Plasma oxidation of benzene (C6H6) in oxygen and nitrogen was investigated using a dielectric barrier discharge (DBD) reactor with or without MnO2 or TiO2 at atmospheric pressure and without external heating except plasma heating. An alternative current power supply was used to generate corona discharges for the plasma oxidation. The energy density was controlled under 200J/L to keep an increase in gas temperature less than 167 K. C6H6 was oxidized to carbon monoxide (CO) and dioxide (CO2). Typically, the energy efficiency at an energy density of 92 J/L was about 0.052, 0.039, and 0.024 mol/kWh with MnO2, TiO2, and without MnO2 and TiO2, respectively. Benzene oxidation mechanism was mentioned. A comparison on energy efficiency as a function of initial concentration of hydrocarbons, inorganic sulphur compounds, and chloro (fluoro and bromo) carbons was given. (c) 2006 Elsevier B.V. All rights reserved.