposition properties, making it perform excellently in the hydroisomerization reaction of bio-oil.

[0052] Example Result 1: After pyrolysis of wood chips and crude glycerol for 20 minutes under a pressure of 0.09 Mpa and catalyzed by 0.1% KOH-MoO 3 (1:1), the resulting solution is hydrodeoxygenated under the catalysis of Pd-Pt (1:1) / activated carbon, and then hydroisomerized under the catalysis of La-Ni-Ti-Ce (25:25:25:25) / Al 2 O 3 -F to obtain sustainable aviation fuel. The indicators are as follows in the table and meet the ASTM7566 standard.

Claims

1. A method for synthesizing aviation fuel based on biomass pyrolysis oil, characterized in that , follow these steps: S1. Biomass liquefaction S1-1 crushing, drying and screening the biomass raw materials; S1-2 adding a solvent for pyrolysis; when pyrolysis begins, the biomass raw material is rapidly heated to 200-250°C under a negative pressure environment; S1-3 adding 0.1-0.5% of the mass of the biomass raw material into an oxidation catalyst to promote the reaction and generate biomass pyrolysis oil with low oxide content; S2, Hydrodeoxygenation S2-1 Catalyst preparation: Preparation of a palladium and platinum bimetallic catalyst supported on carbon; S2-2 Hydrodeoxygenation reaction: The biomass pyrolysis oil generated in step S1-3 is subjected to hydrodeoxygenation treatment using a bimetallic catalyst at 125-250°C for 1-4 hours, and the treated biomass oil is separated to remove the water phase to obtain hydrogenated biomass pyrolysis oil; S3, Hydroisomerization S3-1 Catalyst preparation: preparing a composite metal catalyst composed of lanthanum, nickel, titanium and cerium supported on fluorinated alumina; S3-2 Hydroisomerization reaction: using the composite metal catalyst to perform a hydrogenation isomerization reaction on the hydrogenated biomass pyrolysis oil generated in step S2-2 at 200-450°C, collecting the reactants, and obtaining the isomerized biomass pyrolysis oil as aviation fuel.

2. The method for synthesizing aviation fuel based on biomass pyrolysis oil according to claim 1, characterized in that: The solvent in step S1-2 is crude glycerol, a byproduct of biodiesel.

3. The method for synthesizing aviation fuel based on biomass pyrolysis oil according to claim 1, characterized in that: The oxidation catalyst in step S1-3 is a mixture of an alkali metal hydroxide and a transition metal oxide, wherein the molar ratio of the alkali metal hydroxide to the transition metal oxide is 1:9-9:

1.

4. The method for synthesizing aviation fuel based on biomass pyrolysis oil according to claim 1, characterized in that: In step S2-1, the raw materials of the bimetallic catalyst include activated carbon with a high specific surface area as a catalyst carrier, palladium chloride and chloroplatinic acid as a metal precursor solution, sodium borohydride or hydrogen as a reducing agent, and deionized water; The molar ratio of palladium to platinum in the metal precursor solution is in the range of 1:1-1:

3.

5. The method for synthesizing aviation fuel based on biomass pyrolysis oil according to claim 4, characterized in that: The preparation method of the bimetallic catalyst is as follows: (1) Activated carbon pretreatment Ultrasonic cleaning of activated carbon in deionized water for 20-30 minutes to remove impurities; drying at 100-120°C for 2-3 hours to remove moisture; (2) Preparation of metal precursor solution palladium chloride and chloroplatinic acid are dissolved in deionized water to prepare precursor solutions of desired concentrations; The prepared palladium and platinum precursor solutions are mixed evenly to obtain a metal precursor solution for standby use; (3) Preparation of initial catalyst Adding the activated carbon treated in step (1) to the metal precursor solution in step (2), stirring the solution at room temperature for 2-4 hours, and standing overnight to obtain an initial catalyst; (4) Drying and roasting On the second day, the initial catalyst is dried at 100-120°C for 6-12 hours; the dried initial catalyst is calcined at 200-300°C for 2 hours to remove the organic part in the precursor and form an oxide; the initial catalyst is immersed in a NaBH4 solution and stirred for 1-2 hours; (5) Reduction roasting Hydrogen is introduced into the reduction furnace to reduce the initial catalyst of step (3) at 300-400° C. for 2-3 hours; then the catalyst is washed with deionized water and dried at 100-120° C. to obtain a bimetallic catalyst.

