CN103724649A - Method for preparing alkaline anion-exchange membrane through plasma grafting - Google Patents

Abstract

The invention discloses a method for preparing a basic anion exchange membrane by plasma grafting. The polymer powder is used as a matrix, and the anion exchange group is directly introduced into the polymer powder through plasma bombardment and monomer graft polymerization. group to prepare a basic anion exchange membrane with uniform distribution of functional groups. The method of the invention has simple process and convenient operation; vinyl benzyl ammonium chloride is used as a reaction monomer, does not pollute the atmosphere, improves the working environment of operators, and has lower requirements on devices. The grafting monomer used in the method of the invention can be dissolved in water, can reduce the use of organic solvents, and meanwhile, does not produce chlorobenzylethylene waste liquid and organic amine waste liquid, and does not pollute the environment. The prepared alkaline anion exchange membrane has good thermal stability, chemical stability, electron exchange capacity, ion conductivity and low ethanol permeability, and is suitable for polymer electrolyte fuel cells, especially for alkaline direct Alcohol fuel cells.

Description

A method for preparing alkaline anion exchange membrane by plasma grafting

technical field

The invention relates to a preparation method of an anion exchange membrane, in particular to a method for preparing an alkaline anion exchange membrane by plasma grafting.

Background technique

Polymer electrolyte fuel cells represented by proton exchange membrane fuel cells have the characteristics of cleanness, high efficiency, and low-temperature operation. They are fuel cells with great development potential and application value. However, the acidic environment in which fuel cells work requires a price Precious metals such as platinum, which are expensive and scarce in resources, are used as catalysts, which greatly increase the cost of batteries [R. Borup, et al., Chem. Rev. 107 (2007) 3904]. In order to solve this problem, the alkaline anion exchange membrane fuel cell developed uses the alkaline anion exchange membrane as the electrolyte, conducts hydroxide ions (OH ^– ), and the working environment is alkaline, without using precious metals such as platinum as catalysts, and is not easy CO poisoning of the catalyst occurs, because the conduction direction of OH ^– is opposite to the permeation direction of the fuel, the battery fuel permeation phenomenon is not serious [C. Coutanceau, et al., J. Power Sources 156 (2006) 14; JR Varcoe, et al ., Fuel Cells 5 (2005) 187; K. Kordesch, et al., J. Hydrogen Energ. 13 (1988) 411]. The core of the alkaline direct alcohol fuel cell is the alkaline anion exchange membrane (AAEM), which plays a triple role of conducting OH ^– , isolating electrons, and preventing fuel and oxidant from passing through. Its performance will largely affect the fuel cell performance.

At present, the preparation methods of basic anion membrane mainly include chloromethylation method and radiation grafting method. The chloromethylation method uses the chloromethylation reaction to introduce chloromethyl groups on the polymer skeleton structure, and then obtains anion exchange groups through quaternization and alkalization. The chloromethylation reaction often requires the use of highly toxic carcinogens Chloromethyl ether [T. Xu, et al., J. Membr. Sci. 249 (2005) 183]. The radiation grafting method can avoid the use of chloromethyl ether by grafting functional monomers on the polymer film, and then obtaining anion exchange groups through quaternization and alkalization. However, high radiation energy can easily cause structural damage to the polymer matrix, so the radiation grafting method is only suitable for perfluoropolymer matrix [TN Danks, et al., J. Mater. Chem. 13 (2003) 712]. At the same time, since the radiation energy decreases with the increase of the penetration depth, it is difficult for the functional groups to form a uniform longitudinal distribution, which affects the transmission of ^OH- ions.

Using polymer powder as the matrix, generating free radicals on the surface of the polymer powder by plasma bombardment, and then grafting the free radicals with chloromethylstyrene monomer in liquid phase to introduce functional groups on the polymer matrix The preparation of anion exchange membrane is conducive to the uniform distribution of functional groups in the membrane, and the plasma bombardment is relatively mild and does not damage the polymer matrix [J. Hu, J. Power Source 196 (2011) 4483]. However, since the chloromethylstyrene and organic amine raw materials used in the grafting method are volatile and irritating, the requirements for the sealing of the reaction device and operational safety are high; A large amount of chloromethylstyrene waste liquid and organic amine waste liquid will also be produced in the process, which needs further treatment in the later stage and causes waste of raw materials.

