阅读说明：本技术 一种纯硅沸石膜及其制备方法和应用 (Pure silicon zeolite membrane and preparation method and application thereof ) 是由 刘金梅 吴苏州 陈俊孚 任嵬 于 2021-09-18 设计创作，主要内容包括：本发明公开了一种纯硅沸石膜及其制备方法和应用,所述制备方法先以适宜尺寸的沸石晶粒修饰多孔载体,然后在修饰晶粒的载体表面涂覆硅溶胶,在不使用传统水热晶化液的条件下,将传统晶化液中的硅源和模板剂分别供给,并精确调控模板剂蒸汽压力和去离子水的压力直接制备纯硅沸石膜,提高了材料利用率,优化纯硅沸石膜的结构,克服了传统水热晶化制备沸石膜缺陷多、浪费原料等问题,仅通过精确控制模板剂和去离子水压力即可控制纯硅沸石膜的微观结构。通过本发明的方法制备得到的纯硅沸石膜缺陷少、成品率高,在水醇混合物分离中表现出优异的性能。(The invention discloses a pure silicon zeolite membrane and a preparation method and application thereof, wherein the preparation method comprises the steps of modifying a porous carrier by zeolite crystal grains with proper sizes, then coating silica sol on the surface of the carrier with the modified crystal grains, respectively supplying a silicon source and a template agent in the traditional crystallization liquid under the condition of not using the traditional hydrothermal crystallization liquid, and directly preparing the pure silicon zeolite membrane by accurately regulating and controlling the steam pressure of the template agent and the pressure of deionized water, thereby improving the material utilization rate, optimizing the structure of the pure silicon zeolite membrane, overcoming the problems of more defects, raw material waste and the like of the traditional hydrothermal crystallization preparation of the zeolite membrane, and controlling the microstructure of the pure silicon zeolite membrane only by accurately controlling the pressure of the template agent and the pressure of the deionized water. The pure silicalite membrane prepared by the method has few defects and high yield, and shows excellent performance in separation of water-alcohol mixtures.)

1. A preparation method of a pure silicalite membrane is characterized by comprising the following steps:

(1) pretreatment of the porous carrier: under the assistance of ultrasonic waves, sequentially washing the carrier by using dilute hydrochloric acid, acetone and deionized water, and then drying to obtain a pretreated porous carrier;

(2) coating a zeolite seed layer: coating the seed crystal suspension prepared in advance on the porous carrier pretreated in the step (1) to obtain the porous carrier coated with the seed crystal layer;

(3) coating silica sol: immersing the porous carrier coated with the seed crystal layer obtained in the step (2) into silica sol to obtain a porous carrier coated with the silica sol;

(4) hydrothermal synthesis of zeolite membrane: placing the porous carrier coated with the silica sol obtained in the step (3) in a hydrothermal kettle containing excessive deionized water, communicating the hydrothermal kettle with a template agent steam generator through a pipeline, controlling the temperature of the hydrothermal kettle and the pressure of the template agent steam generator, performing hydrothermal synthesis, and washing and drying a product after the hydrothermal synthesis is finished;

(5) high-temperature treatment: and (4) roasting the product dried in the step (4) at high temperature to remove the template agent, thus obtaining the pure silicalite membrane.

2. The method according to claim 1, wherein the porous support in the step (1) is tubular and is selected from the group consisting of α -Al₂O₃、TiO₂Or ZrO₂The average pore diameter of the porous carrier is 0.1-5 mu m, and the wall thickness is 0.5-2 mm.

3. The method according to claim 1, wherein the drying temperature in the step (1) is 100 to 150 ℃.

4. The production method according to claim 1, wherein the mass concentration of the seed crystal suspension in the step (2) is 1 to 3.5%.

5. The preparation method according to claim 1, wherein the coating method of the zeolite seed crystals in the step (2) is a dip coating method, and the specific steps are as follows: and (3) immersing the pretreated porous carrier into the seed crystal suspension for a certain time, then taking out, and drying at the temperature of 200-300 ℃.

6. The preparation method according to claim 1, wherein the silica sol is commercially available in a mass concentration of 15 to 50% in step (3), the silica sol is coated at least once, and the silica sol-coated porous support is treated at 300-600 ℃ for 1 to 5min after each coating.

7. The method according to any one of claims 1 to 6, wherein the template in step (4) is tetrapropylammonium hydroxide.

8. The preparation method according to any one of claims 1 to 7, wherein the hydrothermal synthesis temperature in the step (4) is 120-180 ℃, the synthesis time is 10-36 h, and the pressure of the hydrothermal kettle is controlled to be equal to that of the template steam generator.

