VOCs Degradation Performance of TiO2 Aerogel Photocatalyst Prepared in SCF Drying

Abstract: Titania (TiO2) aerogels were prepared by the sol-gel method using titanium(IV) chloride (TiCl4) and subsequent supercritical fluid drying (SCD) to avoid collapse of the original gel structure. The characteristics of titania aerogels with varying epoxide/TiCl4 ratios and amounts of water were analyzed using a BET surface analyzer, XRD, and FT-IR spectroscopy. VOCs, such as benzene, toluene, and m-xylene (BTX), were oxidized using the prepared titania aerogel; its performance was compared with that of commercially available TiO2 (P-25, Degusa). The surface area, pore volume, and average pore diameter of the titania aerogel formed using 1,2-epoxybutane as a epoxide were significantly smaller than those obtained using propylene oxide. The titania aerogels with 6 mol of epoxides had high surface areas, pore volumes, and average pore diameters. As a result of photo-oxidation, the conversion of benzene reached ca. 70 %; for the other reactants it reached ca. 60 %. The conversion of BTX increased as the inlet concentration decreased. The reactivity of titania calcined at 600 oC was greater than those of the sample calcined at 400 and 800 oC. Water is required as a reactant for the oxidation of VOCs; the continuous consumption of hydroxyl radicals required replenishment to maintain catalyst activity. The activity ratio increased with the reaction time when enough water was present in the reactor.

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