Preparation method of brominated beta cyclodextrin and polybenzimidazole composite proton exchange membrane

Abstract

The invention discloses a preparation method of a brominated beta cyclodextrin and polybenzimidazole composite proton exchange membrane, and relates to the technical field of high-temperature proton exchange membrane fuel cells. The invention aims to solve the technical problem that the proton conductivity is reduced in a short time due to the fact that the existing method improves the PA absorbing capacity but cannot optimize the PA holding capacity. The method comprises the following steps: preparing 2, 2 '-(m-phenyl)-5, 5'-bibenzimidazole; preparing brominated beta cyclodextrin; and preparing the composite membrane of the brominated beta cyclodextrin and the PBI. The proton exchange membrane prepared by the invention has polyfunctional group quaternary ammonium salt, and provides more proton jump sites; the proton exchange membrane can absorb more PA, so that the proton conductivity of the membrane is improved, and the proton exchange membrane has certain acid retention capacity. The method is used for preparing the proton exchange membrane.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature proton exchange membrane fuel cells, and in particular to a multi-functional quaternary ammonium salt composite poly[2,2'-(meta-phenyl)-5,5'-bibenzimidazole] proton exchange membrane with high proton conductivity. Background Art

[0002] Proton exchange membrane (PEM) has the advantages of environmental friendliness, high energy conversion efficiency, and rapid response. It is one of the clean energy sources with lower cost and longer life. These characteristics have attracted widespread attention.

[0003] At present, the research on proton exchange membranes has become mature, and various types of proton exchange membranes have achieved certain results, but there are still some aspects that need to be improved and factors that need to be optimized. For example, proton exchange membranes doped with high phosphoric acid have better proton transfer capabilities, and quaternary ammonium anions can effectively fix phosphoric acid (PA). In the past, the number of quaternary ammonium anions on quaternary ammonium proton exchange membranes was small, which resulted in a limited content of PA bound and anchored to it, which to a certain extent limited the PA absorption capacity and proton conductivity; secondly, the proton exchange membrane's ability to retain PA also needs to be improved. At this stage, research often improves the PA absorption amount but cannot optimize the ability to retain PA, resulting in a decrease in proton conductivity in a short period of time, limiting the scope and field of use of proton exchange membranes. Therefore, solving the above problems has become a new challenge for the application of high-temperature proton exchange membranes. Summary of the invention

[0004] In order to solve the technical problem that the existing method improves the PA absorption but cannot optimize the PA retention capacity, resulting in a decrease in proton conductivity in a short time, the present invention provides a method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane.

[0005] A method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane is specifically carried out according to the following steps:

[0006] Step 1: Preparation of 2,2'-(m-phenyl)-5,5'-bibenzimidazole

[0007] Dissolve diaminobenzidine and isophthalic acid in polyphosphoric acid, control the temperature between 120 and 140°C, and stir mechanically under nitrogen protection; after complete dissolution, raise the temperature to 200°C, and continue the reaction until the product becomes viscous;

[0008] The viscous product is poured into a sodium bicarbonate solution, washed repeatedly until neutral, and dried to obtain 2,2'-(m-phenyl)-5,5'-bibenzimidazole;

[0009] Step 2: Preparation of brominated β-cyclodextrin

[0010] Dissolve β-cyclodextrin and N-bromosuccinimide in NN-dimethylacetamide, add triphenylphosphine as a polymer initiator, and react for 20 to 24 hours at a temperature of 80°C under nitrogen protection; then pour into methanol and stir to obtain a precipitate, then wash the precipitate with methanol aqueous solution until the washing liquid is colorless; then dry to obtain brominated β-cyclodextrin;

[0011] Step 3: Preparation of phosphoric acid / bromo-β-cyclodextrin / PBI composite membrane

[0012] The 2,2'-(m-phenyl)-5,5'-bibenzimidazole obtained in step 1 and the brominated β-cyclodextrin obtained in step 2 are dissolved in NN-dimethylacetamide, and stirred for 24 hours at a temperature of 60-80° C. under nitrogen protection, and then poured onto a horizontal glass plate, cast into a film, and dried to obtain a brominated β-cyclodextrin and PBI composite film;

[0013] The brominated β-cyclodextrin and PBI composite membrane is immersed in a trimethylamine solution to carry out a quaternization reaction, and then the surface of the composite membrane is washed with distilled water, dried and immersed in a phosphoric acid solution with a mass concentration of 85% for 48 hours to obtain the brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane.

