Composite molecular sieve of MFI or beta-configuration molecular sieve and AEI-configuration molecular sieve as well as preparation method and application of composite molecular sieve

Abstract

The invention relates to a composite molecular sieve of an MFI or beta-configuration molecular sieve and an AEI-configuration molecular sieve, and a preparation method and application thereof. The preparation method of the composite molecular sieve comprises the following steps: providing a first molecular sieve containing a first template agent, and then preparing a second molecular sieve in the presence of a second template agent and the first molecular sieve containing the first template agent to obtain the composite molecular sieve, wherein the first template agent and the second template agent are different in chemical structure, the first molecule is selected from at least one of an MFI configuration molecular sieve and a beta configuration molecular sieve, and the second molecular sieve is an AEI configuration molecular sieve. The composite molecular sieve material provided by the invention is used as a catalyst, and has higher ethylene and propylene yields in the cracking reaction of C5-C10 n-alkanes and the catalytic cracking reaction of naphtha.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, specifically relating to a composite molecular sieve of MFI or beta molecular sieve and AEI molecular sieve, its manufacturing method and its application in catalytic cracking to olefins. Background Technology

[0002] Low-carbon olefins are important basic organic chemical raw materials. Currently, my country's low-carbon olefin production routes mainly rely on naphtha cracking, including steam cracking and catalytic cracking processes. Among these, compared to the energy-intensive and costly steam cracking, catalytic cracking technology lowers the reaction temperature, increases the range of usable feedstocks, allows for flexible control of product distribution, improves economic efficiency, and has a broader application prospect.

[0003] Catalytic cracking reactions mostly utilize molecular sieves as catalysts. The acidic active sites in the molecular sieve break down the feedstock into smaller molecules, and the micropores further shape-selectively generate target products such as ethylene and propylene. Commonly used molecular sieve catalysts include Y-type molecular sieves, β-molecular sieves, ZSM series molecular sieves, and SAPO series molecular sieves. However, single molecular sieve catalytic materials suffer from a limited pore size, resulting in a mismatch between acidic properties and pore structure. This restricts mass transfer between reactants and products within the molecular sieve pores, thus affecting catalyst lifespan and target product selectivity.

[0004] Studies have shown that composite molecular sieves prepared by combining two or more molecular sieves exhibit superior catalytic performance in catalytic cracking reactions compared to single molecular sieves. By harmonizing the acidity properties and pore structures of different molecular sieves in the composite molecular sieve, the pore confinement effect can be enhanced, thereby improving the reaction activity. For example, CN118289775A describes the preparation of a composite molecular sieve using Y-type molecular sieves as seed crystals, comprising 5–20 wt% high silica-to-alumina ratio Y-type molecular sieves and 20–60 wt% modified ZSM-5 molecular sieves. This composite molecular sieve utilizes two different acidic centers to convert hydrocarbons in crude oil into smaller hydrocarbon molecules, which are then cracked into target products such as ethylene and propylene. This composite molecular sieve possesses both strongly acidic active centers and a suitable hierarchical pore structure, enabling the efficient conversion of structurally different hydrocarbon molecules.

[0005] CN104549467A synthesized a Y / ZSM-5 catalytic cracking composite catalyst in situ, which can alleviate diffusion limitations and enhance adsorption, desorption capacity, and selectivity, thereby improving the catalytic cracking reaction activity and ethylene-propylene yield. Specifically, the naphtha conversion rate is 3-5% higher than that of catalysts prepared by existing technologies, and the diene yield is 2-5% higher.

[0006] CN101190418A describes the preparation of a ZSM-5 / mordenite composite molecular sieve using a template agent suitable for the synthesis of both ZSM-5 and mordenite. This sieve features small crystal size and large specific surface area, exhibiting high reactivity. Furthermore, its short intracrystalline pores prevent carbon deposition, resulting in good catalytic performance. The total yield of ethylene and propylene can reach 55.0%.

[0007] Most existing methods for preparing composite molecular sieves involve mechanical mixing or eutectic growth. While these methods effectively combine the properties of two molecular sieves, the pore structure still requires adjustment. Firstly, the two molecular sieves do not fully utilize their synergistic catalytic effect based on the diameter of the raw material molecules, effectively limiting the products to small molecule olefins such as ethylene and propylene. Secondly, the pores of the two molecular sieves are not connected to form a continuous pore structure, significantly limiting the diffusion efficiency between pores and weakening the confinement effect of the molecular sieve pores, making it easier to generate large molecular products or undergo secondary cracking reactions, increasing coking. Therefore, this invention synthesizes a composite molecular sieve material with a continuous pore structure. This continuous pore structure enhances the diffusion efficiency of reactants between different pores, reducing coking of reactants and consumption of low-carbon olefin products. Furthermore, it grows a second molecular sieve with a smaller pore size on the surface of the first molecular sieve material, which confines the pores of the main catalytic material, inhibiting the formation of large molecular products such as long-chain n-alkanes and aromatics, while increasing the contact time between hydrocarbon reactants and the active sites of the catalytic material, resulting in more conversion into small fragments (C4-). Applying this composite molecular sieve to catalytic cracking reactions can effectively improve reaction conversion and the yield of ethylene and propylene. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention discloses a method for preparing a composite molecular sieve material, wherein the composite molecular sieve is composed of a first molecular sieve and a second molecular sieve. This composite molecular sieve material has two different pore sizes and is interconnected, wherein the pore size of the second molecular sieve is smaller than that of the first molecular sieve.

[0009] According to a first embodiment of the present invention, a method for manufacturing a composite molecular sieve is provided, comprising the following steps: providing a first molecular sieve containing a first template agent (e.g., manufacturing the first molecular sieve containing the first template agent in the presence of the first template agent), and then manufacturing a second molecular sieve in the presence of a second template agent and the first molecular sieve containing the first template agent to obtain the composite molecular sieve, wherein the first template agent and the second template agent are chemically different, and the first molecular sieve is selected from at least one of MFI configuration molecular sieve and beta configuration molecular sieve (preferably selected from at least one of ZSM-5 molecular sieve and beta molecular sieve), and the second molecular sieve is an AEI configuration molecular sieve (preferably SAPO-18 molecular sieve).

[0010] According to a second embodiment of the present invention, a composite molecular sieve is provided, comprising a first molecular sieve and a second molecular sieve covering the surface of the first molecular sieve, wherein the first molecular sieve is selected from at least one of MFI configuration molecular sieve and beta configuration molecular sieve (preferably selected from at least one of ZSM-5 molecular sieve and beta molecular sieve), the second molecular sieve is an AEI configuration molecular sieve (preferably SAPO-18 molecular sieve), and the mass ratio of the first molecular sieve to the second molecular sieve is (60-99):1, preferably (70-99):1.

[0011] According to a third embodiment of the present invention, a catalytic cracking catalyst is obtained by ion exchange treatment of the composite molecular sieve of the present invention.

