A ZSM-5 molecular sieve and its preparation method and application

Abstract

The present invention discloses a ZSM-5 molecular sieve, a preparation method thereof, and an application thereof. In the crystal grains of the ZSM-5 molecular sieve, the b-axis thickness is 80 to 700 nm, the a-axis length is 2 to 10 times the b-axis thickness, and the c-axis length is 4 to 40 times the b-axis thickness; the SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve is 150 to 175. The preparation method of the ZSM-5 molecular sieve includes: a step of crystallizing a mixture of a silicon source, an aluminum source, a template, ethanol, a structural aid, and water; the structural aid is selected from at least one of urea, glucose, hexadecyltrimethylammonium bromide, or polydiallyldimethylammonium chloride. The ZSM-5 molecular sieve of the present invention is used in the alkylation reaction of benzene and methanol, and has the characteristics of high single-pass conversion and good selectivity of the target product.

Description

Technical Field

[0001] The invention belongs to the field of catalytic materials, and particularly relates to a ZSM-5 molecular sieve and a preparation method thereof, as well as application of the ZSM-5 molecular sieve in the alkylation of benzene and methanol to prepare toluene and xylene. Background Art

[0002] Molecular sieve materials are crystalline, microporous silicates. Due to their complex pore structure, adjustable acidity, high thermal stability, and high hydrothermal stability, they are widely used in catalysis, adsorption, separation, and ion exchange. However, the single pore structure and small pore size of molecular sieves increase the diffusion resistance of large molecules within the pores, which in turn limits their application in catalytic reactions involving large molecules. In recent years, many studies have shown that introducing mesopores or macropores into silica-alumina molecular sieves to construct multi-level pore molecular sieves can improve the catalytic performance of molecular sieve catalysts. Current methods for synthesizing multi-level pore molecular sieves include soft template method, hard template method, epitaxial growth method, and nanoassembly method. However, problems such as complex synthesis process, high raw material cost, and high energy consumption have seriously hindered their industrialization process.

[0003] CN 104226357A discloses a catalyst for the alkylation of benzene and methanol, as well as its preparation and application. The catalyst is prepared by adding an ethanolic solution of an organic template to an ethanolic solution of an aluminum source, a silicon source, and silane to produce a xerogel. The xerogel is then added to water and tetrapropylammonium hydroxide and placed in an autoclave for crystallization to obtain a multi-level pore ZSM-5 molecular sieve. The multi-level pore ZSM-5 molecular sieve is then kneaded and formed into a carrier. The carrier is then impregnated with a magnesium acetate solution, dried, and calcined to obtain a catalyst for the alkylation of benzyl alcohol. The catalyst for the alkylation of benzene to toluene disclosed in CN 107413375A uses TNU-9, MSM-22, BETA, or HZSM-5 molecular sieves as precursors, which are modified with acid and nitrate.

[0004] Although the benzene and methanol alkylation catalyst prepared by the above ZSM-5 molecular sieve can improve the activity and selectivity of the catalyst to a certain extent, it still needs to be further improved. Summary of the Invention

[0005] The key technical problem to be solved by the present invention is that the existing ZSM-5 molecular sieve catalysts suffer from low per-pass conversion and poor selectivity for the target product during the alkylation reaction of benzene and methanol. The present invention provides a ZSM-5 molecular sieve, its preparation method, and application. The ZSM-5 molecular sieve, when used in the alkylation reaction of benzene and methanol, exhibits high per-pass conversion and good selectivity for the target product.

[0006] The first aspect of the present invention provides a ZSM-5 molecular sieve, wherein the b-axis thickness of the ZSM-5 molecular sieve grains is 80 to 700 nm, the a-axis length is 2 to 10 times the b-axis thickness, and the c-axis length is 4 to 40 times the b-axis thickness; the SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve is 150 to 175.

[0007] In the above technical solution, preferably, in the ZSM-5 molecular sieve grains, the b-axis thickness is 90 to 200 nm.

[0008] In the above technical solution, preferably, in the ZSM-5 molecular sieve grains, the length of the a-axis is 3 to 7 times the thickness of the b-axis.

[0009] In the above technical solution, preferably, in the ZSM-5 molecular sieve grains, the c-axis length is 8 to 20 times the b-axis thickness.

[0010] In the above technical solution, preferably, in the ZSM-5 molecular sieve grains, the length of the a-axis is 200 to 1200 nm.

[0011] In the above technical solution, preferably, in the ZSM-5 molecular sieve grains, the length of the c-axis is 1000 to 4000 nm.

