TiO2-Supported Binary Metal Oxide Catalysts for Low-temperature Selective Catalytic Reduction of NOx with NH3

Binary metal oxide(MnOx-A/TiO2) catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide(TiO2), where, A indicates Fe2O3, WO3, MoO3, and Cr2O3. Their catalytic activity, N2 selectivity, and SO2 poisonous tolerance were investigated. The catalytic performance at low temperatures decreased in the following order: Mn-W/TiO2>Mn-Fe/TiO2>Mn-Cr/TiO2>Mn-Mo/TiO2, whereas the N2 selectivity decreased in the order: Mn-Fe/TiO2>Mn-W/TiO2>Mn-Mo/TiO2>Mn-Cr/TiO2. In the presence of 0.01% SO2 and 6% H2O, the NOx conversions in the presence of Mn-W/TiO2, Mn-Fe/TiO2, or Mn-Mo/TiO2 maintain 98.5%, 95.8% and 94.2%, respectively, after 8 h at 120 °C at GHSV 12600 h-1. As effective promoters, WO3 and Fe2O3 can increase N2 selectivity and the resistance to SO2 of MnOx/TiO2 significantly. The Fourier transform infrared(FTIR) spectra of NH3 over WO3 show the presence of Lewis acid sites. The results suggest that WO3 is the best promoter of MnOx/TiO2, and Mn-W/TiO2 is one of the most active catalysts for the low temperature selective catalytic reduction of NO with NH3.