[0012] According to a fourth embodiment of the present invention, a catalytic cracking method is provided, comprising catalytic cracking of C in the presence of the catalytic cracking catalyst of the present invention. 5-10 n-Alkanes or naphtha to produce C 2-4 The steps of olefins.

[0013] Technical effect

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] The composite molecular sieve material disclosed in this invention is composed of two molecular sieves with different pore sizes, and the channels are interconnected. The small-pore molecular sieve layer inhibits the diffusion of large molecular products such as long-chain n-alkanes and aromatics out of the catalyst, keeping them within the internal large-pore molecular sieve channels. This increases the contact time between reactants and active sites, maximizing their conversion into fragments below C4. The interconnected channel structure helps improve the diffusion efficiency of reactant molecules, reduces secondary cracking reactions, and increases the yield of low-carbon olefins. Using the aforementioned composite molecular sieve material as a catalyst, in the C5-C... 10 It has higher yields of ethylene and propylene in the cracking reactions of n-alkanes and naphtha-catalyzed cracking reactions. Attached Figure Description

[0016] Figure 1 This is the XRD pattern of the composite molecular sieve in Example 1 of the present invention.

[0017] Figure 2 This is the XRD pattern of the composite molecular sieve after light grinding in Example 1 of the present invention.

[0018] Figure 3 These are the pore size distribution diagrams of the Beta molecular sieve and the composite molecular sieve in Example 1 of the present invention.

[0019] Figure 4The results are TEM characterization results of the composite molecular sieve synthesized in Example 1 of this invention. Detailed Implementation

[0020] The specific embodiments of the present invention will be described in detail below. However, it should be noted that the scope of protection of the present invention is not limited to these specific embodiments, but is determined by the claims in the appendix.

[0021] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0022] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0023] In the context of this invention, all numerical values ​​of parameters (e.g., quantity or condition) should be understood to be modified by the term “about” in all cases, regardless of whether “about” actually appears before the numerical value.

[0024] In the context of this invention, "substantially" means that deviations that are acceptable or reasonable to those skilled in the art are permitted, such as deviations within ±2%, ±1%, ±0.5%, or ±0.1%.

[0025] In the context of this invention, the XRD spectrum is measured using a D / max-2500 fully automatic rotating target X-ray diffractometer. The experimental conditions are: Cu target, Kα radiation source, operating voltage 40kV, and tube current 80mA.

[0026] In the context of this invention, the method for measuring the composite structure formed by the first molecular sieve and the second molecular sieve is to use a JEM-2100 high-resolution transmission electron microscope from JEOL Corporation of Japan.

[0027] In the context of this invention, the average thickness of the second molecular sieve is measured using a JEM-2100 high-resolution transmission electron microscope from JEOL Corporation of Japan.

[0028] In the context of this invention, the type of the second molecular sieve is determined by XRD analysis of the powder obtained after lightly grinding the composite molecular sieve and sieving it. Specifically, the light grinding is performed by dry grinding using a mortar and pestle. To facilitate the detachment of the second molecular sieve from the surface of the carrier (first molecular sieve), the entire grinding process is conducted under relatively gentle conditions. The ground composite molecular sieve is then sieved through a mesh of 160 or finer, and the resulting powder (with a higher concentration of the second molecular sieve) is subjected to XRD analysis.

[0029] In the context of this invention, the pore size distribution is measured using an ASAP 2460 physical adsorption instrument via N2 adsorption-desorption method. Before measurement, the sample is activated by vacuuming at 300°C for 4 hours, and the pore size distribution is analyzed using a DFT model.

[0030] In the context of this invention, the average particle size is measured according to GB / T 6288-2021 Method for Determination of Particle Size of Granular Molecular Sieve.

[0031] In the context of this invention, the specific surface area, pore volume, and pore size are measured using an ASAP 2460 physical adsorption instrument via N2 adsorption-desorption method. Before measurement, the sample is activated by vacuuming at 300°C for 4 hours. The specific surface area of ​​the sample is calculated using the BET method, the pore volume is calculated using the BJH model, and the pore size distribution is analyzed using the DFT model.

[0032] In the context of this invention, the template agent content is measured by thermogravimetric analysis, and the weight loss at a temperature above 200°C until the weight loss curve stabilizes is taken as the template agent content of the molecular sieve.

[0033] In the context of this invention, the free water content is measured using a halogen moisture analyzer at a test temperature of 120°C for 10 minutes.

[0034] In the context of this invention, the template agent loss rate is measured by thermogravimetric analysis. The weight loss at temperatures above 200°C until the weight loss curve stabilizes is the template agent content. The template agent loss rate is calculated as: (template agent content in the molecular sieve before washing - template agent content in the molecular sieve after washing) / template agent content in the molecular sieve before washing * 100%.

[0035] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this instruction manual are based on weight.

[0036] In the context of this invention, any two or more embodiments or aspects of this invention can be arbitrarily combined, and the resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of this invention.

[0037] According to one aspect of the present invention, a method for manufacturing a composite molecular sieve is disclosed, comprising the following steps:

[0038] 1) Provide a first molecular sieve containing a first template agent (e.g., manufacture the first molecular sieve containing the first template agent in the presence of the first template agent), then

[0039] 2) A second molecular sieve is manufactured in the presence of a second template agent and a first molecular sieve containing a first template agent to obtain the composite molecular sieve.

[0040] According to the present invention, "then" means that step 2) must be performed after step 1). Specifically, the second molecular sieve is manufactured only after the first molecular sieve containing the first template agent is manufactured according to step 1). Therefore, according to the present invention, the first molecular sieve containing the first template agent and the second molecular sieve are not manufactured simultaneously. As a case of simultaneous manufacturing, for example, the first molecular sieve and the second molecular sieve can be manufactured simultaneously in the presence of the first template agent and the second template agent.

[0041] According to one aspect of the present invention, the first molecular sieve is selected from at least one of MFI-type molecular sieves and beta-type molecular sieves (preferably selected from at least one of ZSM-5 molecular sieves and beta molecular sieves), and the second molecular sieve is an AEI-type molecular sieve (preferably SAPO-18 molecular sieve). The inventors of the present invention have discovered that the first molecular sieve needs to have abundant acidic sites and a large pore size structure to allow the pyrolysis reaction to occur sufficiently therein; the pore size of the second molecular sieve is similar to the molecular dynamic diameter of ethylene and propylene and smaller than that of the first molecular sieve, allowing C4 and smaller products such as ethylene and propylene to diffuse outward, thus achieving a confinement effect on C4 and larger products.

[0042] According to one aspect of the present invention, in step 1), a silicon source, an aluminum source, an alkali source, and water are also present. The molar ratio of the silicon source: the aluminum source: the alkali source: the first template agent R: water is SiO2:Al2O3:OH. - :R:H2O=1:0.01-0.1:0.02-2:0.03-2:5-60 (preferably SiO2:Al2O3:OH) - :R:H20=1:0.01-0.05:0.02-2:0.03-2:5-60).

