A highly sulfur resistant Pt-Sn/γ-Al2O3 catalyst for C3H8-NO-O2 reaction under lean conditions

The selective catalytic reduction (SCR) of NO with C3H8 was studied over 1% Pt/γ-Al2O3, and 1% Pt-2% Sn/γ-Al2O3 catalysts. The SO2 effect on the catalysts activity was examined using pre-sulfated samples of the above catalysts and SO2-containing feeds. A high SO2 tolerance of 1% Pt-2% Sn/γ-Al2O3 pre-sulfated catalyst for C3H8-NO-O2 reaction was found. Above 200 °C, NO was converted mainly into N2 and N2O. Surface analysis of both unsulfated and pre-sulfated catalysts by X-ray photoelectron spectroscopy (XPS) revealed that Sn addition to 1% Pt/γ-Al2O3 prevents Pt particles from sintering during high temperature sulfation process. This fact suggests that a Pt-Sn/γ-Al2O3 catalyst can resist high temperature reactions during automotive exhaust control without losing Pt active area.