CuO/TiO2-ZrO2 wire-mesh catalysts for phenol wet oxidation: substrate effect on the copper leaching

Abstract

Structured catalysts are more suitable than powder catalysts for liquid phase reactions since their removal is simpler by avoiding filtration. In this work we present two structured catalysts consisting in CuO/TiO2-ZrO2 coated wire-meshes calcined at two different temperatures: 500 and 900 °C, Cu-TZ-W500 and Cu-TZ-W900. These catalytic systems were characterized by XRD, LRS, SEM/EDX, XPS and tested in the wet oxidation of phenol. The treated solutions were analyzed to investigate copper leaching, TOC conversion and identification of organic compounds. Powder equivalent formulations have also been prepared for comparison and analysis of substrate role. There is a clear effect of the substrate on the catalytic coating when strong calcination temperature (900 °C) is applied, by the migration of the steel components to the coating, inducing a protective effect on copper species and therefore avoiding metal leaching. This system reached 25% of conversion at 7 min, whereas this value was 100% for Cu-TZ-W500. Furthermore, the final XTOC were ∼ 42% for the first one and ∼ 79% for the second. Despite the lower XTOC obtained with Cu-TZ-W900, copper leaching was negligible. It was found that the higher reaction rate of Cu-TZ-W500 was driven by a combination of both heterogeneous and homogeneous pathways.