A binder-free ZSM-5 molecular sieve catalyst, its preparation method and application

Abstract

The present invention discloses a binderless ZSM-5 molecular sieve catalyst and a preparation method thereof. The present invention also discloses the application of the binderless ZSM-5 molecular sieve catalyst in the gas-phase alkylation reaction of benzene with ethylene or benzene with ethanol to produce ethylbenzene. The catalyst of the present invention exhibits high selectivity in the reaction of gas-phase alkylation of benzene with ethylene or benzene with ethanol to produce ethylbenzene, and the content of the key impurity xylene in the product is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of molecular sieves, and particularly relates to a binderless ZSM-5 molecular sieve catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] ZSM-5 is a microporous molecular sieve with a pore system composed of 10-membered oxygen rings, having medium-sized pore diameters and pore orifices, no cages in the pore orientation, being not easily carbon-deposited during the catalytic process, and having good hydrothermal stability, suitable acidity, good acid and alkali resistance, and hydrophobicity. Due to the high selectivity, high activity, and resistance to carbon deposition and inactivation of ZSM-5 zeolite, it has been widely used as an industrial catalyst.

[0003] Industrially, ZSM-5 is used as a catalyst for the gas-phase alkylation of benzene and ethylene to produce ethylbenzene. In order to meet industrial requirements, especially size and strength requirements, molecular sieves, binders, additives, etc. need to be mixed and formed into a catalyst with a certain size and strength. However, the addition of binders and additives will cover the active centers of the molecular sieves and at the same time limit the content of molecular sieves in the catalyst. To overcome the above problems, Patent CN103030156B discloses a synthesis method of binderless ZSM-5 molecular sieve, which converts the binder into ZSM-5 molecular sieve through vapor-phase transformation. The above method first synthesizes ZSM-5 powder and then adds a binder for forming, and then prepares binderless ZSM-5 molecular sieve through transformation. Most of the formed product is ZSM-5 during the forming process, while the binder is in a small part. Therefore, it is a secondary transformation in the synthesis, with a complex operation process and a long crystallization time. In addition, although the binder is transformed into the ZSM-5 crystal form, it does not contain acid centers. CN107512729A adds an aluminum source in the transformation step to make the binder also contain acidic centers, but secondary transformation is still required in the synthesis. The crystallization of the above schemes needs to be carried out at a temperature above 130 °C, and the formed bars are easily broken during the stirring in the transformation process, and uneven heating is easily caused during the traditional mass transfer heating process, resulting in uneven crystallization. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a binderless ZSM-5 molecular sieve catalyst and a preparation method thereof, and further provide its application in the reaction of gas-phase alkylation of benzene and ethylene or ethanol to produce ethylbenzene. The method of the present invention has a low crystallization temperature, a short crystallization time, and uniform heating during the crystallization process, resulting in uniform crystallization. The prepared ZSM-5 molecular sieve catalyst can be controlled to have a suitable strength (60 - 100 N / cm), and when used in the reaction of gas-phase alkylation of benzene and ethylene or ethanol to produce ethylbenzene, it can have higher selectivity and reduce the generation of by-product xylene in the reaction.

[0005] To this end, a first aspect of the present invention provides a binderless ZSM-5 molecular sieve catalyst. The ZSM-5 molecular sieve catalyst has two peaks in NH 3 -TPD. Among them, the highest position of the first peak is at 170-210 °C, and the highest position of the second peak is at 380-420 °C. The ratio of the peak heights of the first peak and the second peak is 1:(1.0-1.5);

[0006] The ZSM-5 molecular sieve catalyst includes elongated grains and spherical-like grains with a particle size of 20-100 nm. The longest distance between any two points on the elongated grains is 500-1000 nm. Among them, the spherical-like grains account for 60-80% of the total weight of the ZSM-5 molecular sieve catalyst, and the elongated grains account for 20-40% of the total weight of the ZSM-5 molecular sieve catalyst;

[0007] The elongated grains include cuboid grains. The lengths of the a-axis and b-axis of the cuboid grains are the same or different, independently 50-100 nm, the length of the c-axis of the cuboid grains is 500-1000 nm, and the cuboid grains account for 20-30% of the total weight of the elongated grains.

