Model-Based Analysis Of The Photocatalytic Hci Oxidation Kinetics Over Tio2

The kinetic modeling 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 Cl-2 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 O-2 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 similar to 120 degrees 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.