The catalytic wet air oxidation (CWAO) of butyric and maleic acids was carried out in a batch reactor operated at 333 K and at atmospheric pressure. Noble metals (platinum, palladium and ruthenium) supported on TiO2 were used as catalysts as well as commercial Pt/Al2O3, Maleic and butyric acids could be oxidized only into intermediates on the commercial Pt/Al2O3 catalysts with a conversion of 11% and 7.9%, respectively. Total oxidation to CO2 ranged from 0.0% to 0.35% for butyric acid (BA) and from 0.4% to 1.7% for maleic acid (MA). Intermediate products were oxalic and formic acids. In BA oxidation, acetic acid was also detected. (C) 2008 Elsevier B.V. All rights reserved.