Promotion of NH4HSO4 decomposition in NO/NO2 contained atmosphere at low temperature over V2O5-WO3/TiO2 catalyst for NO reduction

Formation of NH4HSO4 and its deposition on catalyst surface are the main obstacle for the application of NH3-SCR technology at low temperature. In this work, the deposited NH4HSO4 was found to be highly active towards NO in the NO/NO2 contained atmosphere on the V2O5-WO3/TiO2 catalyst. The reaction profiles indicate that the NO/NO2/O-2 mixture can rapidly react with NH4+ of NH4HSO4 above 100 degrees C, while NO/O-2 mixture can only strongly react with NH4HSO4 above 300 degrees C. Regenerations of NH4HSO4-deactivated catalyst were performed in both NO/O-2 and NO/NO2/O-2 atmospheres and the performances were compared. Results from FTIR, XPS and EDS characterizations indicate the S-containing groups of deposited NH4HSO4 will be stabilized as metal sulfate after NH4+ is consumed by NOx. The BET and BJH analysis shows that the NO/NO2/O-2 mixture can recover the pore structure of NH4HSO4-deposited catalyst more effectively than NO/O-2 mixture does. The SCR activity tests reveal that the regeneration by NO/NO2/O-2 mixture can remarkably restore the activity of NH4HSO4-deactivated catalyst.