MFI molecular sieve catalyst, its preparation method and use thereof

Abstract

Disclosed is an MFI molecular sieve having the following characteristics: each unit mass of the MFI molecular sieve contains both monoclinic and orthorhombic crystalline forms of the MFI molecular sieve; and the hydroxyl group infrared spectrum of the MFI molecular sieve is 3400-3500 cm -1 The characteristic peak of the hydroxyl group is at 3420 to 3480 cm -1 The characteristic peak is centered around the highest point, and the peak area having a half-width of 210 to 240 accounts for 70% or more of the total peak area; the MFI molecular sieve contains elements of Si, Al and O, but does not contain element of Ti.

Description

Detailed Description of the Invention

[0001] [Technical field] The present disclosure relates to the technical field of catalytic cracking, and in particular to a novel MFI molecular sieve catalyst and its method of preparation, and its use in increasing the production of propylene and ethylene via catalytic cracking of olefins.

[0002] [Background technology] Low-carbon olefins (mainly propylene and ethylene) are important basic organic chemical feedstocks. In recent years, the demand for ethylene and propylene has increased significantly due to the growing demand for polyolefins and alkylaromatic compounds. Currently, most of the propylene produced worldwide comes from the by-products of steam crackers and catalytic crackers. The propylene to ethylene ratio in steam crackers is approximately 0.6. The investment costs for increasing propylene yield in refinery FCC units are high. To address this issue, various countries have developed several alternative propylene production methods, including the butene isomerization (olefin metathesis technology, OMT) process, which increases propylene production by reacting ethylene with butene; the propane dehydrogenation (PDH) process, which directly uses propane for chemical applications; and the methanol-to-olefins (MTP / MTO) process, which uses coal-derived methanol to produce propylene and ethylene. An important research and development direction for petrochemical companies worldwide is the development of new processes to increase propylene and ethylene production through catalytic cracking of olefins by using C4 and C5 olefins produced in large quantities by ethylene plants, FCC units, and MTO units. Catalysts are the key technology in catalytic processes, and their reaction rate, selectivity, and stability are closely related to the pore and crystalline structures of the catalyst. Catalyst performance and product distribution can be directly affected by post-treatment, component modification, and the formation of heat-resistant molecular sieves with new structures.

[0003] Olefin cracking catalysts are mainly MFI molecular sieves with regular pore channels. These catalysts can be prepared by conventional molecular sieve synthesis methods, which require 4 to 48 hours of aging and 6 to 120 hours of crystallization. This method is time-consuming and has low process efficiency. When the resulting catalyst is used in a reaction, carbon is easily deposited on the surface of the aluminum silicate molecular sieve due to side reactions associated with the cracking, such as polymerization and dehydration cycloreversion, resulting in low catalytic activity, low selectivity for the two olefin products, and poor stability. EP0109059A1 describes a C4-C 12 A process for cracking olefins to produce propylene is disclosed, in which ZSM5 or ZSM11 molecular sieves obtained by conventional synthesis are used as catalysts. 12 One patent discloses a process for cracking olefins to produce propylene and ethylene. The catalyst contains a ZSM-5 molecular sieve, synthesized by a traditional method that does not contain protonic acid but does contain a Group 1B metal, as the active component. CN200910072747.7 introduces a method for preparing MFI molecular sieves. This involves adding precrystallized seeds to a template-free gel system for nanomolecular sieve synthesis, followed by crystallization at 160-180°C for 24 hours, cooling to room temperature, and subjecting the resulting product to centrifugation, filtration, washing, drying, and calcination. Both of these patents use traditional molecular sieve synthesis methods, and the resulting olefin cracking catalysts suffer to varying degrees from poor product selectivity, poor catalytic stability, and susceptibility to coking and deactivation.

[0004] [Summary of the Invention] The present disclosure addresses the problems of low stability, low selectivity to the two olefin products, and low efficiency in the conventional synthesis associated with current catalysts for producing propylene and ethylene via catalytic cracking of olefins. In the present disclosure, MFI molecular sieves, particle catalysts containing the same, MFI molecular sieve catalysts containing the same, and methods for their preparation, as well as the use of the catalysts in increasing the production of propylene and ethylene via catalytic cracking of olefins, are provided. When the novel MFI molecular sieve catalyst according to the present disclosure is used to produce propylene and ethylene via catalytic cracking of olefins, the novel MFI molecular sieve catalyst has the advantages of good stability and high selectivity to the two olefin products.

[0005] In one embodiment, the present disclosure provides an MFI molecular sieve having the following characteristics: each unit mass of the MFI molecular sieve contains both monoclinic and orthorhombic crystalline forms of the MFI molecular sieve; the MFI molecular sieve has a hydroxyl group infrared spectrum of 3400 to 3500 cm -1 The characteristic peak of the hydroxyl group is in the range of 3420 to 3480 cm -1 and the peak area of ​​a characteristic peak having a maximum point at a position between 210 and 240 and centered around the maximum point and having a half-width of 210 to 240 accounts for 70% or more of the total peak area; and the MFI molecular sieve is characterized in that it contains elements of Si, Al and O, but does not contain element Ti.

[0006] In the present invention, the infrared spectrum is an absorption spectrum, and therefore the characteristic peaks are absorption peaks.

[0007] In a further aspect, the present disclosure provides a catalyst particle comprising: A) an MFI molecular sieve according to the present disclosure; B) at least two different templates T1 and T2; and C) binder.

[0008] In a further aspect, the present disclosure provides an MFI molecular sieve catalyst comprising: a) an MFI molecular sieve according to the present disclosure; optionally, b) a boron group element R1; and Optionally, c) a nitrogen group element R2.

[0009] Thus, for example, in one embodiment according to the present disclosure, an MFI molecular sieve catalyst is provided, and each unit mass of the catalyst contains both monoclinic and orthorhombic crystalline forms of the MFI molecular sieve. For example, the monoclinic crystalline molecular sieve and the orthorhombic crystalline molecular sieve may be in a molar ratio of 5 to 100 (i.e., 5:1 to 100:1). Preferably, the MFI molecular sieve catalyst has a hydroxyl group infrared spectrum of 3400 to 3500 cm. -1 The characteristic hydroxyl group peak may be at 3420 to 3480 cm -1 The peak area of ​​the characteristic peak having a maximum point at a position between 210 and 240 and centered around the maximum point and having a half-width of 210 to 240 accounts for 70% or more of the total peak area.