9. The method according to any one of claims 1 to 8, wherein the high-temperature calcination temperature in step (5) is 450-.

10. A pure silicalite membrane prepared by the preparation method of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of chemical separation, and particularly relates to a pure silicon zeolite membrane and a preparation method and application thereof.

Background

The zeolite molecular sieve membrane material is a aluminosilicate crystal with a regular microporous structure, has the advantages of excellent thermal stability, mechanical stability, microbial corrosion resistance, oxidation resistance and the like inherent in inorganic membrane materials, is more unique in a uniform and regular crystalline pore system and adjustable surface properties, and endows the zeolite molecular sieve membrane with incomparable uniqueness such as high selectivity, high flux, solvent resistance, high temperature resistance and the like, so that the zeolite molecular sieve membrane material becomes one of the most potential and promising membranes.

The pure silicon zeolite membrane has three-dimensional intercommunicated pore passages which comprise elliptical pores connected into zigzag passages in the direction of the axis a, basically circular pores linearly extend in the direction of the axis b to form straight passages, no passages are opened in the direction of the axis c, but molecules can be continuously and alternately diffused through the passages in the direction of the axis a and the passages in the direction of the axis b. At present, methods for preparing pure silicalite membranes are mainly classified into in-situ growth methods and secondary growth (seeding) methods. The secondary growth method is to coat zeolite crystals as seed crystals on the surface of a carrier, and to crystallize and grow the zeolite crystals in a synthetic solution under certain conditions to prepare a continuous and compact zeolite membrane.

The basic steps of zeolite membrane synthesis can be summarized as: 1) treating and preparing a carrier; 2) preparing a reaction solution; 3) reacting the carrier and the reaction solution under certain conditions to form a film; 4) and (5) post-reaction treatment. The key of the research of the zeolite membrane is to prepare a compact membrane with large permeation quantity and high separation coefficient. The separation performance of zeolite membranes depends mainly on the preparation method and conditions, and furthermore, the properties of the support are important influencing factors. There are researchers through porous alpha-Al₂O₃The surface physicochemical property of the carrier is changed by the treatment or modification of the carrier, and the pure silicon MFI molecular sieve membrane (Zhang Baoquan, Sunjiang, Zheng Ben Yao, etc.) is synthesized by the in-situ hydrothermal crystallization method and the CO thereof is synthesized₂/N₂Study of Mixed gas separation Performance [ J]Membrane science and technology, 2017,37(2): 26-31.); researchers also have synthesized Silicalite-1 zeolite membranes on porous stainless steel carrier tubes by two-step temperature-changing hydrothermal method (Sun Wei, Yangjianhua, Wang Aifang)And the pure silicon molecular sieve membrane prepared by two-step temperature-changing hydrothermal synthesis and the permeability thereof [ J]The proceedings of Process engineering, 2008,8(3): 599-; the patent (CN105080360B) aims at the separation of low-concentration organic matter aqueous solution, takes porous alumina ceramics as a carrier, prepares and obtains a pure silicon molecular sieve membrane with an MFI crystal structure on the surface, and comprises the following synthetic steps: 1) preparing synthetic liquid to form seed crystal; 2) coating seed crystals; 3) preparing a synthetic solution; 4) carrying out hydro-thermal synthesis; 5) and (5) drying at high temperature. Despite the numerous methods reported in the prior art for the preparation of pure silicalite membranes, the synthesis of zeolite membranes with high flux, high separation factor is a challenging task, and improvements based on existing hydrothermal synthesis processes in particular are still sought after. Therefore, the applicant hopes to provide an improved method for preparing pure silicalite film by supplying the silicon source and the template agent in the conventional crystallization liquid separately and matching with the method of precisely regulating the vapor pressure of the template agent.

Disclosure of Invention

The invention aims to provide a pure silicalite membrane which has good separation performance in the separation of ethanol and water; another object of the present application is to provide a method for preparing a pure silicalite film, which overcomes the problems of the traditional hydrothermal crystallization method such as a large number of defects in zeolite film preparation, waste of raw materials, and the like.

