Plasma oxidation of methanol (CH3OH) in oxygen and nitrogen was investigated using two dielectric barrier discharge (DBD) reactors with or without Al2O3 as a catalyst and using a DC circle-to-plate (CTP) reactor. An AC power supply was used for the DBD reactors to generate corona discharges. A DC power supply, a 20-M Omega resistor, and a 100-pF capacitor were used to yield pulselike discharges. CH3OH was oxidized to formaldehyde (HCHO), carbon monoxide (CO), and carbon dioxide (CO2). HCHO was the main product when using DBD reactors and without Al2O3. CO was the main product when using the DBD reactor with Al2O3 and CTP reactor. Al2O3 could inhibit CH3OH further oxidation. The energy efficiency of the DBD reactors decreased with increasing power input and power density. The energy efficiency of the CTP reactor peaked with 7 g CH3OH/kWh that was three times as high as that with the DBD reactors at the same power input. Furthermore, the power density of the CTP reactor was higher than that of the DBD reactors, implying that the CTP reactor could be used for CH3OH oxidation with a small discharge space volume. (c) 2005 American Institute of Chemical Engineers.