[0043] According to one aspect of the present invention, in step 2), a silicon source, an aluminum source, a phosphorus source, and water are also present. The molar ratio of the silicon source: the aluminum source: the phosphorus source: the second template agent D: water is SiO2:Al2O3:P2O5:D:H2O = 0.01-2:1:0.1-2:0.5-5:20-100 (preferably SiO2:Al2O3:P2O5:D:H2O = 0.03-1:1:0.5-1.5:1-3:20-100).

[0044] According to one aspect of the present invention, the mass ratio of the first molecular sieve containing the first template agent to the silicon source, aluminum source, and phosphorus source in step 2) is (55-99):1, preferably (65-99):1. The inventors of the present invention have found that if the content of the second molecular sieve is too high, it will lead to a decrease in product diffusion efficiency, resulting in a secondary pyrolysis reaction; if it is too low, it will not be able to play a confinement role, leading to an increase in the yield of C4 and above products and a decrease in the yield of ethylene and propylene.

[0045] According to one aspect of the invention, the content of the first template agent is 20-70 wt% (preferably 30-60 wt%), based on 100 wt% of the total weight of the first molecular sieve containing the first template agent.

[0046] According to one aspect of the present invention, the average particle size of the first molecular sieve containing the first template agent is 85% or more passing through 60 mesh, preferably 90% or more passing through 100 mesh. The inventors of the present invention have discovered that excessively large molecular sieve particles reduce the specific surface area and the number of pores, leading to the aggregation and growth of the second molecular sieve, affecting its dispersion degree, and resulting in a decrease in catalytic activity.

[0047] According to one aspect of the present invention, the free water content of the first molecular sieve containing the first template agent is no more than 10 wt%, preferably no more than 5 wt%. The inventors of the present invention have found that a low free water content can ensure the particle dispersion of the first molecular sieve. If the water content is too high, it will cause the dispersibility of the first molecular sieve to decrease, resulting in a viscous state, which will affect the growth of the second molecular sieve on its surface.

[0048] According to one aspect of the present invention, after the first molecular sieve containing the first template agent is washed twice with deionized water at room temperature, the loss rate of the first template agent is less than 10 wt% (preferably less than 5 wt% or less than 2 wt%). The inventors of the present invention have discovered that the first template agent is substantially entirely embedded within the pores of the first molecular sieve during its manufacturing process, and the interaction between the agent and the first molecular sieve is not simply physical adsorption or physical mixing; therefore, the washing loss rate is very small.

[0049] According to one aspect of the invention, the first template agent and the second template agent are chemically different. Preferably, the first template agent and the second template agent have similar polarities and can form hydrogen bonds to each other in the presence of water. The inventors of the invention have discovered that the similar polarities of the first and second template agents attract each other, and both template agents contain nitrogen-containing functional groups, which bond to each other through hydrogen bonds. The two bonded template agents self-assemble to form a composite template agent, which, after secondary crystallization, yields a dual-microporous material with different crystal phases. This composite template agent "coats" the confined AEI-configured molecular sieve precursor onto the surface of the main MFI or Beta-configured molecular sieve while maintaining the unobstructed flow of the "variable-diameter composite pores," thus effectively opening the pores of the resulting composite molecular sieve.

[0050] According to the present invention, "similar polarity" means that the first template agent and the second template agent have a small difference in molecular polarity. Specifically, if the two template agent molecules contain the same type and similar number of polar functional groups and the polar functional groups are relatively symmetrically positioned in the molecules, especially ammonium groups or substituted ammonium groups, or if the two template agents are mutually soluble or have a small difference in solubility in the same solvent (e.g., less than 20%), then they can be considered to have a small difference in molecular polarity.

[0051] The inventors of this invention have discovered that the first template agent and the second template agent have similar polarities, which attracts them to each other. Furthermore, if both template agents contain nitrogen-containing functional groups, the two template agents can bond with each other after forming hydrogen bonds through the nitrogen-containing functional groups.

[0052] According to one aspect of the present invention, the first template agent can be used to synthesize the first molecular sieve. Specifically, the first template agent is selected from at least one of ethylenediamine, triethanolamine, tetrapropylammonium hydroxide, n-butylamine, ethylamine, 1,6-hexanediamine, tripropylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, tetraethylammonium fluoride, triethylamine, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, polyvinyl alcohol, and sodium carboxymethyl cellulose, preferably selected from at least one of ethylenediamine and triethanolamine.

[0053] According to one aspect of the invention, the second template agent can be used to synthesize the second molecular sieve. Specifically, the second template agent is selected from at least one of N,N-diisopropylethylamine, tetraethylammonium hydroxide, triethylamine, and N,N-methyl-3,5-dimethylpiperidine, preferably N,N-diisopropylethylamine.

[0054] According to the present invention, step 1) includes the following steps:

[0055] 1-1) A first mixture is formed by mixing a silicon source, an aluminum source, an alkali source, a first template agent, and water.

[0056] 1-2) Crystallize the first mixture to generate the first molecular sieve containing the first template agent.

[0057] 1-3) Separate the first molecular sieve containing the first template agent (preferably, optionally after filtration, dry (especially spray dry) the first molecular sieve containing the first template agent).

[0058] According to one aspect of the invention, there is no particular limitation on the silicon source, which can be any silicon source conventionally used in the manufacture of molecular sieves in the art, such as one or more of silica sol, silica fume, water glass and organosilicone esters, preferably silica sol.

[0059] According to one aspect of the invention, there is no particular limitation on the aluminum source, which can be any aluminum source conventionally used in the manufacture of molecular sieves in the art. Specifically, one or more of sodium aluminate, aluminum hydroxide, boehmite, aluminum isopropoxide, aluminum sulfate and aluminum chloride can be cited, with sodium aluminate and boehmite being preferred.

[0060] According to one aspect of the invention, there is no particular limitation on the phosphorus source, which can be any phosphorus source conventionally used in the manufacture of molecular sieves in the art, such as one or more of phosphoric acid, phosphorous acid, hypophosphoric acid, ammonium phosphate, ammonium monohydrogen phosphate and ammonium dihydrogen phosphate, preferably phosphoric acid.

[0061] According to one aspect of the invention, there is no particular limitation on the alkali source, which can be any alkali source conventionally used in the manufacture of molecular sieves in the art, such as sodium hydroxide or potassium hydroxide, preferably sodium hydroxide.

[0062] According to one aspect of the present invention, in step 1-2), the crystallization conditions include: crystallization pressure from atmospheric pressure to system autogenous pressure, presence or absence of seed crystals, crystallization temperature of 130-220°C (preferably 150-180°C), and crystallization time of 24-96h (preferably 48-96h).

