Supported Re and Mo oxides prepared using binuclear precursors: synthesis and characterization

Rhenium and molybdenum oxomethoxide complexes Re2O3(OMe)(6), ReMoO2(MeO)(7), and Mo2O2(OMe)(8) were used as precursors to prepare highly dispersed mono and bimetallic oxide species supported on the microporous NaY zeolite and mesoporous SiO2 and Al2O3. The prepared materials were characterized by the use of FTIR, NH3-TPD, and H-2-TPR techniques. It was shown that, upon loading into microporous zeolite, oxomethoxide complexes loose their ligands so that just metal suboxide cores remains in the intracrystalline voids as the nanosized oxide clusters. The obtained clusters reveals both acidic and redox properties. The maximum amount of NH3 adsorbed per bimetallic species could be used as a characteristic of both availability of acid sites and oxide dispersion. Reducibility of these species depends strongly on both their location in the matrix and the size. The matrix texture also affects the transitions between different valent states of Re and Mo as well as the metal reduction extent. (C) 2004 Elsevier B.V. All rights reserved.