Degradation of benzene by bipolar pulsed series surface/packed-bed discharge reactor over MnO2-TiO2/zeolite catalyst

In the present study, plasma-catalytic process was used to degrade benzene using the bipolar pulsed series surface/packed-bed discharge (SSPBD) reactor over MnO2-TiO2/zeolite catalyst at room temperature. The SSPBD reactor showed higher benzene degradation efficiency and CO2 selectivity than the traditional packed-bed discharge (PBD) and surface discharge (SD) reactor at the same discharge power. To increase the benzene degradation efficiency and decrease the energy loss, electrical parameters including the pulsed repetitive frequency (f) and pulse forming capacitances (Cp) were optimized. f = 50 Hz and Cp = 1 nF were considered to be the best choices. In comparison to the plasma-only process, the existence of MnO2-TiO2/zeolite and TiO2/zeolite catalysts significantly enhanced the benzene degradation efficiency and CO2 selectivity. Meanwhile, the highest benzene degradation efficiency of 83.7% and CO2 selectivity of 68.1% were obtained by the MnO2-TiO2/zeolite at 10.33 W, which were 4.9% and 5.6% higher than TiO2/zeolite. It could be attributed to the incorporation of Mn into TiO2 catalyst, which was beneficial to the charge transferring between Ti4+ and Mn4+ on the surface of MnO2-TiO2/zeolite catalyst and facilitated the generation of hydroxyl radicals. MnO2-TiO2/zeolite also exhibited better performance in ozone suppression than TiO2/zeolite, which was mainly due to the strong ozone decomposing ability of MnO2. In addition, intermediate products (such as CO, HCOOH, N2O, etc.) were significantly inhibited by the MnO2-TiO2/zeolite catalyst based on the result of Fourier transform infrared spectra (FTIR).