Bimetallic catalysts for continuous catalytic wet air oxidation of phenol

Catalytic wet oxidation has proved to be effective at eliminating hazardous organic compounds, such as phenol, from waste waters. However, the lack of active long-life oxidation catalysts which can perform in aqueous phase is its main drawback. This study explores the ability of bimetallic supported catalysts to oxidize aqueous phenol solutions using air as oxidant. Combin ations of 2% of CoO, Fe2O3, MnO or ZnO with 10% CuO were supported on gamma -alumina by pore filling, calcined and later tested. The oxidation was carr ied out in a packed bed reactor operating in trickle flow regime at 140 deg rees C and 900 kPa of oxygen partial pressure. Lifetime tests were conducte d for 8 days. The pH of the feed solution was also varied. The results show that all the catalysts tested undergo severe deactivation during the first 2 days of operation. Later, the catalysts present steady activity until th e end of the test. The highest residual phenol conversion was obtained for the ZnO-CuO, which was significantly higher than that obtained with the 10% CuO catalyst used as reference. The catalyst deactivation is related to th e dissolution of the metal oxides from the catalyst surface due to the acid ic reaction conditions. Generally, the performance of the catalysts was bet ter when the pH of the feed solution was increased. (C) 1999 Elsevier Scien ce B.V. All rights reserved.