In order to achieve the purpose, the technical scheme adopted by the application is as follows:

a preparation method of a pure silicalite membrane specifically comprises the following steps:

(1) pretreatment of the porous carrier: under the assistance of ultrasonic waves, sequentially washing the carrier by using dilute hydrochloric acid, acetone and deionized water, and then drying to obtain a pretreated porous carrier;

(2) coating a zeolite seed layer: coating the seed crystal suspension prepared in advance on the porous carrier pretreated in the step (1) to obtain the porous carrier coated with the seed crystal layer;

(3) coating silica sol: immersing the porous carrier coated with the seed crystal layer obtained in the step (2) into silica sol to obtain a porous carrier coated with the silica sol;

(4) hydrothermal synthesis of zeolite membrane: placing the porous carrier coated with the silica sol obtained in the step (3) in a hydrothermal kettle containing excessive deionized water, communicating the hydrothermal kettle with a template agent steam generator through a pipeline, controlling the temperature of the hydrothermal kettle and the pressure of the template agent steam generator, performing hydrothermal synthesis, and washing and drying a product after the hydrothermal synthesis is finished;

(5) high-temperature treatment: and (4) roasting the product dried in the step (4) at high temperature to remove the template agent, thus obtaining the pure silicalite membrane.

Further, in the step (1), the porous carrier is tubular and is selected from alpha-Al₂O₃、TiO₂Or ZrO₂The average pore diameter of the porous carrier is 0.1-5 mu m, and the wall thickness is 0.5-2 mm.

Further, the drying temperature in the step (1) is 100-150 ℃.

Further, the mass concentration of the seed crystal suspension in the step (2) is 1-3.5%.

Further, the coating method of the zeolite seed crystal in the step (2) is a dip coating method, and the specific steps are as follows: and (3) immersing the pretreated porous carrier into the seed crystal suspension for a certain time, then taking out, and drying at the temperature of 200-300 ℃.

Further, the silica sol in the step (3) is commercially available, the mass concentration is 15-50%, the silica sol is coated at least once, and the porous carrier coated with the silica sol is treated at the temperature of 300-600 ℃ for 1-5min after each coating.

Further, in the step (4), the template agent is tetrapropylammonium hydroxide.

Further, in the step (4), the hydrothermal synthesis temperature is 120-180 ℃, the synthesis time is 10-36 hours, and meanwhile, the pressure of the hydrothermal kettle and the pressure of the template agent steam generator are controlled to be equal.

Further, the high-temperature roasting temperature in the step (5) is 450-650 ℃, the atmosphere is air, and the time is 1.5-5 h.

The application also claims the pure silicalite membrane prepared by the method and the application of the pure silicalite membrane in water/ethanol separation.

Compared with the prior art, the invention has the following effects and benefits:

(1) the pure silicon zeolite membrane is prepared by respectively supplying the template agent and the silicon source, so that the utilization rate of the material can be improved, and the thickness of the zeolite membrane can be flexibly regulated and controlled; meanwhile, the original mode that the template agent is directly mixed into the synthetic liquid is changed, the steam supply of the template agent can be realized by accurately regulating and controlling the temperature of a template agent steam generator, so that the template agent is fully contacted and formed with the tubular carrier, the full growth of the seed crystal is promoted, the defects of the zeolite membrane are further reduced, and the structure and the performance of the zeolite membrane are improved.

(2) The pure silicalite membrane prepared by the method has few defects and high yield, and shows excellent performance in separation of water/ethanol mixture.

(3) The preparation method of the pure silicon zeolite membrane has simple process, energy conservation and environmental protection, can be popularized to the preparation of other types of zeolite membranes, and is suitable for the scale production of the zeolite membranes.

(4) The pure silicalite membrane prepared by the method has good separation performance and good application prospect.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. Of course, the specific embodiments described herein are merely illustrative of the invention and are not intended to be limiting.

In the present invention, the percentages referred to are percentages by mass, unless otherwise indicated.

The pure silicalite membrane prepared by the method is tested on a self-made small test device, trace water in ethanol is removed by pervaporation through a vacuum pumping method, and the pressure of a certain permeation side is kept at about 200-250 pa. The composition and content of the raw materials and the permeated materials are detected by gas chromatography.

Example 1

A preparation method of a pure silicalite membrane specifically comprises the following steps:

(1) pretreatment of the porous carrier: selecting tubular porous aluminum oxide with the average pore diameter of 0.5 mu m, the inner diameter of 10mm and the outer diameter of 12mm as a carrier, cleaning the carrier for 20min by using 10% dilute hydrochloric acid under the assistance of ultrasonic waves, treating the carrier in acetone for 15 min, cleaning the carrier for 20min by using deionized water, and removing impurities on the surface of the carrier; finally, drying the carrier tube at 120 ℃ for later use;

(2) coating a zeolite seed layer: dispersing pure silicon zeolite with the particle size of about 300nm in deionized water to form seed crystal suspension with the concentration of 2%, sealing two ends of the impurity-removed carrier tube, immersing the carrier tube in the seed crystal liquid, keeping the temperature for 30s, taking out the carrier tube, and further carrying out heat treatment at 220 ℃ for 1 h;