[0012] In the above technical solution, the relative crystallinity of the ZSM-5 molecular sieve is 80% to 100%.

[0013] In the above technical solution, the morphology of the ZSM-5 molecular sieve is a coffin board morphology.

[0014] The second aspect of the present invention provides a method for preparing the above-mentioned ZSM-5 molecular sieve, comprising: a step of crystallizing a mixture of a silicon source, an aluminum source, a template, ethanol, a structural additive and water; the structural additive is selected from at least one of urea, glucose, cetyltrimethylammonium bromide (CTAB) or polydiallyldimethylammonium chloride (PDDA).

[0015] In the above technical solution, the silicon source is selected from at least one of tetraethyl orthosilicate, sodium silicate, fumed silica, or silica sol. The aluminum source is selected from at least one of pseudo-boehmite, sodium metaaluminate, aluminum sulfate, or aluminum isopropoxide.

[0016] In the above technical solution, the template R is selected from at least one of tetrabutylammonium bromide, tetrapropylammonium bromide, tetrapropylammonium hydroxide or n-butylamine.

[0017] In the above technical solution, the structural auxiliary agent is selected from at least one of urea, glucose, hexadecyltrimethylammonium bromide (CTAB) or polydiallyldimethylammonium chloride (PDDA). Among them, the viscosity of PDDA is 100-200cP (25°C). In the above technical solution, preferably, the structural auxiliary agent is polydiallyldimethylammonium chloride (PDDA), or urea and hexadecyltrimethylammonium bromide (CTAB), or urea and polydiallyldimethylammonium chloride (PDDA). Further preferably, the mass ratio of urea to hexadecyltrimethylammonium bromide (CTAB) is 0.001-0.50. The mass ratio of urea to polydiallyldimethylammonium chloride (PDDA) is 0-0.05, preferably 0.0001-0.04.

[0018] In the above technical solution, the molar ratio of silicon source calculated as SiO2, template R, ethanol EtOH, aluminum source calculated as Al2O3 and water is as follows: SiO2: (0.20~1.0) R: (2.0~8.0) EtOH: (0.002~0.005) Al2O3: (120~300) H2O.

[0019] In the above technical solution, the added amount of the structural additive is 80% to 700% of the mass of the silicon source in terms of SiO2.

[0020] In the above technical solution, the conditions of the crystallization reaction are as follows: the crystallization temperature is 120 to 220° C., and the crystallization time is 6 to 120 hours.

[0021] In the above technical solution, after the crystallization step is completed, the ZSM-5 molecular sieve product can be separated from the obtained mixture by any conventionally known separation method.

[0022] In the above technical solution, the crystallized material can be subjected to one or more of the steps of separation, washing, drying, and calcination as needed. The drying conditions are as follows: a drying temperature of 50 to 250°C, preferably 60 to 150°C; a drying time of 4 to 24 hours, preferably 5 to 15 hours; the calcination conditions are as follows: a calcination temperature of 300 to 700°C, and a calcination time of 4 to 24 hours. In the above technical solution, the calcination is generally carried out in an oxygen-containing atmosphere, such as air or oxygen.

[0023] A third aspect of the present invention provides a use of the above-mentioned ZSM-5 molecular sieve in the alkylation reaction of benzene and methanol.

[0024] In the above technical solution, the alkylation reaction conditions of benzene and methanol are as follows: reaction temperature is 350-600°C, reaction pressure is 0-2 MPa, and mass space velocity (WHSV) of benzene and methanol is 0.1-20h -1, the weight ratio of benzene to methanol is 1 to 20, and the reaction carrier gas is at least one of nitrogen, hydrogen or argon.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The ZSM-5 molecular sieve with a specific b-axis size of the present invention, especially the ZSM-5 molecular sieve with a specific silicon-aluminum ratio, is used in the alkylation reaction of benzene and methanol, and has the characteristics of good product diffusivity, high single-pass conversion rate of benzene and good selectivity for the target products toluene and xylene.

