The incorporation of aluminum acetylacetonate as alumina source during the gelation of titanium alkoxide reduces the nucleation sites for the formation of large rutile crystals on temperatures ranging from 400 to 800 degrees C. As a result, the aggregation of anatase crystals is prevented at high temperature. A relationship among the specific surface area, pore size, energy band gap, crystalline structure and crystallite size as the most relevant parameters are evaluated and discussed. According to the results for the photocatalytic degradation of 2,4-dichlorophenoxyacetic acid, the specific surface area, pore size, E-g band gap are not determinant in the photocatalytic properties. It was found that the anatase crystallite size is the mores important parameter affecting the degradation efficiency. (C) 2013 Elsevier B.V. All rights reserved.