Preparation method and application of hierarchical pore aluminum-rich ZSM-5 zeolite

Abstract

The preparation method comprises the following steps: dissolving an aluminum source, sodium hydroxide and tetrapropylammonium hydroxide in deionized water, stirring until the solution is clear, dropwise adding a silicon source into the solution, uniformly stirring to obtain silicon-aluminum gel, transferring the silicon-aluminum gel into a reaction kettle, carrying out hydrothermal crystallization, filtering, washing and drying to obtain the hierarchical porous aluminum-rich ZSM-5 zeolite. And washing, filtering, drying and roasting the obtained product, and carrying out ammonium ion exchange to obtain the multi-defect aluminum-rich ZSM-5 zeolite. The method comprises the following steps: dispersing multi-defect site aluminum-rich ZSM-5 zeolite in a sodium hydroxide or potassium hydroxide solution, and carrying out ultrasonic alkali treatment; the product after alkali treatment is subjected to ammonium ion exchange, and is finally roasted, so that the hierarchical pore aluminum-rich ZSM-5 zeolite with the silicon-aluminum atomic ratio of less than 20 can be obtained, and the hierarchical pore aluminum-rich ZSM-5 zeolite contains rich mesoporous structures, can expose more acidic sites, and shows excellent catalytic performance as a 1, 3, 5-triisopropylbenzene cracking catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic materials, and particularly relates to a preparation method and application of hierarchical pore-rich aluminum ZSM-5 zeolite. Background Art

[0002] ZSM-5 zeolite has a relatively high specific surface area, good water and thermal stability, and excellent shape selectivity, and is an important catalyst or catalyst support in the fields of petrochemical industry, fine chemical industry, etc. The silicon-aluminum ratio is an important factor affecting the performance of ZSM-5. Hierarchical pore-rich aluminum ZSM-5 zeolite (with a silicon-aluminum atomic ratio less than 20) can provide more acidic sites due to its higher aluminum content, and has great application potential in industries such as petroleum cracking, biomass conversion, and plastic degradation.

[0003] Traditional microporous rich-aluminum ZSM-5 zeolite only contains a microporous structure with a relatively small pore size. Most of the acidic sites are located inside the micropores, and large reaction molecules are difficult to access these sites, resulting in insufficient ability to catalytically convert large molecules. At the same time, the relatively small micropore size also hinders the diffusion of large product molecules in the pores, resulting in large mass transfer resistance and thus reducing the stability of the catalyst.

[0004] Existing methods for preparing hierarchical pore-rich aluminum ZSM-5 zeolite include hard template method, soft template method, acid or steam treatment method, etc. The hard template method and the soft template method require the use of expensive mesoporous templating agents, which not only have high production costs, but also are prone to environmental pollution when removing the mesoporous templating agents. Acid treatment or steam treatment has high equipment requirements, complex operations, and will cause great damage to the crystallinity of the zeolite, affecting its thermal and hydrothermal stability, so large-scale industrial applications are limited.

[0005] Compared with the above methods, alkali treatment for desilication to prepare hierarchical pore zeolite has the advantages of high cost-effectiveness, low equipment requirements, low pollution, simple operation, etc., which is beneficial to industrial applications. However, the conventional alkali treatment method is restricted by the silicon-aluminum ratio of the zeolite and can only treat zeolites with a silicon-aluminum atomic ratio greater than 25 into hierarchical pore zeolites, and cannot be directly used to prepare hierarchical pore-rich aluminum ZSM-5 zeolite.

[0006] Therefore, developing a method for preparing hierarchical pore-rich aluminum ZSM-5 zeolite by alkali treatment to break through the limitation of the silicon-aluminum ratio on the alkali treatment method is helpful to develop the alkali treatment technology and promote the industrial application of hierarchical pore-rich aluminum zeolite, which has important practical significance. Summary of the Invention

[0007] To solve the above technical problems, the present invention provides a method for preparing hierarchical pore aluminosilicate ZSM-5 zeolite. First, by finely regulating the raw material composition, aluminosilicate ZSM-5 zeolite rich in defect sites is prepared; then, under ultrasonic water bath conditions, it is treated with sodium hydroxide or potassium hydroxide solution to selectively dissolve the defect sites in the aluminosilicate ZSM-5 zeolite, forming a mesoporous structure, thus successfully preparing hierarchical pore aluminosilicate ZSM-5 zeolite.

[0008] The present invention also provides the application of the hierarchical pore aluminosilicate ZSM-5 zeolite prepared by the preparation method described in the present invention as a catalyst for the cracking of 1,3,5-triisopropylbenzene.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing hierarchical pore aluminosilicate ZSM-5 zeolite, the preparation method comprising the following steps:

[0011] (1) Dissolve an aluminum source, sodium hydroxide and tetrapropylammonium hydroxide in deionized water, stir until clear, dropwise add a silicon source thereto, stir evenly to obtain a silica-alumina gel, transfer the silica-alumina gel to a reaction kettle for hydrothermal crystallization, wash, filter, dry and calcine the obtained product, and then perform ammonium ion exchange to obtain aluminosilicate ZSM-5 zeolite with multiple defect sites;

[0012] (2) Disperse the aluminosilicate ZSM-5 zeolite with multiple defect sites obtained in step (1) in sodium hydroxide or potassium hydroxide solution for ultrasonic alkali treatment;

[0013] (3) Perform ammonium ion exchange on the product after alkali treatment, and finally calcine to obtain hierarchical pore aluminosilicate ZSM-5 zeolite with a silicon-aluminum atomic ratio less than 20;

[0014] In step (1), in the silica-alumina gel, the molar ratio of Al2O3:Na2O:SiO2 is 1:1.1 - 2.3:25 - 40.

