In situ X-ray absorption fine structure spectroscopic studies were carried out to investigate the structural changes in manganese oxides supported on alumina in the catalytic decomposition of ozone at room temperature. In the ozone decomposition with water vapor, Mn atom was oxidized to higher oxidation state with the coordination of water to Mn site, which was caused by the cleavage of Mn-O-Al bond. The used catalyst was regenerated by the heat treatment in an 02 flow at 723 K. (c) 2005 Elsevier B.V. All rights reserved.