Contents of the invention

In order to overcome the deficiencies of the prior art, the invention discloses a preparation method of a basic anion exchange membrane. The benzyl ammonium chloride functional group (ion exchange group) is directly introduced on the surface of the polymer powder by plasma grafting, and the basic anion exchange membrane is obtained by soaking in the alkaline solution after the film is formed. The preparation of the present invention The method has simple process, does not produce waste liquid, and is environmentally friendly.

The technical scheme that the present invention adopts for realizing the above object is as follows:

A method for preparing alkaline anion exchange membranes by plasma grafting, characterized in that it comprises the following steps:

(1) Place the polymer powder in the plasma discharge area and stir the polymer powder continuously; turn on the power to generate plasma discharge, the discharge power is 50-250 W, and the plasma discharge treatment is 10-60 min;

(2) Put the powder after plasma activation in step (1) into the aqueous solution of vinyl benzyl ammonium chloride, raise the temperature to 40-60°C, and stir for 8-72 h to make vinyl benzyl ammonium chloride The polymer is grafted and polymerized on the powder, and anion exchange groups are introduced on the surface of the polymer powder;

(3) Centrifuge and filter the mixture obtained after the reaction in step (2), then wash and dry with deionized water, dissolve the dried powder in a solvent, and then coat and cast to form a film to obtain an anion exchange membrane;

(4) Immerse the prepared anion exchange membrane in 1-2 mol/L alkali solution for 10-60 h, then take out the membrane, wash and soak it with deionized water to prepare an alkaline anion exchange membrane.

The polymer powder is selected from one or more mixtures of polyethersulfone, polyarylsulfone, polyetherketone, polyetheretherketone, polyphenylene sulfide, polyvinyl chloride, polyethylene, polyimide , the particle size of the polymer powder should not be greater than 200 μm.

The plasma source is selected from one of argon plasma source, nitrogen plasma source, oxygen plasma source, helium plasma source, hydrogen plasma source, water gas plasma source, air plasma source or Various mixes.

The plasma is selected from one of low-pressure low-temperature plasma, high-pressure low-temperature plasma and atmospheric-pressure low-temperature plasma.

The concentration of the vinyl benzyl ammonium chloride aqueous solution is 10-80 wt%.

The solvent described in step (3) is selected from one or more of tetrahydrofuran, toluene, xylene, sulfolane, dimethylformamide, dimethyl sulfoxide, tetramethylene sulfoxide, and methylpyrrolidone kind of mix.

The method of the present invention uses polymer powder as a matrix, adopts plasma activation to generate active particles on the surface of the polymer powder, and then grafts and polymerizes the active particles and vinyl benzyl ammonium chloride monomer onto the polymer powder to directly introduce benzyl ammonium chloride functional group (anion exchange group).

The advantage of the present invention compared with prior art is:

1. The method of the present invention is simplified, and the process operation is convenient: the method of the present invention adopts three steps of plasma activation-graft polymerization-film formation to prepare anion exchange membrane, the reaction efficiency is high and the process steps are simplified;

2. The raw materials of the method of the present invention are environmentally friendly and do not pollute the environment: the method of the present invention uses vinyl benzyl ammonium chloride with no volatile irritation and low toxicity as the reaction monomer, which reduces air pollution and improves the working environment of operators , and lower requirements on the device, easy to operate.