[0008] According to the present invention, the a-axis, b-axis, and c-axis are relative concepts. Among them, the a-axis and b-axis respectively refer to the smaller two of the length, width, and height of the cuboid, and the c-axis refers to the largest of the length, width, and height of the cuboid.

[0009] A second aspect of the present invention provides a preparation method of the binderless ZSM-5 molecular sieve catalyst as described in the first aspect of the present invention, which includes the following steps:

[0010] 1) Knead ZSM-5 seeds, an aluminum source, a binder, and an optional additive and then form them, and dry to obtain a ZSM-5 molecular sieve precursor;

[0011] 2) Subject the ZSM-5 molecular sieve precursor prepared in step 1) to liquid-phase crystallization under microwave conditions, and perform solid-liquid separation to obtain a crystallized solid product;

[0012] 3) Wash, dry, exchange, and calcine the obtained crystallized solid product to obtain the ZSM-5 molecular sieve catalyst.

[0013] According to the present invention, the ZSM-5 seeds in the present invention are conventional or known seeds in the art and can be synthesized by conventional or known methods in the art, such as hydrothermal crystallization method.

[0014] According to some embodiments of the present invention, the ZSM-5 seeds are prepared by hydrothermal crystallization by mixing a silicon compound, an aluminum compound, an alkali, and a template agent.

[0015] According to some embodiments of the present invention, the molar ratio of the silicon compound, aluminum compound, base, and template agent is 1:(0.001 - 0.02):(0.1 - 0.5):(0.1 - 1.0):(6 - 20).

[0016] According to some embodiments of the present invention, the temperature of the hydrothermal crystallization is 100 - 170 °C, and the time of the hydrothermal crystallization is 48 - 96 h.

[0017] According to some embodiments of the present invention, the silicon compound is selected from at least one of silica sol, water glass, silicon powder, and silica white.

[0018] According to some embodiments of the present invention, the aluminum compound is selected from at least one of aluminum sulfate, aluminum chloride, and aluminum alkoxide.

[0019] According to some embodiments of the present invention, the base is selected from bases with alkali metals or alkaline earth metals as cations or template agents with strong alkalinity such as tetrapropylammonium hydroxide and tetraethylammonium hydroxide.

[0020] According to some embodiments of the present invention, the template agent is selected from at least one of tetrapropylammonium hydroxide, tetrapropylammonium bromide, ethylamine, n-propylamine, and n-butylamine.

[0021] According to some embodiments of the present invention, in step 1), the ZSM-5 seed crystal can be a slurry material or a powdery material after solid separation, washing, and drying.

[0022] According to some embodiments of the present invention, in step 1), the ZSM-5 seed crystal is the ZSM-5 molecular sieve raw powder.

[0023] According to some embodiments of the present invention, in the ZSM-5 seed crystal, SiO 2 accounts for 0 - 15% and is not 0, preferably 1 - 15%, of the total SiO 2 by weight in the ZSM-5 molecular sieve precursor.

[0024] According to some embodiments of the present invention, the molar ratio of SiO 2 in the binder to Al 2 O 3 in the aluminum source is 50 - 400.

[0025] According to some embodiments of the present invention, the molar ratio of SiO 2 in the ZSM-5 molecular sieve precursor to Al 2 O 3 in the aluminum source is 50 - 350.

[0026] According to some embodiments of the present invention, in step 1), the aluminum source is an aluminum salt, preferably at least one selected from aluminum sulfate, aluminum nitrate, aluminum acetate and their hydrates.

[0027] According to some embodiments of the present invention, in step 1), the binder is at least one of silicon powder, silica white and silica sol.

[0028] According to some embodiments of the present invention, in step 1), the additive includes a pore-forming agent and an aqueous acid solution.

