Aqueous phase catalytic oxidation of phenol in a trickle bed reactor: Effect of the pH

The catalytic oxidation of organic compounds in aqueous phase is a promisin g technique for waste water treatment. Obtaining efficient and durable cata lysts and determining the optimal process conditions are the key to success fully implementing this treatment. Copper-based catalysts supported over ei ther silica or gamma-alumina were prepared for this purpose. This research studies the influence of the pH on the performance of these catalysts. Acti vity tests were conducted for nine days in a trickle bed reactor operating at 140 degrees C using air as oxidant. The results show that the silica sup ported catalyst is very sensitive to the acidic medium which leads to very short lifetimes. At first, the alumina supported catalyst also quickly loss es activity but subsequently it stabilises with a residual phenol conversio n several times higher than that of the silica supported catalyst. For both catalysts, a higher pH reduces the rate of catalyst deactivation by preven ting the leaching of the copper oxides and lengthening their lifetime. The atmosphere (air or nitrogen) during calcination does not change their perfo rmance. (C) 1999 Elsevier Science Ltd. All rights reserved.