[0027] 2. The inventors of the present invention have discovered through extensive research that, by adding a structural additive during the preparation of a ZSM-5 molecular sieve crystallization solution and combining it with other raw materials, a ZSM-5 molecular sieve with good crystallinity and a suitable b-axis size can be prepared. When used in the alkylation reaction of benzene and methanol, the obtained ZSM-5 molecular sieve has the characteristics of good product diffusivity, high single-pass conversion of benzene, and good selectivity for the target products, toluene and xylene. In particular, when the ZSM-5 molecular sieve prepared with the preferred structural additive is used as a catalyst for the alkylation of benzene and methanol, the obtained ZSM-5 molecular sieve has a more outstanding single-pass conversion of benzene and selectivity for the target products, toluene and xylene. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The XRD spectra of the ZSM-5 molecular sieves prepared in Comparative Examples 1-4 of Examples 3, 5, 6, and 7 of the present invention are shown;

[0029] Figure 2 This is a scanning electron microscope photograph of the ZSM-5 molecular sieve prepared in Example 3 of the present invention;

[0030] Figure 3 This is a scanning electron microscope photograph of the ZSM-5 molecular sieve prepared in Example 5 of the present invention;

[0031] Figure 4 This is a scanning electron microscope photograph of the ZSM-5 molecular sieve prepared in Example 6 of the present invention;

[0032] Figure 5 This is a scanning electron microscope photograph of the ZSM-5 molecular sieve prepared in Comparative Example 1 of the present invention;

[0033] Figure 6 This is a scanning electron microscope photograph of the ZSM-5 molecular sieve prepared in Comparative Example 2 of the present invention;

[0034] Figure 7 This is a scanning electron microscope photograph of the ZSM-5 molecular sieve prepared in Comparative Example 3 of the present invention;

[0035] Figure 8 This is a scanning electron microscope photograph of the ZSM-5 molecular sieve prepared in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the examples, but the present invention is not limited to the examples.

[0037] In the present invention, the crystal structure of the samples was analyzed using a Bruker D8 Advance X-ray diffractometer (XRD) with a Cu Kα target, λ = 0.1542 nm, a tube voltage of 40 kV, and a tube current of 50 mA. The peak area of ​​the molecular sieve obtained in Comparative Example 1 at 2θ = 9.3° was taken as 100%, and the relative crystallinity of the post-treated samples was calculated by dividing the peak area of ​​the other samples by the peak area at 2θ = 9.3°.

[0038] In the present invention, the crystal morphology was observed by a Zeiss Merlin scanning electron microscope (SEM) and a Tecnai 20STWIN TEM. The accelerating voltage of the SEM was 2 kV. The sample was evenly dispersed on a sample stage with conductive glue for testing. The accelerating voltage of the TEM was 200 kV.

[0039] In the present invention, the SiO2 / Al2O3 molar ratio is obtained by X-ray fluorescence spectroscopy (XRF) analysis using a Termo / ARLQUANT' X-ray fluorescence spectrometer, with a Kα spectral line, Li F1 crystal, and Rh target.

[0040] Example 1

[0041] Weigh 9.5g of anhydrous ethanol, 145.12g of deionized water, 10.7g of tetraethyl orthosilicate, 4.3g of tetrapropylammonium hydroxide, 0.05g of aluminum isopropoxide, and 7.9g of urea and stir until uniform. Then, transfer the raw materials to a 100mL Teflon-lined stainless steel autoclave and place it in an oven for crystallization at 180°C for 48 hours. The resulting product is washed, filtered, dried at 100°C for 12 hours, and calcined at 550°C for 6 hours to obtain the final product with a SiO2 / Al2O3 molar ratio of 160.

[0042] The XRD pattern of the above product shows that it has a typical ZSM-5 molecular sieve structure with a relative crystallinity of 90%. The scanning electron microscope image of the above product shows that the a-axis length is 520nm, the c-axis length is 1200nm, and the b-axis thickness is 260nm.

[0043] The above product powder was tableted and sieved to obtain 20-40 mesh catalyst particles Cat1. A fixed bed reactor was used to load 3 g of the formed catalyst Cat1. At room temperature, benzene and methanol were mixed in a molar ratio of 1:1, gasified, and evenly dispersed. The mixture was then introduced into the reactor and heated at a reaction temperature of 500°C, a pressure of 0.05 MPa, and a mass space velocity of benzene and methanol of 2.0 h / min. -1The reaction was carried out under the conditions of , and a gaseous product stream was obtained after the reaction. After cooling, it was passed into a gas-liquid separator for separation, and the liquid product was sampled and analyzed. The details are shown in Table 1.

