Preparation method of a multi-stage hole composite molecular sieve catalyst for catalytic hydrogenation and method for preparing bio-jet fuel by hydrogenation of microalgae oil

Abstract

The application discloses a preparation method of a multi-stage hole composite molecular sieve catalyst for catalytic hydrogenation and a method for preparing bio-jet fuel by hydrogenating microalgae oil, and belongs to the technical field of preparing bio-jet fuel from microalgae oil. The multi-stage hole composite molecular sieve catalyst comprises a composite carrier and an active metal component loaded on the composite carrier. The preparation of the composite carrier in the catalyst is based on an in-situ symbiotic composite method, the combination of the treatment of SAPO-11, a prepolymer and an additive in a molecular sieve is used to realize uniform transition of the pore and improve the interface bonding force, the service life and the catalytic effect of the catalyst are improved, the content of isomerization products in the bio-jet fuel is improved, and the freezing point reaches the standard.

Description

Technical Field

[0001] This application relates to a method for preparing a hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation and a method for preparing bio-jet fuel by hydrogenation of microalgae oil, belonging to the field of bio-jet fuel preparation technology from microalgae oil. Background Technology

[0002] Microalgal oil is an oil extracted from microalgal cells. Its oil content is significantly higher than that of terrestrial plants such as soybeans and palms, making it a highly promising new oil resource. This resource can be cultivated using unconventional conditions such as non-arable land, wastewater, and seawater, without competing with food crops for land or water for agriculture. Furthermore, it can absorb carbon dioxide during its growth, making it a green and environmentally friendly biomass raw material.

[0003] Bio-jet fuel is aviation fuel prepared from renewable resources through chemical or biological processes. Currently, its raw materials are mostly concentrated in terrestrial plant oils such as soybean oil and palm oil. The core problem lies in competing with food crops for land and agriculture for water, making it difficult to overcome the bottleneck of raw material supply. Microalgae oil, with its advantages of short growth cycle and strong environmental adaptability, can be cultivated in environments such as saline-alkali land, industrial wastewater, and seawater, becoming a potential raw material to solve the above-mentioned bottlenecks.

[0004] However, microalgal oil has a complex molecular structure, containing a large number of oxygen-containing groups and unsaturated bonds. The current basic technology for producing bio-jet fuel from microalgal oil is to use metal-supported catalysts for catalysis, such as patents CN109364982B, CN109868152B, CN109603908B, and CN103977796B. However, although this technology can achieve a high alkane yield, it also has the problems of few isomers and difficulty in achieving the standard freezing point.

[0005] To address these issues, current research focuses on highly efficient and stable bifunctional catalysts. For example, US12344804B2 uses the noble metal Pt / Pd, US11858872B2 employs a four-step process, and US-20240165589-A1 utilizes the noble metals Pd / C, Ru / WZr, and composite metal oxides through a two-step catalytic reaction. However, these catalysts often employ noble metals or involve complex processes, increasing production costs and hindering industrial-scale application.

[0006] The applicant found that most current research focuses on single molecular sieve supports, lacking studies on the synergistic effects of different molecular sieves. Microalgal oil contains a large number of oxygen-containing groups and requires a two-step reaction of hydrodeoxygenation and hydroisomerization to be converted into bio-jet fuel. Existing processes generally use two-stage reactors for the reaction. SAPO-11 molecular sieves exhibit excellent isomerization performance due to their unique acidic properties and one-dimensional elliptical ten-membered ring channel structure, making them particularly suitable for producing jet fuel components with low freezing points. β-molecular sieves have a three-dimensional twelve-membered ring channel structure, which can improve the diffusion and transport efficiency of macromolecular reactants; they also have strong Brønsted acidic centers, making them particularly suitable for the hydrodeoxygenation process of macromolecular oils. If SAPO-11 and β-molecular sieves could be combined, it is hoped that synergistic hydrodeoxygenation-hydroisomerization could be achieved. However, when using the physical mixing method, the synthesized SAPO-11 and β-molecular sieves need to be physically mixed. This operation is simple, but the interfacial interaction between the two molecular sieves is weak, which limits mass transfer and makes it difficult to realize their synergistic effect. In contrast, the in-situ co-existing composite method can construct a core-shell structure, achieving tight coupling between molecular sieves. Based on the characteristics of SAPO-11 and β-zeolites, a reasonable configuration is to use SAPO-11 as the core and β-zeolites as the shell. This creates a confinement effect through the hierarchical pore distribution of the two molecular sieves. Large molecule oils first undergo hydrogenation and deoxygenation in the pores of the outer β-zeolite, and the resulting small molecule straight-chain alkanes are then "confined" within the composite pore system and diffuse to the internal SAPO-11 active sites for hydrogenation isomerization. This design not only achieves efficient isomerization and moderate cracking of alkanes but also forms a directional "deoxygenation-isomerization" tandem pathway, thus providing a new approach for developing low-cost, easy-to-operate, and industrially suitable composite molecular sieve catalysts.

[0007] However, the applicant discovered the following problems with this method: 1) β-zeolites form shells and grow homogeneously at the same time, rather than forming directional heterogeneous composite structures; 2) The molecular sieve interface between β molecular sieve and SAPO-11 molecular sieve is weak and there is a clear interface boundary, which makes it easy for the core layer to be removed during use, making it difficult to use in the production of bio-jet fuel for a long time. 3) The pore structure of β-zeolite and SAPO-11 zeolite is very different, making it difficult to regulate the overall distribution of acid centers through uniform transition of pores. Therefore, the catalytic effect on biofuel production still needs to be improved.

