Sequentially prepared Mo-V-Based SCR catalyst for simultaneous Hg0 oxidation and NO reduction

Abstract

Molybdenum (Mo)-vanadium (V)-based selective catalytic reduction (SCR) catalyst synthesized by the sequential impregnation of Mo and W followed by V was investigated for simultaneous elemental mercury (Hg0) oxidation and nitrogen oxide (NO) reduction in an existing SCR unit with respect to different TiO2 phases, calcination temperatures, flue gas constituents, gas velocities, and reaction temperatures. Anatase phase TiO2 and the calcination temperatures of 400 and 500 °C resulted in ∼69% Hg0 oxidation at 10 ppmv HCl and 350 °C. The high calcination temperature of 700 °C resulted in TiO2 phase transformation from anatase to rutile and agglomeration. The modified SCR catalyst prepared with the impregnation sequence of Mo and W followed by V using anatase TiO2 and calcination temperature 500 °C showed ∼99% Hg0 oxidation and 87% NO reduction conversions at an NH3/NO molar ratio of 0.9 under 350 °C and 5,000 hr−1 space velocity in typical sub-bituminous and lignite coal simulated flue gases. The effects of these parameters and conditions were further investigated using various characterization techniques including BET, TEM, XRD, NH3 TPD and XAFS.