HZSM-5 molecular sieve catalyst and preparation method thereof, and reaction for preparing propylene from methanol

Abstract

The application provides a HZSM-5 molecular sieve catalyst, a preparation method thereof and a reaction of preparing propylene from methanol. The HZSM-5 molecular sieve catalyst comprises HZSM-5 molecular sieve and a binder, the binder is located between the particles of the HZSM-5 molecular sieve, the mass ratio of the HZSM-5 molecular sieve to the binder is 75-80:20-25, and the compressive strength of the HZSM-5 molecular sieve catalyst is 9.5-12 N / mm. The HZSM-5 molecular sieve catalyst comprises HZSM-5 molecular sieve and a binder, the HZSM-5 molecular sieve has a suitable pore size and high catalytic activity, and the binder is used to bond the particles of the HZSM-5 molecular sieve to form a catalyst with higher catalytic activity. Therefore, the HZSM-5 molecular sieve catalyst has strong abilities of resisting carbon deposition and resisting pulverization.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more specifically, to an HZSM-5 molecular sieve catalyst and its preparation method, and to a reaction catalyzing the production of propylene from methanol. Background Technology

[0002] Propylene, as an important basic raw material in the petrochemical industry, is mainly used to produce downstream products such as polypropylene (PP), acrylic acid (AA), butanol (BA), acetone (PK), phenol (Phenol), octanol (CA), acrylonitrile (AN), propylene oxide (PO), and isopropanol (IPA).

[0003] Traditional propylene production routes in China mainly include steam cracking and refinery gas repackaging, with the former accounting for over 60% of the total propylene supply. In recent years, with the industrialization of coal chemical and propane dehydrogenation (PDH) plants, my country's propylene supply situation has changed significantly. Methanol-to-olefins (MTO) and methanol-to-propylene (MTP) are important pathways for obtaining propylene products in coal chemical processes. Both technologies have achieved industrial-scale production. MTO technology primarily produces ethylene and propylene in equal proportions, while MTP technology primarily produces propylene. Currently, Lurgi's MTP process is the most widely used in large-scale production.

[0004] Chinese Patent CN107282087B discloses a high-silicon ZSM-5 molecular sieve, its preparation method, and its application. Specifically, it relates to a method for preparing a high-silicon ZSM-5 molecular sieve, which includes: uniformly mixing a liquid alkaline silicon source, an aluminum source, ZSM-5 molecular sieve seed crystals, a template agent, an alkali, urea, and water, followed by aging and hydrothermal synthesis crystallization. Urea is added during the uniform mixing stage of the raw materials. The liquid alkaline silicon source is calculated as SiO2, and the aluminum source is calculated as Al2O3. The mixing ratio of the raw materials satisfies the following: the molar ratio of liquid alkaline silicon source, aluminum source, template agent, alkali, urea, and water is 1:(0.001~0.01):(0.025~0.25):(0.02~0.2):(0.3~4):(8~100), and the weight ratio of ZSM-5 molecular sieve seed crystals to SiO2 in the liquid alkaline silicon source is (1~10):100. When the prepared sheet-like high-silica ZSM-5 molecular sieve was used to catalyze the reaction of methanol to propylene and / or butene, the selectivity of C3 and / or C4 olefin products was improved.

[0005] Chinese patent CN109721077B discloses a sheet-like Fe-ZSM-5 zeolite molecular sieve and its preparation method. The crystal thickness of the sheet-like Fe-ZSM-5 zeolite molecular sieve is 60-100 nm. It is obtained by adding different amounts of nanocrystal seeds and adjusting the amount of NH4F. This invention addresses the problems of Fe-ZSM-5 zeolite molecular sieves synthesized under the OH- system having a high non-framework Fe content and Fe-ZSM-5 zeolite molecular sieves synthesized under the F- system having large crystal grains and long crystallization times. Through the combined action of seeds, NH4F, and a dual template agent, nanosheet-like Fe-ZSM-5 zeolite molecular sieves are obtained in a very short crystallization time. This method is beneficial for the diffusion of coking precursors and products in the methanol-to-propylene reaction. Moreover, the content of non-framework Fe is significantly reduced compared to the OH- system synthesis method, thereby reducing the selectivity of the byproduct methane during the reaction and exhibiting a longer lifespan and higher propylene selectivity.

