Performance and Pathways of Toluene Degradation over Co/13X by Different Processes Based on Nonthermal Plasma

Performance and pathways of toluene degradation by three types of processes based on nonthermal plasma, including nonthermal plasma alone (NTP), plasma catalytic (PC), and adsorption-plasma catalytic processes (APC), were compared, which took into account toluene removal efficiency (eta(r)), mineralization efficiency (eta(M)), CO2 selectivity (eta(C)), and energy efficiency (eta(E)). Co/13X is a catalyst prepared by the impregnation method. NTP combined with the catalyst exhibited good oxidation performance. Also, eta(M) and eta(C) were further improved, and eta(E) was greatly reduced by the APC process. The deactivation of the catalyst was the main drawback for the PC and APC processes, and it was detected by CO2-TPD, FTIR, BET, and element analysis. The APC process was more suitable for low-concentrations VOC. The eta(r), eta(M), and eta(C) were enhanced with discharge power and residence time increased. Byproducts of toluene degradation were different between NTP and that combined with catalyst. Toluene degradation in NTP was mainly caused by energetic electrons and reactive species; methyl and an aromatic ring were first destructed and subsequently oxidized. As for NTP combined with the catalyst, toluene was first oxidized and then broken, which mainly depended on active oxygen species.