High-stability BTESE molecular sieve membrane as well as preparation method and application thereof

Abstract

The invention provides a high-stability BTESE molecular sieve membrane as well as a preparation method and application thereof, and belongs to the technical field of membrane separation materials. According to the method, a BTESE / i-BTESE molecular sieve membrane with high flux, high selectivity and high acid stability is successfully prepared on a macroporous tubular alpha-Al2O3 carrier through a layer-by-layer superposition method, and the method belongs to the technical field of membrane separation. The preparation method comprises the following steps: firstly, preparing BTESE swing sol by using a ph-swing method, then coating a tubular alpha-Al2O3 carrier with the BTESE swing sol by using a thermal coating mode, and then coating a middle layer of the BTESE swing sol with the BTESE sol by using a thermal coating mode, so as to obtain the BTESE / i-BTESE molecular sieve membrane with relatively good separation performance under the condition of dehydration of high-concentration acetic acid. The invention relates to a simple and effective method for preparing a high-flux and hydrothermal-stable BTES / i-BTESE molecular sieve membrane by taking porous organic silicon BTESE swinging sol as a middle layer, so that high-concentration acetic acid dehydration is effectively realized. The method is a promising candidate method for preparing the acetic acid dehydration membrane with high hydrothermal stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane separation materials, and relates to a BTESE / i-BTESE molecular sieve membrane with high acid resistance and hydrothermal stability, a preparation method and applications thereof, in particular to a layer-by-layer stacking preparation method of the BTESE / i-BTESE molecular sieve membrane, separation performance in a high acetic acid system, and their use in acetic acid / water separation. Background Art

[0002] Acetic acid is one of the 50 most important chemicals in industry and is widely used in the synthesis of compounds such as polyvinyl acetate, vinyl acetate, acetate and chloroacetic acid. At the same time, acetic acid is also used as an important industrial solvent and raw material in textile printing and dyeing, photographic drug manufacturing and rubber industry. Whether it is the traditional methanol carbonyl synthesis method or the biomass fermentation method to prepare acetic acid, the dehydration and refining of crude acetic acid is an indispensable unit process. Although water and acetic acid usually do not form azeotropes, due to the presence of tangent pinch points in acetic acid solution, it is usually necessary to set up multiple equilibrium stages in the distillation tower and use a higher reflux ratio, which leads to increased energy consumption. Although the traditional acetic acid dehydration method is mature and widely used, it has the disadvantages of high energy consumption, large equipment investment and secondary pollution. Therefore, it is particularly important to develop new environmentally friendly and energy-saving acetic acid dehydration and separation technology.

[0003] Pervaporation is a membrane separation technology used to separate liquid mixtures. It can be used to selectively permeate water or organic compounds. Compared with traditional distillation technology, the pervaporation process not only overcomes the limitations of thermodynamic vapor-liquid equilibrium, but also only requires latent heat of evaporation, and has lower energy consumption. Pervaporation technology has many advantages such as simple and flexible operation, low energy consumption, high separation efficiency, no introduction of other reagents, no need for secondary treatment of products, no secondary pollution, and easy to scale up. It is particularly suitable for isomers, heat-sensitive, near-boiling and azeotropic systems that are difficult or impossible to separate by traditional separation methods. It is considered to be one of the most important and promising high-tech technologies in the current industrial technology transformation.

[0004] Since acetic acid is easily soluble in water, the miscible system of the two is relatively stable and difficult to separate from water. In addition, acetic acid is highly corrosive, and high requirements are also placed on the acid resistance of the material. In the 21st century, microporous inorganic membranes have emerged as a new generation of membrane materials for separating molecular mixtures under harsh conditions. Since inorganic membranes have excellent acid resistance and adjustable hydrophilicity, they have great potential in the dehydration of acetic acid. Zeolite molecular sieve membranes are the largest family of inorganic pervaporation membrane materials, with adjustable hydrophilicity and sub-nanometer-sized molecular sieve pores, and provide strong preferential adsorption and rapid selective diffusion to achieve efficient molecular separation. At the same time, for the dehydration of organic matter or water vapor separation and water vapor heat recovery, the membrane material is required to have high stability.

