Preparation of titanium dioxide in the nano-spaces of activated carbon using carbon dioxide supercritical fluid as a solvent

Abstract

The penetration of titanium tetraisopropoxide (TTIP) dissolved in supercritical CO₂ into the nano-spaces of activated carbon was studied in terms of coating TiO₂ on a carbon surface. The amount of TiO₂, which was derived from TTIP through thermal decomposition, depended on the density of the solvent and the content of an entrainer, 2-propanol (IPA), in the CO₂. In the system without the entrainer, the amount of TiO₂ in the activated carbon pores increased with the solvent density. The addition of the entrainer to the solvent fluid also influenced the TTIP adsorption level. The molar fraction of CO₂ in the solvent (X_CO2) should be more than 0.9 at 393 K for the penetration of TTIP, above which only the supercritical phase existed in the system without any other liquid phases. These results suggested that a supercritical fluid is useful, and that control of the solvent content, density and treatment time should be important for the preparation of activated carbon/metal oxide composites.