[0015] In step (1), the conditions for hydrothermal crystallization are reaction at 150 - 190 °C for 2 - 3 days; the calcination conditions are calcination at 500 - 600 °C for 4 - 7 h.

[0016] In step (1), the aluminum source is any one or more of alumina or aluminum powder.

[0017] In step (1), the silicon source is any one or more of silica sol or fumed silica.

[0018] In step (1), in the silica-alumina gel, the molar ratio of each component is Al2O3:Na2O:SiO2:TPAOH:H2O = 1:1.1 - 2.3:25 - 40:3 - 5:650 - 900.

[0019] In step (2), the concentration of the sodium hydroxide or potassium hydroxide solution is 0.15 - 0.25 mol / L.

[0020] In step (2), the conditions for ultrasonic alkali treatment are as follows: alkali treatment is carried out under the condition of an ultrasonic water bath with an ultrasonic power density of 0.5 - 0.75 W / cm 2 , a frequency of 20 - 40 kHz, and a water bath temperature of 30 - 50 °C, and the treatment time is 0.2 - 2 h.

[0021] In steps (1) and (3), the ammonium ion exchange process is as follows: the substance to be subjected to ammonium ion exchange is dispersed in a 0.8 - 1.3 mol / L ammonium chloride solution, stirred at 55 - 65 °C for 1.5 - 2.5 h, centrifuged, and the above process is repeated three times, and then washed and dried.

[0022] In step (3), the calcination conditions are calcination at 500 - 600 °C for 3 - 5 h.

[0023] The solid-liquid ratio during alkali treatment and ammonium ion exchange is both 1 g: 25 - 35 mL.

[0024] The preparation method of the hierarchical pore-rich aluminum ZSM-5 zeolite provided by the present invention uses tetrapropylammonium hydroxide as a template agent.

[0025] The raw material composition is finely adjusted so that Al2O3:Na2O:SiO2:TPAOH:H2O = 1:1.1 - 2.3:25 - 40:3 - 5:650 - 900 in the silica sol, and a defect-site-rich aluminum ZSM-5 zeolite is prepared through hydrothermal crystallization, calcination, and ammonium ion exchange; then, it is treated with a sodium hydroxide or potassium hydroxide solution under the condition of an ultrasonic water bath to selectively dissolve the defect sites in the aluminum-rich ZSM-5 zeolite to form a mesoporous structure, thereby successfully preparing a hierarchical pore-rich aluminum ZSM-5 zeolite with a silica-alumina ratio of less than 20.

[0026] The hierarchical pore-rich aluminum ZSM-5 zeolite prepared by the present invention contains a rich mesoporous structure, can expose more acidic sites, shorten the diffusion path, and in catalytic reactions involving macromolecules, such as petroleum cracking, biomass conversion, etc., the hierarchical pore-rich aluminum ZSM-5 zeolite can better meet the adsorption and diffusion requirements of macromolecules, and thus exhibits significantly better catalytic activity and longer catalytic life than traditional ZSM-5 zeolite.

[0027] Compared with the prior art, it has the following advantages:

[0028] (1) Avoid using a mesoporous template agent, reducing production costs and also avoiding environmental pollution caused by removing the mesoporous template agent;

[0029] (2) Avoid using acid or steam treatment, thus avoiding corrosion of equipment, reducing equipment costs, and being conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 XRD patterns of ZSM-5 zeolites prepared in Example 1, Example 2, Example 3, Example 4, Comparative Example 1, Comparative Example 2, and Comparative Example 3;

[0031] Figure 2 N2 adsorption-desorption isotherms of ZSM-5 zeolites prepared in Example 1, Example 2, Example 3, Example 4, Comparative Example 1, and Comparative Example 2;

[0032] Figure 3 BJH pore size distribution curves of ZSM-5 zeolites prepared in Example 1, Example 2, Example 3, Example 4, Comparative Example 1, and Comparative Example 2;

[0033] Figure 4 Transmission electron microscope image of the ZSM-5 zeolite prepared in Example 1;

[0034] Figure 5 Transmission electron microscope image of the ZSM-5 zeolite prepared in Comparative Example 1;

[0035] Figure 6 Graph showing the change in the conversion rate of 1,3,5-triisopropylbenzene catalyzed by ZSM-5 zeolites prepared in Example 1, Example 2, Example 3, Example 4, Comparative Example 1, and Comparative Example 2 over time. DETAILED DESCRIPTION OF THE INVENTION

[0036] The present invention will be described in detail below in conjunction with the examples.

