A kind of alkane isomerization catalyst and its preparation method and application

Abstract

The present invention discloses an alkane isomerization catalyst, its preparation method, and application. The catalyst comprises an active metal, aluminum oxide, and an aluminum oxide-modified molecular sieve, wherein the molecular sieve is selected from at least one of a ZSM-5 molecular sieve or a pure silicon-based molecular sieve; the aluminum oxide-modified molecular sieve has an external surface Brønsted acid content of 0.01 to 0.25 mmol / g. The catalyst of the present invention is used for the hydrogenation reaction of normal alkanes and exhibits high selectivity and yield of isomerized products.

Description

Technical Field

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

[0002] Alkane isomerization reaction plays an important role in the entire industrial refining process. 10 The hydroisomerization of light alkanes produces clean, high-octane isomerized oils, while the isomerization of long-chain alkanes is primarily used to improve the low-temperature flow properties of middle distillates (jet fuel and diesel) and lubricating oils. Currently, the predominant industrial alkane isomerization catalyst is a medium-temperature metal / zeolite dual-functional catalytic system. Common active metals, typically precious metals such as Pt, Pd, and Ir, primarily provide hydrogenation-dehydrogenation functions; while the zeolite system primarily provides acidic sites and pore shape selectivity. Zeolites such as mordenite MOR, Y, BETA, ZSM-5, and SAPO-11, among others, exhibit excellent catalytic performance in specific alkane isomerization reactions due to their unique pore topology and physicochemical properties.

[0003] CN111215131A discloses an isomerization catalyst supported by an MTW-type molecular sieve and a preparation method. The in-situ carbon deposits generated during the preparation process partially fill the micropores of the molecular sieve, shortening the pore depth and covering some of the strong B acid sites within the micropores, significantly improving the mass transfer of reactants and intermediates. The prepared catalyst exhibits excellent isomerization performance. Nathan et al. (Mesoporous Aluminosilicate Catalysts for the Selective Isomerization of n-Hexane: The Roles of Surface Acidity and Platinum Metal. J. Am. Chem. Soc. 2015, 137, 32, 10231– 10237) systematically studied the isomerization of n-hexane catalyzed by molecular sieves such as MFI, Beta, and MCF-17. The results showed that strong B acid within the microporous crystals of the molecular sieve would aggravate the cracking process and be detrimental to the formation of isomerized products. Furthermore, an Al-modified mesoporous MCF-17 molecular sieve was designed and synthesized based on a grafting method.

[0004] The pore structure and acidic site distribution of the zeolite, as well as the distance between the metal-acid dual active sites, are important factors influencing the isomerization process. De Jong's research group (Nanoscale intimacy in bifunctional catalysts for selective conversion of hydrocarbons. Nature. 2015, 528:245-248) believes that when the metal sites are located on an alumina binder, the metal active sites and the acidic sites of the Y zeolite are in nanoscale contact. At this point, olefin intermediates formed on the metal active sites preferentially undergo "pore-mouth catalysis," suppressing the enrichment of olefin intermediates on the B acid in the zeolite's micropores and thus preventing intracrystalline mass transfer of the intermediates within the deeper pores. Subsequently, the research group (Influence of Nanoscale Intimacy and Zeolite Micropore Size on the Performance of Bifunctional Catalysts for n-Heptane Hydroisomerization. ACS Catal. 2020, 10: 14245-14257), (Impact of the Spatial Organization of Bifunctional Metal-Zeolite Catalysts for Hydroisomerization of Light Alkanes. Angew Chem. Int Ed. 2020, 59: 3592- 3600) systematically studied the alkane isomerization process in molecular sieve systems such as ZSM-5, Beta, MOR, and ZSM-22, and pointed out that the topological structure of the molecular sieve has a significant influence on the distance effect. At present, the development and design of efficient catalysts is the difficulty of applying the "dual active site nanoscale contact superiority" effect to the alkane isomerization reaction. Summary of the Invention

[0005] To address the low selectivity and yield of isomerized products in the prior art n-alkane isomerization hydrogenation process, the present invention provides an alkane isomerization catalyst, its preparation method, and application. The alkane isomerization catalyst of the present invention is used in the n-alkane isomerization hydrogenation reaction and has high selectivity and yield of isomerized products.

[0006] The first aspect of the present invention provides an alkane isomerization catalyst, comprising an active metal, alumina (derived from a binder component, i.e., binder alumina) and an alumina-modified molecular sieve, wherein the molecular sieve is selected from at least one of a ZSM-5 molecular sieve or a pure silicon-based molecular sieve; in the modified molecular sieve, the amount of B acid on the external surface is 0.01 to 0.25 mmol / g.

[0007] Furthermore, the alumina-modified molecular sieve is an alumina-modified ZSM-5 molecular sieve, and the ratio of the amount of Br2+ acid on the outer surface to the total amount of Br2+ acid is 0.10 to 0.50.

[0008] Furthermore, the alumina-modified molecular sieve is an alumina-modified pure silicon-based molecular sieve, and the B acid sites only exist on the outer surface of the pure silicon-based molecular sieve.

[0009] Furthermore, in the catalyst, the mass ratio of the alumina-modified molecular sieve to the binder alumina is 8:1 to 1:8, preferably 3:1 to 1:3, and more preferably 1.5:1 to 1:1.5.

[0010] Furthermore, based on the weight of the catalyst, the content of the active metal is 0.01% to 10.0%, preferably 0.5% to 10.0%.

[0011] Furthermore, the active metal is one or more of Pt, Pd, Ir, Ni, and Mo, preferably Pt.

[0012] Furthermore, the pure silicon molecular sieve is selected from one or more of pure silicon MCM-41 molecular sieve, Silicalite-1 molecular sieve, pure silicon Beta molecular sieve, pure silicon HMS molecular sieve, and pure silicon MCF-17 molecular sieve, preferably one or more of pure silicon MCM-41 molecular sieve and Silicalite-1 molecular sieve.

