An investigation on the catalytic properties of titania–silica materials

Binary TiO 2 –SiO 2 mixed oxides display interesting catalytic properties which have not been attributed to the pure TiO 2 and SiO 2 . Many authors have proposed that Bronsted acidity is generated upon interaction of the two oxides. Recent results from our laboratories have demonstrated that high-purity crystalline and amorphous TiO 2 –SiO 2 mixed oxides do not possess Bronsted acidity, only Lewis acidity. We have investigated the catalytic properties for 1-butene isomerization up to 340 °C. High-purity TiO 2 , prepared with low temperature supercritical drying, has a high catalytic activity, close to that of the TiO 2 –SiO 2 . The reaction products obtained from TiO 2 and from TiO 2 –SiO 2 are identical and consist of linear butenes only, while Bronsted acid catalysts give rise to isobutylene and C 3 –C 5 hydrocarbons. These results suggest that nanoparticles of TiO 2 stabilized by SiO 2 are the active components of TiO 2 –SiO 2 . No evidence for Bronsted acidity in TiO 2 –SiO 2 has been found.