(3) coating silica sol: selecting commercial silica sol with the concentration of 25%, placing in a 200ml measuring cylinder, sealing two ends of the tubular carrier coated with the seed crystal, soaking in the silica sol for 3min, taking out, performing heat treatment at 350 ℃ for 1min, and repeating the operation for 1 time;

(4) hydrothermal synthesis of zeolite membrane: placing the carrier coated with the silica sol in a reaction kettle, communicating the carrier with the outside of the reaction kettle through a stainless steel pipeline and communicating the carrier with a tetrapropylammonium hydroxide steam generator, injecting 80% of deionized water into a hydrothermal kettle, heating the kettle to 170 ℃, further raising the temperature of a template agent steam generator, keeping the steam pressure and the template agent steam pressure the same, and starting to crystallize and synthesize a pure silica zeolite membrane;

(5) high-temperature treatment: after the synthesis time is 12h, the membrane tube in the reaction kettle is taken out, the membrane tube is repeatedly cleaned by deionized water, and finally, the membrane tube is roasted at 550 ℃ for 1.5h to remove the template agent, so that the pure silicon zeolite membrane is obtained.

The water/ethanol separation performance test result of the zeolite membrane is as follows: the permeation side is vacuumized to provide driving force, and the ethanol permeation flux of the pure silicalite membrane is 2.2kg/m under the conditions of the osmotic pressure of 200pa, the temperature of 50 ℃ and the ethanol concentration of 5 percent²The ethanol/water separation factor was 225.

Example 2

A preparation method of a pure silicalite membrane specifically comprises the following steps:

(1) pretreatment of the porous carrier: selecting tubular porous zirconium dioxide with the average pore diameter of 2 mu m, the inner diameter of 10mm and the outer diameter of 14mm as a carrier, washing the carrier for 30min by using dilute hydrochloric acid with the concentration of 5% under the assistance of ultrasonic waves, treating the carrier in acetone for 10min, washing the carrier for 30min by using deionized water, removing impurities on the surface of the carrier, and finally drying the carrier tube at 150 ℃ for later use;

(2) coating a zeolite seed layer: dispersing pure silicon zeolite with the particle size of about 1000nm in deionized water to form a seed crystal suspension with the concentration of 1%, sealing two ends of the impurity-removed carrier tube, immersing the carrier tube in the seed crystal liquid, keeping the carrier tube for 30s, taking out the carrier tube, and further carrying out heat treatment at 250 ℃ for 1 h;

(3) coating silica sol: selecting commercial silica sol with the concentration of 18 percent, placing the silica sol into a 200ml measuring cylinder, sealing two ends of the tubular carrier coated with the seed crystal, soaking the tubular carrier into the silica sol for 5min, taking out the tubular carrier, performing heat treatment at 480 ℃ for 3min, and repeating the operation for 2 times;

(4) hydrothermal synthesis of zeolite membrane: placing the carrier coated with the silica sol in a reaction kettle, communicating the carrier with the outside of the reaction kettle through a stainless steel pipeline and communicating the carrier with a tetrapropylammonium hydroxide steam generator, injecting 80% of deionized water into a hydrothermal kettle, raising the temperature of the kettle to 120 ℃, further raising the temperature of a template agent steam generator, keeping the steam pressure and the template agent steam pressure the same, and starting to crystallize and synthesize the pure silica zeolite membrane;

(5) high-temperature treatment: after the synthesis time is 18h, the membrane tube in the reaction kettle is taken out, repeatedly cleaned by deionized water, and finally calcined at 650 ℃ for 2h to remove the template agent, thus obtaining the pure silicon zeolite membrane.

The water/ethanol separation performance test result of the zeolite membrane is as follows: the permeation side is vacuumized to provide driving force, and the ethanol permeation flux of the pure silicalite membrane is 2.4kg/m under the conditions of the osmotic pressure of 200pa, the temperature of 50 ℃ and the ethanol concentration of 5 percent²The ethanol/water separation factor was 207.

