Alkane isomerization catalyst and preparation method thereof

Abstract

The present invention discloses an alkane isomerization catalyst and a preparation method thereof, relating to the technical field of catalyst preparation. The method comprises the following steps: Step S1, preparation of a catalyst support precursor; Step S2, surface modification of the catalyst support precursor; Step S3, sulfation; and Step S4, precious metal loading. The alkane isomerization catalyst has higher catalytic activity, improved feedstock conversion rate and selectivity, is environmentally friendly, and does not corrode equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, in particular to an alkane isomerization catalyst and a preparation method thereof. Background Art

[0002] In recent years, with economic development and increasingly stringent environmental protection requirements, the demand for clean gasoline has intensified, and the quality requirements for automotive gasoline products have also become increasingly stringent. Isomerized gasoline, a common clean, high-quality gasoline, has attracted increasing attention and demand due to its advantages such as low sulfur, absence of olefins and aromatics, a small difference between RON and MON, low density, and excellent automotive engine starting performance. Isomerized gasoline is produced through the alkane isomerization reaction. The core of the alkane isomerization reaction lies in the alkane isomerization catalyst, which plays a key role in improving the reaction conversion rate, selectivity, and yield.

[0003] Currently, alkane isomerization catalysts primarily include medium-temperature molecular sieve isomerization catalysts, solid superacid isomerization catalysts, and low-temperature isomerization catalysts. Medium-temperature molecular sieve isomerization catalysts are bifunctional catalysts composed of precious metals loaded onto molecular sieves. The reaction temperature is between 240 and 280°C. The molecular sieve is primarily mordenite. They are characterized by strong adaptability to feedstocks, but a slightly lower isomerization rate, requiring a recycling process to increase the product octane number. Low-temperature isomerization catalysts are precious metal / Cl-Al₂O₃ catalysts. The acidity of the catalyst is provided by Cl₂. The reaction temperature range is 115 to 150°C. They are characterized by a higher isomerization rate. The feedstocks must be dehydrated, sulfur-free, and nitrogen-free. Impurity fluctuations can easily lead to catalyst deactivation, requiring regular chlorine replenishment and potentially causing equipment corrosion. Solid superacid isomerization catalysts usually use Pt-loaded sulfated zirconia as the active ingredient, and the reaction temperature is 170-210°C. This type of catalyst has the advantages of easy separation from the reactants, safe operation, and low equipment requirements. However, the solid superacid material itself has problems such as low specific surface area, easy loss of acid centers, and poor thermal stability of the zirconia active phase.

[0004] To address the above-mentioned problems, Chinese invention patent document CN106140198B discloses a method for preparing a light normal alkane isomerization catalyst and a method for isomerizing light normal alkane. The solid superacid catalyst is synthesized by coprecipitation and hydrothermal treatment. The catalyst can be used for the isomerization of C4-C8 normal alkanes, particularly n-pentane. The presence of hydrogen in the reaction atmosphere significantly improves the reactivity and stability of the catalyst. The normal alkane isomerization catalyst and reaction process are characterized by being environmentally friendly, non-corrosive to equipment, having high activity and selectivity, and having stable reactivity. However, the catalyst's feedstock conversion rate and selectivity need to be further improved.

[0005] It can be seen that it is necessary to seek a more effective method to prepare an alkane isomerization catalyst with higher catalytic activity, higher raw material conversion rate and selectivity, environmental friendliness, and no corrosion to equipment. Summary of the Invention

[0006] The main purpose of the present invention is to provide an alkane isomerization catalyst with higher catalytic activity, higher raw material conversion rate and selectivity, environmental friendliness, and no corrosion to equipment, and a preparation method thereof.

