Kinetics of the Wet Oxidation of Phenol over an Fe/Activated Carbon Catalyst

Abstract

Wet oxidation of phenol over an Fe/activated carbon catalyst has been studied in a trickle-bed reactor in the following operational window: inlet C phenol=0.5 and 1 g/L, T=100-127 °C, PT=3-8 atm, W=0-4.8 g, QL=0.125-2 mL/min and QO2=91.6 NmL/min. The experiments were carried out in the absence of mass transfer limitations. Oxidation and mineralization reactions of phenol are proven to take place on the catalyst surface through a heterogeneous mechanism. Due to the complexity of the phenol oxidation route, simple reaction schemes have been assumed by lumping the intermediate species and generalized kinetic models for phenol and TOC abatement have been proposed. Two kinetic expressions, a power law rate and a Langmuir-Hinshelwood type rate expression, have been considered but only a convergence with statistically reliable parameters was found for the former model. A power law model with first order for phenol and 0.74 for oxygen and apparent activation energy of 74 kJ/mol described the experimental results in the oxidation of phenol well. Mineralization of phenol (TOC abatement) was described by a similar rate expression and takes into account the presence of refractory species such as the low molecular weight acids formed upon phenol oxidation.