Core-shell type composite molecular sieve as well as preparation method and application thereof

Abstract

The invention provides a core-shell type composite molecular sieve and a preparation method and application thereof, and the preparation method comprises the following steps: (1) mixing a silicon source, an aluminum source, a template agent, a 5A molecular sieve and water to obtain a gel mixture, and aging; the template agent contains hexamethylamine hydroxide, urea and urease; and (2) carrying out hydrothermal crystallization on the material obtained by aging in the step (1), washing, drying and roasting to obtain the final 5A-coated ZSM-48 core-shell composite molecular sieve. When the catalyst prepared by taking the composite molecular sieve obtained by the preparation method as the carrier is applied to an isodewaxing reaction, the selectivity of a far-end single branched chain isomer can be improved, and the quality of lubricating oil base oil is further remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic materials, and relates to a core-shell composite molecular sieve and its preparation method and application, specifically to a 5A@ZSM-48 core-shell composite molecular sieve and its preparation method and application. Background Art

[0002] With the increasingly strict environmental protection regulations and the rapid development of the automotive industry, the requirements for the quality of lubricating oil base oil are becoming more and more stringent. In addition to requiring the lubricating oil base oil to have a relatively high pour point, it is also necessary to have a good viscosity index. The isodewaxing technology is the main technical means for producing high-quality lubricating oil base oil. This technology can convert the long-chain normal paraffins with a relatively high pour point in the feedstock oil into branched isoparaffins through isomerization reaction, thereby reducing its pour point. However, the viscosity index of isoparaffins is relatively low, and the higher the degree of isomerization, the lower the viscosity index. Therefore, it is urgent to develop a new isodewaxing technology to solve the above problems.

[0003] One of the cores of the isodewaxing technology is the isomerization catalyst. At present, bifunctional isomerization catalysts with metal active components and acidic components are mostly used to respectively realize the hydrogenation dehydrogenation and skeletal isomerization reaction steps in the isomerization reaction process. Among them, the acidic component uses a molecular sieve with a suitable pore structure and acid properties. The molecular sieves mainly used are molecular sieves with one-dimensional straight pore channels, such as the AEL-type molecular sieve, MTT-type molecular sieve, TON-type molecular sieve, *MRE-type molecular sieve, etc. disclosed in US Patent Nos. US6294081B1, US11220435B1, US9677016B2, US8475648B2, US10640389B2. However, when a molecular sieve with a single pore structure is used as the acidic component of the catalyst, there are certain limitations in molecular adsorption and diffusion, which will lead to adverse phenomena such as the reactants and active centers not being able to fully contact during the isomerization reaction process, excessive isomerization of the transition state intermediates, and the products being difficult to desorb and side reactions occurring, resulting in a low yield of the target product. Therefore, the development of hierarchical pore structure composite molecular sieves suitable for isodewaxing reactions has gradually become a hot topic.

[0004] CN112934258A discloses a composite molecular sieve and its preparation method, a hydroisomerization catalyst, and a method for hydroisomerization of Fischer-Tropsch synthesis oil. The composite molecular sieve has a core-shell structure, and the core-shell structure includes an inner core and an outer shell covering the inner core. The inner core contains a modified ZSM-48 molecular sieve, and the outer shell contains an MCM-41 molecular sieve; based on the total weight of the composite molecular sieve, the content of the outer shell is 0.1 to 50% by weight, and the content of the inner core is 50 to 99.9% by weight. The hydroisomerization catalyst prepared from the composite molecular sieve of the present invention has better isomerization selectivity when used in the hydroisomerization reaction of Fischer-Tropsch synthesis oil, and can produce high-quality and high-yield lubricating oil base oil.

[0005] CN105032478A discloses a catalyst for isomerization and pour point reduction of middle distillates in Fischer-Tropsch synthesis and its dedicated core-shell structured composite molecular sieve. The composite molecular sieve uses microporous ZSM-22 molecular sieve as the core and mesoporous MCM-41 molecular sieve as the shell, and the relative proportion between the two is adjustable. The preparation method is as follows: First, prepare the ZSM-22 molecular sieve, then add an alkali and an organic template agent to the mixed system containing the ZSM-22 molecular sieve for pre-crystallization, and then adjust the pH value to 6.5 - 13.5 for crystallization treatment to obtain the product.

