Core-shell structured catalyst for preparing aviation kerosene from biomass, method for preparing aviation kerosene from biomass

Abstract

This invention provides a core-shell structured catalyst and method for biomass-to-aviation kerosene production, relating to the technical field of solid waste resource utilization. The core-shell structured catalyst of this invention comprises, from the inside out, an active core, a transition layer, and a functional shell. The active core includes a support and a Ru-Ni alloy supported on the support. The transition layer includes a nitrogen-doped carbon layer. The functional shell includes a composite molecular sieve formed from W2C and ZSM-5. This invention solves the technical problems of traditional catalysts, such as single function, low hydrodeoxygenation efficiency, low product selectivity, insufficient stability, and harsh reaction conditions. Compared with traditional biomass hydrocracking catalysts (single-metal catalysts), it improves biomass conversion rate and aviation kerosene fraction selectivity, extends catalyst life, and reduces production costs, meeting environmental protection and resource utilization requirements.

Description

Technical Field

[0001] This invention relates to the technical field of solid waste resource utilization, and in particular to a core-shell structured catalyst for biomass-to-aviation kerosene production and a method for biomass-to-aviation kerosene production. Background Technology

[0002] Aviation kerosene, as the core fuel for air transport, currently relies mainly on petroleum resources, facing the dual challenges of resource depletion and excessive carbon emissions. Biomass, as a renewable resource that can be converted into liquid fuel, has become a research hotspot for its catalytic production of aviation kerosene. Biomass catalytic conversion typically involves a three-step process: pretreatment, platform compound preparation, and hydrodeoxygenation / cracking isomerization. Catalyst performance is crucial in determining product yield and selectivity.

[0003] Currently, mainstream catalysts mainly suffer from the following technical defects: (1) Poor dispersion of active components. In traditional supported catalysts (such as Pt / Al2O3 and Ni / SiO2), active metals tend to agglomerate, resulting in a reduction of hydrogenation active sites. The hydrogenation deoxygenation efficiency of biomass macromolecules (such as lignin-derived phenols and cellulose-derived furans) is less than 60%; (2) Low product selectivity. Single-function catalysts cannot simultaneously achieve "CO bond breaking" and "carbon chain reconstruction". The C8-C content in the product is low. 16 Aviation kerosene fraction accounts for less than 45%, which easily generates excessive C1-C7 light hydrocarbons or C 17+ Heavy wax; (3) Insufficient catalyst stability, impurities in biomass raw materials (such as sulfur and chlorine) during the reaction process can easily lead to poisoning of active components, and the substrate is prone to sintering at high temperature (350℃-450℃), and the catalyst life is usually less than 500 hours; (4) Harsh reaction conditions, which need to be carried out under high pressure (5MPa-10MPa H2), making it difficult to meet the needs of low-cost industrial production.

[0004] Therefore, there is an urgent need to develop a catalyst that combines highly dispersed active sites, multifunctional synergistic effects, high stability, and adaptability to mild reaction conditions.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One of the objectives of this invention is to provide a core-shell structured catalyst for the preparation of aviation kerosene from biomass, which can solve the technical problems of traditional catalysts such as single function, low hydrodeoxygenation efficiency, low product selectivity, insufficient stability and harsh reaction conditions.

[0007] The second objective of this invention is to provide a method for preparing aviation kerosene from biomass, which can improve the biomass conversion rate and the aviation kerosene fraction (C8-C). 16The selectivity is improved, with high-value-added isoalkanes accounting for more than 60%. The reaction conditions are mild and it is suitable for a variety of agricultural and forestry wastes (straw, wood chips, fruit shells). The process has high versatility and is easy to scale up.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In the first aspect, a core-shell structured catalyst for biomass-to-aviation kerosene production comprises, from the inside out, an active core, a transition layer, and a functional shell. The active core includes a support and a Ru-Ni alloy supported on the support; The transition layer includes a nitrogen-doped carbon layer; The functional shell includes a composite molecular sieve formed from W2C and ZSM-5.

[0009] Furthermore, the Ru-Ni alloy contains 5wt%-8wt% Ru and 12wt%-15wt% Ni.

[0010] Furthermore, the carrier comprises a mesoporous ZrO2-TiO2 composite oxide; Preferably, the molar ratio of Zr to Ti in the mesoporous ZrO2-TiO2 composite oxide is 2-4:1.

