Performance evaluation of a hybrid system comprising silent discharge plasma and manganese oxide catalysts for benzene decomposition

A hybrid system comprising a silent discharge plasma reactor (SDR) and manganese oxide (MnO2) catalyst was used for the decomposition of benzene in air. The benzene conversion was greatly enhanced by combining MnO2 with the SDR in the latter part. The MnO2 catalyst decomposed benzene by using ozone (O-3) that was formed in the SDR as the oxidant precursor. With an increase in the amount of water vapor in air, the benzene conversion was decreased, due to the deactivation of high-energy electrons, the diminished formation of O-3 in SDR, and decreased activity of MnO2 for the benzene oxidation with O-3. The only products of the reaction were CO2 and CO. The carbon mass balance was not perfect due to the deposition of intermediates on MnO2 during the reaction. The intermediates were subsequently decomposed to CO2 and CO by MnO2 in the presence of O-3. In dry air, the selectivities to CO2 and CO were 70% and 30%, respectively, and were almost independent of specific energy density. The CO2 selectivity was improved to 90% by humidifying the background air.