Binder-free ZSM-5 molecular sieve catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of molecular sieves, and discloses a binder-free ZSM-5 molecular sieve catalyst as well as a preparation method and application thereof. The binderless ZSM-5 molecular sieve catalyst comprises the following components in percentage by weight: a) 94.5-99.5% of a binderless ZSM-5 molecular sieve, wherein the molar ratio of silicon to aluminum (SiO2 / Al2O3) is 50-400, and the longest distance between any two points on a crystal grain is 500-1000 nm; b) 0.1-5% of a rare earth metal oxide; c) 0.1% to 1% of phosphorus pentoxide; wherein the molar ratio of the phosphorus element to the silicon element on the surface of the catalyst is 1: (10-100) through an XPS test. According to the present invention, the rare earth metal is directly introduced into the binder-free ZSM-5 molecular sieve, such that the rare earth metal is prevented from blocking the pore channel of the molecular sieve, and the prepared catalyst has characteristics of high ethanol conversion rate, high ethyl selectivity, and good activity stability.

Description

Technical Field

[0001] The invention relates to the technical field of molecular sieves, and in particular to a binder-free ZSM-5 molecular sieve catalyst and a preparation method and application thereof. Background Art

[0002] Ethylbenzene is an important petrochemical raw material, mainly used to produce styrene, which is the main raw material for producing polystyrene and other copolymer resins. Ethylbenzene is mainly produced by alkylation of benzene and ethylene, which is divided into AlCl3 method and molecular sieve method, among which AlCl3 method is a technology that is about to be eliminated. In the 1980s, Mobile and Badger successfully launched the process of producing ethylbenzene by molecular sieve gas phase alkylation. The process uses ZSM-5 molecular sieve as a catalyst and has the advantages of no corrosion, no pollution, simple process and high heat recovery rate. US3751504, US3751506, US4016218 and US4547605 all have detailed descriptions of this. In the early 1990s, Lummus and UOP introduced a molecular sieve liquid phase alkylation process for producing ethylbenzene. This process uses β and Y zeolite molecular sieves as catalysts and has the advantages of low reaction temperature, easy operation and few by-products. US4891458, US5227558 and ZL02151177.2 all have detailed descriptions of this process. In the mid-1990s, a liquid phase alkylation and gas phase alkylation process for producing ethylbenzene was introduced. This process uses MCM-22 as a molecular sieve liquid phase alkylation catalyst and has the advantages of low benzene-olefin ratio and few by-products. ZL95197033.X has a detailed description of this process.

[0003] The above-mentioned ethylbenzene production technologies all require the use of ethylene as a raw material, and ethylene is originally produced from petroleum and shale gas as basic raw materials. As petroleum resources become increasingly scarce, people actively seek and explore the use of renewable resources. Biomass ethanol is a green renewable resource, so the process route of alkylating benzene and ethanol to produce ethylbenzene has attracted widespread attention. The key technology of this process route is the catalyst, and the prepared catalyst meets the needs of long-term periodic operation of industrial production; at the same time, on the basis of ensuring that ethanol is basically fully converted, the catalyst must have good selectivity and minimize the generation of impurities such as xylene. CN101450888A discloses a method for preparing a catalyst for synthesizing ethylbenzene through catalytic dehydration reaction, wherein the catalyst contains a ZSM-5 molecular sieve with a high silicon-aluminum ratio, a binder and a modifying component, and the modifying component is selected from at least one of IIA, IIIA, VA and rare earth metal oxides in the periodic table, but the catalyst conversion rate does not exceed 17%, and the ethylbenzene selectivity does not exceed 97%, and there is still room for greater performance improvement. In order to improve the selectivity of ethylbenzene, CN103121909A discloses a method for producing ethylbenzene by gas-phase alkylation of ethanol and benzene. The catalyst uses a binder-free ZSM-5 molecular sieve modified by rare earth metals and phosphoric acid. However, the rare earth elements and phosphorus are loaded on the molecular sieve by physical mixing or impregnation, which easily clogs the pores of the molecular sieve and affects its catalytic activity and stability. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of poor ethylbenzene selectivity, poor catalyst stability and low catalytic activity in the prior art, and to provide a binder-free ZSM-5 molecular sieve catalyst and a preparation method and application thereof. The catalyst has high ethanol conversion rate and ethyl selectivity, low xylene impurity content in ethylbenzene, good catalyst stability and high catalytic activity.

[0005] In order to achieve the above object, the first aspect of the present invention provides a binder-free ZSM-5 molecular sieve catalyst, wherein the catalyst comprises the following components by weight percentage:

[0006] a) 94.5-99.5% of a binderless ZSM-5 molecular sieve having a silicon-aluminum molar ratio SiO2 / Al2O3 of 50-400 and a maximum distance between any two points on a grain of 500-1000 nm;

[0007] b) 0.1-5% rare earth metal oxides;

[0008] c) 0.1-1% of phosphorus pentoxide;

[0009] Among them, according to XPS testing, the molar ratio of phosphorus element to silicon element on the catalyst surface is 1:10-100.

[0010] A second aspect of the present invention provides a method for preparing a binder-free ZSM-5 molecular sieve catalyst, wherein the method comprises the following steps:

[0011] (1) kneading ZSM-5 seed crystals, an aluminum source, a binder, a rare earth metal salt and optional additives, forming the mixture, and drying the mixture to obtain a ZSM-5 molecular sieve precursor;

[0012] (2) crystallizing the ZSM-5 molecular sieve precursor and performing solid-liquid separation to obtain a binder-free ZSM-5 molecular sieve containing rare earth elements;

[0013] (3) treating the binder-free ZSM-5 molecular sieve containing rare earth elements with steam, phosphoric acid and water, and drying to obtain a binder-free ZSM-5 molecular sieve catalyst;

[0014] Calculated by weight percentage of the catalyst, the content of the binder-free ZSM-5 molecular sieve in the catalyst is 94.5-99.5%; the content of the rare earth metal oxide is 0.1-5%; and the content of the phosphorus element is 0.1-1%.

[0015] The third aspect of the present invention provides a use of the binderless ZSM-5 molecular sieve catalyst described in the first aspect or the binderless ZSM-5 molecular sieve catalyst prepared by the method described in the second aspect in the alkylation reaction of benzene and ethanol to produce ethylbenzene.

