Spherical TiO₂/Cr₂O₃ Composites Synthesized with the Use of Ion-Exchange Resins as a Template

Abstract

Two samples of TiO₂/Cr₂O₃ composites are synthesized in the form of spherical grains via the stagewise thermal treatment of ion-exchange resins preliminarily saturated with chromium Cr³⁺ cations and dichromate ${\text{C}}{{{\text{r}}}_{{\text{2}}}}{\text{O}}_{7}^{{2 - }}$ anions, and then coated with a film-forming titania-based solution. Calcination temperature regimes are set on the basis of a thermal analysis and determined by the type of ion-exchange resin selected as a template. The synthesized composites are generally composed of the α-Cr₂O₃ phase, and the content of the TiO₂ phase is less than 4%. The composites replicate the spherical shape of grains for the initial ion-exchange resins with sizes of 370 to 660 µm. The grains of the sample based on kaolinite adsorbing Cr³⁺ ions have a porous structure with bulbs and cavities. The anion-exchange resin-based sample grains have kinks and cracks over their surfaces due to a nonuniform distribution of adsorbed ${\text{C}}{{{\text{r}}}_{{\text{2}}}}{\text{O}}_{7}^{{2 - }}$ anions in the initial anion-exchange resin. The composites exhibit catalytic activity in the deep p-xylene oxidation reaction. The cation-exchange resin-based sample is more active, due apparently to the smaller accessible titania surfaces in the anion-exchange resin-based sample as a result of the formation of a solid Ti³⁺ solution in α-Cr₂O₃.