CN113522037A - Preparation method of pervaporation tetrahydrofuran dehydration composite membrane - Google Patents

Abstract

The invention relates to a preparation method of a pervaporation tetrahydrofuran dehydration composite membrane, belonging to the technical field of pervaporation membrane separation. In the composite membrane material, polyvinyl alcohol and polyaniline synthesized under the acidic condition of specific composite acid have excellent hydrophilicity, water is a protic solvent, tetrahydrofuran is an aprotic solvent, so that tetrahydrofuran and water can be separated, the crosslinking agent maleic anhydride provided by the invention mainly has the function of realizing crosslinking of polymer macromolecules by taking a crosslinking agent as a bridge group, mainly realizes crosslinking of c-c bonds to form body-type molecules, and enables the body-type molecules to be cured, the polyvinyl alcohol has high hydrophilicity and can form hydrogen bonds with water, and after polyaniline is modified, the hydrophilicity of the polyvinyl alcohol is greatly enhanced, and the heat stability of the polyvinyl alcohol can be improved, so that the polyaniline is more resistant to high temperature.

Description

Preparation method of pervaporation tetrahydrofuran dehydration composite membrane

Technical Field

The invention relates to a preparation method of a pervaporation tetrahydrofuran dehydration composite membrane, belonging to the technical field of pervaporation membrane separation.

Background

Tetrahydrofuran is currently a common solvent in organic synthesis and is used as a solvent in pharmaceutical manufacturing, synthesis of polymeric materials, fabrication of precision magnetic tapes and electroplating industries.

Most processes for the production of tetrahydrofuran produce water and therefore, in order to increase the purity of the tetrahydrofuran product, water must be removed. However, tetrahydrofuran forms a minimum azeotrope with water at an azeotropic temperature of 64 ℃ with an azeotropic composition containing about 94.1% by mass of tetrahydrofuran, i.e., tetrahydrofuran products of greater than this purity are not obtained by conventional rectification methods.

A method for separating a tetrahydrofuran-water mixture, which is commonly used in industry, includes: adsorption, pervaporation, azeotropic distillation, pressure swing distillation, extractive distillation, and the like. Adsorption processes can be divided into two categories, including chemisorption and physisorption, which are based on differences in the nature of the binding forces between the adsorbate and the adsorbent molecule. Wherein the physical adsorption is reversible and is widely applied in the field of separation process. Adsorbents commonly used in the adsorption process can be classified into four major categories, namely activated carbon, molecular sieves, activated alumina and silica gel. Suitable adsorbents have a high selectivity, however, after a certain period of use the adsorption capacity decreases, regeneration is required and the assembly is complicated.

Pervaporation is a novel membrane separation technology which takes partial pressure difference of components on two sides of a membrane as driving force and realizes separation of liquid mixtures based on different dissolution and diffusion rates of each osmotic component in the membrane. Compared with the traditional separation process, the method has the advantages of high efficiency, low energy consumption, simple process, convenient operation, easy coupling with other processes, no external separating agent, no pollution, no limitation of vapor-liquid phase balance and the like. However, the main parts of the membrane are difficult to manufacture, the manufacturing cost is high, and the surface is easy to scale.

In view of the above-mentioned drawbacks, the present inventors have made active research and innovation to create a method for preparing a pervaporation tetrahydrofuran dehydration composite membrane, which has industrial value.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide a preparation method of a pervaporation tetrahydrofuran dehydration composite membrane.

