A molecular sieve catalyst for benzene alkylation and its preparation method and application

Abstract

The invention discloses a molecular sieve catalyst for benzene alkylation, a preparation method and an application thereof. In the catalyst, the molecular sieve crystal contains three kinds of nearly spherical cavities with size distribution, and the diameter distribution range of the circles corresponding to the vertical projections of the three cavities from top to bottom is respectively within 10-30nm, 40-50nm and 60-90nm, and the proportion of the number of the three cavities is 20%-40%, 50%-75% and 5%-10%, respectively. The present invention prepares a molecular sieve catalyst containing cavities of suitable size and proportion inside the molecular sieve crystal in a more economical method, and the prepared catalyst is particularly suitable for the benzene alkylation process, and has high activity, selectivity and stability.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic chemistry and chemical engineering, and in particular relates to a molecular sieve catalyst for benzene alkylation and a preparation method and application thereof. Background Art

[0002] Benzene alkylation products, such as ethylbenzene, are important basic organic raw materials with a wide range of uses and play an important role in the development of the national economy.

[0003] The key technology of benzene alkylation is to develop catalysts with high activity, high selectivity and high stability. The effective component of the catalyst is molecular sieve, which has a pure microporous structure. In the actual reaction process, there are problems such as long diffusion path and slow diffusion rate, which will lead to reduced activity, reduced selectivity and shortened life of the catalyst. Introducing cavities inside the microporous molecular sieve can effectively shorten the diffusion path of the reaction molecules, increase the diffusion rate of the reaction molecules, and the generated target products can also quickly diffuse out of the reaction system to avoid side reactions. It can also effectively inhibit the generation of heavy components and slow down the rate of carbon deposition, thereby greatly improving the activity, selectivity and stability of the catalyst.

[0004] CN 201410563714.3 discloses a MCM-22 molecular sieve with a cavity aggregation morphology and a preparation method thereof, wherein the molecular sieve has a size of 5-30 μm, the cavity wall is composed of MCM-22 small crystals of 20-200 nm, and the cavity wall thickness is 0.2-3.0 μm. The preparation method is as follows: (1) uniformly mixing an aluminum source, a silicon source, an alkali, water, polyethylene glycol, sodium lignin sulfonate and a template; (2) continuing to mix the mixture under the combined action of ultrasonic dispersion and mechanical stirring; (3) crystallizing the material obtained in step (2), and the product is washed, dried and roasted to obtain an MCM-22 molecular sieve with a cavity aggregation morphology. However, the molecular sieve cavity prepared by this method is not the true internal cavity of the molecular sieve crystal, but is obtained by aggregating and stacking small-grain MCM-22 molecular sieves, which belongs to the external cavity of the molecular sieve crystal. The external cavity of the crystal has little effect on improving the diffusion performance inside the molecular sieve crystal. In addition, the cavity morphology and size obtained by this method are irregular, which leads to a longer molecular diffusion path during the reaction and the catalytic performance of the molecular sieve is also affected accordingly.

[0005] CN 201811515890.4 discloses a hollow multi-level pore Beta molecular sieve and a preparation method thereof, mainly comprising the following steps: S1, dissolving a double-headed quaternary ammonium salt surfactant N2-p-N2, sodium hydroxide, and sodium metaaluminate in a mixed solution of water and anhydrous ethanol, stirring and mixing to obtain a mixed solution; S2, dripping ethyl orthosilicate into the mixed solution obtained in step S1 under stirring conditions, and continuing to stir until a gel solution is formed; S3, transferring the gel solution obtained in step S2 to an autoclave for hydrothermal crystallization, washing and filtering with water after crystallization, and then vacuum drying; S4, placing the dried product of step S3 in a muffle furnace for roasting to obtain a hollow multi-level pore Beta molecular sieve. The method uses a cut double quaternary amphiphilic small molecule to hydrothermally synthesize a hollow multi-level pore Beta molecular sieve in one step. The hollow multi-level pore Beta molecular sieve prepared by this method has a large hollow cavity and a thin mesopore wall. The molecular sieve is very easy to break in the actual industrial application process. In addition, the molecular sieve is used as a catalyst, and its bulk density is low, resulting in a small amount of catalyst loading. If used in an industrial device, the reaction performance will be greatly reduced. In addition, the structure of the diquaternary ammonium head amphiphilic molecular template agent used in this method is quite complex, expensive and difficult to obtain, which is extremely unfavorable for large-scale industrial application.

[0006] Therefore, how to more economically prepare molecular sieve catalysts containing cavities, and make the cavities have the required morphology and size, and the size and quantity ratio of the cavities have a suitable compatibility relationship, will be more conducive to improving the reaction performance of the molecular sieve catalyst. Summary of the invention

[0007] The present invention aims to provide a molecular sieve catalyst for benzene alkylation and a preparation method thereof and its application in alkylation reaction, so as to improve the activity, selectivity and stability of benzene alkylation reaction.

[0008] The first aspect of the present invention provides a molecular sieve catalyst for benzene alkylation, wherein the molecular sieve crystals in the catalyst contain three types of nearly spherical cavities with size distributions, the diameter distribution ranges of the circles corresponding to the vertical projections of the three cavities from top to bottom are within 10-30nm, 40-50nm and 60-90nm, respectively, and the proportions of the number of the three cavities are 20%-40%, 50%-75% and 5%-10%, respectively.

[0009] In the above technical solution, preferably, the internal grain size of the molecular sieve crystal is 200-500nm.

[0010] In the above technical solution, preferably, the catalyst is a binder-free molecular sieve catalyst, preferably, the molecular sieve is a silicon-aluminum molecular sieve having a twelve-membered ring pore structure, and more preferably, the molecular sieve is a Beta molecular sieve.

[0011] In the above technical solution, preferably, the total specific surface area of ​​the catalyst is 700-850m 2 ·g -1 , with a total pore volume of 0.9-1.2 cm 3 ·g -1 .

[0012] In the above technical solution, preferably, the mechanical strength of the catalyst is 60-120 N / cm, more preferably, the mechanical strength of the catalyst is 70-100 N / cm.

[0013] In the above technical solution, preferably, the bulk density of the catalyst is 0.52-0.58 g·cm -3 .

[0014] In the above technical solution, preferably, the SiO2 / Al2O3 molar ratio of the catalyst is 12-40.

[0015] The second aspect of the present invention provides a method for preparing a molecular sieve catalyst for benzene alkylation, comprising the following steps:

[0016] (a) treating the molecular sieve with an acid and an ammonium salt solution to obtain a mixture E;

[0017] (b) The mixture E is contacted with a mixed organic base to obtain a mixture F, and the mixture F is treated at 130-150° C. for 24-72 hours, and then washed, dried and calcined to obtain a molecular sieve catalyst for benzene alkylation.