[0014] The synthetic reaction formula of 2,2'-(m-phenyl)-5,5'-bibenzimidazole (PBI) is:

[0015]

[0016] The synthetic reaction formula of brominated β-cyclodextrin (Br-CD) is:

[0017]

[0018] Beneficial effects of the present invention:

[0019] The proton exchange membrane has multi-functional quaternary ammonium salts, which provide more proton hopping sites. Since each quaternary ammonium salt ion can bind to a PA, and the PAs are anchored to each other through hydrogen bonds to form a continuous proton transfer channel, the proton exchange membrane can absorb more PAs to improve the proton conductivity of the membrane, and has a certain acid retention capacity.

[0020] The invention is used for preparing a proton exchange membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1SEM images of 2,2'-(meta-phenyl)-5,5'-bibenzimidazole (PBI) prepared in the control example and the brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane (PBI-BC-X) prepared in the example, wherein Figure (a) is a cross-sectional SEM image of PBI, Figure (b) is a cross-sectional SEM image of PBI-BC-10%, Figure (c) is a cross-sectional SEM image of PBI-BC-20%, Figure (d) is a cross-sectional SEM image of PBI-BC-30%, Figure (e) is a surface SEM image of PBI, Figure (f) is a surface SEM image of PBI-BC-10%, Figure (g) is a surface SEM image of PBI-BC-20%, and Figure (h) is a surface SEM image of PBI-BC-30%;

[0022] Figure 2 The infrared spectra of 2,2'-(m-phenyl)-5,5'-bibenzimidazole (PBI) prepared in the control example and the brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane (PBI-BC-X) prepared in the example;

[0023] Figure 3 The acid loss diagrams of 2,2'-(m-phenyl)-5,5'-bibenzimidazole (PBI) prepared in the control example and the brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane (PBI-BC-X) prepared in the example;

[0024] Figure 4 The proton conductivity diagram of 2,2'-(m-phenyl)-5,5'-bibenzimidazole (PBI) prepared in the control example and the brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane (PBI-BC-X) prepared in the example. DETAILED DESCRIPTION

[0025] Specific implementation method 1: This implementation method is a method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane, which is specifically carried out according to the following steps:

[0026] Step 1: Preparation of 2,2'-(m-phenyl)-5,5'-bibenzimidazole

[0027] Dissolve diaminobenzidine and isophthalic acid in polyphosphoric acid, control the temperature between 120 and 140°C, and stir mechanically under nitrogen protection; after complete dissolution, raise the temperature to 200°C, and continue the reaction until the product becomes viscous;

[0028] The viscous product is poured into a sodium bicarbonate solution, washed repeatedly until neutral, and dried to obtain 2,2'-(m-phenyl)-5,5'-bibenzimidazole;

[0029] Step 2: Preparation of brominated β-cyclodextrin

[0030] Dissolve β-cyclodextrin and N-bromosuccinimide in NN-dimethylacetamide, add triphenylphosphine as a polymer initiator, and react for 20 to 24 hours at a temperature of 80°C under nitrogen protection; then pour into methanol and stir to obtain a precipitate, then wash the precipitate with methanol aqueous solution until the washing liquid is colorless; then dry to obtain brominated β-cyclodextrin;

[0031] Step 3: Preparation of phosphoric acid / bromo-β-cyclodextrin / PBI composite membrane

[0032] The 2,2'-(m-phenyl)-5,5'-bibenzimidazole obtained in step 1 and the brominated β-cyclodextrin obtained in step 2 are dissolved in NN-dimethylacetamide, and stirred for 24 hours at a temperature of 60-80° C. under nitrogen protection, and then poured onto a horizontal glass plate, cast into a film, and dried to obtain a brominated β-cyclodextrin and PBI composite film;

[0033] The brominated β-cyclodextrin and PBI composite membrane is immersed in a trimethylamine solution to carry out a quaternization reaction, and then the surface of the composite membrane is washed with distilled water, dried and immersed in a phosphoric acid solution with a mass concentration of 85% for 48 hours to obtain the brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane.

[0034] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that the mass ratio of diaminobenzidine, isophthalic acid and polyphosphoric acid in step 1 is 5.6:4.3:80. The rest is the same as specific embodiment 1.

[0035] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the mechanical stirring speed in step 1 is 200-300 rpm. Other aspects are the same as specific implementation method 1 or 2.

[0036] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the concentration of the sodium bicarbonate solution in step 1 is 2 mol / L. The rest is the same as specific embodiments 1 to 3.

[0037] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the molar ratio of β-cyclodextrin to N-bromosuccinimide in step 2 is 1:14, and the amount of triphenylphosphine used is 1.5 g. Others are the same as specific embodiments 1 to 4.

