CN109433022B

CN109433022B - Preparation method of alcohol permeable membrane material

Info

Publication number: CN109433022B
Application number: CN201811613504.5A
Authority: CN
Inventors: 不公告发明人
Original assignee: Individual
Current assignee: Wang Lingjuan
Priority date: 2018-12-27
Filing date: 2018-12-27
Publication date: 2021-12-24
Anticipated expiration: 2038-12-27
Also published as: CN109433022A

Abstract

The invention discloses a preparation method of an alcohol permeable membrane material, which is characterized in that zeolite particles with proper particle size and aggregate are mixed to prepare a carrier, and a tubular membrane material is further synthesized by hydrothermal synthesis.

Description

Preparation method of alcohol permeable membrane material

Technical Field

The invention relates to a preparation method of a membrane material, in particular to a preparation method of a tubular ceramic membrane for alcohol permeation in industrial alcohol-water separation.

Background

The anhydrous organic solvent is indispensable in the fields of petrochemical industry, fine chemical industry, pharmaceutical chemical industry, daily chemical industry, new energy and the like, so that the anhydrous organic solvent is obtained by separating a small amount of or trace water in the organic solvent, and is one of the most important and common unit processes in the fields. When the mixture of the organic solvent and water reaches a near boiling point and a constant boiling point, due to the restriction of azeotropic equilibrium, the further separation of the organic solvent and the water cannot be realized by adopting a simple distillation method, the traditional process adopts the technologies of constant boiling distillation, extractive distillation, pressurized distillation or zeolite adsorption and the like to separate the water in the mixture, and further obtains the water-free organic solvent.

The pervaporation membrane technology developed in recent decades is generally accepted by people due to the advantages of low energy consumption, no introduction of a third component, less pollution discharge and the like in organic solvent dehydration, particularly alcohol application. In the currently industrialized pervaporation membranes, zeolite membranes get more and more attention due to the regular pore channel structures and good physical and chemical stability, and a plurality of enterprises at home and abroad successively develop research, development and industrialized application of the zeolite membranes. Among them, for the water permeable membrane, it has been industrially applied, such as NaA zeolite membrane, and for the alcohol permeable membrane, it has not been industrially applied. For preparing the Silicalite-1 zeolite membrane, common preparation methods comprise an in-situ synthesis method and a secondary growth method, and compared with the in-situ synthesis method, the secondary growth method has higher controllability on the crystallization process of the zeolite membrane, and can prepare a relatively compact and flat membrane layer in relatively short time, so that the method is mostly adopted in industrial application. However, in the secondary growth method, a layer of seed crystals is coated on the carrier in advance before hydrothermal crystallization, and then the carrier is dried, so that the carrier needs to be transported between a seed crystal coating container and a drying container and among a plurality of containers before entering the reaction kettle for hydrothermal crystallization. However, in the industrial production, a plurality of tubular or hollow fiber carriers need to be operated together, and the seed layer coated on the carrier is easy to crack or even fall off due to factors such as bump, so that the yield of the membrane is reduced, which is one reason why the zeolite membrane is difficult to industrialize. Therefore, a new preparation method is needed to overcome the defects of the secondary growth method for preparing the Silicalite-1 zeolite membrane.

Disclosure of Invention

The invention provides a preparation method of an alcohol permeable membrane material, which is characterized by comprising the following steps:

(1) uniformly mixing alpha-alumina powder, Silicalite-1 zeolite, a pore-forming agent and a binder, carrying out extrusion forming on pug obtained by vacuum pugging, drying, and carrying out high-temperature roasting to obtain a tubular carrier;

(2) preparing a membrane casting solution by taking tetrapropylammonium bromide, silica sol, potassium fluoride and water as raw materials, wherein the molar ratio of the raw materials in the membrane casting solution is as follows: nSiO 2: nTPABr: nKF: nH2O = 1: 0.1-1: 0.05-1: 20-200 parts of;

(3) polishing the carrier prepared in the step (1), and placing the carrier and the membrane casting solution in a high-pressure reaction kettle together for in-situ hydrothermal treatment by a continuous flow method to obtain a tubular membrane material.

