Kinetics of wet air oxidation of phenol over a novel catalyst

The wet air oxidation kinetics of an aqueous solution of phenol was studied over extrudates of an Al-Fe pillared clay catalyst in the temperature range of 90-150 degreesC and air pressure range of 0.8-2.5 MPa. The variables studied included reaction temperature, air pressure, solution pH, initial phenol concentration, and catalyst loading. The obtained findings are compared with those obtained using hydrogen peroxide oxidation. A group of kinetic models considering both the power-law and Langmuir-Hinshelwood approaches was evaluated to describe the catalytic kinetics of the phenol disappearance. The nonlinear dependence of the phenol conversion rate on the catalyst concentration was taken into account via the empirical power-law function of this variable. Finally, a kinetic model was discriminated on the basis of equilibrium adsorption of phenol and dissociated oxygen on two distinct types of active sites. The rate-controlling step was assumed to be the surface reaction between adsorbed reactant species. This model was able to predict well the experimental results over the entire range of the variables studied.