Nanoporous titania-alumina mixed oxides - an alkoxide free sol-gel synthesis

A series of x TiO2 (1 - x) Al2O3 mixed oxides with different molar ratio, x = 0.95, 0.90, 0.80, 0.70 and 0.60 (where x = TiO2/TiO2+Al2O3), have been prepared by a non-alkoxide sol-gel route from a mixture of titania and boehmite sol derived from titanyl sulfate and aluminium nitrate. It was found that alumina introduces structural and textural modification to titania and the resultant properties of the mixed oxides vary with the composition. The anatase to rutile phase transformation temperature increased with increasing mole percent of alumina. The BET surface area of the gels, after degassing at 200 degreesC, was in the range 375-715 m(2) g(-1) with total pore volume in the range 0.2116-0.3363 cm(3) g(-1). Calcination of the gels at high temperature decreases the surface area. However, the surface area of mixed oxide gel was about 80% higher than that of pure titania. Titania-alumina mixed oxide with a composition of x = 0.60 was able to keep a specific surface area of 108 m(2) g(-1) and 0.1466 cm(3) g(-1) total pore volume after calcination at 800 degreesC for 3 h. The pore size distribution of samples derived by BJH method showed that all mixed oxide samples contain pores in the range 2 to 17 nm. (C) 2004 Elsevier B.V. All rights reserved.