[0037] Example 1

[0038] A method for preparing a hierarchical pore aluminosilicate ZSM-5 zeolite, comprising the following steps:

[0039] (1) Using aluminum powder as the aluminum source, tetrapropylammonium hydroxide as the template agent, and silica sol as the silicon source. Weigh the aluminum source, sodium hydroxide, and tetrapropylammonium hydroxide in a beaker according to the molar ratio of Al2O3:Na2O:SiO2:TPAOH:H2O = 1:2.0:32:3.3:709, dissolve them with deionized water and stir until clear, then gradually add the silicon source dropwise and stir evenly to obtain a synthesis gel. Transfer the synthesis gel to an autogenous pressure reactor for hydrothermal crystallization, with a crystallization temperature of 180 °C and a crystallization time of 2 days. Wash the obtained product with distilled water until neutral, filter, dry, then calcine it in a muffle furnace at 520 °C in air for 7 hours, and then mix it with 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry to obtain aluminum-rich ZSM-5 zeolite with multiple defect sites.

[0040] (2) Disperse the aluminum-rich ZSM-5 zeolite with multiple defect sites obtained in step (1) in a sodium hydroxide solution with a concentration of 0.2 mol / L at a solid-liquid ratio of 1 g:30 mL, and perform alkali treatment under ultrasonic bath conditions with an ultrasonic power density of 0.75 W / cm 2 , a frequency of 40 kHz, and a water bath temperature of 50 °C for 0.5 h. After filtration, washing with water, and drying, an alkali-treated product is obtained.

[0041] (3) Mix the alkali-treated product with 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 55 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry, then calcine it in a muffle furnace at 560 °C for 3.5 hours to obtain hierarchical pore aluminum-rich ZSM-5 zeolite.

[0042] The XRD pattern of the sample obtained in Example 1 is as Figure 1 shown, indicating that it is a ZSM-5 zeolite with high crystallinity and no other impurity crystals are formed; XRF test shows that its silicon-aluminum atomic ratio is 11.8; the nitrogen adsorption-desorption isotherm is as Figure 2 shown, indicating the presence of an obvious hysteresis loop, indicating that in addition to the microporous structure, it also contains a rich mesoporous structure; the BJH pore size distribution curve is as Figure 3 shown, indicating that its mesopore diameter is concentrated around 10 nm; the transmission electron micrograph is as Figure 4 shown, further indicating the presence of a rich mesoporous structure in its crystal.

[0043] Example 2

[0044] A preparation method of hierarchical pore aluminum-rich ZSM-5 zeolite, comprising the following steps:

[0045] (1) Using alumina as the aluminum source, tetrapropylammonium hydroxide as the template agent, and fumed silica as the silicon source. Weigh the aluminum source, sodium hydroxide, and tetrapropylammonium hydroxide in a beaker according to the molar ratio of Al2O3:Na2O:SiO2:TPAOH:H2O = 1:1.1:30:3.2:690, dissolve them with deionized water and stir until clear, then gradually add the silicon source dropwise and stir evenly to obtain a synthesis gel. Transfer the synthesis gel to an autogenous pressure reactor for hydrothermal crystallization at a crystallization temperature of 150 °C for 3 days. Wash the obtained product with distilled water until neutral, filter, dry, then calcine it in a muffle furnace at 540 °C in air for 6 hours, and then mix it with 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry to obtain aluminum-rich ZSM-5 zeolite with multiple defect sites.

[0046] (2) Disperse the aluminum-rich ZSM-5 zeolite with multiple defect sites obtained in step (1) in a sodium hydroxide solution with a concentration of 0.17 mol / L at a solid-liquid ratio of 1 g:25 mL, and perform alkali treatment under ultrasonic bath conditions with an ultrasonic power density of 0.6 W / cm 2 , a frequency of 30 kHz, and a water bath temperature of 45 °C for 1 h. After filtration, washing with water, and drying, an alkali-treated product is obtained.

[0047] (3) Mix the alkali-treated product with 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry, then calcine it in a muffle furnace at 580 °C for 3 hours to obtain hierarchical pore aluminum-rich ZSM-5 zeolite.

[0048] The XRD pattern of the sample obtained in Example 2 is as Figure 1 shown, indicating that it is a ZSM-5 zeolite with high crystallinity and no other impurity crystals are formed; XRF test shows that its silicon-aluminum atomic ratio is 12.5; the nitrogen adsorption-desorption isotherm is as Figure 2 shown, indicating the presence of an obvious hysteresis loop, indicating that it contains a rich mesoporous structure in addition to the microporous structure; the BJH pore size distribution curve is as Figure 3 shown, indicating that its mesopore diameter is concentrated around 10 nm.

[0049] Example 3

[0050] A method for preparing hierarchical pore aluminum-rich ZSM-5 zeolite, comprising the following steps:

[0051] (1) Using aluminum powder as the aluminum source, tetrapropylammonium hydroxide as the template agent, and silica sol as the silicon source. Weigh the aluminum source, sodium hydroxide, and tetrapropylammonium hydroxide in a beaker according to the molar ratio of Al2O3:Na2O:SiO2:TPAOH:H2O = 1:2.0:35:4.0:712. Dissolve them with deionized water and stir until clear. Then, gradually add the silicon source dropwise and stir evenly to obtain a synthetic gel. Transfer the synthetic gel to an autogenous pressure reactor for hydrothermal crystallization at a crystallization temperature of 190 °C for 2 days. Wash the obtained product with distilled water until neutral, filter, dry, and then calcine it in a muffle furnace at 600 °C in air for 4 hours. Then, mix it with a 1.2 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:25 mL, stir in a constant temperature water bath at 55 °C for 2.5 h, centrifuge, repeat the above process 3 times, wash with water, and dry to obtain aluminum-rich ZSM-5 zeolite with multiple defect sites.

