Effect of the Preparation Method (Sol-Gel or Hydrothermal) and Conditions on the TiO(2) Properties and Activity for Propene Oxidation

Since the two most commonly used methods for TiO(2) preparation are sol-gel (SG) and hydrothermal (HT) synthesis, this study attempts to compare both methods in order to determine which one is the most suitable to prepare photocatalysts for propene oxidation. In addition, this work studies how the concentration of the HCl used for hydrolysis of the TiO(2) precursor affects the properties of the obtained materials. Also, the effect of avoiding the post-synthesis heat-treatment in a selection of samples is investigated. The photocatalysts are characterized by XRD, N(2) adsorption-desorption isotherms and UV-vis spectroscopy, and the study tries to correlate the properties with the photocatalytic performance of the prepared TiO(2) samples in propene oxidation. TiO(2) materials with high crystallinity, between 67% and 81%, and surface area (up to 134 m(2)/g) have been obtained both by SG and HT methods. In general, the surface area and pore volume of the TiO(2)-HT samples are larger than those of TiO(2)-SG ones. The TiO(2)-HT catalysts are, in general, more active than TiO(2)-SG materials or P25 in the photo-oxidation of propene. The effect of HCl presence during the TiO(2) synthesis and of the post synthesis heat treatment are much more marked in the case of the SG materials.