Toluene and 4-chlorotoluene decomposition in air mixture in electron beam generated non-thermal plasma reactor and their by-products identification

Degradation of toluene and 4-chlorotoluene in air mixture was studied by using electron beam generated plasma reactor. It was found that removal efficiency of toluene and 4-chlorotoluene was influenced by radiation dose, i.e. energy deposited in the gas, and their initial concentration. The by-products formed as a result of degradation of toluene or 4-chlorotoluene under electron beam radiation were identified. The mechanism of their degradation was proposed. •OH radicals play a main role in degradation process of toluene or 4-chlorotoluene. For degradation of 4-chlorotoluene, reaction of •OH radicals with 4-chlorotoluene by hydrogen abstraction from the methyl group, followed by peroxyl radical formation, is a main reaction pathway. 4-chlorobenzaldehyde and 4-chlorobenzyl alcohol are formed according to the Russel-mechanism. For degradation of toluene, reaction pathway of •OH radicals with toluene by hydrogen abstraction from the methyl group plays an important role. Besides it, there are the other two important reaction pathways. One is reaction of •OH radical addition and H atom abstraction from benzene ring; the other is •OH-adduct reaction. Cresol, nitrotoluene and ring cleavage products are formed from these two reaction pathways. Since Cl is more electronegative than H, H atom abstraction from –CH3 by •OH radicals from toluene (HC6H4CH3) is easier than from 4-chlorotoluene (ClC6H4CH3), this may explain why the decomposition efficiency of toluene is slightly higher than that of 4-chlorotoluene in an air mixture under EB radiation.