Performance and kinetic study on selective catalytic reduction of NO_x with NH₃ of MnO_x-WO₃/TiO₂ catalyst

The catalytic activities of MnO_x-WO₃/TiO₂ catalyst in a wide temperature range were investigated for selective catalytic reduction (SCR) of NO with NH₃. It yields 80.3%-99.6% NO_x conversion and 98.7%-100% selectivity for N₂ product from 100°C to 350°C at GHSV 18900 h^-1. In the presence of 0.01% SO₂ and 6% H₂O at 120°C, the NO_x conversion maintains at 98.5%. At 300°C and with 0.07% SO₂ in the reactant stream, the NO_x conversion is 99%, as high as that of the commercial V-W/TiO₂ catalyst. The steady-state kinetic study shows that O₂ plays a promoting role. When O₂ content is less than 1.5%, the NO_x conversion increases sharply with O₂ concentration. The reaction order is zero with respect to NH₃ and first with respect to NO with excess O₂ and H₂O. The active energy of Mn-W/TiO₂ calculated is 6.24 kJ·mol^-1 according to the kinetic experiments at various temperatures, much lower than other catalysts reported in the literatures. Thus Mn-W/TiO₂ is an excellent catalyst for SCR NO with NH₃.