Enhanced performance of Nb2O5 decorated RuO2/Sn0.2Ti0.8O2 for selective catalytic oxidation of ammonia

The ammonia slip from denitration system can result in environmental damage. Selective catalytic oxidation of ammonia (NH3-SCO) to nitrogen is one of the ideal technologies to control NH3 emission. In this work, RuO2/Sn0.2Ti0.8O2 catalysts with different Ru content and modified with Sb or Nb were evaluated for NH3-SCO. The results indicated that the RuO2&Nb2O5/Sn0.2Ti0.8O2 exhibited the similar catalytic activity and superior N2 selectivity within a wide temperature range in NH3-SCO, in comparison with RuO2/Sn0.2Ti0.8O2 and RuO2&Sb2O5/Sn0.2Ti0.8O2. Multiple techniques were used to reveal the effect of the physicochemical properties of the catalysts on the catalytic activity and N2 selectivity. For RuO2/Sn0.2Ti0.8O2, with the increasing ruthenium loading the activity enhanced together with the decline in N2 selectivity due to the high redox ability of highly dispersed ruthenium and the lack of acid sites. Particularly, in situ DRIFTS and NH3-TPD demonstrated the addition of Nb2O5 increased the quantity of acid sites, especially the Brønsted acid sites that were essential to improve N2 selectivity. During NH3 oxidation, the Brønsted acid sites promoted the activation of adsorbed ammonia to produce abundant amide intermediates (-NH2), which could directly react with the NO species to generate N2.