Effect of Mg, Ca and Ba on the Pt-catalyst for NOx storage reduction

A set of catalysts was prepared to improve the activity of the Ba-Pt/γAl2O3 catalyst in the NOx storage reduction (NSR), by replacing Ba with Mg or Ca, but maintaining constant the moles of alkaline–earth element in order to keep the number of storage sites constant. The catalysts were prepared by impregnating first 1.0 wt.% Pt and then the alkaline–earth cations (Ca, Mg and/or Ba) on a commercial γAl2O3 (Sasol, D). Tests were carried out in a wide temperature range (100–500 °C), thus evidencing the specific role of each different alkaline–earth element. Both the activity and the resistance to SO2 poisoning in the catalysts were different and the alkaline–earth cation with lower electronegativity registered the strongest deactivation. A new catalyst with high activity and resistance to deactivation by SO2 was obtained by co-impregnating Ba and Mg on γAl2O3 (1.5Mg8.5Ba-1Pt/γAl2O3).