NO Storage-reduction Reaction over Pt–Li2O/TiO2–Al2O3 Catalysts under SO2-containing Conditions

Abstract

The NO storage-reduction properties of 1 wt% Pt–10 wt% Li2O/TiO2–Al2O3 catalysts prepared by the impregnation and sol-gel methods were investigated in the presence and absence of SO2. The surface area and NO storage amount of catalysts were smaller for the Pt–Li2O/TiO2–Al2O3 catalyst than for the Pt–Li2O/Al2O3 catalyst. However, the Pt–Li2O/TiO2–Al2O3 sample with mixed oxide support achieved high NO removal efficiency for a long period, although the reduction of NO sorption amount by sulfur poisoning was comparable for all catalysts. These results revealed that the mixed oxide support in the catalyst is a key component for continuous NO removal. The preparation method affected the NO storage amount and the crystalline phases of catalysts. The strong diffraction peak of Li2TiO3 phase was observed in the XRD pattern of sample prepared by the impregnation method. The formation of Li2TiO3 weakened the basicity of the catalyst, resulting in decreased NO storage capacity under a SO2-free atmosphere and the enhancement of tolerance to sulfur poisoning.