A cross-shaped hollow MFI molecular sieve, a preparation method thereof and application thereof in a catalyst

Abstract

The present application relates to a kind of cross hollow MFI molecular sieve and its preparation method and application in catalyst.The crystal grain of the cross hollow MFI molecular sieve is cross hollow morphology, using seed and template combination under certain feeding step and proportion to prepare mother liquor, by dynamic crystallization synthesis matrix molecular sieve, then by alkali treatment to obtain hollow molecular sieve.The cross hollow MFI can replace existing MFI molecular sieve to prepare catalyst, with good anti-wear performance, can maintain catalytic activity in fluidization process.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts and relates to a cross-shaped hollow MFI molecular sieve catalyst and a preparation method thereof. Background Art

[0002] ZSM-5 molecular sieve, first developed by Mobile Corporation in the United States in 1972, is a novel zeolite with high silica and three-dimensional intersecting straight channels. This zeolite is oleophilic and hydrophobic, with high thermal and hydrothermal stability. Most pores are approximately 0.55 nm in diameter, making it a medium-pore zeolite. Its unique pore structure not only provides spatial confinement for shape-selective catalysis but also offers abundant access and egress channels for reactants and products. It also provides the crystal structure foundation for the preparation of highly selective, active, and resistant to carbon deposition and deactivation industrial catalysts. As a result, it has become one of the most important catalytic materials for shape-selective reactions in the petroleum industry. However, its small micropore size imposes diffusion limitations in reactions involving large molecules. Compared to hierarchical pore molecular sieves and nanocrystals, hollow materials offer significant advantages: regular and controllable wall thickness; adjustable overall particle size; and a large internal hollow cavity, enabling their use as nanoreactors. One method for synthesizing hollow molecular sieves involves treating already synthesized molecular sieves with alkali. However, not all existing molecular sieves can be treated to produce a hollow structure.

[0003] Prior art MFI molecular sieves are used to prepare catalysts, which generally include the steps of mixing the MFI molecular sieve with a carrier component, forming, and drying. For example, for use in fluidized catalytic cracking catalysts, the steps generally include mixing the MFI structured molecular sieve with clay, a binder, and a matrix material, beating the mixture, and spray drying the mixture. The average particle diameter of the resulting catalyst is generally 60-80 microns to provide the catalyst with good fluidization properties. Since the catalyst circulates in the reactor and regenerator at high temperatures, it is required to have good wear resistance. Prior art generally improves the wear resistance of the catalyst by changing the binder, such as adopting a binder with good performance or using more binder. Existing methods do not address how to improve the wear resistance of the catalyst by improving or changing the molecular sieve. Summary of the Invention

[0004] The first, second and third in the first silicon source, second silicon source, third silicon source, first template and second template of the present invention are used to distinguish the substances added in different steps and should not be understood as limiting the properties or functions of the silicon source or template.

[0005] The cross shape mentioned in the present invention means that the projection of the MFI molecular sieve crystal particles in at least one direction is in the shape of a cross.

[0006] The hollow part means that the MFI molecular sieve crystal has a space surrounded by side walls. The space may be enclosed inside the crystal, or may have openings in multiple directions communicating with the outside of the crystal.

[0007] The room temperature is: 20-35°C.

[0008] Grain size refers to the size of the grain at its widest point, which can be obtained by measuring the size of the widest part of the grain projection in the SEM or TEM image of the sample. The average grain size is obtained by selecting 10 arbitrary molecular sieve grains in the SEM or TEM image and calculating their average value. The wall thickness, or shell thickness, of the grain is the thickness of the sidewalls of the hollow structure of the grain. The wall thickness of a single grain can be measured at any point in the TEM image, and the average value of the 10 grains is taken as the wall thickness of the sample.

[0009] The measurement method of thermal wear refers to the standard Q / SH 3360252-2015: The catalyst is purged with 200m / s fluidizing gas at 700°C. The collision and wear between the catalyst particles and the collision and wear between the catalyst and the wall produce fine powder. The fine powder is swept into the fine powder collector by the evaluation gas. The fine powder of 1h and 5h of wear is collected respectively, and the thermal wear index is calculated based on the mass of the fine powder worn out. Thermal wear (5h loss%) = (mass of fine powder in 5h - mass of fine powder in 1h) / (mass of sample - mass of fine powder in 1h) × 100%

[0010] In the present invention, the relative crystallinity of the molecular sieve is based on the XRD standard ZSM-5 molecular sieve standard sample of the Petrochemical Science Research Institute, and the crystallinity of the standard sample is regarded as 100%.

[0011] The technical problem to be solved by the present invention is to provide a cross-shaped hollow structure molecular sieve and a preparation method thereof.