[0018] In the above technical solution, preferably, the acid used for the acid treatment in step (a) is one or more of hydrochloric acid, sulfuric acid, and nitric acid, and the acid used for the acid treatment is an aqueous solution of the acid with a mass concentration of 0.1%-0.5%.

[0019] In the above technical solution, preferably, in step (a), the ammonium salt is one or more of ammonium chloride, ammonium nitrate and ammonium sulfate, and the ammonium salt solution is an aqueous solution with a mass concentration of 5%-20%.

[0020] In the above technical solution, preferably, the acid treatment condition in step (a) is 20-50° C. for 1-2 hours. The acid treatment is preferably carried out in a closed space.

[0021] In the above technical solution, preferably, the ammonium salt solution treatment condition in step (a) is 20-50° C. for 1-2 hours. Preferably, the ammonium salt solution treatment is carried out in a closed space.

[0022] In the above technical solution, preferably, the acid treatment or ammonium salt solution treatment is followed by washing and drying. The washing and drying can be carried out by conventional methods. For example, washing can be carried out by washing with deionized water until the pH value of the solution is 7-7.5. The drying conditions can be as follows: the drying temperature is 120-200°C and the drying time is 10-24 hours.

[0023] In the above technical solution, preferably, the weight ratio of the acid solution used for the acid treatment in step (a) to the molecular sieve is (1.5-10):1.

[0024] In the above technical solution, preferably, the weight ratio of the ammonium salt solution and the molecular sieve used in the ammonium salt solution treatment in step (a) is (1.5-10):1.

[0025] In the above technical solution, preferably, the mixed organic base in step (b) is a mixed organic base aqueous solution with a mass concentration of 10%-20%; the mass ratio of the mixed organic base aqueous solution to the mixture E is (1.5-10):1.

[0026] In the above technical solution, preferably, the mixed organic base described in step (b) is a mixed alkali aqueous solution of tetraethylammonium hydroxide and at least two other different quaternary ammonium bases, and the other quaternary ammonium bases have the structural formula Wherein R1, R2, R3 and R4 are each independently selected from n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, benzyl or phenethyl, and R1, R2, R3 and R4 may be the same or different.

[0027] In the above technical solution, preferably, the mass ratio of tetraethylammonium hydroxide to the total amount of other quaternary ammonium bases in step (b) is (5-8):1.

[0028] In the above technical solution, preferably, the mass proportion of each quaternary ammonium base in other quaternary ammonium bases in step (b) is 20%-60%.

[0029] In the above technical solution, preferably, the washing, drying and roasting in step (b) can be carried out by any conventional method. For example, washing is carried out by washing with deionized water until the pH value of the solution is 7-7.5; the drying conditions can be as follows: the drying temperature is 120-200°C and the drying time is 10-24 hours; the roasting conditions can be as follows: the roasting temperature is 500-600°C and the roasting time is 5-10 hours.

[0030] In the above technical solution, the molecular sieve is preferably a binder-free molecular sieve.

[0031] In the above technical solution, the binder-free molecular sieve preparation process preferably comprises the following steps:

[0032] (1) contacting a first template, a silicon source, a first aluminum source, and water to obtain a mixture A;

[0033] The molar ratios of the first template, silicon source, first aluminum source and water are respectively: first template: silicon source = (0.2-0.6): 1; silicon source: first aluminum source = (12-40): 1, water: silicon source = (10-15): 1, wherein the silicon source is calculated as SiO2, and the first aluminum source is calculated as Al2O3;

[0034] (2) contacting mixture A, silicon powder and a second aluminum source to obtain mixture B;

[0035] The ratios of the mixture A, silicon powder and the second aluminum source are as follows: the weight ratio of the mixture A to the silicon powder is (0.6-1.0):1; the molar ratio of the silicon powder to the second aluminum source is (12-40):1; the silicon powder is calculated as SiO2, and the second aluminum source is calculated as Al2O3;

[0036] (3) forming the mixture B to obtain a mixture C;

[0037] (4) contacting the mixture C, the fluoride and the second template to obtain a mixture D, and washing, drying and calcining the mixture D to obtain a binder-free molecular sieve;

[0038] The weight ratio of the fluoride to the mixture C is (0.01-0.03):1, and the weight ratio of the second template to the mixture C is (1.5-3):1.

[0039] In the above technical scheme, preferably, the first template described in step (1) is tetraethylammonium hydroxide; the silicon source is one or more of water glass, silica sol, white carbon black, and tetraethyl silicate; the first aluminum source is one or more of sodium aluminate, pseudo-boehmite, aluminum chloride, aluminum nitrate, and aluminum sulfate, and more preferably, the first aluminum source is one or more of sodium aluminate and pseudo-boehmite.

[0040] In the above technical scheme, preferably, in step (1), the process of obtaining mixture A by contacting the first template, the silicon source, the first aluminum source and water is: stirring the first template, the silicon source, the first aluminum source and water in a closed container, the stirring time is 5h-12h, and the stirring temperature is 130-170°C.

[0041] In the above technical solution, preferably, the silicon powder in step (2) is silicon dioxide with a size distribution of 5-10 μm; the second aluminum source is a mixture of sodium aluminate and pseudo-boehmite, and the molar ratio of sodium aluminate and pseudo-boehmite is calculated as Al2O3: (1-2):1.

[0042] In the above technical solution, preferably, in step (3), mixture B is formed into mixture C. Mixture C can be made into strips as needed, and its cross-section is circular, gear-shaped, clover-shaped, four-leaf clover-shaped or honeycomb-shaped. The diameter of mixture C is 1.0-2.2 mm and the length is 2-4 mm.

[0043] In the above technical solution, preferably, the fluoride in step (4) is one or more of ammonium fluoride, ammonium fluorosilicate, and hydrofluoric acid, and the second template is tetraethylammonium hydroxide;

[0044] In the above technical solution, preferably, in step (4), the process of contacting the mixture C, the fluoride and the second template to obtain the mixture D is: treating the mixture C, the fluoride and the second template in a closed space at 130-170° C. for 48-72 hours, and then washing, drying and calcining to remove organic matter.

[0045] In the above technical scheme, the washing, drying and roasting can be carried out by conventional methods. For example, washing can be carried out with deionized water until the pH value of the solution is 7-7.5; for example, the drying conditions can be as follows: the drying temperature is 120-200°C and the drying time is 10-24 hours; the roasting conditions can be as follows: the roasting temperature is 500-600°C and the roasting time is 5-10 hours.

