A hierarchical pore self-supporting lamellar ZSM-5 molecular sieve and its preparation method and application

Abstract

The present invention belongs to the technical field of catalyst preparation, especially in the field of catalysts for catalytic cracking of olefins to produce propylene and ethylene. Specifically disclosed are a preparation method of a template agent, a hierarchical pore self-supporting sheet-like ZSM-5 molecular sieve, a preparation method of the ZSM-5 molecular sieve, and an application thereof. The hierarchical pore self-supporting sheet-like ZSM-5 molecular sieve of the present invention uses ZSM-5 seeds as nuclei, and ordered mutually supporting nanosheets with a thickness of 2-10 nm are formed on the surface of the ZSM-5 seeds. The nanosheets are stacked on top of each other along the B-axis direction, and there is a mesoporous structure of about 3 nm between the nanosheets. Due to the existence of the self-supporting structure, the hierarchical pore self-supporting sheet-like ZSM-5 molecular sieve has good thermal stability, and even after long-term use, it can still retain good catalytic performance. The present invention uses inexpensive raw materials to prepare the template agent, reducing the cost of producing the hierarchical pore self-supporting sheet-like ZSM-5 molecular sieve, which is conducive to large-scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, especially the field of catalysts for catalytic cracking of olefins to produce propylene and ethylene. Specifically, it relates to a preparation method of a template agent, a hierarchical pore self-supporting lamellar ZSM-5 molecular sieve, a preparation method of the ZSM-5 molecular sieve, and applications thereof. Background Art

[0002] With the gradual depletion of crude oil worldwide, the raw material oils required by the chemical industry show a trend of becoming heavier and of lower quality. The dependence of refineries in China on imported raw material oils is very high. Therefore, the processing of heavy and inferior crude oils is an important technical issue in the refining process.

[0003] The ZSM-5 molecular sieve has a regular pore structure, abundant acidic sites, and good hydrothermal stability, showing excellent catalytic activity, shape selectivity, and good anti-coking performance. However, there are serious diffusion resistances in the micropores of the ZSM-5 molecular sieve, making it difficult to handle heavy and inferior raw material oils and resulting in low catalytic activity.

[0004] Lamellar molecular sieves combine the advantages of strong acidity and high stability of microporous molecular sieves and strong mass transfer ability of mesoporous molecular sieves. They can increase the diffusion rates of reactants and products, thereby improving catalytic activity. However, the template agents used for lamellar ZSM-5 molecular sieves are expensive, and the layered structure has poor thermal stability and will be damaged after high-temperature calcination, making it difficult for industrial applications. Summary of the Invention

[0005] One object of the present invention is to provide a preparation method of a template agent, effectively solving the problem of the high price of the template agent used for preparing lamellar ZSM-5 molecular sieves.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A preparation method of a template agent, comprising the following steps:

[0008] (1) Mix a certain amount of 1-bromododecane and N,N,N'N'-tetramethyl-1,6-hexanediamine in an organic solvent, and react at 75 - 85 °C to obtain a mixture I. Separate and purify the mixture I to obtain an intermediate product.

[0009] (2) Mix the intermediate product with a certain amount of 1-bromohexane in an organic solvent, and react at 75 - 85 °C to obtain a mixture II. Separate and purify the mixture II to obtain the template agent C 12 H 25 -N + Br-C6H 12 -N + Br-C6H 13。

[0010] Preferably, in step (1), the molar ratio of 1-bromododecane to N,N,N',N'-tetramethyl-1,6-hexanediamine is 1:(11-15), and in step (2), the molar ratio of the intermediate product to 1-bromohexane is 1:(1.1-2.5).

[0011] Preferably, in step (1), the method for separating and purifying the mixture I is as follows: the reacted mixture I is cooled to room temperature, then dichloromethane is added for extraction, and the lower layer liquid is collected after stratification; then, the lower layer liquid is cooled to about 0 °C and allowed to stand and precipitate for 2 hours; finally, the solid precipitate is separated and dried at 60-80 °C to obtain the intermediate product.