The preparation method of the pervaporation tetrahydrofuran dehydration composite membrane comprises the following steps:

(1) adding a certain amount of aniline into a certain amount of deionized water, continuously stirring, adding sulfuric acid and sulfosalicylic acid composite acid, reacting aniline with the composite acid to generate soluble sulfate, slowly dropwise adding an ammonium persulfate solution into the generated sulfate solution under the condition of continuously stirring, controlling the reaction temperature to perform polymerization reaction, after the reaction is finished, performing suction filtration by using a funnel, washing and filtering by using the composite acid, absolute ethyl alcohol and distilled water in sequence until the filtrate is colorless, then drying for 24 hours at constant temperature of 60 ℃ in a vacuum drying oven, and grinding to obtain polyaniline solid powder;

(2) dissolving a certain amount of polyvinyl alcohol in deionized water to prepare a polyvinyl alcohol solution, keeping a certain temperature and stabilizing for several hours, cooling to normal temperature, and then filling into a bottle for later use;

(3) adding polyaniline powder into a polyvinyl alcohol solution, adding certain maleic anhydride as a cross-linking agent, taking sulfuric acid as a catalyst, uniformly stirring, and then performing ultrasonic dispersion for 6 hours by adopting an ultrasonic dispersion method, controlling the temperature during ultrasonic treatment by using an ice bath method, so as to finally obtain a uniformly dispersed casting solution;

(4) and casting the prepared membrane liquid on a clean glass plate prepared in advance to form a membrane by scraping, and performing heat treatment to obtain the composite membrane to be prepared.

Further, the adding amount of the aniline in the step (1) is 10-15% of the mass of the deionized water.

Further, the molar concentration ratio of the sulfuric acid to the sulfosalicylic acid in the composite acid in the step (1) is 1: 4.

Further, the mass ratio of the amount of the ammonium persulfate added in the step (1) to the aniline is 1.5:1, and the dropping speed of the ammonium persulfate solution is 5 mL/min.

Further, after the ammonium persulfate is added in the step (1), the color of the solution gradually changes from light yellow to green, the color of the solution gradually deepens with the continuous reaction and finally changes into emerald green, and the reaction temperature is controlled to be 20 ℃ for polymerization for 6 hours.

Further, in the step (2), the mass fraction of the polyvinyl alcohol solution is 5% -10%, and the polyvinyl alcohol solution is kept stable at the temperature of 75-95 ℃ for 3-4 h.

Further, in the step (3), the polyaniline is added in an amount which is 1-5% of the mass of the polyvinyl alcohol solution, maleic anhydride which is 5% of the mass of the polyvinyl alcohol solution is added as a cross-linking agent, and sulfuric acid which is 2% of the mass of the polyvinyl alcohol solution is added as a catalyst.

Further, the temperature of the drying oven in the step (4) is 100-115 ℃, and the drying time is 24 hours.

By the scheme, the invention at least has the following advantages:

the pervaporation tetrahydrofuran dehydration composite membrane prepared by the invention has the advantages of simple preparation process and convenience in operation. The prepared pervaporation tetrahydrofuran dehydration composite membrane has a compact separation layer on the outer surface, has good selectivity on tetrahydrofuran/water, high separation factor and considerable flux, and can be used for separating tetrahydrofuran/water fermentation liquor. In the composite membrane material, polyvinyl alcohol and polyaniline synthesized under the acidic condition of specific composite acid have excellent hydrophilicity, water is a protic solvent, tetrahydrofuran is an aprotic solvent, so that tetrahydrofuran and water can be separated, the crosslinking agent maleic anhydride provided by the invention mainly has the function of realizing crosslinking of polymer macromolecules by taking a crosslinking agent as a bridge group, mainly realizes crosslinking of c-c bonds to form body-type molecules, and enables the body-type molecules to be cured, the polyvinyl alcohol has high hydrophilicity and can form hydrogen bonds with water, and after polyaniline is modified, the hydrophilicity of the polyvinyl alcohol is greatly enhanced, and the heat stability of the polyvinyl alcohol can be improved, so that the polyaniline is more resistant to high temperature.

The foregoing is a summary of the present invention, and in order to provide a clear understanding of the technical means of the present invention and to be implemented in accordance with the present specification, the following is a detailed description of the preferred embodiments of the present invention.

