Relationship between structure and performance of a novel cerium-niobium binary oxide catalyst for selective catalytic reduction of NO with NH3

Abstract

A series of Ce-Nb binary oxide catalysts for the selective catalytic reduction (SCR) of NO with ammonia were synthesized using co-precipitation method and showed good catalytic activity and selectivity. The best catalyst Ce1Nb1 presented over 80% NO conversion in a wide temperature range of 200–450°C at a gas hourly space velocity (GHSV) of 120,000mLg−1h−1. The correlations among the structures, acid properties and redox behaviors of the catalysts were tried to establish. The BET specific surface areas of the binary oxides were larger than those of the monadic ones. The sample with Ce/Nb (1:1) possessed special NbO4 tetrahedral coordination. The surface acid sites were mainly provided by niobium oxide species. The NbOH bond was related to the Brønsted acid site and the NbO bond to the Lewis acid site. The abundance of surface adsorbed oxygen, the key factors for the catalytic behaviors, might arise from the short-range activation effect of niobium oxide species to cerium oxide species. In addition, water vapor only had a slight and reversible inhibition effect on the catalytic performance of the catalyst, and it might be a promising SCR catalyst for the practical application.