[0008] Therefore, there is currently a lack of a heterogeneous composite molecular sieve with good structure, no obvious interface boundaries, and good catalytic effect, as well as a method for using such a molecular sieve to catalyze the hydrogenation of microalgae oil to prepare bio-jet fuel. Summary of the Invention

[0009] To address the aforementioned issues, a method for preparing a hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation is provided. This method is based on an in-situ symbiotic composite method. By treating SAPO-11 and combining prepolymers and molecular sieve additives, a uniform transition of pores is achieved, and the interfacial bonding force is improved. This enhances the service life and catalytic effect of the hierarchical porous composite molecular sieve catalyst, thereby increasing the content of isomerization products in bio-jet fuel and ensuring that the freezing point meets the standard.

[0010] According to one aspect of this application, a method for preparing a hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation is provided, comprising the following steps: (1) Using aluminum, phosphorus, silicon and water as reactants in a molar ratio of 1:(0.8-1.0):(0.1-0.6):(40-60), where aluminum source is calculated as Al2O3, phosphorus source as P2O5 and silicon source as SiO2, after adjusting the pH, microporous molecular sieve template agent and polyethyleneimine are added, and after aging and crystallization, intermediate A is obtained; (2) Intermediate A is treated sequentially with NH4F solution and high-temperature steam, then immersed in a solution containing the first active metal component, aged, dried and calcined to obtain intermediate B. The mass of the first active metal component is 10%-25wt% of the total mass of intermediate A, and the first active metal component contains at least nickel. (3) Intermediate B is modified with an aminosilane coupling agent, and then added to the β molecular sieve precursor solution. It is crystallized at 80-100℃ for 6-12h, and then heated to 120-150℃ for 24-48h to obtain intermediate C. The β molecular sieve precursor solution contains 5%-15wt% acrylamide in the total weight of the β molecular sieve precursor solution. (4) Place intermediate C in a prepolymer solution, impregnate under pressure, stir and react at 65-75°C for at least 4 hours, filter and calcine to obtain intermediate D, wherein the reacting monomers in the prepolymer solution include at least unsaturated monomers containing epoxy groups. (5) The intermediate D is immersed in a solution containing the second active metal component, aged, dried, roasted and reduced to obtain the intermediate D. The mass of the second active metal component is 10%-25wt% of the total mass of the intermediate D, and the second active metal component contains at least cobalt.

[0011] The multi-level porous composite molecular sieve catalyst for catalytic hydrogenation in this application contains micropores, mesopores, and macropores. It is a core-shell structure multi-level porous composite molecular sieve. Through the spatial confinement of the core-shell structure, the reactants are forced to proceed along a predetermined path of "deoxygenation first, then isomerization", which reduces the disordered cracking or side reactions of intermediate products. It can improve the selectivity of isomer products in the preparation of bio-jet fuel from microalgae oil, lower the freezing point of bio-jet fuel, and improve the quality of bio-jet fuel.

[0012] The intermediate A synthesized in step (1) is a hierarchical porous SAPO-11 molecular sieve. The addition of polyethyleneimine allows intermediate A to contain polyethyleneimine components, which can form a macroporous channel structure during subsequent calcination. The size of this channel structure is larger than the micropores of SAPO-11 and the micropores and mesopores (acrylamide formation) of β molecular sieve, so that the micropores and mesopores of the catalyst can be uniformly transitioned to macropores, thereby improving the mass transfer efficiency, service life and catalytic effect of the catalyst, so as to increase the content of isomerization products and reduce the freezing point of the products.

[0013] Step (2) sequentially treats intermediate A with NH4F solution and high-temperature steam, which can regulate the surface charge, number of surface sites, and lattice matching degree of intermediate A, significantly reducing the activation energy barrier for β-zeolite crystal nucleus formation. This allows the β-zeolite precursor liquid to achieve directional growth on the surface of intermediate A under the influence of electrostatic adsorption, surface site induction, and lattice matching degree, thereby forming a directional heterogeneous composite structure between SAPO-11 and β-zeolite and initially eliminating the interface boundary. Furthermore, crystallization at 80-100℃ can increase the number of micro-crystal nuclei formed in intermediate A, and crystallization at 120-150℃ can achieve rapid growth of crystal nuclei along the lowest energy crystal direction, achieving directional arrangement. The two-step crystallization operation can avoid the disordered crystal growth caused by high-temperature rapid crystallization and significantly improve the coverage and orientation degree of β-zeolite on the SAPO-11 surface.

[0014] In step (2), the first active metal component was loaded onto SAPO-11 intermediate A and calcined. This allows the straight-chain alkane to instantly generate a short-lived olefin intermediate when isomerized at the acidic site of SAPO-11. The metal loaded in the core can immediately and in situ hydrogenate and saturate it, promoting the isomerization reaction to proceed rapidly in the forward direction and preventing the olefin intermediate from polymerizing and coking.

[0015] Step (3) involves modifying intermediate B with an aminosilane coupling agent. After the addition of the prepolymer, the amino groups on the surface of intermediate B can undergo ring-opening reactions with the epoxy groups in the prepolymer, achieving chemical bonding between intermediate B and the prepolymer. This enhances the interfacial bonding force with the β-zeolite through the prepolymer, eliminates the interfacial boundary, and avoids the removal of the shell. On the other hand, the β-zeolite precursor solution contains 5%-15 wt% acrylamide, and the amino groups in the acrylamide can also connect with the epoxy groups in the prepolymer. Therefore, the above treatment can enhance the correlation between SAPO-11 and the β-zeolite, thereby improving the crushing strength of the catalyst and increasing its service life.

