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

Abstract

The present invention provides a ZSM-5 molecular sieve catalyst, a preparation method thereof and an application. The preparation method includes: mixing nano-ZSM-5 molecular sieve with a binder, a pore-forming agent, a peptizing agent and an extrusion aid, followed by extrusion molding, and then successively performing first calcination, crystallization, drying, second calcination and third calcination to obtain the ZSM-5 molecular sieve catalyst; the first binder in the binder is one or more of coarse pore silica gel, microsilica, silica sol, diatomaceous earth and kaolin, and the second binder is one or more of nano-alumina, pseudo-boehmite and boehmite. The present invention does not need to use alumina or aluminum sol. By using two specific binders for recrystallization and the simultaneous pore-expanding effect of two specific pore-forming agents, the number of molecular sieve structures with catalytic activity in the catalyst increases. The formed catalyst has a large pore specific surface area and pore volume, high purity of ZSM-5 molecular sieve, high catalytic activity, and stable strength and low crushing rate.

Description

Technical Field

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

[0002] ZSM-5 molecular sieve is a typical microporous molecular sieve, which is widely used in the catalytic field and the adsorption separation field due to its uniform and ordered micropores, large specific surface area, and high hydrothermal stability. Its framework contains two mutually intersecting pore systems: elliptical ten-membered ring straight pores and circular zigzag bent pores, and their pore diameters are approximately 0.51×0.55 nm and 0.53×0.56 nm, respectively. The unique three-dimensional cross-pore structure of ZSM-5 molecular sieve not only provides a spatial confinement effect for shape-selective catalysis, but also provides rich access channels for reactants and products. Therefore, ZSM-5 molecular sieve can be used as a solid acid catalyst, a catalyst support, an adsorbent, and an ion exchanger, and can also be applied to important industrial production such as aromatic alkylation, catalytic cracking, light hydrocarbon aromatization, and methanol to gasoline.

[0003] The molecular sieve catalysts commonly used in the chemical industry use molecular sieves with catalytic activity as the catalyst active component, and introduce shaping aids to form particles of different shapes and sizes. Shaping is generally an essential process in the production of heterogeneous catalysts, which can provide catalysts with suitable shapes, sizes, strengths, and catalytic performances, and match the reactors. Therefore, the shaping process of molecular sieves has a great influence on the catalytic activity, stability, and lifespan of molecular sieve catalysts. Among them, the γ-alumina shaped bodies of BETA molecular sieve and ZSM-type molecular sieve are often used as carriers of adsorbents or supported catalysts due to their good pore structures, suitable specific surfaces, and high heat resistance stability. Industrial applications require the shaped samples to have a certain strength, and the original properties of the molecular sieve, such as specific surface area, reaction activity, etc., can be retained to the greatest extent, which puts forward requirements for the binder and the shaping method. Alumina is a commonly used binder due to its high specific surface area, good compressive strength, and suitable acidity and alkalinity. The shaping method usually involves mixing the molecular sieve and alumina, adding nitric acid, and then kneading and extruding into shape.

