Tubular Membrane-Like Catalysts for the Oxidative Decomposition of Low-Concentrated Toluene in Air by Periodic Short-Term Plasma Discharge

Abstract

A porous membrane-like alumina (MA) tube was employed as a catalyst to improve the energy efficiency of the oxidative decomposition of low-concentrated toluene in air by periodic short-term plasma discharge. The raw MA tube prepared by anodizing an aluminum tube had a relatively small surface area and toluene adsorption capacity, but they were remarkably increased by silica coating. Introducing the silica-coated catalyst into the dielectric-barrier discharge plasma generated for 5 s every 1 min resulted in a 3.6-fold increase in the rate of the toluene decomposition in a closed-circulating reaction system, suggesting that the toluene molecules were condensed by adsorption onto the catalyst surface and then decomposed by plasma. The energy efficiency was 14 g kWh−1, which was 9.3 times larger than that for the non-catalytic oxidation of toluene by continuous plasma irradiation. Palladium loading onto the catalyst slightly degraded the decomposition rate, but it suppressed the formation of organic by-products. These results clearly indicate the effectiveness of using a membrane-like catalyst in periodically-irradiated plasma reactors for VOC decompositions.