The superior catalytic performance of noble-metal-free Cu-ZSM-5@CoCeOx catalysts for selective catalytic oxidation of ammonia.

Abstract

In this study, core-shell like Cu-ZSM-5@CoCeOx catalysts were synthesized via a citrate sol-gel method followed by an ion-exchange process for the selective catalytic oxidation of ammonia (NH3-SCO). Owing to the synergism between CoCeOx and copper species, such catalysts exhibited superior NH3-SCO activity and N2 selectivity within the low-medium temperature range, where the optimal one obtained more than 95% NH3 conversion and over 94% N2 selectivity within 250-400 °C. Moreover, it also possessed excellent long-term catalytic stability. Characterization results revealed that the NH3-SCO reaction on Cu-ZSM-5@CoCeOx catalyst followed a SCO-fast SCR (selective catalytic reduction) tandem reaction mechanism. CoCeOx shell possessed strong redox capacity, allowing fast NH3 oxidation and producing large amounts of NO and NO2. And inner Cu-ZSM-5 core enriched ionic Cu species could efficiently consume the NOx generated from NH3 oxidation via fast SCR route, which also inhibited the N2O formation on CoCeOx via the coupling of HNO* (NH3 oxidation intermediate). This thereby resulted in the improved N2 selectivity over tandem catalyst. This work provides new insights into the rational design of highly efficient noble-metal-free NH3-SCO catalysts with suppressed secondary hazardous nitrogen-containing byproducts formation for industrial applications.

Abstract as supplied by the indexing source. © the authors / publisher.