[0029] According to some embodiments of the present invention, the aqueous acid solution is an aqueous nitric acid solution, and preferably the weight content of the aqueous nitric acid solution is 1-10%.

[0030] According to some embodiments of the present invention, in step 1), the amount of the aqueous nitric acid solution is 10-40% of the total weight of the reaction raw materials. In some embodiments, the total weight of the added reaction raw materials refers to the total weight of ZSM-5 seed crystals, aluminum source, binder and pore-forming agent.

[0031] According to some embodiments of the present invention, the pore-forming agent is selected from at least one of methyl cellulose and sesbania powder.

[0032] According to some embodiments of the present invention, the amount of the pore-forming agent is 0.2%-1% of the total weight of the raw materials added in step 1). In some embodiments, the total weight of the added reaction raw materials refers to the total weight of ZSM-5 seed crystals, aluminum source, binder and pore-forming agent.

[0033] According to some embodiments of the present invention, in step 1), the forming is extrusion forming.

[0034] According to some embodiments of the present invention, in step 1), the drying is to dry the formed strips at 100-180°C for 4h-48h.

[0035] According to some embodiments of the present invention, the liquid-phase crystallization under microwave conditions in step (2) includes mixing the ZSM-5 molecular sieve precursor and the organic amine solution and then carrying out crystallization under microwave conditions.

[0036] According to some embodiments of the present invention, the temperature of the crystallization in step (2) is 80-110°C.

[0037] According to some embodiments of the present invention, the time of the crystallization in step (2) is 2-12h.

[0038] According to some embodiments of the present invention, the frequency of the microwave in step (2) is 200-1000W.

[0039] According to some embodiments of the present invention, in step 2), the weight ratio of the organic amine solution to the ZSM-5 molecular sieve precursor is (0.8 - 3):1.

[0040] According to some embodiments of the present invention, in step 2), the organic amine is selected from at least one of ethylamine, n-propylamine, and n-butylamine.

[0041] According to some embodiments of the present invention, the organic amine solution is an aqueous solution of an organic amine, and the concentration of the organic amine solution is 40 - 70% wt.

[0042] According to some embodiments of the present invention, in step 3), the exchange is an acid exchange, and preferably the acid is at least one of HCl, HNO 3 and H 2 SO 4 in it.

[0043] According to some embodiments of the present invention, in step 3), the concentration of the acid for the acid exchange is 0.1 mol / L - 1 mol / L.

[0044] According to some embodiments of the present invention, the number of times of the acid exchange is 1 - 3 times.

[0045] According to some embodiments of the present invention, the weight ratio of the acid to the solid product in the acid exchange is 3:1 - 20:1.

[0046] According to some embodiments of the present invention, the exchange is to use HCl, HNO with a concentration of 0.1 - 1 mol / L 3 and H 2 SO 4 in it to exchange 2 times, the exchange temperature is 0 - 50°C, and the liquid-solid weight ratio is 3 / 1 - 20 / 1.

[0047] According to some embodiments of the present invention, in step 3), the temperature of the calcination is 450 - 600°C, and the time of the calcination is 2 - 12 h.

[0048] The third aspect of the present invention provides an application of the ZSM-5 molecular sieve catalyst as described in the first aspect of the present invention or the ZSM-5 molecular sieve catalyst prepared by the preparation method as described in the second aspect of the present invention in the gas-phase alkylation reaction of benzene with ethylene or benzene with ethanol to produce ethylbenzene.

[0049] According to some embodiments of the present invention, the application includes carrying out a gas-phase alkylation reaction of benzene and ethylene or 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 0.1 - 1.5 MPa, the reaction benzene / ethylene (or benzene / ethanol) ratio is 3 / 1 - 15 / 1, and the ethylene mass space velocity is 1.5 - 5.0 h-1 。

[0050] Advantages of the present invention:

[0051] 1) The method of the present invention has a low crystallization temperature, a short crystallization time, is simple to operate, and saves costs.