[0006] In the prior art, when an isomerization catalyst using a composite molecular sieve as a carrier is used in the isomerization and pour point reduction process, the performance of the catalyst, especially the selectivity of the target product, needs to be further improved, and the quality of the lubricating oil base oil needs to be enhanced. Summary of the Invention

[0007] During the research process, the inventors found that by increasing the selectivity of distal single-branched chain isomers (the "distal single-branched chain isomers" refer to isomers with a single branch located at the 3rd carbon and above of the carbon chain), especially the isomers with a single branch located at the 4th, 5th carbon and above, it is possible to reduce the pour point of the lubricating oil base oil while minimizing the viscosity index loss to the greatest extent, thereby effectively improving the quality of the lubricating oil base oil.

[0008] Based on the above research results, the present invention provides a core-shell type composite molecular sieve, its preparation method and application. When the catalyst prepared with the composite molecular sieve obtained by the preparation method is applied to the isodewaxing reaction, it can improve the selectivity of distal single-branched chain isomers, and thus significantly improve the quality of the lubricating oil base oil.

[0009] The first aspect of the present invention provides a preparation method of a core-shell type composite molecular sieve, including the following steps: (1) Mix a silicon source, an aluminum source, a template agent, 5A molecular sieve and water to obtain a gel mixture, and then perform aging; the template agent contains hexamethylammonium hydroxide, urea and urease; (2) Hydrothermally crystallize the material obtained by aging in step (1), and obtain the final 5A@ZSM-48 core-shell type composite molecular sieve through washing, drying and calcination.

[0010] In the preparation method of the core-shell type composite molecular sieve of the present invention, in step (1), the silicon source is one or more of silica sol, fumed silica, tetraethyl orthosilicate, and preferably silica sol.

[0011] In the preparation method of the core-shell type composite molecular sieve of the present invention, in step (1), the aluminum source is one or more of aluminum hydroxide, pseudo-boehmite, aluminum isopropoxide, aluminum sulfate, aluminum chloride, and preferably pseudo-boehmite.

[0012] In the preparation method of the core-shell composite molecular sieve of the present invention, in step (1), the calcium content of the 5A molecular sieve is 10 wt% to 18 wt%, and the pore volume is 0.20 cm 3 / g to 0.43 cm 3 / g.

[0013] In the preparation method of the core-shell composite molecular sieve of the present invention, in step (1), urease is a nickel-containing oligopeptidase that can catalyze the hydrolysis of urea to produce ammonia.

[0014] In the preparation method of the core-shell composite molecular sieve of the present invention, in step (1), the molar ratio of the silicon source (calculated as SiO 2 ), the aluminum source (calculated as Al 2 O 3 ), water, hexamethylammonium hydroxide, and urea is 1:(20 - 600):(10 - 60):(0.02 - 0.3):(0.005 - 0.5), preferably 1:(50 - 200):(10 - 60):(0.02 - 0.3):(0.005 - 0.5); the mass ratio of the addition amount of the 5A molecular sieve, the addition amount of urease, and the addition amount of the silicon source (calculated as SiO 2 ) is (0.02 - 1):(0.00015 - 1.8):1, preferably (0.025 - 0.333):(0.0015 - 0.18):1.

[0015] In the preparation method of the core-shell composite molecular sieve of the present invention, in step (1), the aging temperature is 30°C to 70°C, and the aging time is 0.3 h to 12 h, preferably 2 h to 6 h.

[0016] In the preparation method of the core-shell composite molecular sieve of the present invention, in step (2), the hydrothermal crystallization treatment can be carried out by static crystallization or dynamic crystallization, preferably by dynamic crystallization; the hydrothermal crystallization treatment temperature is 150°C to 200°C, and the crystallization time is 10 h to 200 h, preferably 20 h to 100 h.

[0017] In the preparation method of the core-shell composite molecular sieve of the present invention, in step (2), the drying treatment conditions are as follows: the drying temperature is 60°C to 150°C, preferably 80°C to 120°C; the drying time is 2 h to 24 h, preferably 4 h to 12 h.

[0018] In the preparation method of the core-shell composite molecular sieve of the present invention, in step (2), the calcination treatment conditions are as follows: the calcination temperature is 400°C to 650°C, preferably 450°C to 600°C; the calcination time is 2 h to 20 h, preferably 4 h to 8 h.

