Using non-thermal plasma for decomposition of toluene adsorbed on γ-Al2O3 and ZSM-5: Configuration and optimization of a double dielectric barrier discharge reactor

A novel hybrid system was established to degrade adsorbed toluene efficiently. A double dielectric barrier discharge (DDBD) reactor was filled with two common adsorbents, gamma-Al2O3 and ZSM-5, in various combinations. Packing material, high-voltage electrode structure, and gas-flow mode were investigated to optimize this reactor. The reactor packed with a mixture of gamma-Al2O3 and ZSM-5 provided a mineralization rate 6.1% to -14.1% greater than one using a single material. Specifically, the highest mineralization rate was obtained in a DDBD reactor packed with gamma-Al2O3 in the inner tube and ZSM-5 in the outer tube. Using the optimal combination of packing material, two high-voltage electrodes were compared. A higher mineralization rate was observed in the reactor with a rod electrode (63.3%) than in one equipped with a coil electrode (53.7%), The total amounts of O-3 and N2O generated were much less in the reactor with a rod electrode. The effect of gas-flow mode on toluene decomposition was investigated and the result showed that mode 1 (with the gas flowing from the inner tube into the outer tube during both adsorption and discharge phases) could not only improve the degradation of toluene, but could also suppress the generation of O-3 and N2O. A possible mechanism for toluene decomposition in the packed-bed DDBD reactor was proposed based on the analysis of organic intermediates remaining in the adsorbents.