Regulation of NH3-SCR Reaction Pathway over MnOx/TiO2 Catalyst by WOx Promotion and the Synergistic Enhancement Effect of VOx

Effective abatement of nitrogen oxides (NOx) is achieved by ammonia selective catalytic reduction (NH3-SCR). In this paper, the effects of single WO3 doping and WOx-VOx co-doping into the MnOx/TiO2 catalyst on NH3-SCR of NOx removal, sulfur and water resistance, and reaction mechanisms were systematically investigated. The 5MnOx/TiO2, WO3-5MnOx/TiO2, and WO3-V2O5-5MnOx/TiO2 were prepared using the incipient-wetness impregnation method. Furthermore, the monolithic WO3-V2O5-5MnOx/TiO2-CC (cordierite support) catalyst involved a coating process. The WO3-V2O5-5MnOx/TiO2 catalyst demonstrated superior NO conversion and maintained over 80% activity following prolonged exposure to SO2 and H2O. Characterization results indicated that the introduction of WO3 regulated Mn valence through the formation of W-O-Mn bonds. The synergistic effect of V2O5 and WO3 further promoted electron transfer, increased surface chemisorbed oxygen and oxygen vacancies, and strengthened reactant adsorption and activation. In situ DRIFTS analysis suggested that WO3 modulated the reaction pathway, and while 5MnOx/TiO2 followed the Langmuir–Hinshelwood (L-H) mechanism, both WO3-5MnOx/TiO2 and WO3-V2O5-5MnOx/TiO2 exhibited a combined L-H and Eley–Rideal (E-R) pathway. This study confirmed that WO3 played a crucial regulatory role in both single-metal and multi-metal systems, and the synergistic interaction between V2O5 and WO3 was the key to achieving superior denitration performance and poisoning resistance.