6. The method for synthesizing aviation fuel based on biomass pyrolysis oil according to claim 1, characterized in that: Step S2-2 Hydrodeoxygenation reaction, the specific steps are as follows: (1) Loading the bimetallic catalyst into the reactor and distributing it evenly; (2) After flushing the reactor with nitrogen, preheat the reactor to 125-250°C; (3) After removing water from the biomass pyrolysis oil generated in step S1-3, it is injected into the reactor at a constant flow rate of 1-10 ton / h; (4) introducing high-purity hydrogen into the reactor and controlling the hydrogen flow rate so that the molar ratio of hydrogen to biomass pyrolysis oil is 2:1-5:1; The reactor pressure is controlled at 20-100 bar; during the reaction, the stirring speed is maintained at 200-500 rpm; during hydrogenation, the temperature in the reactor is maintained between 125-250°C; the hydrogenation treatment time is 1-4 hours; (5) The treated biomass pyrolysis oil is subjected to liquid separation to remove the water phase to obtain hydrogenated biomass pyrolysis oil.

7. The method for synthesizing aviation fuel based on biomass pyrolysis oil according to claim 1, characterized in that: In step S3-1, the preparation steps of the composite metal catalyst are as follows: (1) Fluoridation treatment First, an alumina carrier with a high specific surface area is mixed with an ammonium fluoride solution, wherein the concentration of the ammonium fluoride is 0.1-1M; the mixture is reacted at room temperature for 2-4 hours under stirring conditions; Then, the treated alumina is filtered and dried at 100-120°C for 6-12 hours; Finally, calcination is performed in air at 400-500°C for 2-4 hours to complete the fluorination treatment; (2) Preparation of metal precursor solution Dissolve metal salts of lanthanum nitrate, nickel nitrate, tetrabutyl titanate or titanium tetrachloride, and cerium nitrate in equal amounts of deionized water to form a 0.1-0.5 M metal precursor solution; (3) Preparation of composite metal catalysts The alumina support subjected to fluorination treatment in step (1) is immersed in the metal precursor solution prepared in step (2) so that lanthanum, nickel, titanium and cerium are co-impregnated in a desired proportion; (4) Drying and roasting Stir at room temperature for 2-4 hours to ensure that the metal ions are evenly distributed on the surface of the carrier; after impregnation, the mixture is left to stand overnight; the next day, the impregnated carrier is dried at 100-120°C for 6-12 hours; and then calcined in air at 500-600°C for 4-6 hours; (5) Reduction roasting Subsequently, the metal oxide is partially reduced to the form of active metal in hydrogen at 300-400° C. for 2-4 hours to prepare a composite metal catalyst.

8. The method for synthesizing aviation fuel based on biomass pyrolysis oil according to claim 1, characterized in that: In the S3-2 hydroisomerization reaction, a fixed bed reactor is used for the hydroisomerization reaction. The specific steps are as follows: (1) Load the prepared composite metal catalyst into the reactor and evenly distribute it (2) Flush the reactor with nitrogen and preheat to the reaction starting temperature of 100-150°C. (3) pumping the hydrogenated biomass pyrolysis oil generated in step S2-2 into the reactor, introducing high-purity hydrogen, and controlling the hydrogen flow rate to maintain a molar ratio of hydrogen to hydrogenated biomass pyrolysis oil in the range of 2:1 to 5:1; Control the reaction temperature at 250-350°C; maintain the reaction pressure at 20-50 bar; control the stirring speed at 200-500 rpm; (4) Regular sampling and analysis using gas chromatography to verify the extent of hydrogenation and isomerization; (5) After the reaction is completed, the hydrogen supply is turned off, the reaction temperature is gradually lowered to room temperature, and the product outflow is cooled using a condenser; the reactor pressure is slowly released, the reaction products are collected, and isomerized biomass pyrolysis oil as aviation fuel is obtained through fractionation.

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