[0016] Through the above technical solution, the present invention can achieve the following technical effects:

[0017] (1) The binderless ZSM-5 molecular sieve catalyst provided by the present invention does not contain an inert binder, has a high molecular sieve content, and has a large available effective surface area. The obtained binderless ZSM-5 molecular sieve catalyst has a large pore volume and better catalytic performance;

[0018] (2) The binderless ZSM-5 molecular sieve catalyst provided by the present invention directly introduces rare earth metals into the binderless ZSM-5 molecular sieve, which avoids clogging the molecular sieve pores and improves the catalytic activity, selectivity and stability of the catalyst compared with the traditional method of loading rare earth metal elements on the molecular sieve by impregnation;

[0019] (3) The binder-free ZSM-5 molecular sieve catalyst provided by the present invention contains a certain amount of phosphorus on its surface according to XPS testing, and has good dispersibility, thus preventing a large amount of phosphorus from accumulating in the molecular sieve pores and blocking the pores;

[0020] (4) The binderless ZSM-5 molecular sieve catalyst provided by the present invention is used in the gas phase alkylation reaction of benzene and ethanol, and has high catalytic activity, selectivity and stability, with an ethanol conversion rate of ≥99.5%, an ethyl selectivity of greater than 99.2%, and a low xylene content in the obtained ethylbenzene product, which can reach less than 650 ppm;

[0021] (5) The method for preparing the binder-free ZSM-5 molecular sieve catalyst provided by the present invention comprises treating the catalyst with a phosphoric acid solution to reduce the strength of the molecular sieve catalyst acid and remove amorphous substances in the molecular sieve pores or non-framework aluminum and other substances removed from the molecular sieve framework; washing the catalyst after being treated with the phosphoric acid solution with water to solve the problem of a large amount of phosphorus blocking the molecular sieve pores, improve the activity stability of the catalyst, and extend the catalyst regeneration cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation of the present invention.

[0023] Figure 1 NH3-TPD diagram of the binderless ZSM-5 molecular sieve catalyst prepared according to Example 1 of the present invention;

[0024] Figure 2 This is a scanning electron microscope image of the binderless ZSM-5 molecular sieve catalyst prepared according to Example 1 of the present invention. DETAILED DESCRIPTION

[0025] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0026] The first aspect of the present invention provides a binder-free ZSM-5 molecular sieve catalyst, wherein the catalyst comprises the following components by weight percentage:

[0027] a) 94.5-99.5% of a binderless ZSM-5 molecular sieve having a silicon-aluminum molar ratio SiO2 / Al2O3 of 50-400 and a maximum distance between any two points on a grain of 500-1000 nm;

[0028] b) 0.1-5% rare earth metal oxides;

[0029] c) 0.1-1% of phosphorus pentoxide;

[0030] Among them, according to XPS testing, the molar ratio of phosphorus element to silicon element on the catalyst surface is 1:10-100.

[0031] The inventors of the present invention have discovered that by directly introducing rare earth metals into a binderless ZSM-5 molecular sieve, the resulting binderless ZSM-5 molecular sieve catalyst avoids clogging of the molecular sieve pores by rare earth metals, thereby improving the catalytic activity stability and selectivity of the catalyst. In addition, the rare earth elements have a stabilizing effect on the aluminum of the molecular sieve framework, inhibiting the aluminum atoms from falling off the framework under high-temperature water vapor reaction conditions, thereby improving the hydrothermal stability of the catalyst and extending the catalyst regeneration cycle.

[0032] In some embodiments of the present invention, preferably, the micropore volume of the catalyst is 0.13-0.18 cm 3 / g is preferably 0.14-0.17cm 3 / g.

[0033] In the present invention, the binderless ZSM-5 molecular sieve has a high molecular sieve content, a large available effective surface area, and a large pore volume of the obtained binderless ZSM-5 molecular sieve catalyst, which avoids a large amount of rare earth metal elements and phosphorus blocking the molecular sieve pores, and is conducive to making the catalyst have higher catalytic performance. The micropore volume of the catalyst is tested by N2 physical adsorption and calculated by t-plot curve.

[0034] In some embodiments of the present invention, preferably, after NH3-TPD testing, the catalyst has two peaks, wherein the highest position of the first peak is at 170-210°C, preferably 180-200°C, and the highest position of the second peak is at 340-380°C, preferably 350-370°C, and the ratio of the peak heights of the first peak to the second peak is 1:0.9-1.1.

[0035] In the present invention, the binderless ZSM-5 molecular sieve catalyst has two peaks in the NH3-TPD spectrum, the first peak is a weak acid peak, the second peak is a medium-strong acid peak, and the two peaks have a specific height ratio, which is suitable for the alkylation reaction of benzene and ethanol. The NH3-TPD is tested using a chromatographic thermal conductivity detector, and the test conditions are that after ammonia is adsorbed on the catalyst surface, it is desorbed in a He atmosphere, and the heating rate is 10°C / min.

[0036] In some embodiments of the present invention, preferably, the binderless ZSM-5 molecular sieve has a silicon-aluminum molar ratio SiO2 / Al2O3 of 200-350.

[0037] In the present invention, the lower the silicon-aluminum molar ratio of the binderless ZSM-5 molecular sieve is, the more active centers there are, but the molecular sieve with too low silicon-aluminum ratio will greatly reduce the selectivity of the reaction. The silicon-aluminum molar ratio SiO2 / Al2O3 of the binderless ZSM-5 molecular sieve provided by the present invention is 50-400, and the obtained binderless ZSM-5 molecular sieve catalyst has excellent catalytic performance. The catalyst obtained within the preferred silicon-aluminum molar ratio range of the binderless ZSM-5 molecular sieve has more excellent catalytic performance.

[0038] In some embodiments of the present invention, preferably, the binder-free ZSM-5 molecular sieve is an elongated grain, and the longest distance between any two points on the grain is 550-900 nm. In the present invention, the grain morphology is tested using a scanning electron microscope (SEM).

[0039] In some embodiments of the present invention, preferably, based on the weight percentage of the catalyst, the content of binder-free ZSM-5 molecular sieve in the catalyst is 97-98.5%; the content of rare earth metal oxide is 0.3-2.5%; and the content of phosphorus pentoxide is 0.2-0.5%.

[0040] In the present invention, the contents of the binderless ZSM-5 molecular sieve, the rare earth metal oxide and the phosphorus element in the binderless ZSM-5 molecular sieve catalyst are controlled within the above preferred ranges, which is conducive to making the catalyst have better catalytic performance. The elemental composition of the catalyst is measured by an X-ray fluorescence spectrometer (XRF).