[0019] The second aspect of the present invention provides the core-shell composite molecular sieve obtained by the above preparation method.

[0020] In the core-shell composite molecular sieve of the present invention, the molecular sieve uses 5A molecular sieve as the core and ZSM-48 molecular sieve as the shell, and the mass ratio of the core to the shell is 1:(1-50), preferably 1:(3-40).

[0021] In the core-shell composite molecular sieve of the present invention, the specific surface area of the molecular sieve is 170 m 2 / g to 600 m 2 / g, and the pore volume is 0.15 cm 3 / g to 0.45 cm 3 / g.

[0022] The third aspect of the present invention provides an isomerization catalyst, and the isomerization catalyst contains the above-mentioned core-shell composite molecular sieve.

[0023] In the isomerization catalyst of the present invention, the isomerization catalyst further contains an active metal component, and the active metal component is selected from Group VIII noble metals Pt and / or Pd, preferably Pt.

[0024] In the isomerization catalyst of the present invention, the isomerization catalyst can be prepared by using the existing catalyst preparation methods in the art. Usually, the catalyst carrier is first prepared, and then the active metal component is further introduced by an impregnation method. The specific catalyst carrier can be obtained by mixing the above-mentioned core-shell composite molecular sieve, alumina, binder, and water and then forming.

[0025] The fourth aspect of the present invention provides the application of the above isomerization catalyst in the isodewaxing process.

[0026] In the application of the present invention, the operating conditions are as follows: the reaction temperature is generally 220°C to 400°C, the reaction pressure is generally 1.0 MPa to 20 MPa, the volume space velocity is generally 0.5 h -1 to 4.0 h -1 , and the hydrogen-oil volume ratio is generally 500:1 to 1400:1.

[0027] Compared with the prior art, the present invention has the following advantages: (1) In the preparation method of the core-shell composite molecular sieve provided by the present invention, 5A molecular sieve is used as the core, and then a mixture of hexamethylammonium hydroxide, urea, and urease is used as a template agent to directly in-situ synthesize hydrogen-type ZSM-48 molecular sieve and wrap it on the surface of 5A molecular sieve. The Ca contained in 5A molecular sieve 2+An electric field will be generated between the negatively charged molecular sieve framework, and under the induced polarization effect generated by the electric field, 5A molecular sieve has a high adsorption selectivity for the olefin intermediate of the isomerization reaction, making it easier for olefins to enter the pores of the shell ZSM-48 molecular sieve. According to the pore mouth key reaction mechanism, the olefin intermediate undergoes an isomerization reaction at the pore mouth, and when the olefin intermediate penetrates into the pores of the shell ZSM-48 molecular sieve, the position where the isomerization reaction occurs at the pore mouth is far from both ends of the carbon chain, thus facilitating the formation of distal branched-chain isomers; moreover, the shell ZSM-48 molecular sieve has a rich mesoporous structure, which is more conducive to the diffusion of product molecules and avoids the occurrence of secondary isomerization reactions, thereby maximizing the retention of distal single-branched chain isomers and improving the quality of lubricating oil base oil.

[0028] (2)In the method for preparing the core-shell composite molecular sieve provided by the present invention, the hydrogen form ZSM-48 molecular sieve is directly synthesized in situ and wrapped on the surface of 5A molecular sieve to obtain the composite molecular sieve, which can omit the ammonium exchange process and avoid the Ca 2+ being exchanged down, affecting the adsorption selectivity of 5A molecular sieve for the olefin intermediate of the isomerization reaction, and further avoiding affecting the catalytic performance of the core-shell composite molecular sieve. Description of the Drawings

[0029] Figure 1 is the XRD pattern of the core-shell composite molecular sieve prepared in Example 2 of the present invention.

[0030] Figure 2 is the SEM characterization result of the core-shell composite molecular sieve prepared in Example 2 of the present invention.

[0031] Figure 3 is the TEM characterization result of the core-shell composite molecular sieve prepared in Example 2 of the present invention. Embodiments

[0032] The following examples are used to further illustrate the functions and effects of the method of the present invention, but the following examples do not limit the method of the present invention. The endpoints and any values of the disclosed ranges are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values and individual point values of each range, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. The contents in the following examples are weight percentages unless otherwise specified.