[0011] Furthermore, the particle size of the active core is 50nm-80nm.

[0012] Furthermore, the nitrogen content in the nitrogen-doped carbon layer is 3wt%-5wt%.

[0013] Furthermore, the thickness of the nitrogen-doped carbon layer is 5nm-10nm.

[0014] Furthermore, the W2C content in the composite molecular sieve is 8wt%-12wt%.

[0015] Furthermore, the thickness of the functional shell is 20nm-30nm.

[0016] Secondly, a method for preparing aviation kerosene from biomass includes the following steps: Agricultural and forestry waste is pretreated to obtain pretreated slurry; A mixture of H2 and N2 gas is introduced, and the pretreated slurry is catalytically converted using any one of the core-shell structure catalysts described above. The products are then separated to obtain the aviation kerosene.

[0017] Furthermore, the mass ratio of the pretreated slurry to the core-shell structured catalyst is 9-11:1; Preferably, the temperature of the catalytic conversion is 320℃-360℃, and the pressure of the catalytic conversion is 2MPa-3MPa; Preferably, the liquid space velocity (LHSV) of the catalytic conversion is 1.0 h⁻¹. -1 -1.5h -1 The gas space velocity is 3000 h⁻¹. -1 -4000h -1 .

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: The core-shell structure catalyst for biomass-to-aviation kerosene provided by this invention, through the synergistic effect of the core and shell structure, provides a high-density hydrodeoxygenation active site for efficient CO bond breaking, while the functional shell precisely regulates the carbon chain distribution, and the transition layer prevents the loss of active components. This achieves a one-step completion of "hydrogenation-cracking-isomerization," solving the problem of single-function traditional catalysts. It can improve biomass conversion rate and aviation kerosene fraction selectivity. Compared with traditional biomass hydrocracking catalysts (single-metal catalysts), the core-shell structure catalyst of this invention not only improves biomass conversion rate and aviation kerosene fraction selectivity, but also extends catalyst life. At the same time, the reaction conditions are mild (reaction pressure is reduced from 5MPa-10MPa to 2MPa-3MPa, reducing investment in high-pressure equipment), catalyst life is extended, production costs are reduced, and it also meets environmental protection and resource utilization requirements.

[0019] The present invention provides a method for preparing aviation kerosene from biomass, using agricultural and forestry waste as raw materials, realizing the conversion of waste into energy. The integrated process steps avoid the separation of intermediate products and can increase the biomass conversion rate to 72.3%, producing aviation kerosene fractions (C8-C...). 16 The selectivity is increased to 48.5%, of which high-value-added isoalkanes account for more than 60%. The reaction conditions are mild and it is suitable for a variety of agricultural and forestry wastes (straw, wood chips, fruit shells). The process has high versatility and is easy to scale up. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] According to a first aspect of the present invention, a core-shell structured catalyst for the preparation of aviation kerosene from biomass is provided, comprising, from the inside out, an active core, a transition layer and a functional shell layer; The active core includes a support and a Ru-Ni alloy supported on the support; The transition layer includes a nitrogen-doped carbon layer; The functional shell consists of a composite molecular sieve formed from W2C and ZSM-5.

[0022] This invention's core-shell structure catalyst, through the synergistic effect of its core and shell structure, provides a high-density active site for hydrogenation and deoxygenation, efficiently breaking CO bonds. The functional shell precisely regulates the carbon chain distribution, and the transition layer prevents the loss of active components, achieving a one-step completion of "hydrogenation-cracking-isomerization." This solves the problem of single-function traditional catalysts, improving biomass conversion rate and aviation kerosene fraction selectivity. Compared to traditional biomass hydrocracking catalysts (single-metal catalysts), this invention's core-shell structure catalyst not only improves biomass conversion rate and aviation kerosene fraction selectivity but also extends catalyst life. Furthermore, it provides milder reaction conditions (reacting pressure reduced from 5MPa-10MPa to 2MPa-3MPa, reducing investment in high-pressure equipment), extending catalyst life, lowering production costs, and meeting environmental protection and resource utilization requirements.

[0023] In this invention, a bimetallic active core design is adopted, in which Ru and Ni form an alloy phase. Through the electron transfer effect (the d orbital electrons of Ru shift to Ni), the adsorption capacity for CO bonds is enhanced, and the hydrodeoxygenation efficiency can be improved by more than 30%.