[0041] In the present invention, if the content of the rare earth metal oxide is higher than 5% by weight of the catalyst, the catalytic activity of the catalyst will be reduced and the acidity will be suppressed; if the content of the rare earth metal oxide is lower than 0.1% and the amount is too small, it will not effectively act as an auxiliary agent.

[0042] In some embodiments of the present invention, preferably, after XPS testing, the molar ratio of phosphorus to silicon on the catalyst surface is 1:40-80. The catalyst surface elements are measured using a light ray photoelectron spectrometer (XPS).

[0043] In some embodiments of the present invention, preferably, the rare earth metal oxide is selected from lanthanide metal oxides, preferably at least one selected from lanthanum oxide, cerium oxide and praseodymium oxide, more preferably lanthanum oxide.

[0044] In the present invention, rare earth metal elements are used for modification, and the rare earth metal elements have a stabilizing effect on the aluminum of the molecular sieve framework, inhibit the occurrence of dealumination of the molecular sieve framework, improve the activity stability and selectivity of the catalyst, and extend the regeneration period of the catalyst.

[0045] A second aspect of the present invention provides a method for preparing a binder-free ZSM-5 molecular sieve catalyst, wherein the method comprises the following steps:

[0046] (1) kneading ZSM-5 seed crystals, an aluminum source, a binder, a rare earth metal salt and optional additives, forming the mixture, and drying the mixture to obtain a ZSM-5 molecular sieve precursor;

[0047] (2) crystallizing the ZSM-5 molecular sieve precursor and performing solid-liquid separation to obtain a binder-free ZSM-5 molecular sieve containing rare earth elements;

[0048] (3) treating the binder-free ZSM-5 molecular sieve containing rare earth elements with steam, phosphoric acid and water, and drying to obtain a binder-free ZSM-5 molecular sieve catalyst;

[0049] Calculated by weight percentage of the catalyst, the content of the binder-free ZSM-5 molecular sieve in the catalyst is 94.5-99.5%; the content of the rare earth metal oxide is 0.1-5%; and the content of phosphorus pentoxide is 0.1-1%.

[0050] In some embodiments of the present invention, preferably, the content of the binderless ZSM-5 molecular sieve in the catalyst is 97-98.5% by weight; the content of the rare earth metal oxide is 0.3-2.5%; and the content of phosphorus pentoxide is 0.2-0.5%. In the present invention, the description of the composition of the binderless ZSM-5 molecular sieve catalyst obtained by the preparation method of the binderless ZSM-5 molecular sieve catalyst is as described above and will not be repeated here.

[0051] In some embodiments of the present invention, preferably, in step (1), the ZSM-5 seed crystal is ZSM-5 molecular sieve raw powder.

[0052] In the present invention, the ZSM-5 seed crystal is a conventional seed crystal known in the art, and its preparation method is well known in the art. It can be synthesized by the following hydrothermal crystallization method: a silicon compound, an aluminum compound, a base and a template are mixed, and hydrothermal crystallization is performed at 100-170° C. for 10-96 hours to obtain the ZSM-5 seed crystal of the present invention.

[0053] In the present invention, the silicon compound is selected from at least one of silica sol, water glass, silicon powder, and white carbon black; the aluminum compound is selected from at least one of 18-hydrate and aluminum sulfate, aluminum trichloride, and aluminum alcohol; the base is selected from an alkali metal or alkaline earth metal cation base or a template with a strong alkalinity such as tetrapropylammonium hydroxide and tetraethylammonium hydroxide; the template agent is selected from at least one of tetrapropylammonium hydroxide, tetrapropylammonium bromide, ethylamine, n-propylamine, and n-butylamine.

[0054] In the present invention, the molar ratio of the silicon compound, the aluminum compound, the base and the template agent is 1: (0.001-0.02): (0.1-0.5): (0.1-1.0): (6-20). Controlling the amount of the silicon compound, the aluminum compound, the base and the template agent within the above range is conducive to making the material easier to hydrothermally crystallize and obtain the ZSM-5 seed crystal.

[0055] In the present invention, the ZSM-5 seed crystals may be a slurry material or a powder material after solid separation, washing and drying, preferably ZSM-5 molecular sieve raw powder.

[0056] In some embodiments of the present invention, preferably, based on the weight of total SiO2 in the ZSM-5 molecular sieve precursor, the content of the ZSM-5 seed crystals in terms of SiO2 is 0-15% and is not 0, preferably 0.5-5%.

[0057] In some embodiments of the present invention, preferably, the aluminum source is an aluminum salt, preferably at least one selected from aluminum sulfate, aluminum nitrate, aluminum acetate, aluminum chloride and hydrates thereof, preferably aluminum sulfate.

[0058] In some embodiments of the present invention, preferably, the binder is selected from at least one of silicon powder, white carbon black and silica sol, preferably selected from at least two of silicon powder, white carbon black and silica sol, more preferably silicon powder and silica sol. In the present invention, in step (1), the binder can act as a molding aid, and in step (2), the binder also acts as a silicon source.

[0059] In some embodiments of the present invention, preferably, the binder is calculated as SiO2, the aluminum source is calculated as Al2O3, and the SiO2 / Al2O3 molar ratio is 50-400, preferably 200-350.

[0060] In some embodiments of the present invention, preferably, based on the total weight of the SiO2 and Al2O3, the content of the rare earth metal salt in terms of oxide is 0.1-5%, preferably 0.2-3.5%.

[0061] In some embodiments of the present invention, preferably, in step (1), the additive is selected from a pore-forming agent and / or an aqueous solution of an acid. In the present invention, the role of the additive is to increase viscosity to facilitate molding and to generate partial pores during the molding process.

[0062] In some embodiments of the present invention, preferably, the pore former is selected from methyl cellulose and / or sesbania powder.

[0063] In some embodiments of the present invention, preferably, the amount of the pore former is 0.2-1% of the total weight of the raw materials added in step (1). In the present invention, the total weight of the raw materials added in step (1) refers to the total weight of the ZSM-5 seed crystals, aluminum source, binder, rare earth metal salt and optional additives.

[0064] In some embodiments of the present invention, preferably, the acid is selected from any one of nitric acid, hydrochloric acid, sulfuric acid and oxalic acid, preferably nitric acid.

