Isomorphous substitution of ruthenium in MFI framework using the oxo-anions ruthenate(vi) and perruthenate(vii)

Abstract

The oxo-anions: ruthenate(VI) and perruthenate(VII), as primary sources of ruthenium, have been investigated in the hydrothermal synthesis of zeolite ZSM-5. Crystalline material with ruthenium incorporated into lattice sites was isolated from starting gels containing up to 0.1 mole fraction Ru₂O₃/SiO₂. There are no previous reports of the isomorphous replacement of aluminium by ruthenium in MFI-type zeolites. X-Ray diffraction, infra-red spectroscopy, chemical analysis, electron microscopy, and X-ray photoemission spectroscopy (XPS) all provide evidence for the presence of framework ruthenium. The development of new IR absorption bands in the asymmetric and symmetric Si–O–T stretching region, and the shift to lower wavenumbers is accompanied by an increase in the interplanar spacings and unit-cell dimensions with increased Al replacement. A change in morphology is also observed.