[0013] In a second aspect, the present invention provides a method for preparing the above-mentioned alkane isomerization catalyst, comprising the following steps:

[0014] (1) mixing an aluminum source, an alkali source, a surfactant, ethanol, and water to obtain a modified solution;

[0015] (2) adding the molecular sieve raw powder to the modified solution obtained in step (1), transferring the mixture to a reactor after mixing, performing modification treatment, drying, and roasting to obtain a modified product;

[0016] (3) exchanging the modified product obtained in step (2) with ammonium ions and calcining to obtain an alumina-modified molecular sieve;

[0017] (4) adding a precursor solution containing an active metal dropwise to a suspension of an alumina binder, mixing the mixture evenly, and subjecting the mixture to a heat treatment to obtain an active metal / Al2O3;

[0018] (5) The active metal / Al2O3 obtained in step (4) and the modified molecular sieve obtained in step (3) are mixed and ground to obtain the alkane isomerization catalyst.

[0019] Furthermore, the aluminum source described in step (1) is selected from one or more of aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum carbonate, aluminum acetate, aluminum phosphate, aluminum oxide, aluminum isopropoxide, aluminum sol or pseudo-boehmite, preferably one or more of aluminum chloride, aluminum isopropoxide or aluminum sol, and more preferably aluminum chloride.

[0020] Furthermore, the surfactant described in step (1) is selected from one or more of tetrapropylammonium hydroxide (TPAOH), tetrapropylammonium bromide (TPABr), cetyltrimethylammonium bromide (CTAB), triethylamine and its homologues (such as tripropylamine) or ethylenediamine and its homologues (such as propylenediamine or butylenediamine), preferably one or more of tetrapropylammonium hydroxide (TPAOH), tetrapropylammonium bromide (TPABr) or cetyltrimethylammonium bromide (CTAB).

[0021] Furthermore, the alkali source in step (1) is selected from at least one of NaOH, KOH, Na2CO3, K2CO3, NaHCO3, and KHCO3, preferably NaOH.

[0022] Furthermore, in step (1), the aluminum source is calculated as Al2O3, the alkali source is calculated as oxide (M2O, wherein M represents an alkali metal ion), the surfactant, ethanol and water have a molar ratio of Al2O3:M2O:surfactant:ethanol:H2O=0.05-2.00:0.15-0.40:0.15-0.65:0.03-0.07:20-50.

[0023] Furthermore, after mixing in step (1), the mixture is stirred at 25 to 80° C. for 0.2 to 3.5 hours to obtain a modified liquid.

[0024] Furthermore, the molecular sieve in step (2) is a ZSM-5 molecular sieve, and the SiO2 / Al2O3 ratio is 300 to 1500, preferably 750 to 1200, and more preferably 850 to 1000.

[0025] Furthermore, the molecular sieve in step (2) is ZSM-5 molecular sieve with a specific surface area of ​​300 to 700 m 2 / g, preferably 500 to 700 m 2 / g.

[0026] Furthermore, the molecular sieve in step (2) is a ZSM-5 molecular sieve, and the amount of B acid on the outer surface is 0.0003 to 0.09 mmol / g, preferably 0.0003 to 0.01 mmol / g.

[0027] Furthermore, the molecular sieve in step (2) is a pure silicon molecular sieve, selected from one or more of pure silicon MCM-41 molecular sieve, Silicalite-1 molecular sieve, pure silicon Beta molecular sieve, pure silicon HMS molecular sieve, and pure silicon MCF-17 molecular sieve, preferably one or more of pure silicon MCM-41 molecular sieve or Silicalite-1 molecular sieve.

[0028] Furthermore, the molecular sieve in step (2) is a pure silicon molecular sieve with a specific surface area of ​​500 to 1200 m 2 / g, preferably 700 to 1200 m 2 / g.

[0029] Furthermore, the molecular sieve in step (2) is a pure silicon-based molecular sieve with no B acid sites on the outer surface.

[0030] Furthermore, in step (2), the mass ratio of the molecular sieve to the Al2O3 in the modified solution is 20:1 to 2:1.

[0031] Furthermore, in step (2), the mixing conditions are: stirring at 25-80° C. for 0.2-3.5 h.

[0032] Furthermore, in step (2), the modification treatment is carried out in a rotary oven at a rotation speed of 15 to 50 rpm, and the modification treatment conditions are: the modification temperature is 80 to 200° C., preferably 80 to 150° C., and the modification time is 10 h to 120 h, preferably 24 h to 96 h.

[0033] Furthermore, in step (2), after the modification treatment is completed, conventional steps such as separation and washing are first performed, and then drying is performed at 50-70° C. for 6-12 hours. The separation can be performed by centrifugation. The washing can be performed with deionized water until the pH value reaches 8-9.

[0034] Furthermore, in step (2), the roasting conditions are as follows: the roasting temperature is 500-700° C., and the roasting time is 6-12 hours.

[0035] Furthermore, in step (3), the ammonium ion exchange is carried out at 35-90° C. for 0.2-6.0 h, with the number of exchanges being 1-4. The ammonium salt used in the exchange is preferably ammonium nitrate, the concentration of the ammonium salt solution is 0.001-2.0 mol / L, and the solid-to-liquid mass ratio of the modified product to the ammonium salt solution is 0.1-3.5.

[0036] Furthermore, in step (3), after the ion exchange is completed, conventional steps such as separation and washing are first performed, and then drying is performed at 50-70° C. for 6-12 hours. The separation can be performed by centrifugation. The washing can be performed with deionized water until the pH value reaches 8-9.

[0037] Furthermore, in step (3), the roasting conditions are as follows: the roasting temperature is 350-750° C., and the roasting time is 0.5-10 h.

[0038] Furthermore, in step (4), the active metal is selected from one or more of Pt, Pd, Ir, Ni, and Mo, preferably Pt. The active metal precursor solution may be a soluble compound. For example, the Pt precursor solution is selected from one or more of chloroplatinic acid, ammonium tetrachloroplatinate, and tetraammineplatinum nitrate; the Pd precursor solution is selected from one or more of chloropalladic acid, palladium chloride, and palladium nitrate; the Ir precursor solution is selected from one or more of iridium trichloride and iridium acetylacetonate; the Ni precursor solution is selected from one or more of nickel nitrate and nickel chloride; and the Mo precursor solution is selected from one or more of ammonium molybdate and molybdenum nitrate.

[0039] Furthermore, the metal concentration of the precursor solution is 0.001 mg / mL to 2.50 mg / mL.

[0040] Furthermore, in step (4), the suspension is prepared by first dissolving alumina in water, stirring for 0.1 to 1.0 h, then slowly adding hydrochloric acid dropwise to adjust the pH value to 0.5 to 3.5, and continuing stirring for 0.5 to 2.0 h.