[0052] (2) Disperse the aluminum-rich ZSM-5 zeolite with multiple defect sites obtained in step (1) in a sodium hydroxide solution with a concentration of 0.15 mol / L at a solid-liquid ratio of 1 g:30 mL, and perform alkali treatment under ultrasonic bath conditions with an ultrasonic power density of 0.75 W / cm 2 , a frequency of 20 kHz, and a water bath temperature of 35 °C for 2 h. After filtration, washing with water, and drying, an alkali-treated product is obtained.

[0053] (3) Mix the alkali-treated product with a 1.2 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:25 mL, stir in a constant temperature water bath at 55 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry. Then, calcine it in a muffle furnace at 590 °C for 3 hours to obtain hierarchical pore aluminum-rich ZSM-5 zeolite.

[0054] The XRD pattern of the sample obtained in Example 3 is as Figure 1 shown, indicating that it is a ZSM-5 zeolite with high crystallinity and no other impurity crystals are formed; XRF test shows that its silicon-aluminum atomic ratio is 10.5; the nitrogen adsorption-desorption isotherm is as Figure 2 shown, indicating the presence of an obvious hysteresis loop, indicating that it contains a rich mesoporous structure in addition to the microporous structure; the BJH pore size distribution curve is as Figure 3 shown, indicating that its mesopore diameter is concentrated around 10 nm.

[0055] Example 4

[0056] A method for preparing hierarchical pore aluminum-rich ZSM-5 zeolite, comprising the following steps:

[0057] (1) Using aluminum powder as the aluminum source, tetrapropylammonium hydroxide as the template agent, and fumed silica as the silicon source. Weigh the aluminum source, sodium hydroxide, and tetrapropylammonium hydroxide in a beaker according to the molar ratio of Al2O3:Na2O:SiO2:TPAOH:H2O = 1:2.3:40:4.2:720. Dissolve them with deionized water and stir until clear. Then, slowly add the silicon source drop by drop and stir evenly to obtain a synthesis gel. Transfer the synthesis gel to an autogenous pressure reactor for hydrothermal crystallization at a crystallization temperature of 170 °C for 3 days. Wash the obtained product with distilled water until neutral, filter, dry, and then calcine it in a muffle furnace at 570 °C in air for 6 hours. Then, mix it with 0.8 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry to obtain aluminum-rich ZSM-5 zeolite with multiple defect sites.

[0058] (2) Disperse the aluminum-rich ZSM-5 zeolite with multiple defect sites obtained in step (1) in a sodium hydroxide solution with a concentration of 0.17 mol / L at a solid-liquid ratio of 1 g:35 mL, and perform alkali treatment under ultrasonic bath conditions with an ultrasonic power density of 0.6 W / cm 2 , a frequency of 30 kHz, and a water bath temperature of 45 °C for 1 h. After filtration, washing with water, and drying, an alkali-treated product is obtained.

[0059] (3) Mix the alkali-treated product with 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry. Then, calcine it in a muffle furnace at 580 °C for 3 hours to obtain hierarchical pore aluminum-rich ZSM-5 zeolite.

[0060] The XRD pattern of the sample obtained in Example 4 is as Figure 1 shown, indicating that it is a ZSM-5 zeolite with high crystallinity and no other impurity crystals are formed; XRF test shows that its silicon-aluminum atomic ratio is 13.6; the nitrogen adsorption-desorption isotherm is as Figure 2 shown, indicating the presence of an obvious hysteresis loop, indicating that in addition to the microporous structure, it also contains a rich mesoporous structure; the BJH pore size distribution curve is as Figure 3 shown, indicating that its mesopore diameter is concentrated around 10 nm.

[0061] Example 5

[0062] A preparation method of hierarchical pore aluminum-rich ZSM-5 zeolite, comprising the following steps:

[0063] (1) Aluminum powder was used as the aluminum source, tetrapropylammonium hydroxide was used as the template, and fumed silica was used as the silicon source. The aluminum source, sodium hydroxide, and tetrapropylammonium hydroxide were weighed into a beaker according to the molar ratio of Al2O3:Na2O:SiO2:TPAOH:H2O = 1:1.5:40:5.0:750, dissolved in deionized water and stirred until clear, and the silicon source was added dropwise and stirred evenly to obtain a synthetic gel. The synthetic gel was transferred to an autogenous pressure reactor for hydrothermal crystallization at a crystallization temperature of 180°C and a crystallization time of 2 days. The obtained product was washed with distilled water until neutral, filtered, dried, and then calcined in a muffle furnace at 550°C for 6 hours with air. It was then mixed with 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stirred in a constant temperature water bath at 60°C for 2 hours, centrifuged, and the above process was repeated 3 times. The product was washed with water and dried to obtain a multi-defect aluminum-rich ZSM-5 zeolite.

