Cu(5%)/Al2O3 catalytic performance on the phenol wet oxidation with H2O2: Influence of the calcination temperature

Abstract

In this work the catalytic performance of Cu(5%)/Al2O3 catalysts prepared by wet impregnation and calcined at three different temperatures, 400 ºC (WI 400), 650 ºC (WI 650) and 900 ºC (WI 900), was analyzed. These materials were tested in the phenol wet oxidation reaction using H2O2 (0.22 or 0.88 M) as an oxidizing agent, 1000 mg/L of phenol at 70 °C and atmospheric pressure. A complete conversion of phenol and a high extent of phenol mineralization were obtained for the three catalysts. Surface Cu2+ species suffered a reduction process during the catalytic reaction due to the drop of the pH value and a fraction of the reduced copper was leached to the liquid phase. Despite this, the increment in the calcination temperature produced a decrease in this reduction extent, inducing a protective effect to the Cu2+ species through the interaction between these and the support. Moreover, the existence of Cu-Al-O interactions not only diminished Cu2+ species reduction but also their leaching. Even though the WI 900 catalyst presented the lower leaching extent (36%), the remaining amount of copper in the solution still exceeded the allowed limit value for drinking water (1 mg Cu/L).