[0063] According to one aspect of the invention, in steps 1-3), the drying conditions include: a drying temperature of 60-120°C (preferably 65-110°C) and a drying time of 5-20 hours (preferably 8-15 hours). Preferably, the spray drying conditions include: a solid content of 35-65%, an inlet air temperature of 150-250°C, an outlet air temperature of 80-150°C, and an air velocity of 300-1500 m / s. 3 / h.

[0064] According to one aspect of the invention, after steps 1-3), the first molecular sieve containing the first template agent is pulverized (e.g., ground) to an average particle size of more than 85% passing through 60 mesh (preferably more than 90% passing through 100 mesh).

[0065] Preferably, according to the present invention, the first molecular sieve containing the first template agent is substantially not removed after manufacturing. More preferably, the manufacturing method of the present invention does not include a step capable of removing part or all of the first template agent from the first molecular sieve containing the first template agent. The inventors of the present invention have discovered that if the first molecular sieve does not contain a template agent, or if a first molecular sieve without a template agent is added during the synthesis of the second molecular sieve, and both the first and second template agents are added simultaneously, this situation leads to the inability to form a continuous pore structure between the first and second molecular sieves during the synthesis of the composite molecular sieve, severely restricting the diffusion of reactants and products. Since calcination can remove the template agent, according to a preferred embodiment of the present invention, step 1) does not include a calcination step.

[0066] According to one aspect of the invention, step 2) comprises the following steps:

[0067] 2-1) A second mixture is formed by mixing a silicon source, an aluminum source, a phosphorus source, a second template agent, and water.

[0068] 2-2) Mix the first molecular sieve containing the first template agent with the second mixture to obtain a composite mixture.

[0069] 2-3) Optionally, after drying the composite mixture, crystallize the composite mixture to generate the composite molecular sieve.

[0070] 2-4) After optional washing and / or optional filtration, the composite molecular sieve is dried.

[0071] According to one aspect of the invention, in step 2-2), the second mixture is finely coated (e.g., sprayed) onto the first molecular sieve containing the first template agent. Preferably, the morphological integrity (particularly the bulk structure or pore structure) of the first molecular sieve containing the first template agent is substantially maintained after the mixing. In other words, the morphological integrity (particularly the bulk structure or pore structure) of the first molecular sieve containing the first template agent is substantially maintained under the manufacturing conditions of the second molecular sieve. Therefore, according to the invention, the second molecular sieve is grown in situ on the first molecular sieve containing the first template agent. The inventors of the invention have found that maintaining the morphological integrity of the first molecular sieve not only benefits the permeability of the composite molecular sieve's pore structure and enhances the diffusion of reactants and products, but also preserves the active sites of the first molecular sieve, ensuring the reactivity of the catalytic material. If the morphological integrity of the first molecular sieve is severely damaged, the second molecular sieve will be unable to grow on its surface, seriously affecting the confinement effect.

[0072] According to one aspect of the invention, in steps 2-3), drying is an optional step, but is preferred. The inventors of this invention have discovered that the drying process allows the second molecular sieve precursor to form a dry gel on the surface of the first molecular sieve, which is more conducive to the subsequent crystallization process where the molecular sieve grows on its surface. The drying conditions include: a drying temperature of 50℃-160℃, preferably 60℃-120℃, and a drying time of 0.1h-20h, preferably 0.5h-12h.

[0073] According to one aspect of the present invention, in steps 2-3), the composite mixture is dried, and the crystallization conditions include: a crystallization pressure from atmospheric pressure to the system's autogenous pressure, a mass ratio of dry adhesive powder to water of 1:(0.2-0.7), preferably 1:(0.3-0.5), the mixture is placed separately in a hydrothermal high-pressure reactor, the crystallization temperature is 130-220℃ (preferably 150-180℃), and the crystallization time is 24-96h (preferably 24-72h).

[0074] According to one aspect of the invention, in steps 2-4), the drying conditions include: a drying temperature of 80-150°C (preferably 85-130°C) and a drying time of 5-20 hours (preferably 8-15 hours).

[0075] According to one aspect of the invention, the method further includes a step of calcining the composite molecular sieve after steps 2-4), wherein the calcination conditions include: calcination at a temperature of 500-750°C (preferably 550-700°C) under an oxygen-containing atmosphere, and a calcination time of 5-20 hours (preferably 8-15 hours).

[0076] According to one aspect of the present invention, the composite molecular sieve can be manufactured according to the manufacturing method described in any of the foregoing or hereinafter of this specification. The inventors of the present invention have discovered, based on TEM transmission electron microscopy results, that the first molecular sieve has a complete, smooth crystal structure, with at least a portion of its surface covered by a dense layer of the second molecular sieve.

[0077] In the composite molecular sieve of the present invention, the first molecular sieve has a complete, smooth crystal structure, at least a portion of its surface is covered by a dense layer of the second molecular sieve, and preferably, the second molecular sieve densely covers substantially the entire surface of the first molecular sieve.

[0078] According to one aspect of the present invention, the mass ratio of the first molecular sieve to the second molecular sieve is (60-99):1, preferably (70-99):1. The inventors of the present invention have discovered that the composite molecular sieve formed by the present invention mainly consists of the second molecular sieve growing on the surface of the first molecular sieve. If the content of the second molecular sieve is too high, the reaction will occur on the surface of the second molecular sieve, and the composite molecular sieve will not play a confinement role, resulting in a decrease in the contact time between hydrocarbon reactants and the active sites of the catalytic material, and an increase in byproducts such as C4+ and aromatic hydrocarbons.

[0079] According to one aspect of the invention, the average particle size of the first molecular sieve is 85% or more passing through 60 mesh (preferably 90% or more passing through 100 mesh).

[0080] According to one aspect of the invention, the second molecular sieve is only a thin layer. The inventors of the invention have discovered that if the thickness of the second molecular sieve layer is too thick, the confinement effect of the composite molecular sieve is weaker, and more byproducts such as C4 and above hydrocarbons and aromatic hydrocarbons are produced.

[0081] According to the present invention, since the second molecular sieve accounts for a lower proportion in the entire composite molecular sieve, its contribution to the XRD pattern is smaller. Therefore, the XRD pattern of the composite molecular sieve is substantially the same as that of the first molecular sieve. If the relative intensity of the strongest characteristic diffraction peak in the XRD pattern is designated as 100, then vw = very weak (>0 to <10); w = weak (10 to ≤20); m = moderate (>20 to ≤40); s = strong (>40 to ≤60); vs = very strong (>60 to ≤100). Here, "substantially the same" means that the composite molecular sieve is consistent with the first molecular sieve at least on all characteristic diffraction peaks with relative intensities of s to vs (preferably m to vs). In other words, the composite molecular sieve substantially does not show characteristic diffraction peaks with relative intensities of s to vs associated with the second molecular sieve (when the second molecular sieve is measured alone), unless such characteristic diffraction peaks are shared by both the first and second molecular sieves. Based on the surface properties described above in this specification, and without any theoretical limitations, the inventors of this invention believe that the composite molecular sieve of this invention substantially exhibits the characteristics of the first molecular sieve in terms of bulk properties and substantially exhibits the characteristics of the second molecular sieve in terms of surface properties.