[0046] The third aspect of the present invention provides a use of the aforementioned molecular sieve catalyst in the alkylation reaction of benzene and olefins.

[0047] In the above technical solution, the olefin is preferably ethylene or other mixed gases containing ethylene.

[0048] In the above technical scheme, the preferred conditions for the benzene alkylation reaction are as follows: reaction temperature is 120-220°C, pressure is 1.5-5.0 MPa, ethylene mass space velocity is 0.2-5.0 h -1 , the molar ratio of benzene to ethylene is 1-10.

[0049] The molecular sieve catalyst for benzene alkylation of the present invention has the following beneficial effects:

[0050] 1. It has been found through research that diffusion performance plays a vital role in benzene alkylation catalysts. For molecular sieve catalysts, if the molecular sieve crystals contain cavities of suitable size and proportion, the internal diffusion problem in the alkylation reaction process can be effectively solved, the diffusion rate of the reaction molecules can be increased, and the conversion rate can be effectively improved. In addition, the generated target product can quickly diffuse out of the reaction system, inhibit the occurrence of side reactions, and improve the selectivity of the target product. At the same time, the rate of carbon deposition can be slowed down and the service life of the catalyst can be increased. The molecular sieve crystals in the catalyst of the present invention contain cavities of specific size distribution and have a specific proportional relationship, which is particularly suitable for benzene alkylation reactions.

[0051] 2. The catalyst of the present invention is preferably a binder-free catalyst, which does not contain any inert components, completely eliminating the negative effects of the inert components on the dilution of the active components of the molecular sieve and the clogging of the micropores of the molecular sieve, and further improving the activity, selectivity and stability of the catalyst in the alkylation reaction process of ethylbenzene.

[0052] 3. The catalyst of the present invention has the characteristics of high specific surface area, high pore volume, high mechanical strength and suitable bulk density, and is particularly suitable for industrial benzene alkylation reaction devices. In addition, the mixed organic base used in the present invention is cheap and easily available, and is suitable for large-scale industrial production.

[0053] 4. When the catalyst of the present invention is used for the alkylation reaction of benzene and ethylene to produce ethylbenzene, under the reaction conditions of a low molar ratio of benzene to ethylene, the ethylene conversion rate is greater than 99.9%, the ethyl selectivity in the alkylation product is greater than 99.5%, and the mass content of polyethylbenzene is 5-10%. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 The XRD spectrum of the molecular sieve catalyst for alkylation to ethylbenzene prepared in Example 1 of the present invention;

[0055] Figure 2 This is a TEM photo of the molecular sieve catalyst for alkylation to ethylbenzene prepared in Example 1 of the present invention;

[0056] Figure 3 The XRD spectrum of the molecular sieve catalyst for alkylation to ethylbenzene prepared in Example 2 of the present invention;

[0057] Figure 4 TEM photo of the catalyst prepared in Comparative Example 1;

[0058] Figure 5 This is the TEM photo of the catalyst prepared in Comparative Example 2. DETAILED DESCRIPTION

[0059] The present invention is described in detail below in conjunction with specific implementation modes, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0060] The cavity size and distribution of the catalyst for preparing ethylbenzene by alkylation in the present invention are obtained by analyzing TEM photos.

[0061] In the present invention, the total specific surface area and the total pore volume are obtained by nitrogen adsorption and desorption test; the mechanical strength is obtained by using an intelligent particle strength tester; and the SiO2 / Al2O3 molar ratio is obtained by ICP test.

[0062] In the present invention, the XRD spectrum of the catalyst was obtained by using the Ultima IV X-ray powder diffractometer of Rigaku Corporation of Japan. The voltage was selected as 35 kV, the current was selected as 30 mA, and the scanning speed was 1°·min -1 . When scanning at a small angle, the 2θ angle is 1-5°, and when scanning at a wide angle, the 2θ angle is 5-80°

[0063] In the present invention, a G2F30 transmission electron microscope produced by FEI Company of the United States is used to obtain TEM photos of the catalyst. Before the test, the sample to be tested needs to be ground for 1-5 minutes, and then a large amount of ethanol is added to disperse it evenly by ultrasonic. The suspension is added to the copper mesh, and the test can be carried out after the ethanol is completely evaporated.

[0064] In the present invention, the BEL-MAX specific surface and pore size analyzer produced by BELSORP of Japan is used to test the nitrogen adsorption and desorption isotherms of the catalyst at liquid nitrogen temperature, and the total specific surface area and total pore volume are calculated using the BET equation.

[0065] In the present invention, the mechanical strength of the catalyst is tested by using the DLIII intelligent particle strength tester of Dalian Penghui Technology Development Co., Ltd. The length of the tested catalyst is 5 mm and it is placed horizontally on the tester to test the maximum pressure the catalyst withstands when it is broken. After testing the crushing strength of 20 catalysts, the average value is taken.

[0066] In the present invention, the bulk density of the catalyst is measured using a 1000 ml graduated cylinder as the container, and the actual weight of the added catalyst (unit: g) is divided by the actual volume, and the unit is g·cm -3 .

[0067] In the present invention, Kontron Model S-35 ICP-AES analyzer is used to perform ICP testing to obtain silicon-to-aluminum ratio data.

[0068] [Example 1]

[0069] This embodiment is used to synthesize a molecular sieve catalyst for alkylation to produce ethylbenzene. The specific preparation process is as follows: 84.2 grams of tetraethylammonium hydroxide (aqueous solution with a concentration of 35wt%), 208.3 grams of tetraethyl silicate, 21.25 grams of sodium aluminate (with an Al2O3 mass content of 40%) and 180 grams of water are mixed evenly, and stirred in a closed container at 130°C for 12 hours to obtain a mixture A1. 120 grams of the mixture A1, 200 grams of silicon powder, 35.4 grams of sodium aluminate (with an Al2O3 mass content of 40%) and 20.2 grams of pseudo-boehmite (with an Al2O3 mass content of 70%) are contacted to obtain a mixture B1. B1 is extruded by adding an appropriate amount of deionized water to obtain a mixture C1 (C1 is cylindrical with a diameter of 1.8mm and a length of 2-3mm). 1 g of ammonium fluoride, 150 g of tetraethylammonium hydroxide and 100 g of mixture C1 were treated at 130° C. for 72 hours in a closed space, then washed with deionized water until the pH value was 7.5, dried at 150° C. for 15 hours, and calcined at 550° C. for 6 hours in an air atmosphere to obtain mixture D1. 100 g of mixture D1 and 150 g of 0.1% hydrochloric acid aqueous solution were treated at 20° C. for 1 hour in a closed space, then the acid solution was poured out, and 150 g of 5% ammonium nitrate salt solution was added and treated at 20° C. for 1 hour in a closed space, then washed with deionized water until the pH value was 7.5, and dried at 150° C. for 15 hours to obtain mixture E1. 50 g of the mixture E1 and 75 g of an organic base solution with a mass concentration of 20% (the solution contains three organic bases, tetraethylammonium hydroxide, di-n-pentyldibenzhydrylammonium hydroxide and tri-n-hexylmonoethylammonium hydroxide, with the mass proportions of the three being 84%, 8% and 8% respectively) are mixed evenly to obtain a mixture F1. The mixture F1 is treated at 130° C. for 72 hours in a closed space, and then washed with deionized water until the pH value of the solution is 7, dried at 120° C. for 24 hours, and calcined at 550° C. for 5 hours to obtain a molecular sieve catalyst G1 for alkylation to ethylbenzene.

