PtMo bimetallic catalysts supported on Y-zeolite: I. Characterization of the catalysts

Abstract Bimetallic PtMoY catalysts have been prepared by adsorption and decomposition of Mo(CO) 6 in a Y-type zeolite containing 10-A Pt particles trapped in the zeolite cages. Part of the Mo atoms are deposited onto the Pt particles which produces a weak increase of the particle size measured by CTEM and STEM and a progressive decrease of the amount of H 2 or CO chemisorbed on platinum. At high Mo contents these chemisorptive properties are completely masked. It was checked by XPS, X-ray absorption edge spectroscopy, and ir spectroscopy with CO and NO as probe molecules that the Pt particles are initially electron deficient but the electronic structure becomes similar to that of bulk platinum once the Mo atoms were added. This is probably because the Pt atoms are then shielded from the electron acceptor sites of the support. The Mo atoms bonded to Pt are probably in a low valence state, but there is a fraction of Mo not bonded to Pt, especially in the zeolite outer layers of Mo-rich samples, which is oxidized to Mo IV -Mo VI by oxido-reduction reactions with the zeolite protons.