[0007] To achieve the above object, the present invention provides a method for preparing an alkane isomerization catalyst, comprising the following steps:

[0008] Step S1, preparation of catalyst support precursor: disperse zirconium source, rare earth source, nickel source and M source in ethylene glycol, stir evenly, slowly add sodium acetate, and vigorously stir for 2 hours, then transfer the mixture to a polytetrafluoroethylene-lined hydrothermal reactor and react at 180-200°C for 14-22 hours; remove the reactor, and after the reaction system cools, repeatedly wash with deionized water and anhydrous ethanol, and then dry in a vacuum drying oven at 110-130°C to constant weight;

[0009] Step S2, surface modification of the catalyst support precursor: the catalyst support precursor prepared in step S1 is dispersed in ethanol, tetradecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride is added thereto, and the mixture is stirred at 45-55° C. for 4-6 hours, and the ethanol is then removed by rotary evaporation to obtain a surface-modified catalyst support precursor;

[0010] Step S3, sulfation: adding the surface-modified catalyst support precursor into the sulfonation reagent for immersion, so that SO4 2- After the impregnation amount reaches a certain value, the catalyst carrier is dried at 120-150°C for 18-24 hours and then calcined at 650-850°C for 3-6 hours to obtain a sulfonated catalyst carrier.

[0011] Step S4, precious metal loading: adding an ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride to the sulfonated catalyst support prepared in step S3 while stirring. The addition is completed within 1 hour, and stirring is continued for 2-3 hours after the addition is completed. The crude product is then dried in a vacuum drying oven at 80-90° C. for 10-15 hours to obtain a modified support. The support is then impregnated in a soluble salt solution containing precious metals until the precious metal loading reaches a certain value. The support is then dried at 105-125° C. for 15-20 hours, calcined at 600-800° C. for 4-8 hours, and finally reduced with a reducing gas to obtain an alkane isomerization catalyst.

[0012] Preferably, the mass ratio of the zirconium source, rare earth source, nickel source, M source, ethylene glycol and sodium acetate in step S1 is 1:(0.01-0.03):0.02:0.01:(8-12):(2-3).

[0013] Preferably, the zirconium source is zirconium nitrate or zirconium oxychloride; the rare earth source is at least one of scandium nitrate, yttrium nitrate, and cerium chloride; the nickel source is nickel nitrate; and the M source is at least one of zinc chloride, niobium chloride, aluminum chloride, and manganese nitrate.

[0014] Preferably, in step S2, the mass ratio of the catalyst support precursor, ethanol, and tetradecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride is 1:(3-5):(0.08-0.15).

[0015] Preferably, the sulfonating agent in step S3 is a sulfuric acid solution or an ammonium sulfate solution with a concentration of 0.2-2 mol / L.

[0016] Preferably, the SO4 in step S3 2- The impregnation amount reaches a certain value, wherein the certain value is 1 to 4 wt % of the total weight of the surface-modified catalyst support precursor.

[0017] Preferably, the mass ratio of the sulfonated catalyst support and the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride in step S4 is 1: (0.1-0.3); the mass percentage concentration of the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride is 8-15wt%.

[0018] Preferably, the soluble salt solution containing precious metals is any one of chloroplatinic acid solution, chloropalladic acid solution, and a mixed solution of chloroplatinic acid and chloropalladic acid.

[0019] Preferably, the precious metal loading in step S4 reaches a certain value, in which the certain value is 0.04-0.09wt% of the total weight of the modified support; the reducing gas in step S4 is a mixed gas formed by mixing hydrogen and nitrogen in a volume ratio of 1:(2-3), and the flow rate is 28-32mL / min.

[0020] Preferably, the reduction temperature in step S4 is 300-500° C., and the reduction time is 5-10 h.

[0021] Another object of the present invention is to provide an alkane isomerization catalyst prepared by the above-mentioned preparation method of the alkane isomerization catalyst.

[0022] Due to the application of the above technical solution, the present invention has the following beneficial effects:

[0023] (1) The alkane isomerization catalyst disclosed in the present invention has a simple preparation process, is easy to operate, consumes little energy, has low dependence on equipment, and has good social benefits and industrialization potential.