[0016] In addition, acrylamide in the β-zeolite precursor solution also has the following functions: First, in alkaline synthesis gels, acrylamide monomers can act as gel stabilizers, increasing the viscosity of the gel, improving its uniformity and stability, and facilitating the formation of a more uniform nucleation environment; Second, during the heating crystallization process, acrylamide or its oligomers can act as space fillers. Although they do not possess the strong structure-directing properties of classic organic amines, they can physically confine the local growth environment of the zeolite crystals, acting as "soft templates" to form new microporous or mesoporous structures; Third, acrylamide molecules or their polymer chains can act as morphology regulators, adsorbing on specific crystal faces of the zeolite crystals, changing the growth rate of different crystal faces, thereby effectively controlling the final morphology of the crystals and reducing the crystal size. This helps to synthesize nanoscale zeolites, obtaining zeolites with shorter channels and larger specific surface areas, significantly improving mass transfer efficiency, and exhibiting excellent performance in catalytic reactions.

[0017] In step (4), the prepolymer solution is pressurized and impregnated with intermediate C. Firstly, this allows the prepolymer solution to penetrate to the interface between SAPO-11 molecular sieve and β molecular sieve. The epoxy groups in the prepolymer can undergo ring-opening reactions with the amino silane coupling agent and the amino group of acrylamide. Furthermore, the acrylamide can continue to polymerize with the prepolymer at 65-75℃ to form a polymer, further improving the connectivity between the prepolymer and the shell. Thus, the chemical connection between the two molecular sieves is achieved through the prepolymer as a medium, eliminating the interfacial effect. Secondly, the prepolymer can form a cross-linked network structure in intermediate C under the reaction in step (4), which is then burned off during the subsequent calcination. This can regulate the overall pore matching degree of the catalyst, thereby improving the catalytic effect of the catalyst.

[0018] After intermediate D is prepared, it is loaded with a second active metal component. The metal in the core is physically isolated by a dense β-zeolite shell, making it almost impossible for macromolecular microalgae oil to directly contact them. By loading a highly active hydrodeoxygenating metal on the outermost layer, it is ensured that macromolecules acquire sufficient hydrogenation activity in the initial stage of entering the pores. The active metal and the strong Brønsted acidic centers of the outer β-zeolite synergistically catalyze, significantly improving the deoxygenation efficiency and depth.

[0019] Optionally, the first active metal component may further include at least one of tungsten and niobium.

[0020] Optionally, the second active metal component further includes at least one of nickel and molybdenum.

[0021] The two active metal components used in the catalyst of this application are non-precious metal catalysts, which reduce the cost by 40%-90% compared with precious metal catalysts, making them more suitable for industrial application.

[0022] Optionally, after intermediate A is impregnated in a solution containing the first active metal component, it is dried at a temperature of 80-120°C for 10-12 hours and calcined at a temperature of 450-550°C for 2-6 hours.

[0023] Optionally, after intermediate D is impregnated in a solution containing a second active metal component, it is dried at a temperature of 80-120°C for 10-12 hours, calcined at a temperature of 450-550°C for 2-6 hours, and reduced at a temperature of 450-550°C for 2-6 hours.

[0024] Optionally, the specific operation of modifying intermediate B with an aminosilane coupling agent in step (3) is as follows: Intermediate B is placed in a 0.5%-3% aminosilane coupling agent solution, sonicated at 50-60℃ for 15-30 minutes, filtered, and dried to obtain the final product.

[0025] Optionally, the aminosilane coupling agent includes at least one of N-aminoethyl-3-aminopropyltriethoxysilane, 3-aminopropyldimethoxymethylsilane, and 3-aminopropyltriethoxysilane.

[0026] Optionally, the molar ratio of the microporous molecular sieve template agent to the aluminum source in step (1) is (1.0-2.5):1, and the aluminum source is calculated as Al2O3; The molecular weight of polyethyleneimine is 2000, and the mass of polyethyleneimine accounts for 50 wt% of the aluminum source.

[0027] The amounts of the aforementioned microporous molecular sieve template agent and polyethyleneimine can achieve the formation of micropores and macropores in SAPO-11. Furthermore, by adjusting the amount of polyethyleneimine, the pore structure of SAPO-11 can be adjusted, resulting in pores with a uniform transition between micropores, mesopores, and macropores.

[0028] Optionally, the microporous molecular sieve template agent includes one of di-n-propylamine, diisopropylamine, and diethylamine.

[0029] Optionally, the aluminum source in step (1) is one of boehmite, aluminum sulfate, sodium aluminate, and aluminum hydroxide sol; the silicon source is one of silica sol, water glass, and tetraethyl orthosilicate; and the phosphorus source is one of phosphoric acid and ammonium dihydrogen phosphate.

[0030] Optionally, in step (2), the concentration of the NH4F solution is 0.1-0.3 mol / L, the treatment temperature is 60-70℃, and the treatment time is 1-2 h.

[0031] The concentration of the NH4F solution and the parameter settings for the treatment are, firstly, to selectively remove unstable non-framework aluminum from intermediate A, stabilize the framework structure, open blocked micropores and mesopores, increase specific surface area and pore volume, reduce the starting point of framework collapse under hydrothermal conditions, make the molecular sieve more stable, and make the acid centers more evenly distributed; secondly, to perform framework dealuminization and silicon replenishment, create a silicon-rich layer, increase the framework silicon-aluminum ratio, enhance hydrophobicity and catalytic stability, make it more stable in reactions involving water, and improve its resistance to carbon deposition.

[0032] Optionally, the temperature of the high-temperature steam in step (2) is 440-500℃, and the treatment time is 4-6h.

[0033] The high-temperature steam treatment temperature and time can mildly dealudealate and surface hydroxylate intermediate A, thereby regulating its surface charge and reactivity to promote the directional growth of β molecular sieves on the SAPO-11 surface and obtain a directional heterogeneous composite structure.

[0034] Optionally, the β-zeolite precursor liquid in step (3) includes a silicon source, an aluminum source, a template agent and water, and the molar ratio of the silicon source, aluminum source, template agent and water is 1:(0.01-0.05):(0.2-0.6):(15-40), wherein the aluminum source is calculated as Al2O3 and the silicon source is calculated as SiO2.

