A ruthenium-modified mesoporous molecular sieve-based catalyst and its preparation method and application

Abstract

The present invention discloses a ruthenium-modified mesoporous molecular sieve-based catalyst and its preparation method and application, belonging to the technical field of polyethylene cracking catalysts. The present invention uses a ruthenium-modified mesoporous molecular sieve as a matrix, replaces the silanol groups of the ruthenium-modified mesoporous molecular sieve with Al atoms, and grafts the Al atoms onto the ruthenium-modified mesoporous molecular sieve, thereby introducing acidic sites on the surface of the ruthenium-modified mesoporous molecular sieve to obtain a ruthenium-modified mesoporous molecular sieve-based catalyst. The present invention introduces Al into the ruthenium-modified mesoporous molecular sieve through a post-grafting method, thereby introducing acidic sites. The introduction of the acidic sites effectively improves the catalytic reaction efficiency of the catalyst, thereby shortening the catalytic reaction time and improving the distribution of the catalytic products through the mesoporous channels of the mesoporous molecular sieve. The present invention further improves the catalytic reaction efficiency by the synergistic effect of metallic ruthenium and the acidic sites.

Description

Technical Field

[0001] The present invention relates to the technical field of polyethylene hydrocracking catalysts, and in particular to a ruthenium-modified mesoporous molecular sieve-based catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Plastics are widely used in daily life, but they have serious problems such as large production scale, low recycling rate, slow natural degradation rate, and great harm to the human body. How to efficiently recycle and reuse waste plastics is of great significance to environmental governance and human health.

[0003] Polyethylene (PE) accounts for a significant portion of waste plastics. Yosuke Nakaji et al. directly loaded Ru onto CeO2 for direct hydrogenolysis, demonstrating superior activity compared to other metal-supported catalysts in the hydrogenolysis of low-density polyethylene (LDPE). Kang et al. used a precise impregnation method to uniformly distribute Ru nanoparticles within the channels of an SBA-15 support, achieving significant improvements in the catalytic performance of polyethylene for conversion to high-value liquid fuels, particularly diesel. However, the resulting Ru nanoparticle-loaded SBA-15 catalyst exhibited low catalytic efficiency and a tendency to undergo methanation during polyethylene cracking. Summary of the Invention

[0004] The present invention provides a ruthenium-modified mesoporous molecular sieve-based catalyst, a preparation method and an application thereof, which effectively solve the technical problems of low catalytic reaction efficiency, poor product selectivity and easy methanation of existing polyethylene hydrocracking catalysts. The present invention introduces Al into the ruthenium-modified mesoporous molecular sieve by a grafting method, thereby introducing acidic sites, improving the catalytic reaction efficiency of the ruthenium-modified mesoporous molecular sieve, thereby shortening the catalytic reaction time, and simultaneously solving the problem of easy methanation in polyethylene hydrocracking caused by using ruthenium-modified mesoporous molecular sieve as a catalyst.

[0005] The first object of the present invention is to provide a method for preparing a ruthenium-modified mesoporous molecular sieve-based catalyst, comprising the following steps:

[0006] Preparation of ruthenium-modified mesoporous molecular sieves.

[0007] The ruthenium modified mesoporous molecular sieve is used as a matrix and added to the soluble Al 3+ An alcohol solution of a salt is stirred for reaction at room temperature, and then filtered and dried to obtain a precursor. The precursor is calcined, and the silanol groups of the ruthenium-modified mesoporous molecular sieve are replaced with Al atoms. The Al atoms are grafted onto the ruthenium-modified mesoporous molecular sieve to obtain a ruthenium-modified mesoporous molecular sieve-based catalyst.

[0008] As a preferred embodiment, in the ruthenium-modified mesoporous molecular sieve-based catalyst, the molar ratio of Si to Al is 5 to 30:1.

[0009] As a preferred embodiment, the precursor is heated to 500° C. to 550° C. and calcined for 5 h to 6 h.

[0010] As a preferred embodiment, the mesoporous molecular sieve is SBA-15.

[0011] As a preferred embodiment, the ruthenium modified mesoporous molecular sieve and soluble Al 3+ The dosage ratio of salt is 0.5g:0.3mmol~1.65mmol.