[0004] Patent CN101940944A provides a method for preparing a shaped molecular sieve catalyst by using the slurry after the crystallization of molecular sieves. The molecular sieve product and the crystallization slurry are separated from the slurry of the crystallized molecular sieve, and the two are mixed with a binder to obtain a catalyst slurry, and then the slurry is shaped to obtain a catalyst. The mechanical properties of the obtained catalyst are suitable for fluidized bed processes but not for fixed bed process catalysts with high strength requirements. Patent CN101537369 introduces a ZSM-5 catalyst, which is also obtained by mixing the ZSM-5 catalyst and γ-alumina in a certain proportion, and then adding dilute nitric acid and mixing and shaping. Patent 201711070222.0 discloses a method for extruding and shaping ZSM-5 molecular sieves, which kneads, extrudes, dries and calcines powdered ZSM-5 molecular sieves, starch containing protein and water to obtain ZSM-5 molecular sieve bars. Patent CN 108187728 B proposes an application of a shaped ZSM-5 molecular sieve catalyst. The binder SB powder, V250 powder and extrusion aid sesbania powder are added to the dry powder of the modified molecular sieve catalyst, and after mixing, a colloidal solvent mixture of nitric acid and citric acid and water is added for extrusion and shaping. Patent 201410100278.6 discloses a shaped molecular sieve catalyst, its preparation method and application. It is obtained by mixing a molecular sieve slurry with a binder, adding an extrusion aid and a colloidal solvent, processing, shaping, drying, ion-exchanging and calcining to obtain a shaped molecular sieve catalyst. Patent 201711482811.X discloses a method for shaping molecular sieves, which is to mix alumina and molecular sieves, add an inorganic aluminum salt solution with a weight concentration of 5-15%, and then carry out kneading, shaping and calcining to obtain a product. Patent 201910184212.2 proposes a method for shaping nano-molecular sieves. After uniformly mixing the nano-molecular sieve raw powder and an adhesive, the particles are placed in a rotary disk pelletizer and rolled into mother balls according to the pelletizing method; when the spherical body grows to the required size, cement powder and water are gradually added to make the sphere continue to grow to the required diameter, and then the feeding can be stopped; the prepared spherical nano-molecular sieves are dried at room temperature for 12 hours to obtain a product; through screening and polishing, a spherical nano-molecular sieve shaped body with the required size is obtained.

[0005] However, in the process of shaping the molecular sieves in the above-mentioned prior art, an inert component binder is selected to wrap the surface of the molecular sieves, which will lead to a decrease in the content and purity of the molecular sieve itself, low utilization rate, and at the same time has a diluting effect on the activity of the molecular sieves, a blocking effect on the molecular sieve pores, and affects its diffusion performance. Moreover, when traditional molecular sieves or molecular sieve slurries are spray-shaped or extruded, disadvantages such as unstable strength, catalyst fragmentation and pulverization, and an increase in the bed pressure difference will occur during the industrial application of the catalyst, invisibly increasing the industrial application cost and energy consumption of the catalyst. Summary of the Invention

[0006] The main object of the present invention is to provide a ZSM-5 molecular sieve catalyst, a preparation method thereof and an application, so as to solve the problem in the prior art that the ZSM-5 molecular sieve catalyst cannot take into account both good catalytic effect and stable strength.

[0007] To achieve the above object, according to one aspect of the present invention, a preparation method of a ZSM-5 molecular sieve catalyst is provided, including the following steps: Step S1, mixing nano-ZSM-5 molecular sieve with a binder, a pore-forming agent, a peptizing agent and an extrusion aid to obtain a mixed material; Step S2, extruding the mixed material into a formed product to obtain an intermediate product; Step S3, subjecting the intermediate product to first calcination and crystallization in sequence to obtain a ZSM-5 molecular sieve catalyst precursor; Step S4, drying, second calcination and third calcination of the ZSM-5 molecular sieve catalyst precursor in sequence to obtain a ZSM-5 molecular sieve catalyst; wherein, the binder includes a first binder and a second binder, the first binder is one or more of coarse pore silica gel, microsilica powder, silica sol, diatomite and kaolin, and the second binder is one or more of nano-aluminum oxide, pseudo-boehmite and boehmite; the pore-forming agent includes a first pore-forming agent and a second pore-forming agent, the first pore-forming agent is one or more of sesbania powder, gum arabic and ethyl cellulose; the second pore-forming agent is one or more of lignin, guar gum, cyclodextrin and polyethylene glycol 1000; the temperature of the first calcination is 500-700 °C, the temperature of the second calcination is 300-500 °C, the temperature of the third calcination is 500-700 °C, and the time of the first calcination < the time of the second calcination < the time of the third calcination.

