EXAFS STUDY ON PD-PT CATALYST SUPPORTED ON USY ZEOLITE

Local structure around Pd and Pt in the bimetallic Pd-Pt catalysts sup ported on ultra stable Y (USY) zeolite (SiO2/ Al2O3=680) was investiga ted by an extended X-ray absorption fine structure (EXAFS) method duri ng oxidation, reduction, and sulfidation. The Pt L III-edge EXAFS spec tra showed that a new bond that was significantly different from Pt-Pt to Pt-Pd metallic bonds was formed in the bimetallic Pd-Pt (4:1) redu ced catalysts supported on USY zeolite. This new bond may reflect the ionic properties of Pt through the Pt-Pd interaction. Furthermore this new bond survived sulfidation indicating that the bond has a cationic property and sulfur-tolerance property. The Pt-Pd ionic interaction i n these catalysts allows some of the Pd metal to survive as metallic p hase. The existence of this metallic phase under sulfidation condition may result in high activity of Pd-Pt (4:1) catalyst supported on USY zeolite in the aromatics hydrogenation. (C) 1998 Elsevier Science B.V. All rights reserved.