[0064] (2) The multi-defect aluminum-rich ZSM-5 zeolite obtained in step (1) was dispersed in a sodium hydroxide solution with a concentration of 0.2 mol / L at a solid-liquid ratio of 1 g:35 mL, and an ultrasonic power density of 0.5 W / cm 2 The product was treated with alkali under ultrasonic water bath conditions with a frequency of 30 kHz and a water bath temperature of 30°C for 2 h. The product was filtered, washed with water and dried to obtain an alkali-treated product.

[0065] (3) The alkali-treated product was mixed with 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stirred in a constant temperature water bath at 60°C for 2 h, centrifuged, and the above process was repeated 3 times. The mixture was washed with water, dried, and then calcined in a muffle furnace at 580°C for 3 h to obtain a hierarchical pore aluminum-rich ZSM-5 zeolite.

[0066] The XRD spectrum of the sample obtained in Example 5 is as follows: Figure 1 As shown, it is a high-crystallinity ZSM-5 zeolite without other impurity crystals; XRF test shows that its silicon-aluminum atomic ratio is 12.5; nitrogen adsorption-desorption isotherm is as shown Figure 2 As shown in the figure, there is an obvious hysteresis loop, indicating that it contains abundant mesoporous structure in addition to microporous structure; the BJH pore distribution curve is shown in the figure. Figure 3 As shown, it shows that the mesopore diameter is concentrated around 10 nm.

[0067] Example 6

[0068] A method for preparing a hierarchically porous aluminum-rich ZSM-5 zeolite comprises the following steps:

[0069] (1) Using alumina as the aluminum source, tetrapropylammonium hydroxide as the template agent, and silica sol as the silicon source. Weigh the aluminum source, sodium hydroxide, and tetrapropylammonium hydroxide in a beaker according to the molar ratio of Al2O3:Na2O:SiO2:TPAOH:H2O = 1:1.8:25:3.5:650. Dissolve them with deionized water and stir until clear. Then, gradually add the silicon source dropwise and stir evenly to obtain a synthetic gel. Transfer the synthetic gel to an autogenous pressure reactor for hydrothermal crystallization at a crystallization temperature of 160 °C for 3 days. Wash the obtained product with distilled water until neutral, filter, dry, and then calcine it in a muffle furnace at 560 °C for 5 hours in air. Then, mix it with a 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry to obtain aluminum-rich ZSM-5 zeolite with multiple defect sites.

[0070] (2) Disperse the aluminum-rich ZSM-5 zeolite with multiple defect sites obtained in step (1) in a sodium hydroxide solution with a concentration of 0.2 mol / L at a solid-liquid ratio of 1 g:25 mL, and perform alkali treatment under ultrasonic bath conditions with an ultrasonic power density of 0.5 W / cm 2 , a frequency of 20 kHz, and a water bath temperature of 35 °C for 1.5 h. After filtration, washing with water, and drying, an alkali-treated product is obtained.

[0071] (3) Mix the alkali-treated product with a 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry. Then, calcine it in a muffle furnace at 580 °C for 3.5 hours to obtain hierarchical pore aluminum-rich ZSM-5 zeolite.

[0072] The XRD pattern of the sample obtained in Example 6 shows that it is a ZSM-5 zeolite with high crystallinity and no other impurity crystals are formed; XRF test shows that its silicon-aluminum atomic ratio is 10.8; the nitrogen adsorption-desorption test results show that in addition to the microporous structure, it also contains a rich mesoporous structure.

[0073] Example 7

[0074] A preparation method of hierarchical pore aluminum-rich ZSM-5 zeolite, comprising the following steps:

[0075] (1) Using aluminum powder as the aluminum source, tetrapropylammonium hydroxide as the template agent, and silica sol as the silicon source. Weigh the aluminum source, sodium hydroxide, and tetrapropylammonium hydroxide in a beaker according to the molar ratio of Al2O3:Na2O:SiO2:TPAOH:H2O = 1:1.6:36:3.0:700, dissolve them with deionized water and stir until clear, then gradually add the silicon source dropwise and stir evenly to obtain a synthesis gel. Transfer the synthesis gel to an autogenous pressure reactor for hydrothermal crystallization at a crystallization temperature of 165 °C for 3 days. Wash the obtained product with distilled water until neutral, filter, dry, then calcine it in a muffle furnace at 580 °C for 5 hours in air, and then mix it with a 1.3 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:25 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry to obtain aluminum-rich ZSM-5 zeolite with multiple defect sites.

[0076] (2) Disperse the aluminum-rich ZSM-5 zeolite with multiple defect sites obtained in step (1) in a 0.25 mol / L sodium hydroxide solution at a solid-liquid ratio of 1 g:30 mL, and perform alkali treatment under ultrasonic bath conditions with an ultrasonic power density of 0.75 W / cm 2 , a frequency of 40 kHz, and a water bath temperature of 50 °C for 0.2 h. After filtration, washing with water, and drying, an alkali-treated product is obtained.

[0077] (3) Mix the alkali-treated product with a 1.3 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:25 mL, stir in a constant temperature water bath at 60 °C for 1.5 h, centrifuge, repeat the above process 3 times, wash with water, and dry, then calcine it in a muffle furnace at 600 °C for 3.5 hours to obtain hierarchical pore aluminum-rich ZSM-5 zeolite.

