Molecular sieve membrane, method for preparing the same, and use thereof

Abstract

The application provides a molecular sieve membrane and a preparation method and application thereof. The molecular sieve membrane has a membrane thickness of 10-500 mu m, preferably 30-200 mu m. The application provides a preparation method of the molecular sieve membrane, which comprises the following steps: a) preparing a colloidal slurry by mixing molecular sieve seeds, a silicon source, water, an optional aluminum source and an optional colloidal stabilizer; b) uniformly dispersing the colloidal slurry on the surface of a carrier skeleton and drying to obtain a green body; and c) performing heat treatment on the green body in the presence of an organic amine, so that the surface coating of the green body is converted into a molecular sieve membrane. According to the method, the thickness of the molecular sieve membrane can be effectively adjusted. Meanwhile, the organic amine solution and the coating slurry are prepared separately in the application, and the coating slurry can be repeatedly used. The crystallization organic amine solution can be repeatedly used or recycled because it almost does not change chemically, so that the amount of waste mother liquor is greatly reduced, and the method is particularly suitable for industrial production.

Description

Technical Field

[0001] This invention relates to a method for preparing a molecular sieve membrane, and the molecular sieve membrane obtained by the method and its application in olefin cracking reactions. Background Technology

[0002] Molecular sieve membranes, as a representative type of inorganic membranes, possess all the properties of molecular sieves, including controllable pore structure, uniform and tunable pore size distribution, and adjustable acid density. Therefore, molecular sieve membranes hold promising applications in areas such as molecular-level regulation of catalytic reactions, membrane separation, and environmental treatment of various exhaust gases, and have become a research hotspot in inorganic membrane materials in recent years.

[0003] Molecular sieve membrane preparation can be divided into three main categories: filled membranes, self-supported membranes, and supported membranes. Supported molecular sieve membranes, possessing all the characteristics of molecular sieves, have become the most promising type of molecular sieve membrane for development. The preparation methods for supported molecular sieve membranes are mainly divided into four categories: hydrothermal in-situ generation, secondary growth, microwave synthesis, and vapor phase crystallization. Among these, the secondary growth method is the most commonly used. It involves first attaching a layer of pre-synthesized nanoscale molecular sieve crystals as seed crystals to a support, then immersing it in a synthesis solution for secondary crystallization. This results in the formation of a continuous molecular sieve membrane on the support surface under the promotion of the molecular sieve seed crystals. Examples include existing technologies CN111097293A, CN107840352A, CN101648712B, and CN1077658. However, in these methods, the seed crystals are directly coated, making the preparation process complex and cumbersome. The resulting molecular sieve membranes often have defects, and product quality cannot be effectively controlled or guaranteed. Furthermore, their production costs and application effects are far from meeting the requirements for industrial applications. Summary of the Invention

[0004] To overcome the above-mentioned defects, there is a particular need for a high-quality, simple, and environmentally friendly molecular sieve membrane preparation technology. This technology is intended to address the problems of complex and cumbersome molecular sieve membrane preparation processes, numerous defects in the resulting membranes, inability to effectively control and guarantee product quality, and the large amount of waste mother liquor generated.

[0005] According to a first aspect of the present invention, the present invention provides a molecular sieve membrane with a thickness of 10-500 μm, preferably 30-200 μm.

[0006] According to a second aspect of the present invention, the present invention provides a method for preparing a molecular sieve membrane, the method comprising:

[0007] a) Formulate molecular sieve seed crystals, silicon source, water, optional aluminum source, and optional colloidal stabilizer into a colloidal slurry;

[0008] b) Disperse the colloidal slurry evenly on the surface of the carrier skeleton and dry it to obtain the green body;

[0009] c) In the presence of organic amines, the preform is heat-treated to convert the surface coating of the preform into a molecular sieve membrane.

[0010] According to a third aspect of the present invention, the present invention provides a molecular sieve membrane prepared by the method of the present invention.

[0011] According to a fourth aspect of the present invention, the present invention provides the application of the molecular sieve membrane of the present invention in olefin pyrolysis reactions.

[0012] According to the method of the present invention, the molecular sieve membrane prepared by dispersing seed slurry on a carrier and then performing heat treatment and conversion has high crystallinity, denser structure, high molecular sieve adhesion, and the thickness of the membrane can be arbitrarily adjusted and the shape can be arbitrarily changed according to the carrier.

[0013] The method of the present invention has a simple preparation process and convenient process control. The prepared product can be easily produced by conventional post-processing methods such as separation, washing, and calcination.

[0014] The molecular sieve membrane prepared by the method of this invention is of high quality and achieves good technical results. When the prepared molecular sieve membrane catalyst is used in olefin cracking reactions, it significantly improves the internal diffusion performance of the catalyst, reduces secondary reactions of the main reaction products propylene and ethylene, and exhibits significantly higher selectivity for propylene and ethylene dienes compared to conventional catalysts.

[0015] This invention solves the problem effectively by using a colloidal slurry with appropriate solid content, prepared by mixing molecular sieve seed crystals and silicon source, and optionally aluminum source, then uniformly dispersing the colloidal slurry on the surface of a carrier skeleton, drying it to obtain a preform, and placing the preform in an organic amine aqueous slurry or its steam for hydrothermal treatment, thereby transforming the carrier surface coating into a molecular sieve membrane. This invention can be used for the industrial production of molecular sieve membranes.

[0016] Furthermore, the method of the present invention allows for effective adjustment of the molecular sieve membrane thickness. In addition, the organic amine solution and coating slurry of the present invention are prepared separately, and the coating slurry can be reused repeatedly. The crystallized organic amine solution, since it undergoes almost no chemical change, can be reused or recycled. Therefore, the amount of waste mother liquor is greatly reduced, making it particularly suitable for industrial production. Attached Figure Description

[0017] Figure 1 This is a SEM image of the cross-section of the molecular sieve membrane and the carrier in Example 1.

[0018] Figure 2 This is a photograph of the surface morphology of the molecular sieve membrane sample from Example 1.

[0019] Figure 3 This is a cross-sectional SEM image of the sample from Example 1.