[0052] 2) During the crystallization process of the method of the present invention, the heat is evenly distributed, so the crystallization is uniform. The prepared ZSM-5 molecular sieve catalyst can be controlled to have a suitable strength of 60-100 N / cm.

[0053] 3) The binderless ZSM-5 molecular sieve catalyst of the present invention can have higher selectivity in the gas-phase alkylation of benzene with ethylene or ethanol to produce ethylbenzene, especially reducing the generation of the key impurity xylene in the reaction products. Brief description of the drawings

[0054] Figure 1 XRD pattern of the binderless ZSM-5 molecular sieve catalyst prepared in Example 1.

[0055] Figure 2 NH 3 -TPD pattern of the binderless ZSM-5 molecular sieve catalyst prepared in Example 1.

[0056] Figure 3 SEM image of the binderless ZSM-5 molecular sieve catalyst prepared in Example 1.

[0057] Figure 4 SEM image of the binderless ZSM-5 molecular sieve catalyst prepared in Comparative Example 1. Detailed description of the specific embodiments

[0058] To make the present invention easier to understand, the present invention will be described in detail below in conjunction with the examples and the drawings. These examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. Unless otherwise specified, the materials used in the examples are all commercially available products or conventional products that can be synthesized by known methods.

[0059] In the ranges disclosed herein, the endpoints and any value are not limited to the exact range or value. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0060] Preparation Example 1

[0061] a) Synthesis of ZSM-5 molecular sieve seeds: Using alkaline silica sol, aluminum sulfate octadecahydrate, tetrapropylammonium hydroxide (TPAOH) and water as raw materials, with the material ratio (molar ratio) being: SiO 2 / Al 2 O 3 = 300, TPAOH / SiO 2 = 0.25, H 2 O / SiO 2 = 15, crystallizing at 140 °C for 70 h under stirring conditions in a stainless steel autoclave to obtain a slurry material for use, where the SiO 2 content is approximately 20%.

[0062] b) Preparation of binderless ZSM-5 molecular sieve precursor: Mix 7.3 g of the above ZSM-5 molecular sieve seeds, 40.4 g of silicon powder, 10.3 g of alkaline silica sol (40% content), 1.65 g of aluminum sulfate octadecahydrate, 0.5 g of methyl cellulose, and 21.3 g of nitric acid aqueous solution (7% concentration) evenly. In this mixture, SiO 2 / Al 2 O 3 = 300. Obtain cylindrical ZSM-5 molecular sieve precursor with a diameter of 2.0 mm by kneading and extrusion molding, and dry it at 150 °C for 8 h.

[0063] c) Place 10 g of the above ZSM-5 molecular sieve precursor in 15 g of 50% ethylamine solution, place it in a microwave reactor, heat to 100 °C, carry out a crystallization reaction at a microwave power of 400 W for 7 h. After washing the obtained product, exchange it 2 times with 0.25% mol / L sulfuric acid solution, with the exchange temperature being 40 °C and the liquid-solid weight ratio being 10 / 1. Dry it at 120 °C for 10 h, and then calcine it at 580 °C for 4 h to obtain a binderless ZSM-5 molecular sieve catalyst.

[0064] The XRD of the obtained binderless ZSM-5 molecular sieve catalyst product is as Figure 1 shown. From its spectrum, it can be seen that the diffraction peaks near 2Theta = 7.9°, 8.8°, 23.1°, 23.3°, 23.7°, 24.0°, 24.5° coincide with the characteristic diffraction peaks of ZSM-5 molecular sieve, indicating that ZSM-5 molecular sieve is obtained.

[0065] The TPD diagram of the obtained binderless ZSM-5 molecular sieve catalyst product is as Figure 2 shown. From Figure 2 it can be seen that there are two peaks in NH 3 -TPD. Among them, the highest position of the first peak is at 198 °C, the highest position of the second peak is at 391 °C, and the peak height ratio of the first peak to the second peak is 1:1.19.