[0008] Further, the mass ratio of the nano-ZSM-5 molecular sieve to the first binder is 1:(0.02-5.0), and the mass ratio of the nano-ZSM-5 molecular sieve to the second binder is 1:(0.01-5.0); preferably, the mass ratio of the nano-ZSM-5 molecular sieve to the first binder is 1:(0.05-0.15), and the mass ratio of the nano-ZSM-5 molecular sieve to the second binder is 1:(0.01-0.08); more preferably, the first binder is coarse pore silica gel and / or microsilica powder, and the second binder is pseudo-boehmite.

[0009] Further, the mass ratio of the nano-ZSM-5 molecular sieve to the first pore-forming agent is 1:(0.005-2.0), and the mass ratio of the nano-ZSM-5 molecular sieve to the second pore-forming agent is 1:(0.005-2.0); preferably, the mass ratio of the nano-ZSM-5 molecular sieve to the first pore-forming agent is 1:(0.02-0.04), and the mass ratio of the nano-ZSM-5 molecular sieve to the second pore-forming agent is 1:(0.03-0.06).

[0010] Further, the peptizing agent is one or more of inorganic salts, nitric acid, and citric acid; preferably, the inorganic salt is one or more of aluminum sulfate, aluminum nitrate, aluminum phosphate, and ammonium nitrate.

[0011] Further, the mass ratio of the nano-ZSM-5 molecular sieve to the peptizing agent is 1:(0.005 - 5.0); preferably, the mass ratio of the nano-ZSM-5 molecular sieve to the peptizing agent is 1:(0.2 - 0.35).

[0012] Further, the extrusion aid is one or more of white oil, synthetic engine oil, lubricating oil CL4, isomerized oil, polyalphaolefin, and base oil; preferably, the mass ratio of the nano-ZSM-5 molecular sieve to the extrusion aid is 1:(0.005 - 1.0); more preferably, the mass ratio of the nano-ZSM-5 molecular sieve to the extrusion aid is 1:(0.05 - 0.07).

[0013] Further, the time of the first calcination is 1 - 5 h, the time of the second calcination is 2 - 6 h, and the time of the third calcination is 3 - 7 h.

[0014] Further, in step S3, the crystallization temperature is 80 - 200 °C and the time is 1 - 100 h; preferably, the template agent used in the crystallization process is one or more of tetramethylammonium hydroxide, tetramethylammonium bromide, tetraethylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium hydroxide, and tetrapropylammonium bromide; more preferably, the mass ratio of the nano-ZSM-5 molecular sieve to the template agent is 1:(1.5 - 2.5).

[0015] According to another aspect of the present invention, a ZSM-5 molecular sieve catalyst obtained by the above preparation method of the present invention is provided.

[0016] According to another aspect of the present invention, the application of the above ZSM-5 molecular sieve catalyst of the present invention in the process of catalytic methanol to olefins in a fixed bed is provided.

[0017] Compared with the traditional method for preparing ZSM-5 molecular sieve catalysts, the method of the present invention does not need to use alumina type or aluminosol as a binder. By using two specific binders for recrystallization and the simultaneous pore-expanding effect of two specific pore-forming agents, the number of molecular sieve structures with catalytic activity in the catalyst increases. At the same time, by adding an appropriate amount of peptizing agent and extrusion aid to facilitate extrusion molding synergistically, the three calcinations also make the covering substances on the surface of the ZSM-5 molecular sieve removed more thoroughly. The formed catalyst has a large pore specific surface area and pore volume, high catalytic activity, and high purity of the ZSM-5 molecular sieve, stable strength, and low crushing rate, making it have a wider application range in the field of shape-selective catalysis, especially in the fixed-bed catalytic process, which is conducive to industrial preparation and application. Description of the Drawings

[0018] The accompanying drawings of the specification, which form a part of this application, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not unduly limit the present invention. In the drawings:

[0019] Figure 1 shows the XRD diffraction pattern of the ZSM-5 molecular sieve catalyst according to Embodiment 1 of the present invention; and

[0020] Figure 2 shows the SEM image of the ZSM-5 molecular sieve catalyst according to Embodiment 1 of the present invention. Detailed Description of the Invention

[0021] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0022] It should be noted that the terms "first", "second", etc. in the specification, claims and the above-mentioned drawings of this application are used to distinguish similar objects and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so as to implement the embodiments of this application described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these process, method, product or device.

