阅读说明：本技术 一种双功能分子筛催化剂的制备方法及应用 (Preparation method and application of bifunctional molecular sieve catalyst ) 是由 李久盛 谭阳春 廖廷君 赵永清 朱德林 杜燕燕 陈伟 倪杰 赵恩军 于 2021-08-18 设计创作，主要内容包括：本发明属于分子筛催化剂技术领域,公开了一种双功能分子筛催化剂的制备方法及应用。本发明通过将金属源与分子筛合成原料干剂混合研磨后结晶,一步合成金属@分子筛型双功能分子筛催化剂。在对正构烷烃的加氢异构化反应中,该方法制备的催化剂与传统水热后浸渍法得到的催化剂相比,具有更好的异构体选择性和稳定性,最高异构体收率达80%,催化性能可媲美前负载方法得到的催化剂。本发明的双功能分子筛催化剂制备过程简单,无需对金属源进行任何前处理和引入任何溶剂,可降低生产成本和环境污染,实现加氢异构催化剂的低成本化和可持续化。(The invention belongs to the technical field of molecular sieve catalysts, and discloses a preparation method and application of a bifunctional molecular sieve catalyst. The metal @ molecular sieve type bifunctional molecular sieve catalyst is synthesized in one step by mixing and grinding a metal source and a molecular sieve synthesis raw material dry agent and then crystallizing. In the hydroisomerization reaction of normal paraffin, compared with the catalyst obtained by the traditional hydrothermal post-impregnation method, the catalyst prepared by the method has better isomer selectivity and stability, the highest isomer yield reaches 80%, and the catalytic performance can be comparable to that of the catalyst obtained by the pre-loading method. The preparation process of the bifunctional molecular sieve catalyst is simple, any pretreatment of a metal source and any solvent introduction are not needed, the production cost and the environmental pollution can be reduced, and the cost reduction and the sustainability of the hydroisomerization catalyst are realized.)

1. A method for preparing a bifunctional molecular sieve catalyst, the method comprising the steps of:

mixing and grinding a metal salt drying agent and a molecular sieve synthesis raw material aluminum source, a silicon source and a phosphorus source template complexing agent according to a certain proportion, and transferring to a reaction kettle for carrying out an eutectic reaction; and

and (3) centrifugally washing, drying and calcining the product subjected to crystallization reaction to obtain the bifunctional molecular sieve catalyst.

2. The preparation method according to claim 1, wherein the metal in the metal salt dry agent is selected from any one or more of platinum, palladium and nickel; the metal content in the metal salt drying agent is 20-70 wt%.

3. The process of claim 1 or 2, wherein the bifunctional molecular sieve catalyst has a metal loading of 0.05 to 0.9 wt%.

4. The method according to claim 1, wherein the metal salt dry agent, the aluminum source, the silicon source and the phosphorus source template complexing agent are present in a mass ratio of (0.001-0.01): 1.0: (0.05-0.5): (1.0-2.0).

5. The preparation method according to claim 1 or 4, wherein the aluminum source is selected from any one or more of pseudoboehmite, sodium metaaluminate, gamma-alumina and aluminum potassium sulfate; the silicon source is selected from any one or more of sodium silicate, potassium silicate and gas-phase silicon dioxide; the phosphorus source template complexing agent is selected from any one or more of di-n-propylamine phosphate, ethylenediamine phosphate, n-butylamine phosphite and propionamide phosphite.

6. The method as claimed in claim 1, wherein the temperature of the co-crystallization reaction is 120-220 ℃, and the reaction time is 18-48 h; the solvent for washing is ethanol and deionized water.

7. The method of claim 1, wherein the drying temperature is 80 ℃; the calcining atmosphere is air, and the calcining temperature is 500-650 ℃.