[0020] Figure 4 The image shows the XRD test results of the molecular sieve membrane scraped from the surface of the sample in Example 1. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The present invention provides a molecular sieve membrane with a thickness of 10-500 μm, preferably 30-200 μm.

[0023] According to the present invention, due to the membrane structure of the molecular sieve catalyst, the internal diffusion effect of the catalyst is almost eliminated, and under the same conditions, the diene selectivity reaches more than 70% when used for olefin cracking reaction.

[0024] According to a preferred embodiment of the present invention, the molecular sieve is one or more of ZSM-5, ZSM-11, ZSM-35, ZSM-48, β, Y, mordenite and SAPO-34; preferably one or more of ZSM-5, ZSM-11 and ZSM-35. In the embodiments of the present invention, ZSM-5 and ZSM-11 are used as examples, but the present invention is not limited thereto.

[0025] Molecular sieve membranes possessing the aforementioned features of this invention can all achieve the objectives of this invention, and there are no special requirements for their preparation methods. According to a preferred embodiment of this invention, this invention provides a method for preparing a molecular sieve membrane, the method comprising:

[0026] a) Formulate molecular sieve seed crystals, silicon source, water, optional aluminum source, and optional colloidal stabilizer into a colloidal slurry;

[0027] b) The colloidal slurry is uniformly coated on the surface of the carrier skeleton and dried to obtain the preform;

[0028] c) In the presence of organic amines, the preform is heat-treated to convert the surface coating of the preform into a molecular sieve membrane.

[0029] This invention solves the problem effectively by using a colloidal slurry with appropriate solid content, prepared by mixing molecular sieve seed crystals and silicon source, and optionally aluminum source, then uniformly coating the colloidal slurry onto the surface of a carrier skeleton and drying it to obtain a preform. The preform is then placed in an organic amine aqueous slurry or its steam for hydrothermal treatment, thereby transforming the carrier surface coating into a molecular sieve membrane. This invention can be used for the industrial production of molecular sieve membranes.

[0030] Furthermore, the method of the present invention allows for effective adjustment of the molecular sieve membrane thickness. In addition, the organic amine solution and coating slurry of the present invention are prepared separately, and the coating slurry can be reused repeatedly. The crystallized organic amine solution, since it undergoes almost no chemical change, can be reused or recycled. Therefore, the amount of waste mother liquor is greatly reduced, making it particularly suitable for industrial production.

[0031] According to a preferred embodiment of the present invention, in step a), the solid content of the colloidal slurry is 1-50% by weight, preferably 2-40% by weight. Using the aforementioned solid content has the advantages of convenient slurry preparation and adjustable molecular sieve membrane thickness.

[0032] According to a preferred embodiment of the present invention, in step a), the silicon-to-aluminum molar ratio of the colloidal slurry is 5-1000, preferably 10-500. Using the aforementioned silicon-to-aluminum molar ratio has the advantage of being able to prepare most types of molecular sieve membranes.

[0033] According to a preferred embodiment of the present invention, in step a), the content of molecular sieve seed crystals in the colloidal slurry is 1-80% by weight of all solid oxides, preferably 10-60% by weight. Using the aforementioned content has the advantage of adjusting the crystallinity of the molecular sieve membrane and mitigating the hydrothermal treatment conditions.

[0034] According to a preferred embodiment of the present invention, in step a), the weight ratio of molecular sieve seed crystals, silicon source, water, aluminum source, and colloidal stabilizer is 0.2-80:1-80:100:0-3:0-10; preferably 2-15:8-20:100:0-3:0.01-0.2. Using the aforementioned ratio provides advantages such as high crystallinity, denser structure, high molecular sieve adhesion, and adjustable and controllable membrane thickness.

[0035] According to a preferred embodiment of the present invention, the molecular sieve seed type is selected from one or more of ZSM-5, ZSM-11, ZSM-35, ZSM-48, β, Y, mordenite and SAPO-34; preferably selected from one or more of ZSM-5, ZSM-11 and ZSM-35.

[0036] According to a preferred embodiment of the present invention, the silicon-to-aluminum molar ratio of the molecular sieve seed crystals is 5-1000, preferably 200-500. Using the aforementioned molar ratio has the advantage of being able to prepare most types of molecular sieve membranes.

[0037] According to the present invention, the range of silicon sources that can be selected is relatively wide, and commonly used silicon sources can all be used in the present invention. For the present invention, it is preferred to select one or more of silicone grease, silica sol, and water glass. More preferably, the silicon source is selected from at least one of silica sol, tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, and water glass. In the embodiments of the present invention, silica sol is used as an example to illustrate the advantages of the present invention, but the present invention is not limited thereto. More preferably, the solid content of the silica sol is 10-40% by weight.

[0038] According to the present invention, the range of aluminum sources that can be selected is relatively wide, and commonly used aluminum sources can all be used in the present invention. For the present invention, it is preferred to select at least one of aluminum isopropoxide, boehmite, alumina, sodium aluminate, aluminum nitrate, aluminum chloride or aluminum sulfate, and more preferably to select one or more of sodium aluminate, aluminum sulfate, aluminum chloride and aluminum nitrate.

[0039] According to the present invention, the carrier material can be inorganic, such as alumina, silicon dioxide, ceramics, stainless steel, etc., or organic, such as plastics, paper, etc. To ensure a firm bond between the molecular sieve membrane and the carrier, the carrier surface preferably has appropriate roughness. The carrier is subjected to surface washing and cleaning treatment before use to remove impurities and dust. The cleaning method has no special requirements and will not be described in detail here.

[0040] For the purposes of this invention, the carrier is preferably selected from one or more of alumina, silicon dioxide, ceramics, glass, stainless steel, and plastics.

[0041] According to the present invention, the shape of the carrier is not particularly required, and commonly used shapes can be used in the present invention. For the present invention, the preferred shape of the carrier is selected from one or more of Raschig rings, porous preforms, and small spheres. The embodiments of the present invention use Raschig ring ceramic spheres as an example to illustrate the advantages of the present invention.

