Effects of microporous TiO 2 support on the catalytic and structural properties of V 2 O 5 /microporous TiO 2 for the selective catalytic reduction of NO by NH 3

Abstract Selective catalytic reduction (SCR) of NO by NH 3 over vanadium-based catalyst is often accompanied with unwanted nitrous oxide (N 2 O) formation, which has 300 times higher global warming potential than CO 2 . In this work, VO x dispersed on microporous TiO 2 catalysts calcined at various temperatures were applied to standard SCR reaction compared with VO x on commercial TiO 2 ones. Both catalysts showed stable NO x reduction activity although they did completely different trend in N 2 O formation. Specifically, N 2 O was much less produced on VO x /microporous TiO 2 catalysts regardless of calcination temperature with or without water in the reactant. Structural characterization of the catalysts using H 2 -TPR and Vanadium XANES revealed that the microporous TiO 2 could suppress the formation of bulk-like V 2 O 5 species, which are generally suggested as the main cause of N 2 O formation, in comparison of non-microporous commercial TiO 2 support. Also, NH 3 -TPD and in situ DRIFTS studies showed that VO x on microporous TiO 2 maintained strong Bronsted acidity so that it was capable of providing adsorbed NH 3 species readily up to high temperature, which led to the stable DeNOx performance. We found that such two promoting effects seemed functionally analogous to those of tungsten oxide, which is conventionally used as a promoting material for the VO x /TiO 2 catalyst. Our results demonstrated that vanadium oxides can be effectively stabilized up to high loading by structurally modifying TiO 2 support, and also provided reasonable explanation about the promoting effects of microporous TiO 2 support on the catalytic activity and structural properties of VO x /TiO 2 catalyst.