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 NOx with propane (C3H8-SCR) were investigated under a lean-burn condition. Mn addition 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 C3H8-SCR among samples with a different bimetal loading. Manganese is mainly present in the 3+ and 4+oxidation states in Ag-Mn/H-BEA catalysts. The major 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 allow 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, from diesel engine exhaust.