[0041] Furthermore, in step (4), the heat treatment conditions are as follows: the heat treatment temperature is 350-700°C, the heat treatment time is 1.0-8.0h, and the heat treatment atmosphere can be an oxygen atmosphere (such as air, O2), a reducing atmosphere (such as H2) or an inert atmosphere (such as N2 or Ar).

[0042] Furthermore, in step (5), the mass ratio of the active metal / Al2O3 to the modified molecular sieve is 1:9 to 9:1.

[0043] The third aspect of the present invention provides use of the above-mentioned alkane isomerization catalyst in catalyzing an alkane isomerization reaction.

[0044] Furthermore, the alkane is at least one of normal alkanes with 5 to 9 carbon atoms (such as at least one of n-pentane, n-hexane, n-heptane and n-octane).

[0045] Furthermore, the reaction conditions of the alkane isomerization reaction are preferably: temperature of 180-300°C, pressure of 1.0-3.0 MPa, molar ratio of hydrogen to normal alkane of 2.0-7.0, mass space velocity of alkane of 2.5-8.0h -1 .

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. The present invention provides a novel alkane isomerization catalyst comprising an active metal, alumina, and an alumina-modified molecular sieve. The molecular sieve is selected from a high-silicon-to-aluminum ratio ZSM-5 molecular sieve or a pure silicon-based molecular sieve. After modification, the molecular sieve contains abundant external surface Benzene acid sites and lacks microporous strong Benzene acid sites. The catalyst of the present invention is applied to the hydrogenation reaction of normal alkanes, favoring the formation of isomerized products and exhibiting high selectivity and yield of isomerized products.

[0048] 2. In the preparation process of the alkane isomerization catalyst of the present invention, a high-silicon-aluminum ratio ZSM-5 molecular sieve or a pure silicon-based molecular sieve is first modified. By adjusting the mass ratio of the molecular sieve to the Al2O3 in the modifying solution and the proportions of the various components in the modifying solution, an alumina-modified molecular sieve with abundant B acid sites on the external surface is obtained. The alumina-modified molecular sieve is then mixed with alumina loaded with an active metal. After comprehensive coordination of these steps, the catalyst is finally obtained. The alkane isomerization catalyst prepared by the present method exhibits higher selectivity and yield of isomerized products in the hydrogenation reaction of normal alkane isomerization. DETAILED DESCRIPTION

[0049] In order to more clearly illustrate the technical solution of the present invention, the following specific embodiments are listed. However, those skilled in the art will readily understand that the contents described in the embodiments are only used to illustrate the present invention and should not and will not limit the present invention described in detail in the claims.

[0050] In this study, the specific surface area and pore volume of the samples were determined by nitrogen physical adsorption using a Micromeritics ASAP 2020M. Prior to testing, the samples were vacuum-treated at 350°C for 4 hours. The specific surface area was calculated using the BET multipoint method within a relative pressure range of 0.05–0.25, and the pore volume and pore diameter were determined using the Saito-Foley method.

[0051] In this paper, pyridine adsorption infrared (Py-IR) testing of the samples was performed on a Nicolet 5700 FT-IR spectrometer. The testing process is as follows: First, the sample is formed into a self-supporting thin sheet, placed in a quartz vacuum infrared cell, and vacuum-treated at 400°C for 2 hours. After the temperature is lowered to 150°C, pyridine vapor is injected to saturate the catalyst with adsorption. After evacuation for 30 minutes, a spectrum is collected. The total borax acid content of the alumina-modified molecular sieve is determined based on the spectrum at 150°C, represented by X in mmol / g.

[0052] In this study, 2,6-di-tert-butylpyridine adsorption infrared (DTBPy-IR) measurements of the samples were performed on a Nicolet 5700 FT-IR spectrometer. The test procedure was as follows: the sample was first formed into a self-supporting thin sheet, placed in a quartz vacuum infrared cell cartridge, and vacuum-treated at 400°C for 2 hours. After the temperature was lowered to 50°C, 2,6-di-tert-butylpyridine vapor was injected to saturate the catalyst. After evacuation for 30 minutes, a spectrum was collected. The spectrum at 50°C was used to determine the amount of boronic acid on the outer surface of the alumina-modified molecular sieve, represented by Y in mmol / g.

[0053] In the present invention, the relevant parameters of the ZSM-5 molecular sieve raw powder used in Examples 1-4 and Comparative Examples 1, 3, and 4 are as follows: SiO2 / Al2O3=850, specific surface area (S BET )=525m 2 / g, pore volume = 0.11cm 3 / g, average pore size = 0.60nm. External surface B acid content 0.0003mmol / g.

[0054] In the present invention, the relevant parameters of the Silicalite-1 molecular sieve raw powder used in Examples 5-7 and Comparative Examples 2 and 5 are as follows: specific surface area (S BET )=725m 2 / g, pore volume = 0.20cm 3 / g, average pore diameter = 0.72nm.

[0055] In the present invention, the reaction product was analyzed using an Agilent 7890B gas chromatograph.

[0056] In the present invention, the calculation formulas for conversion, isomer selectivity and isomer yield are as follows, calculated by mass:

[0057] Conversion rate = 1-(amount of isohexane in the reactants / amount of n-hexane in the feed) × 100%;

[0058] Isomer selectivity = (amount of isohexane in product / product) × 100%;

[0059] Isomer yield = conversion × isomer selectivity × 100%.

[0060] Comparative Example 1

[0061] (1) Add 2 g of Al2O3 to 100 g of deionized water, stir for 30 min, then slowly add 0.1 mol / L hydrochloric acid dropwise to adjust the pH to 3, and continue stirring for 1 h;

[0062] (2) Then, add 20 mL of 1 mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the obtained filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0063] (3) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of ZSM-5 molecular sieve powder to obtain the catalyst of Comparative Example 1. The catalyst had a Pt content of 0.5%, an alumina content of 49.5%, and a molecular sieve content of 50%. The amounts of Boron acid (X and Y) of the ZSM-5 molecular sieve in the catalyst of Comparative Example 1 are shown in Table 1.