[0042] According to the present invention, the range of types of organic amines is relatively wide, and commonly used organic amine template agents can be used in the present invention. The organic amines used in the present invention are selected from one or more of diamines, aliphatic amines, and quaternary ammonium salts. Commonly used diamines, aliphatic amines (including various primary, secondary, and tertiary aliphatic amines), and quaternary ammonium salts can all be used in the present invention. For the present invention, the organic amines are preferably selected from one or more of ethylenediamine, hexamethylenediamine, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, propylamine, butylamine, tetraethylammonium bromide, tetrapropylammonium bromide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide.

[0043] In embodiments of the present invention, triethylamine, tetrapropylammonium hydroxide, and ethylenediamine are used as examples to illustrate the advantages of the present invention.

[0044] According to the present invention, the purpose of the heat treatment is to crystallize and form a molecular sieve. There are no special requirements for the temperature of the heat treatment. For the present invention, the preferred temperature of the heat treatment is 100-200℃, and more preferably 120-190℃.

[0045] According to the present invention, the heat treatment time can be selected within a wide range. For the present invention, the preferred heat treatment time is 10-240 hours, and more preferably 24-120 hours.

[0046] According to a specific embodiment of the present invention, preferred step c) includes: placing the blank in an aqueous solution of organic amine or in steam of organic amine and water at a temperature of 100-200°C, preferably 120-190°C, for hydrothermal treatment for 10-240 hours, preferably 24-120 hours.

[0047] According to a preferred embodiment of the present invention, the organic amine aqueous solution has a mass ratio of organic amine to water of 1:0.5-10, preferably 1:0.6-5, and its dosage is sufficient to ensure that there is a certain amount of liquid phase in the closed reactor during hydrothermal treatment.

[0048] According to a preferred embodiment of the present invention, the weight ratio of organic amine to embryo is preferably 0.1-5:1; more preferably 0.3-1.5:1.

[0049] According to a preferred embodiment of the present invention, the method for preparing the molecular sieve membrane of the present invention includes the following steps: a) preparing a uniform colloidal slurry with a silicon-aluminum molar ratio of 5-1000 and a solid content of 1-50% by weight of molecular sieve seed crystals, silicon source, aluminum source and water, based on solid oxides, at a total solid content of 1-80% by weight; b) uniformly coating the colloidal slurry onto the surface of a carrier skeleton and drying it to obtain a preform; c) placing the preform in an organic amine aqueous solution or its vapor at a temperature of 100-200°C for hydrothermal treatment for 10-240 hours to convert the coating on the carrier surface into a molecular sieve membrane.

[0050] According to a preferred embodiment of the present invention, the hydrothermal treatment conditions are more preferably in the range of temperature 120-190°C and time 24-120 hours.

[0051] According to the present invention, after the heat treatment is completed, the sample is cooled, washed with water, and dried to obtain a molecular sieve membrane. The sample can also be modified by calcination, exchange, or other methods to meet the requirements for use.

[0052] According to the present invention, the prepared colloidal slurry is required to be uniform, and a homogenizer can be used to achieve uniform emulsification as needed. The solid content of the slurry can be adjusted to a range of 1-50% by weight according to the required thickness of the molecular sieve membrane, or the thickness of the coating membrane can be increased by multiple impregnations.

[0053] According to the present invention, the slurry coating method of the carrier can be at least one of spray coating or dip-coating method.

[0054] According to the method of the present invention, the molecular sieve membrane prepared by coating a carrier with a seed slurry and then performing heat treatment conversion has high crystallinity, denser structure, high molecular sieve adhesion, adjustable and controllable membrane thickness, and shape that can be arbitrarily changed according to the carrier.

[0055] The carrier of the present invention can be pre-washed using a series of methods including acid washing, water washing, alkali washing, and water washing.

[0056] The method of the present invention has a simple preparation process and convenient process control. The prepared product can be easily produced by conventional post-processing methods such as separation, washing, and calcination.

[0057] The present invention provides a molecular sieve membrane prepared by the preparation method described in the present invention, wherein the membrane thickness of the molecular sieve membrane is preferably 10-500 μm, and more preferably 30-200 μm.

[0058] According to the present invention, the fraction is selected from one or more of ZSM-5, ZSM-11, ZSM-35, ZSM-48, β, Y, mordenite and SAPO-34; preferably selected from one or more of ZSM-5, ZSM-11 and ZSM-35.

[0059] The molecular sieve membrane prepared by the method of this invention is of high quality and achieves good technical results. When the prepared molecular sieve membrane catalyst is used in olefin cracking reactions, it significantly improves the internal diffusion performance of the catalyst, reduces secondary reactions of the main reaction products propylene and ethylene, and exhibits significantly higher selectivity for propylene and ethylene dienes compared to conventional catalysts.

[0060] This invention provides the application of the molecular sieve membrane described herein in olefin pyrolysis reactions.

[0061] The present invention is further illustrated by the following examples, but these are not intended to limit the invention. Specific experimental conditions and methods not specified in the following examples are generally conventional methods well known to those skilled in the art.

[0062] Example 1

[0063] The ￠6 Raschig ring ceramic ring was soaked in 1M hydrochloric acid solution for 2 hours, then washed with deionized water, then soaked in 1M sodium hydroxide solution for 2 hours, washed with deionized water and dried to obtain the carrier (the same applies to the following examples).

[0064] Add 10 g of NaZSM-5 molecular sieve seed crystals with a silicon-aluminum molar ratio of 500 to 500 g of silica sol solution (10% by weight), stir for 30 minutes to obtain a uniform molecular sieve colloidal slurry. The weight ratio of molecular sieve seed crystals, silica, water, and alumina is 2.2:11:100:0.

[0065] One hundred grams of the above-treated carrier is immersed in colloidal slurry for 30 minutes, then removed and dried at 120°C for 8 hours to obtain the coated carrier, referred to as the blank.

[0066] Add 20g of triethylamine and 40g of deionized water to a 200ml reactor. Place a breathable stainless steel mesh on top of the liquid and place 30g of preform on the mesh. After sealing, place the reactor in an oven and maintain the temperature at 180℃ for 72 hours.

