Abstract
A series of TiO2–ZrO2/SiO2 nanocomposites were synthesized using a liquid-phase method and characterized by various techniques, namely, nitrogen adsorption–desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy, and photon correlation spectroscopy (PCS). It was revealed that the component ratio and calcination temperature affect the phase composition of nanocomposites. Composites TiZrSi1 (TiO2:ZrO2:SiO2 = 3:10:87) and TiZrSi2 (10:10:80) calcined at 1100 °С demonstrate the presence of t-ZrO2 crystallites in TiZrSi1 and ZrTiO4 phase in TiZrSi2. The samples calcined at 550 °С were amorphous as it was found from XRD data. According to the Raman spectra, the bands specific for anatase are observed in TiZrSi2. According to XPS data, Zr and Ti are in the highest oxidation state (+4). Textural analysis shows that initial silica is mainly meso/macroporous, but composites are mainly macroporous. The particle size distributions in aqueous media showed a tendency of increasing particle size with increasing TiO2 content in the composites.
Highlights
Disperse oxide composites are of great interest for individual applications as heterogeneous catalysts with an adjustable set and strength of surface active sites [1,2,3,4] and as a part of organic–inorganic composites and polymer fillers [5, 6]
In the present study, highly disperse silica-supported titania–zirconia nanocomposites were synthesized by a liquid-phase method
The X-ray diffraction (XRD) measurements indicated the presence of ZrTiO4 and anatase in TiZrSi2 and tetragonal zirconia in TiZrSi1 calcined at 1100 °C
Summary
Disperse (nanoparticulate) oxide composites are of great interest for individual applications as heterogeneous catalysts with an adjustable set and strength of surface active sites [1,2,3,4] and as a part of organic–inorganic composites and polymer fillers [5, 6]. Combination of dissimilar oxides allows to create surface active sites, which are absent in individual components [7]. The nature of active sites of solid acid catalysts is defined by mobile surface protons generating Brønsted acid sites and coordinately unsaturated cationic centers as Lewis acid sites [8]. Much attention has been focused on development of binary or ternary metal oxides as heterogeneous catalysts [1].
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