The Roles of Various Plasma Active Species in Toluene Degradation by Non-thermal Plasma and Plasma Catalysis

Abstract

Investigating the roles of plasma active species in plasma chemical reaction process can improve understanding of the mechanism of volatile organic compounds degradation by plasma. In this work, different experimental processes were designed to distinguish the contributions of various active species of plasma in the decomposition of toluene by a dielectric barrier discharge plasma with or without the CoMnOx/TiO2 catalyst. The removal efficiency of toluene, selectivity of COx (CO2 and CO), and byproducts were detected. The results showed that within the post-plasma zone, toluene could be oxidized to organic intermediates but not completely oxidized to COx by the long-lived active species of O2 plasma; furthermore, O3 alone could not degrade toluene in the gas phase, and the active species generated by N2 discharge could not degrade toluene. In the plasma area, toluene could be decomposed by both the short- and long-lived active species, and could be oxidized to COx by the short-lived active species. The introduction of CoMnOx/TiO2 catalyst, whether within or after the plasma zone, could efficiently decompose O3 and greatly improve the utilization of the active species, thus increasing the removal efficiency of toluene and the selectivity of COx.