Water pollution abatement by catalytic wet air oxidation in a trickle bed reactor

Catalytic wet air oxidation of an aqueous phenol solution was carried out i n a trickle bed reactor at mild conditions of temperature (120-160 degrees C) and oxygen partial pressure (0.6-1.2 MPa). Tests were performed at space times up to 1 h. A commercially available copper oxide supported over gamm a-alumina was used as catalyst. The results show that the phenol conversion , the chemical oxygen demand (COD) reduction and the distribution of oxidat ion products are considerably affected by the temperature, whereas the oxyg en partial pressure only has minor influence. The process exhibits high sel ectivity towards the production of carbon dioxide. Oxalic, acetic and formi c acids were found to be the main partial oxidation products but also trace s of maleic and malonic acids and quinone-like products, such as dihydric p henols and benzoquinones, were detected. First order with respect to the ph enol concentration and one half order with respect to the oxygen partial pr essure was found for both phenol disappearance and COD reduction. The appar ent activation energy was calculated to be 85 kJ/mol for phenol oxidation a nd 76 kJ/mol for COD abatement. These values favourably compare with those cited in the literature for intrinsic kinetics, which indicates minimal mas s transfer limitations in the trickle bed reacting system used in this stud y. (C) 1999 Elsevier Science B.V. All rights reserved.