Kinetic modeling for the deactivation of TiO2 during the photocatalytic removal of low concentration SO2

Abstract A kinetic model considering the deactivation of a catalyst was developed for the removal of low concentration SO 2 with TiO 2 as the photocatalyst. For the deactivation caused by poisoning of the reaction products, the catalyst activity which decreased with time was derived based on the Langmuir adsorption assumption. The calculated results of the kinetic model were consistent with the experimental data under various operation conditions, including inlet SO 2 concentration, space time, flue gas humidity, and time on stream. The kinetic model can be used to predict the evolution of the outlet SO 2 concentration, as well as the catalyst activity, with the operation time and the position of catalyst bed. The influences of water content on the reaction and deactivation processes of the catalyst were discussed based on the obtained kinetic parameters. The reaction and deactivation rate constants both increased with the increase in water content, which means that the presence of water in flue gas will not only promote the photocatalytic reaction of SO 2 but also accelerate the deactivation of the TiO 2 catalyst.