Silica nanoparticles-attached titania (TiO2@SiO2) was prepared by modification of the surface of titania (TiO2) with octadecyltrichlosilane (OTS) as a source of silica. The attachment of silica was achieved through repeated deposition–hydrolysis–calcination of OTS on the surface of titania particles. For comparison, the silica–titania composite (TiO2–SiO2) containing titania and silica agglomerated particles was also prepared. The physicochemical characteristics of TiO2@SiO2 and TiO2–SiO2 particles are experimentally studied by X-ray diffraction (XRD), UV–vis diffuse reflectance (UV–vis DR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX) and 29Si solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) techniques. The effect of silica attaching on activity of titanium surface species has been tested in the liquid phase epoxidation of 1-octene to 1,2-epoxyoctane with aqueous hydrogen peroxide. It is demonstrated that the surface attachment of titania with silica nanoparticles enhances the epoxidation activity of titania. UV–vis DR spectra of the solid particles showed the increase in intensity of the tetrahedral titanium in TiO2@SiO2. This indicates the occurrence of the transformation of some of the octahedral titanium to the tetrahedral structure during silica attaching of TiO2@SiO2 in which titanium tends to bond with –Si(OH)2(OSi)2 to make it stable in tetrahedral form. Considering that the tetrahedral titanium was considered the most active species in epoxidation of alkene, it can be concluded that a high epoxidation activity of TiO2@SiO2 particle was related to the modification of the local environment of titanium surface species by attachment of silica nanoparticles.
- Silica nanoparticles-attached titania; Titanium surface species; Surface modification
Available at: http://works.bepress.com/hadi_nur/2/