Selective catalytic reduction of NO with NH₃ over Mn-based catalysts at low temperature

Three Mn-based catalysts of Mn/Ce-ZrO₂, Mn/P₂₅, and Mn/Al₂O₃ with different supports were prepared by impregnation method and were used in the selective catalytic reduction of NO with NH₃ (NH₃-SCR) at low temperature. The catalysts were characterized by XRD, NH₃-TPD and H₂-TPR and their activity at low temperature as well as the resistances towards H₂O and SO₂ were investigated. The results showed that Mn/Ce-ZrO₂ exhibits better activity at low temperature (100~160℃) than other two catalysts, while Mn/P₂₅ performs better at high temperature (160~220℃), which is related with the redox characteristics of the catalysts. Mn/Ce-ZrO₂ is more easily to be reduced at low temperature while Mn/P₂₅ has a larger reduction peak at higher temperature, as revealed by H₂-TPR. All of the three catalysts have a good resistance to H₂O; among them Mn/Ce-ZrO₂ exhibits the best resistance to SO₂ and H₂O, which should be attributed to the abundant acid sites and the instability of ammonia sulfate formed on the surface of Mn/Ce-ZrO₂.