[0070] The XRD spectrum of alkylation catalyst G1 for ethylbenzene is shown in Figure 1 As shown in Figure 1, it has typical Beta molecular sieve diffraction peaks. Figure 2 As shown, the molecular sieve crystal contains three kinds of nearly spherical cavities with different sizes. The diameter distribution ranges of the circles corresponding to the vertical projections of the three cavities from top to bottom are 22-28nm, 42-48nm and 85-88nm, respectively. The proportions of the three cavities are 22%, 73% and 5%, respectively. Through testing, the total specific surface area of ​​the alkylation catalyst G1 is 790m 2 ·g -1 , with a total pore volume of 1.1 cm 3 ·g -1, mechanical strength is 85N / cm, bulk density is 0.54g·cm -3 The SiO2 / Al2O3 molar ratio of the alkylation catalyst G1 to ethylbenzene was found to be 13.2 by ICP test.

[0071] [Example 2]

[0072] This embodiment is used to synthesize a molecular sieve catalyst for alkylation to produce ethylbenzene. The specific preparation process is as follows: 152 grams of tetraethylammonium hydroxide (aqueous solution with a concentration of 35wt%), 60 grams of white carbon black, 7.6 grams of pseudo-boehmite (with an Al2O3 mass content of 70%) and 200 grams of water are mixed evenly, and stirred at 150°C for 10 hours in a closed container to obtain a mixture A2. 120 grams of the mixture A2, 150 grams of silicon powder, 17 grams of sodium aluminate (with an Al2O3 mass content of 40%) and 4.8 grams of pseudo-boehmite (with an Al2O3 mass content of 70%) are contacted to obtain a mixture B2. B2 is extruded by adding an appropriate amount of deionized water to obtain a mixture C2 (C2 is a four-leaf clover shape with a diameter of 1.5mm and a length of 3-4mm). 2 g of hydrofluoric acid, 200 g of tetraethylammonium hydroxide and 100 g of mixture C2 were treated at 150° C. for 56 hours in a closed space, then washed with deionized water until the pH value was 7.5, dried at 150° C. for 15 hours, and calcined at 550° C. for 6 hours in an air atmosphere to obtain mixture D2. 100 g of mixture D2 and 500 g of 0.3% hydrochloric acid aqueous solution were treated at 30° C. for 2 hours in a closed space, then the acid solution was poured out, and 200 g of 10% ammonium sulfate salt solution was added and treated at 40° C. for 2 hours in a closed space, then washed with deionized water until the pH value was 7.5, and dried at 150° C. for 15 hours to obtain mixture E2. 50 grams of mixture E2 and 200 grams of an organic base solution with a mass concentration of 15% (the solution contains five organic bases, namely tetraethylammonium hydroxide, tetra-n-heptylammonium hydroxide, tetra-n-octylammonium hydroxide, di-n-octyldiphenylmethylammonium hydroxide and diphenylmethyldiphenylethylammonium hydroxide, with the mass proportions of the five being 84%, 4%, 4%, 4% and 4% respectively) are mixed evenly to obtain mixture F2. Mixture F2 is treated at 140° C. for 48 hours in a closed space, and then washed with deionized water until the pH value of the solution is 7, dried at 120° C. for 24 hours, and calcined at 550° C. for 5 hours to obtain a molecular sieve catalyst G2 for alkylation to ethylbenzene.

[0073] The XRD spectrum of alkylation catalyst G2 for ethylbenzene is shown in Figure 3As shown, it has a typical Beta molecular sieve diffraction peak. The molecular sieve crystal contains three kinds of nearly spherical cavities with different size distributions. The diameter distribution ranges of the circles corresponding to the vertical projections of these three cavities from top to bottom are respectively within 15-20nm, 40-45nm and 70-75nm. The proportions of the three cavities are 33%, 60% and 7% respectively. Through testing, the total specific surface area of ​​the alkylation catalyst G2 for ethylbenzene production is 822m 2 ·g -1 , with a total pore volume of 1.15 cm 3 ·g -1 , mechanical strength is 78N / cm, bulk density is 0.53g·cm -3 The SiO2 / Al2O3 molar ratio of the alkylation catalyst G2 to ethylbenzene was found to be 18.5 by ICP test.

[0074] [Example 3]

[0075] This embodiment is used to synthesize a molecular sieve catalyst for alkylation to produce ethylbenzene. The specific preparation process is as follows: 84.2 grams of tetraethylammonium hydroxide (aqueous solution with a concentration of 35wt%), 208.3 grams of tetraethyl silicate, 21.25 grams of sodium aluminate (with an Al2O3 mass content of 40%) and 180 grams of water are mixed evenly, and stirred at 130°C for 12 hours in a closed container to obtain a mixture A3. 120 grams of the mixture A3, 200 grams of silicon powder, 35.4 grams of sodium aluminate (with an Al2O3 mass content of 40%) and 20.2 grams of pseudo-boehmite (with an Al2O3 mass content of 70%) are contacted to obtain a mixture B3. B3 is extruded by adding an appropriate amount of deionized water to obtain a mixture C3 (C3 is cylindrical, with a diameter of 1.8mm and a length of 2-3mm). 1 g of ammonium fluoride, 150 g of tetraethylammonium hydroxide and 100 g of mixture C3 were treated at 130° C. for 72 hours in a closed space, then washed with deionized water until the pH value was 7.5, dried at 150° C. for 15 hours, and calcined at 550° C. for 6 hours in an air atmosphere to obtain mixture D3. 100 g of mixture D3 and 150 g of 0.2% sulfuric acid aqueous solution were treated at 50° C. for 1 hour in a closed space, then the acid solution was poured out, and 150 g of 15% ammonium chloride salt solution was added and treated at 50° C. for 1 hour in a closed space, then washed with deionized water until the pH value was 7.5, and dried at 150° C. for 15 hours to obtain mixture E3. 50 g of the mixture E3 and 75 g of an organic base solution with a mass concentration of 20% (the solution contains three organic bases, tetraethylammonium hydroxide, di-n-pentyldibenzhydrylammonium hydroxide and tri-n-hexylmonoethylammonium hydroxide, with the mass proportions of the three being 84%, 8% and 8% respectively) are mixed evenly to obtain a mixture F3. The mixture F3 is treated at 150° C. for 25 hours in a closed space, and then washed with deionized water until the pH value of the solution is 7, dried at 120° C. for 24 hours, and calcined at 550° C. for 5 hours to obtain a molecular sieve catalyst G3 for alkylation to ethylbenzene.