[0006] Chinese Patent CN106466619B discloses a catalyst for methanol-to-propylene conversion and its preparation method. This invention primarily addresses the problems of poor stability and low propylene selectivity in existing methanol-to-propylene catalysts. The present invention effectively solves these problems by employing a binder-free, hierarchical porous ZSM-5 molecular sieve catalyst composed of 90-100% ZSM-5 molecular sieve, 0.05-3% boron or aluminum, and 0-5% rare earth elements. This catalyst can be used in the industrial production of propylene from methanol.

[0007] Chinese patent CN108046288B discloses a method for preparing hierarchical porous ZSM-5 molecular sieves for methanol-to-propylene production, comprising: a) mixing an aluminum source, a silicon source, an alkali source, ZSM-5 molecular sieve seed crystals with water to form a gel; b) pre-crystallizing the gel in a reaction vessel at 80–140°C for 6–48 h; c) rapidly cooling the pre-crystallized product obtained in step b, then adding an organic template agent, and finally heating the pre-crystallized product with the template agent to 100–180°C for crystallization reaction; the crystallized product after the reaction is completed is subjected to solid-liquid separation, washing, and drying to obtain molecular sieve powder; d) placing the molecular sieve powder obtained in step c into an ammonium salt solution for ion exchange to obtain an ammonia-type ZSM-5 molecular sieve, and then calcining to obtain HZSM-5 molecular sieve, the obtained HZSM-5 molecular sieve exhibiting good propylene selectivity and anti-carbon deposition properties.

[0008] The above-mentioned authorized patents are mostly aimed at improving and optimizing the active component of MTP (i.e., ZSM-5 molecular sieve) and its preparation technology, such as improving its reactivity through element modification, pore structure adjustment, morphology control or particle size reduction, but rarely address the pulverization problem that occurs in actual production.

[0009] ZSM-5 molecular sieve is the preferred active component in the MTP process. After being combined with a binder and granulated, ZSM-5 molecular sieve has become the only MTP catalyst to achieve industrial application. However, in actual production, the catalyst undergoes multiple reaction-regeneration operations, resulting in particle pulverization. These reaction-regeneration operations include heating and cooling, changing the process medium, and high-temperature calcination. Extensive catalyst pulverization not only affects catalyst activity and alters reaction products but also leads to increased pressure drop in the reactor bed, posing safety risks.

[0010] Therefore, it is of great significance to develop a novel ZSM-5 molecular sieve catalyst that can significantly increase catalytic reaction activity and has strong resistance to carbon deposition and pulverization for MTP reaction. Summary of the Invention

[0011] The main objective of this invention is to provide an HZSM-5 molecular sieve catalyst and its preparation method, as well as a reaction for catalyzing the production of propylene from methanol, in order to solve the problem of easy pulverization of HZSM-5 molecular sieve catalysts in the prior art.

[0012] To achieve the above objectives, according to one aspect of the present invention, an HZSM-5 molecular sieve catalyst is provided, comprising an HZSM-5 molecular sieve and a binder, wherein the binder is located between the particles of the HZSM-5 molecular sieve, the mass ratio of the HZSM-5 molecular sieve to the binder is 75-80:20-25, and the compressive strength of the HZSM-5 molecular sieve catalyst is 9.5-12 N / mm.

[0013] Further, the binder is selected from any one or more of boehmite, SB powder and aluminum oxide; further, preferably the binder is a mixture of boehmite and aluminum oxide, and the mass ratio of boehmite to aluminum oxide is 3-5:7-10.