[0066] The SEM images of the obtained binderless ZSM-5 molecular sieve catalyst products are as Figure 3 shown.

[0067] As a result, in the obtained binderless ZSM-5 molecular sieve catalyst product, the spherical grains with particle sizes in the range of 20 - 100 nm account for 72% of the total weight of the catalyst. Among them, the elongated grains with the longest distance between any two points in the range of 500 - 1000 nm account for 28% of the total weight of the catalyst, and the cuboid grains in the elongated grains account for 25%.

[0068] Preparation Example 2

[0069] The method is the same as that of Preparation Example 1, except that the crystallization condition is crystallization at 80 °C for 10 h. As a result, a binderless ZSM-5 molecular sieve is obtained. There are two peaks on NH3-TPD. Among them, the highest position of the first peak is at 196 °C, and the highest position of the second peak is at 387 °C. The peak height ratio of the first peak to the second peak is 1:1.22. The grains with particle sizes in the range of 20 - 100 nm in the catalyst product account for 78%, and the elongated grains with the longest distance between any two points of 500 - 1000 nm account for 28%. The cuboid grains in the elongated grains account for 21%.

[0070] Preparation Example 3

[0071] The method is the same as that of Preparation Example 1, except for the preparation of the binderless ZSM-5 molecular sieve precursor: 3.3 g of the above ZSM-5 molecular sieve seeds, 25.1 g of white carbon black, 29.5 g of alkaline silica sol (40% content), 1.65 g of aluminum sulfate octadecahydrate, 0.3 g of sesbania powder and 8.3 g of nitric acid aqueous solution (7% concentration) are mixed evenly. The SiO 2 / Al 2 O 3 in this mixture = 248. The cylindrical ZSM-5 molecular sieve precursor with a diameter of 2.0 mm is obtained by kneading and extrusion molding, and dried at 150 °C for 8 h. As a result, a binderless ZSM-5 molecular sieve is obtained. There are two peaks on NH 3 -TPD. Among them, the highest position of the first peak is at 191 °C, and the highest position of the second peak is at 402 °C. The peak height ratio of the first peak to the second peak is 1:1.32. The spherical grains with particle sizes in the range of 20 - 100 nm in the catalyst product account for 77%, and the elongated grains with the longest distance between any two points of 500 - 1000 nm account for 23%. The cuboid grains in the elongated grains account for 22%.

[0072] Preparation Example 4

[0073] The method was the same as that of Preparation Example 1, except for the preparation of the binderless ZSM-5 molecular sieve precursor: 7.3 g of the above ZSM-5 molecular sieve seeds, 40.4 g of silicon powder, 10.3 g of alkaline silica sol (40% content), 1.35 g of aluminum sulfate octadecahydrate, 0.5 g of methyl cellulose, and 24.9 g of nitric acid aqueous solution (7% concentration) were mixed evenly. In this mixture, SiO 2 / Al 2 O 3 = 366. The ZSM-5 molecular sieve precursor in the form of cylindrical bars with a diameter of 2.0 mm was obtained by kneading and extrusion molding, and dried at 150 °C for 8 h. As a result, a binderless ZSM-5 molecular sieve was prepared. There were two peaks on the NH 3 -TPD. Among them, the highest position of the first peak was at 193 °C, the highest position of the second peak was at 385 °C, and the peak height ratio of the first peak to the second peak was 1:1.12; the proportion of grains with a particle size in the range of 20 - 100 nm in the catalyst product was 65%, and the proportion of elongated grains with the longest distance between any two points in the range of 500 - 1000 nm was 35%. Among the elongated grains, the proportion of cuboid grains was 22%.