[0024] (2) The alkane isomerization catalyst disclosed in the present invention has the advantages of better coordination and cooperation between components and preparation steps through the rational selection of components and preparation steps, which gives the product the advantages of higher catalytic activity, higher raw material conversion rate and higher selectivity; at the same time, the finished catalyst has the advantages of no pollution to the environment, no corrosion to equipment and stable catalyst when used in isomerization reaction.

[0025] (3) The alkane isomerization catalyst disclosed in the present invention comprises a catalyst support precursor prepared from raw materials including a zirconium source, a rare earth source, a nickel source and an M source, wherein the M source is at least one of zinc chloride, niobium chloride, aluminum chloride and manganese nitrate; by rationally selecting the types and proportions of these components, the catalytic activity and performance stability of the alkane isomerization catalyst can be effectively improved, while also effectively improving the raw material conversion rate and selectivity.

[0026] (4) The alkane isomerization catalyst disclosed in the present invention is modified with tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride before sulfation and precious metal loading, and an organic cationic structure is introduced to increase the sulfuric acid SO4 2- At the same time, it can also help to disperse them evenly, avoid the loss of acid centers, and effectively improve the catalytic activity and stability of the final product, and improve the raw material conversion rate and selectivity.

[0027] (5) The alkane isomerization catalyst disclosed in the present invention has a larger specific surface area of the product through the reasonable selection of catalyst preparation process parameters and steps, which can effectively promote the adsorption and desorption of alkanes in the catalyst, thereby improving the catalytic activity. DETAILED DESCRIPTION

[0028] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are merely examples, and those skilled in the art may conceive of other obvious variations. Example 1

[0029] A method for preparing an alkane isomerization catalyst comprises the following steps:

[0030] Step S1, preparation of catalyst support precursor: disperse zirconium source, rare earth source, nickel source and M source in ethylene glycol, stir evenly, slowly add sodium acetate, and vigorously stir for 2 hours. Transfer the mixture to a polytetrafluoroethylene-lined hydrothermal reactor and react at 180°C for 14 hours; remove the reactor, and after the reaction system cools, repeatedly wash with deionized water and anhydrous ethanol, and then dry in a vacuum drying oven at 110°C to constant weight;

[0031] Step S2, surface modification of the catalyst support precursor: the catalyst support precursor prepared in step S1 is dispersed in ethanol, tetradecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride is added thereto, and the mixture is stirred and reacted at 45° C. for 4 hours, and the ethanol is then removed by rotary evaporation to obtain a surface-modified catalyst support precursor;

[0032] Step S3, sulfation: adding the surface-modified catalyst support precursor into the sulfonation reagent for immersion, so that SO4 2- When the impregnation amount reaches a certain value, the catalyst support is dried at 120°C for 18 hours and then calcined at 650°C for 3 hours to obtain a sulfonated catalyst support.

[0033] Step S4, precious metal loading: adding an ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride to the sulfonated catalyst support prepared in step S3 while stirring, and completing the addition within 1 hour. After the addition, stirring is continued for 2 hours. The crude product is then dried in a vacuum drying oven at 80° C. for 10 hours to obtain a modified support. The support is then impregnated in a soluble salt solution containing precious metals until the precious metal loading reaches a certain value. The support is then dried at 105° C. for 15 hours, calcined at 600° C. for 4 hours, and finally reduced with a reducing gas to obtain an alkane isomerization catalyst.

[0034] The mass ratio of the zirconium source, rare earth source, nickel source, M source, ethylene glycol, and sodium acetate in step S1 is 1: 0.01: 0.02: 0.01: 8: 2; the zirconium source is zirconium nitrate; the rare earth source is scandium nitrate; the nickel source is nickel nitrate; and the M source is zinc chloride.

[0035] The mass ratio of the catalyst support precursor, ethanol, and tetradecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride in step S2 is 1:3:0.08.

