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

Abstract

This article illustrates the detailed decomposition behavior of NH4HSO4 on the TiO2 and TiO2–SiO2 supports, along with the effect of SiO2 addition on the sulfur resistance of the corresponding V2O5-based catalysts. For TiO2 support, sulfate species selectively occupied its surface basic hydroxyl groups, while Si–OH groups functioned as the main sites for the accommodation of NH4HSO4 over the TiO2–SiO2 mixed support, enabling its surface sulfate species with higher thermal stability. Compared with NH4+ on the TiO2 surface, NH4+ on the TiO2–SiO2 mixed support was much easier to be consumed during the heating process, hence causing some variations in the decomposition behavior of NH4HSO4. Finally, adding SiO2 enhanced the SO2 tolerance properties of the catalysts to a certain extent. When exposed to the SO2-containing flue gas, the deposition of NH4HSO4 mainly caused serious deactivation of SiO2-free catalyst, while the as-accumulated SO42– also contributed to the declined activity of SiO2-added catalyst. These results ensured the potential commercialization of TiO2–SiO2-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 SO2-tolerant ability.