[0023] As described in the background art of the present invention, there is a problem in the prior art that the ZSM-5 molecular sieve catalyst cannot take into account both good catalytic effect and stable strength. To solve the above problems, in a typical embodiment of the present invention, a preparation method of a ZSM-5 molecular sieve catalyst is provided, including the following steps: Step S1, mixing nano-ZSM-5 molecular sieve with a binder, a pore-forming agent, a peptizing agent and an extrusion aid to obtain a mixed material; Step S2, extruding the mixed material into a formed product to obtain an intermediate product; Step S3, subjecting the intermediate product to a first calcination and crystallization in sequence to obtain a ZSM-5 molecular sieve catalyst precursor; Step S4, drying, second calcination and third calcination of the ZSM-5 molecular sieve catalyst precursor in sequence to obtain a ZSM-5 molecular sieve catalyst.

[0024] Among them, the binder includes a first binder and a second binder. The first binder is one or more of coarse pore silica gel, microsilica powder, diatomaceous earth, and kaolin. The second binder is one or more of nano-aluminum oxide, pseudo-boehmite, and boehmite. The pore former includes a first pore former and a second pore former. The first pore former is one or more of sesbania powder, gum arabic, and ethyl cellulose. The second pore former is one or more of lignin, guar gum, cyclodextrin, and polyethylene glycol 1000. The temperature of the first calcination is 500-700 °C, the temperature of the second calcination is 300-500 °C, the temperature of the third calcination is 500-700 °C, and the time of the first calcination < the time of the second calcination < the time of the third calcination.

[0025] In the present invention, the nano-ZSM-5 molecular sieve is first mixed with a binder, a pore former, a peptizing agent, and an extrusion aid. Among them, there is no need to use an alumina type or aluminum sol as a binder. By using two specific binders for recrystallization and the simultaneous pore expansion effect of two specific pore formers, the number of molecular sieve structures with catalytic activity in the catalyst increases. At the same time, by adding an appropriate amount of peptizing agent and extrusion aid to facilitate extrusion molding synergistically, a mixed material is obtained. Subsequently, the mixed material is extruded into a shape to obtain an intermediate product. Then, the first calcination, crystallization, drying, second calcination, and third calcination are carried out in sequence. Through the three calcinations, the covering substances on the surface of the ZSM-5 molecular sieve are removed more thoroughly. The formed catalyst has a large pore specific surface area and pore volume, high catalytic activity, and the ZSM-5 molecular sieve has high purity, stable strength, and low breakage rate, obtaining a ZSM-5 molecular sieve catalyst that can be applied to a fixed bed catalytic process under high pressure.

[0026] In a preferred embodiment, the mass ratio of the nano-ZSM-5 molecular sieve to the first binder is 1:(0.02-5.0), and the mass ratio of the nano-ZSM-5 molecular sieve to the second binder is 1:(0.05-5.0). Preferably, the mass ratio of the nano-ZSM-5 molecular sieve to the first binder is 1:(0.05-0.15), and the mass ratio of the nano-ZSM-5 molecular sieve to the second binder is 1:(0.05-0.08). When the added mass of the binder is within the above range, it can be better adapted to the nano-ZSM-5 molecular sieve and has a comparable silicon-aluminum ratio, further increasing the number of molecular sieve structures with catalytic activity in the catalyst, so that the product formed by this method has a larger pore specific surface area and pore volume, and the catalytic activity is further increased. To further reduce the covering of the molecular sieve pore structure surface by the binder, more preferably, the first binder is coarse pore silica gel and / or microsilica powder, and the second binder is pseudo-boehmite.