[0078] The XRD pattern of the sample obtained in Example 7 shows that it is a ZSM-5 zeolite with high crystallinity and no other impurity crystals are generated; XRF test shows that its silicon-aluminum atomic ratio is 14.3; the nitrogen adsorption-desorption test results show that it contains rich mesoporous structures in addition to the microporous structure.

[0079] Example 8

[0080] A preparation method of hierarchical pore aluminum-rich ZSM-5 zeolite, comprising the following steps:

[0081] (1) Using alumina as the aluminum source, tetrapropylammonium hydroxide as the template agent, and fumed silica as the silicon source. Weigh the aluminum source, sodium hydroxide, and tetrapropylammonium hydroxide in a beaker according to the molar ratio of Al2O3:Na2O:SiO2:TPAOH:H2O = 1:2.1:34:5.0:900, dissolve them with deionized water and stir until clear. Then, dropwise add the silicon source to it and stir evenly to obtain a synthesis gel. Transfer the synthesis gel to an autogenous pressure reactor for hydrothermal crystallization. The crystallization temperature is 155 °C and the crystallization time is 3 days. Wash the obtained product with distilled water until neutral, filter, dry, and then calcine it in a muffle furnace at 540 °C for 6 hours in air. Then, mix it with 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry to obtain aluminum-rich ZSM-5 zeolite with multiple defect sites.

[0082] (2) Disperse the aluminum-rich ZSM-5 zeolite with multiple defect sites obtained in step (1) in a sodium hydroxide solution with a concentration of 0.8 mol / L at a solid-liquid ratio of 1 g:35 mL, and perform alkali treatment under the ultrasonic water bath conditions of ultrasonic power density of 0.6 W / cm 2 , frequency of 30 kHz, and water bath temperature of 45 °C for 0.75 h. After filtration, washing with water, and drying, an alkali-treated product is obtained.

[0083] (3) Mix the alkali-treated product with 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry. Then, calcine it in a muffle furnace at 580 °C for 3 hours to obtain hierarchical pore aluminum-rich ZSM-5 zeolite.

[0084] The XRD pattern of the sample obtained in Example 8 shows that it is a ZSM-� zeolite with high crystallinity and no other impurity crystals are formed; XRF test shows that its silicon-aluminum atomic ratio is 13.0; the nitrogen adsorption-desorption test results show that it contains a rich mesoporous structure in addition to the microporous structure.

[0085] Example 9

[0086] A preparation method of hierarchical pore aluminum-rich ZSM-5 zeolite, comprising the following steps:

[0087] (1) Using a mixture of alumina and aluminum powder with equal mass ratio as the aluminum source, tetrapropylammonium hydroxide as the template agent, and silica sol as the silicon source. Weigh the aluminum source, sodium hydroxide, and tetrapropylammonium hydroxide in a beaker according to the molar ratio of Al2O3:Na2O:SiO2:TPAOH:H2O = 1:1.2:27:4.4:710. Dissolve them with deionized water and stir until clear. Then, gradually add the silicon source dropwise and stir evenly to obtain a synthetic gel. Transfer the synthetic gel to an autogenous pressure reactor for hydrothermal crystallization at a crystallization temperature of 190 °C for 2 days. Wash the obtained product with distilled water until neutral, filter, dry, then calcine it in a muffle furnace at 540 °C in air for 6 hours. Then, mix it with 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry to obtain aluminum-rich ZSM-5 zeolite with multiple defect sites.

[0088] (2) Disperse the aluminum-rich ZSM-5 zeolite with multiple defect sites obtained in step (1) in a sodium hydroxide solution with a concentration of 0.22 mol / L at a solid-liquid ratio of 1 g:35 mL, and perform alkali treatment under ultrasonic bath conditions with an ultrasonic power density of 0.65 W / cm 2 , a frequency of 25 kHz, and a water bath temperature of 30 °C for 1.5 h. After filtration, washing with water, and drying, an alkali-treated product is obtained.

[0089] (3) Mix the alkali-treated product with 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry. Then, calcine it in a muffle furnace at 580 °C for 3 hours to obtain hierarchical pore aluminum-rich ZSM-5 zeolite.

[0090] The XRD pattern of the sample obtained in Example 9 shows that it is a ZSM-5 zeolite with high crystallinity and no other impurity crystals are generated; XRF test shows that its silicon-aluminum atomic ratio is 11.2; the nitrogen adsorption-desorption test results show that it contains rich mesoporous structures in addition to microporous structures.

[0091] Example 10

[0092] A preparation method of hierarchical pore aluminum-rich ZSM-5 zeolite, comprising the following steps:

[0093] (1) Using aluminum powder as the aluminum source, tetrapropylammonium hydroxide as the template agent, and silica sol as the silicon source. Weigh the aluminum source, sodium hydroxide, and tetrapropylammonium hydroxide in a beaker according to the molar ratio of Al2O3:Na2O:SiO2:TPAOH:H2O = 1:1.5:27:4.4:850, dissolve them with deionized water and stir until clear, then gradually add the silicon source dropwise and stir evenly to obtain a synthesis gel. Transfer the synthesis gel to an autogenous pressure reactor for hydrothermal crystallization at a crystallization temperature of 175 °C and a crystallization time of 2 days. Wash the obtained product with distilled water until neutral, filter, dry, then calcine it in a muffle furnace at 540 °C for 6 hours in air, and then mix it with 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry to obtain aluminum-rich ZSM-5 zeolite with multiple defect sites.

