Physicochemical characterization of MoO 3-NaY zeolite catalysts

Abstract

A series of Mo-impregnated NaY zeolite catalysts, with a Mo loading in the range 1–15 wt%, MoO 3, have been studied by X-ray diffraction, transmission electron microscopy, ir and diffuse reflectance spectroscopy, temperature-programmed reduction, specific surface area, water content, and extraction measurements, in order to characterize them structurally. The crystallinity, specific surface area, and water content of the Mo-NaY were found to decrease almost linearly with increasing Mo loading. These effects were accompanied by an increasing perturbation of the zeolite framework. The ir spectra and, particularly, the diffuse reflectance spectra suggest that Mo is predominantly present as a tetrahedrally coordinated MoO 4 2− species, presumably within the zeolite cavities. The Mo extraction and temperature-programmed reduction results revealed the existence of a strong interaction between Mo species and zeolite, which apparently decreases with increasing Mo loading.