CHARACTERIZATION OF PD-CEO2 INTERACTION ON ALUMINA SUPPORT AND HYDROGENATION OF 1,3-BUTADIENE

The influence of the preparation method and loading of CeO2 on the int eraction of Pd/CeO2/Al2O3 catalysts was studied. The materials were ch aracterized by temperature-programmed reduction, hydrogen chemisorptio n and X-ray photoelectron spectroscopy measurements. The 1,3-butadiene hydrogenation was used as a model reaction. The Pd-Ce interaction aff ected the reduction behavior of the catalysts. Temperature-programmed reduction (TPR) results showed that the presence of CeO2 shifts the re duction temperature of PdO to lower values, while palladium similarly facilitates the reduction of the cerium surface species. The hydrogen uptake decreased when increasing the ceria content. XPS results showed that the Pd/Al ratio decreased with CeO2 addition being affected by t he preparation method and content. The formation of catalytic sites at the interface of Pd-Ce was postulated from turnover frequency (TOF) r esults of the 1,3-butadiene hydrogenation. The number of these new sit es increases with the addition of ceria. The nature of these sites is discussed in terms of the influence on the selectivity in butadiene hy drogenation.