[0012] Another technical problem to be solved by the present invention is to provide an application of a molecular sieve containing the cross-shaped hollow structure.

[0013] The first aspect of the present invention provides a cross-shaped hollow MFI molecular sieve, wherein the crystal particles of the MFI molecular sieve are in a cross-shaped hollow morphology.

[0014] The second aspect of the present invention provides a method for preparing the cross-shaped hollow MFI molecular sieve, the method comprising:

[0015] A. Preparation of seed molecular sieve, comprising the following preparation steps:

[0016] (A1) dissolving a silicon source (referred to as a first silicon source) and a template (referred to as a first template) in water and stirring at 30-60° C. for 2-6 hours; wherein the molar ratio of R / SiO2 is 0.10-0.30 and the molar ratio of H2O / SiO2 is 15-50, wherein R represents the template;

[0017] (A2) hydrothermally dynamically crystallize the product of step (A1) at 140-180° C. for 8-24 hours; the resulting reaction product is referred to as the seed solution.

[0018] B. Preparation of cross-shaped hollow MFI molecular sieve, including the following preparation steps:

[0019] (B1) dissolving an alkali source in water and stirring uniformly to obtain an alkali source solution;

[0020] (B2) mixing an aluminum source with water and stirring uniformly to obtain an aluminum source solution; optionally adding a certain amount of a second template solution and an optional organosilicon source;

[0021] (B3) mixing a silicon source (referred to as a second silicon source) with the alkaline source solution obtained in step (B1), stirring at room temperature for, for example, 10 minutes or more, for example, 10 to 30 minutes, and optionally adding a certain amount of a second template solution and an optional organosilicon source;

[0022] (B4) mixing the product obtained in step (B3) with optional water, and then adding the product obtained in step (B2) under stirring, and stirring at room temperature for more than 10 minutes, for example, 30 to 60 minutes; obtaining a mixed solution, referred to as a first mixed solution; the molar ratio of the first mixed solution is: n(SiO2) / n(Al2O3)=50~200, for example, 50~70, n(MB2O) / n(SiO2)=0.25~0.40, n(H2O) / n(SiO2)=60~100, for example, 80~95; wherein the SiO2 in the ratio refers to the SiO2 of the second silicon source, wherein MB refers to an alkali metal, which is one or more of K, Rb, and Cs.

[0023] (B5) adding the seed solution obtained in step (A2) to the first mixed solution in step (B4), stirring at room temperature for 1 to 6 hours, and optionally adding a certain amount of a second template solution and an optional organosilicon source to obtain a second mixed solution; wherein the SiO2 content from the seed solution accounts for 4 to 10% by mass of the SiO2 content in the second silicon source;

[0024] Wherein at least one of the steps (B2), (B3) or (B5) is added with a template agent solution (referred to as the second template agent) and optionally an organic silicon source (referred to as the third silicon source). Preferably, after adding the optional second template agent and the optional third silicon source in each step, stirring is carried out at 30-60℃, preferably for more than 0.5 hours, for example 0.5-4 hours; the total amount of the second template agent added in (B2), (B3) and / or (B5) (if no second template agent is added in a certain step, the amount of the second template agent added is calculated as 0) and the molar ratio of SiO2 in the second silicon source are 0.02-0.08;

[0025] (B6) hydrothermally dynamically crystallizing the second mixed solution obtained in step (B5) at 140-180℃ for 6-48h;

[0026] (B7) filtering, washing, drying and calcining the product obtained in step (B6) to obtain a parent molecular sieve;

[0027] (B8) mixing the parent molecular sieve obtained in step (B7) with an alkali-containing solution, stirring at 60-90℃ for 20-60min, the alkali content in the alkali-containing solution is 0.4-2.0mol / L; obtaining a solid product; the solid product is a cross-shaped MFI molecular sieve with a hollow structure;

[0028] and optionally (B9) ammonium exchanging the solid product obtained in step (B8) to obtain an H-type cross-shaped hollow MFI molecular sieve.

[0029] The third aspect of the present application provides a wear-resistant MFI molecular sieve catalyst, comprising a carrier material and an MFI molecular sieve, the MFI molecular sieve crystal grains have a cross-shaped morphology.

[0030] The present application also provides a preparation method of the wear-resistant MFI molecular sieve catalyst, comprising the steps of mixing the cross-shaped MFI molecular sieve with a carrier material and water, beating, and spray drying.

[0031] The cross-shaped hollow MFI molecular sieve provided by the present application, due to the cross-shaped morphology of the crystal grains, can improve the wear resistance of the prepared MFI molecular sieve-containing catalyst compared with the existing MFI molecular sieve, and due to the hollow structure, in combination with the cross-shaped morphology, has the effect of high accessibility of active centers.