[0012] As a preferred embodiment, the preparation method of the ruthenium-modified mesoporous molecular sieve comprises the following steps:

[0013] Adding a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer to a hydrochloric acid aqueous solution and dissolving it at 35° C. to 45° C., and then adding tetraethoxysilane to obtain a forming agent;

[0014] Mix 3-mercaptopropyltrimethoxysilane, NaOH and water, then add soluble Ru 3+ salt to obtain a reaction solution.

[0015] The reaction solution is added to the accelerator, stirred and then allowed to stand, and crystallized at 100° C. to obtain a primary product, which is then calcined at 500° C. to 550° C. for 5 h to 6 h to obtain a ruthenium-modified mesoporous molecular sieve.

[0016] As a preferred embodiment, the mass ratio of the sodium hydroxide, 3-mercaptopropyltrimethoxysilane, and water is 1:1~1.5:10~50; the amount ratio of the 3-mercaptopropyltrimethoxysilane to the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer is 1:33.3~50.

[0017] As a preferred embodiment, the 3-mercaptopropyltrimethoxysilane and soluble Ru 3+ The mass ratio of salt is 1:0.5~2.

[0018] As a preferred embodiment, cetyltrimethylammonium bromide is further added to the accelerator, and the mass ratio of the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer to cetyltrimethylammonium bromide is 5:0.8~1.

[0019] The second object of the present invention is to provide a ruthenium-modified mesoporous molecular sieve-based catalyst prepared by the above-mentioned preparation method.

[0020] The third object of the present invention is to provide an application of the above-mentioned ruthenium-modified mesoporous molecular sieve-based catalyst in catalyzing the hydrocracking of polyethylene.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a method for preparing a ruthenium-modified mesoporous molecular sieve-based catalyst. The method comprises the following steps: first, preparing a ruthenium-modified mesoporous molecular sieve; then, using the ruthenium-modified mesoporous molecular sieve as a matrix, replacing the silanol groups of the ruthenium-modified mesoporous molecular sieve with Al atoms; and grafting the Al atoms onto the ruthenium-modified mesoporous molecular sieve to introduce acidic sites on the surface of the ruthenium-modified mesoporous molecular sieve to obtain a ruthenium-modified mesoporous molecular sieve-based catalyst. Based on the fact that mesoporous molecular sieves have a large specific surface area and pore volume, a regular and orderly pore structure, and pore size adjustability, but lack acidic sites, the present invention introduces Al into the ruthenium-modified mesoporous molecular sieve through a post-grafting method, thereby introducing acidic sites. The introduction of the acidic sites effectively improves the catalytic reaction efficiency of the catalyst, thereby shortening the catalytic reaction time and improving the distribution of the catalytic products through the mesoporous channels of the mesoporous molecular sieve. The present invention further improves the catalytic reaction efficiency by the synergistic effect of metallic ruthenium and the acidic sites.

[0023] The present invention synthesized three ruthenium-modified mesoporous molecular sieves with different morphologies. When the water bath temperature is controlled at 35°C, the ruthenium-modified mesoporous molecular sieves form columns. The addition of hexadecyltrimethylammonium bromide (CTAB) during the synthesis promotes the formation of spherical ruthenium-modified mesoporous molecular sieves. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is an SEM image of the spherical ruthenium-modified mesoporous molecular sieve-based catalyst prepared in Example 1 of the present invention.

[0025] Figure 2 This is the BET diagram of the spherical ruthenium-modified mesoporous molecular sieve-based catalyst prepared in Example 1 of the present invention.

[0026] Figure 3 This is an SEM image of the columnar ruthenium-modified mesoporous molecular sieve-based catalyst prepared in Example 2 of the present invention.

[0027] Figure 4 This is the BET diagram of the columnar ruthenium-modified mesoporous molecular sieve-based catalyst prepared in Example 2 of the present invention.

[0028] Figure 5 This is an SEM image of the short rod-shaped ruthenium-modified mesoporous molecular sieve-based catalyst prepared in Example 3 of the present invention.

[0029] Figure 6 This is the BET diagram of the short rod-shaped ruthenium-modified mesoporous molecular sieve-based catalyst prepared in Example 3 of the present invention.