[0014] Furthermore, the amount of acidic sites in the above-mentioned HZSM-5 molecular sieve catalyst is 0.02–0.03 mmol / g; and / or, the specific surface area of ​​the HZSM-5 molecular sieve catalyst is 325–340 m². 2 / g; and / or, the porosity of the HZSM-5 molecular sieve catalyst is 45% to 55%; and / or, the average pore size of the HZSM-5 molecular sieve catalyst is 3.5 to 4.5 nm.

[0015] According to another aspect of the present invention, a method for preparing the aforementioned HZSM-5 molecular sieve catalyst is provided. The method includes: mixing raw materials comprising HZSM-5 molecular sieve, binder, pore expander, extrusion aid, and nitric acid aqueous solution, and then sequentially extruding, drying, and calcining to obtain the HZSM-5 molecular sieve catalyst.

[0016] Furthermore, the mass ratio of the above-mentioned HZSM-5 molecular sieve, pore expander, extrusion aid to nitric acid aqueous solution is 75-80:3-3.5:2.5-3:1.7-2.5; and / or, the mass concentration of nitric acid aqueous solution is 3.5-5 wt%.

[0017] Furthermore, the silicon-to-aluminum ratio of the HZSM-5 molecular sieve is 300-500:1; and / or, the particle size of the HZSM-5 molecular sieve is 250-300 mesh; and / or, the particle size of the binder is 450-500 mesh, preferably the ratio of the particle size of the binder to the particle size of the HZSM-5 molecular sieve is 46-48:26-28.

[0018] Furthermore, the aforementioned pore-expanding agent is guar gum powder, and the dynamic viscosity of the guar gum powder is 2000-3000 cP; and / or, the extrusion aid is selected from any one or more of glycerol, polyacrylamide, and silicone resin; preferably, the extrusion aid is glycerol.

[0019] Furthermore, the temperature of the above drying treatment is 60–80°C; and / or the drying time is 4–8 hours.

[0020] Furthermore, the calcination temperature is 500–550°C; and / or the calcination time is 6–8 hours.

[0021] According to another aspect of the present invention, a reaction for the preparation of propylene from methanol using a catalyst is provided, the catalyst being the aforementioned HZSM-5 molecular sieve catalyst.

[0022] Applying the technical solution of this invention, the catalyst of this application comprises an HZSM-5 molecular sieve and a binder. The HZSM-5 molecular sieve has a suitable pore size and high catalytic activity. The binder's role is to bond the HZSM-5 molecular sieve particles together to form a catalyst with higher catalytic activity. Preferably, the mass ratio of HZSM-5 molecular sieve to binder is controlled within the aforementioned range, making the pore size distribution of the catalyst more uniform. On the one hand, this helps improve the uniformity of stress on the catalyst, enabling this application to have the compressive strength within the aforementioned range, thereby reducing the probability of catalyst pulverization due to uneven stress during catalysis. On the other hand, it helps provide more catalytic active sites for the catalyst, thereby improving the catalyst's catalytic activity. Therefore, the catalyst of this application has strong resistance to carbon deposition and pulverization. Attached Figure Description

[0023] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0024] Figure 1 The pore size distribution diagram of the HZSM-5 molecular sieve catalyst in Example 1 of this application is shown;

[0025] Figure 2 A schematic diagram of the evaluation apparatus for the methanol-to-propylene reaction catalyst of this application is shown;

[0026] Figure 3 A schematic diagram of the loading of the HZSM-5 molecular sieve catalyst of this application is shown.

[0027] The above figures include the following reference numerals:

[0028] 1. Reactor; 2. Condenser; 3. Reactor inlet; 4. Upper section of reactor; 5. Middle section of reactor; 6. Lower section of reactor. Detailed Implementation

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] As analyzed in the background section of this application, the existing technology has the problem that HZSM-5 molecular sieve catalysts are prone to pulverization. In order to solve the above problems, this application provides an HZSM-5 molecular sieve catalyst, its preparation method, and a reaction for catalyzing the production of propylene from methanol.