[0032] The present application uses a method combining low crystal seed addition amount and low template agent to silica ratio to prepare a cross-shaped MFI molecular sieve, and through alkali treatment, a hollow MFI molecular sieve with a cross-shaped morphology is obtained, without the need to use a large amount of template agent and a large amount of crystal seeds, which is conducive to reducing the cost of materials.

[0033] The present invention provides a wear-resistant catalyst containing MFI molecular sieves. Compared with conventional MFI molecular sieve catalysts with the same MFI molecular sieve content, the catalyst has higher wear resistance, thermal wear (5h loss%) can be less than 4.2% by mass, and the catalyst has high mechanical strength. During the catalyst fluidization process, the catalyst activity can be maintained, especially for fluidized processes requiring repeated cyclic reaction regeneration, such as fluidized catalytic cracking / cracking reactions, so that the catalyst performance is relatively stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a transmission electron microscope image of the molecular sieve prepared in Example 1. DETAILED DESCRIPTION

[0035] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0036] The cross-shaped hollow MFI molecular sieve provided by the present invention has an average grain size of 800-1500 nm, for example, 900-1200 nm, has a shell layer and a hollow structure in the shell layer, and the shell layer thickness is 100-400 nm, for example, 150-350 nm.

[0037] The catalyst prepared by combining the cross-shaped hollow MFI molecular sieve and a specific particle size carrier material provided by the present invention has a thermal wear (5h loss%) of less than 4.2%. The specific particle size carrier material is silica sol and / or alumina sol, and the catalyst optionally further contains a matrix, such as one or more of clay, alumina, and an alumina precursor. The average particle size of the alumina sol carrier material is 5 to 50 nm, and the average particle size of the silica sol carrier material is 5 to 20 nm. In the prepared catalyst, the content of the cross-shaped hollow MFI molecular sieve is 20 to 60% by mass on a dry basis, the content of the alumina sol is 10 to 20% by mass as Al2O3, the content of the silica sol is 5 to 10% by mass as SiO2, and the content of the matrix is ​​10-50% by mass, for example, 20-50% by mass.

[0038] The cross-shaped hollow MFI molecular sieve can be an alkali metal type cross-shaped hollow MFI molecular sieve or an H type (ie hydrogen type) cross-shaped hollow MFI molecular sieve.

[0039] According to the preparation method of the cross-shaped hollow MFI molecular sieve of the present invention, the silicon source in step (A1) is one or more of methyl orthosilicate or ethyl orthosilicate, and the template in step (A1) is one or more of tetrapropylammonium hydroxide or tetrapropylammonium bromide.

[0040] According to the method for preparing the cross-shaped hollow MFI molecular sieve of the present invention, the grain size of the seed crystal in step (A2) can be 200 to 800 nm.

[0041] According to the method for preparing the cross-shaped hollow MFI molecular sieve of the present invention, the concentration of the alkali source solution in step (B1) is preferably 10-30% by mass, for example, 15-25% by mass. The alkali source is one or more of potassium hydroxide, rubidium hydroxide, or cesium hydroxide.

[0042] According to the method for preparing the cross-shaped hollow MFI molecular sieve of the present invention, the concentration of the aluminum source solution in step (B2) is preferably 5-20% by mass, for example, 5-15% by mass. The aluminum source can be one or more of aluminum sulfate, aluminum nitrate, or aluminum chloride.

[0043] According to the method for preparing a cross-shaped hollow MFI molecular sieve of the present invention, the second silicon source in step (B3) is preferably a silica sol. The silica sol may be an ammonium silica sol, a sodium silica sol, or a mixture thereof. The SiO2 content in the silica sol is preferably 15 to 45% by mass, for example, 15% by mass, 25% by mass, 30% by mass, 45% by mass, or any two of these values ​​as endpoints.

[0044] According to the preparation method of the cross-shaped hollow MFI molecular sieve of the present invention, an organic silicon source (referred to as a third silicon source) can be added in one or more steps (B2), (B3), and (B5), and the organic silicon source added in step B includes the total amount of the organic silicon source added in steps (B2), (B3), and (B5), and the mass ratio of the total amount of the organic silicon source calculated as SiO2 to the second silicon source calculated as SiO2 is 5:100 to 10:100.

[0045] According to the preparation method of the cross-shaped hollow MFI molecular sieve of the present invention, when the second template and the optional organosilicon source are added in step (B5), they are preferably first added to the seed solution of step (B5), then stirred at 30-60°C for 0.5-4 hours, and then added to the first mixed solution obtained in step (B4).