[0074] Preparation Example 5

[0075] The method was the same as that of Preparation Example 3, except that the crystallization condition was crystallization at 110 °C for 5 h. As a result, a binderless ZSM-5 molecular sieve was prepared. There were two peaks on the NH 3 -TPD. Among them, the highest position of the first peak was at 187 °C, the highest position of the second peak was at 411 °C, and the peak height ratio of the first peak to the second peak was 1:1.30; the proportion of spherical grains with a particle size in the range of 20 - 100 nm in the catalyst product was 78%, and the proportion of elongated grains with the longest distance between any two points in the range of 500 - 1000 nm was 28%. Among the elongated grains, the proportion of cuboid grains was 21%.

[0076] Preparation Example 6

[0077] The method was the same as that of Preparation Example 1, except that the ratio of the precursor to the organic amine solution was different during the crystallization process: 10 g of the ZSM-5 molecular sieve precursor was placed in 20 g of 60% n-butylamine solution. As a result, a binderless ZSM-5 molecular sieve was prepared. There were two peaks on the NH 3 -TPD. Among them, the highest position of the first peak was at 182 °C, the highest position of the second peak was at 380 °C, and the peak height ratio of the first peak to the second peak was 1:1.15; the proportion of grains with a particle size in the range of 20 - 100 nm in the catalyst product was 68%, and the proportion of elongated grains with the longest distance between any two points in the range of 500 - 1000 nm was 32%. Among the elongated grains, the proportion of cuboid grains was 25%.

[0078] Preparation Example 7

[0079] The method was the same as that in Preparation Example 1, except that the ratio of the precursor to the organic amine solution was different during the crystallization process: 10 g of the ZSM-5 molecular sieve precursor was placed in 15 g of a 55% n-propylamine solution. As a result, a binderless ZSM-5 molecular sieve was prepared, and NH 3 -TPD had two peaks. Among them, the highest position of the first peak was at 188 °C, the highest position of the second peak was at 385 °C, and the peak height ratio of the first peak to the second peak was 1:1.21; the proportion of grains with a particle size in the range of 20-100 nm in the catalyst product was 70%, and the proportion of strip-shaped grains with the longest distance between any two points in the range of 500-1000 nm was 30%. Among the strip-shaped grains, the proportion of cuboid grains was 26%.

[0080] Comparative Example 1

[0081] The slurry in Example 1 was separated from solid and liquid, washed, and dried to obtain a ZSM-5 molecular sieve. The weight loss rate of the ZSM-5 molecular sieve was measured to be 15%. 38.8 g of ZSM-5 molecular sieve seeds, 35.3 g of alkaline silica sol (40% content), 0.5 g of sesbania powder, and 15 g of nitric acid aqueous solution (5% concentration) were mixed evenly, and a binderless ZSM-5 molecular sieve precursor with a molecular sieve content of 70% was synthesized by extrusion molding and dried at 150 °C for 8 h.

[0082] 0.13 g of sodium aluminate and 10 g of ethylamine were mixed evenly and dissolved in 10 g of water. 10 g of the molecular sieve precursor was placed in 20 g of this solution, and the resulting mixture was crystallized at 150 °C for 30 h. After crystallization, it was filtered, washed, and calcined to obtain a binderless ZSM-5 molecular sieve. The SEM photograph of the product is as Figure 4 shown.

[0083] The NH 3 -TPD result of the prepared binderless ZSM-5 molecular sieve was that the highest position of the first peak was at 188 °C, the highest position of the second peak was at 385 °C, the peak height ratio of the first peak to the second peak was 1:0.95, the proportion of grains with a particle size in the range of 20-100 nm in the synthesized catalyst was less than 1%, the proportion of strip-shaped grains with the longest distance between any two points in the range of 500-1000 nm was more than 99%, and the proportion of cuboid grains among the strip-shaped grains was 50%.

[0084] Example

[0085] Examples 1-2 and Comparative Example 1

[0086] The binderless ZSM-5 molecular sieve catalysts prepared in Preparation Examples 1-2 and Comparative Example 1 were used in the continuous fixed-bed gas-phase alkylation reaction of benzene with pure ethylene. The alkylation reaction conditions were: temperature 330 °C, pressure 0.1 MPa, benzene / ethylene feed ratio 8, ethylene mass space velocity 4.0 h -1, the reaction reached a steady state after 4 h, and the results are shown in Table 1 below.

