Wet oxidation of phenolic solutions over heterogeneous catalysts: Degradation profile and catalyst behavior

Removal of phenol by wet air oxidation (WAO) from dilute aqueous solutions was conducted in the presence of oxygen over a 1 wt% Pt/Al2O3 and Mn/Ce (7/3) composite oxide catalysts. The reaction was carried out in a batch slurry reactor using pure oxygen as an oxidizing agent under mild reaction conditions, i.e., temperature from 80 to 175 degrees C and oxygen pressure from 0.5 to 1.5 MPa. The platinum catalyst was found to be moderately active, while the Mn/Ce catalyst was remarkably effective in reducing both phenol concentration and total organic carbon. On both catalysts the kinetics of phenol removal was characterized by a fast reaction step followed by a slower one. During WAO reaction, a carbonaceous material was formed and deposited on the catalysts surface. This deposit was characterized by temperature-programmed oxidation coupled to mass spectrometry detection and X-ray photoelectron spectroscopy. (C) 1998 Academic Press.