[0024] In a preferred embodiment, the Ru content in the Ru-Ni alloy can be 5wt%-8wt%, for example, 5wt%, 6wt%, 7wt%, 8wt%, but is not limited thereto, and the Ni content can be 12wt%-15wt%, for example, 12wt%, 13wt%, 14wt%, 15wt%, but is not limited thereto.

[0025] In a preferred embodiment, the support includes, but is not limited to, mesoporous ZrO2-TiO2 composite oxides, which have excellent thermal stability (temperature resistance > 800°C); the molar ratio of Zr to Ti in the mesoporous ZrO2-TiO2 composite oxide can be 2-4:1, and typical but non-limiting molar ratios are, for example, 2:1, 3:1, and 4:1.

[0026] In a preferred embodiment, the particle size of the active core can be 50nm-80nm, with typical but non-limiting particle sizes such as 50nm, 60nm, 70nm, and 80nm.

[0027] The active core can be prepared by coprecipitation-hydrogen reduction method, the steps of which are as follows: Zirconium nitrate and tetrabutyl titanate are dissolved in an ethanol-citric acid mixture in proportion, ruthenium nitrate and nickel nitrate are added, the pH is adjusted to 8.5 to form a gel, dried at 120℃ for 4 hours, calcined at 550℃ for 3 hours, and then reduced at 350℃ in H2 atmosphere for 2 hours to obtain an active core with a particle size of 50nm-80nm.

[0028] In this invention, the nitrogen-doped carbon layer serves as a transition layer, which can suppress the interaction between the active core and the shell components and improve electronic conductivity.

[0029] In a preferred embodiment, the nitrogen content in the nitrogen-doped carbon layer can be 3wt%-5wt%, for example, 3wt%, 4wt%, or 5wt%, but is not limited thereto, which is more conducive to improving electronic conductivity.

[0030] In a preferred embodiment, the thickness of the nitrogen-doped carbon layer can be 5 nm to 10 nm, with typical but non-limiting thicknesses such as 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm.

[0031] Nitrogen-doped carbon layers can be prepared by chemical vapor deposition, with the following steps: the active core is placed in a quartz tube reactor, and a mixture of acetylene and ammonia gas (volume ratio of 4:1) is introduced. The mixture is reacted at 600℃ for 1.5 hours to form a nitrogen-doped carbon layer with a thickness of 5nm-10nm, thus obtaining the active core modified with a transition layer.

[0032] In this invention, the composite molecular sieve formed by W2C and ZSM-5 serves as a functional shell, enabling carbon chain cracking and isomerization, regulating the carbon number distribution of the products, and ensuring C8-C... 16 Fraction selectivity.

[0033] In a preferred embodiment, the W2C content in the composite molecular sieve can be 8wt%-12wt%, for example, 8wt%, 9wt%, 10wt%, 11wt%, or 12wt%, but is not limited thereto; the silicon-aluminum ratio of ZSM-5 can be 50:1.

[0034] In a preferred embodiment, the thickness of the functional shell can be 20nm-30nm, with typical but non-limiting thicknesses such as 20nm, 22nm, 24nm, 26nm, 28nm, and 30nm.

[0035] The functional shell can be prepared by in-situ crystallization, with the following steps: the active core modified by the transition layer is dispersed in a mixture of silica sol, aluminum source (aluminum isopropoxide), and template agent (tetrapropylammonium hydroxide), ammonium metatungstate is added, and the mixture is hydrothermally reacted at 180°C for 48 hours. Then, the template agent is removed by calcination at 500°C to form a functional shell with a thickness of 20nm-30nm, thus obtaining a core-shell structure catalyst.