[0036] The sulfonating agent in step S3 is a sulfuric acid solution with a concentration of 0.2 mol / L; the SO4 2- The impregnation amount reaches a certain value, wherein the certain value is 1 wt % of the total weight of the surface-modified catalyst support precursor.

[0037] The mass ratio of the sulfonated catalyst support and the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride in step S4 is 1:0.1; the mass percentage concentration of the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride is 8wt%; and the soluble salt solution containing the precious metal is a chloroplatinic acid solution.

[0038] In step S4, the certain value in which the precious metal loading reaches a certain value is 0.04wt% of the total weight of the modified support; the reducing gas is a mixture of hydrogen and nitrogen in a volume ratio of 1:2, with a flow rate of 28mL / min; the reduction temperature of the reduction is 300°C, and the reduction time is 5h.

[0039] An alkane isomerization catalyst prepared by adopting the preparation method of the alkane isomerization catalyst. Example 2

[0040] A method for preparing an alkane isomerization catalyst comprises the following steps:

[0041] Step S1, preparation of catalyst support precursor: disperse zirconium source, rare earth source, nickel source and M source in ethylene glycol, stir evenly, slowly add sodium acetate, and stir vigorously for 2 hours. Transfer the mixture to a polytetrafluoroethylene-lined hydrothermal reactor and react at 185°C for 16 hours; remove the reactor, and after the reaction system cools, repeatedly wash with deionized water and anhydrous ethanol, and then dry in a vacuum drying oven at 115°C to constant weight;

[0042] Step S2, surface modification of the catalyst support precursor: The catalyst support precursor prepared in step S1 was dispersed in ethanol, and tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride was added thereto. The mixture was stirred and reacted at 47° C. for 4.5 hours, and the ethanol was then removed by rotary evaporation to obtain a surface-modified catalyst support precursor.

[0043] Step S3, sulfation: adding the surface-modified catalyst support precursor into the sulfonation reagent for immersion, so that SO4 2- When the impregnation amount reaches a certain value, the catalyst support is dried at 130°C for 20 hours and then calcined at 700°C for 4 hours to obtain a sulfonated catalyst support.

[0044] Step S4, precious metal loading: an ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride is added to the sulfonated catalyst support prepared in step S3 while stirring. The addition is completed within 1 hour, and stirring is continued for 2.3 hours after the addition is completed. The crude product is then dried in a vacuum drying oven at 83° C. for 11 hours to obtain a modified support. The support is then impregnated in a soluble salt solution containing precious metals until the precious metal loading reaches a certain value. The support is then dried at 110° C. for 17 hours, calcined at 650° C. for 5 hours, and finally reduced with a reducing gas to obtain an alkane isomerization catalyst.

[0045] The mass ratio of the zirconium source, rare earth source, nickel source, M source, ethylene glycol, and sodium acetate in step S1 is 1: 0.015: 0.02: 0.01: 9: 2.3; the zirconium source is zirconium oxychloride; the rare earth source is yttrium nitrate; the nickel source is nickel nitrate; and the M source is niobium chloride.

[0046] The mass ratio of the catalyst support precursor, ethanol, and tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride in step S2 is 1:3.5:0.1.

[0047] The sulfonating agent in step S3 is an ammonium sulfate solution with a concentration of 0.8 mol / L; the SO4 2- The impregnation amount reaches a certain value, wherein the certain value is 2 wt % of the total weight of the surface-modified catalyst support precursor.

[0048] The mass ratio of the sulfonated catalyst support and the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride in step S4 is 1:0.15; the mass percentage concentration of the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride is 10wt%; the soluble salt solution containing precious metals is a chloropalladic acid solution; the precious metal loading reaches a certain value in which the certain value is 0.06wt% of the total weight of the modified support; the reducing gas is a mixed gas formed by mixing hydrogen and nitrogen in a volume ratio of 1:2.2, with a flow rate of 29mL / min; the reduction temperature of the reduction is 350°C, and the reduction time is 6h.

