Tailoring valence state of V in V-Mo atomically dispersed ensemble enables exceptional NH4HSO4 poisoning resistance for NH3-SCR reaction

Although V2O5/WO3/TiO2 catalyst has been commercially used for selective catalytic reduction of NOx with NH3 (NH3-SCR), it suffers from activity loss due to ammonium bisulfate (ABS) poisoning at low temperatures below ABS dew point (<280 degrees C). Here, we demonstrate that V2O5/MoO3/TiO2 catalyst with H2 pretreatment (designated V2O5/MoO3/TiO2_H2) exhibits high activity and excellently stable NH3-SCR performance at 180-230 degrees C under SO2 and H2O poisoning conditions. Nevertheless, commercial V2O5/WO3/TiO2 catalyst is quickly deactivated under identical conditions after reaction for 25 h due to formation of liquid-like ABS. Electronic structure investigations show that H2 pretreatment decreases oxidation states of V species of the V2O5/MoO3/TiO2_H2 catalyst, and reduced V species suppress the SO2-to-SO3 oxidation rate. The suppression of SO2-to-SO3 oxidation rate contributes to lower formation rate of ABS on catalyst surface. MoO3/TiO2 with ABS decomposition ability different from those of conventional or bulk material was synthesized on the basis of our previous efforts, and used as a fundamental building block in V2O5/MoO3/TiO2_H2. Control experiments show that the MoO3/ TiO2 building block in V2O5/MoO3/TiO2_H2 has excellent ability to decompose ABS. Difficulty of ABS formation and rapid decomposition rate of ABS offer a net result in terms of improved ABS resistance and high activity for V2O5/MoO3/TiO2_H2 catalyst.

Automated summary

By pretreating the V2O5/MoO3/TiO2 catalyst with H2, it shows high activity and excellent stability in NH3-SCR performance under SO2 and H2O poisoning conditions at low temperatures. On the other hand, the commercial V2O5/WO3/TiO2 catalyst quickly deactivates due to the formation of liquid-like ABS.