Exploration of surface properties of Sb-promoted copper vanadate catalysts for selective catalytic reduction of NOX by NH3

Abstract

A way to fulfill efficient exploitation of desired catalytic nature provided by V oxide is to modify its chemical structure through the incorporation of secondary transition metal species. This paper reports the use of Cu as a modifier of high-valent V oxide (V2O5) to produce a class of copper vanadates and their utilization as active sites for the selective catalytic reduction of NOX (X = 1 or 2) by NH3 (NH3-SCR). All catalysts contained ∼2 nm-sized copper vanadate particles highly dispersed on anatase with desired vanadate phases. The anatase-supported Cu5V2O10 provided a greater quantity of acid sites with improved redox character than Cu1V2O6, Cu2V2O7, and Cu3V2O8, thereby exhibiting the greatest NH3-SCR performance under ideal reaction conditions. Anatase-supported Cu3V2O8, however, was found to possess the most preferred surface properties among the catalysts post sulfation. This was evidenced by NH3-SCR runs of the catalysts under reaction conditions with H2O and SO2-including stream, where all catalysts were pre-sulfated by SO2 and O2 at elevated temperatures. The NH3-SCR performance of the optimum Cu3V2O8 on anatase was further promoted after sulfation of the catalyst with the optimum content of Sb promoter. The Sb promoter was verified to enhance the redox feature and minimize the interactions among catalyst surfaces and SO2/ammonium (bi)sulfates during the NH3-SCR, as evidenced by durability experiments. While showing N2 selectivities as ∼100% at ≤ 400 °C, the optimized Sb-promoted Cu3V2O8 on anatase showed high NOX conversions (≥ ∼85%) at ≥ 220 °C and outperformed the control vanadia-tungstate on anatase, which was used to simulate a commercial catalyst. This paper remarks the exploration of the variable structures of metal vanadates can be a good strategy to discover high-performance catalytic solids for the reduction of NOX species.