[0030] Figure 7This is a distribution diagram of liquid products from the hydrocracking of polyethylene catalyzed by the spherical ruthenium-modified mesoporous molecular sieve-based catalyst prepared in Example 1 of the present invention.

[0031] Figure 8 This is a distribution diagram of liquid products from the hydrocracking of polyethylene catalyzed by the columnar ruthenium-modified mesoporous molecular sieve-based catalyst prepared in Example 2 of the present invention.

[0032] Figure 9 This is a distribution diagram of liquid products from the hydrocracking of polyethylene catalyzed by the short rod-shaped ruthenium-modified mesoporous molecular sieve-based catalyst prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0033] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention is further described below with reference to specific examples, but the examples are not intended to limit the present invention. The following experimental and detection methods are conventional methods unless otherwise specified; the reagents and raw materials are commercially available unless otherwise specified.

[0034] Existing catalysts containing Ru nanoparticles loaded on SBA-15 suffer from low catalytic efficiency, poor product selectivity, and easy methanation when catalyzing polyethylene cracking. The present invention provides a ruthenium-modified mesoporous molecular sieve-based catalyst, its preparation method, and its application.

[0035] The technical solution of the present invention is described in detail below.

[0036] The present invention provides a method for preparing a ruthenium-modified mesoporous molecular sieve-based catalyst, comprising the following steps:

[0037] S1, preparation of ruthenium-modified mesoporous molecular sieve.

[0038] S2, using the ruthenium modified mesoporous molecular sieve as a matrix, adding to the soluble Al 3+ An alcohol solution of a salt is stirred for reaction at room temperature, and then filtered and dried to obtain a precursor. The precursor is calcined, and the silanol groups of the ruthenium-modified mesoporous molecular sieve are replaced with Al atoms. The Al atoms are grafted onto the ruthenium-modified mesoporous molecular sieve to obtain a ruthenium-modified mesoporous molecular sieve-based catalyst.

[0039] In the above-mentioned technical solution, aluminum is introduced into the ruthenium-modified mesoporous molecular sieve SBA-15 via a post-grafting method, thereby introducing acidic sites. The introduction of these acidic sites effectively improves the catalytic reaction efficiency of the catalyst, thereby shortening the catalytic reaction time and improving the distribution of the catalytic products through the mesoporous channels of SBA-15. The present invention further improves the catalytic reaction efficiency by synergizing the metallic ruthenium and the acidic sites.

[0040] To introduce an appropriate amount of acidic sites into the ruthenium-modified mesoporous molecular sieve, thereby maximizing the catalyst's catalytic activity, the molar ratio of Si to Al in the ruthenium-modified mesoporous molecular sieve-based catalyst is 5 to 30:1. When the Al content is high, i.e., the Si / Al ratio is low (e.g., when the Si / Al ratio is less than 5), the acidity is strong, potentially leading to excessive cracking of the reactants and an increase in gaseous products. When the Al content is low, i.e., the Si / Al ratio is high (e.g., when the Si / Al ratio is greater than 30), the acidity is weak, resulting in fewer acidic sites and poor activity.

[0041] It should be noted that, in the present invention, the precursor is heated to 500° C. to 550° C. and calcined for 5 h to 6 h to obtain a ruthenium-modified mesoporous molecular sieve-based catalyst.

[0042] It should be noted that the molecular mesoporous sieve used in the present invention is SBA-15.

[0043] In order to control the molar ratio of Si to Al on the final product Ruthenium-modified mesoporous molecular sieve-based catalyst to be 5-30:1, the Ruthenium-modified mesoporous molecular sieve and the soluble Al 3+ The dosage ratio of salt is 0.5g:0.3mmol~1.65mmol.

[0044] The preparation method of the ruthenium-modified mesoporous molecular sieve adopted in the present invention comprises the following steps:

[0045] Adding a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer to a hydrochloric acid aqueous solution and dissolving it at 35° C. to 45° C., and then adding tetraethoxysilane to obtain a forming agent;

[0046] Mix 3-mercaptopropyltrimethoxysilane, NaOH and water, then add soluble Ru 3+ salt to obtain a reaction solution.