[0035] The above dosage ensures the directional growth of β-zeolite on SAPO-11, resulting in a shell with high crystallinity and pore structure, thereby improving the catalytic effect.

[0036] Optionally, the silicon source of the β-molecular sieve precursor solution includes silica sol and water glass, and the aluminum source includes sodium aluminate.

[0037] Optionally, the template agent for the β-zeolite precursor solution includes tetraethylammonium hydroxide and tetraethylammonium bromide.

[0038] Optionally, the epoxy-containing unsaturated monomer is selected from at least one of glycidyl methacrylate and allyl glycidyl ether.

[0039] Optionally, the prepolymer solution is obtained by polymerizing acrylic acid and an unsaturated monomer containing epoxy groups, and the preparation method of the prepolymer solution is as follows: The unsaturated monomer containing epoxy groups and the acrylic acid are added to a solvent and polymerized for 1-2 hours under the action of an initiator to obtain the prepolymer solution.

[0040] If the prepolymer is obtained by polymerization of pure unsaturated monomers containing epoxy groups, it will have a large number of epoxy groups, resulting in more reaction sites with SAPO-11 and β-zeolites. However, due to steric hindrance, the utilization rate of these epoxy groups cannot be improved, and the interfacial forces between SAPO-11 and β-zeolites cannot be increased further after reaching a certain level. The prepolymer of this application is further obtained by polymerization of acrylic acid and unsaturated monomers containing epoxy groups. The number of epoxy groups in the prepolymer can be controlled by the acrylic acid, achieving uniform dispersion of the epoxy groups and thus improving their utilization rate. This further enhances the interfacial bonding between SAPO-11 and β-zeolites.

[0041] Optionally, the molar ratio of the acrylic acid and the epoxy-containing unsaturated monomer is 1:(0.2-0.4).

[0042] Under the above-mentioned raw material dosage, the prepolymer can achieve the best interfacial enhancement effect on the two molecular sieves, and the catalyst has the highest mechanical strength under the test, thus extending the service life of the catalyst.

[0043] According to another aspect of this application, a method for preparing bio-jet fuel by hydrogenating microalgae oil is provided, comprising the steps of: The multi-level porous composite molecular sieve catalyst for catalytic hydrogenation described in any of the above items is packed into a fixed-bed reactor. Preheated microalgae oil is pumped into the fixed-bed reactor, and the hydrogenation reaction yields the reaction product. After distillation, bio-jet fuel is obtained.

[0044] This hierarchical porous composite molecular sieve catalyst possesses both excellent hydrogenation activity and isomerization performance. In the process of preparing bio-jet fuel from microalgae oil, it can effectively improve the oxidation stability of the oil, enhance the selectivity of isomers, and significantly reduce the freezing point of bio-jet fuel.

[0045] Optionally, the preheating temperature of the microalgae oil is 60-80℃.

[0046] This preheating reduces the viscosity of the microalgae oil, enabling rapid contact with the multi-level porous composite molecular sieve catalyst and improving hydrogenation efficiency.

[0047] Optionally, the hydrogenation reaction is carried out at a temperature of 300-330℃, a pressure of 2-6 MPa, and a liquid hourly space velocity of 0.5-1.5 h⁻¹. - ¹, The hydrogen-to-oil ratio is (1000-2000):1.

[0048] The above parameters enable continuous production of bio-jet fuel from microalgae oil, improving production efficiency and raw material utilization.

[0049] The beneficial effects of this application include, but are not limited to: 1. The hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation according to this application fully utilizes the core-shell structure confinement effect through bimetallic partitioned loading of the core and shell. Hydrogenation and deoxygenation are controlled by the active metal / β at the inlet, and small molecule straight-chain alkanes are selectively screened into the internal core through hierarchical channels. The active metal / SAPO-11 performs deep hydrogenation isomerization on intermediates, ultimately achieving one-step efficient production of biojet fuel.

[0050] 2. According to the multi-level porous composite molecular sieve catalyst for catalytic hydrogenation of this application, by treating SAPO-11 with NH4F solution, high-temperature steam, and two-step crystallization, the β molecular sieve in step (2) can form a directional heterogeneous composite structure on the surface of SAPO-11 molecular sieve and weaken uniform nucleation growth. Therefore, it can initially weaken the interface boundary and improve the composite effect of the two molecular sieves.

[0051] 3. According to the multi-level porous composite molecular sieve catalyst for catalytic hydrogenation of this application, the addition of polyethyleneimine in step (1) can form a pore structure during calcination, realize the uniform transition between macropores and mesopores, thereby improving the service life and catalytic effect of the catalyst, so as to improve the content of isomerization products and the freezing point control.

[0052] 4. According to the preparation method of the hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation in this application, the acrylamide contained in the β molecular sieve precursor solution can, firstly, increase the interfacial interaction with SAPO-11 molecular sieve, further guiding the β molecular sieve crystal nuclei to preferentially nucleate on the SAPO-11 surface and grow along a specific crystal orientation; secondly, it can undergo double bond polymerization and ring-opening reaction with the prepolymer, thereby improving the binding effect between the prepolymer and the β molecular sieve and eliminating the interfacial boundary with SAPO-11.

[0053] 5. According to the preparation method of the hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation of this application, the addition of the prepolymer solution can realize the interfacial connection between SAPO-11 molecular sieve and β molecular sieve to eliminate the interfacial boundary, thereby avoiding the removal of the shell, improving the strength of the composite molecular sieve, extending the service life of the composite molecular sieve, and making it more suitable for catalytic hydrogenation of microalgae oil to prepare bio-jet fuel.

[0054] 6. The preparation method for preparing bio-jet fuel by hydrogenation of microalgae oil according to this application utilizes a hierarchical porous composite molecular sieve catalyst to achieve catalytic hydrogenation of microalgae oil, which solves the problems of low jet fuel yield and failure to meet freezing point in the existing microalgae oil preparation process, and represents a significant improvement compared to the prior art.

