Preparation and characterization of high surface area mesoporous anatase obtained from TiCl3 hydrothermally

Samples of titania (anatase) were prepared via precipitation by ammonia from TiCl3 aqueous solutions at pH = 4.7. Autoclaving of precipitates, after pre-drying, was effected at 8 atmospheres for 2 or 6 h. Two pre-drying temperatures were assayed (100 °C and 300 °C). The synthetic mesoporous anatase possessed a specific surface area of 160 m2/g, and resisted rutilation up to 800 °C. Autoclaving resulted in fully hydroxylated surfaces (as determined by TGA), and the pre-drying at 300 °C produced a greater number of acidic hydroxyls as determined by equilibrium adsorption of NaOH. Texture analysis via adsorption of N2 at 77 K indicated that pre-drying at 100 °C produced network-pore structure, and fractal analysis (by FHH equation) indicated that the pore network is constituted by channels with a variable distribution of hydraulic radii, and rough walls. On the other hand, pre-drying at 300 °C resulted in plate-like particles in which the pore system is slit-shaped. The different pore structure caused the samples to respond differently to temperature, where the samples pre-dried at 100 °C showed a decrease in fractal dimension implying a decrease in the participation of pores of small volume. On the other hand, no detectable change in fractal dimension was noted in case of the sample pre-dried at 300 °C when calcined at temperatures up to 550 °C. In no case was a specific surface area or less than ∼100 m2/g obtained upon calcination at 550 °C.