Example 3

A preparation method of a pure silicalite membrane specifically comprises the following steps:

(1) pretreatment of the porous carrier: selecting tubular porous titanium oxide with the average pore diameter of 0.2 mu m, the inner diameter of 10mm and the outer diameter of 11mm as a carrier, washing the carrier for 10min by using 10% dilute hydrochloric acid under the assistance of ultrasonic waves, treating the carrier in acetone for 5min, washing the carrier for 20min by using deionized water, removing impurities on the surface of the carrier, and finally drying the carrier tube at 100 ℃ for later use;

(2) coating a zeolite seed layer: dispersing pure silicon zeolite with the particle size of about 50nm in deionized water to form a seed crystal suspension with the concentration of 3.5%, sealing two ends of the impurity-removed carrier tube, immersing the carrier tube in the seed crystal liquid, taking out the carrier tube after keeping the carrier tube for 60s, and further carrying out heat treatment for 1h at 200 ℃;

(3) coating silica sol: selecting commercial silica sol with the concentration of 15%, placing the commercial silica sol into a 200ml measuring cylinder, sealing two ends of the tubular carrier coated with the seed crystal, soaking the tubular carrier into the silica sol for 3min, taking out the tubular carrier, performing heat treatment at 600 ℃ for 5min, and repeating the operation for 1 time;

(4) hydrothermal synthesis of zeolite membrane: placing the carrier coated with the silica sol in a reaction kettle, taking note that one end of the carrier is closed, and the other end is communicated to the outside of the reaction kettle through a stainless steel pipeline and communicated with a tetrapropylammonium hydroxide steam generator, injecting 80% deionized water into a hydrothermal kettle, raising the temperature of the kettle to 150 ℃, further raising the temperature of a template agent steam generator, keeping the steam pressure and the steam pressure of the template agent the same, and starting to crystallize and synthesize the pure silica zeolite membrane;

(5) high-temperature treatment: after the synthesis time is 18h, the membrane tube in the reaction kettle is taken out, repeatedly cleaned by deionized water, and finally calcined at 600 ℃ for 3h to remove the template agent, thus obtaining the pure silicon zeolite membrane.

The water/ethanol separation performance test result of the zeolite membrane is as follows: the permeation side is vacuumized to provide driving force, and the ethanol permeation flux of the pure silicalite membrane is 3.2kg/m under the conditions of the osmotic pressure of 200pa, the temperature of 50 ℃ and the ethanol concentration of 5 percent²The ethanol/water separation factor was 213.

Example 4

A preparation method of a pure silicalite membrane specifically comprises the following steps:

(1) pretreatment of the porous carrier: selecting tubular porous aluminum oxide with the average pore diameter of 0.6 mu m, the inner diameter of 10mm and the outer diameter of 13mm as a carrier, cleaning the carrier for 10min by using 15% dilute hydrochloric acid under the assistance of ultrasonic waves, treating the carrier in acetone for 20min, cleaning the carrier for 20min by using deionized water, removing impurities on the surface of the carrier, and finally drying the carrier tube at 100 ℃ for later use;

(2) coating a zeolite seed layer: dispersing pure silicon zeolite with the particle size of about 200nm in deionized water to form a seed crystal suspension with the concentration of 3%, sealing two ends of the impurity-removed carrier tube, immersing the carrier tube in the seed crystal liquid, keeping the temperature for 60s, taking out the carrier tube, and further carrying out heat treatment at 300 ℃ for 1 h;

(3) coating silica sol: selecting commercially available silica sol with concentration of 45%, placing in 200ml graduated cylinder, sealing two ends of the tubular carrier coated with the seed crystal, soaking in the silica sol for 3min, taking out, heat treating at 400 deg.C for 1min, and repeating the operation for 3 times;

(4) hydrothermal synthesis of zeolite membrane: placing the carrier coated with the silica sol in a reaction kettle, communicating the carrier with the outside of the reaction kettle through a stainless steel pipeline and communicating the carrier with a tetrapropylammonium hydroxide steam generator, injecting 80% of deionized water into a hydrothermal kettle, heating the kettle to 100 ℃, further raising the temperature of a template agent steam generator, keeping the steam pressure and the template agent steam pressure the same, and starting to crystallize and synthesize a pure silica zeolite membrane;

(5) high-temperature treatment: after the synthesis time is 32h, the membrane tube in the reaction kettle is taken out, repeatedly cleaned by deionized water, and finally calcined at 550 ℃ for 3h to remove the template agent, thus obtaining the pure silicon zeolite membrane.

The water/ethanol separation performance test result of the zeolite membrane is as follows: the permeation side is vacuumized to provide driving force, and the ethanol permeation flux of the pure silicalite membrane is 2.7kg/m under the conditions of the osmotic pressure of 200pa, the temperature of 50 ℃ and the ethanol concentration of 5 percent²The ethanol/water separation factor was 205.

The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalents, improvements, etc. that are within the spirit and principle of the present invention should be included in the protection scope of the present invention.