Characteristics of titania supported copper oxide catalysts for wet air oxidation of phenol.

Various techniques have been used to characterize the CuOx/TiO2 catalysts with different copper loading. Surface area, pore volume and pore size distribution of the prepared catalysts were estimated from nitrogen adsorption isotherm. Temperature programmed reduction (TPR), X-ray diffraction (XRD), electron spin resonance (ESR), X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) experiments were performed to investigate the chemical state of the copper species. The chemical state of copper in the CuOx/TiO2 catalysts varied with copper loading (1–25wt.%): highly dispersed Cu2+ cluster for 1 and 5wt.%, and bulk CuO for 7–25wt.%. The activity and mineralization selectivity of the CuOx/TiO2 catalysts increased with copper loading up to 20wt.%, and remained almost constant for higher copper loading. The optimum copper loading was 20wt.% for the wet air oxidation of phenol over the CuOx/TiO2 catalysts in this work. The stability of the CuOx/TiO2 catalysts with different copper loading was also studied with respect to carbonaceous deposits and copper leaching.