[0064] Comparative Example 2

[0065] (1) Add 2 g of Al2O3 to 100 g of deionized water, stir for 30 min, then slowly add 0.1 mol / L hydrochloric acid dropwise to adjust the pH to 3, and continue stirring for 1 h;

[0066] (2) Then, add 20 mL of 1 mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the obtained filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0067] (3) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of Silicalite-1 molecular sieve powder to obtain the catalyst of Comparative Example 2. The catalyst had a Pt content of 0.5%, an alumina content of 49.5%, and a molecular sieve content of 50%. The amount of B acid (X and Y) of the Silicalite-1 molecular sieve in the catalyst of Comparative Example 2 is shown in Table 1.

[0068] Comparative Example 3

[0069] (1) AlCl3, NaOH, and ethanol were dissolved in 30 ml of deionized water as a modification solution. The molar ratio of each component in the modification solution was 1.0Al2O3:0.2Na2O:0.05ethanol:30H2O. The solution was stirred at 25°C for 2 h to obtain a modification solution.

[0070] (2) Slowly add ZSM-5 molecular sieve powder to the modified solution and stir at 25°C for 6 hours, wherein the mass ratio of ZSM-5 powder to Al2O3 in the modified solution is maintained at 10:1; the above mixed solution is transferred to a polytetrafluoroethylene-lined stainless steel kettle, placed in a 150°C rotary oven, and modified at a stirring speed of 30 rpm for 40 hours. After centrifugation and separation and multiple washing, it is dried at 60°C for 12 hours and calcined at 550°C for 8 hours to obtain the modified product;

[0071] (3) The product obtained in step (2) is placed in an ammonium nitrate solution and heated and stirred at 80°C for 3 hours for ion exchange, centrifuged, washed with water several times, dried, and then calcined at 500°C for 6 hours. This process is repeated twice to obtain an alumina-modified ZSM-5 molecular sieve.

[0072] (4) Add 2g Al2O3 to 100g deionized water, stir for 30min, slowly drop 0.1mol / L hydrochloric acid to adjust pH to 3, and continue stirring for 1h; then drop 20mL 1mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the obtained filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0073] (5) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of the ZSM-5 molecular sieve obtained in step (3) to obtain the catalyst of Example 1. The catalyst contained 0.5% Pt, 49.5% alumina, and 50% alumina-modified molecular sieve. The amounts of B acid (X and Y) of the alumina-modified ZSM-5 molecular sieve in the catalyst of Comparative Example 3 are shown in Table 1.

[0074] Comparative Example 4

[0075] (1) AlCl3, NaOH, TPAOH, and ethanol were dissolved in 30 ml of deionized water as a modification solution. The molar ratio of the components in the modification solution was 1.0Al2O3:0.2Na2O:0.5TPAOH:0.05ethanol:30H2O. The solution was stirred at 25°C for 2 h to obtain a modification solution.

[0076] (2) Slowly add ZSM-5 molecular sieve powder to the modified solution and stir at 25°C for 6 hours, wherein the mass ratio of ZSM-5 powder to Al2O3 in the modified solution is maintained at 1:10; the above mixed solution is transferred to a polytetrafluoroethylene-lined stainless steel kettle, placed in a 150°C rotary oven, and modified at a stirring speed of 30 rpm for 40 hours. After centrifugation and separation and multiple washing, it is dried at 60°C for 12 hours and calcined at 550°C for 8 hours to obtain the modified product;

[0077] (3) placing the product obtained in step (2) in an ammonium nitrate solution and heating and stirring at 80° C. for 3 h to perform ion exchange, centrifuging, washing with water multiple times and drying, and then calcining at 500° C. for 6 h. This process is repeated twice to obtain an alumina-modified ZSM-5 molecular sieve;

[0078] (4) Add 2g Al2O3 to 100g deionized water, stir for 30min, slowly drop 0.1mol / L hydrochloric acid to adjust pH to 3, and continue stirring for 1h; then drop 20mL 1mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the obtained filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0079] (5) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of the ZSM-5 molecular sieve obtained in step (3) to obtain the catalyst of Comparative Example 4. The catalyst contained 0.5% Pt, 49.5% alumina, and 50% alumina-modified molecular sieve. The amounts of B acid (X and Y) of the alumina-modified ZSM-5 molecular sieve in the catalyst of Comparative Example 4 are shown in Table 1.

[0080] Comparative Example 5

[0081] (1) AlCl3, NaOH, TPAOH, and ethanol were dissolved in 30 ml of deionized water as a modification solution. The molar ratio of the components in the modification solution was 1.0Al2O3:0.2Na2O:0.5TPAOH:0.05ethanol:30H2O. The solution was stirred at 25°C for 2 h to obtain a modification solution.

[0082] (2) Slowly add ZSM-5 molecular sieve powder to the modified solution and stir at 25°C for 6 hours, wherein the mass ratio of ZSM-5 powder to Al2O3 in the modified solution is maintained at 1:20; the above mixed solution is transferred to a polytetrafluoroethylene-lined stainless steel kettle, placed in a 150°C rotary oven, and modified at a stirring speed of 30 rpm for 40 hours. After centrifugation and separation and multiple washing, it is dried at 60°C for 12 hours and calcined at 550°C for 8 hours to obtain the modified product;

[0083] (3) placing the product obtained in step (2) in an ammonium nitrate solution and heating and stirring at 80° C. for 3 h to perform ion exchange, centrifuging, washing with water multiple times and drying, and then calcining at 500° C. for 6 h. This process is repeated twice to obtain an alumina-modified ZSM-5 molecular sieve;

[0084] (4) Add 2g Al2O3 to 100g deionized water, stir for 30min, slowly drop 0.1mol / L hydrochloric acid to adjust pH to 3, and continue stirring for 1h; then drop 20mL 1mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the obtained filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0085] (5) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of the ZSM-5 molecular sieve obtained in step (3) to obtain the catalyst of Comparative Example 5. The catalyst contained 0.5% Pt, 49.5% alumina, and 50% alumina-modified molecular sieve. The amount of B acid (X and Y) of the alumina-modified ZSM-5 molecular sieve in the catalyst of Comparative Example 5 is shown in Table 1.

[0086] Comparative Example 6

[0087] (1) AlCl3, NaOH, TPAOH, and ethanol were dissolved in 30 ml of deionized water as a modification solution. The molar ratio of the components in the modification solution was 1.0Al2O3:0.2Na2O:0.5TPAOH:0.05ethanol:30H2O. The solution was stirred at 60°C for 2 h to obtain a modification solution.