[0005] Organic hybrid silica membranes have great potential for separation of various molecular mixtures in strong acidic harsh environments due to their high acid resistance, adjustable pore size and fast molecular diffusion rate. A large number of studies on the use of selective organic hybrid silica membranes for pervaporation have been reported in the literature, and have been widely used in acetic acid dehydration, seawater desalination, etc.: Waseem Raza et al. prepared organic hybrid silica membranes using BTESE as a precursor by the sol-gel method, and further post-treated the synthesized BTESE membrane with HCl to improve the separation performance of the BTESE membrane for acetic acid dehydration, with a permeate flux of 2.07 kg·m -2 ·h -1 , the separation coefficient is 780. The method of post-treatment with HCl improves the separation performance for acetic acid dehydration. The BTESE molecular sieve membranes used for desalination or dehydration of organic matter under neutral conditions or separation of acetic acid aqueous solution all use SiO2-ZrO2 as a transition layer to reduce the pore size of the carrier, that is, before pre-coating the BTESE sol particle size, a SiO2-ZrO2 transition layer is pre-coated on the carrier to reduce the pore size of the carrier, and the coated BTESE sol layer does not leak into the inside of the carrier pore size, thereby forming a BTESE / SiO2-ZrO2 composite membrane with separation selectivity, in which the separation layer is BTESE and the transition layer is SiO2-ZrO2 layer.

[0006] At present, the colloidal particle size of organic hybrid silica membrane sols such as BTESE sols prepared under acid catalysis at room temperature is usually below 10nm, and can only be coated on a carrier with a smaller pore size as a separation layer. In the present invention, by regulating the type of acid-base catalyst in the synthesis process of BTESE sol, the particle size of BTESE sol can be effectively adjusted within a large range of particle sizes, and the particle size can be regulated according to different separation requirements. Not only is the preparation simple, but BTESE also has high acid resistance and hydrothermal stability; considering that the SiO2-ZrO2 intermediate layer undergoes a certain hydrolysis reaction under hydrothermal conditions, resulting in high water content or reduced stability under acidic conditions, it cannot be used under harsh conditions. Therefore, the large-particle BTESE sol (referred to as i-BTESE sol) prepared under acid-base acid swing conditions can be used as a transition layer to prepare a BTSES / i-BTESE molecular sieve membrane, so that it has higher acid resistance and hydrothermal stability and a more suitable pore structure, and has better separation performance and acid stability when separating acetic acid / aqueous solution. Summary of the invention

[0007] To solve the above problems, the present invention provides a green, environmentally friendly, simple, fast and economical swing sol preparation method, and successfully prepares a middle layer with high flux, high selectivity and high acid stability by layer-by-layer stacking method, with large-particle BTESE obtained under acid-base acid catalysis conditions as the transition layer, and the small-particle BTESE sol obtained by hydrolysis with only acid as the catalyst as the separation layer membrane precursor liquid, and prepares a separation membrane from the transition layer to the separation functional layer, which is a BTESE membrane material, recorded as BTSES / i-BTESE molecular sieve membrane, and applies it to the dehydration of organic solvents under harsh conditions such as acetic acid, effectively realizing the dehydration of high-concentration acetic acid. The BTSES / i-BTESE molecular sieve membrane prepared by the preparation method proposed in the present invention has higher acid resistance and hydrothermal stability, the preparation method has low energy consumption and is green and environmentally friendly, the preparation process is simple and easy to operate, and has strong repeatability. The preparation process proposed in the present invention provides a promising reference scheme for the preparation of high-performance BTESE membranes, and has potential practical application feasibility.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for preparing a high-stability BTESE molecular sieve membrane, the preparation method comprising the following steps:

[0010] Step (1), pretreatment of the carrier: polish the carrier tube without macroporous defects until the carrier surface is uniform and smooth, then wash it with a mixed solution of hydrochloric acid and water, a sodium hydroxide solution and deionized water in sequence, finally dry the carrier fully, put it into a muffle furnace for calcination, and put it into a sealed bag for standby use;

[0011] Step (2), preparing i-BTESE sol: BTESE, ethanol and water are stirred at room temperature, hydrochloric acid is added to the mixed solution as a catalyst, and the mixed solution is vigorously stirred; then ammonia water is added as a catalyst and vigorously stirred; finally, hydrochloric acid is added to adjust the sol to an acidic pH.

