Multitechnique study of the interaction of SO2 with alumina-supported SnO2 catalysts for lean NOx abatement

This study deals with the physicochemical characterization of SO2-treated alumina-supported tin dioxide surfaces as a function of the tin oxide loading. Three analysis techniques were used: Fourier transform infrared spectroscopy (FTIR), XPS and adsorption calorimetry. The two types of spectroscopies allowed the identification of the nature of the sulphur-containing species after SO2 adsorption. The determination of the quantities of adsorbed sulphur-containing species was made possible by adsorption calorimetry and XPS. At 353 K the SO2 uptake was minimum for 8 wt.% Sn and the major species were SO32-. When increasing the Sn loading, the weakly adsorbed SO2 species vanished whereas the amounts of sulphite species increased. Above 12 wt.% Sn, the presence of sulphate species increased, with a maximum for bulk SnO2. After desorption at 673 K, the SO2 uptake was considerably decreased and each sample presented more SO42- than SO32- species.