[0055] 7. The method for preparing bio-jet fuel by hydrogenation of microalgae oil according to this application allows for the reuse of multi-level porous composite molecular sieve catalysts, reducing the cost of catalyst use and thus lowering the production cost of bio-jet fuel, facilitating its industrial application. Detailed Implementation

[0056] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0057] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application were all purchased commercially.

[0058] Unless otherwise specified, the methods used in the embodiments and comparative examples of this application are conventional methods in the prior art. In the embodiments and comparative examples of this application, aging refers to placing the substance at room temperature, calcination refers to calcination in an air atmosphere, reduction refers to calcination in a hydrogen atmosphere, the pressure of the pressure impregnation is 0.5 MPa, and the molecular weight of the polyethyleneimine is 2000.

[0059] Example 1 This embodiment relates to a method for preparing a hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation, which includes the following steps: (1) Aluminum source, phosphorus source, silicon source and water were used as reactants with a molar ratio of 1:0.8:0.1:40, where the aluminum source was calculated as Al2O3, the phosphorus source as P2O5, and the silicon source as SiO2. After adjusting the pH to 5.5, di-n-propylamine, a microporous molecular sieve template agent and polyethyleneimine were added. After aging for 12 h and crystallizing at 180℃ for 24 h, intermediate A was obtained. The molar ratio of microporous molecular sieve template agent to aluminum source was 2.5:1. The aluminum source was calculated as Al2O3. The mass of polyethyleneimine accounted for 50 wt% of the aluminum source. Boehmite was used as the aluminum source, silica sol was used as the silicon source, and phosphoric acid was used as the phosphorus source. (2) Intermediate A was impregnated with 0.1 mol / L NH4F solution, treated at 80°C for 2 h, filtered, dried at 80°C for 6 h, and then treated with high temperature steam at 500°C for 4 h, dried at 80°C for 6 h. After that, intermediate A was impregnated in a solution of nickel nitrate hexahydrate and ammonium metatungstate hydrate, both with a concentration of 10 wt%, the mass of nickel nitrate hexahydrate being 5 wt% of the total mass of intermediate A, the mass of ammonium metatungstate hydrate being 5 wt% of the total mass of intermediate A, aged for 12 h, dried at 80°C for 12 h, and calcined at 450°C for 6 h to obtain intermediate B; (3) Intermediate B was placed in a 3% N-aminoethyl-3-aminopropyltriethoxysilane solution and ultrasonically treated at 50°C for 15 min. After filtration and drying, intermediate B was obtained. Then, the modified intermediate B was added to the β molecular sieve precursor solution and crystallized at 80°C for 12 h. Then, the temperature was raised to 120°C and crystallized for 48 h to obtain intermediate C. The β molecular sieve precursor solution contained 5 wt% acrylamide in the total weight of the β molecular sieve precursor solution. The β molecular sieve precursor solution was composed of silica sol, sodium aluminate, tetraethylammonium hydroxide and water in a molar ratio of 1:0.01:0.2:15. The aluminum source was calculated as Al2O3 and the silicon source was calculated as SiO2. (4) Intermediate C was placed in a prepolymer solution of glycidyl methacrylate and acrylic acid, impregnated under pressure for 30 min, stirred at 65 °C for 6 h, filtered, and calcined at 500 °C for 4 h to obtain intermediate D. The prepolymer solution was obtained by polymerization of acrylic acid and unsaturated monomers containing epoxy groups. The preparation method of the prepolymer solution was as follows: glycidyl methacrylate and acrylic acid with a molar ratio of 0.4:1 were added to the solvent, and ammonium persulfate accounting for 1 wt% of the total mass of the reactants was added as an initiator, and polymerization was carried out at 65 °C for 2 h. (5) The intermediate D is immersed in a 10wt% solution of cobalt nitrate hexahydrate, aged for 12h, dried at 80℃ for 12h, calcined at 450℃ for 6h, and reduced at 550℃ for 2h to obtain the cobalt nitrate hexahydrate, which is 25wt% of the total mass of the intermediate D.