[0010] For the present invention, based on the specific raw materials and specific preparation process used in the present disclosure, the inventors have surprisingly found that, unlike simple physical mixtures, the monoclinic crystalline molecular sieve and the orthorhombic crystalline molecular sieve according to the present disclosure coexist at the molecular level. Therefore, when analyzing each unit mass of MFI molecular sieve, particle catalyst, or MFI molecular sieve catalyst according to the present disclosure, the coexistence of two crystalline forms of the MFI molecular sieve (monoclinic crystalline form and orthorhombic crystalline form) is obtained, excluding obvious measurement errors. For the purposes of the present invention, the unit mass can be understood and determined as the smallest mass of a powder sample that can be tested by XRD, for example, 500 mg, 300 mg, or 200 mg of powder sample. Without being bound by any known theory, the coexistence of the two crystalline forms of the MFI molecular sieve obtained in the present disclosure is believed to be particularly advantageous for the purposes of the present invention, such as the required conversion and selectivity.

[0011] The inventors further surprisingly found that the MFI molecular sieve, particle catalyst or MFI molecular sieve catalyst according to the present disclosure has a hydroxyl group infrared spectrum of 3400 to 3500 cm -1 It was found that the characteristic peaks of hydroxyl groups were observed at 3420 to 3480 cm, and each peak had a typical broad peak characteristic. -1 The peak area of ​​the characteristic peak having a maximum between 210 and 240, centered around the maximum, and having a half-width between 210 and 240 accounts for 70% or more of the total peak area. As commonly understood and used in the art, for purposes of this invention, when calculating the peak area of ​​a hydroxyl group infrared spectrum, the integrated area is relevant, and the line joining the two lowest points on the spectral curve is the starting reference line for integration.

[0012] Furthermore, the MFI molecular sieve, particle catalyst, or MFI molecular sieve catalyst according to the present disclosure each has a hydroxyl group infrared spectrum of 3460 to 3470 cm -1 An absorption peak with a maximum intensity can be seen at

[0013] Furthermore, the MFI molecular sieve, particle catalyst, or MFI molecular sieve catalyst according to the present disclosure may comprise monoclinic and orthorhombic crystal forms, respectively, in a molar ratio preferably of 6:1 to 50:1, more preferably 8:1 to 20:1, and even more preferably 8:1 to 15:1.

[0014] Additionally, the MFI molecular sieve, particle catalyst, or MFI molecular sieve catalyst according to the present disclosure can each comprise monoclinic and orthorhombic crystalline forms in a molar ratio such as, but not limited to, 8.1:1, 8.2:1, 8.3:1, 8.4:1, 8.5:1, 8.6:1, 8.7:1, 8.8:1, 8.9:1, 9:1, 9.1:1, 9.2:1, 9.3:1, 9.4:1, 9.5:1, 9.6:1, 9.7:1, 9.8:1, 9.9:1, 10:1, etc.

[0015] Furthermore, the MFI molecular sieve catalyst has a particle size of 200 to 1000 m 2 / g, preferably 300 to 800m 2 / g, more preferably 400 to 600m 2 / g specific surface area.

[0016] Furthermore, in the MFI molecular sieve catalyst, the molecular sieve is a hydrogen-type molecular sieve.

[0017] Additionally, the MFI molecular sieve catalyst may comprise, based on the total weight of the catalyst: a) the MFI molecular sieve in an amount of 90 to 100%, preferably 92 to 99%; b) the boron group element R1 in an amount of 0 to 5%, preferably 0.5 to 3.0%; and c) the nitrogen group element R2 in an amount of 0 to 5%, preferably 0.5 to 5.0%.

[0018] Furthermore, in the MFI molecular sieve, particle catalyst or MFI molecular sieve catalyst, the molecular sieve may have a molar ratio of SiO2 / Al2O3 of 80-1500, preferably 80-1000.

[0019] Furthermore, in the particle catalyst or the MFI molecular sieve catalyst, the boron group element R1 is at least one selected from the group consisting of B and Ga, and / or the nitrogen group element R2 is at least one selected from the group consisting of N, P, As, Sb, and Bi.

[0020] Furthermore, the particle catalyst or the MFI molecular sieve catalyst may further comprise a binder, which may be present in an amount of 5% or less, preferably 2% or less, and more preferably 0.5% or less, based on the weight of the catalyst.

[0021] In a further aspect, the present disclosure provides a method for preparing the above-described MFI molecular sieve catalyst, comprising the steps of: Step 1: Preparing MFI molecular sieve raw material powder; Step 2: kneading and molding the molecular sieve raw material powder obtained in step 1 with a binder, and drying to obtain catalyst particles; Step 3: The catalyst particles obtained in Step 2 are subjected to hydrothermal crystallization and ammonium exchange in the presence of template T3 to obtain an MFI molecular sieve catalyst. Step 3, particularly the hydrothermal crystallization and ammonium exchange, is useful for obtaining the hydrogen form molecular sieve required by the present invention.

[0022] In one embodiment of the present invention, the particle catalyst according to the present disclosure may be obtained by carrying out steps 1 and 2 in the above-mentioned method for preparing the MFI molecular sieve catalyst.

[0023] Furthermore, step 1 of preparing the MFI molecular sieve raw material powder may include the following steps: mixing a silicon source, an aluminum source, a template T1, a template T2, water, and optionally a boron group element R1 and / or optionally a nitrogen group element R2 to prepare a raw material gel; Crystallize, wash and dry.

[0024] Furthermore, for the purpose of the present invention, in preparing the raw powder of MFI molecular sieve, template T1 is preferably an ammonium compound, such as at least one selected from the group consisting of tetrapropylammonium bromide, tetrapropylammonium hydroxide, tetramethylammonium bromide, tetraethylammonium bromide, tetrabutylammonium bromide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. Preferably, for the purpose of the present invention, template T2 is a specific template containing an amino group, such as at least one of phthalimide, taurine, and naphthalenediamine. The introduction of template T2 and adjusting the ratio of template T1 to template T2 can control the ratio of orthorhombic to monoclinic crystal forms, resulting in the catalyst.

[0025] Furthermore, in preparing the MFI molecular sieve raw material powder, the silicon source may be at least one of silica sol, tetraethyl orthosilicate, and silicate; and / or the aluminum source may be at least one of aluminum sulfate, aluminum isopropoxide, and aluminate.

[0026] Furthermore, in preparing the MFI molecular sieve raw material powder, the silicon source, the aluminum source, the template, the boron group element, the nitrogen group element and water may be in the following molar ratios: H2O / SiO2=10~500; Si / Al=20~∞; T1 / SiO2=0.01~20; T2 / T1=0.01~30, preferably 0.1~20; R1 / SiO2=0~50, preferably 0.1~30; R2 / SiO2=0~50, preferably 0.1~30.

