Improved sulfur resistance of Pt-Sn/γ-Al2O3 catalysts for C3H8-NO-O2 reaction under lean conditions due to Pt-Sn surface interactions

The selective catalytic reduction (SCR) of NO with C3H8 was studied over unsulfated and pre-sulfated 1% Pt/γ-Al2O3, and 1% Pt-2% Sn/γ-Al2O3 catalysts. Carbon residues deposited were evaluated on all samples, after 12 h of C3H8-NO-O2-SO2 reaction. Pre-sulfated 1% Pt-2% Sn/γ-Al2O3 catalyst showed a high resistance on deactivation by sulfur and on carbon residues deposition. Results are explained on basis of X-ray photoelectron spectra (XPS) showing that tin addition to 1% Pt/γ-Al2O3 resulted in (i) lowering the sulfates generated over the surface of the catalyst; (ii) preventing Pt particles from sintering during sulfation process; and (iii) decrease in the number of sites available on the alumina for carbon residues species to be adsorbed.