Present paper describes the influence of the incorporation of alkali metal cations (AM = Li, Na, K, Cs; and an AM/V ratio of 0.04) and Na-content (Na/V ratio of 0.02-0.30) in alkali metal promoted V2O5 catalyst on both the catalyst structure and the catalytic performance in H2S partial oxidation reactions. The catalytic activity depends on the alkali metal and the amount of alkali metal added, although Na-containing catalysts seem to be the more active ones. However, selectivity to sulphur higher than 98% is achieved in the main of catalysts when working at reaction temperature lower than 220 degrees C. According to the characterization results of used catalysts, V4O9 is selectively formed during the catalytic tests on catalysts presenting V2O5 crystallites. In catalysts with Na/V ratios higher than 0.04, V4O9 and Na0.33V2O5 are observed, the presence of Na0.33V2O5 increasing when increasing the Na/V ratio. Accordingly, V4O9 and Na0.33V2O5 can be proposed as the active and selective crystalline phase in Na-containing catalysts. The role of the presence of V4+-O-V5+ pairs in partial oxidation of H2S is also discussed. (c) 2012 Elsevier B.V. All rights reserved.