Wet oxidation of phenol over transition metal oxide catalysts supported on Ce0.65Zr0.35O2 prepared by continuous hydrothermal synthesis in supercritical water

Abstract

The mixed oxide (Ce0.65Zr0.35O2) prepared by supercritical synthesis was applied as a support of transition metal (Mn, Fe. Co, Ni, and Cu) oxide catalysts for catalytic wet oxidation (CWO) of phenol in view of their higher thermal stability, better oxygen storage capacity, and higher surface area. The prepared catalysts showed an enhanced catalytic activity for CWO of phenol due to the excellent redox properties of ceria-zirconia mixed oxide. Among the prepared catalysts, the CuOx/Ce0.65Zr0.35O2 was the most effective catalyst in view of catalytic activity and CO2 Selectivity. The leached copper ions seem to contribute to the higher conversion of phenol over the CuOx/Ce0.65Zr0.35O2 via homogeneous catalysis. The characterization with XPS, XANES, and TPR experiments confirmed that the active copper species in the CuOx/Ce0.65Zr0.35O2 is highly dispersed Cu2+ clusters. Although the MnOx/Ce0.65Zr0.35O2 showed a high conversion of phenol and TOC, the converted phenol was mainly changed to carbon deposits on the surface of catalyst resulting in catalyst deactivation.