[0076] The XRD spectrum of the alkylation ethylbenzene catalyst G3 has a typical Beta molecular sieve diffraction peak. The molecular sieve crystal contains three kinds of nearly spherical cavities with different size distributions. The diameter distribution ranges of the circles corresponding to the vertical projections of these three cavities from top to bottom are respectively within 20-30nm, 40-45nm and 75-85nm. The proportions of the three cavities are 20%, 70% and 10% respectively. Through testing, the total specific surface area of ​​the alkylation ethylbenzene catalyst G3 is 780m 2 ·g -1 , with a total pore volume of 1.15 cm 3 ·g -1 , mechanical strength is 88N / cm, bulk density is 0.54g·cm -3The SiO2 / Al2O3 molar ratio of the alkylation catalyst G3 to ethylbenzene was found to be 13.4 by ICP test.

[0077] [Example 4]

[0078] This embodiment is used to synthesize a molecular sieve catalyst for alkylation to produce ethylbenzene. The specific preparation process is as follows: 84.2 grams of tetraethylammonium hydroxide (aqueous solution with a concentration of 35wt%), 208.3 grams of tetraethyl silicate, 21.25 grams of sodium aluminate (with an Al2O3 mass content of 40%) and 180 grams of water are mixed evenly, and stirred in a closed container at 130°C for 12 hours to obtain a mixture A4. 120 grams of the mixture A4, 200 grams of silicon powder, 35.4 grams of sodium aluminate (with an Al2O3 mass content of 40%) and 20.2 grams of pseudo-boehmite (with an Al2O3 mass content of 70%) are contacted to obtain a mixture B4. B4 is extruded by adding an appropriate amount of deionized water to obtain a mixture C4 (C4 is cylindrical, with a diameter of 1.8mm and a length of 2-3mm). 1 g of ammonium fluoride, 150 g of tetraethylammonium hydroxide and 100 g of mixture C4 were treated at 130° C. for 72 hours in a closed space, then washed with deionized water until the pH value was 7.5, dried at 150° C. for 15 hours, and calcined at 550° C. for 6 hours in an air atmosphere to obtain mixture D4. 100 g of mixture D4 and 150 g of 0.4% nitric acid aqueous solution were treated at 20° C. for 1 hour in a closed space, then the acid solution was poured out, and 150 g of 5% ammonium nitrate salt solution was added and treated at 20° C. for 1 hour in a closed space, then washed with deionized water until the pH value was 7.5, and dried at 150° C. for 15 hours to obtain mixture E4. 50 g of mixture E4 and 400 g of an organic base solution with a mass concentration of 20% (the solution contains three organic bases, tetraethylammonium hydroxide, di-n-pentyldibenzhydrylammonium hydroxide and tri-n-hexylmonoethylammonium hydroxide, with the mass proportions of the three being 84%, 8% and 8% respectively) are mixed evenly to obtain mixture F4. Mixture F4 is treated at 130° C. for 72 hours in a closed space, and then washed with deionized water until the pH value of the solution is 7, dried at 120° C. for 24 hours, and calcined at 550° C. for 5 hours to obtain a molecular sieve catalyst G4 for alkylation to ethylbenzene.

[0079] The XRD spectrum of the alkylation ethylbenzene catalyst G4 has a typical Beta molecular sieve diffraction peak. The molecular sieve crystal contains three kinds of nearly spherical cavities with different size distributions. The diameter distribution ranges of the circles corresponding to the vertical projections of these three cavities from top to bottom are respectively within 26-30nm, 45-50nm and 80-90nm. The proportions of the three cavities are 40%, 50% and 10% respectively. According to the test, the total specific surface area of ​​the alkylation ethylbenzene catalyst G4 is 850m 2 ·g -1, with a total pore volume of 1.2 cm 3 ·g -1 , mechanical strength is 80N / cm, bulk density is 0.52g·cm -3 The SiO2 / Al2O3 molar ratio of the alkylation catalyst G4 to ethylbenzene was found to be 14.1 by ICP test.

[0080] [Example 5]

[0081] This embodiment is used to synthesize a molecular sieve catalyst for alkylation to produce ethylbenzene. The specific preparation process is as follows: 84.2 grams of tetraethylammonium hydroxide (aqueous solution with a concentration of 35wt%), 208.3 grams of tetraethyl silicate, 21.25 grams of sodium aluminate (with an Al2O3 mass content of 40%) and 180 grams of water are mixed evenly, and stirred at 130°C for 12 hours in a closed container to obtain a mixture A5. 120 grams of the mixture A5, 200 grams of silicon powder, 35.4 grams of sodium aluminate (with an Al2O3 mass content of 40%) and 20.2 grams of pseudo-boehmite (with an Al2O3 mass content of 70%) are contacted to obtain a mixture B5. B5 is extruded by adding an appropriate amount of deionized water to obtain a mixture C5 (C5 is cylindrical with a diameter of 1.8mm and a length of 2-3mm). 1 g of ammonium fluoride, 150 g of tetraethylammonium hydroxide and 100 g of mixture C5 were treated at 130° C. for 72 hours in a closed space, then washed with deionized water until the pH value was 7.5, dried at 150° C. for 15 hours, and calcined at 550° C. for 6 hours in an air atmosphere to obtain mixture D5. 100 g of mixture D5 and 150 g of a 0.1% hydrochloric acid aqueous solution were treated at 20° C. for 1 hour in a closed space, then the acid solution was poured out, and 150 g of a 5% ammonium nitrate salt solution was added and treated at 20° C. for 1 hour in a closed space, then washed with deionized water until the pH value was 7.5, and dried at 150° C. for 15 hours to obtain mixture E5. 50 g of mixture E5 and 75 g of an organic base solution with a mass concentration of 20% (the solution contains three organic bases, tetraethylammonium hydroxide, di-n-pentyldibenzhydrylammonium hydroxide and tri-n-hexylmonoethylammonium hydroxide, with the mass proportions of the three being 88%, 7% and 5%, respectively) are mixed evenly to obtain mixture F5. Mixture F5 is treated at 130° C. for 72 hours in a closed space, and then washed with deionized water until the pH value of the solution is 7, dried at 120° C. for 24 hours, and calcined at 550° C. for 5 hours to obtain a molecular sieve catalyst G5 for alkylation to ethylbenzene.

