Excellent hydrocarbon tolerance of CeO2-WO3-SnO2 oxide catalyst for the NH3-SCR of NO

Abstract

The tolerance of NH3-SCR catalysts towards hydrocarbon compounds (HCs) is very important for their practical application on diesel vehicles. In this study, the HC resistance of CeWSnOx, V2O5-WO3/TiO2 and Cu-SSZ-13 catalysts was systematically investigated using propene, toluene and n-pentane as model HCs. Experimental results suggested that the fresh and hydrothermally aged CeWSnOx showed much better HC tolerance than the Cu-SSZ-13 and V2O5-WO3/TiO2. This property mainly originated from the strong HC oxidation capacity of the CeWSnOx due to Sn introduction, which significantly inhibited side reactions, including the HC ammoxidation and the carbon deposition reactions. In contrast, an undesired HC ammoxidation reaction occurred at medium temperatures over the Cu-SSZ-13 and at medium-high temperatures over V2O5-WO3/TiO2, especially in the presence of propene, accompanied by the emission of toxic HCN gas. The high HC tolerance of CeWSnOx gives it promise for application on heavy-duty diesel after-treatment systems in the future, especially those with the SCR-on-DPF or cc-SCR configuration.