New insight into the role of Mo-Sb addition towards VMoSbTi catalysts with enhanced activity for selective catalytic reduction with NH3

Abstract

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).