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 promising technique for waste water treatment. Obtaining efficient and durable catalysts and determining the optimal process conditions are the key to successfully implementing this treatment. Copper-based catalysts supported over either silica or γ-alumina were prepared for this purpose. This research studies the influence of the pH on the performance of these catalysts. Activity tests were conducted for nine days in a trickle bed reactor operating at 140°C using air as oxidant. The results show that the silica supported catalyst is very sensitive to the acidic medium which leads to very short lifetimes. At first, the alumina supported catalyst also quickly losses activity but subsequently it stabilises with a residual phenol conversion several times higher than that of the silica supported catalyst. For both catalysts, a higher pH reduces the rate of catalyst deactivation by preventing the leaching of the copper oxides and lengthening their lifetime. The atmosphere (air or nitrogen) during calcination does not change their performance.