[0027] Furthermore, the preparation of MFI molecular sieve raw material powder is carried out in a supergravity reactor. A supergravity reactor is a type of reactor known in the art. This type of reactor is used in the present disclosure and has a specific configuration. For example, it may include preparing a raw material gel by mixing a silicon source, an aluminum source, template T1, template T2, water, and optionally a boron group element R1 and / or optionally a nitrogen group element R2; sending the mixture to a supergravity aging-crystallizing integrated device for premixing and circulation, then directly subjecting it to crystallization, discharging it from the device, and drying it to obtain MFI molecular sieve raw material powder. The crystallization is a once-through crystallization that is carried out directly after premixing and circulation in the supergravity aging-crystallizing integrated device. Furthermore, the supergravity aging-crystallizing integrated device may include a supply system, a reaction system, and a discharge system. Furthermore, the raw gel is supplied through the supply system of the integrated supergravity aging-crystallization apparatus, then premixed, circulated, and crystallized in the reaction system, and then discharged from the apparatus through the discharge system. The rotation speed of the supergravity reactor can be 0 to 3000 rpm, preferably 1000 to 2500 rpm, or 1000 to 2000 rpm. The raw gel can be supplied to the integrated supergravity aging-crystallization apparatus at a supply rate of 10 to 2000 mL / min, preferably 15 to 300 mL / min. The supergravity reactor can be operated at a flow rate of 10 mL / min to 5000 mL / min, preferably 20 mL / min to 1000 mL / min, for a time period of 0.5 to 15 hours. Crystallization can be carried out at a temperature of 80 to 180°C for a time period of 5 minutes to 24 hours. Synthesis of molecular sieve raw powder in the integrated supergravity aging-crystallization apparatus increases the specific surface area of ​​the catalyst.

[0028] Furthermore, in the preparation of the MFI molecular sieve raw material powder, washing and drying are carried out after the crystallization. Washing may be carried out with deionized water. Drying may be carried out at a drying temperature of 80 to 100°C for a drying time of 10 to 20 hours.

[0029] Furthermore, in the preparation of MFI molecular sieve raw material powder, the boron group element R1 and the nitrogen group element R2 can be directly added to the mother liquor for molecular sieve synthesis, and the novel MFI molecular sieve can be obtained in one step without the need for impregnation and post-treatment.

[0030] Furthermore, in step 2, the binder may be a silicon compound or a mixture of a silicon compound and an aluminum compound. The aluminum compound may be at least one selected from the group consisting of alumina and aluminum sol, and the silicon compound may be at least one selected from the group consisting of white carbon black and silica sol. Based on the total weight of alumina and silica, the binder may be added in an amount of 3% to 50%, preferably 5% to 40%, of the total weight of the molecular sieve raw material powder and the binder. In the present invention, preferably, the aluminum sol and / or silica sol may contain water as its solvent.

[0031] Furthermore, in step 2, molding may be performed by any conventional method, such as extrusion molding into a strip. For example, when the binder is white carbon black or a mixture of white carbon black and alumina, an appropriate amount of water may be added during molding as needed. Drying may be performed at a drying temperature of 80 to 120°C, preferably 90 to 100°C, for 5 to 10 hours, preferably 6 to 8 hours.

[0032] Furthermore, in step 3, the catalyst particles obtained in step 2 may be placed in an atmosphere of template T3 and subjected to hydrothermal crystallization at a temperature of 100 to 200°C, preferably 120 to 150°C, for 12 to 180 hours, preferably 24 to 32 hours.

[0033] Furthermore, in step 3, template T3 may be at least one of aqueous ammonia, ethylamine, ethylenediamine, triethylamine, n-butylamine, hexamethylenediamine, tetrapropylammonium bromide, and tetrapropylammonium hydroxide. The template atmosphere may be generated by volatilizing an aqueous solution of template T3 under autogenous pressure in a closed system. The aqueous solution of template T3 may have a weight concentration of 0.5 to 40%, preferably 2 to 30%. The aqueous solution of template T3 and the catalyst particles may be in a weight ratio of 1:1 to 5:1.

[0034] Furthermore, in step 3, after hydrothermal crystallization, the resulting product is washed, dried, and subjected to a first calcination. Washing may be performed with deionized water. Drying may be performed at a drying temperature of 80 to 100°C, preferably 90 to 100°C, for 10 to 20 hours, preferably 12 to 16 hours. The first calcination may be performed at a calcination temperature of 500 to 650°C, preferably 530 to 600°C, for 8 to 15 hours, preferably 10 to 12 hours.

[0035] Furthermore, in step 3, the ammonium exchange must be carried out in an aqueous solution of an ammonium salt, and the ammonium salt may be one or more selected from the group consisting of ammonium chloride, ammonium nitrate, and ammonium sulfate. The aqueous solution of ammonium salt may contain 5% to 10% by weight of ammonium salt. The ammonium exchange may be carried out at a temperature of 80 to 90°C and may be repeated 3 to 6 times. The product obtained after the ammonium exchange may be subjected to a second calcination, which may be carried out at a calcination temperature of 500 to 600°C for 4 to 8 hours.

[0036] As will be appreciated by those skilled in the art, for MFI molecular sieve catalysts according to the present disclosure, calcination can remove raw materials such as templates. Therefore, the hydroxyl group at 3400-3500 cm shown in the infrared spectrum of the catalyst can be removed. -1The characteristic hydroxyl peak between does not correspond to other raw materials such as template added during the preparation, but is indicative of the MFI molecular sieve catalyst.

[0037] In a further aspect, the disclosure provides the use of an MFI molecular sieve catalyst in the production of propylene and ethylene via catalytic cracking of olefins.

[0038] Furthermore, the production of propylene and ethylene through catalytic cracking of olefins can be carried out by contacting an olefin feedstock with the above-mentioned MFI molecular sieve catalyst and reacting them to obtain the products propylene and ethylene.

[0039] Furthermore, the above production may be carried out by using at least one of C4-C6 olefins as a raw material under the following conditions: a reaction temperature of 400 to 600°C, preferably 420 to 580°C, a reaction pressure of 0 to 0.3 MPa, preferably 0.01 to 0.2 MPa, and a reaction time of 1 to 50 hours. -1 , preferably 2 to 40 hours -1 Weight space velocity.

[0040] Compared with the prior art, the present invention may have the following advantages:

[0041] The present disclosure provides an MFI molecular sieve, a particle catalyst containing the MFI molecular sieve, and an MFI molecular sieve catalyst containing the MFI molecular sieve. The ratio of the content of monoclinic crystal form to orthorhombic crystal form is within a predetermined range, and the hydroxyl group infrared spectrum of the catalyst is 3400 to 3500 cm. -1Since the MFI molecular sieve catalyst according to the present disclosure exhibits a characteristic hydroxyl group peak at 1000 MPa, when used to produce propylene and ethylene via catalytic cracking, it has high stability, high conversion of olefin feedstock, and high overall selectivity to the product propylene and ethylene. Furthermore, the catalyst according to the present disclosure has a larger specific surface area than existing catalysts in the art, thereby further improving the conversion of olefin feedstock.

[0042] [Drawing Description] FIG. 1 is an XRD spectrum of the catalyst obtained in Example 1; FIG. 2 is an infrared spectrum of the hydroxyl group of the catalyst obtained in Example 1; FIG. 3 is an XRD spectrum of the catalyst obtained in Example 3; FIG. 4 is an XRD spectrum of the catalyst obtained in Comparative Example 1; FIG. 5 is an infrared spectrum of the hydroxyl group of the catalyst obtained in Comparative Example 2.

