Effective removal of toluene at near room temperature using cyclic adsorption-oxidation operation in alternative fixed-bed plasma-catalytic reactor

Abstract

This work investigated the removal of toluene using cyclic adsorption/oxidation operation in a fixed-bed dielectric barrier discharge (DBD) plasma-catalytic reactor containing Pd/ZSM-5 catalyst. The modification of ZSM-5 with Pd catalyst (2 wt %) substantially improved the adsorption capability for toluene. The catalyst adsorbing toluene was readily regenerated during the plasma-catalytic oxidation step. The synergistic effect of the catalyst promoted the toluene oxidation process as well as improved the selectivity towards CO2. As a method of reducing the energy in generating plasma, two cases (when the ground electrode was exposed to the external air and when the ground electrode was immersed in insulating oil) were compared. No micro-discharge occurred outside the ground electrode surface after oil jacketing, which prevented NOx and ozone from forming, improved energy efficiency, and promoted CO2 selectivity to 91%. The energy consumption with the oil insulation was 14.5 J/L, while that without it was 58.0 J/L. The catalyst was characterized using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).