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 °C (WI 400), 650 °C (WI 650) and 900 °C (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).