STUDY OF CERIA SULFATION

The oxidative adsorption of SO2 on ceria has been studied using gravim etry and IR spectroscopy. SO2 oxidation gives rise to two main types o f sulfates: surface and bulklike species. The former are characterized by IR bands in the 1400-1340 cm(-1) range while the latter lead to a very broad band near 1200 cm(-1). Their relative amount depends on the sample surface area and the total sulfate amount formed. The sulfate thermal stability and reducibility are compared to those of sulfate sp ecies formed on other oxides. It is also found that oxidation of SO, a dsorbed species into sulfate can occur without O-2 addition, a concomi tant ceria reduction then being evidenced by UV-visible reflectance sp ectroscopy.