[0012] Preferably, in step (2), the method for separating and purifying the mixture II is as follows: the reacted mixture II is cooled to room temperature, then dichloromethane is added for extraction, and the lower layer liquid is collected after stratification; then, the lower layer liquid is cooled to about 0 °C and allowed to stand and precipitate for 2 hours; finally, the solid precipitate is separated and dried at 60-80 °C to obtain the template agent.

[0013] The second object of the present invention is to provide a preparation method of a hierarchical pore self-supporting lamellar ZSM-5 molecular sieve, effectively solving the problem of poor thermal stability of the layered structure of the existing lamellar ZSM-5 molecular sieve.

[0014] To solve the above technical problems, the technical solution adopted by the present invention is:

[0015] A preparation method of a hierarchical pore self-supporting lamellar ZSM-5 molecular sieve, comprising the following steps:

[0016] (1) Mix ZSM-5 seeds, an alkali source solution and a template agent prepared by the preparation method as described in the above examples at room temperature to form a mixed solution A;

[0017] (2) Mix an aluminum source solution and an acidic solution to form a mixed solution B;

[0018] (3) Under the condition of 60-75 °C, add the mixed solution B to the mixed solution A to form a mixed solution C, and the pH value of the mixed solution C is 9-12;

[0019] (4) Under the condition of 55-65 °C, add a silicon source to the mixed solution C to obtain a gel, and the gel is hydrothermally crystallized at 150 °C - 170 °C. After crystallization, a solid substance is obtained, and after washing, drying and calcination of the solid substance, a hierarchical pore self-supporting lamellar ZSM-5 molecular sieve is obtained.

[0020] Further, the molar ratio of the template agent to alumina is (6 - 15):1, the mass ratio of the ZSM-5 seed crystals to silica is (0.5 - 1.5):1, and the molar ratio of silica in the silicon source to alumina in the aluminum source is (100 - 200):1.

[0021] Further, the molar ratio of silicon element in the silicon source to aluminum element in the aluminum source is (60 - 100):1.

[0022] Further, the molar ratio of each substance in the gel in step (4) is:

[0023] M2O:Al2O3:SiO2:C 12-6-6 Br2:H2SO4:H2O = 30:1:(100 - 200):10:18:4000, where M is the element in the base source.

[0024] source.

[0025] Further, the aluminum source includes aluminum sulfate and / or aluminum isopropoxide, the acidic solution includes sulfuric acid, the silicon source includes tetraethyl orthosilicate and / or silica sol, and the base source includes sodium hydroxide.

[0026] Further, the pH value of the mixed solution A is 10 - 12.

[0027] The third object of the present invention is to provide a hierarchical pore self-supporting lamellar ZSM-5 molecular sieve, which effectively solves the problem of poor thermal stability of the layered structure of the existing lamellar ZSM-5 molecular sieve.

[0028] A hierarchical pore self-supporting lamellar ZSM-5 molecular sieve prepared by the preparation method as described in the above embodiment, with the ZSM-5 seed crystals as the core, forming an ordered and mutually supporting nano-sheet layer with a thickness of 2 - 10 nm on the surface of the ZSM-5 seed crystals. The nano-sheet layers are stacked on top of each other along the B-axis direction, and there is a mesoporous structure of about 3 nm between the nano-sheet layers.

[0029] The fourth object of the present invention is to provide an application of the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve as described in the above embodiment in the reaction system of olefin catalytic cracking to prepare ethylene and propylene.

[0030] The beneficial technical effects of the present invention are:

[0031] (1) The present invention uses inexpensive raw materials to prepare a template agent, reducing the cost of producing lamellar ZSM-5 molecular sieve and facilitating large-scale industrial production. Moreover, during the preparation process of the template agent of the present invention, dichloromethane is selected as the extractant after each reaction step, and the extract is separated and purified by low-temperature cooling and multiple suction filtration. The obtained template agent has high purification purity. When used as the template agent for preparing lamellar ZSM-5 molecular sieve, lamellar ZSM-5 molecular sieve with better performance can be obtained.