The innovation point of the invention is that the zeolite particles used as the membrane crystallization seed crystal, the aggregate for preparing the carrier and corresponding additives are mixed to prepare the special carrier with the function of inducing crystallization to form the membrane. Based on the innovation point, the invention selects the types of the aggregates, and the comparative experiments on various aggregates such as corundum, kaolin, mullite, alpha-alumina, gamma-alumina and the like show that the alpha-alumina and zeolite particles have better combination degree. The doped aggregate is prepared into a tubular carrier, and the Silicalite-1 zeolite membrane is prepared in situ hydrothermally in the tubular carrier. Compared with the secondary growth adopting seed crystal coating, the method omits the seed crystal coating step, is beneficial to an industrialized method, and compared with an in-situ growth method, the method provided by the invention has the zeolite particles on the carrier (and in the carrier), is beneficial to reducing the synthesis time of the zeolite membrane and can effectively control the crystallization process of the membrane, and by adopting the carrier and the synthesis method provided by the invention, the crystallization time of the Silicalite-1 zeolite membrane is preferably 24-48h, and the crystallization temperature is preferably 150-200 ℃.

Because the pore channels in the carrier contain a certain amount of zeolite particles, if the traditional static hydrothermal synthesis method is adopted, the casting solution is always immersed in the carrier in the crystallization process, and then zeolite is easily grown in the carrier, so that the internal channels of the carrier are blocked, and the flux of the membrane is reduced. Therefore, the continuous flow method is adopted for in-situ hydrothermal synthesis, namely two ends of the tubular carrier are connected with a synthetic solution storage tank through a circulating pump so as to lead the synthetic solution to be continuously introduced into and discharged from the carrier.

Preferably, the alpha-alumina powder is spherical powder, and the average particle diameter is 500-800 nm.

Preferably, the particle size of the Silicalite-1 zeolite is 300-500 nm. Preferably, the mass ratio of the alpha-alumina powder to the Silicalite-1 zeolite is 20: 1-5: 1. similarly, in order to ensure the bonding degree between the aggregate and the zeolite particles, the invention optimally selects the particle size and the content between the aggregate and the zeolite particles, and finds that the carrier prepared when the particle size of the alpha-alumina is 500-800nm and the particle size of the Silicalite-1 zeolite is 300-500nm has the best effect.

Preferably, the Silicalite-1 zeolite is prepared by a microwave hydrothermal method, and the template agent is removed by high-temperature roasting. And the Silicalite-1 zeolite particles prepared by the traditional hydrothermal synthesis method are generally larger than 1.5 μm, so the Silicalite-1 particles prepared by the microwave hydrothermal method are preferably adopted, compared with the common hydrothermal method, the particles prepared by the method have more uniform particle size and smaller particle size, and the particle size can be controlled to be 300-400nm through reasonable synthesis steps. The preferred zeolite particle synthetic fluid uses tetrapropylammonium bromide TPABr, fumed silica, sodium hydroxide and water as raw materials, wherein the molar ratio is 1SiO2: xTPABr: yN2O: zH2O, wherein x =0.1-1, y =0.05-0.3 and z = 30-100. The crystallization adopts a two-step crystallization method, the crystallization in the first step is carried out for 6-12h at 50-80 ℃, and then the crystallization is continued for 8-12h at the temperature of 100-150 ℃, the two-step crystallization is carried out under the stirring state, and the stirring speed is 100-300 rpm. It is noted that 500-. The particle size of the zeolite particles prepared by the microwave hydrothermal method is 300-500nm, which is beneficial to mixing with the aggregate. As the synthetic zeolite adopts the template agent, the template agent escapes from zeolite particles when the carrier is sintered at high temperature, and in tests, the carrier prepared by the zeolite without the template agent is found to be easy to generate fine cracks, but the zeolite after the template agent is removed by high-temperature roasting is combined with aggregate but almost has no cracks. However, during the high-temperature sintering stage of the carrier, the framework structure of the Silicalite-1 particles still collapses to be in a pit shape under SEM, but the zeolite membrane prepared by the method has relatively flat surface, and probably the collapse position is caused by thicker zeolite layer synthesized by particle induction, so that the membrane flux is relatively normal.