8. A bifunctional molecular sieve catalyst obtainable by the process according to any one of claims 1 to 7.

9. Use of the bifunctional molecular sieve catalyst of claim 8 in a hydroisomerization reaction of long chain alkanes.

10. The use of claim 9, wherein the long chain alkane has a carbon number between 10 and 30.

Technical Field

The invention belongs to the technical field of molecular sieve catalysts, and particularly relates to a preparation method and application of a bifunctional molecular sieve catalyst.

Background

The Fischer-Tropsch synthesis is a technical route for indirect coal liquefaction and is also an important means for producing high-added-value products in the modern coal chemical industry. The market demand for the main product fischer-tropsch wax (with n-alkane content up to 95%) is limited, resulting in excess capacity. The hydroisomerization process can convert Fischer-Tropsch wax into a low-freezing-point oil phase mixture, can be used as high-quality lubricating oil base oil and diesel oil with excellent low-temperature performance, and realizes high-value utilization of coal resources. However, the lack of a highly efficient bifunctional catalyst has limited the development of hydroisomerization reactions.

The preparation of bifunctional catalysts is the core technology of long paraffin isomerization reactions. According to the classical bifunctional theory, in the hydroisomerization reaction, the hydrogenation-dehydrogenation reaction occurs at the metal site, and the carbocation rearrangement process occurs at the acid site. Therefore, the bifunctional catalyst is composed of metal and acidic carrier, and has wide application in chemical industry. The common synthesis process of the bifunctional catalyst firstly needs to synthesize an acidic molecular sieve by a hydrothermal method, then immerse a metal solution on the acidic molecular sieve, and finally achieve the purpose of attaching metal particles on the surface of the molecular sieve by means of high-temperature calcination. Besides, the acidic molecular sieve is synthesized by microwave method, solvent-free method, etc., and the metal sites are loaded by vacuum-assisted method, vapor deposition method, etc. It can be seen that the preparation of the molecular sieve and the loading of the metal are often carried out step by step, and the synthesis route of the bifunctional catalyst is complicated to operate. In the experimental research stage, a metal pre-loading method (application number: 201910305683.4) is also provided, wherein a metal solution is firstly soaked on an aluminum source and a silicon source which are synthesis raw materials of the molecular sieve to prepare a metal @ aluminum/silicon precursor, and then the metal @ aluminum/silicon precursor reacts with other raw materials to synthesize the acidic molecular sieve, so that the purpose of loading metal sites firstly and then forming the acidic sites is achieved. The pre-loading method can further simplify the synthesis steps, and the obtained catalyst has excellent performance, but the stability of the catalyst is insufficient due to the influence of the metal @ aluminum/silicon precursor in the molecular sieve crystallization process. Although the technical field of molecular sieve catalysts has been developed for many years, and large-scale industrial production technology tends to be mature, the simplification of the synthesis process of the bifunctional catalyst, the promotion of the catalytic performance and the stability of the molecular sieve framework structure still remain the industrial problems to be solved.

Disclosure of Invention

In order to solve the problems in the background art, the invention aims to provide a preparation method for synthesizing a bifunctional molecular sieve catalyst by solid-phase cocrystallization. Compared with the traditional method for synthesizing metal sites and acid sites step by step, the solid-phase co-crystallization method related by the invention can form the dual-functional sites on the dual-functional molecular sieve catalyst simultaneously by one step, and can greatly reduce the loss of raw materials. Compared with the prior loading method which damages the catalyst structure, the method improves the catalytic performance and keeps the stability of the catalyst structure. The method of the invention does not need any pretreatment on the metal source and any solvent, can reduce the production cost and environmental pollution, and promotes the low cost and sustainability of the hydroisomerization catalyst.

In order to achieve the above object, the first technical solution adopted by the present invention is:

a preparation method and application of a bifunctional molecular sieve catalyst comprise the following steps:

mixing and grinding a metal salt drying agent and a molecular sieve synthesis raw material aluminum source, a silicon source and a phosphorus source template complexing agent according to a certain proportion, and transferring to a reaction kettle for carrying out an eutectic reaction; and

and (3) centrifugally washing, drying and calcining the product subjected to crystallization reaction to obtain the bifunctional molecular sieve catalyst.

