1. Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), Dalian University of Technology, Dalian 116024, China2. School of Electrical Engineering, Dalian University of Technology, Dalian 116024, China3. School of Environmental Science & Technology, Dalian University of Technology, Dalian 116024, China
Abstract:
In this study, post plasma-catalysis degradation of mixed volatile organic compounds (benzene, toluene, and xylene) has been performed in a hybrid surface/packed-bed discharge plasma reactor with Ag-Ce/g-Al2O3 catalyst at room temperature. The effect of relative air humidity on mixed VOCs degradation has also been investigated in both plasma-only and PPC systems. In comparison to the plasma-only system, a significant improvement can be observed in the degradation performance of mixed VOCs in PPC system with Ag-Ce/γ-Al2O3 catalyst. In PPC system, 68% benzene, 89% toluene, and 94% xylene were degraded at 800 J·L–1, respectively, which were 25%, 11%, and 9% higher than those in plasma-only system. This result can be attributed to the high catalytic activity of Ag-Ce/γ-Al2O3 catalyst to effectively decompose O3 and lead to generating more reactive species which are capable of destructing the VOCs molecules completely. Moreover, the presence of Ag-Ce/γ-Al2O3 catalyst in plasma significantly decreased the emission of discharge byproducts (NOx and O3) and promoted the mineralization of mixed VOCs towards CO2. Adding a small amount of water vapor into PPC system enhanced the degradation efficiencies of mixed VOCs, however, further increasing water vapor had a negative impact on the degradation efficiencies, which was primarily attributed to the quenching of energetic electrons by water vapor in plasma and the competitive adsorption of water vapor on the catalyst surface. Meanwhile, the catalysts before and after discharge were characterized by the Brunauer-Emment-Teller and X-ray photoelectron spectroscopy.