[0031] In a typical embodiment of this application, an HZSM-5 molecular sieve catalyst is provided, which includes an HZSM-5 molecular sieve and a binder. The binder is located between the particles of the HZSM-5 molecular sieve. The mass ratio of the HZSM-5 molecular sieve to the binder is 75-80:20-25. The compressive strength of the HZSM-5 molecular sieve catalyst is 9.5-12 N / mm.

[0032] The catalyst of this application comprises an HZSM-5 molecular sieve and a binder. The HZSM-5 molecular sieve has a suitable pore size and high catalytic activity. The binder's role is to bind the HZSM-5 molecular sieve particles together to form a catalyst with higher catalytic activity. Preferably, the mass ratio of HZSM-5 molecular sieve to binder is controlled within the aforementioned range, resulting in a more uniform pore size distribution of the catalyst. On the one hand, this helps improve the uniformity of stress on the catalyst, enabling the catalyst to achieve the compressive strength within the aforementioned range, thereby reducing the probability of catalyst pulverization due to uneven stress during catalysis. On the other hand, it helps provide more catalytic active sites for the catalyst, thereby improving its catalytic activity. Therefore, the catalyst of this application has strong resistance to carbon deposition and pulverization.

[0033] In one embodiment of this application, the binder is selected from any one or more of boehmite, SB powder, and aluminum oxide; further, it is preferred that the binder is a mixture of boehmite and aluminum oxide, and the mass ratio of boehmite to aluminum oxide is 3-5:7-10.

[0034] Preferably controlling the type of binder within the above-mentioned range helps to enrich the variety of binder raw materials. Compared with alumina, boehmite contains incompletely crystalline water molecules, and its time to become colloidal is shorter than that of alumina. The simultaneous addition of boehmite and alumina allows for a stepwise dissolution time of the binder, resulting in more uniform catalyst bonding during the molding process. Preferably controlling the mass ratio of boehmite to alumina within the above-mentioned range helps to further improve the bonding force between HZSM-5 molecular sieve particles, thereby further enhancing the catalyst's resistance to pulverization.

[0035] In one embodiment of this application, the amount of acidic sites in the HZSM-5 molecular sieve catalyst is 0.02–0.03 mmol / g; and / or, the specific surface area of ​​the HZSM-5 molecular sieve catalyst is 325–340 m². 2 / g; and / or, the porosity of the HZSM-5 molecular sieve catalyst is 45% to 55%; and / or, the average pore size of the HZSM-5 molecular sieve catalyst is 3.5 to 4.5 nm.

[0036] HZSM-5 molecular sieve catalysts with an amount of acidic sites within the aforementioned range exhibit high catalytic activity, thus demonstrating strong resistance to carbon deposition. HZSM-5 molecular sieve catalysts with the aforementioned specific surface area, porosity, and average pore size range also generate less thermal stress during catalysis, resulting in higher resistance to pulverization.

[0037] In another typical embodiment of this application, a method for preparing the aforementioned HZSM-5 molecular sieve catalyst is provided. The preparation method includes: mixing raw materials including HZSM-5 molecular sieve, binder, pore expander, extrusion aid, and nitric acid aqueous solution, and then sequentially extruding, drying, and calcining to obtain the HZSM-5 molecular sieve catalyst.

[0038] The catalyst is formed by calcining HZSM-5 molecular sieve and binder. The pore expander increases the pore size of the catalyst, and the extrusion aid improves the extrusion molding efficiency. The addition of nitric acid and water ensures sufficient contact between the HZSM-5 molecular sieve, binder, pore expander, and extrusion aid. The pore expander, extrusion aid, and nitric acid are removed during calcination, resulting in a catalyst with a large specific surface area. The above preparation method has the advantages of simple process and low cost, and the prepared catalyst has strong resistance to carbon deposition and pulverization.