[0032] (2) The hierarchical pore self-supporting lamellar ZSM-5 molecular sieve of the present invention has a self-supporting lamellar structure with regular structure and complete crystal form. In particular, even in the case of a relatively low silicon-aluminum ratio, a hierarchical pore self-supporting lamellar ZSM-5 molecular sieve with a complete crystal form and a lamellar structure can be obtained.

[0033] (3) The hierarchical pore self-supporting lamellar ZSM-5 molecular sieve of the present invention has a large specific surface area and the hierarchical pores are interconnected in series, significantly reducing the diffusion resistance of reactants on the molecular sieve, increasing the accessibility of acid sites, and greatly improving the reaction ability of the molecular sieve. In addition, the mutually supporting layered structure significantly enhances the thermal stability of the molecular sieve, avoiding the collapse of the layered structure under high-temperature conditions, and still retaining good catalytic performance even after long-term use. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0035] Figure 1 is the XRD pattern of the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve prepared in Example 3 of the present invention;

[0036] Figure 2 is the scanning electron microscope (SEM) image of the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve prepared in Example 3 of the present invention;

[0037] Figure 3 is the transmission electron microscope (TEM) image of the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve prepared in Example 3 of the present invention;

[0038] Figure 4 is the N2 physical adsorption and desorption isotherm diagram of the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve prepared in Example 3 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] Embodiment 1

[0040] A method for preparing a template agent, comprising the following steps:

[0041] (1) Mix a certain amount of 1-bromododecane and N,N,N',N'-tetramethyl-1,6-hexanediamine in an organic solvent, which can be toluene. React at 75 - 85 °C for 6 - 7 hours to obtain mixture I, and separate and purify mixture I to obtain an intermediate product. Among them, the molar ratio of 1-bromododecane to N,N,N',N'-tetramethyl-1,6-hexanediamine is 1:(11 - 15).

[0042] (2) Mix the intermediate product with a certain amount of 1-bromohexane in an organic solvent, and react at 75 - 85 °C for 6 - 7 hours to obtain mixture II. After separating and purifying mixture II, template agent C is obtained. 12 H 25 -N + Br-C6H 12 -N + Br-C6H 13 . Among them, the molar ratio of the intermediate product to 1-bromohexane is 1:(1.1 - 2.5).

[0043] The chemical reaction equation for the preparation process of the template agent is:

[0044]

[0045] In some embodiments, in step (1), the method for separating and purifying mixture I is: cool the reacted mixture I to room temperature, then add dichloromethane for extraction, and collect the lower layer liquid after stratification; then, cool the lower layer liquid to about 0 °C and let it stand for precipitation for 2 hours at about 0 °C; finally, separate the solid precipitate and dry it at 60 - 80 °C to obtain the intermediate product.

[0046] In some embodiments, in step (2), the method for separating and purifying mixture II is: cool the reacted mixture II to room temperature, then add dichloromethane for extraction, and collect the lower layer liquid after stratification; then, cool the lower layer liquid to about 0 °C and let it stand for precipitation for 2 hours at about 0 °C; finally, separate the solid precipitate and dry it at 60 - 80 °C to obtain the template agent.

[0047] The present invention uses inexpensive raw materials to prepare the template agent, reduces the cost of producing lamellar ZSM-5 molecular sieve, and is beneficial to large-scale industrial production. Moreover, during the preparation process of the template agent, dichloromethane is selected as the extraction agent after each step of the reaction, and the extraction liquid is separated and purified by low-temperature cooling and multiple filtration, and the obtained template agent has a high purification purity. Using it as the template agent for preparing lamellar ZSM-5 molecular sieve can obtain lamellar ZSM-5 molecular sieve with better performance.

[0048] Embodiment 2

[0049] A preparation method of hierarchical pore self-supporting lamellar ZSM-5 molecular sieve, comprising the following steps:

[0050] (1) Mix ZSM-5 seeds, an alkali source solution and the template agent prepared by the preparation method described in Embodiment 1 at room temperature to form a mixed solution A, and the pH value of the mixed solution A is 10-12. Among them, the room temperature is 25-30°C, and the alkali source includes sodium hydroxide.