Preferably, the Silicalite-1 zeolite is obtained by ball milling zeolite synthesized by in-situ hydrothermal method, and then carrying out deposition screening. Besides microwave hydrothermal, the particle size of the hydrothermally synthesized Silicalite-1 particles (average particle size of 1.5 μm) can be shortened to the synthesized particle size range by mechanical crushing. The traditional mechanical crushing mode comprises a grinding mode, a ball milling mode and the like, the preferred mechanical crushing mode is wet ball milling, the ball milling time is 2-4h, the rotating speed is 100-500rpm, and the mass ratio of the particle solvent is 1: 10-1: 200, the solvent is preferably ethanol or water. The particles prepared by the method contain a large amount of amorphous substances which are not beneficial to combination with aggregate, and the amorphous substances can be removed by adopting a sedimentation mode, namely, the ball-milling suspension is placed in a container and stands for 4 to 5 hours, the sediment at the lower layer is dried for standby application, the horizontal surface area of the container is 0.01 to 1m2, and the height of the suspension is 10 to 50 cm. The zeolite particles prepared by the method have collapsed framework structures, so that no 'pits' appear after the carrier is sintered, and the collapsed zeolite particles still have the capability of inducing zeolite growth.

Preferably, the pore-forming agent is one or more of carbon powder, carbon black and polyvinyl alcohol; the binder is one or more of paraffin, dextrin and cellulose.

Detailed Description

In order to make the technical means, innovative features, objectives and effects of the present invention easy to understand, the present invention will be further described with reference to the following embodiments.

Comparative example 1

(1) The method is characterized in that Silicalite-1 zeolite is synthesized by a microwave method, tetrapropylammonium bromide TPABr, fumed silica, sodium hydroxide and water are used as raw materials in a synthetic solution, wherein the molar ratio of TPABr to fumed silica to sodium hydroxide to water is 1SiO2:0.2TPABr:0.15N2O:50H2O, a two-step crystallization method is adopted for crystallization, the first-step crystallization is performed for 12 hours at 60 ℃, then the crystallization is continued for 24 hours at 100 ℃, the two-step crystallization is performed in a stirring state, and the stirring speed is 200 rpm. After hydrothermal synthesis, centrifugally filtering the synthetic solution, washing with water and drying, and detecting the average particle size to be about 450 nm; and continuously roasting at the high temperature of 500 ℃ for 2h to remove the template agent.

(2) Mixing alpha-alumina spherical powder with the average particle size of 800nm and the Silicalite-1 zeolite prepared in the step (1) according to the mass ratio of 10: 1, adding a pore-forming agent carbon black and a binder paraffin, continuously and uniformly mixing, carrying out extrusion forming on pug obtained by vacuum pugging in a vacuum pug mill, drying, and roasting at high temperature to obtain a tubular carrier, wherein the roasting temperature is 1350 ℃.

(3) Preparing a membrane casting solution by taking tetrapropylammonium bromide, silica sol, potassium fluoride and water as raw materials, wherein the molar ratio of the raw materials in the membrane casting solution is as follows: nSiO 2: nTPABr: nKF: nH2O = 1: 0.6: 0.2: 50.

(4) polishing the carrier prepared in the step (2), wrapping the outer surface of the carrier by using a Teflon adhesive tape, and placing the carrier and the casting solution in a high-pressure reaction kettle together for in-situ hydrothermal treatment, wherein the synthesis temperature is 165 ℃, and the synthesis time is 48 hours.

(5) And after the synthesis is finished, naturally cooling the reaction kettle, taking out the tubular membrane material, washing, soaking and drying the tubular membrane material by using water, and roasting the tubular membrane material in a muffle furnace at the temperature of 500 ℃ for 4 hours to remove the template agent.

Comparative example 2

(1) Mixing self-made Silicalite-1 zeolite particles (prepared by a common hydrothermal method, the particle size is 1.7 mu m, the template agent is removed) and ethanol in a mass ratio of 1:100, adding the mixture into a ball milling container, setting the ball milling time for 3h, and setting the rotating speed to 300 rpm. And after the ball milling is finished, ball milling liquid is immediately poured into a cylindrical container with the surface area of 0.1 square meter to enable the ball milling liquid to naturally settle, after 4 hours, supernatant liquid is removed, and then the ball milling liquid is dried, wherein the particle size test shows that the ball milling liquid is 310 nm.