[0082] The XRD spectrum of the alkylation ethylbenzene catalyst G5 has a typical Beta molecular sieve diffraction peak. The molecular sieve crystal contains three kinds of nearly spherical cavities with different size distributions. The diameter distribution range of the circles corresponding to the vertical projections of these three cavities from top to bottom is 15-25nm, 40-50nm and 80-90nm, respectively. The proportion of the number of these three cavities is 30%, 60% and 10%, respectively. Through testing, the total specific surface area of ​​the alkylation ethylbenzene catalyst G5 is 750m 2 ·g -1 , the total pore volume is 1.05cm 3 ·g -1 , mechanical strength is 83N / cm, bulk density is 0.53g·cm -3 The SiO2 / Al2O3 molar ratio of the alkylation catalyst G5 to ethylbenzene was found to be 13.5 by ICP test.

[0083] [Example 6]

[0084] This embodiment is used to synthesize a molecular sieve catalyst for alkylation to produce ethylbenzene. The specific preparation process is as follows: 84.2 grams of tetraethylammonium hydroxide (aqueous solution with a concentration of 35wt%), 208.3 grams of tetraethyl silicate, 21.25 grams of sodium aluminate (with an Al2O3 mass content of 40%) and 180 grams of water are mixed evenly, and stirred in a closed container at 130°C for 12 hours to obtain a mixture A6. 120 grams of the mixture A6, 200 grams of silicon powder, 35.4 grams of sodium aluminate (with an Al2O3 mass content of 40%) and 20.2 grams of pseudo-boehmite (with an Al2O3 mass content of 70%) are contacted to obtain a mixture B6. B6 is extruded by adding an appropriate amount of deionized water to obtain a mixture C6 (C6 is cylindrical with a diameter of 2.2mm and a length of 2-3mm). 1 g of ammonium fluoride, 150 g of tetraethylammonium hydroxide and 100 g of mixture C6 were treated at 130° C. for 48 hours in a closed space, then washed with deionized water until the pH value was 7.5, dried at 150° C. for 15 hours, and calcined at 550° C. for 6 hours in an air atmosphere to obtain mixture D6. 100 g of mixture D6 and 150 g of a 0.1% hydrochloric acid aqueous solution were treated at 20° C. for 1 hour in a closed space, then the acid solution was poured out, and 150 g of a 5% ammonium nitrate salt solution was added and treated at 20° C. for 1 hour in a closed space, then washed with deionized water until the pH value was 7.5, and dried at 150° C. for 15 hours to obtain mixture E6. 50g of mixture E6 and 75g of an organic base solution with a mass concentration of 10% (the solution contains three organic bases, tetraethylammonium hydroxide, di-n-pentyldibenzhydrylammonium hydroxide and tri-n-hexylmonoethylammonium hydroxide, with the mass proportions of the three being 84%, 8% and 8% respectively) are mixed evenly to obtain mixture F6. Mixture F6 is treated at 130°C in a closed space for 72 hours, then washed with deionized water until the pH value of the solution is 7, dried at 120°C for 24 hours and calcined at 550°C for 5 hours to obtain a molecular sieve catalyst G6 for alkylation to ethylbenzene.

[0085] The XRD spectrum of the alkylation ethylbenzene catalyst G6 has a typical Beta molecular sieve diffraction peak. The molecular sieve crystal contains three kinds of nearly spherical cavities with different size distributions. The diameter distribution ranges of the circles corresponding to the vertical projections of these three cavities from top to bottom are 15-22nm, 42-46nm and 60-65nm, respectively. The proportions of the three cavities are 35%, 60% and 5%, respectively. Through testing, the total specific surface area of ​​the alkylation ethylbenzene catalyst G6 is 710m 2 ·g -1 , with a total pore volume of 0.9 cm 3 ·g -1 , mechanical strength is 100N / cm, bulk density is 0.58g·cm -3The SiO2 / Al2O3 molar ratio of the alkylation catalyst G6 to ethylbenzene was found to be 13.2 by ICP test.

[0086] [Example 7]

[0087] This embodiment is used to synthesize a molecular sieve catalyst for alkylation to produce ethylbenzene. The specific preparation process is as follows: 84.2 grams of tetraethylammonium hydroxide (aqueous solution with a concentration of 35wt%), 208.3 grams of tetraethyl silicate, 6.3 grams of sodium aluminate (Al2O3 mass content of 40%) and 180 grams of water are mixed evenly, and stirred at 130°C for 12 hours in a closed container to obtain a mixture A7. 120 grams of the mixture A7, 200 grams of silicon powder, 12.5 grams of sodium aluminate (Al2O3 mass content of 40%) and 7.2 grams of pseudo-boehmite (Al2O3 mass content of 70%) are contacted to obtain a mixture B7. B7 is extruded and molded with an appropriate amount of deionized water to obtain a mixture C7 (C7 is cylindrical with a diameter of 1.8mm and a length of 2-3mm). 1 g of ammonium fluoride, 150 g of tetraethylammonium hydroxide and 100 g of mixture C7 were treated at 130° C. for 72 hours in a closed space, then washed with deionized water until the pH value was 7.5, dried at 150° C. for 15 hours, and calcined at 550° C. for 6 hours in an air atmosphere to obtain mixture D7. 100 g of mixture D7 and 150 g of a 0.1% hydrochloric acid aqueous solution were treated at 20° C. for 1 hour in a closed space, then the acid solution was poured out, and 150 g of a 5% ammonium nitrate salt solution was added and treated at 20° C. for 1 hour in a closed space, then washed with deionized water until the pH value was 7.5, and dried at 150° C. for 15 hours to obtain mixture E7. 50 g of the mixture E7 and 75 g of an organic base solution with a mass concentration of 20% (the solution contains three organic bases, tetraethylammonium hydroxide, di-n-pentyldibenzhydrylammonium hydroxide and tri-n-hexylmonoethylammonium hydroxide, with the mass proportions of the three being 84%, 8% and 8% respectively) are mixed uniformly to obtain a mixture F7. The mixture F7 is treated at 130° C. for 72 hours in a closed space, and then washed with deionized water until the pH value of the solution is 7, dried at 120° C. for 24 hours, and calcined at 550° C. for 5 hours to obtain a molecular sieve catalyst G7 for alkylation to ethylbenzene.