[0065] In some embodiments of the present invention, preferably, the concentration of the aqueous acid solution is 1-10 wt %, preferably 5-8 wt %.

[0066] In some embodiments of the present invention, preferably, the amount of the acid aqueous solution is 10-40% of the total weight of the raw materials added in step (1). In the present invention, the total weight of the raw materials added in step (1) refers to the total weight of ZSM-5 seed crystals, aluminum source, binder, rare earth metal salt and optional additives.

[0067] In the present invention, in step (1), ZSM-5 seed crystals, aluminum source, binder, rare earth metal salt and optional additives are mixed and kneaded into a plastic body. The present invention directly introduces rare earth metals into a binder-free ZSM-5 molecular sieve, and compared with the traditional method of loading rare earth metal elements on a molecular sieve by impregnation, it avoids blocking the molecular sieve pores and improves the catalytic activity stability and selectivity of the catalyst; the plastic body obtained by controlling the amount of each raw material within the above range is more conducive to extrusion into strips, which is conducive to making the extruded cylindrical strip plastic body more suitable for drying treatment, and is more conducive to forming a binder-free ZSM-5 molecular sieve catalyst with a good micropore volume. Preferably, the mixing is carried out under stirring, wherein the stirring conditions are not specifically limited, for example, it can be carried out under stirring conditions of 20-50r / min.

[0068] In the present invention, the extrusion into strips is carried out in an extruder, for example, the plastomer can be extruded into strips using a stainless steel kneading extruder, wherein the model produced by Zibo Yuecheng Machinery Co., Ltd. is a ZYDJ single screw extruder. In addition, according to the difference in the extrusion orifice plate in the extruder, a cylindrical strip ZSM-5 molecular sieve precursor with a diameter of 0.5-4 mm can be prepared, and the diameter is preferably 1-3 nm.

[0069] In the present invention, the drying is to dry the cylindrical strip plastic body after forming in a drying oven. There is no special requirement for the drying conditions. For example, it can be dried at a temperature of 130-150°C for 4-15h. In the present invention, the binder described in step (1) is used as a molding raw material, and a ZSM-5 molecular sieve precursor is obtained after extrusion molding and drying. In step (2), the precursor is subjected to liquid phase crystallization under microwave conditions, and the binder is used as a silicon source in the obtained binder-free ZSM-5 molecular sieve containing rare earth elements.

[0070] In some embodiments of the present invention, preferably, in step (2), the specific step of crystallization includes: mixing the ZSM-5 molecular sieve precursor and the organic amine solution, and then crystallizing under microwave conditions.

[0071] In some embodiments of the present invention, preferably, the organic amine is selected from at least one of ethylamine, n-propylamine and n-butylamine.

[0072] In some embodiments of the present invention, preferably, the organic amine solution is an aqueous solution of organic amine.

[0073] In some embodiments of the present invention, preferably, the concentration of the organic amine solution is 40-70 wt %.

[0074] In some embodiments of the present invention, preferably, the mass ratio of the ZSM-5 molecular sieve precursor to the organic amine solution is 1:1.2-2.

[0075] In some embodiments of the present invention, preferably, the crystallization conditions include: a crystallization temperature of 80-110° C., a crystallization time of 2-12 h, and a microwave power of 200-1000 W.

[0076] In the present invention, in step (2), the ZSM-5 molecular sieve precursor is subjected to liquid phase crystallization under microwave conditions to obtain a crystallized solid product, and then the crystallized solid product is subjected to solid-liquid separation, washing and drying in sequence to obtain a binder-free ZSM-5 molecular sieve containing rare earth elements.

[0077] In the present invention, there is no limitation on the method of solid-liquid separation, as long as solid-liquid separation can be achieved, such as solid-liquid separation can be achieved by filtration separation. Filtration separation is a method of separating liquid and solid particles well known to those skilled in the art, which uses air pressure to separate liquid and solid particles or a mixture of liquid and liquid.

[0078] In the present invention, the method for preparing the binder-free ZSM-5 molecular sieve catalyst may further include the steps of washing, drying and calcining the solid after solid-liquid separation. There are no special requirements for the washing method. For example, the solid can be mixed with deionized water, stirred for 2-4 hours, separated after standing for 2-3 hours, and the above washing process is repeated 6-10 times. There are no special requirements for the drying method. For example, it can be carried out in a drying oven and dried at 130-150°C for 4-15 hours. There are no special requirements for the calcination conditions. For example, it can be calcined at 450-600°C for 4-15 hours.

[0079] In some embodiments of the present invention, preferably, in step (3), the conditions for the water vapor treatment include: the pressure of the water vapor treatment is normal pressure, the temperature is 400-650° C., and the time is 4-10 h.

[0080] In the present invention, the binder-free ZSM-5 molecular sieve containing rare earth elements is subjected to steam treatment under high temperature conditions. The high temperature steam treatment is beneficial to improving the hydrothermal stability of the catalyst and improving the water resistance of the catalyst under reaction conditions.

[0081] In some embodiments of the present invention, preferably, the molecular sieve treated with water vapor is treated with phosphoric acid solution, and the conditions of the phosphoric acid treatment include: the concentration of the phosphoric acid solution is 0.05-2 mol / L, preferably 0.1-0.5 mol / L; the phosphoric acid treatment temperature is 20-90°C, preferably 40-70°C; the phosphoric acid treatment time is 2-15h, preferably 4-8h; the weight ratio of the phosphoric acid solution to the molecular sieve is 2-10, preferably 3-8.

[0082] In the present invention, the specific operation of the phosphoric acid solution treatment includes: subjecting the catalyst treated with water vapor to phosphoric acid treatment, using a phosphoric acid solution with a concentration of 0.05-2 mol / L at a temperature of 20-90° C. for 2-15 hours, and the weight ratio of the phosphoric acid solution to the molecular sieve is 2-10.

[0083] In the present invention, the preparation method used makes the phosphoric acid loading amount higher than the conventional method, which is more conducive to removing amorphous substances in the molecular sieve pores or non-framework aluminum and other substances removed from the molecular sieve framework, and has a modifying effect on the molecular sieve pores; and is conducive to further increasing the binding force of aluminum oxygen bonds in the molecular sieve, inhibiting the molecular sieve framework from dealumination, improving the activity stability of the catalyst, and extending the catalyst regeneration cycle. The conditions for the phosphoric acid solution treatment are within the preferred range, and the obtained catalyst has more excellent comprehensive performance.

