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

Abstract

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 °C). The decomposition temperature of these species was above 350 °C. Meanwhile, the remaining NH₄⁺ has lower thermal stability, which started at ca. 250 °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.