[0044] Example 2

[0045] Weigh 9.5g of anhydrous ethanol, 145.12g of deionized water, 10.7g of tetraethyl orthosilicate, 4.3g of tetrapropylammonium hydroxide, 0.05g of aluminum isopropoxide, and 3.95g of urea and stir until uniform. Then, transfer the raw materials to a 100mL polytetrafluoroethylene-lined stainless steel autoclave and place it in an oven for crystallization at 180°C for 48 hours. The resulting product is washed, filtered, dried at 100°C for 12 hours, and calcined at 550°C for 6 hours to obtain the final product with a SiO2 / Al2O3 molar ratio of 160.

[0046] The XRD pattern of the above product shows that it has a typical ZSM-5 molecular sieve structure with a relative crystallinity of 93%. The scanning electron microscope image of the above product shows that the a-axis length is 600nm, the c-axis length is 2600nm, and the b-axis thickness is 110nm.

[0047] The above product powder was pressed into tablets and sieved to obtain 20-40 mesh catalyst particles Cat2. A fixed bed reactor was used to load 3 g of the formed catalyst Cat2. At room temperature, benzene and methanol were mixed in a molar ratio of 1:1, gasified, and evenly dispersed. The mixture was then introduced into the reactor and heated at a reaction temperature of 500°C, a pressure of 0.05 MPa, and a mass space velocity of benzene and methanol of 2.0 h / min. -1 The reaction was carried out under the conditions of , and a gaseous product stream was obtained after the reaction. After cooling, it was passed into a gas-liquid separator for separation, and the liquid product was sampled and analyzed. The details are shown in Table 1.

[0048] Example 3

[0049] Weigh 9.5 g of anhydrous ethanol, 145.12 g of deionized water, 10.7 g of tetraethyl orthosilicate, 4.3 g of tetrapropylammonium hydroxide, 0.05 g of aluminum isopropoxide, 0.6 g of urea, and 20 g of PDDA (viscosity of 150 cP (25°C)) and stir well. Then transfer the raw materials to a 100 ml polytetrafluoroethylene-lined stainless steel autoclave and place it in an oven for crystallization at 180°C for 36 h. The resulting product is washed and filtered, then dried at 100°C and calcined at 550°C for 6 h to obtain the final product with a SiO2 / Al2O3 molar ratio of 160.

[0050] Figure 1 This is the XRD characterization result of the above product. It can be seen that the product has a typical ZSM-5 molecular sieve structure and a relative crystallinity of 86%. Figure 2This is the SEM image of the product. It can be seen from the figure that the a-axis length is 300nm, the c-axis length is 1300nm, and the b-axis thickness is 90nm.

[0051] The above product powder was pressed into tablets and sieved to obtain 20-40 mesh catalyst particles Cat3. A fixed bed reactor was used to load 3 g of the formed catalyst Cat3. At room temperature, benzene and methanol were mixed in a molar ratio of 1:1, gasified, and evenly dispersed. The mixture was then introduced into the reactor and heated at a reaction temperature of 500°C, a pressure of 0.05 MPa, and a mass space velocity of benzene and methanol of 2.0 h / min. -1 The reaction was carried out under the conditions of , and a gaseous product stream was obtained after the reaction. After cooling, it was passed into a gas-liquid separator for separation, and the liquid product was sampled and analyzed. The details are shown in Table 1.

[0052] Example 4

[0053] Weigh 9.5g of anhydrous ethanol, 145.12g of deionized water, 10.7g of tetraethyl orthosilicate, 4.3g of tetrapropylammonium hydroxide, 0.05g of aluminum isopropoxide, and 11.8g of glucose into a 100ml Teflon-lined stainless steel autoclave. Place the mixture in an oven and crystallize at 150°C for 72h. The resulting product is washed, filtered, dried at 100°C, and calcined at 550°C for 6h to obtain the final product with a SiO2 / Al2O3 molar ratio of 160.

[0054] The XRD results of the above product show that it has a typical ZSM-5 molecular sieve structure with a relative crystallinity of 92%. The scanning electron microscope images of the above product show that the a-axis length is 800nm, the c-axis length is 3000nm, and the b-axis thickness is 290nm.

[0055] The above product powder was pressed into tablets and sieved to obtain 20-40 mesh catalyst particles Cat4. A fixed bed reactor was used to load 3 g of the formed catalyst Cat4. At room temperature, benzene and methanol were mixed in a molar ratio of 1:1, gasified, and evenly dispersed. The mixture was then introduced into the reactor and heated at a reaction temperature of 500°C, a pressure of 0.05 MPa, and a mass space velocity of benzene and methanol of 2.0 h / min. -1 The reaction was carried out under the conditions of , and a gaseous product stream was obtained after the reaction. After cooling, it was passed into a gas-liquid separator for separation, and the liquid product was sampled and analyzed. The details are shown in Table 1.

