High Efficient Decomposition of Environment-Polluting Gases in a Specific Reaction System

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Our previous studies have revealed that Ar plasma could be generated from SiC ceramics under atmospheric pressure upon irradiation of microwave and this microwave-induced (MI) Ar plasma offered several advantages in decomposing trichlorotrifluoroethane (CFC113). The present study was directed to improving the MI Ar plasma processing.When LaィイD20.8ィエD2SrィイD20.2ィエD2MnOィイD23ィエD2 was used as an alternative trigger for MI Ar plasma generation, similar decomposition behavior of CFC113 could be obtained. Thus, we could confirm again that CFC113 could be decomposed more satisfactorily by MI Ar plasma, accompanied by low energy consumption and low concentration of partial decomposition products, than by its direct thermal decomposition or simple catalytic decomposition with LaィイD20.8ィエD2SrィイD20.2ィエD2MnOィイD23ィエD2.Cooperative decomposition of CFC113 was also conducted by the MI Ar plasma generated from SiC ceramics and LaィイD20.8ィエD2SrィイD20.2ィエD2MnOィイD23ィエD2 catalyst placed in the downstream of th … More e plasma zone. In comparison with the decomposition without the catalyst, the concentration of CClィイD22ィエD2FィイD22ィエD2 as a partial decomposition product in the effluent gas was approximately doubled in the microwave power range of 60-80 W, but the total concentration of partial decomposition products was decreased satisfactory above the microwave power of 100 W. Thus, it was revealed that CFC113 could be decomposed more efficiently by the cooperative decomposition. However, the decomposition efficiency decreased gradually with time, probably due to the degradation of the catalyst by HCl and/or HF produced from CFC113 in the plasma. It was suggested that the long-term stability of this reaction system could be improved by setting the catalyst (heated at 550℃) in the downstream of the plasma zone and then by removing both HCl and HF form the effluent gas before reaching the catalyst zone.The shape of the plasma generated from SiC ceramics was a streak, and therefore it is suggested that poor radical and/or ion bombardment to CFC113 is responsible for unsatisfactory decomposition efficiency of the plasma alone. In the next step, therefore, the effect of the successive double plasma reactors, namely, the usefulness of an additional plasma reactor for decomposing partial decomposition products produced by the first plasma reactor has been investigated. As a result, further improvement in decomposition efficiency could be realized.Based on the results obtained, future investigations should be directed to the development of the ceramic form of a plasma trigger with three-dimensional open-micropore structure. The generation of Ar plasma inside the micropores makes low-cost, high efficient and continuous decomposition of environment-polluting gases possible under atmospheric pressure. Less