[0036] A typical preparation method for a core-shell structured catalyst for biomass-to-aviation kerosene production includes the following steps: Preparation of active core: 10.2 g zirconium nitrate and 4.5 g tetrabutyl titanate were dissolved in 50 mL of ethanol-citric acid mixture (volume ratio 2:1), 1.8 g ruthenium nitrate and 5.6 g nickel nitrate were added, and the mixture was stirred for 30 minutes. The pH was adjusted to 8.5 with ammonia water to form a light green gel. The gel was dried in an oven at 120 °C for 4 hours to obtain a dry gel. The dry gel was placed in a muffle furnace and calcined at 550 °C for 3 hours (heating rate 5 °C / min). After cooling, it was transferred to a tube furnace and reduced at 350 °C in an H2 atmosphere (flow rate 50 mL / min) for 2 hours to obtain Ru-Ni / ZrO2-TiO2 active core. Transition layer modification: The active nucleus was placed in a quartz tube reactor, and a mixture of acetylene (20 mL / min) and ammonia (5 mL / min) gas was introduced. The temperature was raised to 600℃ and reacted for 1.5 hours. After natural cooling, the active nucleus with the transition layer modified was obtained. Preparation of functional shell: 5g of the transition layer modified active core was dispersed in 80mL of mixed solution (containing 20g of silica sol, 1.2g of aluminum isopropoxide, 5g of tetrapropylammonium hydroxide, and 1.5g of ammonium metatungstate), stirred evenly, and then transferred to a hydrothermal reactor. The reaction was carried out at 180℃ for 48 hours. After the reaction was completed, the solid was collected by filtration, washed with deionized water until neutral, dried at 110℃ for 12 hours, and calcined at 500℃ for 6 hours (heating rate 2℃ / min) to obtain the core-shell structured catalyst.

[0037] The core-shell structured catalyst of this invention appears as black spherical particles with a particle size of 100nm-150nm and a specific surface area of ​​850m². 2 / g-950m 2 / g, pore volume can be 0.6cm 3 / g-0.8cm 3 / g, with an average pore size of 2.5nm-3.5nm.

[0038] According to a second aspect of the present invention, a method for preparing aviation kerosene from biomass is provided, comprising the following steps: Agricultural and forestry waste is pretreated to obtain pretreated slurry; A mixture of H2 and N2 gas is introduced, and the pretreated slurry is catalytically converted using any of the core-shell structure catalysts described above. The products are then separated to obtain aviation kerosene.

[0039] This invention provides a biomass-to-aviation kerosene production method using agricultural and forestry waste as raw material, achieving the conversion of waste into energy. The integrated process steps avoid the separation of intermediate products and can increase the biomass conversion rate to 72.3%, producing aviation kerosene fractions (C8-C...). 16The selectivity is increased to 48.5%, of which high-value-added isoalkanes account for more than 60%. The reaction conditions are mild and it is suitable for a variety of agricultural and forestry wastes (straw, wood chips, fruit shells). The process has high versatility and is easy to scale up.

[0040] In this invention, agricultural and forestry waste (such as corn stalks) is crushed to a particle size of 1mm-3mm, and a 10% (w / w) formic acid-acetic acid mixture (volume ratio of 1:1) is added. The mixture is reacted at 160℃ and 2MPa for 2 hours to remove 50%-60% of the lignin from the raw material. Then, 0.5wt% zinc sulfate is added, and the mixture is reacted at 120℃ for 1 hour to promote the degradation of cellulose and hemicellulose into soluble sugars, thus obtaining the pretreated pulp.

[0041] It should be noted that during the catalytic conversion process, the active nuclei first convert the sugars and phenols in the pretreated slurry into C. 12 -C 20 Long-chain alcohols / esters, through the functional shell, are further converted into C8-C compounds via cracking and isomerization. 16 Isoalkanes.

[0042] In this invention, the mass ratio of the pretreated slurry to the core-shell structured catalyst can be 9-11:1, with typical but non-limiting mass ratios such as 9:1, 10:1, and 11:1.

[0043] In a preferred embodiment, the temperature of the catalytic conversion can be 320℃-360℃, for example, 320℃, 330℃, 340℃, 350℃, or 360℃, but is not limited thereto, and the pressure of the catalytic conversion can be 2MPa-3MPa, for example, 2MPa, 2.5MPa, or 3MPa, but is not limited thereto.

[0044] The temperature (320℃-360℃) and pressure (2MPa-3MPa) of the catalytic conversion are based on the reaction characteristics of biomass hydrogenation deoxygenation, carbon chain cracking and isomerization. Combined with the high activity advantage of the core-shell structure catalyst of this invention, it not only conforms to the laws of reaction thermodynamics and kinetics, but also takes into account efficiency, selectivity and industrial feasibility.