[0067] After processing, the preform was cooled and removed, then washed repeatedly with deionized water until the pH of the solution was close to neutral. It was then dried and calcined at 550℃ for 4 hours to obtain the molecular sieve membrane sample. Physicochemical tests are shown below. Figure 1 , Figure 2 , Figure 3 , Figure 4 The obtained molecular sieve membrane sample was subjected to conventional ammonium exchange, dried, and then activated by calcination at 550°C to obtain molecular sieve membrane catalyst A.

[0068] List 2 of molecular sieve membrane preparation.

[0069] Figure 1 This is a SEM image of the cross-section of the molecular sieve membrane and the carrier in Example 1.

[0070] Figure 2 The image shows the morphology of the molecular sieve membrane surface of the sample from Example 1, which is a molecular sieve with closely packed small crystallites.

[0071] Electron microscopy images of cross-sections of molecular sieve samples show that the interface between the molecular sieve membrane and the carrier is clear and tightly bonded, the molecular sieve membrane crystals are clear, the binder impurities are not obvious, and the molecular sieve membrane structure is dense.

[0072] Figure 3 The image shows a cross-sectional SEM image of the sample from Example 1, indicating that the molecular sieve membrane is approximately 70 micrometers thick.

[0073] Figure 4 The image shows the XRD results of the molecular sieve membrane scraped from the surface of the sample in Example 1, which is a ZSM-5 molecular sieve.

[0074] 15 grams of catalyst were loaded into a fixed-bed reactor and fed with a C4 feedstock consisting of 60% butene-1 by weight and the remainder being n-butane. The reactor was then subjected to a reaction at 550°C and a space velocity of 15 h⁻¹. -1Under normal pressure, olefin cracking reaction was carried out, and the butene conversion rate and diene (propylene, ethylene) selectivity of the reaction were compared. The reaction results are listed in Table 1.

[0075] The physicochemical parameters of the molecular sieve are shown in Table 2.

[0076] Example 2

[0077] Add 50g of NaZSM-5 molecular sieve seed crystals (silicon-aluminum molar ratio 500) to 500g of a 10% by weight silica sol solution, stir for 30 minutes, and then remove to obtain a homogeneous molecular sieve colloidal slurry. The weight ratio of molecular sieve seed crystals, silica, water, and alumina is 11:11:100:0.

[0078] Immerse 50 grams of the treated carrier in the colloidal slurry for 30 minutes, then remove it and dry it at 120℃ for 8 hours to obtain the coated carrier, referred to as the blank.

[0079] Add 50 g of a 20% (w / w) tetrapropaneammonium hydroxide aqueous solution to a 200 ml reactor. Place a ventilated stainless steel mesh on top of the liquid, and then place 30 g of the preform on the mesh. After sealing, place the reactor in an oven and maintain the temperature at 180°C for 72 hours.

[0080] After hydrothermal treatment, the green body is cooled and removed. It is then washed repeatedly with deionized water until the pH of the solution is close to neutral. After drying and calcining at 550℃ for 4 hours, a molecular sieve membrane is obtained.

[0081] The obtained molecular sieve membrane sample was subjected to conventional ammonium exchange, dried, and then activated by calcination at 550℃ to obtain the molecular sieve membrane catalyst.

[0082] 15 grams of catalyst were loaded into a fixed-bed reactor and fed with a C4 feedstock consisting of 60% butene-1 by weight and the remainder being n-butane. The reactor was then subjected to a reaction at 550°C and a space velocity of 15 h⁻¹. -1 Under normal pressure, olefin cracking reaction was carried out, and the reaction performance was compared. The reaction results are listed in Table 1.

[0083] Example 3

[0084] Add 100g of 40% by weight silica sol and 300ml of water to a beaker, start the electromagnetic stirrer and stir rapidly for 10 minutes, then add 100g of an aqueous solution containing 0.55g of sodium aluminate, and then add 10g of NaZSM-5 molecular sieve seed crystals with a silicon-aluminum molar ratio of 200. After stirring for 30 minutes, take out a uniform molecular sieve colloidal slurry. The weight ratio of molecular sieve seed crystals, silica, water and alumina is 2.2:8.7:100:0.07.

[0085] Immerse 50 grams of the treated carrier in the colloidal slurry for 30 minutes, then remove it and dry it at 120℃ for 8 hours to obtain the coated carrier, referred to as the blank.

[0086] Add 10 g of a 20% (w / w) tetrapropaneammonium hydroxide aqueous solution, 10 g of triethylamine, and 40 g of deionized water to a 200 ml reactor. Place a breathable stainless steel mesh on top of the liquid, and then place 30 g of the preform on the mesh. After sealing, place the reactor in an oven and maintain the temperature at 180°C for 72 hours.

[0087] After hydrothermal treatment, the green body is cooled and removed. It is then washed repeatedly with deionized water until the pH of the solution is close to neutral. After drying and calcining at 550℃ for 4 hours, a molecular sieve membrane is obtained.

[0088] The obtained molecular sieve membrane sample was subjected to conventional ammonium exchange, dried, and then activated by calcination at 550℃ to obtain the molecular sieve membrane catalyst. 15 g of the catalyst was loaded into a fixed-bed reactor, using a C4 feedstock consisting of 60% butene-1 by weight and the remainder being n-butane, and reacted at 550℃ and a space velocity of 15 h⁻¹. -1 Under normal pressure, olefin cracking reaction was carried out, and the reaction performance was compared. The reaction results are listed in Table 1.

[0089] Examples 4-6

[0090] 100 g of 40% silica sol and 0, 100, and 850 g of water were added to beakers respectively. The electromagnetic stirrer was started and stirred rapidly for 10 minutes. Then, 50 g of aqueous solution containing 1.1 g of sodium aluminate was added dropwise, followed by 10 g of NaZSM-5 molecular sieve seed crystals with a silicon-aluminum molar ratio of 100. After stirring for 30 minutes, uniform molecular sieve colloidal slurries with different feed concentrations were obtained, with solid contents of 32%, 20%, and 5% by weight, respectively.

