Effects of reaction temperature on the photocatalytic activity of photo-SCR of NO with NH3 over a TiO2 photocatalyst

Abstract

Effects of reaction temperature on the activity of photo-assisted selective catalytic reduction (photo-SCR) of NO with NH₃ were investigated under very high GHSV conditions (100 000 h⁻¹). The reaction temperature had a significant effect on the photo-SCR activity over a TiO₂ photocatalyst. Maximum NO conversion was achieved at 433 K (NO conversion = 84%, N₂ selectivity = 100%). The apparent activation energies in the low and high temperature range were evaluated to be 9.0 kJ mol⁻¹ (353–433 K) and −2.7 kJ mol⁻¹ (493–593 K), respectively. Kinetic analysis revealed that the rate-determining step in the photo-SCR was decomposition of NH₂NO intermediates in all the ranges of the reaction temperature (353–593 K). The reaction temperature affects not only the rate constant of decomposition of NH₂NO intermediates but also the total number of active sites ([S]₀) and the equilibrium constant of NH₃ adsorption, resulting in the dynamic change in the reaction rate.