[0046] According to the preparation method of the cross-shaped hollow MFI molecular sieve of the present invention, the organic silicon source is one or more of methyl orthosilicate or ethyl orthosilicate; the template agent (second template agent) in step B is one or more of tetrapropylammonium hydroxide or tetrapropylammonium bromide.

[0047] According to the method for preparing the cross-shaped hollow MFI molecular sieve of the present invention, in step (B6), the mixed solution obtained in step (B5) (referred to as the second mixed solution) is subjected to hydrothermal dynamic crystallization at 140-180°C for 6-48 hours. For example, the mixed solution obtained in step (B5) can be transferred to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and then subjected to hydrothermal dynamic crystallization. The dynamic crystallization is performed by subjecting the mixed solution to a crystallization reaction while in motion, such as under stirring.

[0048] According to the method for preparing the cross-shaped hollow MFI molecular sieve of the present invention, in step (B7), the product obtained in step (B6) is filtered to separate the crystallized molecular sieve from the mother liquor, and then washed to remove the mother liquor attached to the molecular sieve. The mother liquor may be washed with water, and then dried and calcined. The calcination temperature is, for example, 450 to 600° C., for example, 500 to 600° C., and the calcination time is, for example, 2 to 12 hours or 2 to 6 hours. The parent molecular sieve is obtained.

[0049] The parent molecular sieve is a cross-shaped MFI molecular sieve. It is a solid molecular sieve. To this end, the present invention further provides an MFI structured molecular sieve having a cross-shaped crystal morphology and an average crystallite size of 800 to 1500 nm. After a one-step alkali treatment, the cross-shaped MFI molecular sieve has a crystal retention rate of 95% to 110%. The alkali treatment comprises mixing the MFI structured molecular sieve with an alkali-containing solution and stirring at 60 to 90°C for 20 to 60 minutes, wherein the alkali content of the alkali-containing solution is 0.4 to 2.0 mol / L. After the alkali treatment, the parent molecular sieve can obtain a hollow cross-shaped MFI molecular sieve.

[0050] According to the preparation method of the cross-shaped hollow MFI molecular sieve of the present invention, step (B8) is to mix the parent molecular sieve with an alkaline solution and stir it for 20 to 60 minutes at 60 to 90 ° C to form a hollow structure. Then, it is filtered and washed, for example with water, to wash away the alkaline solution in the treated parent molecular sieve, and dried to obtain a solid. The alkaline solution is, for example, an alkaline solution containing one or more of sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. The content of alkali in the alkaline solution is 0.4-2.0 mol / L, for example, 0.4-1 mol / L.

[0051] According to the method for preparing the cross-shaped hollow MFI molecular sieve of the present invention, preferably, the method further comprises step (B9): treating the solid product obtained in step (B8) to obtain an H-type hollow cross-shaped ZSM-5 molecular sieve. One embodiment comprises exchanging the solid product obtained in step (B8), for example, by ammonium exchange, followed by drying and calcining. The methods of ammonium exchange, drying and calcining are well known to those skilled in the art. For example, the calcination temperature can be 500-600°C, and the calcination time can be 1-5 hours.

[0052] According to the method for preparing the cross-shaped hollow MFI molecular sieve of the present invention, in one specific embodiment, the preparation steps of the cross-shaped hollow MFI molecular sieve are as follows:

[0053] A. Preparation of seed molecular sieve, including the following preparation steps:

[0054] (1) Dissolve the silicon source and template in water and heat with stirring at 30-60°C for 2-6 hours;

[0055] (2) transferring the solution of step A(1) into a high-pressure hydrothermal reactor and subjecting it to hydrothermal dynamic crystallization at 140-180° C. for 8-24 h;

[0056] (3) The reaction product obtained in step A(2) is recorded as seed solution.

[0057] B. Preparation of cross-shaped hollow MFI molecular sieve, including the following preparation steps:

[0058] (1) dissolving an alkali source in water, stirring evenly, and obtaining an alkali source solution after the alkali source is fully dissolved;

[0059] (2) dissolving an aluminum source in water and stirring uniformly to obtain an aluminum source solution, adding a certain amount of a template solution or a mixture of a template and an organic silicon source, and mixing thoroughly to obtain an aluminum source-containing dispersion; the thorough mixing is performed, for example, at room temperature to 50° C. and stirring for more than 1 hour, for example, 1 to 4 hours; wherein the molar ratio of the template to the SiO2 in the silicon source (second silicon source) in step (3) is 0.02 to 0.08

[0060] (3) Mixing the silicon source (second silicon source) with the alkaline source solution of step B (1) and stirring at room temperature for 10 to 30 minutes;