[0088] (2) Slowly add ZSM-5 molecular sieve powder with a SiO2 / Al2O3 ratio of 60 to the modified solution and stir at 60°C for 6 hours, wherein the mass ratio of ZSM-5 powder to Al2O3 in the modified solution is maintained at 10:1; the above mixed solution is transferred to a polytetrafluoroethylene-lined stainless steel kettle, placed in a 150°C rotary oven, and modified at a stirring speed of 30 rpm for 40 hours. After centrifugation and separation and multiple washing, it is dried at 60°C for 12 hours and calcined at 550°C for 8 hours to obtain the modified product;

[0089] (3) placing the product obtained in step (2) in an ammonium nitrate solution and heating and stirring at 80° C. for 3 h to perform ion exchange, centrifuging, washing with water multiple times and drying, and then calcining at 500° C. for 6 h. This process is repeated twice to obtain an alumina-modified ZSM-5 molecular sieve;

[0090] (4) Add 2g of Al2O3 carrier to 100g of deionized water, stir for 30min, slowly drop 0.1mol / L hydrochloric acid to adjust pH to 3, and continue stirring for 1h; then drop 20mL of 1mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the obtained filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0091] (5) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of the ZSM-5 molecular sieve obtained in step (3) to obtain the catalyst of Comparative Example 6. The catalyst contained 0.5% Pt, 49.5% alumina, and 50% alumina-modified molecular sieve. The amount of B acid (X and Y) of the alumina-modified ZSM-5 molecular sieve in the catalyst of Comparative Example 6 is shown in Table 1.

[0092] Comparative Example 7

[0093] (1) AlCl3, NaOH, TPAOH, and ethanol were dissolved in 30 ml of deionized water as a modification solution. The molar ratio of each component in the modification solution was 1.0Al2O3:0.2Na2O:0.5TPAOH:0.05ethanol:30H2O. The solution was stirred at 30°C for 2 h to obtain a modification solution.

[0094] (2) The specific surface area is 350m 2 / g of pure silicon Silicalite-1 molecular sieve was slowly added to the modified solution and stirred at room temperature for 6 hours. The mass ratio of Silicalite-1 molecular sieve powder to Al2O3 in the modified solution was maintained at 15:1. The mixture was transferred to a polytetrafluoroethylene-lined stainless steel kettle and placed in a rotary oven at 120°C with stirring at 20 rpm for 24 hours. After centrifugation and multiple washing steps, the modified product was dried at 60°C for 12 hours and calcined at 550°C for 8 hours.

[0095] (3) placing the product obtained in step (2) in an ammonium nitrate solution and heating and stirring at 80° C. for 3 h to perform ion exchange, centrifuging, washing with water multiple times and drying, and then calcining at 500° C. for 6 h. This process is repeated twice to obtain an alumina-modified Silicalite-1 molecular sieve;

[0096] (4) Add 2g of Al2O3 carrier to 100g of deionized water, stir for 30min, slowly drop 0.1mol / L hydrochloric acid to adjust pH to 3, and continue stirring for 1h; then drop 20mL of 1mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the obtained filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0097] (5) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of the Silicalite-1 molecular sieve obtained in step (3) to obtain the catalyst of Comparative Example 7. The catalyst contained 0.5% Pt, 49.5% alumina, and 50% alumina-modified molecular sieve. The amount of B acid (X and Y) of the alumina-modified Silicalite-1 molecular sieve in the catalyst of Comparative Example 7 is shown in Table 1.

[0098] Example 1

[0099] (1) AlCl3, NaOH, TPAOH, and ethanol were dissolved in 30 ml of deionized water as a modification solution. The molar ratio of each component in the modification solution was 1.0Al2O3:0.2Na2O:0.5TPAOH:0.05ethanol:30H2O. The solution was stirred at 25°C for 2 h to obtain a modification solution.

[0100] (2) Slowly add ZSM-5 molecular sieve powder to the modified solution and stir at 25°C for 6 hours, wherein the mass ratio of ZSM-5 powder to Al2O3 in the modified solution is maintained at 10:1; the above mixed solution is transferred to a polytetrafluoroethylene-lined stainless steel kettle, placed in a 150°C rotary oven, and modified at a stirring speed of 30 rpm for 40 hours. After centrifugation and separation and multiple washing, it is dried at 60°C for 12 hours and calcined at 550°C for 8 hours to obtain the modified product;

[0101] (3) placing the product obtained in step (2) in an ammonium nitrate solution and heating and stirring at 80° C. for 3 h to perform ion exchange, centrifuging, washing with water multiple times and drying, and then calcining at 500° C. for 6 h. This process is repeated twice to obtain an alumina-modified ZSM-5 molecular sieve;

[0102] (4) Add 2g Al2O3 to 100g deionized water, stir for 30min, slowly drop 0.1mol / L hydrochloric acid to adjust pH to 3, and continue stirring for 1h; then drop 20mL 1mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the obtained filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0103] (5) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of the ZSM-5 molecular sieve obtained in step (3) to obtain the catalyst of Example 1. The catalyst had a Pt content of 0.5%, an alumina content of 49.5%, and an alumina-modified molecular sieve content of 50%. The amounts of B acid (X and Y) of the alumina-modified molecular sieve in the catalyst of Example 1 are shown in Table 1.

[0104] Example 2

[0105] (1) AlCl3, NaOH, TPAOH, and ethanol were dissolved in 30 ml of deionized water as a modification solution. The molar ratio of the components in the modification solution was 2.0Al2O3:0.4Na2O:0.65TPAOH:0.07ethanol:50H2O. The solution was stirred at 80°C for 2 h to obtain a modification solution.

