Efficiency and reactivity pattern of ceria-based noble metal and transition metal-oxide catalysts in the wet air oxidation of phenol

The activity-stability pattern of ceria-based noble metal (Pt/CeO2) and transition metal-oxide (MnCeOx) catalysts in the wet air oxidation of phenol (CWAO) at different catalyst-to-phenol weight ratio (R, 1-5) was comparatively probed using a stirred batch reactor with continuous oxygen feed (T-R, 150 degrees C; Po-2. 0.9 MPa). Both Pt/CeO2 and MnCeOx systems drive a surface dual-site Langmuir-Hinshelwood (L-H) reaction path enabling higher efficiency, different reaction kinetics and "phenol-total organic carbon" conversion relationships in comparison to homogeneous CWAO catalysts [1]. A simplified reaction scheme based on consecutive adsorption and mineralization steps and the relative kinetic analysis show that the former determines the rate of phenol and TOC removal, while the latter controls the selectivity and rate of catalyst fouling. The MnCeOx system ensures a fast and complete phenol conversion and a TOC removal higher than 80% at any R, while improved adsorption and mineralization functionalities explain a higher resistance to deactivation by fouling than Pt/CeO2 system. (C) 2011 Elsevier B.V. All rights reserved.