TRANSMISSION ELECTRON-MICROSCOPY AND ENERGY-DISPERSIVE X-RAY SPECTROSCOPY STUDIES OF PT-RE ALPHA/AL2O3 CATALYSTS/

A series of Pt/rAl2O3, Re/gamma-Al2O3, and Pt-Re/gamma-Al2O3 catalysts have been studied by transmission electron microscopy and energy disp ersive X-ray spectroscopy. It has been shown that rhenium was not allo yed with platinum, but widely dispersed on the surface of alumina. Two types of platinum were found: (i) three-dimensional metallic particle s, and (ii) small particles consisting of a few platinum atoms. Some a ggregation of the platinum particles occurred during use of the cataly sts in the reforming of octane. It is suggested that the interaction o f rhenium with the alumina support and therefore the modification to t he platinum play an essential role in promoting the enhanced stability and selectivity of these catalysts to cycloalkanes and aromatics in r eforming reactions. (C) 1994 Academic Press, Inc.