[0012] Step (3), synthesis of i-BTESE membrane layer: the prepared i-BTESE sol is coated on the modified alumina carrier tube by a thermal coating method, and then placed in a muffle furnace for calcination.

[0013] Step (4), preparing BTESE sol: BTESE, ethanol and water are stirred and mixed at room temperature, hydrochloric acid is added to the mixture as a catalyst, and the mixed solution is vigorously stirred to obtain BTESE sol.

[0014] Step (5), synthesis of BTESE / i-BTESE molecular sieve membrane: The prepared BTESE sol is coated on the i-BTESE membrane prepared in step (3) by a thermal coating method, and then calcined in a muffle furnace to finally obtain an acid-resistant BTESE / i-BTESE molecular sieve membrane having acid resistance and hydrothermal stability.

[0015] The specific operation steps of the preparation method are as follows:

[0016] In the step (1), the carrier is an α-Al2O3 tube with an outer diameter of 12 mm, an inner diameter of 9 mm, and an average pore size of 2 to 3 μm. The carrier is polished with 800-mesh and 1500-mesh sandpapers in turn. The drying condition is drying at 50 to 80°C for 8 to 12 hours, and the calcination condition is calcining at 550°C for 6 hours. In the mixed solution of hydrochloric acid and aqueous solution, the molar ratio of hydrochloric acid is 1 mol / L.

[0017] In the step (2), the method for preparing i-BTESE sol is acid-base acid catalyst, which is recorded as pH-swing method; the molar ratio of raw materials for preparing BTESE swing sol is BTESE: H2O: HCl (first addition): NH3·H2O: HCl (second addition) = 1: 260: (0.1-1): (0.3-3): (0.24-2.4), wherein NH3·H2O: HCl (first addition) = 3-6, HCl (second addition): NH3·H2O = 0.8-1, and the equivalent weight of BTESE in the final composition of BTESE swing sol is maintained at 0.5-10wt.%. After hydrochloric acid is first added as a catalyst, the mixed solution is vigorously stirred at 40-60°C for 0.5-1.5h; after ammonia water is added as a catalyst, the mixed solution is vigorously stirred at room temperature for 0.5-1h; finally, hydrochloric acid is added to adjust the pH, and then the mixed solution is vigorously stirred at room temperature for 10-20min, and the final pH value of the mixed solution is 3-5. Taking the preparation of mg gi-BTESE sol with a total mass as an example, the molar ratio of each component is first determined, and the mass of BTESE added is 0.005m~0.1mg. The masses of other components are determined according to the addition amount of BTESE and the molar ratio of each component. The addition amount of solvent ethanol n=m-the sum of the masses of each reactant.

[0018] In the step (3), before preparing the membrane by layer-by-layer stacking method, the carrier is preheated in an oven at 175-185°C for 20-30 minutes, and the coating material used is a piece of degreased gauze. The coating concentration of i-BTESE is 0.5wt.%-10wt.%, and the muffle furnace calcination temperature of i-BTESE membrane preparation is 100-400°C, the calcination time is 20-40 minutes, and this operation is repeated 2-4 times.

[0019] In the step (4), the molar ratio of the raw materials for preparing the BTESE sol is BTESE:H2O:HCl=1:60:0.1, and the equivalent weight of BTESE in the final prepared BTESE acid sol is maintained at 0.5-10wt.%; the mixed solution is vigorously stirred at 25-35°C for 3-5h. Taking the preparation of a BTESE sol with a total mass of mg as an example, the molar ratio of each component is first determined, and the mass of the added BTESE is 0.005m~0.1mg. The mass of other components is determined according to the added amount of BTESE and the molar ratio of each component, and the added amount of solvent ethanol n=m-the sum of the masses of each reactant.

[0020] In the step (5), before preparing the membrane by layer-by-layer stacking method, the carrier is preheated in an oven at 175-185°C for 20-30 minutes, and the coating material used is a piece of absorbent gauze. The BTESE coating concentration is 0.5wt.%-5wt.%, and the muffle furnace calcination temperature of the BTESE membrane preparation is 200-300°C, the calcination time is 20-40 minutes, and this operation is repeated 2-4 times.

[0021] A method for preparing a high-stability BTESE molecular sieve membrane. The BTESE / i-BTESE molecular sieve membrane has a more suitable pore size, is suitable for molecular sieving, has a smooth and dense membrane surface, and has a thinner membrane layer.

