Post plasma-catalysis for VOCs degradation over different phase structure MnO2 catalysts

MnO2 catalysts with different phase structure were supported on Al2O3 pellets and applied in a post plasma-catalysis system for volatile organic compounds (VOCs) degradation. The introduction of MnO2/Al2O3 catalysts improved the acetaldehyde removal efficiency and the carbon dioxide selectivity significantly, while the formation of ozone and NOx in plasma was inhibited. Among different phase structure MnO2 catalysts, alpha-MnO2 was superior to beta-MnO2 and gamma-MnO2 with respect to the degradation efficiency, the carbon dioxide selectivity and ozone suppression. The excellent activity may be ascribed to OH groups, VOCs adsorption capacity and mobility of oxygen. Compared with acetaldehyde, the degradation of benzene by plasma-catalysis had lower removal efficiency, less production of NOx and more residual ozone. On the other hand, amine and nitromethane were observed by on-line fast FTIR in the acetaldehyde degradation by plasma. It is speculated that some nitrogen-containing intermediates are oxidized into NOx while acetaldehyde also contributes its oxygen to the formation of NOx in non-thermal plasma. (C) 2013 Elsevier B.V. All rights reserved.