Further, the metal in the metal salt dry agent is selected from any one or more of platinum, palladium and nickel; the metal content in the metal salt drying agent is 20-70 wt%, and preferably 20-60 wt%.

Further, the metal loading in the bifunctional molecular sieve catalyst is 0.05-0.9 wt%, preferably 0.1-0.6 wt%.

Further, the mass ratio of the metal salt dry agent, the aluminum source, the silicon source and the phosphorus source template complexing agent is (0.001-0.01): 1.0: (0.05-0.5): (1.0-2.0).

Further, the aluminum source is selected from any one or more of pseudo-boehmite, sodium metaaluminate, gamma-alumina and aluminum potassium sulfate; the silicon source is selected from any one or more of sodium silicate, potassium silicate and gas-phase silicon dioxide; the phosphorus source template complexing agent is selected from any one or more of di-n-propylamine phosphate, ethylenediamine phosphate, n-butylamine phosphite and propionamide phosphite.

Further, the temperature of the co-crystallization reaction is 120-220 ℃, and the reaction time is 18-48 h; the solvent for washing is ethanol and deionized water.

Further, the drying temperature is 80 ℃; the calcining atmosphere is air, and the calcining temperature is 500-650 ℃.

The second technical scheme adopted by the invention is as follows:

a bifunctional molecular sieve catalyst obtained by the preparation method of the first technical scheme.

The third technical scheme adopted by the invention is as follows:

the application of the bifunctional molecular sieve catalyst in the second technical scheme in the hydroisomerization reaction of long-chain alkane.

Further, the long-chain alkane has a carbon number between 10 and 30; preferably, the long chain alkane has a carbon number between 12 and 20.

Compared with the prior art, the invention has the following beneficial effects:

1. compared with the step-by-step synthesis of the bifunctional molecular sieve catalyst adopted by other strategies in the prior art, the method adopts a solid-phase co-crystallization method to simultaneously form the bifunctional sites on the bifunctional molecular sieve catalyst by one step, and can greatly reduce the production cost. The prepared catalyst is used for the hydroisomerization reaction of long-chain alkane, and the overall yield of isoparaffin is up to 80%, at the moment, the yield of single-chain alkane is 50%, and the yield of multi-chain isomer is 30%. Compared with the catalyst obtained by the traditional hydrothermal post-impregnation method, the catalyst prepared by the method has better isomer selectivity and yield, the content of the multi-branched isomer in the product is increased from 22% to 30%, and the pour point of the lube base oil is further reduced.

2. The catalyst prepared by the method disclosed by the invention has the advantages that the catalytic performance is improved, the stability of the catalyst structure is kept, and the catalytic performance is comparable to that of the catalyst obtained by the pre-loading method.

3. The bifunctional molecular sieve catalyst has wide raw material sources, further simplifies the synthesis steps, and can solve the problems of complex preparation process and unstable molecular sieve structure in the prior art. The method does not need to carry out any pretreatment on the metal source and introduce any solvent, can reduce the production cost and environmental pollution, and promotes the low cost and the sustainability of the hydroisomerization catalyst.

Drawings

FIG. 1 is an XRD spectrum of each of the catalysts synthesized in examples 1 and 2 of the present invention and comparative examples 1 and 2;

FIG. 2 is a graph showing the liquid yield of hydroisomerization reaction for n-dodecane according to the present invention for each catalyst synthesized in examples 1 and 2 and comparative examples 1 and 2, respectively, as a function of the conversion rate;

FIG. 3 is a graph showing the temperature dependence of the conversion of each of the catalysts synthesized in examples 1 and 2 of the present invention and comparative examples 1 and 2, respectively, in n-dodecane hydroisomerization;