[0033] In the present invention, a D / max-2500 type full-automatic rotating target X-ray diffractometer was used to characterize the crystal phase structure of the samples of the present invention, an ASAP 2460 was used to characterize the specific surface area and pore volume of the samples, a Zeiss Supra 55 scanning electron microscope was used to characterize the structural morphology of the samples, and a FEI TECNAI20 transmission electron microscope was used to characterize the structural morphology of the samples.

[0034] In the examples and comparative examples of the present invention, the urease used was purchased from Sigma-Aldrich, CAS No.: 9002-13-5.

[0035] Example 1 0.72 g of urea, 56.7 g of hexamethylammonium hydroxide solution (mass fraction 25%), 120 g of silica sol (mass fraction 30%), 1.22 g of pseudoboehmite, 143.4 g of water, 0.27 g of urease and 1.89 g of 5A molecular sieve were mixed evenly and loaded into a crystallization kettle. After aging at 60 °C for 2 h, the temperature was raised to 190 °C for hydrothermal crystallization for 20 h. After the crystallization was completed, the product obtained by crystallization was washed, then dried at 110 °C for 4 h, and then calcined at 500 °C for 5 h to obtain the molecular sieve composite ZA-1, whose specific surface area was 215 m 2 / g, the pore volume was 0.26 mL / g, and the mass ratio of 5A molecular sieve to ZSM-48 molecular sieve was 1:19.

[0036] 140 g of the above-prepared molecular sieve composite ZA-1 (dry basis, the same below) and 50 g of alumina (dry basis) were fully mixed evenly, 2 mL of concentrated nitric acid (mass fraction 65%) and an appropriate amount of water were added, and they were fully kneaded and then extruded into pellets. Then, the noble metal Pt was impregnated by the saturated impregnation method, and the Pt loading was 0.39 wt% of the mass of the carrier. After drying at 100 °C for 4 h and calcining at 500 °C for 3 h, the catalyst C1 of the present invention was obtained, whose specific surface area was 197 m 2 / g, and the pore volume was 0.31 mL / g.

[0037] Example 2 0.18 g of urea, 170.2 g of hexamethylammonium hydroxide solution (mass fraction 25%), 120 g of silica sol (mass fraction 30%), 0.49 g of pseudoboehmite, 252.7 g of water, 0.23 g of urease and 5.86 g of 5A molecular sieve were mixed evenly and loaded into a crystallization kettle. After aging at 40 °C for 3 h, the temperature was raised to 185 °C for hydrothermal crystallization for 24 h. After the crystallization was completed, the product obtained by crystallization was washed, then dried at 110 °C for 4 h, and then calcined at 520 °C for 3 h to obtain the molecular sieve composite ZA-2, whose specific surface area was 275 m 2 / g, the pore volume is 0.28 mL / g, and the mass ratio of 5A molecular sieve to ZSM-48 molecular sieve is 1:6.

[0038] The catalyst was prepared using the molecular sieve composite ZA-2. The catalyst preparation method was the same as in Example 1. The Pt loading was 0.35 wt% of the mass of the support. The catalyst was numbered C2, and its specific surface area was 256 m 2 / g, and the pore volume was 0.33 mL / g.

[0039] Example 3 5.41 g of urea, 85.1 g of hexamethylammonium hydroxide solution (mass fraction 25%), 120 g of silica sol (mass fraction 30%), 0.73 g of pseudoboehmite, 122.2 g of water, 1.03 g of urease, and 3.13 g of 5A molecular sieve were mixed evenly and loaded into a crystallization kettle. After aging at 50 °C for 2.5 h, the temperature was raised to 180 °C for hydrothermal crystallization for 30 h. After crystallization was completed, the product obtained by crystallization was washed, then dried at 100 °C for 4 h, and then calcined at 550 °C for 3 h to obtain the molecular sieve composite ZA-3, whose specific surface area was 234 m 2 / g, the pore volume was 0.29 mL / g, and the mass ratio of 5A molecular sieve to ZSM-48 molecular sieve was 1:12.

[0040] The catalyst was prepared using the molecular sieve composite ZA-3. The catalyst preparation method was the same as in Example 1. The Pt loading was 0.40 wt% of the mass of the support. The catalyst was numbered C3, and its specific surface area was 215 m 2 / g, and the pore volume was 0.34 mL / g.

