CLUSTERING OF PLATINUM ATOMS IN ZEOLITE EMT SUPERCAGE - COMPREHENSIVE PHYSICOCHEMICAL CHARACTERIZATION

Abstract

Hexagonal faujasite (EMT) has two types of supercage whereas cubic faujasite (FAU) presents only one type of supercage. Using the same treatment than that for Pt clusters in a cubic faujasite, e.g. Y zeolite, a highly dispersed Pt cluster supported on EMT zeolite was prepared. The size, location and structure of Pt clusters entrapped in EMT was investigated using Xe-129 NMR spectroscopy, xenon adsorption, hydrogen chemisorption, high resolution electron microscopy (HREM) and extended X-ray absorption fine structure (EXAFS). The results suggest that a Pt cluster consisting of 20-30 Pt atoms is formed within the three-windows supercage of EMT. The size of Pt clusters does not depend on the Pt content in EMT, when the Pt/EMT obtained by the ion exchange of Pt(NH3)(4)(2+) is calcined in flowing O-2 at 573 K and subsequently reduced in flowing H-2 at 573 K.