The synthesis of ZrO2/SiO2 nanocomposites by the two-step CVD of a volatile halogen-free Zr alkoxide in a fluidized-bed reactor

ZrO2/SiO2 nanocomposites with Zr loadings in the range 0.88 wt % to 12.2. wt % were prepared by a two-step metal-organic (MO)CVD process in a fluidized-bed reactor with the Zr alkoxide [Zr((OPr)-Pr-i)(2)(tbaoac)(2)] as the precursor. The high surface area of silica was hardly diminished by the deposition, and the deposited zirconia species were highly dispersed, as indicated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) investigations. The XPS data reveal a linear increase of the Zr surface concentration with increasing Zr loading. The high degree of dispersion is attributed to a strong interaction between the zirconia species and the support through the formation of Si-O-Zr bonds. Correspondingly, the intensity of the isolated silanol bands detected by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was found to decrease with increasing Zr loading.