[0022] The invention discloses an application of a high-stability BTESE molecular sieve membrane, which is applied to the dehydration of acetic acid solution. The permeation flux thereof is greatly improved, and the acid resistance and hydrothermal stability are enhanced. The membrane can be used for dehydration and refining of organic solutions under acidic conditions or with high water content, namely, it can be used for dehydration and refining of acetic acid solutions with a high-temperature acetic acid concentration in the range of 1-99wt.% to prepare high-purity acetic acid, and for dehydration and refining of organic water mixed solutions with a pH between 1-9 and 20wt.% of alcohols / water, ethers / water, ketones / water, phenols / water, esters / water, etc. to prepare high-purity organic matter. The concentration of water in the organic aqueous solution can be in a wide range of 0-100wt.%, and the separation performance of the BTESE / i-BTESE remains stable.

[0023] The present invention utilizes a pervaporation device to evaluate the pervaporation (PV) performance of a BTESE / i-BTESE molecular sieve membrane, wherein the acetic acid concentration on the feed side is 90-95wt.%, the operating temperature is 75-100°C, liquid nitrogen is used as a coolant to condense the permeate vapor, and a gas chromatograph (GC7900) is used to evaluate the composition of the feed and product.

[0024] The beneficial effects of the present invention are:

[0025] (1) The present invention provides a method for preparing a BTESE / i-BTESE molecular sieve membrane. The method requires low-priced chemical raw materials, has low energy consumption, and is environmentally friendly.

[0026] (2) The preparation process is simple and easy to operate, with strong repeatability. The preparation time of BTESE rocking sol is only 2 h, which makes the method of the present invention have excellent film-making efficiency.

[0027] (3) The BTESE / i-BTESE molecular sieve membrane prepared by the method of the present invention has excellent dehydration separation performance for organic solvents such as acetic acid. In addition, the BTESE / i-BTESE molecular sieve membrane prepared by the present invention not only exhibits high separation performance, but also exhibits good acid resistance and stability.

[0028] (4) The present invention effectively saves film-making costs, significantly shortens the film-making cycle, and fully embodies the concept of green chemistry. The preparation process proposed in the present invention is expected to provide a promising reference scheme for the preparation of acid-resistant films and has potential practical application feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the pervaporation test device, including vacuum pump ①, valve ②, pressure gauge ③, cold trap ④, silicone vacuum tube ⑤, membrane assembly ⑥, raw material side ⑦, magnetic stirring heating device ⑧;

[0030] Figure 2 This is a SEM image of the surface coated with i-BTESE interlayer film;

[0031] Figure 3 is a surface scanning electron micrograph of the BTESE / i-BTESE molecular sieve membrane synthesized in Example 1;

[0032] Figure 4 is a cross-sectional scanning electron micrograph of the BTESE / i-BTESE molecular sieve membrane synthesized in Example 1;

[0033] Figure 5 The pervaporation time stability of the BTESE / i-BTESE molecular sieve membrane synthesized in Example 1;

[0034] Figure 6 This is the pervaporation time stability of the BTESE / i-BTESE molecular sieve membrane synthesized in Example 2. DETAILED DESCRIPTION

[0035] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0036] Example 1

[0037] A method for preparing a high-stability BTESE molecular sieve membrane comprises the following steps:

[0038] (1) Pretreatment of the carrier: A carrier tube without macroporous defects was selected and polished with 800-mesh and 1500-mesh sandpaper in turn until the carrier surface was uniform and smooth, and then washed with hydrochloric acid / water solution, sodium hydroxide solution and deionized water in turn. Finally, the carrier was dried at 50°C for 12 h, calcined in a muffle furnace at 550°C for 6 h, and placed in a sealed bag for later use; wherein the carrier was an α-Al2O3 tube with an outer diameter of 12 mm, an inner diameter of 9 mm, and an average pore size of 2 to 3 μm.