[0084] In some embodiments of the present invention, preferably, the phosphoric acid solution is selected from an aqueous solution of at least one of diammonium hydrogen phosphate, ammonium dihydrogen phosphate and phosphoric acid.

[0085] In some embodiments of the present invention, preferably, the molecular sieve treated with phosphoric acid is washed with water, and the washing conditions include: the washing temperature is 20-50°C, preferably 25-40°C; the washing time is 1-10h, preferably 2-6h; the weight ratio of water to molecular sieve is 2-10, preferably 4-8.

[0086] In the present invention, the binder-free ZSM-5 molecular sieve containing rare earth elements after phosphoric acid treatment is contacted with water for water washing treatment, so as to solve the problem of a large amount of phosphorus blocking the pores of the molecular sieve, reduce the amount of pore blocking, improve the activity stability of the catalyst, and extend the catalyst regeneration cycle. The number of times of water washing is not particularly limited, preferably one water washing. Since the preparation method adopted in the present invention makes the phosphoric acid loading higher than the conventional method, the partial loss of phosphorus after water washing will not affect the catalytic performance of the catalyst.

[0087] In the present invention, the method for preparing the binder-free ZSM-5 molecular sieve catalyst may further include the steps of drying and calcining the catalyst after water washing. There is no particular requirement for the drying method, for example, it can be carried out in a drying oven at 130-150° C. for 4-15 hours. There is no particular limitation on the calcination conditions, and it can be calcined at 450-600° C. for 4-15 hours.

[0088] The third aspect of the present invention provides a use of the binderless ZSM-5 molecular sieve catalyst described in the first aspect or the binderless ZSM-5 molecular sieve catalyst prepared by the method described in the second aspect in the alkylation reaction of benzene and ethanol to produce ethylbenzene.

[0089] In the present invention, the application includes a vapor phase alkylation reaction of benzene and ethanol in the presence of the ZSM-5 molecular sieve catalyst. Preferably, the reaction temperature is 250-450°C, the reaction pressure is 0.7-1.5 MPa, the molar ratio of benzene to ethanol is 3-15:1, and the mass space velocity of ethanol is 0.5-5.0 h -1 .

[0090] The present invention will be described in detail below through examples.

[0091] In the following examples and comparative examples, unless otherwise specified, percentages refer to percentages by mass.

[0092] Preparation Example 1

[0093] Preparation of ZSM-5 molecular sieve seed crystals: Using alkaline silica sol (40% content), 18-hydrate and aluminum sulfate, tetrapropylammonium hydroxide (TPAOH) and water as raw materials, according to the material ratio (molar ratio): SiO2 / Al2O3=300, TPAOH / SiO2=0.25, H2O / SiO2=15, crystallize at 140°C for 70 hours under stirring conditions in a stainless steel kettle to obtain a slurry material for stand-by use, in which the SiO2 content is about 20wt%.

[0094] Example 1

[0095] (1) Weigh 7.3 g of the ZSM-5 molecular sieve seed crystals described in Preparation Example 1, 40.2 g of silicon powder, 11 g of silica sol (40% content), 1.65 g of aluminum sulfate 18hydrate, 1.22 g of lanthanum nitrate hexahydrate, 0.45 g of methyl cellulose (Aldrich, M0512) and 19.1 g of nitric acid aqueous solution (7 wt% concentration), mix them evenly, then knead and extrude them into strips, and dry them at 150° C. for 8 h to obtain a cylindrical strip ZSM-5 molecular sieve precursor with a diameter of 2 mm, wherein SiO2 / Al2O3 in the ZSM-5 molecular sieve precursor is 300;

[0096] (2) contacting the 10 g ZSM-5 molecular sieve precursor with 15 g ethylamine solution (50 wt % concentration), placing it in a microwave reactor, and performing a crystallization reaction for 7 h at a microwave power of 400 W and a temperature of 100 ° C., washing the crystallized product, and then drying it at 150 ° C. for 6 h, and then calcining it at 580 ° C. for 4 h to obtain a binder-free ZSM-5 molecular sieve containing lanthanum oxide;

[0097] (3) The binderless ZSM-5 molecular sieve containing lanthanum oxide is subjected to steam treatment at 570°C for 5 hours, and then immersed in a 0.5 mol / L phosphoric acid solution at 40°C for 5 hours, wherein the weight ratio of the phosphoric acid solution to the binderless ZSM-5 molecular sieve is 3.5:1. After drying, the mixture is calcined at 500°C for 5 hours. The calcined solid is immersed in deionized water at 30°C for 2 hours, wherein the weight ratio of the deionized water to the solid is 3:1. After drying, the mixture is calcined at 530°C for 4 hours to obtain a binderless ZSM-5 molecular sieve catalyst.

[0098] The binder-free ZSM-5 molecular sieve catalyst has a La2O3 content of 1%, a P2O5 content of 0.5%, a molar ratio of phosphorus to silicon on the catalyst surface of 1:50, and a micropore volume of 0.165 cm 3 / g. The performance parameters of the catalyst are shown in Table 1.

[0099] The NH3-TPD diagram of the binder-free ZSM-5 molecular sieve catalyst is as follows Figure 1 As shown, from Figure 1 It can be seen that there are two peaks on NH3-TPD, among which the highest position of the first peak is at 192°C, the highest position of the second peak is at 361°C, and the ratio of the peak heights of the first peak and the second peak is 1:0.98.

[0100] The scanning electron microscope image of the binder-free ZSM-5 molecular sieve catalyst is as follows: Figure 2 As shown, from Figure 2 It can be seen that the microscopic morphology of the binder-free ZSM-5 molecular sieve in the catalyst is long strip-shaped grains.

