Effects of Preparation Parameters for Mo-Modified V-Based SCR Catalyst on Simultaneous Hg(0) Oxidation and NO Reduction

In this study, molybdenum (Mo)-modified vanadium (V)-based selective catalytic reduction (SCR) catalysts were investigated for the simultaneous removal of elemental mercury (Hg(0)) and nitrogen oxide (NO) in terms of different metal loadings, impregnation sequences, TiO₂ phases, calcination temperatures, flue gas constituents, gas velocities, and reaction temperatures. Different impregnation sequences could lead to different Hg(0) oxidation performances. The modified SCR catalyst prepared using the impregnation sequence of Mo+W followed by V exhibited the highest Hg(0) oxidation performance. Meanwhile, the NO reduction performance was quite constant with respect to different impregnation sequences. Anatase phase TiO₂ and the calcination temperatures of 400 and 500 °C resulted in the best performance. The high calcination temperature of 700 °C resulted in TiO₂ phase transformation and agglomeration. The modified SCR catalyst prepared with optimal formulations showed ~99% Hg(0) oxidation and 87% NO reduction efficiencies at a molar ratio of NH₃ to NO of 0.9 under 350 °C and 5,000 hr^-1 space velocity in typical sub-bituminous and lignite coal simulated flue gases. Different characterization techniques including BET, TEM, XRD, XPS, and XAFS were employed to explore the mechanisms responsible for the performance differences. The detailed experimental and characterization results will be presented.