3. The method of the present invention does not produce waste liquid that pollutes the environment: the grafted monomers used in the method of the present invention can be dissolved in water, which can reduce the use of organic solvents. At the same time, compared with the original technology, no waste liquid of chlorobenzylethylene is produced , organic amine waste liquid, does not pollute the environment; and does not use highly toxic and carcinogenic chloromethyl ether, clean and non-toxic;

4. The method of the present invention uses the polymer powder as the matrix, which has a larger surface area than the polymer film and increases the grafting active sites;

5. After the graft polymer solution is stirred evenly, the film is cast, which is conducive to the uniform distribution of ion exchange groups in the film;

6. The plasma bombardment is relatively mild and does not damage the polymer matrix.

In a word, the basic anion exchange membrane prepared by the method of the present invention not only has good thermal stability and chemical stability, but also has a low ethanol permeability (10 ^-11 ~ 10 ^-13 m ² /s order of magnitude) And high ion conductivity (10 ^-3 ~10 ^-2 S/cm order), the process is simple, environmentally friendly, and does not produce toxic waste gas. The prepared alkaline anion exchange membrane has good thermal stability, chemical stability, electron exchange capacity, ion conductivity and low ethanol permeability, and is suitable for polymer electrolyte fuel cells, especially for alkaline direct Alcohol fuel cells.

Description of drawings

Fig. 1 is the mass change figure that the alkaline anion exchange membrane that embodiment 1 makes is as temperature increases under nitrogen atmosphere;

Fig. 2 is the basic anion exchange membrane infrared spectrum data figure that embodiment 1 makes;

Fig. 3 Example 3 The corresponding relationship between mass change and time in polyarylsulfone-based plasma-grafted basic anion-exchange membrane immersed in 3 wt% H ₂ O ₂ .

Detailed ways

Example 1:

Weigh 10 g of polyether ketone powder and place it in the plasma reactor, turn on the magnetic stirrer and stir continuously, use helium as the discharge gas to generate jet plasma discharge under atmospheric pressure, discharge power is 250 W, and discharge for 30 min; then Add the plasma-activated powder into 20 ml of vinyl benzyl ammonium chloride aqueous solution, the mass percentage concentration of vinyl benzyl ammonium chloride is 50%, stir at 60°C for 8 h, centrifuge, filter, and deionized water Washing to remove residual monomers on the surface of the polymer, and drying; dissolving the dried powder in N,N-dimethylformamide to form a solution with a concentration of 10% by mass, and then salivating to form a film. Dry the membrane to prepare an anion exchange membrane; finally, immerse the membrane in 1 mol/L NaOH aqueous solution for 48 h, take it out and wash it with deionized water to prepare an alkaline anion exchange membrane. Fig. 1 is the mass change diagram of basic anion exchange membrane along with temperature rising under nitrogen atmosphere, shows by Fig. 1, the inventive method can effectively graft functional group on polymer raw material, and the prepared by the inventive method The basic anion exchange membrane has good thermal stability, and the membrane can be used stably below 120°C. Fig. 2 is the infrared spectrum data diagram of the basic anion exchange membrane prepared by the method of the present invention, as can be seen from Fig. 2, the basic anion exchange membrane prepared by the method of the present invention is rich in quaternary ammonium groups with anion exchange capacity. The alkaline anion exchange membrane has a high ion conductivity (10 ^-2 S/cm order) measured by electrochemical impedance spectroscopy, and the alkaline anion exchange membrane has a low ethanol permeability ( 10 ^-12 m ² /s order)

Example 2:

Weigh 5 g of polyvinyl chloride powder and place it in the plasma reactor, turn on the magnetic stirrer and stir continuously, evacuate to the background, use argon as the discharge gas, and generate capacitive coupling at 20 Pa and 50 W discharge power. Plasma discharge, discharge for 60 min; then add the plasma-activated powder into 20 ml of vinyl benzyl ammonium chloride aqueous solution, the concentration of vinyl benzyl ammonium chloride is 10% by mass, and stir at 60°C for 72 h , centrifuged, filtered, washed with deionized water to remove residual monomers on the surface of the polymer, and dried; the dried powder was dissolved in tetrahydrofuran to make a solution with a concentration of 5% by mass, and then salivated to form a film , drying the membrane to prepare an anion exchange membrane; finally, immerse the membrane in 2 mol/L NaOH aqueous solution for 12 h, take it out and wash it with deionized water to prepare an alkaline anion exchange membrane. The alkaline anion exchange membrane has a high ion conductivity (10 ^-3 S/cm order) measured by electrochemical impedance spectroscopy, and the alkaline anion exchange membrane has a low ethanol permeability ( 10 ^-11 m ² /s order).