[0041] Example 4 18.02 g of urea, 11.3 g of hexamethylammonium hydroxide solution (mass fraction 25%), 120 g of silica sol (mass fraction 30%), 0.47 g of aluminum hydroxide, 555.5 g of water, 6.48 g of urease, and 12 g of 5A molecular sieve were mixed evenly and loaded into a crystallization kettle. After aging at 70 °C for 2 h, the temperature was raised to 170 °C for hydrothermal crystallization for 48 h. After crystallization was completed, the product obtained by crystallization was washed, then dried at 100 °C for 4 h, and then calcined at 520 °C for 4 h to obtain the molecular sieve composite ZA-4, whose specific surface area was 353 m 2 / g, the pore volume was 0.34 mL / g, and the mass ratio of 5A molecular sieve to ZSM-48 molecular sieve was 1:3.

[0042] The catalyst was prepared using the molecular sieve composite ZA-4. The catalyst preparation method was the same as in Example 1. The Pt loading was 0.48 wt% of the mass of the support. The catalyst was numbered C4, and its specific surface area was 323 m 2 / g, and the pore volume was 0.41 mL / g.

[0043] Example 5 2.88 g of urea, 45.4 g of hexamethylammonium hydroxide solution (mass fraction 25%), 36.05 g of silica white, 0.61 g of pseudo-boehmite, 74.0 g of water, 0.16 g of urease and 0.90 g of 5A molecular sieve were mixed evenly and loaded into a crystallization kettle. After aging at 30 °C for 4 h, the temperature was raised to 175 °C for hydrothermal crystallization for 36 h. After the crystallization was completed, the product obtained by crystallization was washed, then dried at 100 °C for 4 h, and then calcined at 550 °C for 3 h to obtain the molecular sieve composite ZA-5, with a specific surface area of 337 m 2 / g, pore volume of 0.33 mL / g, and the mass ratio of 5A molecular sieve to ZSM-48 molecular sieve was 1:40.

[0044] The catalyst was prepared using the molecular sieve composite ZA-5. The catalyst preparation method was the same as in Example 1, with a Pt loading of 0.27 wt% of the carrier mass. The catalyst was numbered C5, with a specific surface area of 303 m 2 / g and a pore volume of 0.39 mL / g.

[0045] Comparative Example 1 21.9 g of ZSM-48 molecular sieve (silica-alumina ratio 100), 8.1 g of 5A molecular sieve, and 10 g of pseudo-boehmite (dry basis) were thoroughly mixed evenly. 0.4 mL of concentrated nitric acid (mass fraction 65%) and an appropriate amount of water were added, and after thorough kneading, it was extruded into shape. The catalyst preparation method was the same as in Example 1, with a Pt loading of 0.23 wt% of the carrier. The catalyst was numbered D1, with a specific surface area of 296 m 2 / g and a pore volume of 0.35 mL / g.

[0046] Comparative Example 2 The preparation process of the comparative catalyst D2 of the present invention was the same as in Example 4, except that urease was not added during the molecular sieve synthesis process, and the mass ratio of 5A molecular sieve to ZSM-48 molecular sieve was 1:2.8. The specific surface area of catalyst D2 was 336 m 2 / g and a pore volume of 0.40 mL / g.

[0047] Example 6 n-Dodecane was used as a model compound to evaluate the reaction performance of the catalyst. Before feeding, the catalyst was pre-reduced to convert the noble metal on the catalyst into the reduced state. The reduction conditions were as follows: reduction was carried out at a temperature of 400 °C and a pressure of 2 MPa for 5 hours in the presence of hydrogen; the evaluation reaction conditions were as follows: reaction pressure 3 MPa, volume space velocity 1 h -1 , hydrogen-oil volume ratio 800:1, and the evaluation results are shown in Table 1.

[0048] Table 1 Evaluation Results

[0049] Example 7 The hydrocracked tail oil (properties are shown in Table 2) was used as the raw material to further evaluate the reaction performance of the catalyst. Before feeding, the catalyst was pre-reduced to convert the noble metal on the catalyst into the reduced state. The reduction conditions were as follows: reduction was carried out at a temperature of 400 °C and a pressure of 10 MPa in the presence of hydrogen for 6 hours; the evaluation reaction conditions were as follows: reaction pressure 14 MPa, volume space velocity 0.8 h -1 , hydrogen-oil volume ratio 800:1, reaction temperature 325 °C, and the evaluation results are shown in Table 3.