[0106] (2) Slowly add ZSM-5 molecular sieve powder to the modified solution and stir at 80°C for 6 hours, wherein the mass ratio of ZSM-5 powder to Al2O3 in the modified solution is maintained at 10:1; the above mixed solution is transferred to a polytetrafluoroethylene-lined stainless steel kettle, placed in a rotary oven at 120°C, and modified at a stirring speed of 50 rpm for 96 hours. After centrifugation and separation and multiple washing, it is dried at 60°C for 12 hours and calcined at 550°C for 8 hours to obtain the modified product;

[0107] (3) placing the product obtained in step (2) in an ammonium nitrate solution and heating and stirring at 80° C. for 3 h to perform ion exchange, centrifuging, washing with water multiple times and drying, and then calcining at 500° C. for 6 h. This process is repeated twice to obtain an alumina-modified ZSM-5 molecular sieve;

[0108] (4) Add 2g Al2O3 to 100g deionized water, stir for 30min, slowly drop 0.1mol / L hydrochloric acid to adjust pH to 3, and continue stirring for 1h; then drop 400mL 1mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the obtained filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0109] (5) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of the ZSM-5 molecular sieve obtained in step (3) to obtain the catalyst of Example 2. The catalyst contained 10% Pt, 40% alumina, and 50% alumina-modified molecular sieve.

[0110] The amount of B acid (X and Y) of the alumina-modified molecular sieve in the catalyst of Example 2 is shown in Table 1.

[0111] Example 3

[0112] (1) Dissolve NaAlO2, NaOH, TPAOH, and ethanol in 30 ml of deionized water as a modification solution. The molar ratio of each component in the modification solution is 1.0Al2O3:0.25Na2O:0.55TPAOH:0.06ethanol:40H2O. Stir at room temperature at 25°C for 2 h to obtain a modification solution.

[0113] (2) Slowly add ZSM-5 molecular sieve powder to the modified solution and stir at room temperature for 6 hours, wherein the mass ratio of ZSM-5 powder to Al2O3 in the modified solution is maintained at 15:1; the above mixed solution is transferred to a polytetrafluoroethylene-lined stainless steel kettle, placed in a rotary oven at 120°C, and modified at a stirring speed of 50 rpm for 96 hours. After centrifugation and separation and multiple washing, it is dried at 60°C for 12 hours and calcined at 550°C for 8 hours to obtain the modified product;

[0114] (3) placing the product obtained in step (2) in an ammonium nitrate solution and heating and stirring at 80° C. for 3 h to perform ion exchange, centrifuging, washing with water multiple times and drying, and then calcining at 500° C. for 6 h. This process is repeated twice to obtain an alumina-modified ZSM-5 molecular sieve;

[0115] (4) Add 2g Al2O3 to 100g deionized water, stir for 30min, slowly drop 0.1mol / L hydrochloric acid to adjust pH to 3, and continue stirring for 1h; then drop 200mL 1mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the obtained filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0116] (5) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of the ZSM-5 molecular sieve obtained in step (3) to obtain the catalyst of Example 3. The catalyst had a Pt content of 5%, an alumina content of 45%, and a molecular sieve content of 50%. The amounts of B acid (X and Y) of the alumina-modified molecular sieve in the catalyst of Example 3 are shown in Table 1.

[0117] Example 4

[0118] (1) AlCl3, NaOH, CTBA, and ethanol were dissolved in 30 ml of deionized water to prepare a modification solution. The molar ratio of the components in the modification solution was 2.0Al2O3:0.15Na2O:0.15CTBA:0.03ethanol:20H2O. The solution was stirred at 80°C for 2 h to obtain a modification solution.

[0119] (2) Slowly add ZSM-5 molecular sieve powder to the modified solution and stir at 80°C for 6 hours, wherein the mass ratio of ZSM-5 powder to Al2O3 in the modified solution is maintained at 20:1; the above mixed solution is transferred to a polytetrafluoroethylene-lined stainless steel kettle, placed in a rotary oven at 120°C, and modified at a stirring speed of 20 rpm for 24 hours. After centrifugation and separation and multiple washing, it is dried at 60°C for 12 hours and calcined at 550°C for 8 hours to obtain the modified product;

[0120] (3) placing the product obtained in step (2) in an ammonium nitrate solution and heating and stirring at 80° C. for 3 h to perform ion exchange, centrifuging, washing with water multiple times and drying, and then calcining at 500° C. for 6 h. This process is repeated twice to obtain an alumina-modified ZSM-5 molecular sieve;

[0121] (4) Add 2g Al2O3 to 100g deionized water, stir for 30min, slowly drop 0.1mol / L hydrochloric acid to adjust pH to 3, and continue stirring for 1h; then drop 400mL 1mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the obtained filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0122] (5) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of the ZSM-5 molecular sieve obtained in step (3) to obtain the catalyst of Example 4. The catalyst contained 10% Pt, 40% alumina, and 50% molecular sieve. The amounts of B acid (X and Y) in the alumina-modified ZSM-5 molecular sieve in the catalyst of Example 4 are shown in Table 1.

[0123] Example 5

[0124] (1) AlCl3, NaOH, TPAOH, and ethanol were dissolved in 30 ml of deionized water as a modification solution. The molar ratio of each component in the modification solution was 1.0Al2O3:0.2Na2O:0.5TPAOH:0.05ethanol:30H2O. The solution was stirred at 25°C for 2 h to obtain a modification solution.

[0125] (2) Pure silicon Silicalite-1 molecular sieve was slowly added to the modified solution and stirred at 25°C for 6 hours, wherein the mass ratio of Silicalite-1 powder to Al2O3 in the modified solution was maintained at 15:1; the mixed solution was transferred to a polytetrafluoroethylene-lined stainless steel kettle, placed in a rotary oven at 120°C, and modified at a stirring speed of 20 rpm for 24 hours. After centrifugation and separation and multiple washing, it was dried at 60°C for 12 hours and calcined at 550°C for 8 hours to obtain the modified product;

[0126] (3) placing the product obtained in step (2) in an ammonium nitrate solution and heating and stirring at 80° C. for 3 h to perform ion exchange, centrifuging, washing with water multiple times and drying, and then calcining at 500° C. for 6 h. This process is repeated twice to obtain an alumina-modified Silicalite-1 molecular sieve;

[0127] (4) Add 2g Al2O3 to 100g deionized water, stir for 30min, slowly drop 0.1mol / L hydrochloric acid to adjust pH to 3, and continue stirring for 1h; then drop 20mL 1mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the obtained filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0128] (5) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of the Silicalite-1 molecular sieve obtained in step (3) to obtain the catalyst of Example 5. The catalyst had a Pt content of 0.5%, an alumina content of 49.5%, and a molecular sieve content of 50%. The amount of B acid (X and Y) of the alumina-modified Silicalite-1 molecular sieve in the catalyst of Example 5 is shown in Table 1.

