Model-Based Analysis of the Photocatalytic HCl Oxidation Kinetics over TiO₂

Ind. Eng. Chem. Res. 59 (2020), 4265-4272, doi: doi:10.1021/acs.iecr.9b05820

Abstract

The kinetic modelling of photocatalytic reactions is a powerful tool for process optimization. We applied a holistic kinetic model for the gas-phase photocatalytic oxidation of HCl to Cl₂ to identify suitable operation conditions and further optimization potential. We used a flat-plate photoreactor with UV LEDs and iodometric titration as online analytics and performed a comprehensive parameter variation. High O₂ and moderate HCl partial pressures resulted in the highest reaction rates, indicating a favorable reactant ratio of 4:1. An Arrhenius dependence of the reaction rate with an apparent activation energy of 25.7 kJ mol^-1 identifies a suitable reaction temperature of about 120°C. This temperature combines high reaction rates with high apparent quantum yields up to 8.4%, showing a logarithmic dependence of reaction rates on light intensity. The well-fitting kinetic model predicts that improving the intrinsic activity of the photocatalyst is the key for further enhancing the efficiency of photocatalytic HCl recycling.