[0027] When too little of the above-mentioned pore former of the present invention is added, the pore expansion effect will be unsatisfactory, and too few molecular sieve pore structures will affect the catalytic activity; when too much is added, there will be too many pore structures, resulting in the collapse of the molecular sieve framework and a decrease in strength during subsequent calcination. Therefore, in a preferred embodiment, the mass ratio of the nano-ZSM-5 molecular sieve to the first pore former is 1:(0.005-2.0), and the mass ratio of the nano-ZSM-5 molecular sieve to the second pore former is 1:(0.005-2.0); specifically, preferably, the mass ratio of the nano-ZSM-5 molecular sieve to the first pore former is 1:(0.02-0.04), and the mass ratio of the nano-ZSM-5 molecular sieve to the second pore former is 1:(0.03-0.06), and the pore expansion effect is the best.

[0028] Common components in the art can be used as the peptizing agent. For the consideration of further improving the preparation efficiency, in a preferred embodiment, the peptizing agent is one or more of inorganic salts, nitric acid and citric acid; preferably, the inorganic salt is one or more of aluminum sulfate, aluminum nitrate, aluminum phosphate and ammonium nitrate.

[0029] In a preferred embodiment, the mass ratio of the nano-ZSM-5 molecular sieve to the peptizing agent is 1:(0.005-5.0); too much peptizing agent should not be added, otherwise too much of the surface of the molecular sieve will be covered during the forming process, resulting in too high strength and affecting the activity of the catalyst instead. Preferably, the mass ratio of the nano-ZSM-5 molecular sieve to the peptizing agent is 1:(0.2-0.35), which can better balance the strength and catalytic activity of the catalyst.

[0030] The extrusion molding step can be carried out using a common extruder in the prior art. In a preferred embodiment, the extrusion aid is one or more of white oil, synthetic engine oil, lubricating oil CL4, isomerized oil, polyalphaolefin and base oil; preferably, the mass ratio of the nano-ZSM-5 molecular sieve to the extrusion aid is 1:(0.005-1.0); more preferably, the mass ratio of the nano-ZSM-5 molecular sieve to the extrusion aid is 1:(0.05-0.07). Adding an appropriate amount of extrusion aid can make the extrusion of the molecular sieve catalyst smoother. The above-mentioned weight of the extrusion aid can play a lubricating role while not affecting the porous structure of the molecular sieve itself, and can better maintain the catalytic performance of the molecular sieve.

[0031] To further remove the covering on the surface of the ZSM-5 molecular sieve, while limiting that the time of the first calcination < the time of the second calcination < the time of the third calcination, in a preferred embodiment, the time of the first calcination is 1-5 h, the time of the second calcination is 2-6 h, and the time of the third calcination is 3-7 h. The above-mentioned calcination conditions can make the formed catalyst have a larger pore specific surface area and pore volume, and higher catalytic activity.

[0032] In order to further improve the catalytic performance of the catalyst, in a preferred embodiment, in step S3, the crystallization temperature is 80-200 °C and the time is 1-100 h; preferably, the template agent used in the crystallization process is one or more of tetramethylammonium hydroxide, tetramethylammonium bromide, tetraethylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium hydroxide and tetrapropylammonium bromide; more preferably, the mass ratio of the nano-ZSM-5 molecular sieve to the template agent is 1:(1.5-2.5); the above crystallization process can convert more binder into the ZSM-5 molecular sieve structure and improve the catalytic activity of the catalyst.

[0033] In another typical embodiment of the present invention, a ZSM-5 molecular sieve catalyst is further provided, which is obtained by the preparation method of the present invention, wherein the ZSM-5 molecular sieve has high purity, a large pore specific surface area and pore volume, high catalytic activity, and stable strength and low crushing rate.

[0034] In another typical embodiment of the present invention, the application of the above ZSM-5 molecular sieve catalyst in the fixed-bed catalytic methanol-to-olefins process is further provided. The fixed-bed catalysis has the advantages of small backmixing and simple structure, but has high requirements for the strength of the catalyst. The size, shape, porous structure and distribution of active sites are investigated to ensure that it operates within the entire process requirements. At the same time, the catalyst kinetics and mass transfer parameters are also considered. This catalyst has high strength and can withstand the high pressure of the fixed-bed process and exhibit high catalytic activity.