[0051] The preparation method of the ZSM-5 seeds is as follows: Dissolve tetrapropylammonium hydroxide in deionized water, stir at a temperature of 25-35°C for 0.5-1 h, then slowly add tetraethyl orthosilicate and stir at a temperature of 50-70°C for 24 h, and finally hydrothermally crystallize at 80°C for 1 day to obtain ZSM-5 seeds.

[0052] (2) Mix an aluminum source solution and an acidic solution to form a mixed solution B. Among them, the aluminum source includes aluminum sulfate and / or aluminum isopropoxide, and the acidic solution includes sulfuric acid.

[0053] (3) Under the condition of 60-75°C, add the mixed solution B to the mixed solution A to form a mixed solution C, and the pH value of the mixed solution C is 9-12.

[0054] By adding the mixed solution B to the mixed solution A and controlling the pH value at 9-12, the aluminum source can be fully hydrolyzed without agglomeration. In addition, it is also convenient to mix with the silicon source, and the dissolution-formation rate of the aluminosilicate is well controlled, so that the aluminosilicate crystallizes better and the crystallinity of the ZSM-5 molecular sieve is improved.

[0055] (4) Under the condition of 55-65°C, add a silicon source to the mixed solution C to obtain a gel. The silicon source includes tetraethyl orthosilicate and / or silica sol, and the molar ratio of each substance in the gel is: M2O:Al2O3:SiO2:C 12-6-6 Br2:H2SO4:H2O = 30:1:(100-200):10:18:4000, where M is the element in the alkali source, such as Na, K, etc.

[0056] The gel is hydrothermally crystallized at 150°C - 170°C, and after crystallization, a solid substance is obtained. The solid substance is washed, dried at 80-120°C, and calcined at 500-600°C to obtain the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve.

[0057] In some embodiments, the molar ratio of the template agent to aluminum oxide is (6 - 15):1, the mass ratio of the ZSM-5 seed crystals to silicon dioxide is (0.5 - 1.5):1, and the molar ratio of silicon dioxide in the silicon source to aluminum oxide in the aluminum source is (100 - 200):1.

[0058] In some embodiments, the molar ratio of silicon element in the silicon source to aluminum element in the aluminum source is (60 - 100):1.

[0059] In some embodiments, the calcination temperature in step (4) is 550 °C.

[0060] During the preparation process, using the ZSM-5 seed crystals as the core, under the action of the template agent, aluminosilicate forms mutually supporting nanosheet layers with a thickness of 2 - 10 nanometers on the surface of the ZSM-5 seed crystals, and there is a mesoporous structure of about 3 nanometers between the nanosheet layers.

[0061] The hierarchical pore self-supporting sheet-like ZSM-5 molecular sieve of the present invention is self-assembled by the interaction between the amphiphilic cationic template agent C 12-6-6 and the inorganic substance through the free assembly of Br2. The prepared hierarchical pore self-supporting sheet-like ZSM-5 molecular sieve has a large specific surface area, and the hierarchical pores are interconnected in series with each other, which can give full play to their respective diffusion characteristics, significantly reduce the diffusion resistance of the reactants on the molecular sieve, increase the accessibility of the acidic sites, and greatly improve the reaction ability of the molecular sieve. The mutually supporting layered structure significantly improves the thermal stability of the molecular sieve, avoids the collapse of the layered structure under high-temperature conditions, and has a significant effect in the conversion reaction of C4 olefins.

[0062] At the same time, because the sheet layer thickness of the hierarchical pore self-supporting sheet-like ZSM-5 molecular sieve is only 2 - 10 nanometers, the diffusion path is shortened, the occurrence of secondary reactions is reduced, the formation of coke is inhibited, and the service life of the molecular sieve is increased. Therefore, the self-supporting sheet-like ZSM-5 molecular sieve of the present invention has good thermal stability and can maintain good catalytic performance even after long-term use.

[0063] Embodiment 3

[0064] Application of the hierarchical pore self-supporting sheet-like ZSM-5 molecular sieve described in Embodiment 2 in the reaction system for catalytic cracking of olefins to prepare ethylene and propylene.

