Plasma-catalytic removal of a low concentration of acetone in humid conditions

A coaxial dielectric barrier discharge (DBD) plasma reactor has been developed for plasma-catalytic removal of low concentration acetone over MOx/gamma-Al2O3 (M=Mn, Co, or Cu) catalysts. The effect of relative humidity of air (RH) on the discharge characteristics, acetone removal efficiency, CO2 selectivity, and byproduct formation with and without catalyst has been investigated. The results show that increasing the RH leads to a decrease of the specific energy density (SED) of the DBD, while packing gamma-Al2O3 supported metal oxide catalysts into the discharge gap enhances the SED of the discharge. The maximum acetone removal of 75.3% is achieved at an optimum RH of 10% using CoOx/gamma-Al2O3 beyond which the removal efficiency of acetone decreases with the increase of the RH. Higher RH inhibits the formation of energetic electrons while water can be adsorbed onto the catalyst surface and block active sites on the catalyst surface. It is found that increasing the air humidity enhances both CO2 selectivity and carbon balance, but decreases the formation of ozone. However, the formation of NOx slightly increases with increasing the gas humidity. In addition, the presence of these catalysts in the discharge significantly decreases the formation of unwanted byproducts (O-3 and NOx) and promotes the deep oxidation of acetone towards CO2 with an increased carbon balance.