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

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 Cr2O72- 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 alpha-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 mu m. 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 Cr2O72- 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 alpha-Cr2O3.