[0065] First, disperse the hierarchical pore self-supporting sheet-like ZSM-5 molecular sieve in 1 mol / L NH4Cl solution for ammonium exchange. After the ammonium exchange is completed, then calcine the sample to obtain the H-type hierarchical pore self-supporting sheet-like ZSM-5 molecular sieve.

[0066] Then, using the H-type hierarchical pore self-supporting lamellar ZSM-5 molecular sieve as a catalyst, catalytic cracking of the raw material olefins is carried out to produce propylene and ethylene, and the catalytic cracking reaction is carried out at a temperature of 500-600°C. The raw material olefins are C4 olefins.

[0067] The present invention will be further described below in conjunction with the drawings, examples, experimental examples and comparative examples.

[0068] The methods and equipment for detecting the structural properties of molecular sieves involved in the following examples are:

[0069] XRD analysis of the sample was determined using an X’Pert PRO MPD diffractometer produced by Panalytical Company in the Netherlands. Its light source is Cu target Kα radiation, the tube voltage is 40 kV, the tube current is 40 mA, the scanning step size is 0.0167, and the diffraction pattern is recorded in the range of 2θ from 5° to 75°.

[0070] SEM analysis of the sample was carried out on a S-4800 type scanning electron microscope produced by Hitachi Company in Japan, with a magnification of 30-800,000 times and an accelerating voltage of 0.5-30 kV.

[0071] TEM analysis of the sample was carried out on a JEM-2100UHR transmission electron microscope produced by JEOL Company in Japan, with an accelerating voltage of 200 kV. The sample was first ultrasonically dispersed in 1 mL of ethanol, and then dropped on a copper mesh for testing. The average particle size analysis is to count the sizes of no less than 200 particles in a random area on the image.

[0072] The N2 adsorption-desorption experiment of the sample was carried out on an ASAP 2460 physical adsorption instrument produced by Micromeritics Company. Before the test, the sample was degassed and pretreated at 300°C for 6 h, and then the adsorption-desorption isotherm was measured at -196.15°C with high-purity nitrogen as the adsorption medium.

[0073] All the technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of this technology. Except for the specific methods, equipment, and materials used in the examples, those skilled in the art of this technology can also use any methods, equipment, and materials of the prior art similar to or equivalent to the methods, equipment, and materials described in the examples of the present invention to implement the present invention according to their mastery of the prior art and the description of the present invention.

[0074] The reagents used in the examples of the present invention are all of chemical pure grade.

[0075] Example 1

[0076] This example is a preparation method of ZSM-5 seeds.

[0077] (1) Dissolve 1 g of tetrapropylammonium hydroxide (mass concentration 20%) in 15 g of deionized water, and stir for 0.5 h at 25 °C to prepare solution A.

[0078] (2) Add 2.4 g of tetraethyl orthosilicate to solution A, stir at 70 °C for 24 h, and then hydrothermally crystallize at 80 °C for 1 day to obtain ZSM-5 seeds.

[0079] Example 2

[0080] This example is for template C 12 H 25 -N + Br-C6H 12 -N + Br-C6H 13 (C 12-6-6 Br2) preparation method.

[0081] (1) Mix 1.32 g of 1-bromododecane and 11 g of N,N,N’N’-tetramethyl-1,6-hexanediamine in a mixed solution of 50 ml of acetonitrile and toluene to prepare solution A.

[0082] (2) Heat solution A at 80 °C for 6 hours to obtain mixture I. After cooling mixture I to room temperature, add dichloromethane for extraction, and collect the lower layer liquid I after layering.

[0083] (3) Let the lower layer liquid I stand at 0 °C for 2 hours to form a precipitate. Filter and separate the solid precipitate, and dry it at 75 °C to obtain the intermediate C.

[0084] (4) Dissolve 3.51 g of intermediate C and 2.21 g of 1-bromohexane in 32 ml of acetonitrile to form solution D.

[0085] (5) Heat solution D at 80 °C for 6 hours to obtain mixture II. After cooling mixture II to room temperature, add dichloromethane for extraction, and collect the lower layer liquid II after layering.

