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

Rath, T. and Bloh, J.Z. and Lüken, A. and Ollegott, K. and Muhler, M.

Volume: 59 Pages: 4265-4272
DOI: 10.1021/acs.iecr.9b05820
Published: 2020

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 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 ∼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. Copyright © 2020 American Chemical Society.

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