Detailed Description

The following examples are given to further illustrate the embodiments of the present invention. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Adding deionized water into a reaction kettle, adding aniline with the mass of 10-15% of the deionized water into the reaction kettle, continuously stirring, mixing sulfuric acid and sulfosalicylic acid according to the molar ratio of 1:4 to obtain mixed acid, adding excessive mixed acid into the reaction kettle, reacting aniline and acid to generate soluble sulfate, dropwise adding an ammonium persulfate solution with the mass of 1.5 times of that of aniline into the generated sulfate solution at the speed of 5mL/min under the condition of continuously stirring, gradually changing the solution color from light yellow to green after adding ammonium persulfate, gradually deepening the solution color along with the continuous reaction to finally change into emerald green, controlling the reaction temperature to polymerize at 20 ℃ for 6h, after the reaction is finished, performing suction filtration by using a funnel, sequentially washing and filtering by using composite acid, absolute ethyl alcohol and distilled water until the filtrate is basically colorless, and then drying at the constant temperature of 60 ℃ for 24h in a vacuum drying oven, grinding to obtain polyaniline solid powder;

adding deionized water into a beaker, adding polyvinyl alcohol with the mass of 5-10% of that of the deionized water into the beaker, dissolving to prepare polyvinyl alcohol solution, keeping the temperature at 75-95 ℃ for 3-4 hours, cooling to normal temperature, and filling into a bottle for later use;

adding polyaniline powder accounting for 1-5% of the mass of the polyvinyl alcohol solution into the polyvinyl alcohol solution, adding maleic anhydride accounting for 5% of the mass of the polyvinyl alcohol solution as a cross-linking agent, adding sulfuric acid accounting for 2% of the mass of the polyvinyl alcohol solution as a catalyst, uniformly stirring, performing ultrasonic dispersion, controlling the temperature during ultrasonic dispersion by using an ice bath method, and performing ultrasonic dispersion for 6 hours to finally obtain a uniformly dispersed casting solution;

casting the prepared membrane liquid on a clean glass plate prepared in advance to be scraped into a membrane, putting the membrane liquid into a drying box with the temperature of 100-115 ℃, and drying for 24 hours to prepare the pervaporation tetrahydrofuran dehydration composite membrane.

Examples

Example 1

(1) Deionized water is added into a reaction kettle, aniline with the mass of 10 percent of that of the deionized water is added into the reaction kettle, the mixture is continuously stirred, sulfuric acid and sulfosalicylic acid are mixed according to the molar ratio of 1:4 to obtain mixed acid, excessive mixed acid is added into the reaction kettle, the aniline and the acid react to generate soluble sulfate, slowly dripping ammonium persulfate solution with the mass of 1.5 times of that of aniline into the generated sulfate solution under the condition of continuously stirring, adding ammonium persulfate, gradually changing the color of the solution from light yellow to green, gradually deepening the color of the solution along with the continuous reaction, finally changing the color of the solution into emerald green, controlling the reaction temperature to be 20 ℃ for polymerization for 6 hours, after the reaction is finished, performing suction filtration by using a funnel, washing and filtering with composite acid, absolute ethyl alcohol and distilled water in sequence until the filtrate is colorless, then drying the polyaniline in a vacuum drying oven for 24 hours at the constant temperature of 60 ℃, and grinding to obtain polyaniline solid powder;

(2) adding deionized water into a beaker, adding polyvinyl alcohol with the mass of 5% of that of the deionized water into the beaker, dissolving to prepare polyvinyl alcohol solution, keeping the temperature at 75 ℃ for 3 hours, cooling to normal temperature, and filling into a bottle for later use;

(3) adding polyaniline powder accounting for 1 percent of the mass of the polyvinyl alcohol solution into the polyvinyl alcohol solution, adding maleic anhydride accounting for 5 percent of the mass of the polyvinyl alcohol solution as a cross-linking agent, adding sulfuric acid accounting for 2 percent of the mass of the polyvinyl alcohol solution as a catalyst, uniformly stirring, performing ultrasonic dispersion, controlling the temperature during ultrasonic dispersion by an ice bath method, and performing ultrasonic dispersion for 6 hours to finally obtain a uniformly dispersed casting solution;

(4) and casting the prepared membrane liquid on a clean glass plate prepared in advance to scrape the membrane liquid into a membrane, putting the membrane liquid into a drying oven at the temperature of 100 ℃, and drying the membrane liquid for 24 hours to prepare the pervaporation tetrahydrofuran dehydration composite membrane.