[0101] Example 2

[0102] (1) Weigh 3.2 g of the ZSM-5 molecular sieve seed crystals described in Preparation Example 1, 32.5 g of silicon powder, 20 g of silica sol (40% content), 2.25 g of aluminum sulfate 18hydrate, 2.4 g of lanthanum nitrate hexahydrate, 0.25 g of sesbania powder and 13.6 g of nitric acid aqueous solution (5.5 wt% concentration), mix them evenly, then knead and extrude them into strips, and dry them at 150° C. for 8 h to obtain a cylindrical strip ZSM-5 molecular sieve precursor with a diameter of 2 mm, wherein SiO2 / Al2O3 in the ZSM-5 molecular sieve precursor is 200;

[0103] (2) contacting the 10 g ZSM-5 molecular sieve precursor with 15 g n-butylamine solution (50 wt % concentration), placing it in a microwave reactor, and performing a crystallization reaction for 8 h at a microwave power of 500 W and a temperature of 90 ° C., washing the crystallized product, and then drying it at 150 ° C. for 6 h, and then calcining it at 580 ° C. for 4 h to obtain a binder-free ZSM-5 molecular sieve containing lanthanum oxide;

[0104] (3) The binderless ZSM-5 molecular sieve containing lanthanum oxide is subjected to steam treatment at 530°C for 8 hours, and then immersed in a 0.3 mol / L phosphoric acid solution at 60°C for 5 hours, wherein the weight ratio of the phosphoric acid solution to the binderless ZSM-5 molecular sieve is 5:1. After drying, the mixture is calcined at 500°C for 5 hours. The calcined solid is immersed in deionized water at 28°C for 5 hours, wherein the weight ratio of the deionized water to the solid is 5:1. After drying, the mixture is calcined at 530°C for 4 hours to obtain a binderless ZSM-5 molecular sieve catalyst.

[0105] The binder-free ZSM-5 molecular sieve catalyst has a La2O3 content of 2.2%, a P2O5 content of 0.2%, a molar ratio of phosphorus to silicon on the catalyst surface of 1:73, and a micropore volume of 0.155 cm 3 / g. The performance parameters of the catalyst are shown in Table 1.

[0106] The binderless ZSM-5 molecular sieve catalyst has two peaks on the NH3-TPD, wherein the highest position of the first peak is at 185°C, the highest position of the second peak is at 353°C, and the ratio of the peak heights of the first peak to the second peak is 1:1.03.

[0107] Example 3

[0108] (1) Weigh 4.3 g of the ZSM-5 molecular sieve seed crystals described in Preparation Example 1, 38.3 g of silicon powder, 15.6 g of silica sol (40% content), 2.25 g of aluminum sulfate 18hydrate, 2.4 g of lanthanum nitrate hexahydrate, 0.4 g of sesbania powder and 18.3 g of nitric acid aqueous solution (6.5 wt% concentration), mix them evenly, then knead and extrude them into strips, and dry them at 150° C. for 8 h to obtain a cylindrical strip ZSM-5 molecular sieve precursor with a diameter of 2 mm, wherein SiO2 / Al2O3 in the ZSM-5 molecular sieve precursor is 340;

[0109] (2) contacting the 10 g ZSM-5 molecular sieve precursor with 15 g ethylamine solution (50 wt % concentration), placing it in a microwave reactor, and performing a crystallization reaction for 7 h at a microwave power of 400 W and a temperature of 100 ° C., washing the crystallized product, and then drying it at 150 ° C. for 6 h, and then calcining it at 580 ° C. for 4 h to obtain a binder-free ZSM-5 molecular sieve containing lanthanum oxide;

[0110] (3) The binderless ZSM-5 molecular sieve containing lanthanum oxide is treated with steam at 570°C for 5 hours, then immersed in a 0.5 mol / L phosphoric acid solution at 50°C for 5 hours, the weight ratio of the phosphoric acid solution to the binderless ZSM-5 molecular sieve is 7:1, and then dried and calcined at 500°C for 5 hours. The calcined solid is immersed in deionized water at 30°C for 4.5 hours, the weight ratio of deionized water to the solid is 4.5:1, and then dried and calcined at 530°C for 4 hours to obtain a binderless ZSM-5 molecular sieve catalyst.

[0111] The binder-free ZSM-5 molecular sieve catalyst has a La2O3 content of 0.3%, a P2O5 content of 0.3%, a molar ratio of phosphorus to silicon on the catalyst surface of 1:62, and a micropore volume of 0.16 cm 3 / g. The performance parameters of the catalyst are shown in Table 1.

[0112] The binderless ZSM-5 molecular sieve catalyst has two peaks on the NH3-TPD, wherein the highest position of the first peak is at 197° C., the highest position of the second peak is at 369° C., and the ratio of the peak heights of the first peak to the second peak is 1:1.07.

[0113] Example 4

[0114] The method of Example 1 is followed, except that in step (3), the concentration of the phosphoric acid solution used is 0.07 mol / L, to obtain a binder-free ZSM-5 molecular sieve catalyst.

[0115] The binder-free ZSM-5 molecular sieve catalyst has a La2O3 content of 1%, a P2O5 content of 0.14%, a molar ratio of phosphorus to silicon on the catalyst surface of 1:85, and a micropore volume of 0.17 cm 3 / g. The performance parameters of the catalyst are shown in Table 1.

[0116] The binderless ZSM-5 molecular sieve catalyst has two peaks on the NH3-TPD, wherein the highest position of the first peak is at 204° C., the highest position of the second peak is at 372° C., and the ratio of the peak heights of the first peak to the second peak is 1:1.02.

[0117] Example 5

[0118] The method of Example 2 is followed, except that in step (3), the water washing condition is soaking in deionized water at 25° C. for 1.5 hours, and the weight ratio of deionized water to the solid is 2.5:1, to obtain a binder-free ZSM-5 molecular sieve catalyst.

[0119] The binder-free ZSM-5 molecular sieve catalyst has a La2O3 content of 2.2%, a P2O5 content of 0.65%, a molar ratio of phosphorus to silicon on the catalyst surface of 1:31, and a micropore volume of 0.14 cm 3 / g. The performance parameters of the catalyst are shown in Table 1.

[0120] The binderless ZSM-5 molecular sieve catalyst has two peaks on the NH3-TPD, wherein the highest position of the first peak is at 175°C, the highest position of the second peak is at 346°C, and the ratio of the peak heights of the first peak to the second peak is 1:0.92.

[0121] Example 6

[0122] The method of Example 1 is followed, except that in step (1), 1.22 g of lanthanum nitrate hexahydrate is replaced with 3.92 g of cerium nitrate to obtain a binder-free ZSM-5 molecular sieve catalyst.

[0123] The CeO2 content of the binder-free ZSM-5 molecular sieve catalyst is 4.5%, the phosphorus pentoxide content is 0.45%, the molar ratio of phosphorus to silicon on the catalyst surface is 1:5, and the micropore volume of the catalyst is 0.135 cm 3 / g. The performance parameters of the catalyst are shown in Table 1.

