Vanadium-density-dependent thermal decomposition of NH4HSO4 on V2O5/TiO2 SCR catalysts

In this study, the thermal decomposition of NH4HSO4 (ABS) on two typical V2O5/TiO2 catalysts (0.5 wt% and 4.5 wt% vanadia loadings) was studied. The vanadium-density-dependent decomposition process of ABS was verified using thermogravimetric analysis followed by IR and XPS investigations. The vanadium density strongly influences the interaction between the ABS and catalyst surface, thus changing the decomposition process of the ABS-related surface species. For the 0.5 wt% V2O5/TiO2 catalyst, the bidentate SO42- species that formed from the interaction between the ABS and TiO2 support have higher thermal stability than those of pure ABS (ca. 330 degrees C). The decomposition temperature of these species was above 350 degrees C. Meanwhile, the remaining NH4+ has lower thermal stability, which started at ca. 250 degrees C. By contrast, for the 4.5 wt% V2O5/TiO2 catalyst, the ABS was deposited on the catalyst surface probably through a VOSO4 analogous structure rather than being bonded to the TiO2 sites, such that the decomposition process of the ABS was very similar to that of pure ABS with only a slight decomposition delay. This study suggests that different regeneration strategies for ABS deactivation should be adopted depending on the vanadia loadings of the V2O5/TiO2 catalysts.