[0035] Typical but non-limiting, the mass ratio of the nano-ZSM-5 molecular sieve to the first binder is 1:0.02, 1:0.05, 1:0.07, 1:0.1, 1:0.13, 1:0.15, 1:0.2, 1:0.5, 1:1.0, 1:2.0, 1:3.0, 1:4.0, 1:5.0 or a range value composed of any two of these ratios; typical but non-limiting, the mass ratio of the nano-ZSM-5 molecular sieve to the second binder is 1:0.01, 1:0.02, 1:0.05, 1:0.08, 1:0.1, 1:0.15, 1:0.2, 1:0.5, 1:1.0, 1:2.0, 1:3.0, 1:4.0, 1:5.0 or a range value composed of any two of these ratios.

[0036] Typically but not limited to, the mass ratio of the nano-ZSM-5 molecular sieve to the first pore-forming agent is 1:0.005, 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.1, 1:0.15, 1:0.2, 1:0.5, 1:1.0, 1:2.0, or a range value composed of any two of these ratios; typically but not limited to, the mass ratio of the nano-ZSM-5 molecular sieve to the second pore-forming agent is 1:0.005, 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.1, 1:0.15, 1:0.2, 1:0.5, 1:1.0, 1:2.0, or a range value composed of any two of these ratios.

[0037] Typically but not limited to, the mass ratio of the nano-ZSM-5 molecular sieve to the peptizing agent is 1:0.005, 1:0.01, 1:0.05, 1:0.1, 1:0.2, 1:0.3, 1:0.5, 1:1.0, 1:2.0, 1:3.0, 1:4.0, 1:5.0, or a range value composed of any two of these ratios.

[0038] Typically but not limited to, the mass ratio of the nano-ZSM-5 molecular sieve to the extrusion aid is 1:0.005, 1:0.01, 1:0.05, 1:0.07, 1:0.1, 1:0.2, 1:0.3, 1:0.5, 1:1.0, or a range value composed of any two of these ratios.

[0039] Typically but not limited to, the temperature of the first calcination is 500°C, 550°C, 600°C, 650°C, 700°C, or a range value composed of any two of these values; the temperature of the second calcination is 300°C, 350°C, 400°C, 450°C, 500°C, or a range value composed of any two of these values; the temperature of the third calcination is 500°C, 550°C, 600°C, 650°C, 700°C, or a range value composed of any two of these values.

[0040] Typically but not limited to, the time of the first calcination is 1h, 2h, 3h, 4h, 5h, or a range value composed of any two of these values; the time of the second calcination is 2h, 3h, 4h, 5h, 6h, or a range value composed of any two of these values; the time of the third calcination is 3h, 4h, 5h, 6h, 7h, or a range value composed of any two of these values.

[0041] Typically but not limited to, the crystallization temperature is 80 °C, 100 °C, 120 °C, 140 °C, 160 °C, 180 °C, 200 °C or a range value composed of any two of these values; the crystallization time is 1 h, 12 h, 24 h, 36 h, 48 h, 60 h, 72 h, 84 h, 96 h, 100 h or a range value composed of any two of these values.

[0042] Typically but not limited to, the mass ratio of nano-ZSM-5 molecular sieve to template agent is 1:1.5, 1:1.8, 1:2.0, 1:2.3, 1:2.5 or a range value composed of any two of these ratios.

[0043] The following further describes the present application in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present application.

[0044] Example 1

[0045] Step S1, 15 g of nano-ZSM-5 molecular sieve, 1.0 g of microsilica (SiO2 mass fraction 95%), 0.5 g of pseudoboehmite, 0.55 g of talc powder, 0.45 g of guar gum, and 0.8 g of white oil are sequentially stirred evenly to obtain a wet powder system; 9.2 g of Al(NO3)3·9H2O and 50 g of deionized water are mixed evenly and ultrasonically stirred at 35 °C for 1 h to obtain a dispersed phase aqueous solution A of 0.5 mol / L salts; 8.6 g of nitric acid and 50 g of deionized water are mixed evenly to obtain a dispersed phase aqueous solution B of 0.02 mol / L salts. 3.5 g of the mixed aqueous solution of nitric acid and aluminum nitrate is slowly added dropwise to the wet powder system, and stirring is continued at 20 - 100 °C for 0.1 - 5 h to obtain a flocculent wet gel;

