Promotion of Ag/H-BEA by Mn for lean NO reduction with propane at low temperature

Effects of adding manganese to Ag/H-BEA for selective catalytic reduction of NO_x with propane (C₃H₈-SCR) were investigated underalean-burn condition.Mnaddition significantly promotes the catalytic performance of Ag/H-BEA below 673 K. A Ag-Mn/H-BEA catalyst with equal metal weight of 3 wt % has the highest activity for C₃H ₈-SCR among samples with a different bimetal loading. Manganese is mainly present in the 3+and4+oxidation states inAg-Mn/H-BEAcatalysts.Themajor contributions of manganese suggested by the data presented in this paper are to catalyze the NO oxidation and stabilize silver in a dispersed Ag⁺ state. The presence of silver enforces the transformation of a certain amount of Mn³⁺ ions to Mn⁴⁺ ions. The activity of Ag-Mn/H-BEA decreases slightly at low SO₂ concentrations (0-200 ppm) but decreases significantly at high SO₂ concentrations (400-800 ppm). In the presence of 10% H₂O and 200 ppm SO₂, the inhibition of C₃H₈-SCR below 673 K is more significant than that at high temperature above 673 K. Ag-Mn/H-BEA is a promising catalyst for the removal of NO_x from diesel engine exhaust.