(170d) Novel but Simple Method to Prepare Vanadia Catalyst with Superior Sulphur Resistance and NOx Removal Activity

Nitrogen oxides (NOx) are a pollutant present in combustion gases that have serious deleterious effects on the human body, and these species also participate in photochemical processes that result in smog and acid rain. Nevertheless, NOx can be efficiently removed from exhaust gases by implementing selective catalytic reduction with NH₃ (NH₃-SCR). TiO₂-supported vanadia catalysts are the most common materials used in NH₃-SCR processes since they offer excellent denitrification ability and high sulfur resistance, in the temperature range from 300 to 400 °C. However, as environmental regulations become more stringent and applied to various fields in the future, the necessity of operating SCR at low-temperature below 250 °C becomes more important. Although it is known that V-based catalysts have relatively high sulfur resistance, they are not free from sulfur deactivation at the temperature below 250 °C due to the formation of ammonium bisulfate (ABS), which can physically block the pores in the catalyst, deteriorate the catalytic performance (Eq 1).

NH₃ + H₂O + SO₃ = NH₄HSO₄ (l) ---- (1)

Thus, the current technology has a huge dilemma in achieving both low-temperature activity and high sulfur resistance. Here, we report that Y zeolite can be physically mixed with the vanadia catalyst to effectively trap liquid ABS, protecting most V sites from deactivation by ABS and demonstrating stable NH₃-SCR performance at 220 °C. The sulfur resistance of physically mixed catalyst was 3 times higher than VWTi, and order of magnitude higher compared to the commercial low-temperature catalysts (Cu-SSZ-13 and Mn/TiO₂). Moreover, the activity of VWTi+ Z recovered almost completely after regeneration at 350 °C where ABS decomposes

This study proposed a simple but novel “physical mixing” strategy to achieve excellent sulfur resistance of the vanadia NH₃-SCR catalyst with high NOx removal ability. Moreover, the developed physical mixing catalyst was transferred to the POSCO steelmaking company and successfully commercialized in their sintering process.