Effect of metal ions doping (M = Ti4+, Sn4+) on the catalytic performance of MnOx/CeO2 catalyst for low temperature selective catalytic reduction of NO with NH3

Abstract Ceria-based solid solutions were synthesized and used as supports to prepare MnO x /Ce 0.8 Ti 0.2 O 2 and MnO x /Ce 0.8 Sn 0.2 O 2 catalysts (Mn/CeTi and Mn/CeSn) for low temperature selective catalytic reduction of NO by NH 3 . The effects of Ti or Sn doping on the catalytic performance of MnO x /CeO 2 catalyst were investigated. Experimental results show that doping of Ti or Sn increases the NO removal efficiency of MnO x /CeO 2 . The NO conversion of Mn/CeTi catalyst is more than 90% at temperature window of 175–300 °C under a gas hour space velocity of 60,000 mL g −1  h −1 . Modified catalysts are also found to exhibit greatly improved resistance to sulfur-poisoning. Characterization results indicate that doping of Ti or Sn brings about catalysts with higher BET surface area, enhanced oxygen storage capacity and increased surface acidity. X-ray photoelectron spectroscopy (XPS) analysis of spent catalysts following SCR reaction in the presence of SO 2 verify that the loss of surface Mn species was inhibited by doping of Ti, which contributes to extend the sulfur durability. The SCR activity is considered as well to be promoted by the dual redox cycles in Mn/CeTi (Mn 4+  + Ce 3+  ↔ Mn 3+  + Ce 4+ , Ce 4+  + Ti 3+  ↔ Ce 3+  + Ti 4+ ) and Mn/CeSn (Mn 4+  + Ce 3+  ↔ Mn 3+  + Ce 4+ , 2Ce 4+  + Sn 2+  ↔ 2Ce 3+  + Sn 4+ ) catalysts.