The catalytic activity of Pt on alumina catalysts, with and without MnOx incorporated to the catalyst formulation, for CO oxidation in H-2-free as well as in H-2-rich stream (PROX) has been studied in the temperature range of 25-250 degrees C. The effect of catalyst preparation (by successive impregnation or by co-impregnation of Mn and Pt) and Mn content in the catalyst performance has been studied. A low Mn content (2 wt.%) has been found not to improve the catalyst activity compared to the base catalyst. However, catalysts prepared by successive impregnation with 8 and 15 wt.% Mn have shown a lower operation temperature for maximum CO conversion than the base catalyst with an enhanced catalyst activity at low temperatures with respect to Pt/Al2O3. A maximum CO conversion of 89.8%, with selectivity of 44.9% and CO yield of 40.3% could be reached over a catalyst with 15 wt.% Mn operating at 139 degrees C and lambda = 2. The effect of the presence of 5 vol.% CO2 and 5 vol.% H2O in the feedstream on catalysts performance has also been studied and discussed. The presence Of CO2 in the feedstream enhances the catalytic performance of all the studied catalysts at high temperature, whereas the presence of steam inhibits catalysts with higher MnOx content. (c) 2006 Elsevier B.V. All rights reserved.