FIG. 4 is a graph of the product selectivity of each of the catalysts synthesized in examples 1 and 2 of the present invention and comparative examples 1 and 2, respectively, for n-dodecane hydroisomerization versus conversion;

FIG. 5 is a graph showing the yield of products of the hydroisomerization reaction for n-dodecane as a function of conversion for each of the catalysts synthesized in examples 1 and 2 of the present invention and comparative examples 1 and 2, respectively;

FIG. 6 is a bar graph showing the product distribution of the hydroisomerization reaction for n-dodecane as a function of temperature for the catalysts synthesized in examples 1 and 2 of the present invention and comparative examples 1 and 2, respectively.

Detailed Description

The present invention is described in detail below with reference to the drawings and examples, and it should be noted that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention. The invention is susceptible to numerous insubstantial modifications and adaptations by those skilled in the art in view of the foregoing disclosure.

Before carrying out the examples, the curing treatment of the template, i.e. the preparation of the phosphorus source template complex agent, is completed. The template agent is selected from di-n-propylamine (DPA), and the DPA is reacted with the raw material phosphoric acid for synthesizing the molecular sieve to form di-n-propylamine phosphate (DPA. H) before the reaction₃PO₄) Powders, DPA and H₃PO₄The reaction molar ratio of (A) is 1:1.0-1: 1.5. In addition, the reagents and materials used below were all commercial products unless otherwise specified.

Example 1

0.06 g of H having a platinum content of 37.5% by weight are initially introduced₂PtCl₆·6H₂O drier, 0.25 g fumed silica, 2.912 g pseudoboehmite, 6.28 g DPA. H₃PO₄Mixing and grinding for 8 min, then transferring to a reaction kettle for 24 h at 200 ℃ for co-crystallization, centrifugally washing the crystallized product after reaction, drying at 80 ℃ and roasting at 600 ℃ in air atmosphere for 6 h to obtain the final bifunctional catalyst. The sample prepared above was tested using plasma emission spectroscopy (ICP) to determine the metal loading to be 0.4 wt%.

Example 2

0.05 g of (NH) containing 44.0 wt.% of platinum₄)₂PtCl₆The dry agent was mixed with 0.25 g fumed silica, 2.912 g pseudoboehmite, 6.28 g DPA. H₃PO₄Mixing and grinding for 8 min, then transferring to a reaction kettle for cocrystallization at 200 ℃ for 24 h, centrifugally washing a crystallized product after reaction, drying at 80 ℃ and roasting at 600 ℃ in an air atmosphere for 6 h to obtain the final bifunctional molecular sieve catalyst. The sample prepared above was tested by ICP to determine the metal loading to be 0.4 wt%.

Example 3

First 0.04 g of Pt (NH) containing 58.0 wt% of platinum₃)₄Cl₂The dry agent was mixed with 0.25 g fumed silica, 2.912 g pseudoboehmite, 6.28 g DPA. H₃PO₄Mixing and grinding for 8 min, then transferring to a reaction kettle for cocrystallization at 200 ℃ for 24 h, centrifugally washing a crystallized product after reaction, drying at 80 ℃ and roasting at 600 ℃ in an air atmosphere for 6 h to obtain the final bifunctional molecular sieve catalyst. The sample prepared above was tested by ICP to determine the metal loading to be 0.4 wt%.

Example 4

First 0.06 g of Pd (NH) containing 35.5 wt.% of palladium₃)₄(NO₃)₂The dry agent was mixed with 0.25 g fumed silica, 2.912 g pseudoboehmite, 6.28 g DPA. H₃PO₄Mixing and grinding for 8 min, then transferring to a reaction kettle for cocrystallization at 200 ℃ for 24 h, centrifugally washing a crystallized product after reaction, drying at 80 ℃ and roasting at 600 ℃ in an air atmosphere for 6 h to obtain the final bifunctional molecular sieve catalyst. The sample prepared above was tested by ICP to determine the metal loading to be 0.4 wt%.