[0046] Step S2, the flocculent wet gel is extruded into a cylindrical shape and air-dried for 1 - 24 h to obtain an intermediate product;

[0047] Step S3, after the intermediate product is calcined at 550 °C for 3 h, 30 g of tetrapropylammonium hydroxide template agent is added, and crystallization is carried out at 120 °C for 24 h to obtain a ZSM-5 molecular sieve catalyst precursor;

[0048] Step S4, after the ZSM-5 molecular sieve catalyst precursor is dried, it is first calcined at 350 °C for 4 h, and then at 550 °C for 6 h to obtain a ZSM-5 molecular sieve catalyst.

[0049] Examples 2 to 8

[0050] The differences between Examples 2 to 8 and Example 1 lie in the binder, pore former, peptizing agent and extrusion aid, their addition amounts, and the preparation process parameters. See Tables 1 to 2 for details.

[0051] Examples 9 to 10

[0052] Examples 9 to 10 are different from Example 1 in that the addition amounts of the binder, pore former, peptizing agent, and extrusion aid are different. See Table 1 for details.

[0053] Examples 11 to 12

[0054] Examples 11 to 12 are different from Example 1 in that the preparation process parameters are different. See Table 2 for details.

[0055] Comparative Examples 1 to 2

[0056] Comparative Examples 1 to 2 are different from Example 1 in that the preparation process parameters are different. See Table 2 for details.

[0057] Comparative Example 3

[0058] Comparative Example 3 is different from Example 1 in that 1.0 g of microsilica powder (SiO2 mass fraction 95%) and 0.5 g of alumina are used as the binder.

[0059] Comparative Example 4

[0060] Comparative Example 4 is different from Example 1 in that 1 g of sesbania powder is used as the pore former.

[0061] The XRD diffraction pattern of the ZSM-5 molecular sieve catalyst prepared in Example 1 is as Figure 1 shown, and the SEM image is as Figure 2 shown. The specific surface area of the catalyst and the purity of ZSM-5 molecular sieve in the above examples and comparative examples measured by BET are shown in Table 3.

[0062] Table 1

[0063]

[0064]

[0065]

[0066] Table 2

[0067]

[0068] Table 3

[0069]

[0070]

[0071] As can be seen from the above, compared with the conventional method for preparing ZSM-5 molecular sieve catalyst in the comparative example, each embodiment of the present invention does not need to use alumina type or aluminum sol as a binder. By using two specific binders for recrystallization and the simultaneous pore-expanding effect of two specific pore-forming agents, the amount of molecular sieve structure with catalytic activity in the catalyst increases. At the same time, by adding an appropriate amount of peptizing agent and extrusion aid to facilitate extrusion molding synergistically, the three-time calcination also makes the coverings on the surface of ZSM-5 molecular sieve removed more thoroughly. The formed catalyst has a large pore specific surface area and pore volume, high catalytic activity, and the ZSM-5 molecular sieve has high purity, stable strength and low crushing rate, with excellent comprehensive performance. In addition, it can be seen that when all process parameters are within the preferred range of the present invention, the comprehensive performance of the catalyst is better.

