STRUCTURE CHARACTERIZATION OF PLATINUM/ALUMINA, RHENIUM/ALUMINA, AND PLATINUM-RHENIUM/ALUMINA CATALYSTS

The structures of Pt, Re, and Pt-Re catalysts supported on alumina containing 0.14 wt% titania were studied in the stages of impregnation, calcination, and reduction by UV diffuse reflectance spectroscopy (DRS), temperature-programmed reduction (TPR), selected area electron diffraction (SAED), and carbon monoxide and hydrogen adsorption measurements. Both platinum and rhenium species interacted strongly with the support after calcination. It is suggested that the platinum species interacts more strongly with titania than with alumina, while the converse is true with the rhenium species. A Pt3Ti alloy was found in both the reduced Pt/Al2O3 and reduced Pt-Re/A12O3 catalysts. An Al(ReO4)3 complex was found in the Re/A12O3 catalyst which was reduced at 480°C. Pt(0), Re(0), and Pt3Ti coexist in the reduced Pt-Re/A12O3 catalyst and the surface concentration of Re(0) increases with the Re/Pt ratio. Hydrogen adsorption at a high temperature increases with increasing Re/Pt ratio. It is possible that this kind of hydrogen is responsible for the higher stability of the catalyst with a high Re/Pt ratio. © 1994 Academic Press, Inc.