[0039] In one embodiment of this application, the mass ratio of the above-mentioned HZSM-5 molecular sieve, pore expander, extrusion aid and nitric acid aqueous solution is 75-80:3-3.5:2.5-3:1.7-2.5; and / or, the mass concentration of the nitric acid aqueous solution is 3.5-5 wt%.

[0040] Preferably controlling the mass ratio of HZSM-5 molecular sieve, pore expander, extrusion aid, and nitric acid aqueous solution within the above-mentioned range helps to further improve the specific surface area and pore size distribution uniformity of the catalyst, thereby further improving the catalyst's resistance to carbon deposition and pulverization. Preferably controlling the concentration of nitric acid aqueous solution within the above-mentioned range helps to further improve the mixing uniformity of HZSM-5 molecular sieve with other components.

[0041] In one embodiment of this application, the silicon-to-aluminum ratio of the HZSM-5 molecular sieve is 300-500:1; and / or, the particle size of the HZSM-5 molecular sieve is 250-300 mesh; and / or, the particle size of the binder is 450-500 mesh, preferably the ratio of the particle size of the binder to the particle size of the HZSM-5 molecular sieve is 46-48:26-28.

[0042] Preferably controlling the silica-alumina ratio of the HZSM-5 molecular sieve within the aforementioned range helps to ensure that the shaped catalyst has a suitable number and strength of acidic sites, thereby promoting high propylene selectivity during the MTP reaction. Preferably controlling the particle size of the HZSM-5 molecular sieve and the binder within the aforementioned range helps to create a synergistic effect between the binder, HZSM-5 molecular sieve, and other components, resulting in a tighter bond between the components and improving the catalyst's resistance to pulverization. Preferably controlling the particle size of the binder and the HZSM-5 molecular sieve within the aforementioned range also helps to ensure uniform distribution among the binder, HZSM-5 molecular sieve, and pore expander. The resulting catalyst after calcination has higher porosity and more active sites, allowing for timely heat removal during the reaction and preventing localized heat release that cannot diffuse, thus avoiding catalyst fragmentation and pulverization.

[0043] To further improve the specific surface area and pore size distribution uniformity of the catalyst and to improve the efficiency of extrusion molding, in one embodiment of this application, the pore-expanding agent is preferably guar gum powder with a dynamic viscosity of 2000-3000 cP; and / or, the extrusion aid is selected from any one or more of glycerol, polyacrylamide and silicone resin; preferably, the extrusion aid is glycerol.

[0044] In order to fully remove moisture, in one embodiment of this application, the temperature of the above drying treatment is preferably 60-80°C; and / or the drying time is 4-8 hours.

[0045] In order to promote the formation of HZSM-5 catalyst, in one embodiment of this application, the calcination temperature is preferably 500-550°C; and / or the calcination time is 6-8 hours.

[0046] In another typical embodiment of this application, a reaction for preparing propylene from methanol using a catalyst is provided, wherein the catalyst is the aforementioned HZSM-5 molecular sieve catalyst.

[0047] Since the catalyst in the above-mentioned reaction of methanol to propylene is the catalyst of this application, the reaction has a high reaction efficiency.

[0048] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0049] Example 1

[0050] Weigh 200g of HZSM-5 molecular sieve. The silica-to-alumina ratio of HZSM-5 molecular sieve is 400:1, and the particle size of HZSM-5 molecular sieve is 275 mesh. Mix HZSM-5 molecular sieve, 55g of a mixture of boehmite and alumina, 8g of guar gum powder, and 6.5g of glycerol for 30 minutes. The mass ratio of boehmite to alumina is 3:7, and the particle size of both boehmite and alumina is 470 mesh. The dynamic viscosity of guar gum powder is 3000 cP. 5g of a 5% nitric acid aqueous solution was added to the mixture and kneaded for 30 minutes. The mixture was then extruded using a twin-screw extruder with a 3.0mm diameter perforated plate. The resulting strips were allowed to stand at room temperature for 24 hours, dried at 80℃ for 4 hours, and calcined in a muffle furnace at 500℃ for 8 hours to obtain the HZSM-5 molecular sieve catalyst. The pore size distribution of the HZSM-5 molecular sieve catalyst was tested, and the results are shown below. Figure 1 As shown, from Figure 1 It can be seen that the pore size distribution of the HZSM-5 molecular sieve catalyst is relatively uniform. The mass ratio of HZSM-5 molecular sieve to binder is 80:22.