[0124] The binderless ZSM-5 molecular sieve catalyst has two peaks on the NH3-TPD, wherein the highest position of the first peak is at 171° C., the highest position of the second peak is at 342° C., and the ratio of the peak heights of the first peak to the second peak is 1:0.93.

[0125] Comparative Example 1

[0126] The method of Example 1 is followed, except that in step (3), no steam treatment, phosphoric acid treatment and water washing treatment are performed to obtain a binder-free ZSM-5 molecular sieve catalyst.

[0127] The binder-free ZSM-5 molecular sieve catalyst has a La2O3 content of 1% and contains no phosphorus. The micropore volume of the catalyst is 0.176 cm 3 / g. The performance parameters of the catalyst are shown in Table 1.

[0128] The binderless ZSM-5 molecular sieve catalyst has two peaks on NH3-TPD, wherein the highest position of the first peak is at 215°C, the highest position of the second peak is at 387°C, and the ratio of the peak heights of the first peak to the second peak is 1:1.3.

[0129] Comparative Example 2

[0130] The method of Example 1 is followed, except that in step (1), lanthanum nitrate hexahydrate is not added, and an equal amount of lanthanum oxide is loaded on the binderless ZSM-5 molecular sieve by impregnation, and the remaining steps and conditions are the same to obtain a binderless ZSM-5 molecular sieve catalyst.

[0131] The binder-free ZSM-5 molecular sieve catalyst has a La2O3 content of 1%, a phosphorus pentoxide content of 0.45%, a molar ratio of phosphorus to silicon on the catalyst surface of 1:50, and a micropore volume of 0.125 cm 3 / g. The performance parameters of the catalyst are shown in Table 1.

[0132] The binderless ZSM-5 molecular sieve catalyst has two peaks on the NH3-TPD, wherein the highest position of the first peak is at 185°C, the highest position of the second peak is at 352°C, and the ratio of the peak heights of the first peak to the second peak is 1:0.95.

[0133] Comparative Example 3

[0134] The method of Example 1 is followed, except that in step (1), the amount of aluminum sulfate 18hydrate is changed to 11 g, to obtain a binder-free ZSM-5 molecular sieve catalyst.

[0135] The binder-free ZSM-5 molecular sieve catalyst has a La2O3 content of 1%, a phosphorus pentoxide content of 0.45%, a molar ratio of phosphorus to silicon on the catalyst surface of 1:52, and a micropore volume of 0.162 cm 3 / g. The performance parameters of the catalyst are shown in Table 1.

[0136] There are two peaks on the NH3-TPD graph of the binderless ZSM-5 molecular sieve catalyst, wherein the highest position of the first peak is at 198°C, the highest position of the second peak is at 375°C, and the ratio of the peak heights of the first peak to the second peak is 1:1.3.

[0137] Comparative Example 4

[0138] The method of Example 1 is followed, except that in step (3), no water washing treatment is performed to obtain a binder-free ZSM-5 molecular sieve catalyst.

[0139] The binder-free ZSM-5 molecular sieve catalyst has a La2O3 content of 1%, a P2O5 content of 1.5%, a molar ratio of phosphorus to silicon on the catalyst surface of 1:15, and a micropore volume of 0.12 cm 3 / g. The performance parameters of the catalyst are shown in Table 1.

[0140] The binderless ZSM-5 molecular sieve catalyst has two peaks on the NH3-TPD, wherein the highest position of the first peak is at 182° C., the highest position of the second peak is at 351° C., and the ratio of the peak heights of the first peak to the second peak is 1:0.85.

[0141] Test Example 1

[0142] The binderless ZSM-5 molecular sieve catalyst was used for the continuous fixed bed vapor phase alkylation reaction of benzene and ethanol. The reaction activity and selectivity of the catalyst were evaluated. The alkylation reaction conditions included: temperature of 360°C, pressure of 0.7 MPa, benzene / alcohol feed molar ratio of 6:1, and ethanol mass space velocity of 1.0 h -1 The reaction reached a stable state after 4 hours. The reaction results are shown in Table 2.

[0143] Test Example 2

[0144] The ZSM-5 molecular sieve catalyst was used for the gas-phase alkylation reaction of benzene and ethanol in a continuous fixed bed. The activity stability of the catalyst, i.e., the regeneration cycle of the catalyst, was evaluated. The alkylation reaction conditions included: a temperature of 400°C, a pressure of 1 MPa, a benzene / alcohol feed molar ratio of 1:1, and an ethanol mass space velocity of 3.0 h -1 , the reaction time was 100h, and the reaction results are shown in Table 3.

[0145] Table 1

[0146]

[0147] Table 2

[0148]

[0149]

[0150] Table 3

[0151]

[0152] From the results in Table 1, it can be seen that the binderless ZSM-5 molecular sieve catalyst obtained by the method of the present invention has a high ethanol conversion rate and ethyl selectivity, a low content of xylene impurities in ethylbenzene, and exhibits excellent activity stability. From Examples 1-6 in Table 1, it can be seen that the ethanol conversion rate of the binderless ZSM-5 molecular sieve catalyst obtained by the method of the present invention is ≥99.5%, the ethyl selectivity is greater than 99.2%, the xylene content in the obtained ethylbenzene product is low, and can reach below 650ppm, and the deactivation rate per hour under harsh reaction conditions is ≤0.025%; compared with Example 1, Comparative Examples 1 to Comparative Examples 4 do not use the method defined by the present invention to prepare the catalyst, and the obtained catalyst cannot have good ethyl selectivity and activity at the same time, and the activity stability under harsh conditions is poor.

[0153] The preferred embodiments of the present invention are described in detail above, 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 combination of various technical features 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 binder-free ZSM-5 molecular sieve catalyst, characterized in that: The catalyst comprises the following components by weight percentage: a) 94.5-99.5% of a binderless ZSM-5 molecular sieve having a silicon-aluminum molar ratio SiO2 / Al2O3 of 50-400 and a maximum distance between any two points on a grain of 500-1000 nm; b) 0.1-5% of rare earth metal oxides; c) 0.1-1% of phosphorus pentoxide; Among them, according to XPS testing, the molar ratio of phosphorus element to silicon element on the catalyst surface is 1:10-100.