[0056] Example 5

[0057] Weigh 9.5g of anhydrous ethanol, 145.12g of deionized water, 10.7g of tetraethyl orthosilicate, 4.3g of tetrapropylammonium hydroxide, 0.05g of aluminum isopropoxide, 0.3g of urea, and 3.65g of CTAB and stir until uniform. Then, transfer the raw materials to a 100ml Teflon-lined stainless steel autoclave and place it in an oven for crystallization at 175°C for 72 hours. The resulting product is washed, filtered, dried at 100°C, and calcined at 550°C for 6 hours to obtain the final product with a SiO2 / Al2O3 molar ratio of 160.

[0058] From the XRD spectrum (see Figure 1 ) It can be seen that the product has a typical ZSM-5 molecular sieve structure with a relative crystallinity of 96%. Figure 3 From the SEM photograph, we can see that the a-axis length is 400nm, the c-axis length is 1300nm, and the b-axis thickness is 120nm.

[0059] The above product powder was pressed into tablets and sieved to obtain 20-40 mesh catalyst particles Cat5. A fixed bed reactor was used to load 3 g of the formed catalyst Cat5. At room temperature, benzene and methanol were mixed in a molar ratio of 1:1, gasified, and evenly dispersed. The mixture was then introduced into the reactor and heated at a reaction temperature of 500°C, a pressure of 0.05 MPa, and a mass space velocity of benzene and methanol of 2.0 h / min. -1 The reaction was carried out under the conditions of , and a gaseous product stream was obtained after the reaction. After cooling, it was passed into a gas-liquid separator for separation, and the liquid product was sampled and analyzed. The details are shown in Table 1.

[0060] Example 6

[0061] Weigh 9.5 g of anhydrous ethanol, 145.12 g of deionized water, 10.7 g of tetraethyl orthosilicate, 4.3 g of tetrapropylammonium hydroxide, 0.05 g of aluminum isopropoxide, and 13.6 g of PDDA (viscosity 150 cP at 25°C) and stir until uniform. Then, transfer the raw materials to a 100 ml polytetrafluoroethylene-lined stainless steel autoclave and place it in an oven for crystallization at 180°C for 48 h. The resulting product is washed, filtered, dried at 100°C, and calcined at 550°C for 6 h to obtain the final product with a SiO2 / Al2O3 molar ratio of 160.

[0062] From the XRD spectrum (see Figure 1 ) It can be seen that the product has a typical ZSM-5 molecular sieve structure with a relative crystallinity of 90%. From the SEM photo ( Figure 4 )The a-axis length is 300nm, the c-axis length is 1000nm, and the b-axis thickness is 90nm.

[0063] The above product powder was tableted and sieved to obtain 20-40 mesh catalyst particles Cat6. A fixed bed reactor was used to load 3 g of the formed catalyst Cat6. At room temperature, benzene and methanol were mixed in a molar ratio of 1:1, gasified, and evenly dispersed. The mixture was then introduced into the reactor and heated at a reaction temperature of 500°C, a pressure of 0.05 MPa, and a mass space velocity of benzene and methanol of 2.0 h / min. -1 The reaction was carried out under the conditions of , and a gaseous product stream was obtained after the reaction. After cooling, it was passed into a gas-liquid separator for separation, and the liquid product was sampled and analyzed. The details are shown in Table 1.

[0064] Example 7

[0065] Weigh 9.5 g of anhydrous ethanol, 145.12 g of deionized water, 10.7 g of tetraethyl orthosilicate, 4.3 g of tetrapropylammonium hydroxide, 0.05 g of aluminum isopropoxide, and 20 g of PDDA (viscosity of 150 cP (25°C)) and stir well. Then transfer the raw materials to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and place it in an oven for crystallization at 180°C for 48 h. The obtained product was washed and filtered, dried at 100°C for 12 h, and calcined at 550°C for 6 h to obtain the final product with a SiO2 / Al2O3 molar ratio of 160.

[0066] From the XRD spectrum (see Figure 1 ) It can be seen that the product has a typical ZSM-5 molecular sieve structure with a relative crystallinity of 90%. From the SEM image, it can be seen that the a-axis length is 400nm, the c-axis length is 1100nm, and the b-axis thickness is 100nm.

