The enhancement effect of Cu modification on N2 selectivity of V0.5/Pt0.04/TiO2 catalyst for selective catalytic oxidation of NH3

Abstract

Background: Currently selective catalytic oxidation (SCO) is considered as an effective approach to remove slipped ammonia from exhaust gas of NH3-fuel engines. But it is still challenging to achieve high NH3 conversion and N2 selectivity simultaneously. Methods: Cu was introduced to modify V0.5/Pt0.04/TiO2 catalysts and the effects of Cu addition step and amounts on NH3 removal performance of the composite catalysts were investigated. Significant findings: Compared to V0.5/Pt0.04/TiO2 catalyst, Cu0.5V0.5/Pt0.04/TiO2 catalyst exhibited a similar NH3 conversion rate but a much better N2 selectivity. When reaction temperature was higher than 225 °C, a complete NH3 removal could be achieved for Cu0.5V0.5/Pt0.04/TiO2 catalyst, while N2 selectivity was higher than 80 % in a wide temperature range of 225–375 °C. The introduction of Cu resulted in the formation of CuVOx species with strong catalytic oxidation activity due to double redox couples of V5+/V4+ and Cu2+/Cu1+. There was a synergistic effect between CuVOx species and Pt species, which significantly facilitated i-SCR reactions, thus improving N2 selectivity. As main intermediates, -NH2 species actively participated in NH3-SCO reactions over Cu0.5V0.5/Pt0.04/TiO2 catalyst.