The Mo modified Ce/TiO2 catalyst for simultaneous Hg0 oxidation and NO reduction

Abstract

TiO2 supported CeMo catalyst (CeMo/TiO2) were employed for the first time to simultaneously oxidize elemental mercury (Hg0) and reduce nitrogen monoxide (NO) under simulated SCR atmosphere. The combination of molybdenum oxides and cerium oxides exhibits obvious synergy for Hg0 oxidation and NO reduction. CeMo/TiO2-0.3 catalyst exhibited an excellent Hg0 oxidation and NO reduction efficiencies of over 90% at above 250 °C corresponding to gas hourly space velocity (GHSV) of 119,000 h−1 (NO reduction) and 1,190,000 h−1 (Hg0 oxidation). Brunauer-Emmett-Teller (BET) surface area was not the dominating factor affecting the CeMo/TiO2 performance. Well-dispersion of active species, abundant chemisorbed oxygen and large surface oxygen capacity were responsible for its high catalytic activity. The presence of Hg0 exhibited a negligible effect on NO reduction. Low-concentration of NO inhibited the Hg0 oxidation while a relatively high concentration had a promotional effect inversely due to abundant NO2. NH3 consumed surface oxygen and competed to adsorb with Hg0 resulting in the deactivation of Hg0 oxidation while an excellent recovery was observed after simultaneous cutting off NH3 and introduction of O2. In addition, CeMo/TiO2-0.3 catalyst also presented an excellent resistance to SO2 and H2O poisoning and a good stability and recyclability. The possible mechanism for simultaneous NO reduction and Hg0 oxidation was proposed for CeMo/TiO2 catalysts.