Generalized Kinetic Model for the Catalytic Wet Oxidation of Phenol Using Activated Carbon as the Catalyst

Catalytic wet oxidation of phenol using a commercial activated carbon (supplied by Chemviron Carbon) as the catalyst has been studied. The phenol oxidation has been carried out at middle temperatures (127-160 (degree) C) and oxygen pressures (3.4-16 bar). An integral fixed-bed reactor with concurrent upflow of the gas and liquid phases that allows reaching of the steady state has been used as the experimental setup. The activated carbon employed is stable at the maximum temperature and pressure employed for periods higher than 200 h. It was found that the reaction takes place only at the catalyst surface, with the adsorption phenomena for both organic compounds and oxygen being significant. A generalized kinetic model is proposed for phenol oxidation and mineralization. The selected model, discriminated among several proposed, includes an adsorption term and fits the experimental data quite well. Moreover, small amounts of stable short-chain organic acids are produced in the phenol oxidation, and this fact is also taken into account in the kinetic model for the phenol mineralization rate description.