CN115010907A

CN115010907A - Polyarylpiperidine type anion exchange membrane containing hydrophilic and hydrophobic double side chains and preparation method thereof

Info

Publication number: CN115010907A
Application number: CN202210665437.1A
Authority: CN
Inventors: 许莉; 王慧敏; 许卫
Original assignee: Tianjin Mainland Hydrogen Equipment Co ltd
Current assignee: Tianjin Mainland Hydrogen Equipment Co ltd
Priority date: 2022-06-14
Filing date: 2022-06-14
Publication date: 2022-09-06

Abstract

The invention provides a polyarylpiperidine type anion exchange membrane containing hydrophilic and hydrophobic double side chains and a preparation method thereof, belonging to the technical field of anion exchange membranes. The anion exchange membrane is prepared by grafting hydrophilic bromo-6C-piperidine and hydrophobic bromo-n-hexane with different molar ratios on a main chain of polyarylpiperidine. The anion exchange membrane takes the polyaryl piperidine without ether bonds as a main chain, ensures the alkaline stability of the anion exchange membrane, and grafts hydrophilic and hydrophobic side chains with different proportions to form a comb-shaped structure to promote the microphase separation of the anion exchange membrane so as to improve the ionic conductivity of the anion exchange membrane and solve the problem of poor ionic conductivity of the anion exchange membraneThe trade-off problem between the alkali resistance stability and the ion conductivity of the anion exchange membrane is solved. The experimental results show that: the anion exchange membrane prepared by the invention has an obvious microphase separation structure and shows excellent conductivity (112 mS cm at 80℃) ^‑1 ) And dimensional stability. In addition, the conductivity can still keep more than 90% after soaking in 1mol/L NaOH solution at 80 ℃ for 720h, and the excellent alkali-resistant stability is shown.

Description

Polyarylpiperidine type anion exchange membrane containing hydrophilic and hydrophobic double side chains and preparation method thereof

Technical Field

The invention belongs to the technical field of anion exchange membranes, and particularly relates to a polyarylpiperidine type anion exchange membrane containing hydrophilic and hydrophobic double side chains and a preparation method thereof.

Background

Nowadays, energy crisis and environmental pollution are becoming more severe, threatening the survival and development of human beings. The development of renewable energy sources and the sustainable development path become the focus of research of various national scholars. Hydrogen energy is recognized as the most potential energy carrier in the future due to the characteristics of cleanness and high efficiency. Among the various current hydrogen production technologies, the use of electrical energy generated by renewable energy sources as a power to electrolyze water is the most mature and potential technology, considered the best path to the hydrogen economy. With the increasingly deep and wide development of hydrogen energy research, the technology of hydrogen production by water electrolysis is also developed rapidly.

Among many hydrogen production processes, the hydrogen production by alkaline electrolysis of water has a high chemical reaction rate of the anode due to the reaction in an alkaline environment, which is conducive to oxidation, so that a catalyst with low activity can be selected to replace a noble metal catalyst, the use cost is greatly reduced, and the operation is easy, so that the hydrogen production process is widely used. Anion Exchange Membranes (AEMs) are core components in alkaline electrolyzers, the performance of which has a crucial influence on the performance of alkaline electrolyzers. High hydroxide conductivity is a necessary condition for improving energy efficiency and power density, and alkali resistance is crucial for the durability of the electrolytic cell. Therefore, the development of anion exchange membranes with long-term alkali resistance stability and high conductivity is a major approach to promote the rapid development of alkaline electrolyzed water.

Many anion exchange membrane materials based on a polysulfone, polyphenylene oxide, polyetheretherketone, or the like framework have been developed. However, it has been found that these polymer backbones containing ether linkages are susceptible to degradation under alkaline conditions. Accordingly, AEMs that produce aromatic polymer backbones without ether linkages are of great interest. The polyarylalpiperidine is a novel ether bond-free skeleton, which has high structural rigidity and dimensional stability. In addition, it can be synthesized by simple superacid catalyzed Friedel-crafts polymerization, and has the advantages of adjustable cationic sites and controllable degree of functionalization. Numerous studies have demonstrated excellent stability under alkaline conditions. However, its main chain structure results in the cationic functional groups being close to the polymer backbone, limiting the aggregation of the cationic groups and preventing the formation of broad ion transport channels. Therefore, the development of an anion exchange membrane with both high conductivity and long-term alkali resistance stability is a technical problem to be solved urgently in the field.

