Influence of calcination temperature on the structure and properties of Al2O3 as support for Pd catalyst

We investigated the influence of the calcination temperature on the structural properties of Al2O3 and how the resultant Al2O3 support affects the characteristics of Pd/Al2O3 catalysts. Al2O3 pretreated at different calcination temperatures ranging from 500 A degrees C to 1,150 A degrees C, was used as catalyst supports. The Pd/Al2O3 catalysts were prepared by a deposition-precipitation method using a pH 7.5 precursor solution. Characterization of the prepared Pd/Al2O3 catalysts was performed by X-ray diffraction (XRD), N-2-physisorption, CO2-temperature programmed desorption (TPD), CO-chemisorption, and field emission-transmission electron microscopic (FE-TEM) analyses. The CO-chemisorption results showed that the Pd catalyst with the Al2O3 support calcined at 900 A degrees C, Pd/Al2O3 (900), had the highest and most uniformly dispersed Pd particles, with a Pd dispersion of 29.8%. The results suggest that the particle size and distribution of Pd are related to the phase transition of Al2O3 and the ratio of isolated tetrahedral to condensed octahedral coordination sites (i.e., functional groups), where the tetrahedral sites coordinate more favorably with Pd.