[0129] Example 6

[0130] (1) AlCl3, NaOH, TPAOH, and ethanol were dissolved in 30 ml of deionized water as a modification solution. The molar ratio of the components in the modification solution was 2.0Al2O3:0.4Na2O:0.65TPAOH:0.07ethanol:50H2O. The solution was stirred at 80°C for 2 h to obtain a modification solution.

[0131] (2) Pure silicon Silicalite-1 molecular sieve was slowly added to the modified solution and stirred at 80°C for 6 hours, wherein the mass ratio of Silicalite-1 raw powder to Al2O3 in the modified solution was maintained at 5:1; the above mixed solution was transferred to a polytetrafluoroethylene-lined stainless steel kettle, placed in a rotary oven at 150°C, and modified at a stirring speed of 50 rpm for 72 hours. After centrifugation and separation and multiple washing, it was dried at 60°C for 12 hours and calcined at 550°C for 8 hours to obtain the modified product;

[0132] (3) placing the product obtained in step (2) in an ammonium nitrate solution and heating and stirring at 80° C. for 3 h to perform ion exchange, centrifuging, washing with water multiple times and drying, and then calcining at 500° C. for 6 h. This process is repeated twice to obtain an alumina-modified Silicalite-1 molecular sieve;

[0133] (4) Add 2g of Al2O3 carrier to 100g of deionized water, stir for 30min, slowly drop 0.1mol / L hydrochloric acid, adjust pH to 3, and continue stirring for 1h; then drop 200mL of 1mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0134] (5) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of the Silicalite-1 molecular sieve obtained in step (3) to obtain the catalyst of Example 6. The catalyst had a Pt content of 5%, an alumina content of 45%, and a molecular sieve content of 50%. The amount of B acid (X and Y) of the alumina-modified Silicalite-1 molecular sieve in the catalyst of Example 6 is shown in Table 1.

[0135] Example 7

[0136] (1) AlCl3, NaOH, TPAOH, and ethanol were dissolved in 30 ml of deionized water as a modification solution. The molar ratio of each component in the modification solution was 0.05Al2O3:0.15Na2O:0.15TPAOH:0.03ethanol:20H2O. The solution was stirred at 60°C for 2 h to obtain a modification solution.

[0137] (2) Pure silicon Silicalite-1 molecular sieve was slowly added to the modified solution and stirred at 60°C for 6 hours, wherein the mass ratio of Silicalite-1 raw powder to Al2O3 in the modified solution was maintained at 5:1; the above mixed solution was transferred to a polytetrafluoroethylene-lined stainless steel kettle, placed in an 80°C rotary oven, and modified at a stirring speed of 50 rpm for 96 hours. After centrifugation and separation and multiple washing, it was dried at 60°C for 12 hours and calcined at 550°C for 8 hours to obtain the modified product;

[0138] (3) placing the product obtained in step (2) in an ammonium nitrate solution and heating and stirring at 80° C. for 3 h to perform ion exchange, centrifuging, washing with water multiple times and drying, and then calcining at 500° C. for 6 h. This process is repeated twice to obtain an alumina-modified Silicalite-1 molecular sieve;

[0139] (4) Add 2g of Al2O3 carrier to 100g of deionized water, stir for 30min, slowly drop 0.1mol / L hydrochloric acid to adjust pH to 3, and continue stirring for 1h; then drop 400mL of 1mg Pt / mL H2PtCl6·6H2O solution, stirred for 3h, filtered and washed with 1.5L deionized water, and the filter cake was dried in an 80℃ oven for 12h, and then air-treated at 500℃ for 4h to obtain Pt / Al2O3 component;

[0140] (5) 1 g of the Pt / Al2O3 component was physically mixed with 1 g of the Silicalite-1 molecular sieve obtained in step (3) to obtain the catalyst of Example 7. The catalyst had a Pt content of 10%, an alumina content of 40%, and a molecular sieve content of 50%. The amount of B acid (X and Y) of the alumina-modified Silicalite-1 molecular sieve in the catalyst of Example 7 is shown in Table 1.

[0141] Example 8:

[0142] The catalysts prepared in Examples 1-7 and Comparative Examples 1-7 were pressed into tablets and sieved through 20-40 mesh. 0.3 g of the catalyst was placed in a fixed bed reactor. The temperature was raised from room temperature to 450°C at a rate of 10°C / min under a hydrogen atmosphere. After reduction for 2 h, the temperature was cooled to the reaction temperature and the catalyst was evaluated.

[0143] The catalyst evaluation conditions were as follows: temperature 200 °C, pressure 2.0 MPa, molar ratio of hydrogen to n-hexane 6.0, mass space velocity of n-hexane 4.5 h -1 The evaluation results of each catalyst are shown in Table 2.

[0144] Table 1 Results of the B acid amount (X and Y) of the alumina-modified molecular sieve in each catalyst

[0145] Example No. X (mmol / g) Y (mmol / g) Y / X Comparative Example 1 0.09 0.0003 0.003 Comparative Example 2 0.002 0.00 0.00 Comparative Example 3 0.094 0.004 0.04 Comparative Example 4 0.12 0.005 0.042 Comparative Example 5 0.15 0.003 0.02 Comparative Example 6 0.156 0.0008 0.005 Comparative Example 7 0.00 0.00 -- Example 1 0.12 0.03 0.25 Example 2 0.16 0.07 0.44 Example 3 0.13 0.04 0.31 Example 4 0.10 0.01 0.10 Example 5 0.08 0.07 0.88 Example 6 0.13 0.12 0.92 Example 7 0.22 0.22 1.00

[0146] Table 2 Evaluation results of catalysts obtained in each case

[0147]

[0148]

[0149] The above embodiments are merely examples for the purpose of clearly illustrating the technical solutions of the present invention and are not intended to limit the present invention. Those skilled in the art will appreciate that other variations or modifications may be made based on the above descriptions. This list of all possible implementations is not exhaustive, and any obvious variations or modifications that may be derived from these variations are still within the scope of protection of the present invention.