Disclosure of Invention

In view of the above, the present invention provides a method for preparing a polyarylpiperidine anion exchange membrane with high conductivity and high alkali resistance stability. The anion exchange membrane adopts high-alkali-resistance stable poly-m-terphenyl piperidine as a framework, and simultaneously introduces a hydrophilic and hydrophobic double side chains to regulate an intramembrane microphase separation structure so as to improve the conductivity. The prepared anion exchange membrane has higher conductivity and better alkali-resistant stability, and can be applied to equipment such as alkaline electrolyzed water and the like.

The technical scheme of the invention is as follows:

a polyarylpiperidine type anion exchange membrane containing hydrophilic and hydrophobic double side chains has a general structural formula as follows:

wherein x is the mole percentage of the hydrophilic side chain 6C-piperidine, and the value range of x is 0-50; y is the mole percentage of the hydrophobic side chain bromo-n-hexane, and the value of y is 0-100. When X or y is 0, the two special cases are that only hydrophilic side chains or only hydrophobic side chains are grafted.

A preparation method of a polyarylpiperidine type anion exchange membrane containing hydrophilic and hydrophobic double side chains comprises the following steps:

the method comprises the following steps: m-terphenyl and N-methyl-4-piperidone were dissolved in dichloromethane, and trifluoroacetic acid TFA and trifluoromethanesulfonic acid TFSA were then added dropwise under an ice-water bath. After reacting for 4 hours, precipitating the reaction solution in 5mol/LNaOH solution, washing with deionized water until the solution is neutral, and finally drying to obtain poly-m-terphenyl piperidine polymer;

step two: dissolving 1, 6-dibromohexane and N-methylpiperidine in ethyl acetate, reacting at 40 ℃ for 48h, washing the reaction solution with ethyl acetate for three times, filtering and drying to obtain a hydrophilic side chain which is recorded as 6C-piperidine polymer.

Step three: dissolving the poly-m-terphenyl piperidine polymer obtained in the step one in 1-methyl-2-pyrrolidone NMP, adding n-bromo-hexane at 80 ℃ for reacting for 24 hours, adding the 6C-piperidine polymer obtained in the step two, and continuing to react for 24 hours to finally obtain a polymer solution;

step four: forming a film on the glass plate by the polymer solution obtained in the step three by adopting a casting method, and drying to obtain an anion exchange membrane;

step five: and (3) stripping the anion exchange membrane obtained in the step four from the glass plate, soaking the anion exchange membrane in 1mol/LNaOH solution for 48h, and then washing the anion exchange membrane with deionized water until the anion exchange membrane is neutral, thus obtaining the polyarylpiperidine type anion exchange membrane containing hydrophilic and hydrophobic double side chains.

In the first step, the molar ratio of the intermediate terphenyl to the N-methyl-4-piperidone is 1: 1.3.

The volume ratio of TFA to dichloromethane in the first step is 1: 6.2.

The volume ratio of TFSA to dichloromethane in the first step is 1: 0.62.

The drying temperature in the first step is 60-80 ℃, and the drying time is 12-24 h.

In the second step, the molar ratio of the 1, 6-dibromohexane to the N-methylpiperidine is 1: 0.66.

The drying temperature in the second step is 25-40 ℃, and the drying time is 24-48 h.

The molar ratio of the n-bromohexane to the poly-m-terphenyl piperidine polymer in the step III is 0-1: 1.

The molar ratio of the 6C-piperidine to the poly-m-terphenyl piperidine polymer in the third step is 0-0.5: 1.

The drying temperature in the fourth step is 60-80 ℃, and the drying time is 12-24 h.

The invention has the beneficial effects that:

the invention provides a polyarylpiperidine type anion exchange membrane containing hydrophilic and hydrophobic double side chains and a preparation method thereof. The anion exchange membrane takes the polyarylpiperidine without ether bonds as a main chain, and ensures the alkaline stability of the anion exchange membrane.

In addition, the hydrophilic cationic piperidine group is linked to the main chain through a hexyl spacer chain to improve the fluidity and stability of the cationic group.

Meanwhile, the introduction of the hydrophobic alkyl side chain can improve the microphase separation structure, further improve the conductivity and limit the excessive swelling of the membrane.

The functionalization degree of the anion exchange membrane can be changed by regulating the grafting amount of the hydrophilic and hydrophobic side chains so as to prepare anion exchange membranes with different performances.