[0091] Each 50g of the above-treated carrier is immersed in colloidal slurry for 30 minutes, then removed and dried at 120℃ for 8 hours to obtain the coated carrier, referred to as blank A / B / C.

[0092] Add 200g of 20% (w / w) tetrapropaneammonium hydroxide aqueous solution to a 1000ml reactor. Place an aerated stainless steel mesh on top of the liquid, and then place 30g each of preforms A / B / C on the mesh. After sealing, incubate at 180℃ for 72 hours.

[0093] After hydrothermal treatment, the green body was cooled and removed. It was then washed repeatedly with deionized water until the pH of the solution was close to neutral. After drying and calcining at 550℃ for 4 hours, molecular sieve membranes were obtained. The membrane thicknesses were measured to be approximately 150, 100 and 20 micrometers, respectively.

[0094] The obtained molecular sieve membrane sample was subjected to conventional ammonium exchange, dried, and then activated by calcination at 550°C to obtain the molecular sieve membrane catalyst.

[0095] 15 grams of catalyst were loaded into a fixed-bed reactor and fed with a C4 feedstock consisting of 60% butene-1 by weight and the remainder being n-butane. The reactor was then subjected to a reaction at 550°C and a space velocity of 15 h⁻¹. -1 Under normal pressure, olefin cracking reaction was carried out, and the reaction performance was compared. The reaction results are listed in Table 1.

[0096] Examples 7-10

[0097] Add 100g of 40% by weight silica sol and 300ml of water to a beaker, start the electromagnetic stirrer and stir rapidly for 10 minutes, then add 100g of an aqueous solution containing 1.1g of sodium aluminate, and then add 40g of NaZSM-5 molecular sieve seed crystals with a silicon-aluminum molar ratio of 100. After stirring for 30 minutes, take out a uniform molecular sieve colloidal slurry. The weight ratio of molecular sieve seed crystals, silica, water and alumina is 8.7:8.7:100:0.15.

[0098] Immerse 50 grams of the above-treated carrier in colloidal slurry for 30 minutes, then remove it and dry it at 120°C for 8 hours to obtain the coated carrier, referred to as the blank.

[0099] Add 50g of 20% (w / w) tetrapropaneammonium hydroxide solution to a 200ml reactor. Place a ventilated stainless steel mesh on top of the liquid, and then place 30g of each preform on the mesh. After sealing, place the reactor in an oven and maintain the temperature at 120℃, 150℃, and 190℃ for 24 hours, 72 hours, and 120 hours, respectively (see Table 1 for details).

[0100] After hydrothermal treatment, the green body is cooled and removed. It is then washed repeatedly with deionized water until the pH of the solution is close to neutral. After drying and calcining at 550℃ for 4 hours, a molecular sieve membrane is obtained.

[0101] The obtained molecular sieve membrane sample was subjected to conventional ammonium exchange, dried, and then activated by calcination at 550℃ to obtain the molecular sieve membrane catalyst. 15 g of the catalyst was loaded into a fixed-bed reactor, using a C4 feedstock consisting of 60% butene-1 by weight and the remainder being n-butane, and reacted at 550℃ and a space velocity of 15 h⁻¹. -1 Under normal pressure, olefin cracking reaction was carried out, and the reaction performance was compared. The reaction results are listed in Table 1.

[0102] Example 11

[0103] Add 100g of 40% by weight silica sol and 300ml of water to a beaker, start the electromagnetic stirrer and stir rapidly for 10 minutes, then add 100g of an aqueous solution containing 1.1g of sodium aluminate, and then add 10g of NaZSM-11 molecular sieve seed crystals with a silicon-aluminum molar ratio of 100. After stirring for 30 minutes, take out a uniform molecular sieve colloidal slurry.

[0104] Immerse 50 grams of the above-treated carrier in colloidal slurry for 30 minutes, then remove it and dry it at 120°C for 8 hours to obtain the coated carrier, referred to as the blank.

[0105] Add 20g of 20% (by weight) tetrapropylammonium hydroxide solution, 30g of ethylenediamine, and 10g of deionized water to a 200ml reactor. Place a breathable stainless steel mesh on top of the liquid, and then place 30g of the preform on the mesh. After sealing, place the reactor in an oven and maintain the temperature at 180℃ for 72 hours.

[0106] After hydrothermal treatment, the green body is cooled and removed. It is then washed repeatedly with deionized water until the pH of the solution is close to neutral. After drying and calcining at 550℃ for 4 hours, a molecular sieve membrane is obtained.

[0107] The obtained molecular sieve membrane sample was subjected to conventional ammonium exchange, dried, and then activated by calcination at 550°C to obtain the molecular sieve membrane catalyst. 15 grams of the catalyst were loaded into a fixed-bed reactor, using a C4 feedstock consisting of 60% butene-1 by weight and the remainder being n-butane, and reacted at 550°C and a space velocity of 15 h⁻¹. -1 Under normal pressure, olefin cracking reaction was carried out, and the reaction performance was compared. The reaction results are listed in Table 1.

[0108] Example 12

[0109] Add 100g of 40% by weight silica sol and 300ml of water to a beaker, start the electromagnetic stirrer and stir rapidly for 10 minutes, then add 100g of an aqueous solution containing 1.1g of sodium aluminate, and then add 10g of NaZSM-5 molecular sieve seed crystals with a silicon-aluminum molar ratio of 100. After stirring for 30 minutes, a uniform molecular sieve colloidal slurry is obtained.

[0110] Immerse 50 grams of carrier in colloidal slurry for 30 minutes, then remove and dry at 120°C for 8 hours to obtain the coated carrier, referred to as the blank.

[0111] Add 10 g of tetrapropylammonium bromide, 20 g of ethylenediamine, and 40 g of deionized water to a 200 ml reactor, mix well, and then immerse 30 g of the preform into the mixture. After sealing, place the reactor in an oven and maintain the temperature at 180°C for 72 hours.

[0112] After hydrothermal treatment, the green body is cooled and removed. It is then washed repeatedly with deionized water until the pH of the solution is close to neutral. After drying and calcining at 550℃ for 4 hours, a molecular sieve membrane is obtained.