[0039] (2) Preparation of i-BTESE sol: The raw material molar ratio is BTESE: H2O: HCl: NH3·H2O: HCL = 1: 260: 0.16: 0.48: 0.348, and the equivalent weight of BTESE is maintained at 0.5wt.%, to prepare 10gi-BTESE sol; the mass of BTESE added is 0.05g, and the mass of other components is determined according to the amount of BTESE added and the molar ratio of each component. The amount of solvent ethanol added is n = 10-the sum of the masses of each reactant. After adding hydrochloric acid (the first addition) as a catalyst, the mixed solution is vigorously stirred at 50°C for 1h; then ammonia water is added as a catalyst, and the mixed solution is vigorously stirred at room temperature for 0.67h; finally, hydrochloric acid (the second addition) is added to adjust the pH, and the mixture is vigorously stirred at room temperature for 10min, and the final pH value of the mixed solution is 4.

[0040] (3) Preparation of i-BTESE membrane: Before thermal coating, the carrier was preheated in an oven at 175°C for 0.5 h, the prepared i-BTESE sol was coated on the carrier tube using a piece of absorbent gauze, and then calcined in a muffle furnace at 300°C for 0.5 h, wherein the coating concentration of the i-BTESE sol was 10%, the number of coatings was 3, and step (3) was repeated three times to ensure a dense layer of the i-BTESE membrane.

[0041] (4) Preparation of BTESE sol: The molar ratio of raw materials is BTESE: H2O: HCl = 1: 60: 0.1, and the equivalent weight of BTESE is maintained at 0.5wt.%, to prepare 10g of BTESE sol; the mass of BTESE added is 0.05g, and the masses of other components are determined according to the amount of BTESE added and the molar ratio of each component, and the amount of solvent ethanol added is n = 10-the sum of the masses of each reactant; BTESE, ethanol and water are stirred and mixed at room temperature, and hydrochloric acid is added to the mixture as a catalyst, and the mixed solution is vigorously stirred at 35°C for 3h;

[0042] (5) Preparation of BTESE membrane: The prepared BTESE sol is coated on the i-BTESE membrane by a hot coating method. Before hot coating, the i-BTESE membrane is preheated in a 175°C oven for 0.5 h. The prepared BTESE sol is coated on the i-BTESE membrane using a piece of absorbent gauze, and then placed in a muffle furnace at 250°C for calcination for 0.5 h. The coating concentration of the BTESE sol is 5%. Step (5) is repeated 4 times to ensure the density of the BTESE / i-BTESE molecular sieve membrane.

[0043] The surface structure of i-BTESE molecular sieve membrane is composed of Figure 2 The analysis confirmed that the surface structure and cross-sectional structure of BTESE / i-BTESE molecular sieve membrane are Figure 3 and 4 The analysis confirmed that the acid resistance and hydrothermal stability of BTESE / i-BTESE molecular sieve membranes are Figure 5 Confirmed. Figure 2 It can be seen that the i-BTESE middle layer is flat and dense, and the carrier surface becomes dense and continuous; Figure 3 to Figure 4 It can be seen that the BTESE / i-BTESE molecular sieve membrane is flat and dense, and the carrier surface is dense and continuous; Figure 5 It can be seen that during the 8-hour pervaporation test, the separation factor of the BTESE / i-BTESE molecular sieve membrane was slightly reduced, and the permeation flux first decreased and then remained stable. The BTESE / i-BTESE molecular sieve membrane prepared in Example 1 was used for dehydration of acetic acid solution. The pervaporation (PV) performance of the BTESE / i-BTESE molecular sieve membrane was evaluated using a pervaporation device. The acetic acid concentration on the feed side was 90 wt.%, the operating temperature was 75 ° C, liquid nitrogen was used as a coolant to condense the permeate vapor, and a gas chromatograph (GC7890T) was used to evaluate the composition of the feed and product. The water flux was measured to be 1.67 kg·m -2 ·h -1 , the separation factor is 1791.36, and the water flux for 95 wt.% acetic acid aqueous solution at 90°C is 2.07 kg·m -2 ·h -1 , the separation factor is 2000.36.

[0044] Example 2

[0045] (1) Pretreatment of the carrier: A carrier tube without macroporous defects was selected and polished with 800-mesh and 1500-mesh sandpaper in turn until the carrier surface was uniform and smooth, and then washed with hydrochloric acid / water solution, sodium hydroxide solution and deionized water in turn. Finally, the carrier was dried at 80°C for 8 h, calcined in a muffle furnace at 550°C for 6 h, and placed in a sealed bag for later use; wherein the carrier was an α-Al2O3 tube with an outer diameter of 12 mm, an inner diameter of 9 mm, and an average pore size of 2 to 3 μm.

