Investigation of Pt/γ-Al2O3 catalysts prepared by sol-gel method -: XAFS and ethane hydrogenolysis

The physical and chemical properties of alumina-supported Pt prepared by sol-gel method were investigated using BET surface area measurement, hydrogen chemisorption, transmission electron microscopy, X-ray powder diffraction, and X-ray absorption fine structure (XAFS). The BET surface area, pore size, and pore volume of Pt/gamma-Al2O3 obtained from sol-gel method were similar to those of impregnated catalysts. The result of XAFS showed that the platinum particles consisted of 20 atoms, ca 1 nm, independent of the preparation method. However, the available metal surface area in the sol-gel catalysts for hydrogen chemisorption decreased by as much as 30%, compared to the impregnated catalyst. The turnover frequency of ethane hydrogenolysis reaction was considerably lower than that of the impregnated catalyst. Thus, we concluded that the platinum particles in the Pt/gamma-Al2O3 sol-gel catalysts were buried in the gamma-Al2O3. This burial of particles was the cause of a strong metal support interaction and resulted in high sintering resistance of metal particles at 873 K in air. (C) 1998 Academic Press.