Effects of microporous TiO2 support on the catalytic and structural properties of V2O5/microporous TiO2 for the selective catalytic reduction of NO by NH3

Selective catalytic reduction (SCR) of NO by NH3 over vanadium-based catalyst is often accompanied with unwanted nitrous oxide (N2O) formation, which has 300 times higher global warming potential than CO2. In this work, VOX dispersed on microporous TiO2 catalysts calcined at various temperatures were applied to standard SCR reaction compared with VOX on commercial TiO2 ones. Both catalysts showed stable NO reduction activity although they did completely different trend in N2O formation. Specifically, N2O was much less produced on VOxImicroporous TiO2 catalysts regardless of calcination temperature with or without water in the reactant. Structural characterization of the catalysts using H2 TPR and Vanadium XANES revealed that the microporous TiO2 could suppress the formation of bulk-like V2O5 species, which are generally suggested as the main cause of N2O formation, in comparison of nonmicroporous commercial TiO2 support. Also, NH3-TPD and in situ DRIFTS studies showed that VOX on microporous TiO2 maintained strong Bronsted acidity so that it was capable of providing adsorbed NH3 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 VOx/TiO2 catalyst. Our results demonstrated that vanadium oxides can be effectively stabilized up to high loading by structurally modifying TiO2 support, and also provided reasonable explanation about the promoting effects of microporous TiO2 support on the catalytic activity and structural properties of VOx/TiO2 catalyst. (C) 2017 Elsevier B.V. All rights reserved.