[0047] The reaction solution is added to the accelerator, stirred and then allowed to stand, and crystallized at 100° C. to obtain a primary product, which is then calcined at 500° C. to 550° C. for 5 h to 6 h to obtain a ruthenium-modified mesoporous molecular sieve.

[0048] In the above-mentioned preparation method of ruthenium-modified mesoporous molecular sieve, the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, namely P123, plays the role of a structure-directing agent in the synthesis of ruthenium-modified mesoporous molecular sieve. In the synthesis process of ruthenium-modified mesoporous molecular sieve, P123 acts as a template to guide the structure of the ruthenium-modified mesoporous molecular sieve to be columnar. P123 is dissolved in an aqueous hydrochloric acid solution. The concentration and dosage of hydrochloric acid, as well as the stirring temperature, stirring speed and other surfactants will cause the morphology of the ruthenium-modified mesoporous molecular sieve to change. If the stirring speed is too fast, the finally synthesized ruthenium-modified mesoporous molecular sieve will be curved. If the temperature is too high, the ruthenium-modified mesoporous molecular sieve will be transformed from a columnar shape to a short rod and a long rod shape.

[0049] When cetyltrimethylammonium bromide, i.e., CTAB, is added to the accelerator, the interfacial tension between the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer and silica can be reduced, so that the ruthenium-modified mesoporous molecular sieve exhibits a spherical morphology. The added mass of the CTAB is 0.2 times the mass of the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

[0050] In the preparation process of the above-mentioned ruthenium-modified mesoporous molecular sieve, in order to prepare a ruthenium-modified mesoporous molecular sieve with the expected morphology, the mass ratio of the sodium hydroxide, 3-mercaptopropyltrimethoxysilane, and water is limited to 1:1~1.5:10~50; the mass ratio of the 3-mercaptopropyltrimethoxysilane to the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer is limited to 1:33.3~50.

[0051] In order to prepare a ruthenium-modified mesoporous molecular sieve and control the loading amount of ruthenium, the present invention combines the 3-mercaptopropyltrimethoxysilane with a soluble Ru 3+ The mass ratio of salts is limited to 1:0.5-2. Ruthenium is introduced into the molecular mesoporous sieve SBA-15 via mercaptosilane modification. Using less ruthenium results in fewer metal sites and poorer reaction performance; using more ruthenium results in less mercaptosilane and incomplete ligand formation, resulting in greater ruthenium loss.

[0052] The present invention will be described in detail below through the following examples and comparative examples.

[0053] Example 1

[0054] A method for preparing a ruthenium-modified mesoporous molecular sieve-based catalyst comprises the following steps:

[0055] S1, preparation of ruthenium-modified mesoporous molecular sieve: 2g of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer and 0.4g of hexadecyltrimethylammonium bromide were added to 45g of 2mol / L hydrochloric acid and 15g of water, and stirred in a 40°C water bath for 4h to dissolve, and then 5.8g of tetraethoxysilane was added to obtain a facilitator; 0.04g of sodium hydroxide, 0.05g of 3-Trimercaptopropyltrimethoxysilane and 2 g of water were mixed, and then 1.63 mL of RuCl3 with a concentration of 100 mM was added to obtain a reaction solution; the reaction solution was added to the accelerator, stirred for 5 minutes, allowed to stand at 40°C for 24 hours, and then transferred to a crystallization kettle for crystallization at 100°C for 24 hours, filtered and washed, and dried at 80°C for 12 hours to obtain a primary product, which was calcined at 550°C for 5 hours to obtain a ruthenium-modified mesoporous molecular sieve, recorded as spherical Ru-SBA-15.

[0056] S2, add 0.11gAlCl3 into 50mL ethanol solution to dissolve to obtain AlCl3 alcohol solution, add 0.5g ruthenium-modified mesoporous molecular sieve to the AlCl3 alcohol solution, stir and react at room temperature for 12h, filter and wash with ethanol, dry at 100℃ for 12h to obtain a precursor; heat the precursor to 550℃ and calcine for 6h to obtain a ruthenium-modified mesoporous molecular sieve-based catalyst, recorded as spherical Al-Ru-SBA-15.