[0049] An alkane isomerization catalyst prepared by adopting the preparation method of the alkane isomerization catalyst. Example 3

[0050] A method for preparing an alkane isomerization catalyst comprises the following steps:

[0051] Step S1, preparation of catalyst support precursor: disperse zirconium source, rare earth source, nickel source and M source in ethylene glycol, stir evenly, slowly add sodium acetate, and stir vigorously for 2 hours. Transfer the mixture to a polytetrafluoroethylene-lined hydrothermal reactor and react at 190°C for 18 hours; remove the reactor, and after the reaction system cools, repeatedly wash with deionized water and anhydrous ethanol, and then dry in a vacuum drying oven at 120°C to constant weight;

[0052] Step S2, surface modification of the catalyst support precursor: the catalyst support precursor prepared in step S1 was dispersed in ethanol, tetradecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride was added thereto, and the mixture was stirred and reacted at 50° C. for 5 hours, and then the ethanol was removed by rotary evaporation to obtain a surface-modified catalyst support precursor;

[0053] Step S3, sulfation: adding the surface-modified catalyst support precursor into the sulfonation reagent for immersion, so that SO4 2- When the impregnation amount reaches a certain value, the catalyst support is dried at 135°C for 21 hours and then calcined at 750°C for 4.5 hours to obtain a sulfonated catalyst support.

[0054] Step S4, precious metal loading: adding an ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride to the sulfonated catalyst support prepared in step S3 while stirring, and completing the addition within 1 hour. After completion of the addition, stirring is continued for 2.5 hours. The crude product is then dried in a vacuum drying oven at 85° C. for 13 hours to obtain a modified support. The support is then impregnated in a soluble salt solution containing precious metals until the precious metal loading reaches a certain value. The support is then dried at 115° C. for 18 hours, calcined at 700° C. for 6 hours, and finally reduced with a reducing gas to obtain an alkane isomerization catalyst.

[0055] The mass ratio of the zirconium source, rare earth source, nickel source, M source, ethylene glycol, and sodium acetate in step S1 is 1: 0.02: 0.02: 0.01: 10: 2.5; the zirconium source is zirconium nitrate; the rare earth source is cerium chloride; the nickel source is nickel nitrate; and the M source is aluminum chloride.

[0056] The mass ratio of the catalyst support precursor, ethanol, and tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride in step S2 is 1:4:0.11.

[0057] The sulfonating agent in step S3 is a sulfuric acid solution with a concentration of 1.3 mol / L; the SO4 2- The impregnation amount reaches a certain value, wherein the certain value is 2.5 wt % of the total weight of the surface-modified catalyst support precursor.

[0058] The mass ratio of the sulfonated catalyst support and the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride in step S4 is 1:0.2; the mass percentage concentration of the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride is 12wt%; the soluble salt solution containing precious metals is a chloroplatinic acid solution; the precious metal loading reaches a certain value in which the certain value is 0.07wt% of the total weight of the modified support; the reducing gas is a mixed gas formed by mixing hydrogen and nitrogen in a volume ratio of 1:2.5, with a flow rate of 30mL / min; the reduction temperature of the reduction is 400°C, and the reduction time is 7.5h.

[0059] An alkane isomerization catalyst prepared by adopting the preparation method of the alkane isomerization catalyst. Example 4

[0060] A method for preparing an alkane isomerization catalyst comprises the following steps:

[0061] Step S1, preparation of catalyst support precursor: disperse zirconium source, rare earth source, nickel source and M source in ethylene glycol, stir evenly, slowly add sodium acetate, and stir vigorously for 2 hours. Transfer the mixture to a polytetrafluoroethylene-lined hydrothermal reactor and react at 195°C for 20 hours; remove the reactor, and after the reaction system cools, repeatedly wash with deionized water and anhydrous ethanol, and then dry in a vacuum drying oven at 125°C to constant weight;

[0062] Step S2, surface modification of the catalyst support precursor: The catalyst support precursor prepared in step S1 was dispersed in ethanol, and tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride was added thereto. The mixture was stirred and reacted at 53° C. for 5.5 hours, and the ethanol was then removed by rotary evaporation to obtain a surface-modified catalyst support precursor.

