Improved alkali-tolerance of FeOx-WO3 catalyst for NO removal via in situ reserving FeOx active species

The improvement of alkali tolerance of de-NOx catalysts remains an immense challenge for selective catalytic reduction (SCR) of NO by NH3. In this work, NOx removal efficiency was nearly retained in the presence of potassium over FeOx-WO3 (FW) catalysts via protecting iron active species using different template agents. Typically, FW using urea (FW-(urea)) as template agent showed superior de-NOx performance after being poisoned by potassium (K/FW-(urea)). Urea could promote the facile binding of potassium with WO3, which acted as alkali-poisoning sites so that iron active species were reserved to a great extent. Additionally, potassium species tended to be aggregated over K/FW-(urea) and thus a lot of iron active sites could be exposed. Besides, K/FW-(urea) catalyst has higher surface acidity, superior redox ability, stronger interaction of WO3 with Fe2O3, and more surface adsorbed oxygen compare with other parallel poisoned samples. This is the reason for the remarkable ability of potassium resistance over K/FW-(urea). The strategy of template regulation could offer a novel route for maintaining considerable NH3-SCR performance in the presence of alkali.

Automated summary

Improving the alkali tolerance of de-NOx catalysts for selective catalytic reduction (SCR) of NO by NH3 remains a significant challenge. In this study, different template agents were used to protect iron active species, leading to the retention of NOx removal efficiency in the presence of potassium over FeOx-WO3 catalysts. The use of urea as a template agent showed superior de-NOx performance even after being poisoned by potassium. The binding of potassium with WO3 promoted by urea allowed the preservation of iron active species. Additionally, the aggregation of potassium species in the catalyst resulted in the exposure of more iron active sites and higher surface acidity and redox ability. Template regulation strategy offers a novel route for maintaining considerable NH3-SCR performance in the presence of alkali.