THE PLATINUM AGGLOMERATION IN THE (111)-TWIN PLANES OF THE ZEOLITE FAU

The preferred location of platinum clusters in the {111}-twin planes (TP) of zeolite NaY (FAU) has been observed by high-resolution transmission electron microscopy (HRTEM). The platinum was incorporated in the zeolite by ion exchange followed by oxidation and reduction. Samples from each of the three different synthesis stages were examined by HRTEM, ion exchange provides a homogeneous platinum distribution in the zeolite, and agglomeration of platinum in the TP was only observed after the oxidation. The HRTEM observations of platinum in the TP, from two independent directions, <110> and <211>, support the fact that the platinum clusters are intrazeolitic. HRTEM observations of ultrathin sections (<400 Angstrom), prepared by ultramicrotomy, prove that the Tps of the zeolite crystals are occupied with platinum.