[0045] In a preferred embodiment, the liquid space velocity for catalytic conversion can be 1.0 h⁻¹. -1 -1.5h -1 For example, it can be 1.0h -1 1.1h -1 1.2h -1 1.3h -1 1.4h -1 1.5h -1 However, it is not limited to this; the gas space velocity can be 3000 h⁻¹. -1 -4000h-1 For example, it can be 3000h -1 3200h -1 3400h -1 3600h -1 3800h -1 4000h -1 However, it is not limited to this.

[0046] After condensation, the product can be successively subjected to atmospheric distillation (collecting the 150℃-280℃ fraction) and molecular sieve adsorption (removing water using 3A molecular sieve) to obtain aviation kerosene product, with the remaining heavy components (C... 17+ Then it can be recycled back to the reactor for secondary conversion.

[0047] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0048] Example 1 A core-shell structured catalyst for biomass-to-aviation kerosene production comprises, from the inside out, an active core, a transition layer, and a functional shell. The active core consists of a support and a Ru-Ni alloy supported on the support, with a particle size of 65 nm. The Ru-Ni alloy contains 5 wt% Ru and 15 wt% Ni. The support is a mesoporous ZrO2-TiO2 composite oxide, wherein the molar ratio of Zr to Ti is 3:1; The transition layer is a nitrogen-doped carbon layer with a thickness of 7 nm; The nitrogen content in the nitrogen-doped carbon layer is 4 wt%; The functional shell is a composite molecular sieve formed by W2C and ZSM-5, with a thickness of 25 nm; The functional shell contains 10 wt% W2C, and the silicon-to-aluminum ratio of ZSM-5 is 50:1.

[0049] Example 2 The only difference between this embodiment and Embodiment 1 is that the Ru content in the Ru-Ni alloy is 6 wt% and the Ni content is 14 wt%. Everything else is the same as in Example 1.

[0050] Example 3 The only difference between this embodiment and Embodiment 1 is that the Ru content in the Ru-Ni alloy is 7wt% and the Ni content is 13wt%. Everything else is the same as in Example 1.

[0051] Example 4 The only difference between this embodiment and Embodiment 1 is that the Ru content in the Ru-Ni alloy is 8 wt% and the Ni content is 12 wt%. Everything else is the same as in Example 1.

[0052] Example 5 The only difference between this embodiment and Embodiment 1 is that the nitrogen content in the nitrogen-doped carbon layer is 3 wt%. Everything else is the same as in Example 1.

[0053] Example 6 The only difference between this embodiment and Embodiment 1 is that the nitrogen content in the nitrogen-doped carbon layer is 5 wt%. Everything else is the same as in Example 1.

[0054] Example 7 The only difference between this embodiment and Embodiment 1 is that the W2C content in the functional shell is 8 wt%. Everything else is the same as in Example 1.

[0055] Example 8 The only difference between this embodiment and Embodiment 1 is that the W2C content in the functional shell is 12 wt%. Everything else is the same as in Example 1.

[0056] Comparative Example 1 The only difference between this comparative example and Example 1 is that the active core consists of a support and Ru loaded on the support, and does not contain Ni; Everything else is the same as in Example 1.

[0057] Compared with Example 1, the drawback of this comparative example is that the pure Ru active core leads to a significant decrease in the hydrodeoxygenation activity of the catalyst, an imbalance in product selectivity, increased aggregation and poisoning of active components, and a weakened bonding force with the support interface.

[0058] The Ru-Ni alloy exhibits an electronic synergistic effect, while the active core of pure Ru lacks this synergistic effect. This reduces the efficiency of CO bond breaking in biomass, resulting in incomplete conversion of sugars and aldehydes in biomass and a decrease in conversion rate.

[0059] Pure Ru active nuclei exhibit high adsorption selectivity for C-C bonds, readily adsorbing C... 12 -C 20 Long-chain alcohols / esters undergo excessive cracking into light hydrocarbons, while heavy waxes (C...) are also affected by the lack of Ni regulation. 17+ The increased production of aviation kerosene fractions (C8-C) ultimately leads to an increase in the amount of these fractions. 16 Selectivity is reduced.