[0057] Example 2

[0058] A method for preparing a ruthenium-modified mesoporous molecular sieve-based catalyst comprises the following steps:

[0059] S1, preparation of ruthenium-modified mesoporous molecular sieve: add 2g of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer to 65g of 2mol / L hydrochloric acid, stir and dissolve in a water bath at 35°C for 4h, then add 4.28g of tetraethoxysilane to obtain a facilitator; mix 0.04g of sodium hydroxide, 0.05g of 3-trimercaptopropyltrimethoxysilane and 2g of water, then add 1.2mL of 100mM RuCl3 to obtain a reaction solution; add the reaction solution to the facilitator, stir for 5min, let stand at 35°C for 24h, then transfer to a crystallization kettle and crystallize at 100°C for 24h, filter and wash, and dry at 80°C for 12h to obtain a primary product, which is calcined at 550°C for 5h to obtain a ruthenium-modified mesoporous molecular sieve, recorded as columnar Ru-SBA-15.

[0060] S2, add 0.11gAlCl3 into 50mL ethanol solution to dissolve to obtain AlCl3 alcohol solution, add 0.5g ruthenium-modified mesoporous molecular sieve to the AlCl3 alcohol solution, stir and react at room temperature for 12h, filter and wash with ethanol, dry at 100℃ for 12h to obtain a precursor; heat the precursor to 550℃ and calcine for 6h to obtain a ruthenium-modified mesoporous molecular sieve-based catalyst, recorded as columnar Al-Ru-SBA-15.

[0061] Example 3

[0062] A method for preparing a ruthenium-modified mesoporous molecular sieve-based catalyst comprises the following steps:

[0063] S1, preparation of ruthenium modified mesoporous molecular sieve: add 2g of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer to 65g of 2mol / L hydrochloric acid, stir and dissolve in a water bath at 45°C for 4h, then add 4.28g of tetraethoxysilane to obtain a facilitator; mix 0.04g of sodium hydroxide, 0.05g of 3-trimercaptopropyltrimethoxysilane and 2g of water, then add 1.2mL of 100mM RuCl3 to obtain a reaction solution; add the reaction solution to the facilitator, stir for 5min, let stand at 45°C for 24h, then transfer to a crystallization kettle and crystallize at 100°C for 24h, filter and wash, and dry at 80°C for 12h to obtain a primary product, which is calcined at 550°C for 5h to obtain a ruthenium modified mesoporous molecular sieve, recorded as short rod-shaped Ru-SBA-15.

[0064] S2, add 0.11gAlCl3 into 50mL ethanol solution to dissolve to obtain AlCl3 alcohol solution, add 0.5g ruthenium-modified mesoporous molecular sieve to the AlCl3 alcohol solution, stir and react at room temperature for 12h, filter and wash with ethanol, dry at 100℃ for 12h to obtain a precursor; heat the precursor to 550℃ and calcine for 6h to obtain a ruthenium-modified mesoporous molecular sieve-based catalyst, recorded as short rod-shaped Al-Ru-SBA-15.

[0065] The performance of the ruthenium-modified mesoporous molecular sieve-based catalysts provided in Examples 1 to 3 above was tested, and the results are as follows.

[0066] Table 1 Parameters of the catalysts prepared in Examples 1 to 3 of the present invention

[0067]

[0068] Figure 1 、 Figure 3 and Figure 5 The following are SEM images of the ruthenium-modified mesoporous molecular sieve-based catalysts prepared in Examples 1 to 3 of the present invention. Figure 1 、 Figure 3 and Figure 5 It can be seen that the ruthenium-modified mesoporous molecular sieve-based catalyst prepared in Example 1 of the present invention has a spherical structure, while the ruthenium-modified mesoporous molecular sieve-based catalyst prepared in Example 2 has a columnar structure, and the ruthenium-modified mesoporous molecular sieve-based catalyst prepared in Example 3 has a short rod-like structure.

[0069] Figure 2 、 Figure 4 and Figure 6 The BET diagrams of the ruthenium-modified mesoporous molecular sieve-based catalysts prepared in Examples 1 to 3 of the present invention are shown respectively. Figure 2 、 Figure 4 、 Figure 6As shown in Table 1, the surface area, pore volume and pore diameter of the ruthenium-modified mesoporous molecular sieve are reduced before and after the introduction of Al atoms, which proves that Al atoms are successfully incorporated into the ruthenium-modified molecular mesoporous sieve-based catalyst prepared in the present invention.

