CATALYTIC WET AIR OXIDATION OF PHENOL USING CeO₂AS THE CATALYST. KINETIC STUDY AND MECHANISM DEVELOPMENT

Abstract

ABSTRACT Using a CeO2 catalyst prepared from CeCl3 ċ 7H2O under high thermal impact, the catalytic wet air oxidation (CWAO) of phenol was effectively implemented. With initial phenol concentrations of between (400 and 2500) mg/L, and at a temperature of 160°C, the rate of phenol conversion increased with increased catalyst loading (0.2 g/L–1.0 g/L) and oxygen pressure (0.5 MPa–1.5 MPa). Even at an initial concentration of 2500 mg/L, conversion of phenol was as high as 95% after 3 h reaction. The effect of phenol concentration, catalyst loading, and oxygen pressure on the initial rate of phenol conversion was evaluated in a kinetic study. The initial rate equation derived from kinetic study is: R o = k 1 × [Ph]1.3–1.4 × W0.5–0.6 × Po 2 0.9–1.1, where k 1 is a rate constant, and [Ph], W and Po 2 refer to phenol concentration, catalyst loading and oxygen pressure, respectively. A free-radical involved reaction mechanism was proposed and an initial rate expression based on this mechanism was derived: R o = k 2 × [Ph]1.5 × W0.5, where k 2 is also a rate constant. Fitting of experimental data with the theoretically derived initial rate equation resulted in good correlation: the coefficient is greater than 0.99.