[0113] The obtained molecular sieve membrane sample was subjected to conventional ammonium exchange, dried, and then activated by calcination at 550℃ to obtain the molecular sieve membrane catalyst.

[0114] 15 grams of catalyst were loaded into a fixed-bed reactor and fed with a C4 feedstock consisting of 60% butene-1 by weight and the remainder being n-butane. The reactor was then subjected to a reaction at 550°C and a space velocity of 15 h⁻¹. -1 Under normal pressure, olefin cracking reaction was carried out, and the reaction performance was compared. The reaction results are listed in Table 1.

[0115] Examples 13-15 (Example 13 uses a stainless steel sheet as the carrier; Example 14 uses Φ6 alumina ceramic balls as the carrier; Example 15 uses silica gel balls as the carrier)

[0116] Add 100g of 40% by weight silica sol and 300ml of water to a beaker, start the electromagnetic stirrer and stir rapidly for 10 minutes, then add 100g of an aqueous solution containing 1.1g of sodium aluminate, and then add 10g of NaZSM-5 molecular sieve seed crystals with a silicon-aluminum molar ratio of 100. After stirring for 30 minutes, take out a uniform molecular sieve colloidal slurry. The weight ratio of molecular sieve seed crystals, silica, water and alumina is 2.2:8.7:100:0.15.

[0117] 50 grams of carriers of different materials and shapes, such as treated stainless steel, are immersed in colloidal slurry for 30 minutes. After being removed, they are dried at 120°C for 8 hours to obtain the coated carrier, referred to as the blank.

[0118] Add 50 g of 20% (w / w) tetrapropane ammonium hydroxide solution to a 200 ml reactor. Place a ventilated stainless steel mesh on top of the liquid, and then place 30 g of the preform on the mesh. After sealing, place the reactor in an oven and maintain the temperature at 180°C for 72 hours.

[0119] After hydrothermal treatment, the green body is cooled and removed. It is then washed repeatedly with deionized water until the pH of the solution is close to neutral. After drying and calcining at 550℃ for 4 hours, a molecular sieve membrane is obtained.

[0120] Example 16

[0121] Add 100g of silica sol (10% by weight) to a beaker, start the electromagnetic stirrer, and then add 10g of NaZSM-5 molecular sieve seed crystals with a silicon-aluminum molar ratio of 20. After stirring for 30 minutes, a uniform molecular sieve colloidal slurry is obtained.

[0122] Immerse 50 grams of carrier in colloidal slurry for 30 minutes, then remove and dry at 120°C for 8 hours to obtain the coated carrier, referred to as the blank.

[0123] Add 50 g of 20% (w / w) tetrapropylammonium hydroxide solution to a 200 ml reactor. Place a ventilated stainless steel mesh on top of the liquid, and then place 30 g of the preform on the mesh. After sealing, place the reactor in an oven and maintain the temperature at 180°C for 72 hours. After hydrothermal treatment, cool the preform and remove it. Then, wash it repeatedly with deionized water until the pH of the solution is close to neutral. After drying and calcining at 550°C for 4 hours, the molecular sieve membrane is obtained.

[0124] The obtained molecular sieve membrane sample was subjected to conventional ammonium exchange, dried, and then activated by calcination at 550℃ to obtain the molecular sieve membrane catalyst.

[0125] 15 grams of catalyst were loaded into a fixed-bed reactor and fed with a C4 feedstock consisting of 60% butene-1 by weight and the remainder being n-butane. The reactor was then subjected to a reaction at 550°C and a space velocity of 15 h⁻¹. -1 Under normal pressure, olefin cracking reaction was carried out, and the reaction performance was compared. The reaction results are listed in Table 1.

[0126] Comparative Example 1

[0127] NaZSM-5 molecular sieve with a silicon-to-aluminum molar ratio of 500 was added to 40% by weight of silica sol, and after reaching the appropriate dryness, it was extruded into Φ2 cylinders. Then, it was dried at 120℃ for 8 hours to obtain the green body.

[0128] Add 50 g of 20% (w / w) tetrapropane ammonium hydroxide solution to a 200 ml reactor. Place a ventilated stainless steel mesh on top of the liquid, and then place 30 g of the preform on the mesh. After sealing, place the reactor in an oven and maintain the temperature at 180°C for 72 hours.

[0129] After hydrothermal treatment, the green body is cooled and removed. It is then washed repeatedly with deionized water until the pH of the solution is close to neutral. After drying, it is calcined at 550℃ for 4 hours, followed by conventional ammonium exchange and calcination activation to obtain an active molecular sieve catalyst.

[0130] 15 grams of catalyst were loaded into a fixed-bed reactor and fed with a C4 feedstock consisting of 60% butene-1 by weight and the remainder being n-butane. The reactor was then subjected to a reaction at 550°C and a space velocity of 15 h⁻¹. -1 Under normal pressure, olefin cracking reaction was carried out to obtain butene with a conversion rate of 66.1% and a diene selectivity of 51.2%.

[0131] Due to severe internal diffusion within the catalyst, a secondary reaction of the product diene occurs. Although the butene conversion rate is higher than in Example 1, the diene selectivity is significantly reduced.

[0132] Comparative Example 2

[0133] First, 20 grams of NaZSM-5 molecular sieve seed crystals with a silicon-aluminum molar ratio of 200 are uniformly dispersed in 100 grams of water to form an emulsion liquid. Then, 50 grams of carrier are soaked in the liquid for 30 minutes. The liquid is removed by decantation, and the carrier is dried to obtain a carrier with seed crystals coated on the surface.

[0134] Weigh 18g of 40wt% tetrapropylammonium hydroxide solution and 2.7g of sodium hydroxide, add them to 350g of deionized water, stir to dissolve, then add 0.27g of sodium aluminate, continue stirring to obtain a clear solution, then add 50g of 40wt% silica sol, stir at room temperature for 4 hours to obtain a colloidal solution with the composition Na2O:TPAOH:SiO2:Al2O3:H2O=0.1:0.1:1:0.005:65.