[0070] Figures 7 to 9 The following are the distribution diagrams of liquid products from polyethylene hydrocracking catalyzed by ruthenium-modified mesoporous molecular sieve-based catalysts prepared in Examples 1 to 3 of the present invention. 0.5g of low-density polyethylene and 0.1g of the catalysts prepared in each Example of the present invention were physically mixed and placed in a hydrogenation reactor. The mixture was reacted at 280°C, 2MPa, and H2 for 3h. After the reaction, the gaseous products were collected and analyzed by gas chromatography. The liquid and solid products were extracted with dichloromethane and analyzed by gas chromatography using n-hexadecane as an external standard. Figure 7 It can be seen that the spherical Al-Ru-SBA-15 catalyst has a complete conversion rate for low-density polyethylene, with liquid products accounting for 87.71% and C5-C7 products accounting for 47.04%. Figure 8 It can be seen that the columnar Al-Ru-SBA-15 catalyst has a low-density polyethylene conversion rate of 83.52%, liquid products account for 50.68%, and C5-C7 products account for 41.65%. Figure 9 The short-rod Al-Ru-SBA-15 catalyst achieved a 94.64% conversion of low-density polyethylene, with a liquid product ratio of 74.22% and a C5-C7 product ratio of 43.21%. Spherical Al-Ru-SBA-15 exhibited superior catalytic performance to cylindrical Al-Ru-SBA-15 due to the uniform distribution of mesoporous pore openings in the spherical Al-Ru-SBA-15 catalyst, while the pores in the cylindrical Al-Ru-SBA-15 catalyst were located at both ends of the catalyst.

[0071] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing a ruthenium-modified mesoporous molecular sieve-based catalyst, characterized in that: The following steps are involved: Preparation of ruthenium modified mesoporous molecular sieve: add polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer to hydrochloric acid aqueous solution, dissolve at 35℃~45℃, then add tetraethoxysilane to obtain a facilitator; mix 3-mercaptopropyltrimethoxysilane, NaOH and water, then add soluble Ru 3+ salt to obtain a reaction solution; the reaction solution is added to the accelerator, stirred and then allowed to stand for crystallization to obtain a primary product, and the primary product is calcined at 500°C to 550°C for 5h to 6h to obtain a ruthenium-modified mesoporous molecular sieve; the mass ratio of the sodium hydroxide, 3-mercaptopropyltrimethoxysilane, and water is 1:1-1.5:10-50; the amount ratio of the 3-mercaptopropyltrimethoxysilane to the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer is 1:33.3-50; the 3-mercaptopropyltrimethoxysilane and the soluble Ru 3+ The mass ratio of salt is 1:0.5~2; The ruthenium modified mesoporous molecular sieve is used as a matrix and added to the soluble Al 3+ An alcohol solution of a salt is stirred at room temperature for reaction, and then filtered and dried to obtain a precursor, which is heated to 500° C. to 550° C. and calcined for 5 h to 6 h, replacing the silanol groups of the ruthenium-modified mesoporous molecular sieve with Al atoms, and grafting the Al atoms onto the ruthenium-modified mesoporous molecular sieve to obtain a ruthenium-modified mesoporous molecular sieve-based catalyst; in the ruthenium-modified mesoporous molecular sieve-based catalyst, the molar ratio of Si to Al is 5 to 30:

1.

2. The method for preparing a ruthenium-modified mesoporous molecular sieve-based catalyst according to claim 1, characterized in that: The mesoporous molecular sieve is SBA-15.

3. The method for preparing a ruthenium-modified mesoporous molecular sieve-based catalyst according to claim 1, characterized in that: Cetyltrimethylammonium bromide is also added to the accelerator, and the mass ratio of the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer to cetyltrimethylammonium bromide is 5:0.8-1.

4. A ruthenium-modified mesoporous molecular sieve-based catalyst, characterized in that: The preparation method according to any one of claims 1 to 3 is used.

5. Use of the ruthenium-modified mesoporous molecular sieve-based catalyst according to claim 4 in catalyzing the hydrocracking of polyethylene.

Images