Example 2

(1) Deionized water is added into a reaction kettle, aniline with the mass of 13 percent of that of the deionized water is added into the reaction kettle, the mixture is continuously stirred, sulfuric acid and sulfosalicylic acid are mixed according to the molar ratio of 1:4 to obtain mixed acid, excessive mixed acid is added into the reaction kettle, the aniline and the acid react to generate soluble sulfate, slowly dripping ammonium persulfate solution with the mass of 1.5 times of that of aniline into the generated sulfate solution under the condition of continuously stirring, adding ammonium persulfate, gradually changing the color of the solution from light yellow to green, gradually deepening the color of the solution along with the continuous reaction, finally changing the color of the solution into emerald green, controlling the reaction temperature to be 20 ℃ for polymerization for 6 hours, after the reaction is finished, performing suction filtration by using a funnel, washing and filtering with composite acid, absolute ethyl alcohol and distilled water in sequence until the filtrate is colorless, then drying the polyaniline in a vacuum drying oven for 24 hours at the constant temperature of 60 ℃, and grinding to obtain polyaniline solid powder;

(2) adding deionized water into a beaker, adding polyvinyl alcohol with the mass of 8% of that of the deionized water into the beaker, dissolving to prepare polyvinyl alcohol solution, keeping the temperature at 85 ℃ and stabilizing for 3 hours, cooling to normal temperature, and then filling into a bottle for later use;

(3) adding polyaniline powder accounting for 3% of the mass of the polyvinyl alcohol solution into the polyvinyl alcohol solution, adding maleic anhydride accounting for 5% of the mass of the polyvinyl alcohol solution as a cross-linking agent, adding sulfuric acid accounting for 2% of the mass of the polyvinyl alcohol solution as a catalyst, uniformly stirring, performing ultrasonic dispersion, controlling the temperature during ultrasonic dispersion by an ice bath method, and performing ultrasonic dispersion for 6 hours to finally obtain a uniformly dispersed casting solution;

(4) and casting the prepared membrane liquid on a clean glass plate prepared in advance to be scraped into a membrane, putting the membrane liquid into a drying box with the temperature of 108 ℃, and drying for 24 hours to obtain the pervaporation tetrahydrofuran dehydration composite membrane.

Example 3

(1) Deionized water is added into a reaction kettle, aniline with the mass of 15 percent of that of the deionized water is added into the reaction kettle, the mixture is continuously stirred, sulfuric acid and sulfosalicylic acid are mixed according to the molar ratio of 1:4 to obtain mixed acid, excessive mixed acid is added into the reaction kettle, the aniline and the acid react to generate soluble sulfate, slowly dripping ammonium persulfate solution with the mass of 1.5 times of that of aniline into the generated sulfate solution under the condition of continuously stirring, adding ammonium persulfate, gradually changing the color of the solution from light yellow to green, gradually deepening the color of the solution along with the continuous reaction, finally changing the color of the solution into emerald green, controlling the reaction temperature to be 20 ℃ for polymerization for 6 hours, after the reaction is finished, performing suction filtration by using a funnel, washing and filtering with composite acid, absolute ethyl alcohol and distilled water in sequence until the filtrate is colorless, then drying the polyaniline in a vacuum drying oven for 24 hours at the constant temperature of 60 ℃, and grinding to obtain polyaniline solid powder;

(2) adding deionized water into a beaker, adding polyvinyl alcohol with the mass of 10% of that of the deionized water into the beaker, dissolving to prepare polyvinyl alcohol solution, keeping the temperature at 95 ℃ for 4 hours, cooling to normal temperature, and then filling into a bottle for later use;