Example 1

(1) The method is characterized in that Silicalite-1 zeolite is synthesized by a microwave method, tetrapropylammonium bromide TPABr, fumed silica, sodium hydroxide and water are used as raw materials in a synthetic solution, wherein the molar ratio of TPABr to fumed silica to sodium hydroxide to water is 1SiO2:0.2TPABr:0.15N2O:50H2O, a two-step crystallization method is adopted for crystallization, the first-step crystallization is performed for 12 hours at 60 ℃, then the crystallization is continued for 24 hours at 100 ℃, the two-step crystallization is performed in a stirring state, and the stirring speed is 200 rpm. After hydrothermal synthesis, centrifugally filtering the synthetic solution, washing with water and drying, and detecting the average particle size to be 450 nm; and continuously roasting at the high temperature of 500 ℃ for 2h to remove the template agent.

(4) polishing the carrier prepared in the step (2), putting the carrier into a dynamic hydrothermal synthesis kettle, connecting two ends of the tubular carrier with a casting solution storage tank (with heat preservation and heating functions) through a pipeline, arranging a circulating pump on the pipeline, enabling the synthetic solution to continuously enter and exit the tubular carrier according to the modes of the casting solution storage tank, the circulating pump, the synthesis kettle and the casting solution storage tank, setting the synthesis temperature at 165 ℃ and the synthesis time at 48h, and preparing the tubular membrane material.

Example 2

Performance testing

The tubular membrane materials obtained in comparative examples 1-2 and examples 1-2 were subjected to pervaporation under test conditions: the operating temperature was 60 ℃, and the separation system was a 5wt.% ethanol/water solution. The results obtained are shown in table 1.

Table 1 results of pervaporation experiments on tubular membrane materials synthesized in examples 1-4

Sample (I)	Selectivity is	Flux (kg. h-1. m-2)
			Comparative example 1	150	1.04
Comparative example 2	141	1.11
			Example 1	145	1.56
Example 2	139	1.61

As can be seen from the table, the selectivity of the tubular membrane material for industrial alcohol-water separation provided by the invention is higher than 100, the flux is higher than 1.0 kg.h < -1 > m < -2 >, the tubular membrane material has high selectivity and permeation flux and better application value, and the membrane prepared by adopting the continuous flow method has small difference of selectivity compared with the membrane prepared by the static method, but the flux is greatly increased.

Other embodiments of the present invention than the preferred embodiments described above will be apparent to those skilled in the art from the present invention, and various changes and modifications can be made therein without departing from the spirit of the present invention as defined in the appended claims.

Claims

1. The preparation method of the alcohol permeable membrane material is characterized by comprising the following steps:

(2) preparing a membrane casting solution by taking tetrapropylammonium bromide, silica sol, potassium fluoride and water as raw materials, wherein the molar ratio of the raw materials in the membrane casting solution is as follows: nSiO₂：nTPABr：nKF：nH₂O=1：0.1-1： 0.05-1：20-200；

(3) Polishing the carrier prepared in the step (1), and placing the carrier and the membrane casting solution in a synthesis kettle for in-situ hydrothermal treatment by a continuous flow method to obtain an alcohol permeable membrane material; the particle size of the Silicalite-1 zeolite is 300-500 nm; the Silicalite-1 zeolite is obtained by ball milling zeolite which is synthesized by in-situ hydrothermal method, and then depositing and screening; the continuous flow method is characterized in that two ends of a tubular carrier are connected with a casting solution storage tank through pipelines, and a circulating pump is arranged on the pipelines, so that a synthetic solution can continuously enter and exit the tubular carrier according to the modes of the casting solution storage tank-the circulating pump-the synthetic kettle-the casting solution storage tank; the ball milling is wet ball milling, the ball milling time is 2-4h, the rotating speed is 100-500rpm, and the mass ratio of the Silicalite-1 zeolite particles to the solvent is 1: 10-1: 200, and the solvent is ethanol or water.

2. The method as set forth in claim 1, wherein the α -alumina powder is spherical and has an average particle size of 500-800 nm.

3. The method according to claim 1, wherein the mass ratio of the alpha-alumina powder to the Silicalite-1 zeolite is 20: 1-5: 1.

4. the method according to claim 1, wherein the pore-forming agent is one or more of carbon powder, carbon black and polyvinyl alcohol; the binder is one or more of paraffin, dextrin and cellulose.