[0061] Alternatively, step (2) may be replaced by the following (2'), and step (3) may be replaced by the following (3'),

[0062] (2') dissolving the aluminum source in water and stirring evenly to obtain an aluminum source solution,

[0063] (3') mixing a silicon source (second silicon source) with the alkaline source solution of step B (1), stirring at room temperature for 10 to 30 minutes; adding a certain amount of template solution or a mixture of template and organosilicon source, stirring, for example, at room temperature to 50° C. for more than 1 hour, for example, 1 to 4 hours; wherein the molar ratio of the template to the SiO2 in the silicon source (second silicon source) is 0.02 to 0.08;

[0064] (4) adding the mixture obtained in step B(3) or B(3') to a certain amount of water, then adding the product of step B(2) or B(2') under stirring, and stirring at room temperature for 30 to 60 minutes;

[0065] (5) Add a certain amount of the seed solution described in step A(3) to the product of step B(4) and stir at room temperature for 1 to 6 hours;

[0066] (6) transferring the product obtained in step B(5) to a high-pressure hydrothermal reactor and subjecting it to hydrothermal dynamic crystallization at 140-180° C. for 6-48 hours;

[0067] (7) filtering, washing, drying, and calcining the product obtained in step B (6) to obtain a parent molecular sieve;

[0068] (8) mixing the parent molecular sieve obtained in step B (7) with an alkaline solution, stirring at 60-90° C. for 20-60 min, wherein the alkaline content in the alkaline solution is 0.4-2.0 mol / L;

[0069] (9) The solid product obtained in step B (8) is subjected to ammonium exchange to obtain an H-type cross-shaped hollow MFI molecular sieve.

[0070] According to the wear-resistant MFI molecular sieve catalyst of the present invention, the MFI molecular sieve is preferably the cross-shaped hollow MFI molecular sieve provided by the present invention. In addition to having high wear resistance, the catalyst also has high accessibility to active centers and good catalytic performance due to the hollow structure of the cross-shaped hollow MFI molecular sieve.

[0071] The attrition-resistant MFI molecular sieve catalyst is preferably a fluidizable catalyst, such as a catalyst for fluidized catalytic cracking. The fluidizable, attrition-resistant MFI molecular sieve catalyst preferably has an average particle size of 60 to 80 microns. The average particle size is measured using laser particle size analysis, which is well known to those skilled in the art.

[0072] According to the attrition-resistant MFI molecular sieve catalyst provided by the present invention, the thermal attrition (5h loss %) of the catalyst is less than 4.2% by mass.

[0073] According to the wear-resistant MFI molecular sieve catalyst provided by the present invention, the support material includes aluminum sol, and the average particle size of the aluminum sol is preferably 5 to 50 nm. In one embodiment, the content of the aluminum sol in the catalyst is 10 to 20% by mass in terms of Al2O3.

[0074] According to the wear-resistant MFI molecular sieve catalyst provided by the present invention, the support material comprises silica sol, and the average particle size of the silica sol is preferably 5 to 20 nm. In one embodiment, the content of silica sol in the wear-resistant MFI molecular sieve catalyst is 5 to 10% by mass, calculated as SiO2.

[0075] The average particle size of the aluminum sol and the average particle size of the silica sol were measured by a dynamic light scattering method.

[0076] According to the wear-resistant MFI molecular sieve catalyst provided by the present invention, the carrier material of the wear-resistant MFI molecular sieve catalyst further includes a matrix, and the matrix is, for example, one or more of clay, alumina such as γ-alumina, and pseudo-boehmite.

[0077] In one embodiment, the attrition-resistant MFI molecular sieve catalyst may have a clay content of 0-50% by mass, for example, 10-40% by mass, on a dry basis, and alumina and / or pseudo-boehmite content of 0-50% by mass, for example, 10-40% by mass, calculated as Al2O3. The content of each component in the catalyst is calculated based on the raw materials added during preparation.

[0078] The room temperature described in the following examples and comparative examples is 26°C.

[0079] The average particle size of the aluminum sol and the average particle size of the silica sol were measured by dynamic light scattering using a Malvern Zetasizer Nano ZS90 instrument.

[0080] The measurement method of thermal wear is in accordance with standard Q / SH 3360252-2015.

