Tailoring the proceeding of the NH3-SCO and NH3-SCR reactions over FeOx catalysts by modifying with NbOx

Abstract

This study presents the synthesis of a series of FeO_x-NbO_x mixed oxide catalysts for the selective catalytic reduction (SCR) of NO by NH₃. By meticulously controlling the Fe/Nb molar ratio, we have rationally tailored the proceeding of the main reaction of NO reduction and the side reaction of NH₃ oxidation to NO_x. The incorporation of NbO_x introduced a significant number of acid sites, which enhanced the adsorption of NH₃ on the catalyst surface, particularly at elevated temperatures. Additionally, the oxidative capacity of the catalyst was moderated by the addition of NbO_x, hindering the over-oxidation of NH₃ to NO or NO₂, thus preserving more NH₃ to act as a reductant for NO reduction. Consequently, the NbO_x-enriched samples exhibited improved deNO_x performance. However, an excessive amount of NbO_x led to a notably weakened oxidative ability, which negatively impacted the activation of reactants and resulted in decreased NO conversion at lower temperatures. The optimized catalyst presented >80 % NO conversion and >95 % N₂ selectivity within a temperature range of 250–400 °C. These findings offer valuable insights for the development of new catalysts with an extended operational temperature window.