Simultaneous NO reduction and Hg0 oxidation over Sb modified Mn/TiO2 catalyst

Abstract

Sb-modified Mn/TiO2 catalyst synthetized by sol–gel method exhibited outstanding performance in simultaneous Hg0 oxidation and NO reduction under SCR conditions at low temperature. NO removal (>90%) and Hg0 oxidation (>80%) were simultaneously obtained over MnSb/TiO2-0.25 catalyst in 200–300 °C with a GHSV of 54,000 h−1. Moreover, MnSb/TiO2-0.25 catalyst exhibited excellent tolerance to SO2 and H2O. Characterization results suggested that the well-dispersed Mn, Sb and Ti species, along with the enriched Mn4+ and surface oxygen species on Mn-Sb/TiO2-0.25 catalyst should play a critical role in its excellent catalytic performance. The formed HgO had little inhibition effect on NO reduction over MnSb/TiO2-0.25 catalyst. And the coexistence of NO and O2 has a promotion effect on Hg0 oxidation, while NH3 exhibited an inhibition effect on oxidation of Hg0. In SCR reaction process, the Hg0 oxidation efficiency was suppressed, but this effect could be basically eliminated by using a relatively low GHSV value. Thus using MnSb/TiO2-0.25 for simultaneous Hg0 oxidation and NO reduction in SCR reactor may be workable in coal-burning power plants. Based on the results of experiments and characterizations, the mechanism of synchronous removal of Hg0 and NO on MnSb/TiO2-0.25 catalyst could be described as:Hg0(ad)+Oα(Oβ)→HgO(ad), NO(g)+NO2(ad)+NH3(ad)→N2+H2O.