[0067] The above product powder was pressed into tablets and sieved to obtain 20-40 mesh catalyst particles Cat7. A fixed bed reactor was used to load 3 g of the formed catalyst Cat7. At room temperature, benzene and methanol were mixed in a molar ratio of 1:1, gasified, and evenly dispersed. The mixture was then introduced into the reactor and heated at a reaction temperature of 500°C, a pressure of 0.05 MPa, and a mass space velocity of benzene and methanol of 2.0 h / min. -1 The reaction was carried out under the conditions of , and a gaseous product stream was obtained after the reaction. After cooling, it was passed into a gas-liquid separator for separation, and the liquid product was sampled and analyzed. The details are shown in Table 1.

[0068] Example 8

[0069] Weigh 11.88 g of anhydrous ethanol, 120 g of deionized water, 10.7 g of tetraethyl orthosilicate, 8.05 g of tetrapropylammonium hydroxide, 0.07 g of aluminum isopropoxide, and 20 g of PDDA (viscosity of 150 cP (25°C)) and stir well. Then transfer the raw materials to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and place it in an oven for crystallization at 150°C for 72 h. The obtained product was washed and filtered, dried at 100°C for 12 h, and calcined at 550°C for 6 h to obtain the final product with a SiO2 / Al2O3 molar ratio of 150.

[0070] The XRD spectrum shows that the product has a typical ZSM-5 molecular sieve structure with a relative crystallinity of 90%. The SEM image shows that the a-axis length is 350nm, the c-axis length is 1200nm, and the b-axis thickness is 100nm.

[0071] The above product powder was pressed into tablets and sieved to obtain 20-40 mesh catalyst particles Cat8. A fixed bed reactor was used to load 3 g of the formed catalyst Cat8. At room temperature, benzene and methanol were mixed in a molar ratio of 1:1, gasified, and evenly dispersed. The mixture was then introduced into the reactor and heated at a reaction temperature of 500°C, a pressure of 0.05 MPa, and a mass space velocity of benzene and methanol of 2.0 h / min. -1 The reaction was carried out under the conditions of , and a gaseous product stream was obtained after the reaction. After cooling, it was passed into a gas-liquid separator for separation, and the liquid product was sampled and analyzed. The details are shown in Table 1.

[0072] Example 9

[0073] Weigh 16.5 g of anhydrous ethanol, 120 g of deionized water, 10.7 g of tetraethyl orthosilicate, 9.2 g of tetrapropylammonium hydroxide, 0.06 g of aluminum isopropoxide, and 20 g of PDDA (viscosity of 150 cP (25°C)) and stir well. Then transfer the raw materials to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and place it in an oven for crystallization at 170°C for 52 h. The obtained product was washed and filtered, dried at 100°C for 12 h, and calcined at 550°C for 6 h to obtain the final product with a SiO2 / Al2O3 molar ratio of 165.

[0074] The XRD spectrum shows that the product has a typical ZSM-5 molecular sieve structure with a relative crystallinity of 90%. The SEM image shows that the a-axis length is 430nm, the c-axis length is 1400nm, and the b-axis thickness is 100nm.

[0075] The above product powder was tableted and sieved to obtain 20-40 mesh catalyst particles Cat9. A fixed bed reactor was used to load 3 g of the formed catalyst Cat9. At room temperature, benzene and methanol were mixed in a molar ratio of 1:1, gasified, and evenly dispersed. The mixture was then introduced into the reactor and heated at a reaction temperature of 500°C, a pressure of 0.05 MPa, and a mass space velocity of benzene and methanol of 2.0 h / min. -1 The reaction was carried out under the conditions of , and a gaseous product stream was obtained after the reaction. After cooling, it was passed into a gas-liquid separator for separation, and the liquid product was sampled and analyzed. The details are shown in Table 1.

[0076] Comparative Example 1

[0077] Weigh 9.5g of anhydrous ethanol, 145.12g of deionized water, 10.7g of tetraethyl orthosilicate, 4.3g of tetrapropylammonium hydroxide, and 0.05g of aluminum isopropoxide and mix thoroughly. Then, transfer the raw materials to a 100mL polytetrafluoroethylene-lined stainless steel autoclave and place it in an oven for crystallization at 180°C for 48 hours. The resulting product is washed, filtered, dried at 100°C for 12 hours, and calcined at 550°C for 6 hours to obtain the final product.

[0078] From the XRD spectrum (see Figure 1 ) It can be seen that the product is a typical ZSM-5 molecular sieve structure with a relative crystallinity of 100%. Figure 5 ) It can be seen that the a-axis length is 600nm, the c-axis length is 600nm, and the b-axis thickness is 300nm.