[0060] In the active core of pure Ru, Ru atoms are prone to surface diffusion at a reaction temperature of 340℃, forming agglomerated particles and reducing the exposure of active sites. Ni can preferentially adsorb sulfur and chlorine impurities in the feedstock, protecting the Ru active sites; while pure Ru is in direct contact with impurities, increasing the poisoning rate and leading to a shortened catalyst lifetime.

[0061] Comparative Example 2 The only difference between this comparative example and Example 1 is that the active core consists of a support and Ni loaded on the support, and does not contain Ru; Everything else is the same as in Example 1.

[0062] Compared with Example 1, the drawback of this comparative example is that the hydrodeoxygenation activity is severely insufficient.

[0063] Ni's hydrogenation activity stems from its ability to dissociate and adsorb H2, but Ni's d-band center (-1.8 eV) is lower than that of Ru (-1.5 eV) and Ru-Ni alloys (-1.2 eV), resulting in an adsorption activation energy as high as 3.2 eV for the strongly polar CO bonds in biomass (compared to only 2.1 eV for Ru-Ni alloys), leading to a decrease in CO bond breaking efficiency. Furthermore, the phenolic hydroxyl groups of phenolic compounds in biomass cannot be effectively removed, and the resulting intermediate products easily polymerize on the catalyst surface, ultimately reducing the biomass conversion rate.

[0064] The product lacks the ability to regulate the carbon chain. The hydrogen transfer rate of the pure Ni active core is only 1 / 3 that of the Ru-Ni alloy. A large amount of incompletely hydrogenated long-chain olefins are prone to cyclization reactions to form aromatics. At the same time, Ni has weak cracking activity and cannot control the carbon chain. 20+ Heavy substances are effectively broken down into C8-C. 16 The distillate fractions lead to a decrease in the selectivity of aviation kerosene.

[0065] High-temperature sintering exacerbates carbon deposition. Although Ni's melting point (1455℃) is higher than Ru's, at a reaction temperature of 340℃, pure Ni particles have a higher surface energy (1.8 J / m²). 2 The Ru-Ni alloy has a strength of 1.2 J / m. 2 Ni is prone to particle fusion, reducing the exposure of active sites. Simultaneously, Ni has high acid site strength, readily catalyzing the polymerization and coking of olefins in biomass, resulting in a high coking rate and shortening catalyst life.

[0066] Comparative Example 3 The only difference between this comparative example and Example 1 is that there is no transition layer in the catalyst; Everything else is the same as in Example 1.

[0067] Compared with Example 1, the shortcomings of this comparative example are that the interdiffusion of components between the active core and the functional shell is intensified, the hydrogenation active sites of the active core are lost, the CO bond breaking efficiency decreases, the shape-selective catalytic ability of the functional shell is ineffective, and the C8-C bond cannot be precisely controlled. 16 The fractions; at the same time, the interfacial electronic synergistic effect is lost, the catalyst interfacial stress cracks, and the carbon deposition rate increases.

[0068] Comparative Example 4 The only difference between this comparative example and Example 1 is that the transition layer is a carbon layer, rather than a nitrogen-doped carbon layer; Everything else is the same as in Example 1.

[0069] Compared with Example 1, the shortcomings of this comparative example are that the interfacial electronic synergistic effect is significantly weakened, the migration inhibition of active components is insufficient, and chemical anchoring sites cannot be formed by physical isolation alone; at the same time, the anti-carbon deposition performance is poor and the catalyst interfacial binding force is reduced.

[0070] Comparative Example 5 The only difference between this comparative example and Example 1 is that the catalyst has no functional shell. Everything else is the same as in Example 1.

[0071] Compared with Example 1, the shortcomings of this comparative example are that the carbon chain regulation function is lost, the target aviation kerosene fraction is reduced, the active nucleus's resistance to poisoning and carbon deposition is drastically reduced, the mass transfer efficiency is low, the reaction rate is greatly reduced, and the biomass cannot be completely converted.

[0072] Comparative Example 6 The only difference between this comparative example and Example 1 is that the functional shell is a ZSM-5 molecular sieve, which does not contain W2C. Everything else is the same as in Example 1.

[0073] Compared with Example 1, the shortcomings of this comparative example are that the long-chain product is lost, the macromolecule cannot be converted into the target fraction, the shape-selective catalytic function fails, the product distribution is out of control, the active core load increases dramatically, the carbon deposition rate increases, and the lifespan is shortened.