[0082] The inventors of this invention discovered that, compared to the micropore size distribution of the first molecular sieve, the composite molecular sieve exhibits two distribution peaks within the micropore size distribution range: one for small pores and one for larger pores. This shows a small number of small-pore channels, while the number of larger-pore channels is slightly reduced. Without being limited by any theoretical constraints, the inventors believe this is because, when the second molecular sieve, with its smaller pore size, is assembled onto the first molecular sieve, it covers a portion of the surface of the first molecular sieve's larger-pore channels, thus reducing the number of larger-pore channels, albeit by a small margin. This phenomenon also indicates that the channels of the first and second molecular sieves are essentially interconnected.

[0083] According to one aspect of the invention, the composite molecular sieve has a bimodal pore distribution, wherein the most probable pore sizes of the pores are 0.38-0.45 nm (preferably about 0.42 nm) and 0.50-0.75 nm (preferably 0.55-0.70 nm), respectively. Preferably, the pores with the most probable pore size of 0.50-0.75 nm account for more than 80% (preferably about 90%) of the total pore volume of the composite molecular sieve. Generally, the BET specific surface area of ​​the composite molecular sieve is 400-650 m². 2 / g (preferably 400-600mg) 2 / g), with a pore volume of 0.30-0.70 ml / g (preferably 0.30-0.60 ml / g).

[0084] According to one aspect of the invention, a catalytic cracking catalyst is also involved, which is obtained by ion exchange treatment of the composite molecular sieve as described above.

[0085] According to one aspect of the present invention, the conditions for the ion exchange treatment (single) include: an ammonium salt solution concentration of 1-2 mol / L, a solid-liquid mass ratio of the composite molecular sieve to the ammonium salt solution of 1:(10-30), a reaction temperature of 60-100°C, and a reaction time of 1-3 hours.

[0086] According to one aspect of the invention, a catalytic cracking method is also disclosed, comprising catalytic cracking of C in the presence of a catalytic cracking catalyst as described above. 5-10 n-Alkanes or naphtha to produce C 2-4 The steps of olefins.

[0087] According to one aspect of the present invention, the conditions for the catalytic cracking include: nitrogen as the carrier gas, a nitrogen flow rate of 30-50 ml / min, a reaction temperature of 500℃-700℃, and a feed space velocity of 2-5 h⁻¹. -1 .

[0088] According to one aspect of the invention, a molecular sieve precursor is also disclosed, comprising a molecular sieve and a template agent. The precursor has an average particle size of at least 85% passing through 60 mesh (preferably at least 90% passing through 100 mesh) and a free water content of no more than 10 wt% (preferably no more than 5 wt%). The template agent is selected from at least one of ethylenediamine, triethanolamine, tetrapropylammonium hydroxide, n-butylamine, ethylamine, 1,6-hexanediamine, tripropylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, tetraethylammonium fluoride, triethylamine, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, polyvinyl alcohol, and sodium carboxymethyl cellulose, preferably at least one of ethylenediamine and triethanolamine. Furthermore, the molecular sieve is selected from at least one of MFI-configured molecular sieves and beta-configured molecular sieves (preferably at least one of ZSM-5 molecular sieves and beta molecular sieves).

[0089] According to one aspect of the invention, after the precursor is washed twice with deionized water at room temperature, the loss rate of the template agent is less than 10 wt% (preferably less than 5 wt% or less than 2 wt%). Furthermore, based on a total weight of 100 wt% of the precursor, the content of the template agent is 20-70 wt% (preferably 30-60 wt%).

[0090] Example

[0091] The present invention will be further described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0092] Example 1

[0093] (1) 2g sodium hydroxide, 1.36g sodium aluminate, 22.4g triethanolamine, and 100g silica sol (30% by mass) were added to 180g deionized water and stirred at room temperature to form a homogeneous initial gel mixture. The gel mixture was crystallized at 150℃ for 48h. After crystallization, the crystallized product was spray-dried under the following conditions: solid content 30%, inlet air temperature 140℃, outlet air temperature 80℃, and inlet air volume 550m³. 3 / h, yielding the first molecular sieve N1, which is a Beta molecular sieve.

[0094] The main molecular sieve N1 is not calcined, and its average particle size is more than 95% passing through 100 mesh, free water content is 3wt%, template agent content is 40wt%, and template agent loss rate is less than 5wt%.

[0095] (2) Add 0.42g of boehmite, 0.71g of phosphoric acid, 0.82g of silica sol (30% by mass) and 1.58g of N,N-diisopropylethylamine to 6.2g of water and stir until homogeneous. Stir at room temperature until a homogeneous second molecular sieve gel mixture is formed. The gel mixture is then sprayed onto the molecular sieve prepared in step (1) and dried at 60℃ for 4h to obtain a composite dry gel. The composite dry gel is crystallized at 160℃ and a water vapor pressure of 1MPa for 72 hours. After crystallization, it is dried at 110℃ for 8h and calcined at 650℃ in air for 4h to obtain the composite molecular sieve M1, which is formed by coating Beta molecular sieve with SAPO-18 molecular sieve.

[0096] Figure 1 The image shows the XRD pattern of the composite molecular sieve, which is essentially the same as that of the first molecular sieve. Figure 2 The XRD pattern of the composite molecular sieve after light grinding and sieving is shown below. Figure 1 Compared to the characteristic peak shape, a weaker SAPO-18 characteristic diffraction peak appeared at 2θ = 9.509, indicating that the type of the second molecular sieve is SAPO-18 molecular sieve.

[0097] Figure 3The pore size distribution results for the composite molecular sieve and the first molecular sieve are shown. It can be seen that the composite molecular sieve exhibits two distribution peaks: one for small pores and one for larger pores. Compared to the first molecular sieve, the introduction of the second molecular sieve in the composite molecular sieve reduces the proportion of larger pores, with a smaller decrease, and introduces a new small pore distribution peak, indicating that the pores of the first and second molecular sieves are essentially interconnected. TEM images reveal that the dual-microporous composite molecular sieve M1 consists of a first molecular sieve (Beta molecular sieve) and a second molecular sieve (SAPO-18 molecular sieve) covering the surface of the first molecular sieve. Figure 4 As shown. According to Figure 4 It can be seen that a dense crystalline material covers the original crystal surface of the first molecular sieve, Beta molecular sieve, and a clear boundary between the two can be seen when magnified.

