Pt/ZrO₂: An Efficient Catalyst for Aerobic Oxidation of Toluene in Aqueous Solution

Abstract

The heterogeneous oxidation of toluene in aqueous medium has been investigated. Artificially contaminated water with aromatic compound (toluene) was exposed to a simple platinized zirconia (1% Pt/ZrO 2 ) catalyst in the presence of molecular oxygen. This selective oxidation of toluene to benzyl alcohol, benzaldehyde and benzoic acid provides a step for removing toluene from wastewater or converting it into less harmful substances. Different parameters, e.g. the reaction time, temperature, pressure, the amount of catalyst and agitation, etc influenced the toluene conversion and selectivity. Typical batch reactor kinetic data were obtained and fitted to the classical Langmuir-Hinshelwood model, Mars-van Krevelen model as well as to the Eley-Rideal model of heterogeneously catalyzed reactions. The Eley-Rideal model was found to give a better fit. 1% Pt/ZrO 2 was observed to be the most active for oxidation of toluene at 333 K in oxygenated atmosphere [p(O 2 ) ca. 101 kPa] with a nominal stirring speed ≥900 r/min. It was found that catalytic oxidation may be an effective method for the removal of volatile organic compounds from aqueous solutions and comparable to other advanced oxidation processes.