[0043] [Detailed explanation] The present invention is further illustrated by the following examples.

[0044] In this study, the specific surface area was measured using a TriStar 3000 physical adsorption apparatus. After vacuum treatment at 300°C for 3 hours, the sample was placed in the apparatus and liquid nitrogen was added for testing. The Barret-Joyner-Halenda (BJH) model was used to calculate the specific surface area of ​​the sample.

[0045] In this disclosure, XRD analysis was performed on a Rigaku D / MAX-1400X polycrystalline X-ray diffractometer under the following conditions: graphite monochromator, Cu Kα radiation, 40 kV tube voltage, 40 mA tube current, and a scan range of 2θ from 2 to 70°. The XRD data were refined using software to calculate the lattice constants and the ratio of the orthorhombic to monoclinic crystal forms of the catalysts.

[0046] In this disclosure, the molar ratio of SiO2 / Al2O3 was calculated based on the elemental composition of the solid sample analyzed by using a Magix X-ray fluorescence spectrometer manufactured by Philips, The Netherlands, operated at a voltage of 40 kV and a current of 40 mA.

[0047] In the examples and comparative examples, the production of propylene and ethylene via catalytic cracking is carried out by using at least one of C4-C6 olefins as a feedstock, wherein: Conversion rate of olefin feed (%) = (1 - weight of olefin in product / weight of olefin in feed) × 100%; Selectivity (%) of the two olefin products = total weight of propylene and ethylene obtained in the product / (weight of olefins in the feed - weight of olefins remaining after the reaction) x 100%.

[0048] In this disclosure, the software used for refinement was Topas software, and the refinement method was the Rietveld full pattern fitting method for crystal structure refinement. As known in the art, Rietveld refinement is primarily used to obtain information such as a sample's crystal structure and phase composition from its XRD spectrum. As an example, a model of the sample's initial structure was first established (e.g., using a known model from the International Molecular Sieve Association's molecular sieve structure database). Then, by continuously adjusting the model parameters (atomic coordinates, temperature coefficients, unit cell parameters, peak parameters, background parameters, proportionality coefficients, etc., as known in the art), the XRD spectrum calculated from the initial structure gradually approached the actual spectrum. When the difference between the calculated spectrum and the actual spectrum becomes small to a certain extent (e.g., Rwp<10.0% as a convergence criterion), the crystal structure at this time can be considered accurate, and the atomic coordinates, unit cell parameters, proportionality coefficients, etc. contained therein can be considered to be actual values, where the proportionality coefficients represent the compositions of various phases in the molecular sieve. Those skilled in the art could adjust and determine the specific refinement based on their expertise and various factors of Rietveld refinement known in the art. The Rietveld refinement in this disclosure was performed with GSAS software (see, e.g., Larson, A.; Von Dreele, RB General Structure Analysis System GSAS; Los Alamos National Laboratory: Los Alamos, NM, 1996).

[0049] In this disclosure, when calculating the peak area and its ratio in the infrared spectrum of the hydroxyl group, the integrated area is emphasized, and the line connecting the two lowest points on the characteristic peak curve of the spectrum is used as the starting reference line for integration. After peak division, the peak area is integrated, and the center is around the position of wavenumber 3450, and the half width is 286 cm. -1 The peak area of ​​the peak having the characteristic hydroxyl group was calculated, and the proportion was 86%.-1 The integration was performed by centering the wavenumber around the maximum point and using the line connecting the two lowest points of the spectrum curve as the starting reference line, and the peak area of ​​the characteristic peak with a half-width of 210 to 240 and the total area of ​​the characteristic peak curve were calculated, and then the ratio of the peak area of ​​the characteristic peak with a half-width of 210 to 240 to the total area was calculated.

[0050] [Example 1] Step 1: Preparation of molecular sieve raw material powder A silicon source, an aluminum source, templates T1 and T2, and water were mixed to obtain a raw gel. A total volume of 1 L of raw gel was supplied to the supergravity integrator through the supply system of the supergravity integrator at a supply rate of 50 mL / min. The silicon source was silica sol, the aluminum source was aluminum sulfate, the template T1 was TPABr, and the template T2 was phthalimide. Furthermore, a boron group element R1 (Ga) and a nitrogen group element R2 (P) were added, where the Ga source was GaCl3 and the P source was H3PO4. The molar ratios of the silicon source, aluminum source, template, and water were: HO / SiO2 = 20; Si / Al = 300; T1 / SiO2 = 0.05; R1 / SiO2 = 0.03; R2 / SiO2 = 0.02, and the ratio of T1 to T2 was adjusted to T2 / T1 = 1.2. The raw gel was circulated through the reaction system of the integrated supergravity aging and crystallization apparatus, where the rotation speed of the supergravity reactor was 1500 rpm, the flow rate was 100 mL / min, and the residence time was 5 hours. This procedure resulted in homogeneous mixing of the gel. The raw material after premixing and circulation was directly crystallized. After once-through crystallization at 170 °C for 12 hours in the supergravity reactor, the reaction was stopped. After cooling to room temperature, the product was removed from the integrated apparatus through the discharge system, washed and centrifuged three times, and dried at 80 °C for 12 hours to obtain ZSM-5 molecular sieve raw powder.

[0051] Step 2: Preparation of catalyst particles 100 g of the above ZSM-5 molecular sieve raw material powder, 20 g of silica sol containing 40 wt % SiO2, and 0.06 g of alumina were kneaded, extruded into strips, and dried at 80°C for 10 hours to obtain catalyst particles.

[0052] Step 3: Preparation of ZSM-5 molecular sieve The resulting catalyst particles were placed in an atmosphere of Template T3, a 10% ethylenediamine solution, and subjected to vapor-solid hydrothermal crystallization at 130°C for 112 hours. The Template T3 atmosphere was generated by volatilizing an aqueous solution containing Template T3 ethylenediamine under autogenous pressure in a closed system. The weight ratio of Template T3 ethylenediamine aqueous solution to catalyst particles was 1.5. After hydrothermal crystallization, the product was removed, washed with distilled water, dried at 90°C for 15 hours, and then calcined in an air atmosphere at 550°C for 10 hours.

[0053] The calcined product was subjected to ammonium exchange three times at 90°C in a 5 wt% ammonium nitrate solution, dried, and calcined in a muffle furnace at 500°C for 4 hours to obtain a ZSM-5 molecular sieve catalyst.