[0079] The above product powder was tableted and sieved to obtain 20-40 mesh catalyst particles DCat1. A fixed bed reactor was used to load 3 g of the formed catalyst DCat1. At room temperature, benzene and methanol were mixed in a molar ratio of 1:1, gasified, and evenly dispersed. The mixture was then introduced into the reactor and heated at a reaction temperature of 500°C, a pressure of 0.05 MPa, and a mass space velocity of 2.0 h -1 The reaction was carried out under the conditions of , and a gaseous product stream was obtained after the reaction. After cooling, it was passed into a gas-liquid separator for separation, and the liquid product was sampled and analyzed. The details are shown in Table 1.

[0080] Comparative Example 2

[0081] Weigh 145.12g of deionized water, 10.7g of tetraethyl orthosilicate, 4.3g of tetrapropylammonium hydroxide, and 0.05g of aluminum isopropoxide and mix thoroughly. Then, transfer the raw materials to a 100mL Teflon-lined stainless steel autoclave and place it in an oven for crystallization at 180°C for 48 hours. The resulting product is washed, filtered, dried at 100°C for 12 hours, and calcined at 550°C for 6 hours to obtain the final product.

[0082] From the XRD spectrum (see Figure 1) It can be seen that the product is a typical ZSM-5 molecular sieve structure with a relative crystallinity of 90%. Figure 6 ) It can be seen that the a-axis length is 900nm, the c-axis length is 2400nm, and the b-axis thickness is 600nm.

[0083] The above product powder was pressed into tablets and sieved to obtain 20-40 mesh catalyst particles DCat2. A fixed bed reactor was used to load 3 g of the formed catalyst DCat2. At room temperature, benzene and methanol were mixed in a molar ratio of 1:1, gasified, and evenly dispersed. The mixture was then introduced into the reactor and heated at a reaction temperature of 500°C, a pressure of 0.05 MPa, and a mass space velocity of benzene and methanol of 2.0 h / min. -1 The reaction was carried out under the conditions of , and a gaseous product stream was obtained after the reaction. After cooling, it was passed into a gas-liquid separator for separation, and the liquid product was sampled and analyzed. The details are shown in Table 1.

[0084] Comparative Example 3

[0085] Weigh 9.5g of anhydrous ethanol, 145.12g of deionized water, 10.7g of tetraethyl orthosilicate, 4.3g of tetrapropylammonium hydroxide, 0.05g of aluminum isopropoxide, and 20g of starch and mix thoroughly. Then, transfer the raw materials to a 100mL Teflon-lined stainless steel autoclave and place it in an oven for crystallization at 180°C for 48 hours. The resulting product is washed, filtered, dried at 100°C for 12 hours, and calcined at 550°C for 6 hours to obtain the final product.

[0086] From the XRD spectrum (see Figure 1 ) It can be seen that the product is a typical ZSM-5 molecular sieve structure with a relative crystallinity of 90%. Figure 7 ) It can be seen that the a-axis length is 1000nm, the c-axis length is 3800nm, and the b-axis thickness is 600nm.

[0087] The above product powder was pressed into tablets and sieved to obtain 20-40 mesh catalyst particles DCat3. A fixed-bed reactor was loaded with 3 g of the formed catalyst DCat3. At room temperature, benzene and methanol were mixed in a molar ratio of 1:1, gasified, and evenly dispersed. The mixture was then introduced into the reactor and heated at a reaction temperature of 500°C, a pressure of 0.05 MPa, and a mass space velocity of benzene and methanol of 2.0 h / min. -1 The reaction was carried out under the conditions of , and a gaseous product stream was obtained after the reaction. After cooling, it was passed into a gas-liquid separator for separation, and the liquid product was sampled and analyzed. The details are shown in Table 1.

[0088] Comparative Example 4

[0089] Weigh 9.5 g of anhydrous ethanol, 145.12 g of deionized water, 10.7 g of tetraethyl orthosilicate, 4.3 g of tetrapropylammonium hydroxide, 0.15 g of aluminum isopropoxide, and 20 g of PDDA (viscosity 150 cP (25°C)) and stir well. Then transfer the raw materials to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and place it in an oven for crystallization at 180°C for 48 h. The obtained product is washed and filtered, dried at 100°C for 12 h, and calcined at 550°C for 6 h to obtain the final product with a SiO2 / Al2O3 molar ratio of 68.

