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 (O₃) that was formed in the SDR as the oxidant precursor. With an increase in the amount of water vapour in air, the benzene conversion was decreased, due to the deactivation of high-energy electrons, the diminished formation of O₃ in SDR, and decreased activity of MnO₂ for the benzene oxidation with O₃. 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 O₃. 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.