[0098] Measurements showed that the mass ratio of the first to the second molecular sieve in the dual-microporous composite molecular sieve M1 was 90:1. The composite molecular sieve exhibited a bimodal pore distribution, with the most probable pore diameters being 0.43 nm and 0.65 nm, respectively. Pores with a most probable diameter of 0.65 nm accounted for 90% of the total pore volume. The BET specific surface area of ​​the composite molecular sieve was 602 m². 2 / g, pore volume is 0.40ml / g.

[0099] (3) The above-mentioned composite molecular sieve was placed in a 1 mol / L ammonium nitrate solution with a solid-liquid mass ratio of 1:10. Three ion exchanges were performed at 80℃, each lasting 1 h. The ion-exchanged sample was filtered, washed, dried at 110℃ for 8 h, and then calcined in a muffle furnace at 550℃ for 4 h. After pressing into tablets, the resulting 20-40 mesh composite molecular sieve catalyst A1 was obtained. The physicochemical properties and evaluation results are shown in Table 1.

[0100] Example 2

[0101] (1) 0.39 g sodium hydroxide, 1.36 g sodium aluminate, 36 g ethylenediamine, and 100 g silica sol (mass fraction 30%) were added to 120 g deionized water and stirred at room temperature to form a homogeneous initial gel mixture. After crystallization at 170 °C for 48 h, the crystallized product was spray-dried under the following conditions: solid content 30%, inlet air temperature 140 °C, outlet air temperature 80 °C, and inlet air volume 550 m³ / h, to obtain the first molecular sieve N2, which is a ZSM-5 molecular sieve.

[0102] The main molecular sieve N2 is not calcined, and its average particle size is more than 95% passing through 100 mesh, free water content is 3wt%, template agent content is 50wt%, and template agent loss rate is less than 5wt%.

[0103] (2) 0.42g of boehmite, 0.71g of phosphoric acid, 0.82g of silica sol (30% by mass) and 1.58g of N,N-diisopropylethylamine were added to 6.2g of water and stirred until homogeneous. The mixture was stirred at room temperature until a homogeneous second molecular sieve gel mixture was formed. The gel mixture was then sprayed onto the molecular sieve prepared in step (1) and dried at 60℃ for 4h to obtain a composite dry gel. The composite dry gel was crystallized at 160℃ and a steam pressure of 1MPa for 72 hours. After crystallization, it was dried at 110℃ for 8h and calcined at 650℃ for 4h in air to obtain the composite molecular sieve M2, which is a SAPO-18 molecular sieve coated with a ZSM-5 molecular sieve. The mass ratio of the first molecular sieve to the second molecular sieve in the dual-microporous composite molecular sieve M2 was measured to be 90:1. The composite molecular sieve exhibits a bimodal pore distribution with most probable pore sizes of 0.43 nm and 0.65 nm, respectively. Pores with a most probable pore size of 0.65 nm account for 92% of the total pore volume. The composite molecular sieve has a BET specific surface area of ​​454 m². 2 / g, pore volume is 0.31ml / g.

[0104] (3) The above-mentioned composite molecular sieve was placed in a 1 mol / L ammonium nitrate solution with a solid-liquid mass ratio of 1:10. Three ion exchanges were performed at 80℃, each lasting 1 h. The ion-exchanged sample was filtered, washed, dried at 110℃ for 8 h, and then calcined in a muffle furnace at 550℃ for 4 h. After pressing into tablets, the resulting 20-40 mesh composite molecular sieve catalyst A2 was obtained. The physicochemical properties and evaluation results are shown in Table 1.

[0105] Example 3

[0106] The synthesis of the composite molecular sieve and the preparation and evaluation of the catalyst were the same as in Example 1, except that: the second molecular sieve was SSZ-39, the silicon source, aluminum source and template agent were silica sol, sodium aluminate and TMPOH, the catalyst was named A3, and the evaluation results of the catalyst are shown in Table 1.

[0107] Example 4

[0108] The synthesis of the composite molecular sieve and the preparation and evaluation of the catalyst were the same as in Example 2, except that: the second molecular sieve was SSZ-39, the silicon source, aluminum source and template agent were silica sol, sodium aluminate and TMPOH, the catalyst was named A4, and the evaluation results of the catalyst are shown in Table 1.

[0109] Example 5

[0110] The synthesis of the composite molecular sieve and the preparation and evaluation of the catalyst were the same as in Example 1, except that the mass ratio of the first molecular sieve to the second molecular sieve was 80:1, the catalyst was named A5, and the evaluation results of the catalyst are shown in Table 1.

[0111] Example 6

[0112] The synthesis of the composite molecular sieve and the preparation and evaluation of the catalyst were the same as in Example 2, except that the mass ratio of the first molecular sieve to the second molecular sieve was 70:1, the catalyst was named A6, and the evaluation results of the catalyst are shown in Table 1.

[0113] Example 7

[0114] The synthesis of the composite molecular sieve and the preparation and evaluation of the catalyst were the same as in Example 1, except that: the average particle size of the main molecular sieve N1 was more than 85% passing through 60 mesh, the catalyst was named A7, and the evaluation results of the catalyst are shown in Table 1.

[0115] Example 8

[0116] The synthesis of the composite molecular sieve and the preparation and evaluation of the catalyst were the same as in Example 1, except that the free water content of the first molecular sieve of the first template agent was 10 wt%, the catalyst was named A8, and the evaluation results of the catalyst are shown in Table 1.

[0117] Example 9

[0118] The synthesis of the composite molecular sieve and the preparation and evaluation of the catalyst were the same as in Example 1, except that: the drying in the molecular sieve preparation process was carried out using ordinary drying, the catalyst was named A9, and the evaluation results of the catalyst are shown in Table 1.

[0119] Comparative Example 1

[0120] The H-beta molecular sieve crystallization and ion exchange process is the same as in Example 1. After crystallization, it is dried at 110°C for 8 hours and calcined at 550°C in air for 4 hours. The 20-40 mesh particles obtained after tableting and sieving are the comparative catalyst, numbered B1. Its physicochemical properties and evaluation results are shown in Table 1.

[0121] Comparative Example 2

[0122] The crystallization and ion exchange process of HZSM-5 molecular sieve is the same as in Example 2. After crystallization, it is dried at 110°C for 8 hours and calcined at 550°C in air for 4 hours. The 20-40 mesh particles obtained after tableting and sieving are the comparative catalyst, numbered B2. Its physicochemical properties and evaluation results are shown in Table 1.

[0123] Comparative Example 3

[0124] The synthesis of the composite molecular sieve and the preparation and evaluation of the catalyst were the same as in Example 1, except that the first molecular sieve was SAPO-18 molecular sieve, the second molecular sieve was beta molecular sieve, the catalyst was named B3, and the evaluation results of the catalyst are shown in Table 1.