[0063] Step S3, sulfation: adding the surface-modified catalyst support precursor into the sulfonation reagent for immersion, so that SO4 2- When the impregnation amount reaches a certain value, the catalyst support is dried at 145°C for 23 hours and then calcined at 830°C for 5.5 hours to obtain the sulfonated catalyst support;

[0064] Step S4, precious metal loading: an ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride is added to the sulfonated catalyst support prepared in step S3 while stirring. The addition is completed within 1 hour, and stirring is continued for 2.8 hours after the addition is completed. The crude product is then dried in a vacuum drying oven at 88° C. for 14 hours to obtain a modified support. The support is then impregnated in a soluble salt solution containing precious metals until the precious metal loading reaches a certain value. The support is then dried at 120° C. for 19 hours, calcined at 750° C. for 7.5 hours, and finally reduced with a reducing gas to obtain an alkane isomerization catalyst.

[0065] The mass ratio of the zirconium source, rare earth source, nickel source, M source, ethylene glycol, and sodium acetate in step S1 is 1: 0.025: 0.02: 0.01: 11: 2.8; the zirconium source is zirconium nitrate; the rare earth source is a mixture of scandium nitrate, yttrium nitrate, and cerium chloride in a mass ratio of 1: 2: 1; the nickel source is nickel nitrate; and the M source is a mixture of zinc chloride, niobium chloride, aluminum chloride, and manganese nitrate in a mass ratio of 1: 2: 3: 1.

[0066] The mass ratio of the catalyst support precursor, ethanol, and tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride in step S2 is 1:4.5:0.13.

[0067] The sulfonating agent in step S3 is a sulfuric acid solution with a concentration of 1.8 mol / L; the SO4 2- The impregnation amount reaches a certain value, wherein the certain value is 3.5 wt % of the total weight of the surface-modified catalyst support precursor.

[0068] The mass ratio of the sulfonated catalyst support and the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride in step S4 is 1:0.25; the mass percentage concentration of the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride is 14wt%; the soluble salt solution containing precious metals is a chloropalladic acid solution; the precious metal loading reaches a certain value in which the certain value is 0.08wt% of the total weight of the modified support; the reducing gas is a mixed gas formed by mixing hydrogen and nitrogen in a volume ratio of 1:2.8, with a flow rate of 31mL / min; the reduction temperature of the reduction is 450°C, and the reduction time is 9h.

[0069] An alkane isomerization catalyst prepared by adopting the preparation method of the alkane isomerization catalyst. Example 5

[0070] A method for preparing an alkane isomerization catalyst comprises the following steps:

[0071] Step S1, preparation of catalyst support precursor: disperse the zirconium source, rare earth source, nickel source and M source in ethylene glycol, stir evenly, slowly add sodium acetate, and vigorously stir for 2 hours. Then, transfer the mixture to a polytetrafluoroethylene-lined hydrothermal reactor and react at 200°C for 22 hours. Remove the reactor, wait for the reaction system to cool, repeatedly wash with deionized water and anhydrous ethanol, and then dry in a vacuum drying oven at 130°C to constant weight.

[0072] Step S2, surface modification of the catalyst support precursor: the catalyst support precursor prepared in step S1 was dispersed in ethanol, tetradecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride was added thereto, and the mixture was stirred and reacted at 55° C. for 6 hours, and then the ethanol was removed by rotary evaporation to obtain a surface-modified catalyst support precursor;

[0073] Step S3, sulfation: adding the surface-modified catalyst support precursor into the sulfonation reagent for immersion, so that SO4 2- When the impregnation amount reaches a certain value, the catalyst support is dried at 150°C for 24 hours and then calcined at 850°C for 6 hours to obtain a sulfonated catalyst support.

