Synthesis, characterization and application of polypyrrole/zeolite composites
Yu, Kai (2017-06-02)
Yu, Kai
Åbo Akademi - Åbo Akademi University
02.06.2017
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https://urn.fi/URN:ISBN:978-952-12-3539-9
https://urn.fi/URN:ISBN:978-952-12-3539-9
Tiivistelmä
Hybrid materials consisting of microporous aluminosilicate zeolites and the conducting polymer polypyrrole (PPy) were synthesized and characterized. The PPy/zeolite composites exhibit both the mechanical and chemical properties of the zeolites as well as the unique electrical and electrochemical properties of PPy, which are intended for new types of catalysts and sensors.
The acid groups in the zeolites were expected to influence the properties of the PPy/zeolite composites. Therefore, the acidity of the selected zeolites was determined prior to synthesis of the composites. Because the synthetic reaction takes place in the aqueous phase, potentiometric acid-base titration was used here instead of the common gas-phase techniques. Analysis of the titration data was based on the Gran method. Various acid groups were found in the studied zeolites. Both the protonation constants and the concentrations of these acid groups were determined. The results also show that the potentiometric titration is a reliable and suitable method for characterizing the acidic properties of zeolites that are used in aqueous-phase catalytic reactions.
PPy/zeolite composites were first synthesized by chemical polymerization of pyrrole in presence of zeolites using FeCl3 as the oxidizing agent. The protonated form of Beta zeolites with various SiO2/Al2O3 ratios were used as the host for PPy in this study. Both the anionic groups in the zeolite structures and the chloride ions from the FeCl3 oxidant functioned as the counter ion during the polymerization. Deposition of PPy inside the channels of the zeolite decreased the surface area of the zeolite. Some PPy/zeolite composites showed higher conductivity, compared with PPy(Cl-), which may be due to an increased alignment of the polymer chains in the PPy/zeolite composites.
Electropolymerization of pyrrole in presence of zeolites was performed by using the method of constant potential, resulting in electrodeposition of PPy/zeolite composites on the electrode surface. The protonated forms of Beta zeolites and Y zeolites were used in this study. The results indicate that electropolymerization of pyrrole took place mainly on the outer surfaces of the zeolite crystals. PPy was observed on the crystal surface and also in the channels of the zeolites. The oxidized cationic PPy was charge-balanced by the anionic groups in the zeolite framework, and therefore the zeolite influenced the electrochemical behavior of PPy.
The electrodeposited PPy/zeolite composites were tested as solid contact in an ion-selective electrode (ISE). For this purpose, the protonated forms of ZSM-5 zeolites were used as the host for PPy. The anionic groups in these zeolites functioned as the counter ions for PPy during the polymerization. The results indicated that microporous zeolites containing a high concentration of anionic groups are proper candidates to form composites with conducting polymers in order to generate a new type of solid contact for ion-selective electrodes.
The acid groups in the zeolites were expected to influence the properties of the PPy/zeolite composites. Therefore, the acidity of the selected zeolites was determined prior to synthesis of the composites. Because the synthetic reaction takes place in the aqueous phase, potentiometric acid-base titration was used here instead of the common gas-phase techniques. Analysis of the titration data was based on the Gran method. Various acid groups were found in the studied zeolites. Both the protonation constants and the concentrations of these acid groups were determined. The results also show that the potentiometric titration is a reliable and suitable method for characterizing the acidic properties of zeolites that are used in aqueous-phase catalytic reactions.
PPy/zeolite composites were first synthesized by chemical polymerization of pyrrole in presence of zeolites using FeCl3 as the oxidizing agent. The protonated form of Beta zeolites with various SiO2/Al2O3 ratios were used as the host for PPy in this study. Both the anionic groups in the zeolite structures and the chloride ions from the FeCl3 oxidant functioned as the counter ion during the polymerization. Deposition of PPy inside the channels of the zeolite decreased the surface area of the zeolite. Some PPy/zeolite composites showed higher conductivity, compared with PPy(Cl-), which may be due to an increased alignment of the polymer chains in the PPy/zeolite composites.
Electropolymerization of pyrrole in presence of zeolites was performed by using the method of constant potential, resulting in electrodeposition of PPy/zeolite composites on the electrode surface. The protonated forms of Beta zeolites and Y zeolites were used in this study. The results indicate that electropolymerization of pyrrole took place mainly on the outer surfaces of the zeolite crystals. PPy was observed on the crystal surface and also in the channels of the zeolites. The oxidized cationic PPy was charge-balanced by the anionic groups in the zeolite framework, and therefore the zeolite influenced the electrochemical behavior of PPy.
The electrodeposited PPy/zeolite composites were tested as solid contact in an ion-selective electrode (ISE). For this purpose, the protonated forms of ZSM-5 zeolites were used as the host for PPy. The anionic groups in these zeolites functioned as the counter ions for PPy during the polymerization. The results indicated that microporous zeolites containing a high concentration of anionic groups are proper candidates to form composites with conducting polymers in order to generate a new type of solid contact for ion-selective electrodes.