[0087] Example 3

[0088] The binderless ZSM-5 molecular sieve catalyst prepared in Preparation Example 3 was used in the gas-phase alkylation reaction of benzene with pure ethylene in a continuous fixed bed. The alkylation reaction conditions were as follows: temperature 310 °C, pressure 0.3 MPa, benzene / ethylene feed ratio 7, ethylene mass space velocity 8.0 h -1 , the reaction reached a steady state after 4 h, and the results are shown in Table 1 below.

[0089] Example 4

[0090] The binderless ZSM-5 molecular sieve catalyst prepared in Preparation Example 4 was used in the gas-phase alkylation reaction of benzene with pure ethylene in a continuous fixed bed. The alkylation reaction conditions were as follows: temperature 370 °C, pressure 0.2 MPa, benzene / ethylene feed ratio 5, ethylene mass space velocity 4.0 h -1 , the reaction reached a steady state after 4 h, and the results are shown in Table 1 below.

[0091] Example 5

[0092] The binderless ZSM-5 molecular sieve catalyst prepared in Preparation Example 5 was used in the gas-phase alkylation reaction of benzene with pure ethylene in a continuous fixed bed. The alkylation reaction conditions were as follows: temperature 310 °C, pressure 0.1 MPa, benzene / ethylene feed ratio 6, ethylene mass space velocity 6.0 h -1 , the reaction reached a steady state after 4 h, and the results are shown in Table 1 below.

[0093] Example 6

[0094] The binderless ZSM-5 molecular sieve catalyst prepared in Preparation Example 6 was used in the gas-phase alkylation reaction of benzene with pure ethylene in a continuous fixed bed. The alkylation reaction conditions were as follows: temperature 320 °C, pressure 0.7 MPa, benzene / ethylene feed ratio 6, ethylene mass space velocity 7.0 h -1 , the reaction reached a steady state after 4 h, and the results are shown in Table 1 below.

[0095] Example 7

[0096] The binderless ZSM-5 molecular sieve catalyst prepared in Preparation Example 7 was used in the gas-phase alkylation reaction of benzene with pure ethylene in a continuous fixed bed. The alkylation reaction conditions were as follows: temperature 350 °C, pressure 0.1 MPa, benzene / ethylene feed ratio 7, ethylene mass space velocity 7.0 h -1 , the reaction reached a steady state after 4 h, and the results are shown in Table 1 below.

[0097] Table 1

[0098]

[0099] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as stipulated, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. An adhesive-free ZSM-5 molecular sieve catalyst, and the ZSM-5 molecular sieve catalyst has two peaks in NH 3 -TPD, Among them, the highest position of the first peak is at 170 - 210 °C, the highest position of the second peak is at 380 - 420 °C, and the ratio of the peak height of the first peak to that of the second peak is 1:(1.0 - 1.5); the ZSM-5 molecular sieve catalyst comprises elongated grains and spherical-like grains with a particle size of 20 - 100 nm. The longest distance between any two points on the elongated grains is 500 - 1000 nm. Among them, the spherical-like grains account for 60 - 80% of the total weight of the ZSM-5 molecular sieve catalyst, and the elongated grains account for 20 - 40% of the total weight of the ZSM-5 molecular sieve catalyst; the elongated grains comprise cuboid grains. The lengths of the a-axis and b-axis of the cuboid grains are the same or different, independently 50 - 100 nm, the length of the c-axis of the cuboid grains is 500 - 1000 nm, and the cuboid grains account for 20 - 30% of the total weight of the elongated grains.