Example 5

First 0.11 g of Ni (NO) containing 20.0 wt% of nickel₃)₂·6H₂O drier, 0.25 g fumed silica, 2.912 g pseudoboehmite, 6.28 g DPA. H₃PO₄Mixing and grinding for 8 min, then transferring to a reaction kettle for co-crystallization for 24 h at 200 ℃, centrifugally washing the crystallized product after reaction, and finally, adding the obtained productDrying at the temperature of 80 ℃ and roasting for 6 hours at the temperature of 600 ℃ in an air atmosphere to obtain the final bifunctional molecular sieve catalyst. The sample prepared above was tested by ICP to determine the metal loading to be 0.4 wt%.

Example 6

0.015 g of H having a platinum content of 37.5% by weight₂PtCl₆·6H₂O drier, 0.25 g fumed silica, 2.912 g pseudoboehmite, 6.28 g DPA. H₃PO₄Mixing and grinding for 8 min, then transferring to a reaction kettle for cocrystallization at 200 ℃ for 24 h, centrifugally washing a crystallized product after reaction, drying at 80 ℃ and roasting at 600 ℃ in an air atmosphere for 6 h to obtain the final bifunctional molecular sieve catalyst. The sample prepared above was tested by ICP to determine the metal loading to be 0.1 wt%.

Example 7

0.09 g of H having a platinum content of 37.5% by weight₂PtCl₆·6H₂O drier, 0.25 g fumed silica, 2.912 g pseudoboehmite, 6.28 g DPA. H₃PO₄Mixing and grinding for 8 min, then transferring to a reaction kettle for cocrystallization at 200 ℃ for 24 h, centrifugally washing a crystallized product after reaction, drying at 80 ℃ and roasting at 600 ℃ in an air atmosphere for 6 h to obtain the final bifunctional molecular sieve catalyst. The sample prepared above was tested by ICP to determine the metal loading to be 0.6 wt%.

Comparative example 1

First by mixing the components in a molar ratio of 1.2 DPA: 1.0 Al₂O₃：1.0 P₂O₅：0.3 SiO₂：120 H₂And (3) forming a gel hydrothermal synthesis molecular sieve carrier by using O. 12.4 g of phosphoric acid (85 wt%) was dissolved in 116 g of deionized water with stirring, and then 7.21 g of pseudoboehmite (75 wt% Al)₂O₃) Slowly adding the mixture, and stirring the obtained mixture for 2 hours; 3.39 g tetraethyl orthosilicate (99% TEOS) was added slowly and stirred for 2 h. 6.58 g DPA (99 wt.%) were added to the above mixture and stirred for 2 h. Finally, the homogeneous gel obtained is crystallized in a stainless steel autoclave with a polytetrafluoroethylene lining at 185 ℃ for 48 h, the product obtained is washed centrifugally, dried at 100 ℃ for 3 h,and roasting the mixture for 5 hours at the temperature of 600 ℃ in an air atmosphere to obtain the hydrothermal molecular sieve S11.

With 5.0 mL of H having a concentration of 0.0244 mol/L₂PtCl₆The solution impregnated 6.0 g S11 powder was maintained at room temperature for 24 h, then dried at 80 ℃ and calcined in an air atmosphere at 480 ℃ for 4 h to give the final catalyst product. The sample prepared above was tested by ICP to determine the metal loading to be 0.4 wt%.

Comparative example 2

First, 1.3 mL of H with a concentration of 0.133 mol/L was used₂PtCl₆0.25 g of fumed silica is soaked in the solution, the room temperature is maintained for 24 hours, and then the platinum-silicon precursor is obtained by drying at the temperature of 80 ℃ and roasting at the temperature of 480 ℃ in the air atmosphere for 4 hours. The precursor was mixed with 2.912 g of pseudoboehmite and 6.28 g of DPA. H₃PO₄Mixing and grinding for 8 min, then transferring to a reaction kettle for cocrystallization at 200 ℃ for 24 h, centrifugally washing a crystallized product after reaction, drying at 80 ℃ and roasting at 600 ℃ in an air atmosphere for 6 h to obtain the final product. The sample prepared above was tested by ICP to determine the metal loading to be 0.4 wt%.