Example 3:

Weigh 2 g of polyarylsulfone powder and place it in the plasma reactor, turn on the magnetic stirrer and stir continuously, vacuumize to the background, use nitrogen as the discharge gas, and generate inductively coupled plasma discharge at 100 Pa, and the discharge power is 200 W, discharge for 10 min; then add the plasma-activated powder into 10 ml of vinyl benzyl ammonium chloride aqueous solution, the mass percentage concentration of vinyl benzyl ammonium chloride is 80%, and stir at 40 °C for 24 h, Centrifuge, filter, wash with deionized water to remove residual monomers on the surface of the polymer, and dry; dissolve the dried powder in N,N-dimethylformamide to make a concentration of 20% by mass solution, and then form a film, dry the film to obtain an anion exchange membrane; finally, immerse the membrane in 2 mol/L NaOH aqueous solution for 60 h, take it out and wash it with deionized water to obtain a basic anion exchange membrane. Figure 3 is a graph showing the relationship between the mass change and time of polyarylsulfone-based plasma-grafted basic anion exchange membranes soaked in 3 wt% H ₂ O ₂ . It can be found that the basic anion exchange membranes have good chemical stability. At the same time, the alkaline anion exchange membrane has a high ion conductivity (10 ^-3 S/cm order) measured by electrochemical impedance spectroscopy, and the alkaline anion exchange membrane has a low ethanol permeation rate measured by the open circuit potential method. rate (10 ^-13 m ² /s order of magnitude).

Claims (6)

1. plasma grafting is prepared a method for alkaline anion-exchange membrane, it is characterized in that comprising the following steps:

(1) polymer powder is placed in to plasma discharge, and constantly stirs polymer powder; Opening power, produces plasma discharge, and discharge power is 50-250 W, and plasma discharge is processed 10-60 min;

(2) powder after step (1) is plasma-activated is placed in vinyl benzyl chlorination aqueous ammonium, and be warmed up to 40-60 ℃, stir 8-72 h, make the graft polymerization on powder of vinyl benzyl chlorination ammonium monomer, in polymer powder surface, introduce anion exchange groups;

(3) step (2) reaction is finished the mixture that makes centrifugal, filter, then use deionized water wash, oven dry, the powder of oven dry is dissolved in solvent, be then coated with and cast film, make anion-exchange membrane;

(4) anion-exchange membrane making is immersed in 1-2 mol/L alkaline solution, soak time 10-60 h, then takes out film, with deionized water wash, immersion, makes alkaline anion-exchange membrane.

2. plasma grafting according to claim 1 is prepared the method for alkaline anion-exchange membrane, it is characterized in that: described polymer powder is selected from one or more mixing in polyethersulfone, polyarylsulphone, polyetherketone, polyether-ether-ketone, polyphenylene sulfide, polyvinyl chloride, polyethylene, polyimide, and described polymer powder particle diameter should be not more than 200 μ m.

3. plasma grafting according to claim 1 is prepared the method for alkaline anion-exchange membrane, it is characterized in that: described plasma source is selected from one or more mixing in argon plasma body source, nitrogen plasma body source, oxygen plasma body source, helium plasma source, hydrogen gas plasma source, aqueous vapor plasma source, air plasma body source.

4. plasma grafting according to claim 1 is prepared the method for alkaline anion-exchange membrane, it is characterized in that: described plasma body is selected from a kind of in subatmospheric low-temperature plasma, high atmospheric pressure low-temperature plasma and atmos low-temperature plasma.

5. plasma grafting according to claim 1 is prepared the method for alkaline anion-exchange membrane, it is characterized in that: described vinyl benzyl chlorination aqueous ammonium concentration is 10-80 wt%.

6. plasma grafting according to claim 1 is prepared the method for alkaline anion-exchange membrane, it is characterized in that: the described solvent of step (3) is selected from one or more mixing in tetrahydrofuran (THF), toluene, dimethylbenzene, tetramethylene sulfone, dimethyl formamide, dimethyl sulfoxide (DMSO), tetramethylene sulfoxide, methyl-2-pyrrolidone.

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