[0054] The obtained ZSM-5 molecular sieve catalyst was characterized by XRD, as shown in Figure 1. The XRD data was refined by software to calculate the lattice constant. The results showed that the catalyst had monoclinic and orthorhombic crystal forms in a ratio of 8:1 and a binder content of less than 0.2%. Characterization of the catalyst by nitrogen adsorption / desorption revealed that the specific surface area of ​​the catalyst was 420 cm 2 / g. Analysis by X-ray fluorescence analysis revealed that the SiO2 / Al2O3 molar ratio of the catalyst was 298. The obtained catalyst contained ZSM-5 molecular sieve at a weight fraction of 98.9%, Ga element at a weight fraction of 0.5%, P element at a weight fraction of 0.5%, and the remainder was a binder.

[0055] Figure 2 shows the infrared spectrum of the hydroxyl group of the catalyst. The infrared spectrum of the hydroxyl group of the catalyst is shown in the range of 3400-3500 cm.-1 After peak division, the peak was centered around the wavenumber 3450 position and had a half-width of 286 cm -1 When the peak area was integrated to determine the peak area of ​​the characteristic peak having the formula:

[0056] The catalyst was evaluated for its activity in producing propylene and ethylene through catalytic cracking of olefins in a fixed-bed catalytic reactor using a mixed C4 (40 wt% butane and 60 wt% butene) feedstock from an ethylene plant. The catalyst loading was 3 g, the reaction temperature was 530°C, the reaction pressure was 0.03 MPa, and the weight hourly space velocity was 20 h -1 The reaction was carried out under the conditions of 100°C / 200°F. As a result, the conversion of C4 olefins was 79%, and the selectivity for propylene and ethylene was 81%. After 80 hours of operation, the activity and selectivity of the catalyst remained essentially unchanged, indicating good stability.

[0057] [Example 2] Step 1: Preparation of molecular sieve raw material powder The silicon source, aluminum source, templates T1 and T2, and water were mixed to obtain a raw gel. The raw gel was fed into the supergravity integrated device through its supply system at a feed rate of 50 mL / min. The silicon source was silica sol, the aluminum source was aluminum sulfate, the template T1 was TPABr, and the template T2 was phthalimide. The silicon source, aluminum source, template, and water had a molar ratio of H2O / SiO2 = 20; Si / Al = 300; T1 / SiO2 = 0.05; the ratio of T1 to T2 was adjusted to T2 / T1 = 1.2. The raw gel was circulated through the reaction system of the supergravity aging-crystallization integrated device, where the rotation speed of the supergravity reactor was 1500 rpm, the flow rate was 100 mL / min, and the residence time was 5 hours. This procedure ensured uniform mixing of the gel. The raw materials after premixing and circulation were directly crystallized. After the once-through crystallization was performed in the supergravity reactor at 170°C for 12 hours, the reaction was stopped. After cooling to room temperature, the product was taken out of the integrated device through the discharge system, washed and centrifuged three times, and dried at 80°C for 12 hours to obtain ZSM-5 molecular sieve raw powder.

[0058] Step 2: Preparation of catalyst particles 100 g of the above ZSM-5 molecular sieve raw material powder, 20 g of silica sol containing 40 wt % SiO2, and 0.06 g of alumina were kneaded, extruded into strips, and dried at 80°C for 10 hours to obtain catalyst particles.

[0059] Step 3: Preparation of ZSM-5 molecular sieve The resulting catalyst particles were placed in an atmosphere of Template T3, a 30% ethylenediamine solution, and subjected to vapor-solid hydrothermal crystallization at 130°C for 112 hours. The Template T3 atmosphere was generated by volatilizing an aqueous solution containing Template T3 ethylenediamine under autogenous pressure in a closed system. The weight ratio of Template T3 ethylenediamine aqueous solution to catalyst particles was 1.5. After hydrothermal crystallization, the product was removed, washed with distilled water, dried at 90°C for 15 hours, and then calcined in an air atmosphere at 550°C for 10 hours.

[0060] This product was subjected to ammonium exchange three times in a 5 wt % ammonium nitrate solution at 90°C, dried, and calcined in a muffle furnace at 500°C for 4 hours to obtain a ZSM-5 molecular sieve catalyst.

[0061] The resulting ZSM-5 molecular sieve catalyst was characterized by XRD, and the XRD data was refined with software to calculate the lattice constant. The results showed that the catalyst had monoclinic and orthorhombic crystal forms in a ratio of 8:1 and a binder content of less than 0.2%. Characterization of the catalyst by nitrogen adsorption / desorption revealed that the specific surface area of ​​the catalyst was 410 cm. 2 / g. Analysis by a fluorescent X-ray analyzer revealed that the SiO2 / Al2O3 molar ratio of the catalyst was 304. The obtained catalyst contained ZSM-5 molecular sieve at a weight fraction of 99.9%, with the remainder being a binder.

[0062] The hydroxyl group infrared spectrum of the catalyst is 3400 to 3500 cm -1 After peak division, the peak was centered around the wavenumber 3448 and had a half-width of 272 cm -1 When the peak area of ​​the characteristic peak having the formula (I) was integrated to determine the peak area, the peak area accounted for 82%.

[0063] The catalyst was evaluated for its activity in producing propylene and ethylene through catalytic cracking of olefins in a fixed-bed catalytic reactor using a mixed C4 (40 wt% butane and 60 wt% butene) feedstock from an ethylene plant. The catalyst loading was 3 g, the reaction temperature was 530°C, the reaction pressure was 0.03 MPa, and the weight hourly space velocity was 20 h -1 The catalyst was operated under the conditions of 100°C / 200°F. As a result, the conversion of C4 olefins was 78%, and the selectivity for propylene and ethylene was 80%. After 80 hours of operation, the activity and selectivity of the catalyst remained substantially unchanged, indicating good stability.

[0064] Example 3 Step 1: Preparation of molecular sieve raw material powder A silicon source, an aluminum source, templates T1 and T2, and water were mixed to obtain a raw gel. The raw gel was fed to the supergravity integrated device through its supply system at a feed rate of 50 mL / min. The silicon source was silica sol, the aluminum source was aluminum sulfate, the template T1 was TPABr, and the template T2 was naphthalenediamine. Furthermore, a boron group element R1 (Ga) and a nitrogen group element R2 (P) were added, where the Ga source was GaCl3 and the P source was H3PO4. The molar ratios of the silicon source, aluminum source, template, and water were: HO / SiO2 = 20; Si / Al = 300; T1 / SiO2 = 0.05; R1 / SiO2 = 0.03; R2 / SiO2 = 0.02, and the ratio of T1 to T2 was adjusted to T2 / T1 = 3. The raw gel was circulated through the reaction system of the supergravity integrated device for aging and crystallization. The supergravity reactor rotation speed was 1500 rpm, the flow rate was 100 mL / min, and the residence time was 5 hours. This procedure resulted in a uniformly mixed gel. The raw materials were then directly crystallized after premixing and circulation. Once-through crystallization was carried out in the supergravity reactor at 170°C for 12 hours, after which the reaction was stopped. After cooling to room temperature, the product was removed from the integrated device through the discharge system, washed and centrifuged three times, and dried at 80°C for 12 hours to obtain ZSM-5 molecular sieve raw material powder.