[0094] (2) Disperse the aluminum-rich ZSM-5 zeolite with multiple defect sites obtained in step (1) in a sodium hydroxide solution with a concentration of 0.25 mol / L at a solid-liquid ratio of 1 g:30 mL, and perform alkali treatment under ultrasonic bath conditions with an ultrasonic power density of 0.75 W / cm 2 , a frequency of 30 kHz, and a water bath temperature of 35 °C for 1 h. After filtration, washing with water, and drying, an alkali-treated product is obtained.

[0095] (3) Mix the alkali-treated product with 1 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 60 °C for 2 h, centrifuge, repeat the above process 3 times, wash with water, and dry, then calcine it in a muffle furnace at 580 °C for 3 hours to obtain hierarchical pore aluminum-rich ZSM-5 zeolite.

[0096] The XRD pattern of the sample obtained in Example 10 shows that it is a ZSM-5 zeolite with high crystallinity and no other impurity crystals are generated; XRF test shows that its silicon-aluminum atomic ratio is 10.8; the nitrogen adsorption-desorption test results show that it contains rich mesoporous structures in addition to the microporous structure.

[0097] Comparative Example 1

[0098] A preparation method of aluminum-rich ZSM-5 zeolite, comprising the following steps:

[0099] Using aluminum powder as the aluminum source, tetrapropylammonium hydroxide as the template agent, and silica sol as the silicon source. Weigh the aluminum source, sodium hydroxide, and tetrapropylammonium hydroxide according to the molar ratio of Al2O3:Na2O:SiO2:TPAOH:H2O = 1:2.0:32:3.3:709 in a beaker, dissolve them with deionized water and stir until clear. Then, dropwise add the silicon source to it and stir evenly to obtain a synthetic gel. Transfer the synthetic gel to an autogenous pressure reactor for hydrothermal crystallization. The crystallization temperature is 180 °C and the crystallization time is 2 days. The obtained product is washed with distilled water until neutral, filtered, dried, and then calcined in a muffle furnace at 520 °C for 7 hours under air flow to obtain microporous aluminum-rich ZSM-5 zeolite.

[0100] The XRD pattern of the sample obtained in Comparative Example 1 is as Figure 1 shown, indicating that it is a ZSM-5 zeolite with high crystallinity and no other impurity crystals are formed; XRF test shows that its silica-alumina ratio is 12.7; the nitrogen adsorption-desorption isotherm is as Figure 2 shown, indicating that there is no hysteresis loop, indicating that it only contains microporous structure and no mesoporous structure; the BJH pore size distribution curve is as Figure 3 shown, indicating that there is no observable mesoporous distribution; the transmission electron microscope image is as Figure 5 shown, further indicating that there is no mesoporous structure in its crystal.

[0101] Comparative Example 2

[0102] Other conditions are the same as those in Example 1, except that the ultrasonic treatment process in step (2) is omitted, that is, step (2) is:

[0103] Disperse the multi-defect-site aluminum-rich ZSM-5 zeolite obtained in step (1) in a sodium hydroxide solution with a concentration of 0.2 mol / L at a solid-liquid ratio of 1 g:30 mL, stir in a constant temperature water bath at 50 °C for 0.5 h, filter, wash with water, and dry to obtain an alkali-treated product.

[0104] The XRD pattern of the sample obtained in Comparative Example 2 is as Figure 1 shown, indicating that it is a ZSM-5 zeolite with high crystallinity and no other impurity crystals are formed; XRF test shows that its silica-alumina ratio is 12.5; the nitrogen adsorption-desorption isotherm is as Figure 2 shown, indicating that the hysteresis loop is very small, indicating that it does not have an obvious mesoporous structure; the BJH pore size distribution curve is as Figure 3 shown, further indicating that it does not have an obvious mesoporous structure.

[0105] Comparative Example 3

[0106] Equally replace the tetrapropylammonium hydroxide template agent in Example 1 with tetrapropylammonium bromide template agent, and other conditions are the same as those in Example 1.

[0107] The XRD pattern of the sample obtained in Comparative Example 3 is as follows Figure 1 shown, indicating that it is not pure ZSM-5 zeolite and the sample contains mordenite intergrowth crystals.

[0108] Application Example

[0109] The catalytic performance of the hierarchical pore aluminosilicate ZSM-5 zeolites prepared in the Examples and Comparative Examples was evaluated by the catalytic cracking reaction of 1,3,5-triisopropylbenzene.

[0110] The prepared ZSM-5 zeolite was processed into catalyst particles with a size of 20-40 mesh. 0.2 g of the catalyst particles were loaded into a fixed-bed reactor with an inner diameter of 10 mm. 1,3,5-triisopropylbenzene was catalytically cracked at 400 °C and atmospheric pressure. The feed rate of the reactants was 2.4 mL / h, and N2 with a flow rate of 30 mL / min was used as the carrier gas. The composition of the products was analyzed online using a Fuli GC9790Ⅱ gas chromatograph equipped with an INNO-WAX capillary column, and the conversion rate of 1,3,5-triisopropylbenzene at different reaction times was measured. The results are as follows Figure 6 shown.