[0051] Example 2

[0052] The difference from Example 1 is that the mass of HZSM-5 molecular sieve is 200g, and the mass of the mixture of boehmite and alumina is 50g, ultimately yielding the HZSM-5 molecular sieve catalyst. The mass ratio of HZSM-5 molecular sieve to binder is 80:20.

[0053] Example 3

[0054] The difference from Example 1 is that the mass of HZSM-5 molecular sieve is 187.5 g, and the mass of the mixture of boehmite and alumina is 62.5 g, ultimately yielding the HZSM-5 molecular sieve catalyst. The mass ratio of HZSM-5 molecular sieve to binder is 75:25.

[0055] Example 4

[0056] The difference from Example 1 is that the mass ratio of boehmite to alumina is 3:10, resulting in the HZSM-5 molecular sieve catalyst.

[0057] Example 5

[0058] The difference from Example 1 is that the mass ratio of pseudoboehmite to alumina is 5:7, and the final product is HZSM-5 molecular sieve catalyst.

[0059] Example 6

[0060] The difference from Example 1 is that the mass ratio of pseudoboehmite to alumina is 3:5, and the final product is HZSM-5 molecular sieve catalyst.

[0061] Example 7

[0062] The difference from Example 1 is that the mass ratio of HZSM-5 molecular sieve, guar gum powder, glycerol and nitric acid aqueous solution is 80:3:3:1.7, and the final product is HZSM-5 molecular sieve catalyst.

[0063] Example 8

[0064] The difference from Example 1 is that the mass ratio of HZSM-5 molecular sieve, guar gum powder, glycerol and nitric acid aqueous solution is 75:3.5:2.5:2.5, and the final product is HZSM-5 molecular sieve catalyst.

[0065] Example 9

[0066] The difference from Example 1 is that the mass ratio of HZSM-5 molecular sieve, guar gum powder, glycerol and nitric acid aqueous solution is 90:2.5:3.5:1.5, and the final product is HZSM-5 molecular sieve catalyst.

[0067] Example 10

[0068] The difference from Example 1 is that the particle size of HZSM-5 molecular sieve is 280 mesh, the particle size of the mixture of boehmite and alumina is 460 mesh, and the particle size ratio of the mixture of boehmite and alumina to HZSM-5 molecular sieve is 46:28, thus obtaining HZSM-5 molecular sieve catalyst.

[0069] Example 11

[0070] The difference from Example 1 is that the particle size of HZSM-5 molecular sieve is 260 mesh, the particle size of the mixture of boehmite and alumina is 480 mesh, and the particle size ratio of the mixture of boehmite and alumina to HZSM-5 molecular sieve is 48:26, thus obtaining HZSM-5 molecular sieve catalyst.

[0071] Example 12

[0072] The difference from Example 1 is that the particle size of HZSM-5 molecular sieve is 250 mesh, and the particle size of the mixture of boehmite and alumina is 500 mesh, ultimately yielding HZSM-5 molecular sieve catalyst.

[0073] Example 13

[0074] The difference from Example 1 is that the particle size of HZSM-5 molecular sieve is 300 mesh, and the particle size of the mixture of boehmite and alumina is 450 mesh, ultimately yielding HZSM-5 molecular sieve catalyst.

