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 N-2 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 N-2 selectivity. For RuO2/Sn0.2Ti0.8O2, with the increasing ruthenium loading the activity enhanced together with the decline in N-2 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 Bronsted acid sites that were essential to improve N-2 selectivity. During NH3 oxidation, the Bronsted acid sites promoted the activation of adsorbed ammonia to produce abundant amide intermediates (-NH2), which could directly react with the NO species to generate N-2. (c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.