Behavior of titania-supported vanadia and tungsta SCR catalysts at high temperatures in reactant streams: Tungsten and vanadium oxide and hydroxide vapor pressure reduction by surficial stabilization

▶ Bulk vanadia and tungsta relative vapor pressures: V4O10 ∼ WO2(OH)2 > VO(OH)3 > (WO3)3. ▶ Without H2O, no V or W oxides vaporize from TiO2 surface. ▶ With H2O, WO2(OH)2 is much more volatile than VO(OH)3 on TiO2 surface. ▶ TiO2 surface lowers W-, V-oxide vapor pressures. ▶ W-, V-oxide vapor pressures are negligible on TiO2 supports with improved stability.