[0090] From the XRD spectrum (see Figure 1 ) It can be seen that the product is a typical ZSM-5 molecular sieve structure with a relative crystallinity of 90%. Figure 8 ) It can be seen that the a-axis length is 300nm, the c-axis length is 1000nm, and the b-axis thickness is 120nm.

[0091] The above product powder was tableted and sieved to obtain 20-40 mesh catalyst particles DCat4. A fixed bed reactor was used to load 3 g of the formed catalyst DCat4. At room temperature, benzene and methanol were mixed in a molar ratio of 1:1, gasified, and evenly dispersed. The mixture was then introduced into the reactor and heated at a reaction temperature of 500°C, a pressure of 0.05 MPa, and a mass space velocity of benzene and methanol of 2.0 h / min. -1 The reaction was carried out under the conditions of , and a gaseous product stream was obtained after the reaction. After cooling, it was passed into a gas-liquid separator for separation, and the liquid product was sampled and analyzed. The details are shown in Table 1.

[0092] Table 1

[0093] sample Benzene conversion rate, % Toluene and xylene selectivity, % Example 1 Cat1 62.2 83.7 Example 2 Cat2 61.6 87.5 Example 3 Cat3 64.4 91.2 Example 4 Cat4 58.2 87.9 Example 5 Cat5 62.7 89.9 Example 6 Cat6 67.2 91.8 Example 7 Cat7 65.2 90.8 Example 8 Cat8 63.8 89.6 Example 9 Cat9 64.2 89.8 Comparative Example 1 DCat1 61.7 77.8 Comparative Example 2 DCat2 55.2 72.1 Comparative Example 3 DCat3 53.2 76.5 Comparative Example 4 DCat4 50.6 70.3

[0094] The above describes in detail the specific embodiments of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as the contents disclosed by the present invention and fall within the scope of protection of the present invention.

Claims

1. Application of a ZSM-5 molecular sieve in the alkylation reaction of benzene and methanol, characterized in that: The b-axis thickness of the ZSM-5 molecular sieve grains is 80-120 nm; the a-axis length is 3-7 times the b-axis thickness, and the c-axis length is 8-20 times the b-axis thickness; the SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve is 150-175.

2. The use according to claim 1, characterized in that The b-axis thickness of the ZSM-5 molecular sieve grains is 90-120 nm.

3. The use according to claim 1, characterized in that In the ZSM-5 molecular sieve crystals, the length of the a-axis is 300-1200 nm; and / or the length of the c-axis is 1000-4000 nm.

4. The use according to any one of claims 1 to 3, characterized in that: The preparation method of the ZSM-5 molecular sieve comprises the steps of crystallizing a mixture of a silicon source, an aluminum source, a template agent R, ethanol, a structural auxiliary agent and water; the structural auxiliary agent is selected from at least one of urea, glucose, hexadecyltrimethylammonium bromide and polydiallyldimethylammonium chloride.

5. The use according to claim 4, characterized in that The silicon source is selected from at least one of tetraethyl orthosilicate, sodium silicate, fumed silica or silica sol; the aluminum source is selected from at least one of pseudo-boehmite, sodium metaaluminate, aluminum sulfate or aluminum isopropoxide; and the template R is selected from at least one of tetrabutylammonium bromide, tetrapropylammonium bromide, tetrapropylammonium hydroxide or n-butylamine.

6. The use according to claim 4, characterized in that The structural auxiliary agent is polydiallyldimethylammonium chloride, or urea and cetyltrimethylammonium bromide, or urea and polydiallyldimethylammonium chloride.

7. The use according to claim 4, characterized in that In the preparation method, the molar ratio of the silicon source (calculated as SiO2), the template R, ethanol EtOH, the aluminum source (calculated as Al2O3) and water is as follows: SiO2: (0.20-1.0) R: (2.0-8.0) EtOH: (0.002-0.005) Al2O3: (120-300) H2O; and / or, the amount of the structural additive added is 80%-700% of the mass of the silicon source (calculated as SiO2).

8. The use according to claim 4, characterized in that The conditions of the crystallization reaction are as follows: the crystallization temperature is 120-220° C., and the crystallization time is 6-120 hours.

9. The use according to claim 1, characterized in that The alkylation reaction conditions of benzene and methanol are as follows: reaction temperature is 350-600°C, reaction pressure is 0-2 MPa, mass space velocity of benzene and methanol is 0.1-20 h -1 , the weight ratio of benzene to methanol is 1~20, and the reaction carrier gas is at least one of nitrogen, hydrogen or argon.

Images