[0046] (2) Preparation of i-BTESE sol: The molar ratio of raw materials was BTESE: H2O: HCl: NH3·H2O: HCL = 1: 240: 0.1: 0.4: 0.36, and the equivalent weight of BTESE was kept at 5wt.% to prepare 10gi-BTESE sol; the mass of BTESE added was 0.5g, and the mass of other components was determined according to the amount of BTESE added and the molar ratio of each component. The amount of solvent ethanol added was n = 10-the sum of the masses of each reactant. After adding hydrochloric acid (the first addition) as a catalyst, the mixed solution was vigorously stirred at 40°C for 1.5h; then ammonia water was added as a catalyst, and the mixed solution was vigorously stirred at room temperature for 1h; finally, hydrochloric acid (the second addition) was added to adjust the pH, and the mixture was vigorously stirred at room temperature for 20min. The final pH value of the mixed solution was 5.

[0047] (3) Preparation of i-BTESE membrane: Before thermal coating, the carrier was preheated in an oven at 180°C for 0.42 h, the prepared i-BTESE sol was coated on the carrier tube using a piece of absorbent gauze, and then calcined in a muffle furnace at 400°C for 0.33 h, wherein the coating concentration of the i-BTESE sol was 1%, the number of coatings was 4, and step (3) was repeated three times to ensure a dense layer of the i-BTESE membrane.

[0048] (4) Preparation of BTESE sol: The molar ratio of raw materials is BTESE: H2O: HCl = 1: 60: 0.1, and the equivalent weight of BTESE is maintained at 5wt.%, to prepare 10g of BTESE sol; the mass of added BTESE is 0.5g, and the masses of other components are determined according to the amount of BTESE added and the molar ratio of each component, and the amount of solvent ethanol added is n = 10-the sum of the masses of each reactant; BTESE, ethanol and water are stirred at room temperature, and hydrochloric acid is added to the mixture as a catalyst, and the mixed solution is vigorously stirred at 25°C for 5h;

[0049] (5) Preparation of BTESE membrane: The prepared BTESE sol is coated on the i-BTESE membrane by a hot coating method. Before hot coating, the i-BTESE membrane is preheated in an oven at 180°C for 0.42 h. The prepared BTESE sol is coated on the i-BTESE membrane using a piece of absorbent gauze, and then placed in a muffle furnace at 300°C for calcination for 0.33 h. The coating concentration of the BTESE sol is 1%. Step (5) is repeated 4 times to ensure the compactness of the BTESE / i-BTESE molecular sieve membrane.

[0050] Figure 6 The pervaporation time stability test diagram of the BTESE / i-BTESE molecular sieve membrane prepared for this embodiment at 90 ℃ for 90wt.% acetic acid / water. As can be seen from the figure, during the entire 144-hour pervaporation test, the separation factor of the BTESE / i-BTESE molecular sieve membrane molecular sieve membrane is slightly reduced, and the permeation flux first decreases and then remains stable. The reason for the slight decrease in permeation flux may be that, during the pervaporation separation process, acetic acid molecules are adsorbed on the membrane surface, occupying adsorption sites, causing water molecules to be unable to penetrate the membrane better. In the entire pervaporation time stability test, the BTESE / i-BTESE molecular sieve membrane exhibits good stability.

[0051] Example 3

[0052] (1) Pretreatment of the carrier: A carrier tube without macroporous defects was selected and polished with 800-mesh and 1500-mesh sandpaper in turn until the carrier surface was uniform and smooth, and then washed with hydrochloric acid / water solution, sodium hydroxide solution and deionized water in turn. Finally, the carrier was dried at 60°C for 10 h, calcined in a muffle furnace at 550°C for 6 h, and placed in a sealed bag for later use; wherein the carrier was an α-Al2O3 tube with an outer diameter of 12 mm, an inner diameter of 9 mm, and an average pore size of 2 to 3 μm.

