The Chemistry of Pt-NaY Zeolite Preparation

Raman spectroscopy and temperature programmed reduction experiments establish the chemical intermediates important to the formation of highly dispersed platinum clusters on a NaY-zeolite support. Calcination at 673 K decomposes the ion-exchanged Pt(NH 3 ) 4 2+ -NaY starting material to PtO/2H + -NaY which, upon reduction at 673 K, yields optimum metal dispersion in the NaY supercage cavities. Calcination at temperatures above ca. 773 K induces decomposition of PtO to yield Pt2 + cations which occupy sodalite cage sites. Migratory tendencies of the metal during reduction of cationic precursors Pt(NH 3 ) 4 2+ and Pt 2+ contribute to diminished metal dispersion in catalysts calcined to temperatures significantly below or above 673 K, respectively.