[0081] Example 1

[0082] A. Preparation of seed solution:

[0083] (A1) 39.8 g of ethyl orthosilicate, 42.5 g of tetrapropylammonium hydroxide, and 120.0 g of deionized water were mixed and heated with stirring at 40° C. for 4 h;

[0084] (A2) transferring the solution from step (A1) to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and subjecting it to dynamic crystallization at 170° C. for 12 h;

[0085] (A3) is taken out after the crystallization is completed and recorded as seed solution 1;

[0086] B Preparation of cross-shaped hollow ZSM-5 molecular sieve:

[0087] (B1) adding 7.86 g of potassium hydroxide to 23.58 g of deionized water and stirring to obtain an alkaline source solution;

[0088] (B2) adding 1.80 g of aluminum sulfate 18hydrate to 16.2 g of deionized water and stirring uniformly to obtain an aluminum source solution;

[0089] (B3) 36.80 g of silica sol (sodium silicate, 30% by mass silicon oxide content, pH 9.2, 0.22% by mass Na2O content) was slowly added to the alkali source solution of step (B1), and stirred at room temperature for 30 minutes. Then, a mixed solution of 8.96 g of tetrapropylammonium hydroxide and 3.50 g of ethyl orthosilicate was added, and stirred at 35°C for 2 hours;

[0090] (B4) adding 210.82 g of deionized water to the product of step (B3), then adding the aluminum source solution of step (B2) while stirring, and stirring at room temperature for 30 minutes;

[0091] (B5) adding 5.52 g of the seed solution 1 from step (A3) to the product from step (B4) and stirring at room temperature for 4 hours;

[0092] (B6) transferring the mixed solution from step (B5) to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and subjecting it to hydrothermal dynamic crystallization at 170° C. for 48 h;

[0093] (B7) filtering, washing, drying, and calcining the product obtained in step (B6) to obtain molecular sieve S-1;

[0094] (B8) molecular sieve S-1 and a 0.6 mol / L sodium hydroxide solution were mixed uniformly, with the mass ratio of molecular sieve S-1 to the alkaline solution being 1:10. The mixture was heated to 80°C at a heating rate of 4°C / min and stirred at the same temperature for 30 min. The mixture was filtered, washed, and dried to obtain molecular sieve S-1-J.

[0095] (B9) Molecular sieve S-1-J: ammonium chloride: deionized water were mixed in a mass ratio of 1:1:10, stirred and heated in a water bath at 80°C for 30 min, filtered, washed, and dried, and then the dried solid: ammonium chloride: deionized water were mixed in a mass ratio of 1:0.5:10, subjected to a second ammonium exchange, filtered, washed, dried, and calcined at 550°C for 2 h to obtain a hydrogen-type cross-shaped hollow ZSM-5 molecular sieve, recorded as S-1-JH. Figure 1 This is a transmission electron microscope image.

[0096] Example 2

[0097] A. Prepare seed solution:

[0098] (A1) 45.6 g of ethyl orthosilicate, 28.9 g of tetrapropylammonium hydroxide, and 105.9 g of deionized water were mixed and heated with stirring at 40° C. for 4 h;

[0099] (A2) transferring the solution from step (A1) to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and subjecting it to dynamic crystallization at 170° C. for 12 h;

[0100] (A3) is taken out after the crystallization is completed and recorded as seed solution 2;

[0101] B Preparation of cross-shaped hollow ZSM-5 molecular sieve:

[0102] (B1) Add 6.34 g of potassium hydroxide to 28.88 g of deionized water and stir well;

[0103] (B2) adding 1.67 g of aluminum isopropoxide to 19.205 g of deionized water and stirring uniformly, then adding a mixed solution of 4.85 g of tetrapropylammonium hydroxide and 2.25 g of ethyl orthosilicate, and stirring at 40° C. for 1 hour;

[0104] (B3) adding 40.20 g of silica sol (silicon oxide content 30%) to the alkali source solution of step (B1) and stirring at room temperature for 30 minutes;

[0105] (B4) adding 252.61 g of deionized water to the product of step (B3), then adding the aluminum source solution of step (B2) while stirring, and stirring at room temperature for 30 minutes;

[0106] (B5) adding 9.65 g of the seed solution 2 from step (A3) to the product obtained in step (B4) and stirring at room temperature for 4 hours;

[0107] (B6) transferring the product of step (B5) to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and subjecting it to hydrothermal dynamic crystallization at 170° C. for 48 h;

[0108] (B7) filtering, washing, drying, and calcining the product obtained in step (B6) to obtain molecular sieve S-2;

[0109] (B8) molecular sieve S-2 and a 0.8 mol / L sodium hydroxide solution were mixed uniformly, with the mass ratio of molecular sieve S-2 to sodium hydroxide solution being 1:10, and the mixture was heated to 80°C at a heating rate of 4°C / min, stirred at the same temperature for 30 min, filtered, washed, and dried to obtain molecular sieve S-2-J;

[0110] (B9) The molecular sieve S-2-J: ammonium chloride: deionized water were mixed in a mass ratio of 1:1:10, stirred and heated in a water bath at 80°C for 30 minutes, filtered, washed, and dried, and then the dried solid: ammonium chloride: deionized water were mixed in a mass ratio of 1:0.5:10, subjected to a second ammonium exchange, filtered, washed, dried, and calcined at 550°C for 2 hours to obtain a hydrogen-type (H-type) cross-shaped hollow ZSM-5 molecular sieve, recorded as S-2-JH.