(3) adding polyaniline powder accounting for 5% of the mass of the polyvinyl alcohol solution into the polyvinyl alcohol solution, adding maleic anhydride accounting for 5% of the mass of the polyvinyl alcohol solution as a cross-linking agent, adding sulfuric acid accounting for 2% of the mass of the polyvinyl alcohol solution as a catalyst, uniformly stirring, performing ultrasonic dispersion, controlling the temperature during ultrasonic dispersion by an ice bath method, and performing ultrasonic dispersion for 6 hours to finally obtain a uniformly dispersed casting solution;

(4) and casting the prepared membrane liquid on a clean glass plate prepared in advance to be scraped into a membrane, putting the membrane liquid into a drying box with the temperature of 115 ℃, and drying for 24 hours to prepare the pervaporation tetrahydrofuran dehydration composite membrane.

Comparative example 1

The preparation method is basically the same as that of example 1 of the present invention, except that a mixed acid prepared by using hydrochloric acid instead of sulfuric acid and sulfosalicylic acid used in the present invention;

comparative example 2

The molecular sieve vaporization permeable membrane is used for replacing the pervaporation tetrahydrofuran dehydration composite membrane of the invention;

comparative example 3

The polyaniline ultrafiltration membrane is used for replacing the pervaporation tetrahydrofuran dehydration composite membrane;

the performance of examples 1 to 3 of the present invention and comparative examples 1 to 3 were measured, respectively, and the results are shown in table 1:

the detection method comprises the following steps:

heating tetrahydrofuran solution with water content of 5%, dehydrating by a pervaporation membrane device, controlling the temperature to be 55 ℃, and calculating the final permeation flux:

permeate flux (J, g/m)²H) determined by measuring the permeate mass at steady state of the permeation process:

J＝W/(A*t)

wherein: w is total mass of permeate, kg; a is the membrane area, m²(ii) a t is the time h.

TABLE 1 Performance test results

Firstly, the detection data in examples 1-3 of the invention are compared, and it can be seen that the detection data in example 3 is optimal, because the material dosage and the reaction condition in example 3 are optimal, which also laterally proves that the technical scheme of the invention can be implemented;

comparing the experimental data of comparative example 1 with the performance of example 1 of the present invention, the comparative example 1 has substantially the same performance as example 1 of the present invention except that the mixed acid prepared by using hydrochloric acid instead of sulfuric acid and sulfosalicylic acid used in the present invention has poor permeability and dehydration properties of the finally prepared composite membrane, so that it can be confirmed that the synthesized polyaniline has better hydrophilicity, water is a protic solvent, and tetrahydrofuran is an aprotic solvent, so that tetrahydrofuran and water can be more completely separated;

the experimental data of comparative example 2 were compared with those of example 1 of the present invention in terms of performance, and comparative example 2 was a molecular sieve vapor permeation membrane instead of the pervaporation tetrahydrofuran dehydration composite membrane of the present invention. The dehydration performance of tetrahydrofuran is obviously reduced finally, so that the composite membrane has better separation effect compared with zeolite molecular sieve;

the experimental data of comparative example 3 and example 3 of the present invention were compared in terms of performance, and comparative example 3 used a polyaniline ultrafiltration membrane in place of the pervaporation tetrahydrofuran dehydration composite membrane of the present invention; the dehydration performance of tetrahydrofuran is obviously reduced finally, so that the composite membrane has a better separation effect compared with a polyaniline ultrafiltration membrane.

The prepared pervaporation tetrahydrofuran dehydration composite membrane has a compact separation layer on the outer surface, has good selectivity on tetrahydrofuran/water, high separation factor and considerable flux, and can be used for separating tetrahydrofuran/water fermentation liquor. In the composite membrane material, polyvinyl alcohol and polyaniline synthesized under the acidic condition of specific composite acid have excellent hydrophilicity, water is a protic solvent, tetrahydrofuran is an aprotic solvent, so that tetrahydrofuran and water can be separated, the crosslinking agent maleic anhydride provided by the invention mainly has the function of realizing crosslinking of polymer macromolecules by taking a crosslinking agent as a bridge group, mainly realizes crosslinking of c-c bonds to form body-type molecules, and enables the body-type molecules to be cured, the polyvinyl alcohol has high hydrophilicity and can form hydrogen bonds with water, and after polyaniline is modified, the hydrophilicity of the polyvinyl alcohol is greatly enhanced, and the heat stability of the polyvinyl alcohol can be improved, so that the polyaniline is more resistant to high temperature. The normal working temperature of the permeable membrane before modification by polyaniline is about 25-110 ℃, and the working temperature-resistant range of the modified composite membrane is about 25-160 ℃.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (8)