[0053] (2) Preparation of i-BTESE sol: The molar ratio of raw materials was BTESE: H2O: HCl: NH3·H2O: HCL = 1:240:0.2:1.2:1.2, and the equivalent weight of BTESE was maintained at 10wt.% to prepare 10gi-BTESE sol; the mass of BTESE added was 1g, and the masses of other components were determined according to the addition amount of BTESE and the molar ratio of each component. The addition amount of solvent ethanol was n = 10-the sum of the masses of each reactant; after adding hydrochloric acid (the first addition) as a catalyst, the mixed solution was vigorously stirred at 60°C for 0.5h; then ammonia water was added as a catalyst, and the mixed solution was vigorously stirred at room temperature for 0.5h; finally, hydrochloric acid was added (the second addition) to adjust the pH, and the mixture was vigorously stirred at room temperature for 20min. The final pH value of the mixed solution was 3.

[0054] (3) Preparation of i-BTESE membrane: Before thermal coating, the carrier was preheated in an oven at 185°C for 0.33 h, the prepared i-BTESE sol was coated on the carrier tube using a piece of absorbent gauze, and then calcined in a muffle furnace at 100°C for 0.67 h, wherein the coating concentration of the i-BTESE sol was 0.5%, the number of coatings was 3 times, and step (3) was repeated three times to ensure a dense layer of the i-BTESE membrane.

[0055] (4) Preparation of BTESE sol: The molar ratio of raw materials is BTESE: H2O: HCl = 1: 60: 0.1, and the equivalent weight of BTESE is maintained at 10wt.%, to prepare 10g of BTESE sol; the mass of added BTESE is 1g, and the masses of other components are determined according to the amount of BTESE added and the molar ratio of each component, and the amount of solvent ethanol added is n = 10-the sum of the masses of each reactant; BTESE, ethanol and water are stirred and mixed at room temperature, and hydrochloric acid is added to the mixture as a catalyst, and the mixed solution is vigorously stirred at 30°C for 4h;

[0056] (5) Preparation of BTESE membrane: The prepared BTESE sol is coated on the i-BTESE membrane by a hot coating method. Before hot coating, the i-BTESE membrane is preheated in an oven at 185°C for 0.33 h. The prepared BTESE sol is coated on the i-BTESE membrane using a piece of absorbent gauze, and then placed in a muffle furnace at 200°C for calcination for 0.67 h. The coating concentration of the BTESE sol is 0.5%. Step (5) is repeated 4 times to ensure the compactness of the BTESE / i-BTESE molecular sieve membrane.

[0057] The BTESE / i-BTESE molecular sieve membrane prepared in Example 3 was used for dehydration of acetic acid solution. The pervaporation (PV) performance of the BTESE / i-BTESE molecular sieve membrane was evaluated using a pervaporation device. The acetic acid concentration on the feed side was 90 wt.%, the operating temperature was 75 ° C, liquid nitrogen was used as a coolant to condense the permeate vapor, and a gas chromatograph (GC7890T) was used to evaluate the composition of the feed and product. The water flux was measured to be 1.16 kg·m -2 ·h -1 , the separation factor is 281.24, and the water flux at 100 °C is 3.16 kg·m -2 ·h -1 , the separation factor is 300.24.

[0058] The above-described embodiments merely express the implementation methods of the present invention, but they should not be understood as limiting the scope of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for preparing a high-stability BTESE molecular sieve membrane, characterized in that: The preparation method comprises the following steps: Step (1), pretreatment of the carrier: grinding, cleaning, drying the carrier tube, and then calcining it; Step (2), preparing i-BTESE sol: at room temperature, BTESE, ethanol and water are stirred and mixed, hydrochloric acid is added to the mixed solution as a catalyst, and the mixture is stirred vigorously; then ammonia water is added as a catalyst, and the mixture is stirred vigorously; Finally, hydrochloric acid was added to adjust the sol to an acidic pH to obtain i-BTESE sol; Step (3), synthesizing the i-BTESE membrane layer: coating the i-BTESE sol on the carrier tube obtained in step (1), and calcining in a muffle furnace to obtain the i-BTESE membrane; Step (4), preparing BTESE sol: at room temperature, BTESE, ethanol and water are stirred and mixed, hydrochloric acid is added to the mixture as a catalyst, and the mixture is stirred vigorously to obtain BTESE sol; Step (5), synthesizing BTESE / i-BTESE molecular sieve membrane: coating the BTESE sol on the i-BTESE membrane prepared in step (3), placing it in a muffle furnace for calcination, and obtaining an acid-resistant and hydrothermally stable BTESE / i-BTESE molecular sieve membrane.

