Oxidation of SO2-SO3 has been studied experimentally in laboratory flow reactors. The homogeneous oxidation by O-2 was characterized in the temperature range 1023-1323 K at semi-dry and moist conditions. The reaction was found to be very slow, in agreement with results from literature. The experimental data compared well with modeling predictions using a recently published reaction mechanism for gas-phase SO2 oxidation. The ability of quartz, alumina and iron oxide to catalyze the SO2 oxidation was studied in the temperature range 873-1273 K. Quartz was found to be inert to SO2 oxidation, while alumina promoted the oxidation. Iron oxide was found to be a strong oxidation catalyst, in agreement with results from literature. (c) 2007 Elsevier Ltd. All rights reserved.