2. The catalyst according to claim 1, wherein The micropore volume of the catalyst is 0.13-0.18 cm 3 / g, preferably 0.14-0.17cm 3 / g; Preferably, after NH3-TPD testing, the catalyst has two peaks, wherein the highest position of the first peak is at 170-210°C, preferably 180-200°C, the highest position of the second peak is at 340-380°C, preferably 350-370°C, and the ratio of the peak heights of the first peak to the second peak is 1:0.9-1.

1.

3. The catalyst according to claim 1 or 2, wherein The binderless ZSM-5 molecular sieve has a silicon-aluminum molar ratio SiO2 / Al2O3 of 200-350; Preferably, the binder-free ZSM-5 molecular sieve is an elongated grain, and the longest distance between any two points on the grain is 550-900 nm; Preferably, in terms of weight percentage of the catalyst, the content of the binder-free ZSM-5 molecular sieve in the catalyst is 97-98.5%; the content of the rare earth metal oxide is 0.3-2.5%; and the content of phosphorus pentoxide is 0.2-0.5%; Preferably, according to XPS testing, the molar ratio of phosphorus to silicon on the catalyst surface is 1:40-80.

4. The catalyst according to any one of claims 1 to 3, wherein The rare earth metal oxide is selected from lanthanide metal oxides, preferably at least one selected from lanthanum oxide, cerium oxide and praseodymium oxide, more preferably lanthanum oxide.

5. A method for preparing a binder-free ZSM-5 molecular sieve catalyst, characterized in that: The method comprises the following steps: (1) kneading ZSM-5 seed crystals, an aluminum source, a binder, a rare earth metal salt and optional additives, forming the mixture, and drying the mixture to obtain a ZSM-5 molecular sieve precursor; (2) crystallizing the ZSM-5 molecular sieve precursor and performing solid-liquid separation to obtain a binder-free ZSM-5 molecular sieve containing rare earth elements; (3) treating the binder-free ZSM-5 molecular sieve containing rare earth elements with steam, phosphoric acid and water, and drying to obtain a binder-free ZSM-5 molecular sieve catalyst; Calculated by weight percentage of the catalyst, the content of the binder-free ZSM-5 molecular sieve in the catalyst is 94.5-99.5%; the content of the rare earth metal oxide is 0.1-5%; and the content of phosphorus pentoxide is 0.1-1%.

6. The method according to claim 5, wherein: In terms of weight percentage of the catalyst, the content of the binder-free ZSM-5 molecular sieve in the catalyst is 97-98.5%; the content of the rare earth metal oxide is 0.3-2.5%; and the content of phosphorus pentoxide is 0.2-0.5%; Preferably, in step (1), the ZSM-5 seed crystal is ZSM-5 molecular sieve raw powder; Preferably, based on the weight of total SiO2 in the ZSM-5 molecular sieve precursor, the content of the ZSM-5 seed crystals in terms of SiO2 is 0-15% and not 0, preferably 0.5-5%; Preferably, the aluminum source is an aluminum salt, preferably at least one selected from aluminum sulfate, aluminum nitrate, aluminum acetate, aluminum chloride and their hydrates, preferably aluminum sulfate; Preferably, the binder is selected from at least one of silicon powder, white carbon black and silica sol, preferably selected from at least two of silicon powder, white carbon black and silica sol, more preferably silicon powder and silica sol; Preferably, the binder is calculated as SiO2, the aluminum source is calculated as Al2O3, and the SiO2 / Al2O3 molar ratio is 50-400, preferably 200-350; Preferably, based on the total weight of SiO2 and Al2O3 in the binderless ZSM-5 molecular sieve catalyst, the content of the rare earth metal salt in terms of oxide is 0.1-5%, preferably 0.2-3.5%.

7. The method according to claim 5 or 6, wherein: In step (1), the additive is selected from a pore-forming agent and / or an aqueous solution of an acid; Preferably, the pore-forming agent is selected from methylcellulose and / or sesbania powder; Preferably, the amount of the pore-forming agent is 0.2-1% of the total weight of the raw materials added in step (1); Preferably, the acid is selected from any one of nitric acid, hydrochloric acid, sulfuric acid and oxalic acid, preferably nitric acid; Preferably, the concentration of the aqueous solution of the acid is 1-10 wt%, preferably 5-8 wt%; Preferably, the amount of the acid aqueous solution used is 10-40% of the total weight of the raw materials added in step (1).

8. The method according to any one of claims 5 to 7, wherein: In step (2), the specific steps of crystallization include: mixing the ZSM-5 molecular sieve precursor and the organic amine solution, and then crystallizing under microwave conditions; Preferably, the organic amine is selected from at least one of ethylamine, n-propylamine and n-butylamine; Preferably, the organic amine solution is an aqueous solution of an organic amine; Preferably, the concentration of the organic amine solution is 40-70wt%; Preferably, the mass ratio of the ZSM-5 molecular sieve precursor to the organic amine solution is 1:1.2-2; Preferably, the crystallization conditions include: crystallization temperature of 80-110° C., crystallization time of 2-12 h, and microwave power of 200-1000 W.

9. The method according to any one of claims 5 to 8, wherein: In step (3), the conditions of the water vapor treatment include: the pressure of the water vapor treatment is normal pressure, the temperature is 400-650° C., and the time is 4-10 hours; Preferably, the molecular sieve treated with water vapor is treated with phosphoric acid solution, and the conditions of the phosphoric acid treatment include: the concentration of the phosphoric acid solution is 0.05-2 mol / L, preferably 0.1-0.5 mol / L; the phosphoric acid treatment temperature is 20-90° C., preferably 40-70° C.; the phosphoric acid treatment time is 2-15 h, preferably 4-8 h; the weight ratio of the phosphoric acid solution to the molecular sieve is 2-10, preferably 3-8; Preferably, the phosphoric acid solution is an aqueous solution of at least one selected from diammonium hydrogen phosphate, ammonium dihydrogen phosphate and phosphoric acid; Preferably, the molecular sieve treated with phosphoric acid is washed with water, and the washing conditions include: the washing temperature is 20-50°C, preferably 25-40°C; the washing time is 1-10h, preferably 2-6h; the weight ratio of water to molecular sieve is 2-10, preferably 4-8.

10. Use of the binderless ZSM-5 molecular sieve catalyst according to any one of claims 1 to 4 or the binderless ZSM-5 molecular sieve catalyst prepared by the method according to any one of claims 5 to 9 in the alkylation reaction of benzene and ethanol to produce ethylbenzene.

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