Performance and tolerance to SO₂ of MnO_x-WO₃ /TiO₂ catalyst for selective catalytic reduction of NO_x with NH₃

The performances of Mn-W/TiO₂ catalyst for selective catalytic reduction (SCR) of NO with NH₃ and its resistance to different concentrations of SO₂ at various temperatures were investigated. The results suggest that WO₃ can increase the active sites and enhance the strength of acid. It is an excellent promoter of MnO_x/TiO₂. The NO_x conversion ranges from 80.3% to 99.6% during 100°C to 350°C at gaseous hourly space velocity (GHSV) 18 900 h?1, while N₂ product selectivity yields 100%~98.7% over Mn-W/TiO₂. The NO_x conversion maintains 98.5% at 120°C in presence of 0.01% SO₂ and 6% H₂O. The impact on catalytic activity will disappear if the temperature rises over 250°C with SO₂ concentration above 0.01%. At 300°C the NO_x conversion can reach to 99% as high as the commercial V-W/TiO₂ catalyst's level with 0.07% SO₂ in the stream gas. The Mn-W/TiO₂ shows excellent performance for SCR NO with NH₃ and it is the one of best catalysts with strong resistance to SO₂ by now. It was found that the impact of SO₂ is reversible and the activity will recover spontaneously with the rise of temperature.