[0050] Table 2 Properties of the raw material

[0051] Table 3 Evaluation results of the catalyst performance

[0052] It can be seen from the catalyst evaluation results that increasing the selectivity of the distal single-branched chain isomers can reduce the pour point of the lubricating oil base oil while minimizing the viscosity index loss to the greatest extent, thereby effectively improving the quality of the lubricating oil base oil.

Claims

1. A preparation method of a core-shell composite molecular sieve, characterized in that: comprises the following steps: (1) Mix a silicon source, an aluminum source, a template agent, 5A molecular sieve and water to obtain a gel mixture, and then age it; the template agent contains hexamethylammonium hydroxide, urea and urease; (2) Hydrothermally crystallize the material obtained by aging in step (1), and obtain the final 5A@ZSM-48 core-shell composite molecular sieve through washing, drying and calcination.

2. The preparation method according to claim 1, characterized in that: in step (1), the silicon source is one or more of silica sol, white carbon black, tetraethyl orthosilicate, preferably silica sol.

3. The preparation method according to claim 1, characterized in that: in step (1), the aluminum source is one or more of aluminum hydroxide, pseudo-boehmite, aluminum isopropoxide, aluminum sulfate, aluminum chloride, preferably pseudo-boehmite.

4. The preparation method according to claim 1, characterized in that: In step (1), the calcium content of the 5A molecular sieve is 10 wt% to 18 wt%, and the pore volume is 0.20 cm 3 / g to 0.43 cm 3 / g.

5. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of the silicon source (calculated as SiO 2 , the aluminum source (calculated as Al 2 O 3 ), water, hexamethylammonium hydroxide, and urea is 1:(20 - 600):(10 - 60):(0.02 - 0.3):(0.005 - 0.5), preferably 1:(50 - 200):(10 - 60):(0.02 - 0.3):(0.005 - 0.5); the mass ratio of the addition amount of the 5A molecular sieve, the addition amount of urease, and the addition amount of the silicon source (calculated as SiO 2 ) is (0.02 - 1):(0.00015 - 1.8):1, preferably (0.025 - 0.333):(0.0015 - 0.18):

1.

6. The preparation method according to claim 1, characterized in that: in step (1), the aging temperature is 30°C to 70°C, and the aging time is 0.3 h to 12 h, preferably 2 h to 6 h.

7. The preparation method according to claim 1, characterized in that: in step (2), the hydrothermal crystallization treatment adopts static crystallization or dynamic crystallization, preferably dynamic crystallization; the hydrothermal crystallization treatment temperature is 150°C to 200°C, and the crystallization time is 10 h to 200 h, preferably 20 h to 100 h.

8. The preparation method according to claim 1, characterized in that: in step (2), the drying treatment conditions are as follows: the drying temperature is 60°C to 150°C, preferably 80°C to 120°C; the drying time is 2 h to 24 h, preferably 4 h to 12 h.

9. The preparation method according to claim 1, characterized in that: in step (2), the calcination treatment conditions are as follows: the calcination temperature is 400°C to 650°C, preferably 450°C to 600°C; the calcination time is 2 h to 20 h, preferably 4 h to 8 h.

10. The core-shell composite molecular sieve obtained by the preparation method according to any one of claims 1-9.

11. The core-shell composite molecular sieve according to claim 10, characterized in that: the molecular sieve uses 5A molecular sieve as the core and ZSM-48 molecular sieve as the shell, and the core-shell mass ratio is 1:(1-50), preferably 1:(3-40).

12. The core-shell composite molecular sieve according to claim 10, characterized in that: The specific surface area of the molecular sieve is 170 m 2 / g to 600 m 2 / g, and the pore volume is 0.15 cm 3 / g to 0.45 cm 3 / g.

13. An isomerization catalyst, the isomerization catalyst contains the core-shell composite molecular sieve according to any one of claims 10-12.

14. Application of the isomerization catalyst according to claim 13 in the isodewaxing treatment process.

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