[0135] 300 ml of the above colloidal solution was placed into a 500 ml high-pressure reactor lined with tetrafluoroethylene. 50 g of pre-coated seeded preform was immersed in the sol. The reactor was sealed and kept at 180 °C for 72 hours to carry out a hydrothermal reaction. The preform was then removed, washed with water, and dried to obtain a molecular sieve membrane carrier.

[0136] The obtained molecular sieve membrane support was calcined at 550°C for 5 hours, and then activated by conventional ammonium exchange to obtain an active molecular sieve membrane catalyst.

[0137] 15 grams of catalyst were loaded into a fixed-bed reactor and fed with a C4 feedstock consisting of 60% butene-1 by weight and the remainder being n-butane. The reactor was then subjected to a reaction at 550°C and a space velocity of 15 h⁻¹. -1 Under normal pressure, olefin cracking reaction was carried out to obtain butene with a conversion rate of 22.1% and a diene selectivity of 52.1%.

[0138] The reaction butene conversion rate and diene selectivity are lower than those of Example 3, which uses molecular sieves with the same silica-alumina ratio.

[0139] Comparative Example 3

[0140] Following the same method as Example 6 of document CN102225314A, ZSM-5 molecular sieve membranes with a silicon-to-aluminum molar ratio of 200 were prepared.

[0141] Step A. Prepare seed crystal slurry

[0142] First, weigh 35 g of a 40 wt% tetrapropylammonium hydroxide solution and 5.4 g of sodium hydroxide, add them to 700 g of deionized water, stir to dissolve, then add 0.55 g of sodium aluminate, continue stirring to obtain a clear solution, then add 100 g of 40 wt% silica sol, stir at room temperature for 4 hours to obtain a colloidal solution with the composition Na2O:TPAOH:SiO2:Al2O3:H2O = 0.1:0.1:1:0.005:65. This mixture is then aged at room temperature for 1 day and used as a sol for preparing seed crystal slurry.

[0143] Weigh 100g of the sol and 10g of NaZSM-5 molecular sieve seed crystals with a silicon-aluminum molar ratio of 200, and prepare a seed slurry. The mass ratio of the seed crystals to the solids in the sol is 10:7, and the solid content of the slurry is 15%. Stir evenly.

[0144] Step B. Pre-coating the seed layer

[0145] Take 50 grams of the carrier treated in Example 1, immerse it in the seed slurry for 30 minutes, take it out and dry it at 120°C for 8 hours to obtain the carrier coated with seed slurry, referred to as the blank.

[0146] Step C. Synthesizing molecular sieve membranes

[0147] Take 300 ml of the remaining sol without seed crystals from step A and put it into a 500 ml high-pressure reactor lined with tetrafluoroethylene. Immerse the preform with seed crystals pre-coated in step B in the sol, seal the reactor, and perform a hydrothermal synthesis reaction at 180°C for 3 hours. Then take it out, wash it with water, and dry it to obtain a preform containing a molecular sieve membrane.

[0148] The obtained molecular sieve membrane preform was calcined at 550°C for 5 hours to remove moisture and template agent from the membrane pores. It was then activated by conventional ammonium exchange calcination to obtain the active molecular sieve catalyst.

[0149] 15 grams of catalyst were loaded into a fixed-bed reactor and fed with a C4 feedstock consisting of 60% butene-1 by weight and the remainder being n-butane. The reactor was then subjected to a reaction at 550°C and a space velocity of 15 h⁻¹. -1 Under normal pressure, olefin cracking reaction was carried out to obtain butene with a conversion rate of 34.6% and a diene selectivity of 50.1%.

[0150] Because the slurry containing most of the molecular sieve seed crystals in the carrier coating layer is only physically bonded to the carrier, the structure is loose. During the hydrothermal crystallization process with the sol mother liquor, the coating partially peels off due to the dissolution and crystallization effect of the alkali on the silicon and aluminum raw materials, resulting in many defects on the surface of the molecular sieve membrane.

[0151] The comparative method produces a large amount of crystallized sol mother liquor containing template agents and molecular sieves, increasing the burden of waste treatment. In contrast, the present invention prepares the template agent solution and the coating slurry separately. The coating slurry can be reused repeatedly, and the organic amine crystallization solution, due to its simple composition and lack of chemical reaction, can be reused or recycled.

[0152] Comparative Example 4

[0153] ZSM-5 molecular sieve membranes with a silicon-aluminum molar ratio of 200 were prepared using a method similar to that in Example 1 of document CN 107840352A.

[0154] First, 20 grams of NaZSM-5 molecular sieve seed crystals with a silicon-aluminum molar ratio of 200 are uniformly dispersed in 100 grams of water to form an emulsion liquid. Then, 50 grams of the above-treated carrier are soaked in the liquid for 30 minutes. The liquid is removed by decantation, and the carrier is dried to obtain a carrier with seed crystals coated on the surface.

[0155] Add 100g of 40% by weight silica sol and 300ml of water to a beaker, start the electromagnetic stirrer and stir quickly for 10 minutes, then add 100g of an aqueous solution containing 0.55g of sodium aluminate and 5.4g of sodium hydroxide, and stir for another 30 minutes to obtain a uniform colloidal slurry.

[0156] Immerse 50 grams of the above-mentioned seed-coated carrier in colloidal slurry for 10 minutes, remove and drain, and then air dry at room temperature to obtain the carrier coated with slurry, referred to as the blank.

[0157] Add 10 g of 20% (w / w) tetrapropylammonium hydroxide solution, 10 g of triethylamine, and 40 g of deionized water to a 200 ml reactor. Place a breathable stainless steel mesh on top of the liquid, and then place 30 g of preform on the mesh. Seal the reactor and place it in an oven at 180°C for 72 hours.

[0158] After heat treatment, the green body is cooled and removed. It is then washed repeatedly with deionized water until the pH of the solution is close to neutral. After drying and calcining at 550℃ for 4 hours, a molecular sieve membrane is obtained.

