Optimization of high surface area VOx/TiO2 catalysts for low-temperature NH3-SCR for NOx abatement

Abstract

We have prepared two series of VOx/TiO2 catalysts (V surface density in the range 1.6–7.7 V at/nm2) employing anatase TiO2 with different surface area (89 and 181 m2/g) to find the optimal composition for the low temperature NH3 Selective Catalytic Reduction and correlate their physico-chemical properties to performance. The same platelet-like morphology was observed for the two TiO2 supports by electron microscopies and X-ray diffraction, indicating that the different surface area is only related to particle size. A higher amount of defective surface sites (undercoordinated Ti4+ sites at edges, corner and steps positions) was found on the high surface area TiO2 by FTIR spectroscopy of CO probe molecule. The distribution of VOx species determined by FTIR and Raman spectroscopies is similar on the two series, reaching the monolayer coverage and maximum activity at ≈ 5 V at/nm2, which can be considered the optimal V density for these catalysts.