[0075] Example 14

[0076] The difference from Example 1 is that the particle size of HZSM-5 molecular sieve is 350 mesh, and the particle size of the mixture of boehmite and alumina is 400 mesh, ultimately yielding HZSM-5 molecular sieve catalyst.

[0077] Example 15

[0078] The difference from Example 1 is that the concentration of the nitric acid aqueous solution is 3.5%, the dynamic viscosity of the guar gum powder is 2000 cP, the drying temperature is 60°C, the drying time is 8 h, the calcination temperature is 550°C, and the calcination time is 6 h, finally obtaining the HZSM-5 molecular sieve catalyst.

[0079] Comparative Example 1

[0080] The difference from Example 1 is that the mass of HZSM-5 molecular sieve is 200g, and the mass of the mixture of boehmite and alumina is 41g, ultimately yielding the HZSM-5 molecular sieve catalyst. The mass ratio of HZSM-5 molecular sieve to binder is 80:16.4.

[0081] Performance testing

[0082] The catalysts prepared in the above examples and comparative examples were tested using a methanol-to-propylene catalyst evaluation device. A schematic diagram of the methanol-to-propylene catalyst evaluation device is shown below. Figure 2 As shown, specifically, the reaction liquid is fed into reactor 1 using a feed pump, while nitrogen gas is introduced into the reactor at the same time. Glass beads are filled in the upper section 4 and the lower section 6 of the reactor, and a catalyst is filled in the middle section 5 of the reactor.

[0083] A schematic diagram of catalyst loading is shown below. Figure 3 As shown, the distance between the feed inlet 1 and the top of the middle section 5 of the reactor is 28 cm. The gaseous product after the reaction liquid and catalyst are condensed in condenser 2 to obtain the liquid product. The gaseous product is then analyzed by gas chromatography. The reactor 1 has dimensions of 20mm * 12mm * 400mm, a catalyst loading mass of 5g, a catalyst particle size of 10-20 mesh, and glass beads with a particle size of 2-3mm. The bottom of reactor 1 is sealed with a filter screen. A thermocouple is inserted in the middle of the catalyst bed to monitor the actual reaction temperature in real time. The feed space velocity is 1 h⁻¹. -1The reaction temperature was 480℃. Sampling began after 5 hours of operation, with a sampling frequency of 2 hours per sample. All components were analyzed online. After 24 hours of operation, the space velocity was adjusted to 2 hours per sample. -1 After 48 hours of operation, the airspeed will be adjusted to 3 hours. -1 The experiment was stopped when the methanol conversion rate reached ≤95% at this space velocity, indicating catalyst deactivation. The sampling frequency remained constant throughout the experiment. Catalyst activity and lifetime were tested during the experiment. After catalyst deactivation, the catalyst was removed and its pulverization rate was tested.

[0084] Acidic site test

[0085] Acidity determination was performed on a BELCAT-II atmospheric pressure chemisorption analyzer using high-purity helium as the carrier gas at a flow rate of 50 L / min and a catalyst loading of 0.05 g. Catalyst activation was performed by increasing the temperature from room temperature to 550 °C at a rate of 10 °C / min and holding for 1 h. The temperature was then decreased to 100 °C to adsorb ammonia until saturation, followed by purging for 20 min to remove physically adsorbed NH3. The temperature was then increased to 610 °C at a rate of 10 °C / min, and the desorption curve was recorded. Quantitative acidity determination of the catalyst sample was achieved by passing an ammonia-helium mixture through a flow meter, detecting the ammonia using a thermal conductivity detector (TCD), and integrating the peak area to plot a correction curve for the ammonia quantity versus the peak area. The test sample adsorbed ammonia at 100 °C. After adsorption, the temperature was programmed to increase to 610 °C at a rate of 10 °C / min to desorb the adsorbed ammonia. The desorption peak was detected using a TCD, integrated, and the amount of desorbed ammonia, i.e., the amount of acidic sites, was calculated based on the desorption peak area.

