New Insights into the Decomposition Behavior of NH4HSO4 on the SiO2-Decorated SCR Catalyst and Its Enhanced SO2-Resistant Ability

This article illustrates the detailed decomposition behavior of NH 4 HSO 4 on the TiO 2 and TiO 2 -SiO 2 supports, along with the effect of SiO 2 addition on the sulfur resistance of the corresponding V 2 O 5 -based catalysts. For TiO 2 support, sulfate species selectively occupied its surface basic hydroxyl groups, while Si-OH groups functioned as the main sites for the accommodation of NH 4 HSO 4 over the TiO 2 -SiO 2 mixed support, enabling its surface sulfate species with higher thermal stability. Compared with NH 4 + on the TiO 2 surface, NH 4 + on the TiO 2 -SiO 2 mixed support was much easier to be consumed during the heating process, hence causing some variations in the decomposition behavior of NH 4 HSO 4 . Finally, adding SiO 2 enhanced the SO 2 tolerance properties of the catalysts to a certain extent. When exposed to the SO 2 -containing flue gas, the deposition of NH 4 HSO 4 mainly caused serious deactivation of SiO 2 -free catalyst, while the as-accumulated SO 4 2- also contributed to the declined activity of SiO 2 -added catalyst. These results ensured the potential commercialization of TiO 2 -SiO 2 -based catalysts in the typical low-temperature selective catalytic reduction systems in the short run and pointed out a strategy to design new catalysts with superior activity and enhanced SO 2 -tolerant ability.