Mechanochemical localization of vanadia on titania to prepare a highly sulfur-resistant catalyst for low-temperature NH₃-SCR

This paper reports a novel attempt to mechanochemically localize vanadia on the surface of WO₃-TiO₂ by physically grinding high-vanadia-loading V₂O₅/WO₃-TiO₂ with WO₃-TiO₂. On the surface of the vanadia-localized catalysts, clustered vanadia sites exhibited enhanced activity for low-temperature (< 250 °C) NH₃-selective catalytic reduction (NH₃-SCR) by forming polymeric structures. The catalyst with localized vanadia simultaneously exhibited superior sulfur resistance, which has not been achieved in conjunction with high activity via conventional synthesis. Mechanochemical interactions between clustered vanadia and titania resulted in the formation of TiO₂ sites adjacent to the vanadyl species without deforming the polymeric structure of the vanadia. Density functional theory calculations showed that ammonium bisulfate (ABS) was considerably more stable in the presence of exposed TiO₂ adjacent to the vanadyl species. The exposed TiO₂ sites absorbed the deactivating material ABS from the clustered vanadia sites, which prevented the blockage of the catalytic active sites, leading to less deactivation.