[0074] Step S4, precious metal loading: adding an ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride to the sulfonated catalyst support prepared in step S3 while stirring, and completing the addition within 1 hour. After completion of the addition, stirring is continued for 3 hours. The crude product is then dried in a vacuum drying oven at 90° C. for 15 hours to obtain a modified support. The support is then impregnated in a soluble salt solution containing precious metals until the precious metal loading reaches a certain value. The support is then dried at 125° C. for 20 hours, calcined at 800° C. for 8 hours, and finally reduced with a reducing gas to obtain an alkane isomerization catalyst.

[0075] The mass ratio of the zirconium source, rare earth source, nickel source, M source, ethylene glycol, and sodium acetate in step S1 is 1: 0.03: 0.02: 0.01: 12: 3; the zirconium source is zirconium oxychloride; the rare earth source is scandium nitrate; the nickel source is nickel nitrate; and the M source is aluminum chloride.

[0076] The mass ratio of the catalyst support precursor, ethanol, and tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride in step S2 is 1:5:0.15.

[0077] The sulfonating agent in step S3 is a sulfuric acid solution with a concentration of 2 mol / L; the SO4 in step S3 2- The impregnation amount reaches a certain value, wherein the certain value is 4 wt % of the total weight of the surface-modified catalyst support precursor.

[0078] The mass ratio of the sulfonated catalyst support and the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride in step S4 is 1:0.3; the mass percentage concentration of the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride is 15wt%; the soluble salt solution containing precious metals is a chloroplatinic acid solution; the precious metal loading reaches a certain value in which the certain value is 0.09wt% of the total weight of the modified support; the reducing gas is a mixed gas formed by mixing hydrogen and nitrogen in a volume ratio of 1:3, with a flow rate of 32mL / min; the reduction temperature of the reduction is 500°C, and the reduction time is 10h.

[0079] An alkane isomerization catalyst prepared by adopting the preparation method of the alkane isomerization catalyst.

[0080] Comparative Example 1

[0081] An alkane isomerization catalyst is substantially the same as that of Example 1, except that no rare earth source and M source are added.

[0082] Comparative Example 2

[0083] An alkane isomerization catalyst is substantially the same as that of Example 1, except that step S2, surface modification of the catalyst support precursor, is omitted.

[0084] In order to further illustrate the beneficial technical effects of the alkane isomerization catalysts prepared in each embodiment of the present invention, the catalytic performance of the alkane isomerization catalysts prepared in Examples 1-5 and Comparative Examples 1-2 was tested. The test results are shown in Table 1. The test method is as follows: 5 grams of each alkane isomerization catalyst was loaded into a 10 mL fixed bed reactor, activated at 200°C under a hydrogen atmosphere for 2 hours, and then switched to n-pentane for reaction. Reaction conditions: temperature 200°C, system pressure 2 MPa, hydrogen partial pressure 0.8 MPa, space velocity 2 h -1 The molar ratio of hydrogen to n-pentane was 1:3. After 2 hours of reaction, samples were taken for analysis, and the n-pentane conversion and isopentane selectivity were statistically calculated. The test results are shown in Table 1.

[0085] Table 1

[0086] project n-pentane conversion Isopentane selectivity unit % % Example 1 66.3 98.6 Example 2 66.8 98.8 Example 3 67.6 99.1 Example 4 68.0 99.2 Example 5 68.2 99.4 Comparative Example 1 60.8 94.1 Comparative Example 2 62.2 95.7

[0087] As can be seen from Table 1, the alkane isomerization catalyst disclosed in the embodiment of the present invention has better catalytic effect and better selectivity than the comparative example product; the addition of rare earth source and M source, and the setting of step S2, surface modification of the catalyst support precursor are beneficial to improving the above performance.

