Synergetic Effect Between Plasma and UV for Toluene Conversion in Integrated Combined Plasma Photolysis Reactor with KrCl/KrBr/XeCl/Xe-2 Excilamp

摘要

An integrated combined plasma photolysis (CPP) reactor, which simultaneously produced dielectric barrier discharge (DBD) plasma and excimer UV radiation, was employed to decompose toluene gas. The study of toluene degradation by the separate processes, realized in three reactors (DBD, UV, and CPP), showed that toluene conversion by CPP was higher than the sum of the conversions for DBD and UV alone, indicating a synergetic effect in CPP between plasma and UV occurred. The degradation performance of gaseous toluene in CPP using different excimer UV sources (XeCl*, KrCl*, KrBr*, Xe-2*) was compared, and a regression analysis showed that CPP can enhance toluene conversion by about 50% and energy yield by 90%. Radiant spectra and efficiency of excimer UV sources were recorded in detail. Further, it was observed that carbon balance and CO2 selectivity were greatly increased in the CPP in comparison with DBD, accompanied by NO, CO, and O-3 being effectively suppressed. Intermediate products in effluent gas using CPP treatment for toluene included formic acid, acetic acid, benzene, benzaldehyde, phenol, benzoic acid, etc. Based on by-product analysis and excimer UV radiant efficiency, we concluded that toluene degradation is due to electron impact dissociation, excited species and free radical reaction from background gases dissociation, direct photolysis by excimer UV, and synergy between plasma and UV. Among these, electron impact, free radical reaction, and plasma-UV synergy played critical roles on toluene conversion, while direct UV contribution seems to be minor.