The invention provides a method for solving the balance problem between the alkali resistance stability and the ion conductivity of an anion exchange membrane.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a nuclear magnetic resonance hydrogen spectrum of a hydrophilic side chain-containing polyarylaiperidine type anion exchange membrane prepared in example 1 of the present invention, which shows an ion exchange capacity;

FIG. 2 is a nuclear magnetic resonance hydrogen spectrum of a polyarylpiperidine-type anion exchange membrane containing hydrophobic side chains prepared in example 2 of the present invention, which shows ion exchange capacity;

FIG. 3 is a NMR spectrum of a polyarylpiperidine-type anion exchange membrane containing hydrophilic and hydrophobic double side chains prepared in example 3 of the present invention, showing the ion exchange capacity;

FIG. 4 is a NMR spectrum of an anion exchange membrane of the type polyarylpiperidine having hydrophilic and hydrophobic double side chains prepared in example 4 of the present invention, showing the ion exchange capacity;

FIG. 5 shows the change of water absorption with temperature of the polyarylpiperidine anion exchange membranes containing hydrophilic and hydrophobic double side chains prepared in examples 1 to 4 of the present invention (the abscissa represents temperature and the ordinate represents water absorption);

FIG. 6 shows the change of swelling ratio with temperature of the polyarylamide type anion exchange membranes having hydrophilic and hydrophobic double side chains prepared in examples 1 to 4 of the present invention (the abscissa represents temperature and the ordinate represents swelling ratio);

FIG. 7 shows the temperature dependence of conductivity of the anion-exchange membranes of the type polyarylpiperidine having hydrophilic and hydrophobic double side chains prepared in examples 1 to 4 of the present invention (temperature on the abscissa and conductivity on the ordinate).

Detailed Description

The embodiments of the invention are described in further detail below with reference to the following figures:

example 1:

synthesis of Poly-m-terphenyl piperidine Polymer:

mixing 8.7mmol of m-terphenyl, 11.3mmol of N-methyl-4-piperidone and 5mL of dichloromethane in a three-neck flask;

then, under ice bath, TFA0.8mL and TFSA8mL were added dropwise to a three-necked flask;

after magnetic stirring for 4h, the resulting viscous dark brown mixture was slowly poured into 5mol/LNaOH solution to form a white precipitate;

after filtration, the white fibrous solid obtained was washed to neutrality with deionized water and dried under vacuum at 60 ℃ for 24 h.

Synthesis of 6C-piperidine Polymer:

dissolving 61.8mmol of 1, 6-dibromohexane in 40mL of ethyl acetate;

then, 41.0mmol of 1-methylpiperidine is added dropwise under the condition of continuous stirring, and the mixture reacts for 48 hours at the temperature of 40 ℃;

the resulting white powder was filtered and washed 3 times with ethyl acetate and dried under vacuum at 30 ℃ for 24 h.

Synthesis of a polyarylpiperidine type anion exchange membrane containing hydrophilic and hydrophobic double side chains:

uniformly mixing 0.93mmol of poly-m-terphenyl piperidine polymer and 10mL of NMP solution in a three-neck flask;

then adding 0.34mmol of 6C-piperidine polymer into the mixed solution, and continuing to react for 24h at 80 ℃;

casting the resulting mixed solution on a glass plate and drying at 80 ℃ for 18h to obtain an anion-exchange membrane;

peeling the membrane from the glass plate in deionized water, and soaking the obtained anion exchange membrane in 1mol/LNaOH solution for 48h to ensure that anions are completely exchanged with hydroxide ions;

and soaking the obtained membrane in deionized water and washing to neutrality to obtain the polyarylpiperidine type anion exchange membrane containing hydrophilic side chains.

The anion exchange membrane prepared in this example has the following structure:

FIG. 1 is the NMR spectrum of AEM prepared in example 1, and it can be seen that example 1 successfully synthesizes an anionic exchange membrane of the type polyarylpiperidine having hydrophilic side chains. Experimental results show that the ion exchange capacity of the polyarylpiperidine type anion-exchange membrane containing hydrophilic side chains prepared in the example is 1.66 mmol/g. It has a water absorption of 66%, a swelling rate of 38% and an electrical conductivity of 87mS/cm at 80 ℃. In addition, after the membrane is soaked in 1mol/LNaOH solution at 80 ℃ for 720h, the conductivity retention rate is 93%, and the anion exchange membrane shows good conductivity and alkali-resistant stability.