[0060] Example 2 This embodiment relates to a method for preparing a hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation, which includes the following steps: (1) Aluminum source, phosphorus source, silicon source and water were used as reactants with a molar ratio of 1:1.0:0.6:60, where aluminum source was calculated as Al2O3, phosphorus source as P2O5 and silicon source as SiO2. After adjusting the pH to 5.5, diisopropylamine and polyethyleneimine, microporous molecular sieve template agents were added. After aging for 12 h and crystallizing at 180℃ for 24 h, intermediate A was obtained. The molar ratio of microporous molecular sieve template agent to aluminum source was 1:1. Aluminum source was calculated as Al2O3. The mass of polyethyleneimine accounted for 50 wt% of aluminum source. Aluminum isopropoxide was used as aluminum source, silica sol was used as silicon source and ammonium dihydrogen phosphate was used as phosphorus source. (2) Intermediate A was impregnated with 0.3 mol / L NH4F solution, treated at 60℃ for 2 h, filtered, dried at 80℃ for 6 h, and then treated with high temperature steam at 440℃ for 6 h and dried at 80℃ for 6 h. Then, intermediate A was impregnated in a solution of nickel nitrate hexahydrate and ammonium niobate oxalate hydrate, both with a concentration of 25 wt%, the mass of nickel nitrate hexahydrate being 20 wt% of the total mass of intermediate A and the mass of ammonium niobate oxalate hydrate being 5 wt% of the total mass of intermediate A. After aging for 12 h, dried at 120℃ for 10 h and calcined at 550℃ for 2 h to obtain intermediate B; (3) Intermediate B was placed in a 0.5% 3-aminopropyldimethoxymethylsilane solution and ultrasonically treated at 60°C for 20 min. After filtration and drying, intermediate B was obtained. Then, the modified intermediate B was added to the β molecular sieve precursor solution and crystallized at 100°C for 6 h. Then, the temperature was raised to 150°C and crystallized for 24 h to obtain intermediate C. The β molecular sieve precursor solution contained acrylamide accounting for 15 wt% of the total weight of the β molecular sieve precursor solution. The β molecular sieve precursor solution was composed of silica sol, sodium aluminate, tetraethylammonium hydroxide and water in a molar ratio of 1:0.05:0.6:40. The aluminum source was calculated as Al2O3 and the silicon source was calculated as SiO2. (4) Intermediate C was placed in a prepolymer solution of allyl glycidyl ether and acrylic acid, impregnated under pressure for 30 min, stirred at 75 °C for 4 h, filtered, and calcined at 500 °C for 4 h to obtain intermediate D. The prepolymer solution was obtained by polymerization of acrylic acid and unsaturated monomers containing epoxy groups. The preparation method of the prepolymer solution was as follows: allyl glycidyl ether and acrylic acid with a molar ratio of 0.2:1 were added to the solvent, and ammonium persulfate accounting for 1 wt% of the total mass of the reactants was added as an initiator, and polymerization was carried out at 75 °C for 1 h. (5) The intermediate D is immersed in a solution of cobalt nitrate hexahydrate and nickel nitrate hexahydrate, both with a concentration of 25wt%, aged for 12h, dried at 120℃ for 10h, calcined at 550℃ for 2h, and reduced at 450℃ for 6h to obtain the intermediate. The mass of cobalt nitrate hexahydrate is 5wt% of the total mass of intermediate D, and the mass of nickel nitrate hexahydrate is 5wt% of the total mass of intermediate D.

[0061] Example 3 This embodiment relates to a method for preparing a hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation, which includes the following steps: (1) Aluminum source, phosphorus source, silicon source and water were used as reactants with a molar ratio of 1:0.9:0.5:50, where the aluminum source was calculated as Al2O3, the phosphorus source as P2O5, and the silicon source as SiO2. After adjusting the pH to 5.5, diethylamine, a microporous molecular sieve template agent and polyethyleneimine were added. After aging for 12 h and crystallizing at 180℃ for 24 h, intermediate A was obtained. The molar ratio of microporous molecular sieve template agent to aluminum source was 1.8:1. The aluminum source was calculated as Al2O3. The mass of polyethyleneimine accounted for 50 wt% of the aluminum source. Sodium aluminate was used as the aluminum source, silica sol was used as the silicon source, and ammonium dihydrogen phosphate was used as the phosphorus source. (2) Intermediate A was impregnated with 0.2 mol / L NH4F solution, treated at 70°C for 1 h, filtered, dried at 80°C for 6 h, and then treated with high temperature steam at 480°C for 5 h, dried at 80°C for 6 h. After that, intermediate A was impregnated in a solution of nickel nitrate hexahydrate with a concentration of 15 wt%, the mass of nickel nitrate hexahydrate being 15 wt% of the total mass of intermediate A, aged for 12 h, dried at 80°C for 12 h, and calcined at 550°C for 2 h to obtain intermediate B; (3) Intermediate B was placed in a 1% N-aminoethyl-3-aminopropyltriethoxysilane solution and ultrasonically treated at 50°C for 30 min. After filtration and drying, intermediate B was obtained. Then, the modified intermediate B was added to the β molecular sieve precursor solution and crystallized at 90°C for 10 h. Then, the temperature was raised to 130°C and crystallized for 28 h to obtain intermediate C. The β molecular sieve precursor solution contained 10 wt% acrylamide in the total weight of the β molecular sieve precursor solution. The β molecular sieve precursor solution was composed of silica sol, sodium aluminate, tetraethylammonium hydroxide and water in a molar ratio of 1:0.03:0.4:25. The aluminum source was calculated as Al2O3 and the silicon source was calculated as SiO2. (4) Intermediate C was placed in a prepolymer solution of glycidyl methacrylate and acrylic acid, impregnated under pressure for 30 min, stirred at 70 °C for 5 h, filtered, and calcined at 500 °C for 4 h to obtain the prepolymer solution. The prepolymer solution was obtained by polymerization of acrylic acid and unsaturated monomers containing epoxy groups. The preparation method of the prepolymer solution was as follows: glycidyl methacrylate and acrylic acid with a molar ratio of 0.3:1 were added to the solvent, and ammonium persulfate accounting for 1 wt% of the total mass of the reactants was added as an initiator. The polymerization was carried out at 70 °C for 1.5 h. (5) The intermediate D is immersed in a solution of cobalt nitrate hexahydrate and ammonium molybdate tetrahydrate, both with a concentration of 15wt%, aged for 12h, dried at 80℃ for 12h, calcined at 500℃ for 4h, and reduced at 450℃ for 4h to obtain the intermediate. The mass of cobalt nitrate hexahydrate is 15wt% of the total mass of intermediate D, and the mass of ammonium molybdate tetrahydrate is 5wt% of the total mass of intermediate D.

[0062] Example 4 The difference between this embodiment and Embodiment 3 is that the mass of polyethyleneimine accounts for 100 wt% of the aluminum source.

[0063] Example 5 The difference between this embodiment and Example 3 is that the concentration of the NH4F solution is 0.5 mol / L.

[0064] Example 6 The difference between this embodiment and Embodiment 3 is that the temperature of the high-temperature steam is 400°C.

[0065] Example 7 The difference between this embodiment and Embodiment 3 is that no acrylic acid is added in the preparation of the prepolymer solution; that is, only glycidyl methacrylate is used to obtain the prepolymer solution.