[0086] (6) Let the lower layer liquid II stand at 0 °C for 2 hours to form a precipitate. Filter and separate the solid precipitate, and dry it at 75 °C to obtain template C 12 H 25 -N + Br-C6H 12 -N + Br-C6H 13 .

[0087] Example 3

[0088] This example uses the ZSM-5 seeds prepared in Example 1 and the template agent prepared in Example 2 to prepare hierarchical pore self-supporting lamellar ZSM-5 molecular sieve.

[0089] (1) Dissolve 1.33 g of sodium hydroxide (0.03 mol) and 10 g of ZSM-5 seeds in 20 g of deionized water to form solution A; add 2.01 g of the template agent to solution A and stir at 25 °C for 0.5 h to form solution B.

[0090] (2) Add 1 g of concentrated sulfuric acid (0.01 mol) to 20 g of deionized water to form solution C.

[0091] (3) Dissolve 0.19 g of aluminum sulfate (0.0006 mol) in solution C and stir evenly at room temperature to form solution D.

[0092] (4) Slowly add solution D to solution B and quickly stir at 70 °C for 1 h to form solution E.

[0093] (5) Add 11.06 g of tetraethyl orthosilicate (0.04 mol) to solution E, quickly stir at 70 °C for 1 h to form a reaction mixture, and then hydrothermally crystallize at 150 °C for 7 days to obtain a solid sample.

[0094] (6) Wash the solid sample with a large amount of water, dry it at 80 - 120 °C for 12 h, and then calcine it in a muffle furnace at 550 °C for 6 h to obtain the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve.

[0095] Perform XRD, SEM, TEM, and BET analyses on the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve prepared in Example 3.

[0096] X-ray diffraction characterization is as Figure 1 shown. It can be seen from Figure 1 that there is a set of doublets between 2θ = 3 - 8°, and another set of doublets also appears between 2θ = 22 - 26°, which conforms to the MFI structure characteristics and there are no impurity peaks, indicating that the synthesized sample is ZSM-5 molecular sieve.

[0097] Scanning electron microscopy characterization is as Figure 2 shown. It can be concluded from Figure 2 that the molecular sieve is composed of mutually supported nanosheet layers stacked in a pine needle shape.

[0098] Transmission electron microscopy characterization is as Figure 3 shown. It can be concluded from Figure 3 that the lamellar structures are stacked on top of each other along the B-axis direction, and the nanosheet molecular sieve is composed of 2-nm-thick sheets supported by each other in an orderly manner. The B-axis is the (010) crystal plane.

[0099] The N2 physical adsorption and desorption curve is as shown in Figure 4 and it can be concluded from Figure 4 that there is an adsorption hysteresis loop in the image, and the structure reflected by this image is generally flaky particulate material with a certain mesoporous structure.

[0100] Example 4

[0101] In this example, the ZSM-5 seeds prepared in Example 1 and the template agent prepared in Example 2 are used to prepare hierarchical pore self-supporting lamellar ZSM-5 molecular sieve.

[0102] (1) Dissolve 1.33 g of sodium hydroxide (0.03 mol) and 10 g of ZSM-5 seeds in 20 g of deionized water to form solution A. Add 2.01 g of the template agent to solution A and stir at 25 °C for 1 h to form solution B.

[0103] (2) Add 1 g of concentrated sulfuric acid (0.01 mol) to 20 g of deionized water to form solution C.

[0104] (3) Dissolve 0.37 g of aluminum sulfate (0.001 mol) in solution C and stir evenly at room temperature to form solution D.

[0105] (4) Slowly add solution D to solution B and stir rapidly at 70 °C for 2 h to form solution E.

[0106] (5) Add 11.06 g of tetraethyl orthosilicate (0.04 mol) to solution E, stir rapidly at 70 °C for 2 h to form a reaction mixture, and then hydrothermally crystallize at 150 °C for 7 days to obtain a solid sample.

[0107] (6) Wash the solid sample with a large amount of water, dry it at 80 - 120 °C for 12 h, and then calcine it in a muffle furnace at 550 °C for 6 h to obtain the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve.

