Super/subcritical fluid extractions for preparation of the crystalline titania

Various extraction techniques which use fluids in super/subcritical state (CO(2). H(2)O, CH(3)OH) were used for the preparation of crystalline TiO(2) from surfactant-mediated titania organogels (the amorphous reaction intermediate products of surfactant-mediated sol-gel synthesis). Crystallinity, purity and texture of TiO(2) powders (titania aerogels) were studied in detail for different treatment modes of titania organogels. Suitable combinations of extraction solvents and extraction temperature and pressure were considered for synthesis of TiO(2) powder crystalline phase (anatase) with high specific surface area and purity (carbon content <0.1 wt.%). Optimum results were achieved by combined extraction procedures subcritical water extraction and supercritical fluid extraction or pressurised liquid extraction. Moreover, the possible tuning of the TiO2 powder pore-size distribution by regulation of temperature at constant pressure for the combined subcritical water extraction and pressurised liquid extraction was found. (C) 2010 Elsevier B.V. All rights reserved.