Comparative example 3

Firstly, 2.0 mL of H with the concentration of 0.0665 mol/L is used₂PtCl₆2.912 g of pseudo-boehmite powder is soaked in the solution, the room temperature is maintained for 24 h, and then the solution is dried at the temperature of 80 ℃ and roasted at the temperature of 480 ℃ for 4 h in an air atmosphere to obtain a platinum-aluminum precursor. The precursor was mixed with 0.25 g of fumed silica and 6.28 g of DPA. H₃PO₄Mixing and grinding for 8 min, then transferring to a reaction kettle for cocrystallization at 200 ℃ for 24 h, centrifugally washing a crystallized product after reaction, drying at 80 ℃ and roasting at 600 ℃ in an air atmosphere for 6 h to obtain the final product. The sample prepared above was tested by ICP to determine the metal loading to be 0.4 wt%.

Referring to fig. 1, there is shown XRD spectra of each of the catalysts synthesized in examples 1 and 2 and comparative examples 1 and 2. As can be seen from FIG. 1, the catalysts obtained in examples 1 and 2 and comparative examples 1 and 2 all exhibited a SAPO-11 crystal phase of a typical AEL structure. Of these, the sample of comparative example 1 was prepared by a conventional hydrothermal method and its crystallinity was superior to the solid phase co-crystallization and metal pre-loading solvent-free methods involved in the present invention. In particular, the crystallinity of the catalyst in comparative example 2 is greatly affected, probably because the reduction of the framework silicon atoms of the molecular sieve is caused by loading the silicon source before the metal, and the acid sites of the carrier molecular sieve related to the invention are derived from isomorphous substitution of the framework silicon atoms for aluminum atoms and phosphorus atoms. It can be seen that the solid-phase co-crystallization method of the embodiment of the invention has the catalyst performance which is comparable to that of the pre-metal loading method, and simultaneously well maintains the structural stability of the molecular sieve. In addition, due to the different synthesis steps of the hydrothermal method and the solid phase method, a distinct metallic platinum crystalline phase in the example sample can be observed, indicating that platinum nanoparticles with higher crystallinity are present in the example sample.

Examples of the experiments

The catalyst samples prepared in examples 1 and 2 and comparative examples 1 and 2 were subjected to a hydroisomerization reaction of n-dodecane. The reaction conditions are as follows: 4.5 MPa, WHSV 1.5 h^-1，nH₂:nC₁₂The hydroisomerization activity, product selectivity and product yield of the catalyst were evaluated at a temperature range of 280 ℃ and 400 ℃.

Referring to FIG. 2, the liquid yield of the hydroisomerization reaction for n-dodecane according to the present invention is shown as a function of the conversion rate for each of the catalysts synthesized in examples 1 and 2 and comparative examples 1 and 2. The experimental results show that the liquid yield of the catalyst prepared in comparative example 1 by the hydrothermal method is obviously lower than that of the catalyst prepared by the solid-phase co-crystallization method and the metal pre-loading method, and that the gaseous products generated by cracking are less.

Referring to FIG. 3, the curves of the conversion rate of each catalyst synthesized in examples 1 and 2 and comparative examples 1 and 2 of the present invention in n-dodecane hydroisomerization reaction, respectively, are shown as a function of temperature. The experimental results show that the reactivity is as compared with comparative example 1, comparative example 2 and example 2. The reaction activity is positively correlated with the crystallinity of the molecular sieve. The possible reasons for this analysis are: in the operation process of the solid-phase co-crystallization method and the metal pre-loading method, the metal source and a raw material dry agent of the molecular sieve participate in the crystallization process together, so that part of metal nano particles are embedded in the molecular sieve crystals, the pore channels of the molecular sieve are distorted, the acidity is reduced, the activity of the catalyst is reduced, and the conversion rate is reduced.