Claims

1. An alkane isomerization catalyst comprising an active metal, alumina, and an alumina-modified molecular sieve, wherein the molecular sieve is selected from at least one of a ZSM-5 molecular sieve and a pure silicon-based molecular sieve; the alumina-modified molecular sieve has an external surface Br acid content of 0.01 to 0.25 mmol / g; and the pure silicon-based molecular sieve is selected from one or more of a pure silicon MCM-41 molecular sieve, a Silicalite-1 molecular sieve, a pure silicon Beta molecular sieve, a pure silicon HMS molecular sieve, and a pure silicon MCF-17 molecular sieve; In the catalyst, the mass ratio of alumina-modified molecular sieve to alumina is 8:1 to 1:8; In the catalyst, the content of the active metal is 0.01% to 10.0% based on the weight of the catalyst; The preparation method of the catalyst comprises the following steps: (1) Mixing an aluminum source, an alkali source, a surfactant, ethanol and water to obtain a modified solution; (2) adding the molecular sieve raw powder to the modified solution obtained in step (1), mixing and transferring the mixture to a reactor, performing modification treatment, drying, and roasting to obtain a modified product; (3) exchanging the modified product obtained in step (2) with ammonium ions and calcining to obtain an alumina-modified molecular sieve; (4) adding the precursor solution containing the active metal to the suspension of the alumina binder, mixing them evenly, and heat treating them to obtain active metal / Al2O3; (5) mixing and grinding the active metal / Al2O3 obtained in step (4) and the modified molecular sieve obtained in step (3) to obtain the alkane isomerization catalyst; In step (2), the mass ratio of the molecular sieve to the Al2O3 in the modified solution is 20:1 to 2:1; The modification temperature in step (2) is 80~200°C.

2. The catalyst according to claim 1, characterized in that The alumina-modified molecular sieve is an alumina-modified ZSM-5 molecular sieve, and the ratio of the amount of Brønsted acid on the outer surface to the total amount of Brønsted acid is 0.10-0.

50.

3. The catalyst according to claim 1, characterized in that In the catalyst, the mass ratio of the alumina-modified molecular sieve to alumina is 3:1 to 1:

3.

4. The catalyst according to claim 1, characterized in that In the catalyst, the mass ratio of the alumina-modified molecular sieve to alumina is 1.5:1 to 1:1.

5.

5. The catalyst according to claim 1 or 3, characterized in that Based on the weight of the catalyst, the content of the active metal is 0.5% to 10.0%.

6. The catalyst according to claim 1, characterized in that The active metal is one or more of Pt, Pd, Ir, Ni, and Mo.

7. The catalyst according to claim 1, characterized in that The active metal is Pt.

8. The catalyst according to claim 1, characterized in that The pure silicon molecular sieve is one or more of pure silicon MCM-41 molecular sieve and Silicalite-1 molecular sieve.

9. A method for preparing the catalyst according to any one of claims 1 to 8, comprising the following steps: (1) Mixing an aluminum source, an alkali source, a surfactant, ethanol and water to obtain a modified solution; (2) adding the molecular sieve raw powder to the modified solution obtained in step (1), mixing and transferring the mixture to a reactor, performing modification treatment, drying, and roasting to obtain a modified product; (3) exchanging the modified product obtained in step (2) with ammonium ions and calcining to obtain an alumina-modified molecular sieve; (4) adding the precursor solution containing the active metal to the suspension of the alumina binder, mixing them evenly, and heat treating them to obtain active metal / Al2O3; (5) The active metal / Al2O3 obtained in step (4) and the modified molecular sieve obtained in step (3) are mixed and ground to obtain the alkane isomerization catalyst.

10. The preparation method according to claim 9, characterized in that In step (1), the molar ratio of the aluminum source calculated as Al2O3, the alkali source calculated as oxide, the surfactant, ethanol and water is Al2O3:M2O:surfactant:ethanol:H2O=0.05~2.00:0.15-0.40:0.15~0.65:0.03~0.07:20~50.

11. The preparation method according to claim 9, characterized in that In step (1), the aluminum source is selected from one or more of aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum carbonate, aluminum acetate, aluminum phosphate, aluminum oxide, aluminum isopropoxide, aluminum sol or pseudo-boehmite; and / or the surfactant is selected from one or more of tetrapropylammonium hydroxide, tetrapropylammonium bromide, hexadecyltrimethylammonium bromide, triethylamine and its homologues or ethylenediamine and its homologues; and / or the alkali source is selected from at least one of NaOH, KOH, Na2CO3, K2CO3, NaHCO3, and KHCO3.

12. The preparation method according to claim 9, characterized in that In step (1), the aluminum source is one or more of aluminum chloride, aluminum isopropoxide or aluminum sol; and / or the surfactant is one or more of tetrapropylammonium hydroxide, tetrapropylammonium bromide or hexadecyltrimethylammonium bromide; and / or the alkali source is NaOH.

13. The preparation method according to claim 9, characterized in that In step (1), the aluminum source is aluminum chloride.

14. The preparation method according to claim 9, characterized in that In step (2), the mass ratio of the molecular sieve to the Al2O3 in the modified solution is 20:1 to 2:

1.

15. The preparation method according to claim 9, characterized in that In step (2), the modification treatment is carried out in a rotary oven at a rotation speed of 15 to 50 rpm, a modification temperature of 80 to 200°C, and a modification time of 10 to 120 hours; and / or, in step (2), the roasting conditions are as follows: a roasting temperature of 500 to 700°C, and a roasting time of 6 to 12 hours; and / or, in step (4), the heat treatment conditions are as follows: a heat treatment temperature of 350 to 700°C, and a heat treatment time of 1.0 to 8.0 hours, and the heat treatment atmosphere can be an oxygen atmosphere, a reducing atmosphere, or an inert atmosphere.

16. The preparation method according to claim 9, characterized in that In step (2), the modification temperature is 80~150 °C, and the modification time is 24 h~96 h.

17. The preparation method according to claim 9, characterized in that In step (4), the metal concentration of the precursor solution is 0.001 mg / mL to 2.50 mg / mL; and / or, in step (5), the mass ratio of the active metal / Al2O3 to the alumina-modified molecular sieve is 1:9 to 9:

1.

18. Use of the catalyst according to any one of claims 1 to 8 in catalyzing alkane isomerization reactions.

19. The use according to claim 18, characterized in that The reaction conditions of the alkane isomerization reaction are as follows: reaction temperature of 180-300 °C, reaction pressure of 1.0-3.0 MPa, molar ratio of hydrogen to normal alkane of 2.0-7.0, mass space velocity of alkane of 2.5-8.0 h -1 .

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