[0065] Step 2: Preparation of catalyst particles 100 g of the above ZSM-5 molecular sieve raw material powder, 20 g of silica sol containing 40 wt % SiO2, and 0.06 g of alumina were kneaded, extruded into strips, and dried at 80°C for 10 hours to obtain catalyst particles.

[0066] Step 3: Preparation of ZSM-5 molecular sieve The resulting catalyst particles were placed in an atmosphere of Template T3, a 20% ethylenediamine solution, and subjected to vapor-solid hydrothermal crystallization at 130°C for 112 hours. The Template T3 atmosphere was generated by volatilizing an aqueous solution containing Template T3 ethylenediamine under autogenous pressure in a closed system. The weight ratio of Template T3 ethylenediamine aqueous solution to catalyst particles was 1.5. After hydrothermal crystallization, the product was removed, washed with distilled water, dried at 90°C for 15 hours, and then calcined in an air atmosphere at 550°C for 10 hours.

[0067] The product was subjected to ammonium exchange three times at 90°C in a 5 wt% ammonium nitrate solution, dried, and calcined in a muffle furnace at 500°C for 4 hours to obtain a ZSM-5 molecular sieve catalyst.

[0068] The obtained ZSM-5 molecular sieve catalyst was characterized by XRD, as shown in Figure 3. The XRD data was refined by software to calculate the lattice constant. The results showed that the catalyst had monoclinic and orthorhombic crystal forms in a ratio of 10:1 and a binder content of less than 0.2%. Characterization of the catalyst by nitrogen adsorption / desorption revealed that the specific surface area of ​​the catalyst was 400 cm 2 Analysis by X-ray fluorescence analysis revealed that the SiO2 / Al2O3 molar ratio of the catalyst was 297.

[0069] The hydroxyl group infrared spectrum of the catalyst is 3400-3500 cm -1 After peak division, the peak was centered around the wavenumber 3453 and had a half-width of 284 cm -1 When the peak area was integrated to determine the peak area of ​​the characteristic peak having the formula:

[0070] The obtained catalyst contained ZSM-5 molecular sieve at a weight fraction of 98.8%, Ga element at a weight fraction of 0.6%, P element at a weight fraction of 0.5%, and the remainder was a binder.

[0071] The catalyst was evaluated for its activity in producing propylene and ethylene through catalytic cracking of olefins in a fixed-bed catalytic reactor using a mixed C4 (40 wt% butane and 60 wt% butene) feedstock from an ethylene plant. The catalyst loading was 3 g, the reaction temperature was 530°C, the reaction pressure was 0.03 MPa, and the weight hourly space velocity was 20 h -1 The reaction was carried out under the conditions of 1. As a result, the conversion of C4 olefins was 77%, and the selectivity for propylene and ethylene was 79%. After the catalyst was operated for 80 hours, the activity and selectivity of the catalyst did not decrease substantially.

[0072] [Comparative Example 1] Step 1: Preparation of molecular sieve raw material powder A silicon source, an aluminum source, template T1, and water were mixed to obtain a raw gel. The raw gel was fed into the supergravity integrated device through its supply system at a feed rate of 50 mL / min. The silicon source was silica sol, the aluminum source was aluminum sulfate, and template T1 was TPABr. Furthermore, a boron group element R1 (Ga) and a nitrogen group element R2 (P) were added, where the Ga source was GaCl3 and the P source was H3PO4. The molar ratios of the silicon source, aluminum source, template, and water were: H2O / SiO2 = 20; Si / Al = 300; T1 / SiO2 = 0.11; R1 / SiO2 = 0.03; R2 / SiO2 = 0.02. The raw gel was circulated through the reaction system of the supergravity integrated device. The rotation speed of the supergravity reactor was 1500 rpm, the flow rate was 100 mL / min, and the residence time was 5 hours. This procedure resulted in a uniformly mixed gel. The premixed and recycled raw materials were directly crystallized. Once-through crystallization was performed in the supergravity reactor at 170°C for 12 hours, after which the reaction was stopped. After cooling to room temperature, the product was removed from the integrated device through the discharge system, washed and centrifuged three times, and then dried at 80°C for 12 hours to obtain ZSM-5 molecular sieve raw material powder.

[0073] Step 2: Preparation of catalyst particles 100 g of the above ZSM-5 molecular sieve raw material powder, 20 g of silica sol containing 40 wt % SiO2, and 0.06 g of alumina were kneaded, extruded into strips, and dried at 80°C for 10 hours to obtain catalyst particles.

[0074] Step 3: Preparation of ZSM-5 molecular sieve The resulting catalyst particles were placed in an atmosphere of Template T3, a 10% ethylenediamine solution, and subjected to vapor-solid hydrothermal crystallization at 130°C for 112 hours. The Template T3 atmosphere was generated by volatilizing an aqueous solution containing Template T3 ethylenediamine under autogenous pressure in a closed system. The weight ratio of Template T3 ethylenediamine aqueous solution to catalyst particles was 1.5. After hydrothermal crystallization, the product was removed, washed with distilled water, dried at 90°C for 15 hours, and then calcined in an air atmosphere at 550°C for 10 hours.

[0075] The product was subjected to ammonium exchange three times at 90°C in a 5 wt% ammonium nitrate solution, dried, and calcined in a muffle furnace at 500°C for 4 hours to obtain a ZSM-5 molecular sieve catalyst.

[0076] The obtained ZSM-5 molecular sieve catalyst was characterized by XRD, as shown in Figure 4. The XRD data was refined by software to calculate the lattice constant. The results showed that the catalyst had an orthorhombic crystal form with a 100% content and a binder content of less than 0.2%. Characterization of the catalyst by nitrogen adsorption / desorption revealed that the specific surface area of ​​the catalyst was 200 cm 2 / g. Analysis by X-ray fluorescence analysis revealed that the SiO2 / Al2O3 molar ratio of the catalyst was 296. The obtained catalyst contained ZSM-5 molecular sieve at a weight fraction of 98.9%, Ga element at a weight fraction of 0.5%, and P element at a weight fraction of 0.5%.

[0077] The hydroxyl group infrared spectrum of the catalyst is 3400-3500 cm -1 No peak characteristic of hydroxyl groups was observed.

[0078] The catalyst was evaluated for its activity in producing propylene and ethylene through catalytic cracking of olefins in a fixed-bed catalytic reactor using a mixed C4 (40 wt% butane and 60 wt% butene) feedstock from an ethylene plant. The catalyst loading was 3 g, the reaction temperature was 530°C, the reaction pressure was 0.03 MPa, and the weight hourly space velocity was 20 h -1 The catalyst was operated under the conditions of 1. As a result, the conversion of C4 olefins was 59%, and the selectivity for propylene and ethylene was 60%. After the catalyst was operated for 80 hours, the activity and selectivity of the catalyst were obviously decreased.