[0111] Comparative Example 1

[0112] Comparative Example: A conventional hexagonal ZSM-5 molecular sieve with a crystal size of 2.5 μm was selected and subjected to alkali treatment and ammonium exchange according to steps (B8) and (B9) of Example 1, and was designated as DS-1-JH. It does not have a hollow structure.

[0113] Preparation of catalytic cracking catalysts in Examples 3-4 and Comparative Example 2

[0114] Among them, the raw materials other than the molecular sieves used are commercially available products. The average particle sizes of the aluminum sol and silica sol used in each embodiment and comparative example are shown in Table 2.

[0115] (1) molecular sieve, aluminum sol, silica sol, kaolin and pseudo-boehmite slurry and deionized water were uniformly mixed to form a slurry with a solid content of 40% by mass, and spray-dried to obtain catalyst microspheres;

[0116] (4) The catalyst microspheres were calcined at 550 °C for 4 h;

[0117] (5) The calcined catalyst microspheres were exchanged at 80° C. for 1 hour, filtered, and the exchange and filtration process was repeated once in a mass ratio of catalyst microspheres: ammonium salt: H O = 1:1:10, and then dried. The ammonium salt was ammonium chloride, and the sodium oxide content of the resulting catalytic cracking catalyst was less than 0.15% by mass. The composition of the prepared catalyst is shown in Table 2.

[0118] Table 1

[0119]

[0120] The molecular sieve synthesis ratio is the ratio of the product of step B4. The crystallinity retention after alkali treatment is the ratio of the crystallinity of the parent molecular sieve obtained in step B7 after alkali treatment to the crystallinity of the parent molecular sieve. For example, in Example 1, it is the ratio of the crystallinity of S-1-J to the crystallinity of S-1, and in Example 2, it is the ratio of the crystallinity of S-2-J to the crystallinity of S-2.

[0121] Table 2 Catalyst composition and thermal wear performance

[0122]

Claims

1. A method for preparing a cross-shaped hollow MFI molecular sieve, the method comprising: A. Preparation of seed molecular sieve, comprising the following steps: (A1) Dissolve the silicon source and template in water and stir at 30-60°C for 2-6 hours; the molar ratio of R / SiO2 is 0.10-0.30, and the molar ratio of H2O / SiO2 is 15-50, where R represents the template; (A2) hydrothermally crystallizing the product of step (A1) at 140-180°C for 8-24 hours; the resulting reaction product is referred to as the seed solution; B. Preparation of cross-shaped hollow MFI molecular sieve, including the following preparation steps: (B1) dissolving an alkali source in water and stirring uniformly to obtain an alkali source solution; (B2) mixing an aluminum source with water and stirring uniformly to obtain an aluminum source solution, and optionally adding a second template solution and an optional organosilicon source; (B3) mixing a second silicon source with the alkaline source solution obtained in step (B1) and stirring at room temperature; optionally adding a second template solution and an optional organosilicon source; (B4) Mixing the product obtained in step (B3) with optional water, then adding the product obtained in step (B2) under stirring, and stirring at room temperature to obtain a first mixed solution; the molar ratio of the first mixed solution is: n (SiO2) / n (Al2O3)=50~200, n (K2O) / n (SiO2)=0.25~0.40, n (H2O) / n (SiO2)=60~100; wherein, the SiO2 in the ratio refers to SiO2 from the second silicon source; (B5) adding the seed solution obtained in step (A2) to the first mixed solution in step (B4), stirring at room temperature to obtain a second mixed solution; optionally adding a second template solution and an optional organic silicon source; wherein the SiO2 from the seed solution accounts for 4-10% by mass of the SiO2 in the second silicon source; wherein, in at least one of steps (B2), (B3) or (B5), a second template solution and an optional organosilicon source are added, and the molar ratio of the total amount of the second template added in steps (B2), (B3) and / or (B5) to SiO2 in the second silicon source is 0.02 to 0.08; (B6) hydrothermally dynamic crystallizing the second mixed solution obtained in step (B5) at 140 to 180° C. for 6 to 48 hours; (B7) filtering, washing, drying, and calcining the product obtained in step (B6) to obtain a parent molecular sieve; (B8) mixing the parent molecular sieve obtained in step (B7) with an alkaline solution having an alkali content of 0.4-2.0 mol / L, and stirring at 60-90° C. for 20-60 min to obtain a solid product; and Optionally (B9) the solid product obtained in step (B8) is subjected to ammonium exchange to obtain an H-type cross-shaped hollow MFI molecular sieve.