[0066] Example 8 The difference between this embodiment and Example 3 is that the molar ratio of glycidyl methacrylate to acrylic acid is 0.1:1.

[0067] Comparative Example 1 The difference between this comparative example and Example 3 is that polyethyleneimine is not added in step (1).

[0068] Comparative Example 2 The difference between this comparative example and Example 3 is that NH4F solution is not used to treat intermediate A in step (2).

[0069] Comparative Example 3 The difference between this comparative example and Example 3 is that intermediate A is not treated with high-temperature steam in step (2).

[0070] Comparative Example 4 The difference between this comparative example and Example 3 is that the β-zeolite precursor solution in step (3) does not contain acrylamide.

[0071] Comparative Example 5 The difference between this comparative example and Example 3 is that the prepolymer impregnation in step (4) is not performed. Intermediate C is calcined at 500°C for 4 hours to obtain intermediate D, and then step (5) is performed.

[0072] Comparative Example 6 The difference between this comparative example and Example 3 is that glycidyl methacrylate is not added in step (4), that is, only the prepolymer solution obtained by acrylic acid is used.

[0073] Test Example 1 At least 50 shaped catalyst particles (such as cylindrical or clover-shaped) prepared according to the above embodiments and comparative examples were taken. Using a particle strength tester, pressure was applied along the radial direction, and the instantaneous maximum force value at the time of crushing was recorded. The average crushing strength of all tested particles was calculated, and the results are shown in Table 1.

[0074] The specific surface area and pore volume of the catalysts prepared in the above examples and comparative examples were tested. The test results are shown in Table 1. The specific test methods are as follows: Specific surface area, pore volume, and average pore size were measured using a physical adsorption analyzer (Microtrac BELSORP MAX X). Before testing, the samples underwent vacuum degassing pretreatment (temperature: 300℃, time: 6h, vacuum degree ≤10Pa).

[0075] BET specific surface area (S) BET ): Based on the Brunauer-Emmett-Teller (BET) theory, adsorption data within the relative pressure (P / P0) range of 0.05–0.30 were used for calculation; Micropore volume, mesopore volume, and macropore volume: obtained by integration using the NLDFT model, total pore volume (V 总 = Micropore volume + Mesopore volume + Macropore volume; Average aperture: calculated using the formula .

[0076] Table 1

[0077] Test Example 2 Catalytic hydrogenation tests were conducted using microalgae oil of the same quality. The hierarchical porous composite molecular sieve catalysts prepared in the above examples and comparative examples were loaded into a fixed-bed reactor with a loading height of 8 times the reactor diameter. The reaction was carried out at a temperature of 330°C, a reaction pressure of 4 MPa, and a liquid hourly space velocity of 1.5 h⁻¹. - ¹, under a hydrogen-to-oil ratio of 1000:1, the product is reacted with microalgae oil preheated to 60°C. The product is collected, washed with 1% sodium hydroxide aqueous solution, and the aqueous phase is separated, while the oil phase is collected. The oil phase enters a distillation column, and the fraction collected at 130°C-300°C is the bio-jet fuel.

[0078] 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 2.

[0079] Where isomer selectivity = [(C6-C18) peak area ratio of isomer products / peak area ratio of all products] × 100%, in units of 100%.

[0080] Aviation kerosene yield = [(130℃-300℃) fraction weight / total oil product weight] × liquid phase yield × 100%, in units of 100%.

[0081] Thermal oxidative stability was determined according to national standard GB / T 9169-2023.

[0082] Table 2

[0083] Test Example 3 Catalytic hydrogenation tests were conducted using microalgae oil of the same quality. The multi-level porous composite molecular sieve catalysts prepared in the above examples and comparative examples were repeatedly used for catalysis 20 times in the manner of Test Example 2. The decrease rate of isomer selectivity and the decrease rate of jet fuel yield were tested. The test results are shown in Table 3.

[0084] The rate of decrease in heteroselectivity is calculated as follows: [(first heteroselectivity - 20th heteroselectivity) / first heteroselectivity] × 100%, with units of 1.

[0085] Aviation kerosene yield decline rate = [(first aviation kerosene yield - 20th aviation kerosene yield) / first aviation kerosene yield] × 100%, unit is .

[0086] Table 3

[0087] As can be seen from the above test examples, the multi-level porous composite molecular sieve catalyst of this application has a higher average crushing strength and has micropores, mesopores and macropores, which can achieve a uniform transition of pores, improve the service life and catalytic effect of the multi-level porous composite molecular sieve catalyst, and thus improve the isomerization yield and product quality of bio-jet fuel.

[0088] A comparison of Examples 4 and 3 shows that increasing the amount of polyethyleneimine added reduces the average crushing strength of the catalyst and the overall pore volume, which in turn reduces the isomerization selectivity and jet fuel yield, and causes the freezing point to rise.

[0089] A comparison of Examples 5, 6, and 3 shows that changes in the treatment conditions of intermediate A affect the growth of the β-zeolite, leading to a decrease in the average crushing strength, specific surface area, and pore volume of the catalyst, ultimately resulting in a decline in catalytic performance. A comparison of Comparative Examples 2, 3, and 3 shows that not treating intermediate A with NH4F solution or high-temperature steam causes a greater decrease in the average crushing strength, specific surface area, and pore volume of the catalyst, confirming that these two steps are indispensable for forming a highly crystalline hierarchical porous composite zeolite and severely impact catalytic performance.

[0090] According to the comparison of Examples 7, 8 and Example 3, the amount of acrylic acid added in the prepolymer can affect the enhancement effect on the catalyst interface, directly affecting its average crushing strength, specific surface area, pore volume and average pore size, and indirectly affecting the catalytic hydrogenation effect on microalgae oil, resulting in a decrease in isomer selectivity, jet fuel yield and cycle catalytic stability.