[0108] Experimental Example 1

[0109] The as-prepared hierarchical pore self-supporting lamellar ZSM-5 molecular sieve (Si / Al = 200) obtained in Example 3 is pressed into tablets under 20 Mpa after ammonium exchange, screened for 20 - 40 mesh particles, and subjected to a 20-hour reaction evaluation in a micro fixed-bed reactor.

[0110] The reaction raw material is 1-butene, the reaction temperature is 600 °C, the reaction pressure is 0.1 MPa, and the reaction space velocity is 10 h -1 . After 20 h, the conversion rate of the raw material 1-butene drops from 96.0% to 93.5%; the yield of propylene has been maintained above 31% and gradually increases; the yield of ethylene shows a slow downward trend as a whole. The raw material conversion rate and the yields of the main products (propylene, ethylene) are shown in Table 1.

[0111] Table 1 Yields of Main Products and Conversion Rates of Raw Materials over Reaction Time

[0112]

[0113]

[0114] Experimental Example 2

[0115] The as - synthesized powder of hierarchical porous self - supported lamellar ZSM - 5 zeolite (Si / Al = 100) prepared in Example 4 after ammonium exchange was pressed into tablets at 20 MPa, and the 20 - 40 mesh particles were screened and subjected to reaction evaluation in a micro - fixed - bed reactor for 20 hours.

[0116] The reaction raw materials were 1 - butene, the reaction temperature was 550 °C, the pressure was 0.1 MPa, and the space velocity was 10 h−1. -1 . After 20 hours, the conversion rate of raw material 1 - butene decreased from 95.3% to 93.9%; the yield of the main product propylene remained at about 31% all the time; the yield of ethylene showed a slow downward trend as a whole. The conversion rate of raw materials and the yields of main products (propylene, ethylene) are shown in Table 2.

[0117] Table 2 Yields of Main Products and Conversion Rates of Raw Materials over Reaction Time

[0118]

[0119]

[0120] It can be seen from the data in Table 1 and Table 2 that the hierarchical porous self - supported lamellar ZSM - 5 zeolite prepared by the present invention has good thermal stability in the reaction system for olefin cracking to prepare ethylene and propylene. After continuous operation for 20 hours, the decrease in the conversion rate of 1 - butene is very small, indicating that the catalytic performance of the hierarchical porous self - supported lamellar ZSM - 5 zeolite decreases very little and the service life of the catalyst is long.

[0121] Comparative Example 1

[0122] A commercial ZSM - 5 zeolite (Si / Al = 200) was used as the catalyst for reaction evaluation in a micro - fixed - bed reactor. The reaction raw materials were 1 - butene, the reaction temperature was 600 °C, the reaction pressure was 0.1 MPa, and the reaction space velocity was 10 h−1. -1 . After 6 hours, the conversion rate of raw material 1 - butene decreased from 94.5% to 86.9%; the yield of the main product propylene decreased from 32.7% to 26.0%; the yield of ethylene decreased from 17.9% to 6.3%. The reaction data of the conversion rate of raw materials and the yields of main products (propylene, ethylene) are shown in Table 3.

[0123] Table 3 Yields of Main Products and Conversion Rates of Raw Materials over Reaction Time

[0124] Reaction time (h) 1-Butene conversion rate (%) Propylene yield (%) Ethylene yield (%) 1 94.44 32.65 17.91 2 91.80 32.14 11.80 3 91.06 31.13 11.13 4 89.97 29.82 9.38 5 88.28 25.94 6.36 6 86.84 26.41 6.24

[0125] As can be seen from the data in Table 3, when using commercial ZSM-5 molecular sieve (Si / Al = 200) as the catalyst in the reaction system for olefin cracking to prepare ethylene and propylene, the conversion rate of raw materials and the yields of products decrease significantly.

[0126] Based on Table 1, Table 2 and Table 3 comprehensively, it can be concluded that the hierarchically porous self-supporting lamellar ZSM-5 molecular sieve prepared in the present invention has good thermal stability in the reaction system for olefin cracking to prepare ethylene and propylene. Compared with the reaction system using commercial ZSM-5 molecular sieve as the catalyst, the conversion rate of raw materials increases, and the selectivities of ethylene and propylene increase.