[0088] The XRD spectrum of the alkylation catalyst G7 for ethylbenzene has a typical Beta molecular sieve diffraction peak. The molecular sieve crystal contains three kinds of nearly spherical cavities with different size distributions. The diameter distribution ranges of the circles corresponding to the vertical projections of these three cavities from top to bottom are respectively within 22-30nm, 45-48nm and 84-88nm. The proportions of the three cavities are 20%, 75% and 5% respectively. Through testing, the total specific surface area of ​​the alkylation catalyst G7 for ethylbenzene is 800m 2 ·g -1, the total pore volume is 1.16cm 3 ·g -1 , mechanical strength is 88N / cm, bulk density is 0.54g·cm -3 The SiO2 / Al2O3 molar ratio of the alkylation catalyst G7 to ethylbenzene was found to be 39.8 by ICP test.

[0089] [Comparative Example 1]

[0090] Compared with Example 1, only mixture D was not treated with an acid solution, and the rest was the same. The specific preparation process of the catalyst is as follows: This example is used to synthesize a molecular sieve catalyst for alkylation to produce ethylbenzene, and the specific preparation process is as follows: 84.2 grams of tetraethylammonium hydroxide (aqueous solution with a concentration of 35wt%), 208.3 grams of tetraethyl silicate, 21.25 grams of sodium aluminate (Al2O3 mass content of 40%) and 180 grams of water are mixed evenly, and stirred in a closed container at 130°C for 12 hours to obtain a mixture A. 120 grams of mixture A, 200 grams of silicon powder, 35.4 grams of sodium aluminate (Al2O3 mass content of 40%) and 20.2 grams of pseudo-boehmite (Al2O3 mass content of 70%) are contacted to obtain a mixture B. B is extruded by adding an appropriate amount of deionized water to obtain a mixture C (C is cylindrical, with a diameter of 1.8mm and a length of 2-3mm). 1 gram of ammonium fluoride, 150 grams of tetraethylammonium hydroxide and 100 grams of mixture C were treated at 130°C in a closed space for 72 hours, then washed with deionized water until the pH value was 7.5, dried at 150°C for 15 hours, and roasted at 550°C in an air atmosphere for 6 hours to obtain mixture D. 100 grams of mixture D and 150 grams of ammonium nitrate salt solution with a mass concentration of 5% were treated at 20°C in a closed space for 1 hour, then washed with deionized water until the pH value was 7.5, and dried at 150°C for 15 hours to obtain mixture E. 50 grams of mixture E and 75 grams of organic base solution with a mass concentration of 20% (the solution contained three organic bases of tetraethylammonium hydroxide, di-n-pentyldibenzhydryl ammonium hydroxide and tri-n-hexyl-monoethyl ammonium hydroxide, and the mass proportions of the three were 84%, 8% and 8% respectively) were mixed uniformly to obtain mixture F. The mixture F was treated at 130° C. for 72 hours in a closed space, then washed with deionized water until the pH value of the solution was 7, dried at 120° C. for 24 hours, and calcined at 550° C. for 5 hours to obtain a molecular sieve catalyst H1.

[0091] TEM image of catalyst H1 Figure 4 As shown in the figure, there is no obvious cavity inside the molecular sieve crystal. The total specific surface area of ​​the alkylation catalyst H1 for ethylbenzene is 580m 2 ·g -1 , with a total pore volume of 0.3 cm 3 ·g -1, mechanical strength is 125N / cm, bulk density is 0.60cm 3 ·g -1 The SiO2 / Al2O3 molar ratio of the alkylation catalyst H1 to ethylbenzene was found to be 14.2 by ICP test.

[0092] [Comparative Example 2]

[0093] Compared with Example 1, the only difference is that the organic base used is tetraethylammonium hydroxide, and the rest is the same. The specific preparation process is as follows: 84.2 grams of tetraethylammonium hydroxide (aqueous solution with a concentration of 35wt%), 208.3 grams of tetraethyl silicate, 21.25 grams of sodium aluminate (with an Al2O3 mass content of 40%) and 180 grams of water are mixed evenly, and stirred at 130°C for 12 hours in a closed container to obtain a mixture A. 120 grams of the mixture A, 200 grams of silicon powder, 35.4 grams of sodium aluminate (with an Al2O3 mass content of 40%) and 20.2 grams of pseudo-boehmite (with an Al2O3 mass content of 70%) are contacted to obtain a mixture B. B is extruded by adding an appropriate amount of deionized water to obtain a mixture C (C is cylindrical, with a diameter of 1.8mm and a length of 2-3mm). 1 gram of ammonium fluoride, 150 grams of tetraethylammonium hydroxide and 100 grams of mixture C were treated at 130°C for 72 hours in a closed space, then washed with deionized water until the pH value was 7.5, dried at 150°C for 15 hours, and roasted at 550°C in an air atmosphere for 6 hours to obtain mixture D. 100 grams of mixture D and 150 grams of 0.1% hydrochloric acid aqueous solution were treated at 20°C for 1 hour in a closed space, then the acid solution was poured out, and 150 grams of 5% ammonium nitrate salt solution was added and treated at 20°C for 1 hour in a closed space, then washed with deionized water until the pH value was 7.5, and dried at 150°C for 15 hours to obtain mixture E. 50 grams of mixture E and 75 grams of 20% tetraethylammonium hydroxide solution were mixed uniformly to obtain mixture F. The mixture F was treated at 130° C. for 72 hours in a closed space, then washed with deionized water until the pH value of the solution was 7, dried at 120° C. for 24 hours, and calcined at 550° C. for 5 hours to obtain a molecular sieve catalyst H2.

[0094] TEM image of catalyst H2 Figure 5 As shown in the figure, the cavity inside the molecular sieve crystal is irregular in shape, and the maximum cavity diameter is more than 150nm. Through testing, the total specific surface area of ​​the alkylation catalyst H2 is 680m 2 ·g -1 , with a total pore volume of 1.3 cm 3 ·g -1 , mechanical strength is 55N / cm, bulk density is 0.50cm 3 ·g -1The SiO2 / Al2O3 molar ratio of catalyst H2 was 11.6 as determined by ICP testing.

[0095] [Example 8]

[0096] The alkylation catalysts G1-G2 and H1-H2 prepared in Examples 1-2 and Comparative Examples 1-2 were respectively applied to the alkylation reaction of benzene and ethylene to produce ethylbenzene. The reaction temperature was 180°C, the pressure was 3.5 MPa, and the mass space velocity of ethylene was 0.6 h -1 , under the condition that the molar ratio of benzene to ethylene was 1.5, the ethylene conversion rate, ethyl selectivity and diethylbenzene content in the alkylation product were tested. The test results are shown in Table 1 below.