1. A preparation method of a pervaporation tetrahydrofuran dehydration composite membrane is characterized by comprising the following steps:

(1) adding a certain amount of aniline into a certain amount of deionized water, continuously stirring, adding sulfuric acid and sulfosalicylic acid composite acid, reacting aniline with the composite acid to generate soluble sulfate, slowly dropwise adding an ammonium persulfate solution into the generated sulfate solution under the condition of continuously stirring, controlling the reaction temperature to perform polymerization reaction, after the reaction is finished, performing suction filtration by using a funnel, washing and filtering by using the composite acid, absolute ethyl alcohol and distilled water in sequence until the filtrate is colorless, then drying for 24 hours at constant temperature of 60 ℃ in a vacuum drying oven, and grinding to obtain polyaniline solid powder;

(2) dissolving a certain amount of polyvinyl alcohol in deionized water to prepare a polyvinyl alcohol solution, keeping a certain temperature and stabilizing for several hours, cooling to normal temperature, and then filling into a bottle for later use;

(3) adding polyaniline powder into a polyvinyl alcohol solution, adding certain maleic anhydride as a cross-linking agent, taking sulfuric acid as a catalyst, uniformly stirring, and then performing ultrasonic dispersion for 6 hours by adopting an ultrasonic dispersion method, controlling the temperature during ultrasonic treatment by using an ice bath method, so as to finally obtain a uniformly dispersed casting solution;

(4) and casting the prepared membrane liquid on a clean glass plate prepared in advance to form a membrane by scraping, and performing heat treatment to obtain the composite membrane to be prepared.

2. The method for preparing the pervaporation tetrahydrofuran dehydration composite membrane according to claim 1, wherein the amount of aniline added in the step (1) is 10-15% of the mass of deionized water.

3. The method for preparing the pervaporation tetrahydrofuran dehydration composite membrane according to claim 1, wherein the molar concentration ratio of the sulfuric acid to the sulfosalicylic acid in the composite acid in the step (1) is 1: 4.

4. The method for preparing the pervaporation tetrahydrofuran dehydration composite membrane according to claim 1, wherein the mass ratio of the amount of the ammonium persulfate to the aniline added in the step (1) is 1.5:1, and the dropping speed of the ammonium persulfate solution is 5 mL/min.

5. The preparation method of the pervaporation tetrahydrofuran dehydration composite membrane according to claim 1, wherein after the ammonium persulfate is added in the step (1), the color of the solution gradually changes from light yellow to green, and finally changes to emerald green as the color of the solution gradually deepens with the continuous progress of the reaction, and the polymerization is carried out for 6 hours at the reaction temperature of 20 ℃.

6. The preparation method of the pervaporation tetrahydrofuran dehydration composite membrane according to claim 1, wherein in the step (2), the mass fraction of the polyvinyl alcohol solution is 5% -10%, and the polyvinyl alcohol solution is kept stable at a temperature of 75-95 ℃ for 3-4 h.

7. The method according to claim 1, wherein polyaniline is added in an amount of 1-5% by mass of the polyvinyl alcohol solution in step (3), maleic anhydride is added in an amount of 5% by mass of the polyvinyl alcohol solution as a crosslinking agent, and sulfuric acid is added in an amount of 2% by mass of the polyvinyl alcohol solution as a catalyst.

8. The method for preparing the pervaporation tetrahydrofuran dehydration composite membrane according to claim 1, wherein the temperature of the drying oven in the step (4) is 100 ℃ to 115 ℃, and the drying time is 24 hours.