[0159] The obtained molecular sieve membrane sample was subjected to conventional ammonium exchange, dried, and then activated by calcination at 550°C to obtain an active molecular sieve membrane catalyst. 15 grams of the catalyst were loaded into a fixed-bed reactor, using a C4 feedstock consisting of 60% butene-1 by weight and the remainder being n-butane, and incubated at 550°C and a space velocity of 15 h⁻¹. -1 Under normal pressure, olefin cracking reaction was carried out to obtain butene with a conversion rate of 26.6% and a diene selectivity of 48.1%.

[0160] Molecular sieve seed crystals have poor stability when dispersed in water, and the coating amount obtained by methods such as impregnation is very small. Moreover, the seed crystals are wrapped in the innermost layer after the slurry is coated. When crystallizing by steam heat treatment according to the method of this comparative embodiment, the guiding effect of the seed crystals is not obvious, resulting in poor crystallization effect.

[0161] Table 1

[0162]

[0163] In the event of any discrepancy between the data in the table and the descriptions in the embodiments, the descriptions in the embodiments shall prevail.

[0164] Table 2

[0165]

[0166]

[0167] *The crystallinity of each sample is calculated relative to the XRD intensity of Example 2.

[0168] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for producing a molecular sieve membrane, characterized by, The method comprises: a) preparing a colloidal slurry of molecular sieve seeds, a silicon source, water, optionally an aluminum source, and optionally a colloidal stabilizer; b) uniformly dispersing the colloidal slurry on the surface of a support framework and drying to obtain a green body; c) placing the green body in an aqueous solution of an organic amine or steam thereof, and performing hydrothermal treatment to convert the surface coating of the green body into a molecular sieve membrane.

2. The production method according to claim 1, wherein In step a), the solid content of the colloidal slurry is 1-50 wt%; and / or the silica-to-alumina molar ratio of the colloidal slurry is 5-1000; and / or the content of the molecular sieve seeds in the colloidal slurry is 1-80 wt% of the total solid oxides; and / or the weight ratio of the molecular sieve seeds, the silicon source, the water, the aluminum source, and the colloidal stabilizer is 0.2-80:1-80:100:0-3:0-10.

3. The production method according to claim 2, wherein In step a), the solid content of the colloidal slurry is 2-40 wt%; and / or the silica-to-alumina molar ratio of the colloidal slurry is 10-500; and / or the content of the molecular sieve seeds in the colloidal slurry is 10-60 wt% of the total solid oxides; and / or the weight ratio of the molecular sieve seeds, the silicon source, the water, the aluminum source, and the colloidal stabilizer is 2-15:8-20:100:0-3:0.01-0.

2.

4. The preparation method according to claim 1 or 2, wherein the type of the molecular sieve seeds is selected from one or more of ZSM-5, ZSM-11, ZSM-35, ZSM-48, beta, Y, mordenite, and SAPO-34; and / or the silica-to-alumina molar ratio of the molecular sieve seeds is 5-1000.

5. The preparation method according to claim 4, wherein the type of the molecular sieve seeds is selected from one or more of ZSM-5, ZSM-11, and ZSM-35; and / or the silica-to-alumina molar ratio of the molecular sieve seeds is 200-500.

6. The preparation method according to claim 1 or 2, wherein the silicon source is selected from one or more of organosilicon grease, silica sol, and water glass; and / or the aluminum source is selected from at least one of aluminum isopropoxide, pseudoboehmite, aluminum oxide, sodium aluminate, aluminum nitrate, aluminum chloride, and aluminum sulfate; and / or the support is selected from one or more of aluminum oxide, silicon oxide, ceramic, glass, stainless steel, and plastic; and / or the shape of the support is selected from one or more of Raschig rings, porous preforms, and small balls; and / or the organic amine is selected from one or more of diamines, aliphatic amines, and quaternary ammonium salts.

7. The preparation method according to claim 6, wherein the silicon source is selected from at least one of silica sol, tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, and water glass; and / or the aluminum source is selected from one or more of sodium metaaluminate, aluminum sulfate, aluminum chloride, and aluminum nitrate; and / or the organic amine is selected from one or more of ethylenediamine, hexanediamine, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, propylamine, butylamine, tetraethylammonium bromide, tetrapropylammonium bromide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide.

8. The preparation method according to claim 7, wherein the silicon source is selected from silica sol, and the solid content of the silica sol is 10-40 wt%; and / or The organic amine is selected from one or more of triethylamine, tetrapropylammonium hydroxide, and ethylenediamine.

9. The preparation method according to claim 1 or 2, wherein the temperature of the heat treatment is 100-200°C; and / or the time of the heat treatment is 10-240 hours.

10. The preparation method according to claim 9, wherein the temperature of the heat treatment is 120-190°C; and / or the time of the heat treatment is 24-120 hours.

11. The preparation method according to claim 1 or 2, wherein step c) comprises placing the green body in an aqueous organic amine solution or steam of the aqueous organic amine solution at a temperature of 100-200°C for hydrothermal treatment for 10-240 hours; the aqueous organic amine solution has a mass ratio of organic amine to water of 1:0.5-10; and the weight ratio of organic amine to green body is 0.1-5:

1.

12. The preparation method according to claim 11, wherein step c) comprises placing the green body in an aqueous organic amine solution or steam of the aqueous organic amine solution at a temperature of 120-190°C for hydrothermal treatment for 24-120 hours; the aqueous organic amine solution has a mass ratio of organic amine to water of 1:0.6-5; and the weight ratio of organic amine to green body is 0.3-1.5:

1.

13. The molecular sieve membrane prepared by the preparation method of any one of claims 1-12.

14. The molecular sieve membrane according to claim 13, wherein the thickness of the molecular sieve membrane is 10-500 μm; and / or the molecular sieve is selected from one or more of ZSM-5, ZSM-11, ZSM-35, ZSM-48, β, Y, mordenite, and SAPO-34.

15. The molecular sieve membrane according to claim 14, wherein the thickness of the molecular sieve membrane is 30-200 μm; and / or the molecular sieve is selected from one or more of ZSM-5, ZSM-11, and ZSM-35.

16. Use of the molecular sieve membrane of any one of claims 13-15 in an olefin cracking reaction. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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