2. A method for preparing a binderless ZSM-5 molecular sieve catalyst as claimed in claim 1, which comprises the following steps: 1) Knead ZSM-5 seeds, an aluminum source, a binder, and an optional additive and then form them, and dry to obtain a ZSM-5 molecular sieve precursor; 2) Subject the ZSM-5 molecular sieve precursor prepared in step 1) to liquid-phase crystallization under microwave conditions, and perform solid-liquid separation to obtain a crystallized solid product; 3) Wash, dry, exchange, and calcine the obtained crystallized solid product to obtain the ZSM-5 molecular sieve catalyst.

3. According to the preparation method described in claim 2, characterized in that, the liquid-phase crystallization under microwave conditions in step 2) includes mixing the ZSM-5 molecular sieve precursor and an organic amine solution and then performing crystallization under microwave conditions.

4. According to the preparation method described in claim 3, characterized in that, the temperature of the crystallization is 80 - 110 °C, and / or the time of the crystallization is 2 - 12 h, and / or the power of the microwave is 200 - 1000 W.

5. According to the preparation method described in any one of claims 2 - 4, characterized in that, In step 1), the ZSM-5 seed is the ZSM-5 molecular sieve raw powder, and the SiO 2 in the ZSM-5 seed accounts for 0-15% by weight of the total SiO 2 in the ZSM-5 molecular sieve precursor and is not 0; and / or SiO in the binder 2 and Al in the aluminum source 2 O 3 has a molar ratio of 50 - 400.

6. According to the preparation method described in claim 5, characterized in that, In step 1), the SiO in the ZSM-5 seed 2 accounts for 1-15% of the total SiO in the ZSM-5 molecular sieve precursor 2 by weight.

7. According to the preparation method described in any one of claims 2 - 4, characterized in that, in step 1), the aluminum source is an aluminum salt; and / or the binder is at least one of silica powder, white carbon black, and silica sol; and / or the additive includes a pore-forming agent and an aqueous solution of an acid.

8. According to the preparation method described in claim 7, characterized in that, in step 1), the aluminum source is selected from at least one of aluminum sulfate, aluminum nitrate, and aluminum acetate and their hydrates; and / or the aqueous solution of the acid is an aqueous solution of nitric acid; and / or the pore-forming agent is selected from at least one of methyl cellulose and sesbania powder.

9. According to the preparation method described in claim 8, characterized in that, in step 1), the weight content of the aqueous solution of nitric acid is 1% - 10%, and / or the dosage of the aqueous solution of nitric acid is 10% - 40% of the total weight of the raw materials added in step 1); and / or the dosage of the pore-forming agent is 0.2% - 1% of the total weight of the raw materials added in step 1).

10. The preparation method according to any one of claims 2-4, characterized in that, in step 1), the shaping is extrusion shaping.

11. The preparation method according to any one of claims 3 or 4, characterized in that, in step 2), the weight ratio of the organic amine solution to the ZSM-5 molecular sieve precursor is (0.8-3):

1.

12. The preparation method according to any one of claims 2-4, characterized in that, in step 2), the organic amine is selected from at least one of ethylamine, n-propylamine and n-butylamine.

13. The preparation method according to claim 12, characterized in that, in step 2), the organic amine solution is an aqueous solution of the organic amine, and the concentration of the organic amine solution is 40-70% wt.

14. The preparation method according to any one of claims 2-4, characterized in that, in step 3), the exchange is acid exchange; and / or the temperature of the calcination is 450-600 °C, and the time of the calcination is 2-12 h.

15. The preparation method according to claim 14, characterized in that, The acid is at least one of HCl, HNO 3 and H 2 SO 4 ; and / or the concentration of the acid is 0.1 mol / L-1 mol / L; and / or the temperature of the acid exchange is 0-50 °C; and / or the number of times of the acid exchange is 1-3 times; and / or the weight ratio of the acid to the solid product in the acid exchange is 3:1-20:

1.

16. Use of the binderless ZSM-5 molecular sieve catalyst according to claim 1 or the binderless ZSM-5 molecular sieve catalyst prepared by the preparation method according to any one of claims 2-15 in the alkylation reaction of benzene with ethylene or benzene with ethanol to produce ethylbenzene.

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