[0125] Comparative Example 4

[0126] The synthesis of the composite molecular sieve and the preparation and evaluation of the catalyst were the same as in Example 1, except that the first molecular sieve was SAPO-18 molecular sieve, the second molecular sieve was ZSM-5 molecular sieve, the catalyst was named B4, and the evaluation results of the catalyst are shown in Table 1.

[0127] Comparative Example 5

[0128] The synthesis of the composite molecular sieve and the preparation and evaluation of the catalyst were the same as in Example 1, except that the mass ratio of the first molecular sieve to the second molecular sieve was 110:1, the catalyst was named B5, and the evaluation results of the catalyst are shown in Table 1.

[0129] Comparative Example 6

[0130] The synthesis of the composite molecular sieve and the preparation and evaluation of the catalyst were the same as in Example 2, except that the mass ratio of the first molecular sieve to the second molecular sieve was 50:1, the catalyst was named B6, and the evaluation results of the catalyst are shown in Table 1.

[0131] Comparative Example 7

[0132] The synthesis of composite molecular sieves and the preparation and evaluation of catalysts are the same as in Example 1, except that: after the first molecular sieve is prepared, it is calcined and then coated with the already manufactured second molecular sieve. The mass ratio of the first molecular sieve to the second molecular sieve is 90:1. The catalyst is named B7. The evaluation results of the catalyst are shown in Table 1.

[0133] Comparative Example 8

[0134] The synthesis of the composite molecular sieve and the preparation and evaluation of the catalyst were the same as in Example 1, except that 0.5 g of NaOH was added to destroy the structure of the first molecular sieve when preparing the second molecular sieve. The mass ratio of the first molecular sieve to the second molecular sieve was 90:1. The catalyst was named B8. The evaluation results of the catalyst are shown in Table 1.

[0135] Comparative Example 9

[0136] The synthesis of the composite molecular sieve and the preparation and evaluation of the catalyst were the same as in Example 2, except that: 1,6-hexanediol was used to replace the template agent in the preparation of the first molecular sieve, the mass ratio of the first molecular sieve to the second molecular sieve was 90:1, the catalyst was named B9, and the evaluation results of the catalyst are shown in Table 1.

[0137] The catalytic cracking reaction conditions for n-heptane are as follows: n-heptane is used as the raw material, the catalyst loading is 5 ml, nitrogen is introduced as the carrier gas at a flow rate of 30 ml / min, the reaction temperature is 650℃, and the feed space velocity is 2 h⁻¹. -1 .

[0138] Table 1. Physicochemical properties and evaluation results of the catalysts

[0139] Catalyst number <![CDATA[S BET / m 2 / g ]]> <![CDATA[V total / ml / g ]]> n-Heptane conversion rate / % Ethylene selectivity / % Propylene selectivity / % A1 602 0.40 56.9 29.8 37.7 A2 454 0.31 65.4 24.3 33.2 A3 604 0.39 55.7 26.5 35.3 A4 451 0.31 63.8 22.4 32.1 A5 598 0.40 56.5 28.1 35.8 A6 454 0.31 63.2 26.4 31.4 A7 592 0.39 53.4 26.2 34.7 A8 595 0.40 54.1 25.3 34.2 A9 596 0.40 53.7 25.9 33.4 B1 605 0.39 51.3 20.6 30.1 B2 452 0.30 61.6 15.4 25.5 B3 533 0.34 42.8 16.9 18.6 B4 530 0.34 43.4 17.2 19.2 B5 602 0.40 50.5 21.1 31.0 B6 454 0.31 57.4 12.7 20.5 B7 603 0.39 49.9 20.4 28.3 B8 531 0.39 36.5 11.9 14.4 B9 384 0.29 50.3 12.5 13.1

[0140] As can be seen from the results in Table 1, the catalyst of the present invention significantly improves the selectivity of ethylene and propylene in the reaction of n-heptane catalytic cracking to produce low-carbon olefins compared with the comparative catalyst.

Claims

1. A method for manufacturing a composite molecular sieve, comprising the following steps: 1) Provide a first molecular sieve containing a first template agent (e.g., manufacture the first molecular sieve containing the first template agent in the presence of the first template agent), then 2) A second molecular sieve is manufactured in the presence of a second template agent and the first molecular sieve containing the first template agent to obtain the composite molecular sieve. The first template agent and the second template agent are different in chemical structure, and the first molecular sieve is selected from at least one of MFI molecular sieve and beta molecular sieve (preferably selected from at least one of ZSM-5 molecular sieve and beta molecular sieve), and the second molecular sieve is AEI molecular sieve (preferably SAPO-18 molecular sieve).

2. The manufacturing method of claim 1, wherein in step 1), a silicon source, an aluminum source, an alkali source, and water are further present, wherein the molar ratio of the silicon source: the aluminum source: the alkali source: the first template agent R: water is SiO2:Al2O3:OH - :R:H2O=1:0.01-0.1:0.02-2:0.03-2:5-60 (preferably SiO2:Al2O3:OH) - The molar ratio of silicon source: aluminum source: phosphorus source: second template agent D: water is 1:0.01-0.05:0.02-2:0.03-2:5-60, and / or, in step 2), a silicon source, an aluminum source, a phosphorus source, and water are also present, wherein the molar ratio of silicon source: aluminum source: phosphorus source: second template agent D: water is SiO2:Al2O3:P2O5:D:H2O = 0.01-2:1:0.1-2:0.5-5:20-100 (preferably SiO2:Al2O3:P2O5:D:H2O). =0.03-1:1:0.5-1.5:1-3:20-100), and / or, the total mass ratio of the first molecular sieve containing the first template agent to the silicon source, aluminum source and phosphorus source in step 2) is (55-99):1, preferably (65-99):1, and / or, the average particle size of the first molecular sieve containing the first template agent is more than 85% passing through 60 mesh (preferably more than 90% passing through 100 mesh), and / or, the free water content of the first molecular sieve containing the first template agent is not greater than 10wt% (preferably not greater than 5wt%), and / or, based on the total weight of the first molecular sieve containing the first template agent as 100wt%, the content of the first template agent is 20-70wt% (preferably 30-60wt%), and / or, after washing the first molecular sieve containing the first template agent with deionized water twice at room temperature, the loss rate of the first template agent is less than 10wt% (preferably less than 5wt% or less than 2wt%).

3. The manufacturing method of claim 1, wherein the first template agent and the second template agent are capable of forming hydrogen bonds or ionic bonds with each other in the presence of water, and / or the first template agent is capable of being used to synthesize the first molecular sieve, and / or the first template agent is selected from at least one of ethylenediamine, triethanolamine, tetrapropylammonium hydroxide, n-butylamine, ethylamine, 1,6-hexanediamine, tripropylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, tetraethylammonium fluoride, triethylamine, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, polyvinyl alcohol, and sodium carboxymethyl cellulose, preferably selected from at least one of ethylenediamine and triethanolamine, and / or the second template agent is capable of being used to synthesize the second molecular sieve, and / or the second template agent is selected from at least one of N,N-diisopropylethylamine, tetraethylammonium hydroxide, triethylamine, and N,N-methyl-3,5-dimethylpiperidine, preferably N,N-diisopropylethylamine.