[0038] Specific implementation method 6: This implementation method is different from specific implementation methods 1 to 5 in that: in step 2, the stirring speed is controlled to be 500-600 rpm. The rest is the same as specific implementation methods 1 to 5.

[0039] Specific embodiment 7: This embodiment differs from Specific embodiments 1 to 6 in that the volume ratio of distilled water to methanol in the methanol aqueous solution in step 2 is 1:1. The rest is the same as Specific embodiments 1 to 6.

[0040] Specific embodiment eight: This embodiment differs from specific embodiments one to seven in that the mass ratio of 2,2'-(m-phenyl)-5,5'-bibenzimidazole, brominated β-cyclodextrin and NN-dimethylacetamide in step three is 1:(0.05-0.3):25. The rest is the same as specific embodiments one to seven.

[0041] Specific embodiment 9: This embodiment is different from specific embodiments 1 to 8 in that the thickness of the composite film in step 3 is 80 to 100 μm. The rest is the same as specific embodiments 1 to 8.

[0042] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that the quaternization reaction time in step 3 is controlled to be 48 to 72 hours. The rest is the same as specific embodiments 1 to 9.

[0043] The content of the present invention is not limited to the content of the above-mentioned embodiments. The combination of one or several specific embodiments can also achieve the purpose of the invention.

[0044] Embodiment 1:

[0045] A method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane is specifically carried out according to the following steps:

[0046] Step 1: Preparation of 2,2'-(m-phenyl)-5,5'-bibenzimidazole (PBI)

[0047] Dissolve 5.6g of diaminobenzidine and 4.3g of isophthalic acid in 80g of polyphosphoric acid, control the temperature to 160°C, and stir mechanically under nitrogen protection; after complete dissolution, raise the temperature to 200°C, and continue the reaction until the product becomes viscous;

[0048] The viscous product is poured into a 2 mol / L sodium bicarbonate solution, washed repeatedly until neutral, and dried to obtain 2,2'-(m-phenyl)-5,5'-bibenzimidazole (PBI);

[0049] Step 2: Preparation of brominated β-cyclodextrin (Br-CD)

[0050] β-cyclodextrin and N-bromosuccinimide were dissolved in NN-dimethylacetamide, the molar ratio of β-cyclodextrin to N-bromosuccinimide was 1:14, 1.5 g of polymer initiator triphenylphosphine was added, and the temperature was controlled at 80°C under nitrogen protection conditions, and the reaction was carried out for 24 hours; then the mixture was poured into methanol and stirred to obtain a precipitate, and then the precipitate was washed with a methanol aqueous solution until the washing liquid turned from yellow to transparent; then the mixture was dried in an oven at 60°C to obtain brominated β-cyclodextrin (Br-CD);

[0051] Step 3: Preparation of phosphoric acid / bromo-β-cyclodextrin / PBI composite membrane (PBI-BC-X)

[0052] Dissolve 1g of 2,2'-(m-phenyl)-5,5'-bibenzimidazole obtained in step 1 and 0.05g of brominated β-cyclodextrin obtained in step 2 in 25g of N-N-dimethylacetamide, react at 80°C under nitrogen protection for 24h, then pour onto a clean glass plate, cast into a film, and dry to obtain a brominated β-cyclodextrin and PBI composite film;

[0053] The brominated β-cyclodextrin and PBI composite membrane was immersed in a trimethylamine solution for 48 hours to carry out a quaternization reaction, and then the surface of the composite membrane was rinsed with distilled water, dried and immersed in a phosphoric acid solution with a mass concentration of 85% for 48 hours to obtain the brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane (PBI-BC-5%).

[0054] The mechanical stirring speed in step 1 is 300 rpm;

[0055] Step 2: Control the stirring speed to 500 rpm;

[0056] The volume ratio of distilled water to methanol in the methanol aqueous solution in step 2 is 1:1;

[0057] The thickness of the composite film in step 3 is 80-90 μm.

[0058] Embodiment 2:

[0059] The difference between this embodiment and the first embodiment is that the amount of brominated β-cyclodextrin used in step 3 is 0.1 g, and the obtained product is a composite proton exchange membrane of brominated β-cyclodextrin and polybenzimidazole (PBI-BC-10%). The other parameters and steps are the same as those in the first embodiment.

[0060] Embodiment three:

[0061] The difference between this embodiment and the first embodiment is that the amount of brominated β-cyclodextrin used in step 3 is 0.15 g, and the obtained product is a composite proton exchange membrane of brominated β-cyclodextrin and polybenzimidazole (PBI-BC-15%). The other parameters and steps are the same as those in the first embodiment.

