Manganese Oxide/Titania Materials for Removal of NO _<i>x</i> and Elemental Mercury from Flue Gas

Abstract

A novel catalyst for low temperature selective catalytic reduction (SCR) using CO as reductant, MnO x supported on titania, has been shown to be effective for both elemental mercury capture and low temperature SCR. In low temperature (200 °C) SCR trials using an industrially relevant space velocity (50 000 h −1) and oxygen concentration (2 vol %), nearly quantitative reduction of NO x was obtained using CO as the reductant. Fresh catalyst used as an adsorbent for elemental mercury from an inert atmosphere showed remarkable mercury capture capacity, as high as 17.4 mg/g at 200 °C. The catalyst effectively captured elemental mercury after use in NO x reduction. Mercury capture efficiency was not affected by the presence of water vapor. Mercury capacity was reduced in the presence of SO 2. Manganese loading and bed temperature, which influence surface oxide composition, were found to be important factors for mercury capture. X-ray photoelectron spectroscopy (XPS) results reveal that the mercury is present in its oxidized form (HgO) in spent catalyst, indicating the participation of lattice oxygen of the catalyst in the reaction. These results suggest that a single-step process integrating low temperature SCR and mercury capture from flue gas might be feasible.