The effect of hydrophilicity/hydrophobicity of TiO2-SiO2 composite aerogels in the epoxidation reaction

The TiO2-SiO2 composite aerogels were prepared via sol-gel synthesis followed by ambient pressure drying technology, and then hydrophobically modified via the surface silylation reaction. These materials were applied in the styrene epoxidation using H2O2 as the oxidant. The results show that no epoxide ring-opening and deep oxidation products were observed, maybe attributed to the weak acidity of them. For these samples, hydrophobic modification led to a decrease in the acidity and the amount of hydrated tetrahedrally coordinated titanium species which resulted in a drop of the selectivity for styrene oxide. The hydrated tetrahedrally coordinated titanium species plays an important role in the styrene epoxidation.