Performance and kinetics studies on selective catalytic reduction of NO_x with NH₃ over MnO_x-WO₃/TiO₂ catalyst

The catalytic activities of MnOx-WO3/TiO2 for selective catalytic reduction(SCR) of NO with NH3 were investigated in a wide range of temperature and reaction condition. It yielded a NO_x conversion of 80.3%-99.6% and a N2 product selectivity of 100%-98.7% during 100 °C to 350 °C at gas hourly space velocity(GHSV)=18900 h-¹. In the presence of 0.01% SO₂ and 6% H₂O at 120 °C, the NOx conversion can maintain 98.5%. At 300 °C and with 0.07% SO₂ in reactant stream, the NO_x conversion stabilized at 99% as high as the commercial V-W/TiO₂ catalyst's level. The steady-state kinetics study shows that O₂ played a promoting role. In the presence of less than 1.5% O₂, NO_x conversion can increase sharply with the increase of O2 concentration. The reaction order was zero with respect to NH₃ and first with respect to NO with excess O₂ and H₂O. The kinetics active energy(E_a) of Mn-W/TiO₂ was calculated to be 6.24 kJ/mol according to the kinetic experiment at various temperatures, much lower than those of other catalysts reported in the literature. Mn-W/TiO₂ is an excellent catalyst for SCR of NO with NH₃ by now.