[0127] Certainly, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the substantial scope of the present invention shall also fall within the protection scope of the present invention.

Claims

1. Application of a hierarchical pore self-supporting lamellar ZSM-5 molecular sieve in an olefin catalytic cracking reaction system for preparing ethylene and propylene, characterized in that, The preparation method of the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve includes: (1) Mix the ZSM-5 seed crystal, the alkali source solution and the template agent C 12 H 25 -N + Br-C6H 12 -N + Br-C6H 13 at room temperature to form a mixed solution A; the pH value of the mixed solution A is 10 to 12; (2) Mix the aluminum source solution with the acidic solution to form a mixed solution B; (3) Under the condition of 60 - 75 °C, add the mixed solution B to the mixed solution A to form a mixed solution C, and the pH value of the mixed solution C is 9 - 12; (4) Under the condition of 55 - 65 °C, add the silicon source to the mixed solution C to obtain a gel, and the gel is hydrothermally crystallized at 150 °C - 170 °C. After crystallization, a solid substance is obtained. The solid substance is washed, dried, and calcined to obtain the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve; Among them, the preparation method of the ZSM-5 seed crystal is: dissolve tetrapropylammonium hydroxide in deionized water, stir for 0.5 - 1 h under the condition of a temperature of 25 - 35 °C, then add tetraethyl orthosilicate and stir for 24 h under the condition of a temperature of 50 - 70 °C, and finally hydrothermally crystallize at 80 °C for 1 day to obtain the ZSM-5 seed crystal; The molar ratio of silica in the silicon source to alumina in the aluminum source is (100 - 200):1, and the template agent C 12 H 25 -N + Br-C6H 12 -N + Br-C6H 13 The molar ratio of it to alumina is (6 - 15):1, and the mass ratio of ZSM-5 seed crystals to silica is (0.5 - 1.5):1; The template agent C 12 H 25 -N + Br-C6H 12 -N + Br-C6H 13 The preparation method comprises the following steps: S1. Mix a certain amount of 1-bromododecane and N,N,N',N'-tetramethyl-1,6-hexanediamine in an organic solvent, react at 75 - 85 °C to obtain a mixture I, and separate and purify the mixture I to obtain an intermediate product; S2. The intermediate product is mixed with a certain amount of 1-bromohexane in an organic solvent and reacted at 75-85 °C to obtain mixture II. After separating and purifying mixture II, the template agent C is obtained. 12 H 25 -N + Br-C6H 12 -N + Br-C6H 13 ; The molar ratio of the 1-bromododecane to the N,N,N',N'-tetramethyl-1,6-hexanediamine is 1:(11 - 15), and the molar ratio of the intermediate product to 1-bromohexane is 1:(1.1 - 2.5); Using the ZSM-5 seed crystal as the core, ordered mutually supporting nanosheets with a thickness of 2 - 10 nm are formed on the surface of the ZSM-5 seed crystal. The nanosheets are stacked on top of each other along the B-axis direction, and there is a mesoporous structure of about 3 nm between the nanosheets.

2. Use of the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve according to claim 1 in the reaction system for catalytic pyrolysis of olefins to prepare ethylene and propylene, characterized in that, The molar ratio of the silicon element in the silicon source to the aluminum element in the aluminum source is (60 - 100):

1.

3. Use of the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve according to claim 2 in an olefin catalytic cracking reaction system for preparing ethylene and propylene, characterized in that The molar ratio of each substance in the gel described in step (4) is: M2O:Al2O3:SiO2:C 12-6-6 Br2:H2SO4:H2O = 30:1:(100 - 200):10:18:4000, where M is the element in the base source.

4. Use of the hierarchical pore self-supporting lamellar ZSM-5 molecular sieve according to claim 3 in the reaction system for catalytic cracking of olefins to prepare ethylene and propylene, characterized in that, The aluminum source includes aluminum sulfate and / or aluminum isopropoxide, the acidic solution includes sulfuric acid, the silicon source includes tetraethyl orthosilicate and / or silica sol, and the base source includes sodium hydroxide.

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