Example 2:

this example is the case where only a hydrophobic side chain is grafted when x is 0, and thus there is no step of synthesizing a hydrophilic side chain.

Synthesis of Poly-m-terphenyl piperidine Polymer:

adding 0.64mmol of bromo-n-hexane into the mixed solution, and continuing to react for 24 hours at 80 ℃;

and soaking the obtained membrane in deionized water and washing the membrane to be neutral to obtain the polyarylpiperidine type anion exchange membrane containing hydrophobic side chains.

FIG. 2 is the NMR spectrum of AEM prepared in example 2, from which it can be seen that example 2 successfully synthesizes a polyarylpiperidine type anion exchange membrane having hydrophobic side chains. The experimental results show that the ion exchange capacity of the polyarylpiperidine type anion exchange membrane containing hydrophobic side chains prepared in the example is 1.58 mmol/g. It has a water absorption of 31%, a swelling ratio of 10% and an electrical conductivity of 25mS/cm at 80 ℃. In addition, after soaking in 1mol/LNaOH solution at 80 ℃ for 720h, the conductivity retention rate is 90%.

Example 3:

synthesis of Poly-m-terphenyl piperidine Polymer:

Synthesis of 6C-piperidine Polymer:

dissolving 61.8mmol of 1, 6-dibromohexane in 40mL of ethyl acetate;

then adding 0.08mmol of bromo-n-hexane into the mixed solution, and reacting for 24h at 80 ℃;

then adding 0.30mmol of 6C-piperidine polymer into the mixed solution, and continuing to react for 24 hours at 80 ℃;

finally the resulting mixed solution was cast on a glass plate and dried at 80 ℃ for 18h to obtain an anion exchange membrane;

and soaking the obtained membrane in deionized water and washing to neutrality to obtain the polyarylpiperidine type anion exchange membrane containing hydrophilic and hydrophobic double side chains.

FIG. 3 is the NMR spectrum of AEM prepared in example 3, from which it can be seen that example 3 successfully synthesizes an anion exchange membrane of the polyarylpiperidine type containing hydrophilic and hydrophobic double side chains. The experimental results show that the ion exchange capacity of the polyarylpiperidine-type anion exchange membrane containing hydrophilic and hydrophobic double side chains prepared in this example is 1.68 mmol/g. It has a water absorption of 58%, a swelling ratio of 37% and an electrical conductivity of 112mS/cm at 80 ℃. In addition, after the membrane is soaked in 1mol/LNaOH solution at 80 ℃ for 720h, the conductivity retention rate is 92%, and the anion exchange membrane shows good conductivity and alkali-resistant stability.

Example 4:

synthesis of Poly-m-terphenyl piperidine Polymer:

after magnetic stirring for 4h, the resulting viscous dark brown mixture was slowly poured into 5mol/L NaOH solution to form a white precipitate;

Synthesis of 6C-piperidine Polymer:

dissolving 61.8mmol of 1, 6-dibromohexane in 40mL of ethyl acetate;

then adding 0.17mmol of bromo-n-hexane into the mixed solution, and reacting for 24h at 80 ℃;

then adding 0.25mmol of 6C-piperidine polymer into the mixed solution, and continuing to react for 24 hours at 80 ℃;

FIG. 4 is the NMR spectrum of AEM prepared in example 4, from which it can be seen that example 4 successfully synthesizes an anion exchange membrane of the type polyarylpiperidine containing hydrophilic and hydrophobic double side chains. Experimental results prove that the ion exchange capacity of the polyarylpiperidine type anion exchange membrane containing hydrophilic and hydrophobic double side chains prepared in the embodiment is 1.64 mmol/g. At 80 ℃, the water absorption rate is 48%, the swelling rate is 35%, and the conductivity is 96 mS/cm. In addition, after the membrane is soaked in 1mol/LNaOH solution for 720h at 80 ℃, the conductivity retention rate is 89%, and the anion exchange membrane shows good conductivity and alkali resistance stability.

FIG. 5 shows the water absorption rate of the polyarylamide type anion exchange membranes having hydrophilic and hydrophobic double side chains prepared in examples 1 to 4 of the present invention, which varies with temperature. It can be seen that, with the increase of the grafting rate of the hydrophilic side chain 6C piperidine, the hydrophilicity of AEMs is enhanced, and the water absorption rate is increased continuously. Wherein, the embodiment 1 has the highest water absorption rate of 66 percent at 80 ℃, can still maintain the dimensional stability thereof, and completely meets the use requirements of devices such as electrolytic water and the like.