[0111] As can be seen from the figure, the initial conversion rates of the hierarchical pore aluminosilicate ZSM-5 zeolites prepared in Example 1, Example 2, Example 3, and Example 4 are significantly higher than those of the microporous aluminosilicate ZSM-5 zeolite prepared in Comparative Example 1, and the conversion rate is increased by about one time, indicating that the hierarchical pores improve the activity of ZSM-5 zeolite in catalytically converting macromolecules. In addition, compared with the microporous aluminosilicate ZSM-5 zeolite prepared in Comparative Example 1, the change of the conversion rate of the hierarchical pore aluminosilicate ZSM-5 zeolites prepared in Example 1, Example 2, Example 3, and Example 4 with time is slower, indicating that the hierarchical pore aluminosilicate ZSM-5 zeolite has better catalytic stability. However, compared with the microporous aluminosilicate ZSM-5 zeolite prepared in Comparative Example 1, the catalytic activity of the ZSM-5 zeolite prepared in Comparative Example 2 is only slightly improved, and the catalytic stability hardly changes, further indicating that an effective hierarchical pore structure cannot be obtained by using the method of Comparative Example 2.

[0112] The above detailed description of the preparation method and application of a hierarchical pore aluminosilicate ZSM-5 zeolite with reference to the Examples is illustrative rather than restrictive. Several Examples can be listed within the defined scope. Therefore, changes and modifications without departing from the general concept of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for preparing hierarchical pore-rich aluminum ZSM-5 zeolite, characterized in that, The preparation method comprises the following steps: (1) Dissolve an aluminum source, sodium hydroxide, and tetrapropylammonium hydroxide in deionized water, stir until clear, dropwise add a silicon source thereto, stir evenly to obtain a silica-alumina gel, transfer the silica-alumina gel to a reaction kettle for hydrothermal crystallization, wash, filter, dry, and calcine the obtained product, and then perform ammonium ion exchange to obtain multi-defect-site aluminum-rich ZSM-5 zeolite; (2) Disperse the multi-defect-site aluminum-rich ZSM-5 zeolite obtained in step (1) in a sodium hydroxide or potassium hydroxide solution, and perform ultrasonic alkali treatment; (3) Perform ammonium ion exchange on the product after alkali treatment, and finally calcine it to obtain hierarchical pore aluminum-rich ZSM-5 zeolite with a silica-aluminum atomic ratio less than 20; In step (1), in the silica-alumina gel, the molar ratio of Al2O3:Na2O:SiO2 is 1:1.1-2.3:25-40.

2. The preparation method of the hierarchical pore rich-aluminum ZSM-5 zeolite according to claim 1, characterized in that, In step (1), the conditions for hydrothermal crystallization are reaction at 150-190 °C for 2-3 days; the calcination conditions are calcination at 500-600 °C for 4-7 h.

3. The preparation method of the hierarchical pore aluminosilicate ZSM-5 zeolite according to claim 1, wherein, In step (1), the aluminum source is any one or more of alumina or aluminum powder.

4. The preparation method of the hierarchical pore rich-aluminum ZSM-5 zeolite according to claim 1, wherein, In step (1), the silicon source is any one or more of silica sol or fumed silica.

5. The preparation method of the hierarchical pore alumina-rich ZSM-5 zeolite according to any one of claims 1-5, characterized in that, In step (1), in the silica-alumina gel, the molar ratio of each component is Al2O3:Na2O:SiO2: TPAOH:H2O = 1:1.1-2.3:25-40:3-5:650-900.

6. The preparation method of the hierarchical pore-rich aluminum ZSM-5 zeolite according to any one of claims 1-5, characterized in that, In step (2), the concentration of the sodium hydroxide or potassium hydroxide solution is 0.15-0.25 mol / L.

7. The preparation method of the hierarchical pore-rich aluminous ZSM-5 zeolite according to any one of claims 1-5, characterized in that, In step (2), the conditions for ultrasonic alkali treatment are as follows: alkali treatment is carried out under the condition of ultrasonic water bath with ultrasonic power density of 0.5-0.75 W / cm 2 , frequency of 20-40 kHz, and water bath temperature of 30-50 °C, and the treatment time is 0.2-2 h.

8. The preparation method of the hierarchical pore aluminosilicate ZSM-5 zeolite according to claim 1, characterized in that, In steps (1) and (3), the process of ammonium ion exchange is as follows: Disperse the substance to be subjected to ammonium ion exchange in a 0.8-1.3 mol / L ammonium chloride solution, stir at 55-65 °C for 1.5-2.5 h, centrifuge, repeat the above process three times, and then wash and dry.

9. The preparation method of the hierarchical pore-rich aluminous ZSM-5 zeolite according to any one of claims 1-5, characterized in that, In step (3), the calcination conditions are calcination at 500-600 °C for 3-5 h.

10. Application of the hierarchical pore aluminum-rich ZSM-5 zeolite prepared by the preparation method according to any one of claims 1-9 as a catalyst for the cracking of 1,3,5-triisopropylbenzene.

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