OXIDATION OF REDUCED PLATINUM CLUSTERS IN PT-NAY

Raman spectroscopy and 129Xe NMR, in conjunction with hydrogen chemisorption and transmission electron microscopy, have been used to monitor the location and stability of metal clusters as a function of oxidation conditions for NaY-zeolite-supported platinum. After initial calcination and reduction of Pt-NaY, subsequent reoxidation at temperatures up to 873 K induces no additional agglomeration of the metal species. Different Pt-NaY systems exhibit cluster-size-dependent responses to reoxidation treatment, consistent with the greater reactivities expected for small metal particles compared to larger aggregates. We present a summary of platinum dispersal chemistry in NaY zeolite based on these and recent corroborative results. © 1993 by Academic Press, Inc.