[0086] The results of testing the acid sites, compressive strength, specific surface area, porosity, pore size, pore size distribution, lifetime, and pulverization rate of the catalysts prepared in the above examples and comparative examples are shown in Table 1.

[0087] Table 1

[0088]

[0089]

[0090] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0091] The catalyst of this application comprises an HZSM-5 molecular sieve and a binder. The HZSM-5 molecular sieve has a suitable pore size and high catalytic activity. The binder's role is to bind the HZSM-5 molecular sieve particles together to form a catalyst with higher catalytic activity. Preferably, the mass ratio of HZSM-5 molecular sieve to binder is controlled within the aforementioned range, resulting in a more uniform pore size distribution of the catalyst. On the one hand, this helps improve the uniformity of stress on the catalyst, enabling the catalyst to achieve the compressive strength within the aforementioned range, thereby reducing the probability of catalyst pulverization due to uneven stress during catalysis. On the other hand, it helps provide more catalytic active sites for the catalyst, thereby improving its catalytic activity. Therefore, the catalyst of this application has strong resistance to carbon deposition and pulverization.

[0092] The above are merely embodiments of the present invention and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an HZSM-5 molecular sieve catalyst, characterized in that, The preparation method includes: The raw materials, including HZSM-5 molecular sieve, binder, pore expander, extrusion aid, and nitric acid aqueous solution, are mixed and then sequentially extruded, dried, and calcined to obtain the HZSM-5 molecular sieve catalyst; the mass ratio of the HZSM-5 molecular sieve, the pore expander, the extrusion aid, and the nitric acid aqueous solution is 75~80:3~3.5:2.5~3:1.7~2.5; The HZSM-5 molecular sieve catalyst comprises an HZSM-5 molecular sieve and a binder. The binder is located between the particles of the HZSM-5 molecular sieve. The mass ratio of the HZSM-5 molecular sieve to the binder is 75~80:20~25. The compressive strength of the HZSM-5 molecular sieve catalyst is 9.5~12 N / mm. The binder is a mixture of boehmite and alumina, and the mass ratio of the boehmite to the alumina is 3~5:7~10.

2. The method for preparing the HZSM-5 molecular sieve catalyst according to claim 1, characterized in that, The amount of acidic sites in the HZSM-5 molecular sieve catalyst is 0.02~0.03 mmol / g; and / or, the specific surface area of ​​the HZSM-5 molecular sieve catalyst is 325~340 m². 2 / g; and / or, the porosity of the HZSM-5 molecular sieve catalyst is 45%~55%; and / or, the average pore size of the HZSM-5 molecular sieve catalyst is 3.5~4.5nm.

3. The preparation method according to claim 1, characterized in that, The mass concentration of the nitric acid aqueous solution is 3.5~5wt%.

4. The preparation method according to claim 1, characterized in that, The HZSM-5 molecular sieve has a silica-to-alumina ratio of 300-500:1; and / or, the HZSM-5 molecular sieve has a particle size of 250-300 mesh; and / or, the binder has a particle size of 450-500 mesh.

5. The preparation method according to claim 4, characterized in that, The particle size ratio of the binder to the particle size of the HZSM-5 molecular sieve is 46~48:26~28.

6. The preparation method according to claim 1, characterized in that, The pore-expanding agent is guar gum powder, and the dynamic viscosity of the guar gum powder is 2000~3000 cP; and / or, the extrusion aid is selected from any one or more of glycerol, polyacrylamide and silicone resin.

7. The preparation method according to claim 6, characterized in that, The extrusion aid is glycerin.

8. The preparation method according to claim 1, characterized in that, The drying temperature is 60~80℃; and / or the drying time is 4~8h.

9. The preparation method according to claim 1, characterized in that, The calcination temperature is 500~550℃; and / or the calcination time is 6~8h.

10. The application of an HZSM-5 molecular sieve catalyst prepared by any one of claims 1 to 9 in the catalytic reaction of methanol to propylene.

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