[0088] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions merely illustrate the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an alkane isomerization catalyst, characterized in that: The steps include: Step S1, preparation of a catalyst support precursor: dispersing a zirconium source, a rare earth source, a nickel source and an M source in ethylene glycol, stirring evenly, slowly adding sodium acetate, and then vigorously stirring for 2 hours, transferring the mixture to a polytetrafluoroethylene-lined hydrothermal reactor, and reacting at 180-200°C for 14-22 hours; taking out the reactor, and after the reaction system is cooled, repeatedly washing with deionized water and anhydrous ethanol, and then drying to constant weight in a vacuum drying oven at 110-130°C; the mass ratio of the zirconium source, rare earth source, nickel source, M source, ethylene glycol, and sodium acetate is 1:(0.01-0.03):0.02:0.01:(8-12):(2-3); the rare earth source is at least one of scandium nitrate, yttrium nitrate, and cerium chloride; the M source is at least one of zinc chloride, niobium chloride, aluminum chloride, and manganese nitrate; Step S2, surface modification of the catalyst support precursor: the catalyst support precursor prepared in step S1 is dispersed in ethanol, tetradecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride is added thereto, and the mixture is stirred at 45-55° C. for 4-6 hours, and the ethanol is then removed by rotary evaporation to obtain a surface-modified catalyst support precursor; Step S3, sulfation: adding the surface-modified catalyst support precursor into the sulfonation reagent for immersion, so that SO4 2- After the impregnation amount reaches a certain value, the catalyst carrier is dried at 120-150°C for 18-24 hours and then calcined at 650-850°C for 3-6 hours to obtain a sulfonated catalyst carrier. Step S4, precious metal loading: adding an ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride to the sulfonated catalyst support prepared in step S3 while stirring. The addition is completed within 1 hour, and stirring is continued for 2-3 hours after the addition is completed. The crude product is then dried in a vacuum drying oven at 80-90° C. for 10-15 hours to obtain a modified support. The support is then impregnated in a soluble salt solution containing precious metals until the precious metal loading reaches a certain value. The support is then dried at 105-125° C. for 15-20 hours, calcined at 600-800° C. for 4-8 hours, and finally reduced with a reducing gas to obtain an alkane isomerization catalyst.

2. The method for preparing an alkane isomerization catalyst according to claim 1, wherein: The zirconium source is zirconium nitrate or zirconium oxychloride; and the nickel source is nickel nitrate.

3. The method for preparing an alkane isomerization catalyst according to claim 1, wherein: The mass ratio of the catalyst support precursor, ethanol, and tetradecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride in step S2 is 1:(3-5):(0.08-0.15).

4. The method for preparing an alkane isomerization catalyst according to claim 1, wherein: The sulfonating agent in step S3 is a sulfuric acid solution or ammonium sulfate solution with a concentration of 0.2-2 mol / L; the SO4 in step S3 2- The impregnation amount reaches a certain value, wherein the certain value is 1 to 4 wt % of the total weight of the surface-modified catalyst support precursor.

5. The method for preparing an alkane isomerization catalyst according to claim 1, wherein: The mass ratio of the sulfonated catalyst support and the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride in step S4 is 1: (0.1-0.3); the mass percentage concentration of the ethanol solution of tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride is 8-15wt%.

6. The method for preparing an alkane isomerization catalyst according to claim 1, wherein: The soluble salt solution containing precious metals is any one of chloroplatinic acid solution, chloropalladic acid solution, and chloroplatinic acid-chloropalladic acid mixed solution.

7. The method for preparing an alkane isomerization catalyst according to claim 1, wherein: The noble metal loading amount in step S4 reaches a certain value, wherein the certain value is 0.04-0.09wt% of the total weight of the modified support; the reducing gas in step S4 is a mixed gas formed by mixing hydrogen and nitrogen in a volume ratio of 1:(2-3), and the flow rate is 28-32mL / min.

8. The method for preparing an alkane isomerization catalyst according to claim 1, wherein: The reduction temperature in step S4 is 300-500° C., and the reduction time is 5-10 h.

9. An alkane isomerization catalyst prepared by the preparation method of the alkane isomerization catalyst according to any one of claims 1 to 8.