Enhanced SO2 resistance of V2O5/WO3-TiO2 catalyst physically mixed with alumina for the selective catalytic reduction of NOx with NH3

Selective catalytic reduction with NH3 (NH3-SCR) is an effective NOx removal technology in the industry. Vanadia supported on tungsten titania (V2O5/WO3-TiO2) is most widely utilized for NH3-SCR because of its high tolerance to sulfur. Although it exhibits stable performance under SO2 in the stream, there are still unsolved sulfur poisoning issues under low-temperature operations due to the accumulation of ammonium bisulfate (ABS). In this study, we introduce a hybrid catalyst comprising V2O5/WO3-TiO2 physically mixed with alumina (VWTi + Al), which exhibited superior stability during SO2 aging compared to conventional vanadia catalysts. The improved sulfur tolerance originates from the direct migration of in-situ formed ABS from the vanadia domain to the alumina domain through physical contact rather than gas-phase SO2 adsorption on alumina. Interestingly, the mixed alumina maintains superior affinity to ABS as well as reusability after repetitive SO2 aging and regeneration. In addition, the protection ability, i.e. affinity to ABS, of mixed alumina closely related to its surface properties including acidity and pore size. The present study suggests that the hybrid catalyst can be an applicable catalyst to NOx removal process in stationary sources and a breakthrough for the decrease of pollutants emission.