New Insights into the Role of WO3 in Improved Activity and Ammonium Bisulfate Resistance for NO Reduction with NH3 over V–W/Ce/Ti Catalyst

The W-modified V–W/Ce/Ti-x% catalysts are prepared to investigate their selective catalytic reduction (SCR) activity. The V–W/Ce/Ti-5% with 5% WO3 loading shows superior NH3-SCR activity and higher ammonium bisulfate (ABS) resistance at 280 °C. The 5% WO3 doping can induce the isolated tetrahedrally coordinated vanadium species to transform into the oligomeric ones and strongly combine with neighboring V and Ce via synergetic interaction (V4+ + Ce4+ ↔ V5+ + Ce3+ and W5+ + Ce4+ ↔ W6+ + Ce3+), which favors the electron conduction among these active sites and significantly enhances the NOx conversion rate. Moreover, WO3 doping suppresses the formation of ABS and metal sulfate species over active sites by lowering the alkalinity of V–W/Ce/Ti-5%. The synergetic interaction through electron transfer can lower the thermal stability of ABS species and cause the NH3-SCR reaction between NO + O2 and ABS to completely prohibit the formation of ABS because of the faster de-NOx conversion rate with 5% WO3 loading.