[0072] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a ZSM-5 molecular sieve catalyst, characterized in that, It includes the following steps: Step S1: Mix the nano-ZSM-5 molecular sieve with a binder, a pore former, a peptizing agent, and an extrusion aid to obtain a mixed material; Step S2: Extrude the mixed material into a formed product to obtain an intermediate product; Step S3: Subject the intermediate product to first calcination and crystallization in sequence to obtain a ZSM-5 molecular sieve catalyst precursor; Step S4: Subject the ZSM-5 molecular sieve catalyst precursor to drying, second calcination, and third calcination in sequence to obtain the ZSM-5 molecular sieve catalyst; Among them, the binder includes a first binder and a second binder. The first binder is one or more of macroporous silica gel, microsilica powder, silica sol, diatomaceous earth, and kaolin. The second binder is one or more of nano-aluminum oxide, pseudoboehmite, and boehmite; The pore former includes a first pore former and a second pore former. The first pore former is one or more of sesbania powder, gum arabic, and ethyl cellulose. The second pore former is one or more of lignin, guar gum, cyclodextrin, and polyethylene glycol 1000; The peptizing agent is an inorganic salt, a mixture of an inorganic salt and nitric acid, a mixture of an inorganic salt and citric acid, or a mixture of an inorganic salt, nitric acid, and citric acid. The inorganic salt is one or more of aluminum sulfate, aluminum nitrate, aluminum phosphate, and ammonium nitrate; The extrusion aid is one or more of white oil, synthetic engine oil, lubricating oil CL4, isomerized oil, polyalphaolefin, and base oil; The temperature of the first calcination is 500 - 700 °C, the temperature of the second calcination is 300 - 500 °C, the temperature of the third calcination is 500 - 700 °C, and the time of the first calcination < the time of the second calcination < the time of the third calcination.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the nano-ZSM-5 molecular sieve to the first binder is 1:(0.02 - 5.0), and the mass ratio of the nano-ZSM-5 molecular sieve to the second binder is 1:(0.01 - 5.0).

3. The preparation method according to claim 2, characterized in that, The mass ratio of the nano-ZSM-5 molecular sieve to the first binder is 1:(0.05 - 0.15), and the mass ratio of the nano-ZSM-5 molecular sieve to the second binder is 1:(0.01 - 0.08).

4. The preparation method according to claim 3, characterized in that, The first binder is macroporous silica gel and / or microsilica powder, and the second binder is pseudoboehmite.

5. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of the nano-ZSM-5 molecular sieve to the first pore former is 1:(0.005 - 2.0), and the mass ratio of the nano-ZSM-5 molecular sieve to the second pore former is 1:(0.005 - 2.0).

6. The preparation method according to claim 5, characterized in that, The mass ratio of the nano-ZSM-5 molecular sieve to the first pore former is 1:(0.02 - 0.04), and the mass ratio of the nano-ZSM-5 molecular sieve to the second pore former is 1:(0.03 - 0.06).

7. The preparation method according to claim 1 or 2, characterized in that The mass ratio of the nano-ZSM-5 molecular sieve to the peptizing agent is 1:(0.005 - 5.0).

8. The preparation method according to claim 7, wherein The mass ratio of the nano-ZSM-5 molecular sieve to the peptizing agent is 1:(0.2 - 0.35).

9. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of the nano-ZSM-5 molecular sieve to the extrusion aid is 1:(0.005 - 1.0).

10. The preparation method according to claim 9, characterized in that, The mass ratio of the nano-ZSM-5 molecular sieve to the extrusion aid is 1:(0.05~0.07).

11. The preparation method according to claim 1 or 2, characterized in that, The time of the first calcination is 1~5 h, the time of the second calcination is 2~6 h, and the time of the third calcination is 3~7 h.

12. The preparation method according to claim 1 or 2, characterized in that, In the step S3, the crystallization temperature is 80~200 °C and the time is 1~100 h.

13. The preparation method according to claim 12, characterized in that, In the step S3, the template agent used in the crystallization process is one or more of tetramethylammonium hydroxide, tetramethylammonium bromide, tetraethylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium hydroxide, and tetrapropylammonium bromide.

14. The preparation method according to claim 13, characterized in that, In the step S3, the mass ratio of the nano-ZSM-5 molecular sieve to the template agent is 1:(1.5~2.5).

15. A ZSM-5 molecular sieve catalyst, characterized in that, Obtained by the preparation method according to any one of claims 1 to 14.

16. Use of the ZSM-5 molecular sieve catalyst according to claim 15 in the process of catalytic methanol to olefins in a fixed bed.

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