[0062] Embodiment 4:

[0063] The difference between this embodiment and the first embodiment is that the amount of brominated β-cyclodextrin used in step 3 is 0.20 g, and the obtained product is a composite proton exchange membrane of brominated β-cyclodextrin and polybenzimidazole (PBI-BC-20%). The other parameters and steps are the same as those in the first embodiment.

[0064] Embodiment five:

[0065] The difference between this embodiment and the first embodiment is that the amount of brominated β-cyclodextrin used in step 3 is 0.25 g, and the obtained product is a composite proton exchange membrane of brominated β-cyclodextrin and polybenzimidazole (PBI-BC-25%). The other parameters and steps are the same as those in the first embodiment.

[0066] Embodiment six:

[0067] The difference between this embodiment and the first embodiment is that the amount of brominated β-cyclodextrin used in step 3 is 0.30 g, and the obtained product is a composite proton exchange membrane of brominated β-cyclodextrin and polybenzimidazole (PBI-BC-30%). The other parameters and steps are the same as those in the first embodiment.

[0068] Comparison example:

[0069] This comparative example is 2,2'-(m-phenyl)-5,5'-bibenzimidazole prepared in Example, which is then prepared into a film (PBI).

[0070] The absorption capacity, ADL and volume swelling test results of the PBI prepared in the control example and the brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane prepared in the example for PA are shown in Table 1:

[0071] Table 1

[0072] Samples PA uptake (wt.%) ADL Swelling(%) PBI 185.6±5.8 5.8±0.2 125.7±2.0 PBI-BC-5% 226.9±1.3 7.5±0.4 141.0±4.4 PBI-BC-10% 270.3±8.0 9.3±0.3 153.5±3.0 PBI-BC-15% 342.1±9.2 12.4±0.3 173.0±3.5 PBI-BC-20% 419.3±8.5 15.8±0.3 192.2±3.1 PBI-BC-25% 389.7±7.2 15.3±0.3 184.5±3.6 PBI-BC - 30% 369.5±1.6 15.1±0.1 178.4±3.0

[0073] Figure 1SEM images of 2,2'-(m-phenyl)-5,5'-bibenzimidazole (PBI) prepared in the control example and the brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane (PBI-BC-X) prepared in the example, wherein Figure (a) is a cross-sectional SEM image of PBI, Figure (b) is a cross-sectional SEM image of PBI-BC-10%, Figure (c) is a cross-sectional SEM image of PBI-BC-20%, Figure (d) is a cross-sectional SEM image of PBI-BC-30%, and Figure (e) is a cross-sectional SEM image of PBI Figure (f) is the surface SEM image of PBI-BC-10%, Figure (g) is the surface SEM image of PBI-BC-20%, and Figure (h) is the surface SEM image of PBI-BC-30%; in the cross-sectional view, each membrane shows a certain degree of roughness, and with the increase of Br-CD content, the roughness becomes more obvious, which is beneficial to improving the absorption content of PA and promoting the enhancement of electrical conductivity; in the plan view, each membrane is smooth, dense and defect-free, and can be used as a good membrane material.

[0074] Figure 2 Infrared spectra of 2,2'-(m-phenyl)-5,5'-bibenzimidazole (PBI) prepared in the control example and the brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane (PBI-BC-X) prepared in the example; 804 cm -1 The peak corresponding to the CN stretching vibration of the polybenzimidazole ring is 1450 cm -1 The characteristic absorption peak at 1623 cm -1 The peak at 656cm is the C=N stretching vibration peak on the polybenzimidazole ring. -1 The peak at is the stretching vibration peak of the bromine bond. It is observed that the peak intensity increases with the increase of Br-CD content, indicating that multifunctional quaternary ammonium salts in different proportions have been successfully introduced into PBI, indicating the successful preparation of the composite membrane PBI-BC-X.

[0075] Figure 3 The acid loss diagram of 2,2'-(m-phenyl)-5,5'-bibenzimidazole (PBI) prepared as a control example and the brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane (PBI-BC-X) prepared in the example; compared with the original PBI membrane, the composite membrane has a better retention capacity for PA, which is attributed to the fact that the introduced Br-CD can bind more PA and promote acid retention. The effect of PBI-BC-20% is better than that of PBI-BC-25% and PBI-BC-30% with higher Br-CD content, which is because more Br-CD aggregates in the membrane, hindering the effective absorption of PA. This test result echoes the acid absorption test results.

