High temperature stability of anatase in titania–alumina semiconductors with enhanced photodegradation of 2, 4-dichlorophenoxyacetic acid

•Synthesis of titania–alumina materials with the modified sol-gel method.•Alumina stabilizes the anatase structure at 800°C.•The pore and crystallite size are key parameters in a photodegradation test.•Nucleation and growth control of structural phases through thermal treatments results in a more active materials. 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°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, Eg 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.