Mechanistic investigation of enhanced reactivity of NH4HSO4 and NO on Nb- and Sb-doped VW/Ti SCR catalysts

This study focused on promotional effect of Sb2O5 and Nb2O5 addition to V-SCR on decomposition of NH4HSO4, reactivity of NH4HSO4 and NO, and sulfur resistance. Adding Sb2O5 and Nb2O5 increased the electron cloud density around the S atoms in SO42-, which exerted a positive effect on the transformation of SO42- to SO2 in the lower temperature region. As a result, the decomposition behavior of NH4HSO4 was obviously enhanced on the promoters-modified catalysts. Meanwhile, a high reactivity of NH4HSO4 with NO was observed with the introduction of Sb2O5 and Nb2O5, which could be explained by the increased amount of V5+ and reactive electrophilic oxygen species on the Sb2O5- and Nb2O5-doped catalyst surfaces. Finally, the deactivation of catalysts by SO2 and H2O was impeded in a certain extent through introducing Nb2O5 and Sb2O5, suggesting that these promoters-modified catalysts might be typically used in the low-temperature SCR systems in the future.