2. The method for preparing a high-stability BTESE molecular sieve membrane according to claim 1, characterized in that: The step (1) is specifically as follows: grinding the carrier tube without macroporous defects until the carrier surface is uniform and smooth, washing it with a mixed solution of hydrochloric acid and water, a sodium hydroxide solution and deionized water in sequence, and calcining the carrier in a muffle furnace after it is fully dried, wherein the drying temperature is 50-80° C., the drying time is 8-12 hours, the calcination temperature is 550° C., and the calcination time is 6 hours.

3. The method for preparing a high-stability BTESE molecular sieve membrane according to claim 2, characterized in that: The carrier tube is an α-Al2O3 tube; in the mixed solution of hydrochloric acid and aqueous solution, the molar ratio of hydrochloric acid is 1 mol / L.

4. The method for preparing a high-stability BTESE molecular sieve membrane according to claim 1, characterized in that: In the step (2), the method for preparing the i-BTESE sol is the pH-swing method, which is specifically as follows: The raw materials for preparing i-BTESE sol include BTESE, H2O, HCl, NH3·H2O, and ethanol, wherein HCl is added twice; Assuming that the total mass of the i-BTESE sol is Mg, the total mass of BTESE, H2O, HCl, and NH3·H2O is Ng, the amount of ethanol added is M-Ng; the equivalent weight of BTESE in the final i-BTESE sol is maintained at 0.5-10wt.%; the molar ratio of the added amounts of BTESE, H2O, HCl, and NH3·H2O is: BTESE: H2O: first added HCl: NH3·H2O: second added HCl = 1: 260: (0.1-1): (0.3-3)：(0.24-2.4)； After the first addition of hydrochloric acid, the mixed solution was vigorously stirred at 40-60°C for 0.5-1.5h; after the addition of ammonia water, the mixed solution was vigorously stirred at room temperature for 0.5-1h; after the second addition of hydrochloric acid, the mixed solution was vigorously stirred at room temperature for 10-20min, and the final pH value of the mixed solution was 3-5.

5. The method for preparing a high-stability BTESE molecular sieve membrane according to claim 1, characterized in that: In the step (3), the i-BTESE sol is coated on the carrier tube obtained in the step (1) by using a hot coating method; in the step (5), the BTESE sol is coated on the i-BTESE membrane prepared in the step (3) by using a hot coating method.

6. The method for preparing a high-stability BTESE molecular sieve membrane according to claim 1, characterized in that: In the step (3), before preparing the i-BTESE membrane by layer-by-layer stacking method, the carrier is preheated in an oven at 175-185°C for 20-30 minutes, the coating material is a piece of absorbent gauze; the coating concentration of the i-BTESE sol is 0.5wt.%-10wt.%; the calcination temperature is 100-400°C, and the calcination time is 20-40 minutes; the above operation is repeated multiple times.

7. The method for preparing a high-stability BTESE molecular sieve membrane according to claim 1, characterized in that: In the step (4): The raw materials for preparing BTESE sol include BTESE, H2O, HCl, and ethanol, and the mixed solution is vigorously stirred at 25-35°C for 3-5h; Assuming that the total mass of the BTESE sol is Mg, and the total mass of BTESE, H2O, and HCl is Ng, the amount of ethanol added is M-Ng; the equivalent weight of BTESE in the final prepared BTESE sol is maintained at 0.5-10wt.%; the molar ratio of the added amounts of BTESE, H2O, and HCl is: BTESE:H2O:HCl=1: 60：0.1。 8. The method for preparing a high-stability BTESE molecular sieve membrane according to claim 1, characterized in that: In the step (5), before preparing the membrane by layer-by-layer stacking method, the carrier is preheated in an oven at 175-185°C for 20-30 minutes, and the coating material used is a piece of absorbent gauze; the coating concentration of the BTESE sol is 0.5wt.%-5wt.%; the calcination temperature is 200-300°C, and the calcination time is 20-40 minutes; the above operation is repeated multiple times.

9. A high-stability BTESE molecular sieve membrane, characterized in that: The BTESE / i-BTESE molecular sieve membrane is prepared by the preparation method described in any one of claims 1-8.

10. An application of the hydrothermally stable BTESE molecular sieve membrane according to claim 9, characterized in that: The hydrothermally stable BTESE / i-BTESE molecular sieve membrane is applied to dehydration of acetic acid solution.

Images