[0074] Test case The catalysts of Examples 1-8 and Comparative Examples 1-6 were subjected to biomass catalytic conversion experiments to obtain the corresponding biomass conversion rates and aviation kerosene fractions (C8-C6). 16 Selectivity and catalyst lifetime were evaluated, and the results are shown in Table 1.

[0075] The test method is as follows: Pretreatment: Crush corn stalks to 2mm, take 50g and add 100mL of formic acid-acetic acid mixture (volume ratio 1:1), put it into a high-pressure reactor, react at 160℃ and 2MPa for 2 hours, filter to obtain filter residue; add 50mL of aqueous solution containing 0.5wt% zinc sulfate to the filter residue, react at 120℃ for 1 hour, filter to obtain pretreated slurry; Catalytic reaction: 5g of catalyst was loaded into a fixed-bed reactor, and a H2 / N2 mixed gas (volume ratio 3:1) was introduced. The temperature was raised to 340℃, and the pressure was stabilized at 2.5MPa. The pretreated slurry was then subjected to a 1.2h reaction. -1 The liquid hourly space velocity (LHSV) is pumped into the reactor, and the gas hourly space velocity (GEV) is 3500 h⁻¹. -1 The reaction lasted for 1000 hours; Product analysis: The composition of the products was analyzed by gas chromatography-mass spectrometry (GC-MS, Agilent 7890A-5975C), and the results are shown in Table 1.

[0076] As shown in Table 1, the present invention is derived from Ru Ni bimetallic alloy active core, nitrogen-doped carbon transition layer, W2C ZSM The three-level core-shell structure catalyst composed of five composite molecular sieve functional shells achieves synergistic enhancement of hydrodeoxygenation, selective cracking, directional isomerization and stable mass transfer. Compared with traditional catalysts and comparative examples that are single-metallic, without transition layers, without functional shells, and without W2C, the core-shell structure catalyst of this invention can improve biomass conversion rate, improve the selectivity of aviation kerosene fractions, and extend catalyst life.

[0077] Table 1

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A core-shell structured catalyst for biomass-to-aviation kerosene production, characterized in that, From the inside out, it consists of an active core, a transition layer, and a functional shell. The active core includes a support and a Ru-Ni alloy supported on the support; The transition layer includes a nitrogen-doped carbon layer; The functional shell includes a composite molecular sieve formed from W2C and ZSM-5.

2. The core-shell structured catalyst according to claim 1, characterized in that, The Ru-Ni alloy contains 5wt%-8wt% Ru and 12wt%-15wt% Ni.

3. The core-shell structured catalyst according to claim 2, characterized in that, The carrier comprises a mesoporous ZrO2-TiO2 composite oxide; Preferably, the molar ratio of Zr to Ti in the mesoporous ZrO2-TiO2 composite oxide is 2-4:

1.

4. The core-shell structured catalyst according to any one of claims 1-3, characterized in that, The particle size of the active core is 50nm-80nm.

5. The core-shell structured catalyst according to claim 1, characterized in that, The nitrogen content in the nitrogen-doped carbon layer is 3wt%-5wt%.

6. The core-shell structured catalyst according to claim 5, characterized in that, The thickness of the nitrogen-doped carbon layer is 5nm-10nm.

7. The core-shell structured catalyst according to claim 1, characterized in that, The W2C content in the composite molecular sieve is 8wt%-12wt%.

8. The core-shell structured catalyst according to claim 7, characterized in that, The thickness of the functional shell is 20nm-30nm.

9. A method for preparing aviation kerosene from biomass, characterized in that, Includes the following steps: Agricultural and forestry waste is pretreated to obtain pretreated slurry; A mixture of H2 and N2 gas is introduced, and the pretreated slurry is catalytically converted using the core-shell structure catalyst according to any one of claims 1-8. The products are separated to obtain the aviation kerosene.

10. The method according to claim 9, characterized in that, The mass ratio of the pretreated slurry to the core-shell structured catalyst is 9-11:1; Preferably, the temperature of the catalytic conversion is 320℃-360℃, and the pressure of the catalytic conversion is 2MPa-3MPa; Preferably, the liquid space velocity (LHSV) of the catalytic conversion is 1.0 h⁻¹. -1 -1.5h -1 The gas space velocity is 3000 h⁻¹. -1 -4000h -1 .

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