[0097] Table 1 Alkylation of benzene and ethylene to produce ethylbenzene

[0098]

[0099] [Example 9]

[0100] The alkylation catalysts G1-G2 and H1-H2 prepared in Examples 1-2 and Comparative Examples 1-2 were tested for their one-way life in the alkylation of benzene and ethylene to produce ethylbenzene under ultra-high ethylene mass space velocity reaction conditions. The specific test conditions are as follows: reaction temperature 220°C, pressure 3.5MPa, ethylene mass space velocity 5h -1 , the molar ratio of benzene to ethylene is 1.5, and the one-way life refers to the time from the start of the reaction to the time when the ethylene conversion rate drops to 60% of the initial conversion rate. The test results are shown in Table 2 below. Under ultra-high ethylene space velocity reaction conditions, the one-way life of G1-G2 is significantly longer than that of H1-H2.

[0101] Table 2 Single-pass life test results of catalysts under ultra-high space velocity reaction conditions

[0102] Catalyst No. One-way life, h G1 480 G2 495 H1 240 H2 326

[0103] The above describes the specific implementation of the present invention in detail, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the various technical features being combined in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A molecular sieve catalyst for benzene alkylation, characterized in that: The molecular sieve crystals in the catalyst contain nearly spherical cavities with three size distributions, the diameter distribution ranges of the circles corresponding to the vertical projections of the three cavities from top to bottom are respectively within 10-30 nm, 40-50 nm and 60-90 nm, and the proportions of the three cavities are respectively 20%-40%, 50%-75% and 5%-10%; the catalyst is a binder-free molecular sieve catalyst; wherein the molecular sieve is a silicon-aluminum molecular sieve with a twelve-membered ring pore structure.

2. The molecular sieve catalyst according to claim 1, characterized in that The molecular sieve is Beta molecular sieve.

3. The molecular sieve catalyst according to claim 1, characterized in that The total specific surface area of ​​the catalyst is 700-850 m 2 ·g -1 , with a total pore volume of 0.9-1.2 cm 3 ·g -1 .

4. The molecular sieve catalyst according to claim 1, characterized in that: The mechanical strength of the catalyst is 60-120 N / cm.

5. The molecular sieve catalyst according to claim 1, characterized in that: The mechanical strength of the catalyst is 70-100 N / cm.

6. The molecular sieve catalyst according to claim 1, characterized in that: The bulk density of the catalyst is 0.52-0.58 g·cm -3 .

7. The method for preparing the molecular sieve catalyst according to any one of claims 1 to 6, characterized in that: The steps include: (a) treating the molecular sieve with an acid and an ammonium salt solution to obtain a mixture E; (b) The mixture E is contacted with a mixed organic base to obtain a mixture F, and the mixture F is treated at 130-150°C for 24-72 hours, and then washed, dried and calcined to obtain a molecular sieve catalyst for benzene alkylation.

8. The preparation method according to claim 7, characterized in that: The acid used for the acid treatment in step (a) is one or more of hydrochloric acid, sulfuric acid and nitric acid.

9. The preparation method according to claim 8, characterized in that: The acid used in the acid treatment in step (a) is an aqueous solution of the acid with a mass concentration of 0.1%-0.5%.

10. The preparation method according to claim 7, characterized in that: In step (a), the ammonium salt is one or more of ammonium chloride, ammonium nitrate and ammonium sulfate.

11. The preparation method according to claim 10, characterized in that: The ammonium salt solution in step (a) is an aqueous solution with a mass concentration of 5%-20%.

12. The preparation method according to claim 7, characterized in that: The acid treatment condition in step (a) is 20-50° C. for 1-2 hours.

13. The preparation method according to claim 12, characterized in that: In step (a), the acid treatment is carried out in a closed space.

14. The preparation method according to claim 7, characterized in that: The ammonium salt solution treatment condition in step (a) is 20-50° C. for 1-2 hours.

15. The preparation method according to claim 14, characterized in that: In step (a), the ammonium salt solution treatment is carried out in a closed space.

16. The preparation method according to claim 7, characterized in that: In step (a), the weight ratio of the acid solution used in the acid treatment to the molecular sieve is (1.5-10):1; the weight ratio of the ammonium salt solution used in the ammonium salt solution treatment to the molecular sieve is (1.5-10):

1.

17. The preparation method according to claim 7, characterized in that: The mixed organic base in step (b) is a mixed organic base aqueous solution with a mass concentration of 10%-20%.

18. The preparation method according to claim 17, characterized in that: In step (b), the mass ratio of the mixed organic base aqueous solution to the mixture E is (1.5-10):

1.

19. The preparation method according to claim 7, characterized in that: The mixed organic base in step (b) is a mixed alkali aqueous solution of tetraethylammonium hydroxide and at least two other different quaternary ammonium bases, the other quaternary ammonium bases having the structural formula , wherein R1, R2, R3 and R4 are each independently selected from n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, benzyl or phenethyl.

20. The preparation method according to claim 19, characterized in that: The mass ratio of tetraethylammonium hydroxide to the total amount of other quaternary ammonium bases in step (b) is (5-8):

1.

21. The preparation method according to claim 20, characterized in that: In step (b), the mass proportion of each quaternary ammonium base in other quaternary ammonium bases is 20%-60%.

22. The preparation method according to claim 7, characterized in that: The molecular sieve is a binder-free molecular sieve, and the preparation process of the binder-free molecular sieve comprises the following steps: (1) contacting a first template, a silicon source, a first aluminum source, and water to obtain a mixture A; The molar ratios of the first template, silicon source, first aluminum source and water are respectively: first template: silicon source = (0.2-0.6): 1; silicon source: first aluminum source = (12-40): 1, water: silicon source = (10-15): 1, wherein the silicon source is calculated as SiO2, and the first aluminum source is calculated as Al2O3; (2) contacting mixture A, silicon powder and a second aluminum source to obtain mixture B; The ratios of the mixture A, silicon powder and the second aluminum source are as follows: the weight ratio of the mixture A to the silicon powder is (0.6-1.0):1; the molar ratio of the silicon powder to the second aluminum source is (12-40):1; the silicon powder is calculated as SiO2, and the second aluminum source is calculated as Al2O3; (3) forming mixture B to obtain mixture C; (4) contacting the mixture C, the fluoride and the second template to obtain a mixture D, and washing, drying and calcining the mixture D to obtain a binder-free molecular sieve; The weight ratio of the fluoride to the mixture C is (0.01-0.03):1, and the weight ratio of the second template to the mixture C is (1.5-3):

1.

23. Use of the molecular sieve catalyst according to any one of claims 1 to 6 or the molecular sieve catalyst prepared by the preparation method according to any one of claims 7 to 22 in the alkylation reaction of benzene and olefins.

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