[0079] Comparative Example 2 Step 1: Preparation of molecular sieve raw material powder A silicon source, an aluminum source, template T2, and water were mixed to obtain a raw gel. The raw gel was fed into the supergravity integrated device through its supply system at a feed rate of 50 mL / min. The silicon source was silica sol, the aluminum source was aluminum sulfate, and T2 was phthalimide. Furthermore, a boron group element R1 (Ga) and a nitrogen group element R2 (P) were added, where the Ga source was GaCl3 and the P source was H3PO4. The molar ratios of the silicon source, aluminum source, template, and water were: H2O / SiO2 = 20; Si / Al = 300; T2 / SiO2 = 0.11; R1 / SiO2 = 0.03; R2 / SiO2 = 0.02. The raw gel was circulated through the reaction system of the supergravity ripening-crystallization integrated device, where the rotation speed of the supergravity reactor was 1500 rpm, the flow rate was 100 mL / min, and the residence time was 5 hours. This procedure resulted in a uniformly mixed gel. The premixed and recycled raw materials were directly crystallized. Once-through crystallization was performed in a supergravity reactor at 170°C for 12 hours, after which the reaction was stopped. After cooling to room temperature, the product was removed from the integrated device through the discharge system, washed and centrifuged three times, and dried at 80°C for 12 hours to obtain an amorphous powder that failed to form a molecular sieve catalyst.

[0080] Comparative Example 3 Step 1: Preparation of molecular sieve raw material powder A silicon source, an aluminum source, template T1, and water were mixed to obtain a raw gel. The raw gel was fed into the supergravity integrated device through its supply system at a feed rate of 50 mL / min. The silicon source was silica sol, the aluminum source was aluminum sulfate, and template T1 was TPABr. Furthermore, a boron group element R1 (Ga) and a nitrogen group element R2 (P) were added, where the Ga source was GaCl3 and the P source was H3PO4. The molar ratios of the silicon source, aluminum source, template, and water were: H2O / SiO2 = 20, Si / Al = 300, T1 / SiO2 = 0.11, R1 / SiO2 = 0.03, and R2 / SiO2 = 0.02. The raw gel was circulated through the reaction system of the supergravity ripening-crystallization integrated device, where the rotation speed of the supergravity reactor was 1500 rpm, the flow rate was 100 mL / min, and the residence time was 5 hours. This procedure resulted in a uniformly mixed gel. The premixed and recycled raw materials were directly crystallized. Once-through crystallization was performed in the supergravity reactor at 170°C for 12 hours, and then the reaction was stopped. After cooling to room temperature, the product was removed from the integrated device through the discharge system, washed, centrifuged three times, and dried at 80°C for 12 hours to obtain ZSM-5 molecular sieve raw material powder.

[0081] Step 2: Preparation of catalyst particles 100 g of the above ZSM-5 molecular sieve raw material powder, 20 g of silica sol containing 40 wt % SiO2, and 0.06 g of alumina were kneaded, extruded into strips, and dried at 80°C for 10 hours to obtain catalyst particles.

[0082] Step 3: Preparation of ZSM-5 molecular sieve The resulting catalyst particles were subjected to conventional treatment with water vapor and hydrothermal calcination at 550° C. for 4 hours.

[0083] The product was subjected to ammonium exchange three times at 90°C in a 5 wt% ammonium nitrate solution, dried, and then calcined in a muffle furnace at 500°C for 4 hours to obtain a ZSM-5 molecular sieve catalyst.

[0084] The resulting ZSM-5 molecular sieve catalyst was characterized by XRD, and the XRD data were refined using software to calculate the lattice constant. The results showed that the catalyst had monoclinic and orthorhombic crystal forms in a ratio of 50:1. Characterization of the catalyst by nitrogen adsorption / desorption revealed that the specific surface area of ​​the catalyst was 200 cm 2 / g. Analysis by X-ray fluorescence analysis revealed that the SiO2 / Al2O3 molar ratio of the catalyst was 301. The obtained catalyst contained ZSM-5 molecular sieve at a weight fraction of 90%, Ga element at a weight fraction of 0.5%, and P element at a weight fraction of 0.5%.

[0085] The hydroxyl group infrared spectrum of the obtained catalyst is shown in Figure 5. The hydroxyl group infrared spectrum of the catalyst has a peak at 3400 to 3500 cm -1 No peak characteristic of hydroxyl groups was observed.

[0086] The catalyst was evaluated for its activity in producing propylene and ethylene through catalytic cracking of olefins in a fixed-bed catalytic reactor using a mixed C4 (40 wt% butane and 60 wt% butene) feedstock from an ethylene plant. The catalyst loading was 3 g, the reaction temperature was 530°C, the reaction pressure was 0.03 MPa, and the weight hourly space velocity was 20 h -1 The catalyst was operated under the conditions of 100°C / 200°F. As a result, the conversion of C4 olefins was 62%, and the selectivity for propylene and ethylene was 59%. After operating this catalyst for 80 hours, the activity and selectivity of the catalyst clearly decreased.

[0087] For ease of comparison, the main treatment conditions and results are shown in Table 1.

[0088] [Table 1]

[0089] The embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Various simple modifications can be made to the embodiments of the present invention, including combining various technical features in other appropriate ways, within the technical scope of the present invention. These simple modifications and combinations are also the contents disclosed in this specification and should be considered to be within the protection scope of the present disclosure. [Brief explanation of the drawings]

[0090] [Figure 1] FIG. 1 is an XRD spectrum of the catalyst obtained in Example 1. [Figure 2] FIG. 2 is an infrared spectrum of the hydroxyl group of the catalyst obtained in Example 1. [Figure 3] FIG. 3 is an XRD spectrum of the catalyst obtained in Example 3. [Figure 4] FIG. 4 is an XRD spectrum of the catalyst obtained in Comparative Example 1. [Figure 5] FIG. 5 is an infrared spectrum of the hydroxyl group of the catalyst obtained in Comparative Example 2.

Claims

1. MFI molecular sieves having the following characteristics: Each unit mass of the MFI molecular sieve contains both monoclinic and orthorhombic crystal forms of the MFI molecular sieve; the MFI molecular sieve has a hydroxyl group infrared spectrum of 3400 to 3500 cm －１ The characteristic peak of the hydroxyl group is at 3420 to 3480 cm －１ and the peak area of ​​the characteristic peak having a maximum point at a position between 210 and 240 and centered around the maximum point and having a half-width of 210 to 240 accounts for 70% or more of the total peak area; and the MFI molecular sieve contains the elements Si, Al and O, but does not contain the element Ti.

2. 2. The MFI molecular sieve according to claim 1, characterized in that each unit mass of said MFI molecular sieve contains monoclinic and orthorhombic crystalline forms in a molar ratio of 5-100, preferably 6-50.