4. The manufacturing method of claim 1, wherein step 1) comprises the following steps: 1-1) A first mixture is formed by mixing a silicon source, an aluminum source, an alkali source, a first template agent, and water. 1-2) Crystallize the first mixture to generate the first molecular sieve containing the first template agent. 1-3) Separate the first molecular sieve containing the first template agent (preferably, optionally after filtration, dry (especially spray dry) the first molecular sieve containing the first template agent).

5. The manufacturing method of claim 4, wherein in steps 1-2), the crystallization conditions include: The crystallization pressure is from atmospheric pressure to the system's autogenous pressure, with or without seed crystals; the crystallization temperature is 130-220℃ (preferably 150-180℃); the crystallization time is 24-96h (preferably 48-96h); and / or, in steps 1-3), the drying conditions include: a drying temperature of 60-120℃ (preferably 65-110℃); a drying time of 5-20 hours (preferably 8-15 hours); and / or, the spray drying conditions include: a solid content of 35-65%; an inlet air temperature of 150-250℃; an outlet air temperature of 80-150℃; and an air velocity of 300-1500 m / s. 3 / h, and / or, further comprising, after steps 1-3), pulverizing (e.g., grinding) the first molecular sieve containing the first template agent to an average particle size of more than 85% passing through 60 mesh (preferably more than 90% passing through 100 mesh).

6. The manufacturing method of claim 1, excluding the step of removing part or all of the first template agent from the first molecular sieve containing the first template agent, and / or, wherein step 1) does not include a calcination step.

7. The manufacturing method of claim 1, wherein step 2) comprises the following steps: 2-1) A second mixture is formed by mixing a silicon source, an aluminum source, a phosphorus source, a second template agent, and water. 2-2) The first molecular sieve containing the first template agent is mixed with the second mixture to obtain a composite mixture. 2-3) Optionally, after drying the composite mixture, crystallize the composite mixture to generate the composite molecular sieve. 2-4) After optional washing and / or optional filtration, the composite molecular sieve is dried.

8. The manufacturing method of claim 7, wherein in step 2-2), the second mixture is finely coated (e.g., sprayed) onto the first molecular sieve containing the first template agent, and / or, in step 2-2), the morphological integrity (particularly the bulk structure or pore structure) of the first molecular sieve containing the first template agent is substantially maintained after the mixing.

9. The manufacturing method of claim 7, wherein in steps 2-3), the composite mixture is dried, and the crystallization conditions include: The crystallization pressure is from atmospheric pressure to the system's own pressure. The mass ratio of dry adhesive powder to water is 1:(0.2-0.7), preferably 1:(0.3-0.5). The powder is placed separately in a hydrothermal high-pressure reactor. The crystallization temperature is 130-220℃ (preferably 150-180℃), and the crystallization time is 24-96h (preferably 24-72h). And / or, in steps 2-3), the drying conditions include: a drying temperature of 50℃-160℃ (preferably 60℃-120℃), and a drying time of 0.1h-20h (preferably 0.5h-12h). And / or, in steps 2-4), the drying conditions include: a drying temperature of 80-150℃ (preferably 85-130℃), and a drying time of 5-20 hours (preferably 8-15 hours).

10. The manufacturing method of claim 7, further comprising, after steps 2-4), a step of calcining the composite molecular sieve, wherein the calcination conditions include: Under an oxygen-containing atmosphere, the calcination temperature is 500-750℃ (preferably 550-700℃), and the calcination time is 5-20 hours (preferably 8-15 hours).

11. The manufacturing method of claim 1, wherein in step 1), the first molecular sieve containing the first template agent is substantially not removed after manufacturing, and / or, in step 2), the morphological integrity (particularly the bulk structure or pore structure) of the first molecular sieve containing the first template agent is substantially maintained under the manufacturing conditions of the second molecular sieve, and / or, in step 2), the second molecular sieve is grown in situ on the first molecular sieve containing the first template agent.

12. A composite molecular sieve, comprising a first molecular sieve and a second molecular sieve covering the surface of the first molecular sieve, wherein the first molecular sieve is selected from at least one of MFI configuration molecular sieve and beta configuration molecular sieve (preferably selected from at least one of ZSM-5 molecular sieve and beta molecular sieve), the second molecular sieve is an AEI configuration molecular sieve (preferably SAPO-18 molecular sieve), and the mass ratio of the first molecular sieve to the second molecular sieve is (60-99):1, preferably (70-99):

1.

13. The composite molecular sieve of claim 12, wherein the average particle size of the first molecular sieve is more than 85% passing through 60 mesh (preferably more than 90% passing through 100 mesh).

14. The composite molecular sieve of claim 12, wherein the first molecular sieve and the second molecular sieve are substantially interconnected in terms of pores, and / or, the XRD pattern of the composite molecular sieve is substantially the same as that of the first molecular sieve, and / or, the composite molecular sieve has a bimodal pore distribution, and / or, the most probable pore sizes of the pore distribution of the composite molecular sieve are 0.38-0.45 nm (preferably about 0.42 nm) and 0.50-0.75 nm (preferably 0.55-0.70 nm), respectively, and / or, the pores with the most probable pore size of 0.50-0.75 nm account for more than 80% (preferably about 90%) of the total pore volume of the composite molecular sieve, and / or, the BET specific surface area of ​​the composite molecular sieve is 400-650 m². 2 / g (preferably 400-600mg) 2 / g), with a pore volume of 0.30-0.70ml / g (preferably 0.30-0.60ml / g).

15. The composite molecular sieve of claim 12 can be manufactured according to the manufacturing method of any one of claims 1-11.

16. A catalytic cracking catalyst obtained by ion exchange treatment of the composite molecular sieve of claim 12.

17. The catalytic cracking catalyst of claim 16, wherein the conditions for the ion exchange treatment (single) include: The concentration of the ammonium salt solution is 1-2 mol / L, the solid-liquid mass ratio of the composite molecular sieve to the ammonium salt solution is 1:(10-30), the reaction temperature is 60-100℃, and the reaction time is 1-3 hours.

18. A catalytic cracking method, comprising catalytically cracking C in the presence of the catalytic cracking catalyst of claim 16. 5-10 n-Alkanes or naphtha to produce C 2-4 The steps of olefins.

19. The catalytic cracking method of claim 18, wherein the conditions for catalytic cracking include: Nitrogen is used as the carrier gas, with a flow rate of 30-50 ml / min. The reaction temperature is 500℃-700℃, and the feed space velocity is 2-5 h⁻¹. -1 .

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