FIG. 6 shows the swelling ratio of the polyarylamide type anion-exchange membranes having hydrophilic and hydrophobic double side chains prepared in examples 1 to 4 of the present invention as a function of temperature. It can be seen that the water absorption and thus swelling rate increases with increasing grafting of the hydrophilic side chain 6C piperidine. Wherein, the embodiment 1 has the highest swelling rate of 38 percent at 80 ℃, can still maintain the dimensional stability and completely meet the use requirements of devices such as electrolytic water and the like.

FIG. 7 shows the temperature dependence of conductivity of the anion-exchange membranes of the type polyarylpiperidine having hydrophilic and hydrophobic double side chains prepared in examples 1 to 4 of the present invention. It can be seen that example 3 has the highest conductivity of 112mS/cm, and therefore, the control of the grafting ratio of the hydrophilic and hydrophobic side chains has a crucial influence on the performance of the anion exchange membrane.

Although the embodiments of the present invention and the accompanying drawings are disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the disclosure of the embodiments and the accompanying drawings.

Claims

1. A polyarylpiperidine anion exchange membrane containing hydrophilic and hydrophobic double side chains is characterized in that the membrane material has the following structure:

wherein x is the mole percentage of the hydrophilic side chain 6C-piperidine, and the value range of x is 0-50; y is the mole percentage of the hydrophobic side chain bromo-n-hexane, and the value range of y is 0-100.

2. A process for the preparation of the hydrophilic and hydrophobic bis-sidechain containing polyarylpiperidine anion exchange membranes according to claim 1, characterized in that: the preparation method comprises the following steps:

the method comprises the following steps: dissolving m-terphenyl and N-methyl-4-piperidone in dichloromethane, then dropwise adding trifluoroacetic acid and trifluoromethanesulfonic acid in an ice water bath, reacting for 4h, precipitating the reaction solution in a 5mol/LNaOH solution, washing with deionized water until the solution is neutral, and finally drying to obtain a poly-m-terphenyl piperidine polymer;

step two: dissolving 1, 6-dibromohexane and N-methylpiperidine in ethyl acetate, reacting for 48h at 40 ℃, washing the reaction solution with ethyl acetate for three times, filtering and drying to obtain a hydrophilic side chain 6C-piperidine polymer;

step three: dissolving the poly-m-terphenyl piperidine polymer obtained in the step one in 1-methyl-2-pyrrolidone, adding n-bromo-hexane at 80 ℃ for reacting for 24 hours, adding the 6C-piperidine polymer obtained in the step two, and continuing to react for 24 hours to finally obtain a polymer solution;

3. The process for preparing an anion-exchange membrane of the polyarylpiperidine type containing hydrophilic and hydrophobic double side chains according to claim 2, characterized in that: in the first step, the molar ratio of the intermediate terphenyl to the N-methyl-4-piperidone is 1: 1.3; the volume ratio of trifluoroacetic acid to dichloromethane is 1: 6.2; the volume ratio of the trifluoromethanesulfonic acid to the dichloromethane is 1: 0.62; the drying temperature in the first step is 60-80 ℃, and the drying time is 12-24 h.

4. The process for preparing an anion-exchange membrane of the polyarylpiperidine type containing hydrophilic and hydrophobic double side chains according to claim 2, characterized in that: in the second step, the mol ratio of the 1, 6-dibromohexane to the N-methylpiperidine is 1:0.66, the drying temperature is 25-40 ℃, and the drying time is 24-48 h.

5. The process for preparing an anion-exchange membrane of the polyarylpiperidine type containing hydrophilic and hydrophobic double side chains according to claim 2, characterized in that: in the step III, the molar ratio of the n-bromohexane to the poly-m-terphenyl piperidine polymer is 0-1:1, and the molar ratio of the 6C-piperidine polymer to the poly-m-terphenyl piperidine polymer is 0-0.5: 1.

6. The process for preparing an anion-exchange membrane of the polyarylpiperidine type containing hydrophilic and hydrophobic double side chains according to claim 2, characterized in that: the drying temperature required by the drying in the fourth step is 60-80 ℃, and the drying time is 12-24 h.