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 (XCO2) 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.