2. The method according to claim 1, wherein The silicon source in step (A1) is one or more of methyl orthosilicate or ethyl orthosilicate, and the template in step (A1) is one or more of tetrapropylammonium hydroxide or tetrapropylammonium bromide; the organosilicon source in step B is one or more of methyl orthosilicate or ethyl orthosilicate, and the template in step B is one or more of tetrapropylammonium hydroxide or tetrapropylammonium bromide.

3. The method according to claim 1, wherein The grain size of the seed crystals in the seed solution in step (A2) is 200-800 nm.

4. The method according to claim 1, wherein The concentration of the alkaline source solution in step (B1) is 10 to 30% by mass, and the alkaline source is one or more of potassium hydroxide, rubidium hydroxide or cesium hydroxide.

5. The method according to claim 1, wherein The concentration of the aluminum source solution in step (B2) is 5 to 20% by mass, and the aluminum source is one or more of aluminum sulfate, aluminum nitrate, or aluminum chloride; In step (B3), the second silicon source is silica sol, and the SiO2 content in the silica sol is 15-45% by mass.

6. The method according to claim 1, wherein The mass ratio of the total amount of the organic silicon source added in steps (B2), (B3) and (B5) calculated as SiO2 to the second silicon source calculated as SiO2 is 5:100 to 10:

100.

7. The method according to claim 1, wherein When the second template and the optional organosilicon source are added in step (B5), they are first added to the seed solution of step (B5), then stirred at 30-60°C for 0.5-4 hours, and then added to the first mixed solution obtained in step (B4).

8. The method according to claim 1, wherein In step (B3), the mixture is stirred at room temperature for 10 to 30 minutes; in step (B4), the mixture is stirred at room temperature for 30 to 60 minutes; and in step (B5), the mixture is stirred at room temperature for 1 to 6 hours.

9. A cross-shaped hollow MFI molecular sieve, characterized in that: The cross-shaped hollow MFI molecular sieve has an average grain size of 800-1500 nm and a shell thickness of 100-400 nm. The cross-shaped hollow MFI molecular sieve is prepared according to the method according to any one of claims 1 to 8.

10. The cross-shaped hollow MFI molecular sieve according to claim 9, characterized in that: The cross-shaped hollow MFI molecular sieve is an H-type cross-shaped hollow MFI molecular sieve.

11. The cross-shaped hollow MFI molecular sieve according to claim 9, characterized in that: The catalyst prepared by combining the molecular sieve with a specific particle size carrier material has a thermal wear loss of less than 4.2% by mass in 5 hours, wherein the specific particle size carrier material is silica sol and / or aluminum sol, the average particle size of the aluminum sol carrier material is 5-50 nm, the average particle size of the silica sol carrier material is 5-20 nm, the catalyst optionally contains one or more matrices selected from clay, alumina, and an alumina precursor, and the composition of the catalyst includes: 20-60% by mass of the cross-shaped hollow MFI molecular sieve calculated on a dry basis, 10-20% by mass of the aluminum sol calculated on Al2O3, 5-10% by mass of the silica sol calculated on SiO2, and 20-50% by mass of the matrix calculated on a dry basis.

12. An abrasion-resistant MFI molecular sieve catalyst comprising a carrier material and an MFI molecular sieve, wherein the MFI molecular sieve is the cross-shaped hollow MFI molecular sieve according to any one of claims 9 to 11 or the cross-shaped hollow MFI molecular sieve obtained by the method according to any one of claims 1 to 8.

13. The wear-resistant MFI molecular sieve catalyst according to claim 12, characterized in that: The catalyst loss due to thermal wear is less than 4.2% by mass in 5 hours.

14. The wear-resistant MFI molecular sieve catalyst according to claim 12 or 13, characterized in that: The carrier material includes aluminum sol with an average particle size of 5 to 50 nm, silica sol with an average particle size of 5 to 20 nm and one or more matrices selected from clay, alumina and pseudo-boehmite. The content of the aluminum sol with an average particle size of 5 to 50 nm in the catalyst is 10 to 20% by mass as calculated by Al2O3, the content of the silica sol with an average particle size of 5 to 20 nm in the catalyst is 5 to 10% by mass as calculated by SiO2, the content of clay is 0 to 50% by mass on a dry basis, and the content of alumina and / or pseudo-boehmite is 0 to 50% by mass as calculated by Al2O3.

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