[0091] The comparison between Comparative Example 1 and Example 3 shows that the absence of polyethyleneimine significantly reduces the pore volume of micropores, mesopores, and macropores in the catalyst, demonstrating that its addition can adjust the structure and number of pores, and also indirectly affects the average crushing strength through the adjustment of pore volume.

[0092] The comparison between Comparative Example 4 and Example 3 shows that the absence of acrylamide during the formation of β-zeolite not only affects the specific surface area and pore volume of the catalyst, but also the average crushing strength. This demonstrates that the addition of acrylamide can improve the interfacial interaction between the two types of zeolites, thereby enhancing the catalytic effect.

[0093] The comparison between Comparative Example 5 and Example 3 shows that if intermediate B is not treated with prepolymer, the interfacial connectivity of the catalyst is reduced, which in turn reduces the average crushing strength and the mesoporous volume, ultimately leading to a decrease in isomerization selectivity and jet fuel yield.

[0094] A comparison of Comparative Example 6 and Example 3 shows that the absence of epoxy-containing unsaturated monomers prevents the formation of effective chemical bonds with the molecular sieve, resulting in a decrease in crushing strength. Furthermore, the absence of glycidyl methacrylate-based cross-linked polymer networks, which contribute more porosity after calcination, directly leads to a decrease in the carrier's pore volume, thereby reducing the catalytic effect on microalgae oil.

[0095] 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 preparing a hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation, characterized in that, Includes the following steps: (1) Using aluminum, phosphorus, silicon and water as reactants in a molar ratio of 1:(0.8-1.0):(0.1-0.6):(40-60), where aluminum source is calculated as Al2O3, phosphorus source as P2O5 and silicon source as SiO2, after adjusting the pH, microporous molecular sieve template agent and polyethyleneimine are added, and after aging and crystallization, intermediate A is obtained; (2) Intermediate A is treated sequentially with NH4F solution and high-temperature steam, then immersed in a solution containing the first active metal component, aged, dried and calcined to obtain intermediate B. The mass of the first active metal component is 10%-25wt% of the total mass of intermediate A, and the first active metal component contains at least nickel. (3) Intermediate B is modified with an aminosilane coupling agent, and then added to the β molecular sieve precursor solution. It is crystallized at 80-100℃ for 6-12h, and then heated to 120-150℃ for 24-48h to obtain intermediate C. The β molecular sieve precursor solution contains 5%-15wt% acrylamide in the total weight of the β molecular sieve precursor solution. (4) Place intermediate C in a prepolymer solution, impregnate under pressure, stir and react at 65-75°C for at least 4 hours, filter and calcine to obtain intermediate D, wherein the reacting monomers in the prepolymer solution include at least unsaturated monomers containing epoxy groups. (5) The intermediate D is immersed in a solution containing the second active metal component, aged, dried, roasted and reduced to obtain the intermediate D. The mass of the second active metal component is 10%-25wt% of the total mass of the intermediate D, and the second active metal component contains at least cobalt.

2. The method for preparing a hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation according to claim 1, characterized in that, The molar ratio of the microporous molecular sieve template agent to the aluminum source in step (1) is (1.0-2.5):1, and the aluminum source is calculated as Al2O3; The molecular weight of polyethyleneimine is 2000, and the mass of polyethyleneimine accounts for 50 wt% of the aluminum source.

3. The method for preparing a hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation according to claim 1, characterized in that, In step (2), the concentration of NH4F solution is 0.1-0.3 mol / L, the treatment temperature is 60-80℃, and the treatment time is 1-2h.

4. The method for preparing the hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation according to claim 3, characterized in that, The temperature of the high-temperature steam in step (2) is 440-500℃, and the treatment time is 4-6h; The roasting temperature in step (2) is 450-550℃, and the processing time is 2-6h.

5. The method for preparing a hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation according to claim 1, characterized in that, The β-zeolite precursor liquid in step (3) includes a silicon source, an aluminum source, a template agent and water. The molar ratio of the silicon source, aluminum source, template agent and water is 1:(0.01-0.05):(0.2-0.6):(15-40), where the aluminum source is calculated as Al2O3 and the silicon source is calculated as SiO2.

6. The method for preparing a hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation according to claim 1, characterized in that, The unsaturated monomer containing an epoxy group is selected from at least one of glycidyl methacrylate and allyl glycidyl ether.

7. The method for preparing a hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation according to claim 6, characterized in that, The prepolymer solution is obtained by polymerizing acrylic acid and an unsaturated monomer containing epoxy groups. The preparation method of the prepolymer solution is as follows: The unsaturated monomer containing epoxy groups and the acrylic acid are added to a solvent and polymerized for 1-2 hours under the action of an initiator to obtain the prepolymer solution.

8. The method for preparing a hierarchical porous composite molecular sieve catalyst for catalytic hydrogenation according to claim 7, characterized in that, The molar ratio of the acrylic acid and the epoxy-containing unsaturated monomer is 1:(0.2-0.4).

9. A method for preparing bio-jet fuel by hydrogenation of microalgae oil, characterized in that, Including the following steps: The multi-level porous composite molecular sieve catalyst prepared by the method of any one of claims 1-8 for catalytic hydrogenation is packed into a fixed-bed reactor. Preheated microalgae oil is pumped into the fixed-bed reactor, and hydrogenation reaction is carried out to obtain reaction products. After distillation, bio-jet fuel is obtained.

10. The method for preparing bio-jet fuel by hydrogenation of microalgae oil according to claim 9, characterized in that, The preheating temperature of the microalgae oil is 60-80℃; and / or The hydrogenation reaction is carried out at a temperature of 300-330℃, a pressure of 2-6 MPa, and a liquid hourly space velocity of 0.5-1.5 h⁻¹. - ¹, The hydrogen-to-oil ratio is (1000-2000):1.

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