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H2O resistance of a catalyst is often underrated in reducing wet NOX and forming/pyrolyzing ammonium (bi)sulfate (AS/ABS) poisons, yet, is improved markedly when Ni1V2O6 and Sb2O5 serve as a prime activator and a promoter, respectively.

The role of SiO2 and WO3 in CeVO4-based catalyst supported on TiO2 support containing silica-tungsten was systematically investigated for selective catalytic reduction (SCR) by hydrothermal aging. It has been found that the CeVO4 with SiO2 and WO3 added to TiO2 (i.e., CeVO4/TWS) is the optimal catalyst to promote N2 selectivity through improved thermal stability and NH3 oxidation. CeVO4/TWS(HT; hydrothermal aging) had abundant defects and surface adsorbed oxygen species even after thermal aging. The high Vn+ (n = 4, 3) fraction of CeVO4/TWS(HT) is due to the improved thermal stability by adding SiO2 and WO3 to TiO2. The addition of SiO2 and WO3 maintains NH3 adsorption and redox properties, so the TWS support exhibits high thermal stability. As the NH3-SCR reaction mechanism, the pristine catalyst shows an Eley–Rideal and Langmuir–Hinshelwood models as dual model (ER-LH) based on abundant Lewis and Bronsted acid sites below 300 °C. On the other hand, the hydrothermal aged catalyst dominates the Eley–Rideal mechanism (reaction of activated ammonia with gaseous NO) based on Lewis acid sites. This study comprehensively shows that CeVO4-based catalysts have improved thermal stability by including SiO2 and WO3 in the TiO2 support.

The effect of adding Mo and/or Sb to a VTi catalyst on its activity and durability in the selective catalytic reduction (SCR) of nitrogen oxide by NH3 was investigated. The addition of an appropriate amount of Mo–Sb significantly improved the catalyst specific surface area, enhanced the number of Bronsted acid sites, and adjusted the surface species composition. The catalytic activity improved as the Vn+ (n = 4, 3) fraction increased due to the formation of functional groups on the catalyst surface. The redox properties, amount of active labile oxygen, and number of surface oxygen vacancies were improved by the presence of V2MoO8. This species also played an important role in improving the SCR performance and water/sulfur durability of the catalysts due to its sufficient acidity enhancement and reduction of SO2 adsorption. The addition of Mo–Sb likely enhanced catalyst SO2 durability because it reduced SO2 adsorption by inhibiting the reaction between terminal oxygen (V = O) and SO2(g).