3. The MFI molecular sieve has a hydroxyl group infrared spectrum of 3460 to 3470 cm －１ 2. The MFI molecular sieve of claim 1, characterized in that it exhibits an absorption peak with a maximum intensity at

4. The MFI molecular sieve is SiO ２ / Al ２ O ３ 2. The MFI molecular sieve according to claim 1, characterized in that the molar ratio of

5. Catalyst particles comprising: A) the MFI molecular sieve according to any one of claims 1 to 3; B) at least two different templates T1 and T2; and C) Binder.

6. 6. The catalyst particle according to claim 5, wherein the template T1 is at least one of tetrapropylammonium bromide, tetrapropylammonium hydroxide, tetramethylammonium bromide, tetraethylammonium bromide, tetrabutylammonium bromide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide; and / or the template T2 is at least one of phthalimide, taurine, and naphthalenediamine.

7. 6. The catalyst particles of claim 5, wherein the binder is a silicon compound or a mixture of a silicon compound and an aluminum compound; wherein the aluminum compound is at least one selected from the group consisting of alumina and aluminum sol, and the silicon compound is at least one selected from the group consisting of white carbon black and silica sol; and the binder is added in an amount of 3% to 50% of the total weight of the molecular sieve raw material powder and the binder, based on the total weight of alumina and silica.

8. MFI molecular sieve catalyst, including: a) the MFI molecular sieve according to any one of claims 1 to 3; optionally, b) a boron group element R1; and Optionally, c) a nitrogen group element R2.

9. The MFI molecular sieve catalyst is 200 to 1000 m ２ 9. The MFI molecular sieve catalyst according to claim 8, characterized in that it has a specific surface area of ​​1 / g.

10. The MFI molecular sieve catalyst according to claim 8, wherein the molecular sieve is a hydrogen-type molecular sieve.

11. 9. The MFI molecular sieve catalyst of claim 8, characterized in that the MFI molecular sieve catalyst comprises, based on the weight of the MFI molecular sieve catalyst: a) the MFI molecular sieve in an amount of 90 to 100%, preferably 92 to 99%; b) a boron group element R1 in an amount of 0 to 5%, preferably 0.5 to 3.0%; and c) Nitrogen group element R2 in an amount of 0 to 5%, preferably 0.5 to 5.0%.

12. The MFI molecular sieve catalyst according to claim 8, characterized in that in the MFI molecular sieve catalyst, the boron group element R1 is at least one selected from the group consisting of B and Ga; and / or the nitrogen group element R2 is at least one selected from the group consisting of N, P, As, Sb and Bi.

13. 9. The MFI molecular sieve catalyst of claim 8, wherein the MFI molecular sieve catalyst further comprises a binder; the binder is present in an amount of 5 wt. % or less based on the weight of the catalyst.

14. The MFI molecular sieve catalyst according to any one of claims 8 to 13, characterized in that the MFI molecular sieve catalyst is obtained by subjecting the catalyst particles according to any one of claims 5 to 7 to a treatment including hydrothermal crystallization in an atmosphere of template T3.

15. A method for preparing the MFI molecular sieve catalyst of any one of claims 8 to 14, comprising the steps of: Step 1: Preparing MFI molecular sieve raw material powder; Step 2: Mixing the molecular sieve raw material powder obtained in step 1 with a binder, optionally adding water, and then kneading, molding, and drying to obtain catalyst particles; Step 3: The catalyst particles obtained in step 2 are subjected to hydrothermal crystallization under the atmosphere of template T3, and then subjected to first calcination, ammonium exchange and second calcination to obtain the MFI molecular sieve catalyst.

16. 16. The method according to claim 15, wherein in step 1, at least two different templates T1 and T2 are used; preferably, T1 and T2 are in a molar ratio of T2 / T1=0.01-30.

17. Step 1 includes preparing a raw material gel by mixing a silicon source, an aluminum source, the template T1, the template T2, water, and optionally a boron group element R1 and / or optionally a nitrogen group element R2; wherein the silicon source, the aluminum source, the template, the boron group element, the nitrogen group element, and water are mixed in the following molar ratio: ２ O / SiO ２ =10~500;Si / Al=20~∞;T1 / SiO ２ =0.01~20; R1 / SiO ２ =0~50; R2 / SiO ２ 17. The method of claim 16, wherein: = 0 to 50.

18. 17. The method of claim 16, wherein the template T1 is at least one of tetrapropylammonium bromide, tetrapropylammonium hydroxide, tetramethylammonium bromide, tetraethylammonium bromide, tetrabutylammonium bromide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide; and / or the template T2 is at least one of phthalimide, taurine, and naphthalenediamine.

19. 16. The method of claim 15, wherein in step 2, the binder is a silicon compound or a mixture of a silicon compound and an aluminum compound; wherein the aluminum compound is at least one selected from the group consisting of alumina and aluminum sol, and the silicon compound is at least one selected from the group consisting of white carbon black and silica sol; and the binder is added in an amount of 3% to 50% of the total weight of the molecular sieve raw material powder and the binder, based on the total weight of alumina and silica.

20. 16. The method of claim 15, wherein in step 3, the template T3 is at least one of aqueous ammonia, ethylamine, ethylenediamine, triethylamine, n-butylamine, hexamethylenediamine, tetrapropylammonium bromide, and tetrapropylammonium hydroxide; the template atmosphere is generated by volatilizing an aqueous solution of the template T3 under autogenous pressure in a closed system; the aqueous solution of the template T3 has a weight concentration of 0.5 to 40%, and the weight ratio of the aqueous solution of the template T3 to the catalyst particles is 1 to 5.

21. The method according to claim 15, wherein in step 3, after hydrothermal crystallization, the first calcination is carried out under conditions of a calcination temperature of 500 to 650°C, preferably 530 to 600°C, and a calcination time of 8 to 15 hours, preferably 10 to 12 hours; and / or after ammonium exchange, the second calcination is carried out under conditions of a calcination temperature of 500 to 600°C, and a calcination time of 4 to 8 hours.

22. The method according to claim 15, wherein in step 3, drying is carried out after the hydrothermal crystallization and before the first firing, and the drying is carried out under conditions of a drying temperature of 80 to 100°C, preferably 90 to 100°C, and a drying time of 10 to 20 hours, preferably 12 to 16 hours.

23. Use of the MFI molecular sieve catalyst according to any one of claims 8 to 14 in the production of propylene and ethylene via catalytic cracking of olefins.

24. 1. A process for producing propylene and ethylene via catalytic cracking of olefins, comprising: contacting an olefin feedstock with the MFI molecular sieve catalyst of any one of claims 8 to 14 to react with it to obtain product propylene and ethylene; The reaction is carried out at a reaction temperature of 400 to 600°C, a reaction pressure of 0 to 0.3 MPa, and a weight hourly space velocity of 1 to 50 h －１ The process is carried out by using at least one C4-C6 olefin as a raw material under the conditions of

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