Effects of SO2 on selective catalytic reduction of NO with NH3 over a TiO2 photocatalyst

Selective Catalytic Reduction of NO by NH3 over Photocatalysts (Photo-SCR): Mechanistic Investigations and Developments

This account describes the work of our group in the selective catalytic reduction of nitrogen oxides (NO_x ) with ammonia over heterogeneous photocatalysts (photo-SCR) in the past 16 years. We have found that the photo-SCR proceeds over heterogeneous photocatalysts using a gas flow reactor, elucidated the reaction mechanism under UV- and visible-light irradiation by spectroscopic and kinetic studies, and developed a highly active photo-SCR system by improving the photocatalyst material itself and the reaction system with several approaches based on the reaction mechanism.

Removal of elemental mercury by TiO₂doped with WO₃ and V₂O₅ for their photo- and thermo-catalytic removal mechanisms

The catalytic removal of Hg(0) was investigated to ascertain whether the catalysts could simultaneously possess both thermo- and photo-catalytic reactivity. The immobilized V2O5/TiO2 and WO3/TiO2 catalysts were synthesized by sol-gel method and then coated on the surface of glass beads for catalytic removal of Hg(0). They were also characterized by SEM, BET, XRD, UV-visible, and XPS analysis, and their catalytic reactivity was tested under 100-160 °C under the near-UV irradiation. The results indicated that V2O5/TiO2 solely possessed the thermo-catalytic reactivity while WO3/TiO2 only had photo-catalytic reactivity. Although the synthesis catalytic reactivity has not been found for these catalysts up to date, but compared with TiO2, the removal efficiencies of Hg(0) at 140 and 160 °C were enhanced; particularly, the efficiency was improved from 20 % at 160 °C by TiO2 to nearly 90 % by WO3/TiO2 under the same operating conditions. The effects of doping amount of V2O5 and WO3 were also investigated, and the results showed that 10 % V2O5 and 5 % WO3/TiO2 were the best immobilized catalysts for thermo- and photo-catalytic reactivity, respectively. The effect of different influent concentrations of Hg(0) was demonstrated that the highest concentration of Hg(0) led to the best removal efficiencies for V2O5/TiO2 and WO3/TiO2 at 140 and 160 °C, because high Hg(0) concentration increased the mass transfer rate of Hg(0) toward the surface of catalysts and drove the reaction to proceed. At last, the effect of single gas component on the removal of Hg(0) was also investigated.