[0076] Figure 4The proton conductivity diagram of 2,2'-(m-phenyl)-5,5'-bibenzimidazole (PBI) prepared as a control example and the brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane (PBI-BC-X) prepared in the example. The proton conductivity of the membrane was tested at 100℃~180℃. The results showed that with the increase of temperature, the proton conductivity of the composite membrane also increased, and the conductivity of the composite membrane was better than that of the original PBI membrane. The improvement of the conductivity of the composite membrane is attributed to the presence of more quaternary ammonium salts in the membrane, which is beneficial for the absorption and retention of PA, and PA provides a channel for proton transfer. Among the composite membranes, the best conductivity is PBO-BC-20%, and the conductivity is 127mS / cm at 180℃. The test results are consistent with the results of acid absorption capacity, ADL, swelling volume test, and acid loss test.

[0077] In summary, the product of the present invention prepares a PBI composite membrane with multi-functional quaternary ammonium salts. The quaternary ammonium salts can be combined with PA through ionic bonds, providing more proton hopping sites, and improving the ability of the high-temperature proton exchange membrane in absorbing and retaining PA; at the same time, Br-CD has the cavity structure of β-cyclodextrin, which can fix more PA and promote the improvement of conductivity.

Claims

1. A method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane, characterized in that The method is specifically carried out in the following steps: Step 1: Preparation of 2,2'-(m-phenyl)-5,5'-bibenzimidazole Dissolve diaminobenzidine and isophthalic acid in polyphosphoric acid, control the temperature between 120 and 140°C, and stir mechanically under nitrogen protection; after complete dissolution, raise the temperature to 200°C, and continue the reaction until the product becomes viscous; The viscous product is poured into a sodium bicarbonate solution, washed repeatedly until neutral, and dried to obtain 2,2'-(m-phenyl)-5,5'-bibenzimidazole; Step 2: Preparation of brominated β-cyclodextrin Dissolve β-cyclodextrin and N-bromosuccinimide in NN-dimethylacetamide, add triphenylphosphine as a polymer initiator, and react for 20 to 24 hours at a temperature of 80°C under nitrogen protection; then pour into methanol and stir to obtain a precipitate, then wash the precipitate with methanol aqueous solution until the washing liquid is colorless; then dry to obtain brominated β-cyclodextrin; Step 3: Preparation of phosphoric acid / bromo-β-cyclodextrin / PBI composite membrane The 2,2'-(m-phenyl)-5,5'-bibenzimidazole obtained in step 1 and the brominated β-cyclodextrin obtained in step 2 are dissolved in NN-dimethylacetamide, and stirred for 24 hours at a temperature of 60-80° C. under nitrogen protection, and then poured onto a horizontal glass plate, cast into a film, and dried to obtain a brominated β-cyclodextrin and PBI composite film; The brominated β-cyclodextrin and PBI composite membrane is immersed in a trimethylamine solution to carry out a quaternization reaction, and then the surface of the composite membrane is washed with distilled water, dried and immersed in a phosphoric acid solution with a mass concentration of 85% for 48 hours to obtain the brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane.

2. The method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane according to claim 1, characterized in that The mass ratio of diaminobenzidine, isophthalic acid and polyphosphoric acid in step 1 is 5.6:4.3:

80.

3. The method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane according to claim 1, characterized in that The mechanical stirring speed in step 1 is 200-300 rpm.

4. The method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane according to claim 1, characterized in that The concentration of the sodium bicarbonate solution in step 1 is 2 mol / L.

5. The method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane according to claim 1, characterized in that In step 2, the molar ratio of β-cyclodextrin to N-bromosuccinimide is 1:14, and the amount of triphenylphosphine used is 1.5 g.

6. The method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane according to claim 1, characterized in that Step 2: Control the stirring speed to 500-600 rpm.

7. The method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane according to claim 1, characterized in that The volume ratio of distilled water to methanol in the methanol-water solution in step 2 is 1:

1.

8. The method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane according to claim 1, characterized in that In step 3, the mass ratio of 2,2'-(m-phenyl)-5,5'-bibenzimidazole, brominated β-cyclodextrin and NN-dimethylacetamide is 1:(0.05-0.3):

25.

9. The method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane according to claim 1, characterized in that The thickness of the composite film in step 3 is 80-100 μm.

10. The method for preparing a brominated β-cyclodextrin and polybenzimidazole composite proton exchange membrane according to claim 1, characterized in that Step 3: Control the quaternization reaction time to be 48 to 72 hours.

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