Referring to fig. 4 and 5, the product selectivity and yield versus conversion for n-dodecane hydroisomerization for each of the catalysts synthesized in examples 1 and 2 of the present invention and comparative examples 1 and 2, respectively, are shown. Experimental results show isomer selectivity and isomer yield example 1= example 2= comparative example 2> comparative example 1. For the catalyst of example 1, when the maximum isomer yield of 80% (50% single branched isomer, 30% multi branched isomer) was reached, the reaction temperature was 355 ℃, the liquid product yield was 94%, the reactant conversion was 89%, the isomer selectivity was 89%, the liquid cracked product selectivity was 5.4%, and the liquid cracked product yield was 4.8%; for the catalyst of example 2, when the maximum isomer yield of 80% (single branched isomer 46%, multi branched isomer 34%) was reached, the reaction temperature was 370 ℃, the liquid product yield was 96%, the reactant conversion rate was 92%, the isomer selectivity was 87%, the liquid cracked product selectivity was 9.8%, and the liquid cracked product yield was 9.0%; for the catalyst of comparative example 1, when the maximum isomer yield of 67% (single branched isomer 45%, multi branched isomer 22%) was reached, the reaction temperature was 340 ℃, the liquid product yield was 87%, the reactant conversion was 90%, the isomer selectivity was 74%, the liquid cracked product selectivity was 11.0%, and the liquid cracked product yield was 9.9%. For the catalyst of comparative example 2, when the maximum isomer yield of 78% (single branched isomer 40%, multi branched isomer 38%) was reached, the reaction temperature was 355 ℃, the liquid product yield was 98%, the reactant conversion was 87%, the isomer selectivity was 90%, the liquid cracked product selectivity was 7.0%, and the liquid cracked product yield was 6.0%. The catalysts of examples 1-2 and comparative example 2 are superior to the catalyst of comparative example 1 synthesized by the conventional hydrothermal method, indicating that the catalyst performance obtained by the conventional method still has the need of further improvement. Therefore, the bifunctional molecular sieve catalyst synthesized by solid-phase cocrystallization shows the best catalytic performance for the hydroisomerization reaction of n-dodecane, the catalytic performance is comparable to that of a catalyst prepared by a pre-metal loading method, and meanwhile, good structural stability is kept. The maximum isomer yield is about 13% higher than that of a hydrothermal catalyst, and the selectivity of the multi-branched isomer is obviously improved, so that the method is more favorable for high-value utilization of product oil.

Referring to FIG. 6, a bar graph of the product distribution of the hydroisomerization reaction for n-dodecane over temperature for each of the catalysts synthesized in examples 1 and 2 of the present invention and comparative examples 1 and 2, respectively, is shown. The results show that the example catalysts are capable of significantly reducing the cracking components in the liquid product. This means that the selectivity of the isomers is greatly increased and the reaction tends towards the direction of isomerization rather than to the cleavage of the alkane chain.

In summary, although the catalyst obtained by the hydrothermal post-impregnation method in comparative example 1 has a stable structure, the catalytic performance needs to be further improved, and the performance of examples 1-2 of the present invention is obviously improved compared with comparative example 1. Comparative example 2 using the metal pre-loading method, although the synthesis procedure can be further simplified and the resulting catalyst is excellent in performance, the stability of the catalyst is insufficient due to the influence of the metal @ aluminum/silicon precursor during the molecular sieve crystallization process. The method disclosed by the embodiment 1-2 of the invention further simplifies the synthesis steps while maintaining the catalytic performance of the pre-loading method, and compared with the method for damaging the catalyst structure by the pre-loading method, the method disclosed by the embodiment of the invention also keeps the stability of the catalyst structure while improving the catalytic performance.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention. The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.