Recovery and Recycling of Ti Supported Bimodal Mesoporous Catalysts Prepared via Ship-in-a-bottle Method in the Epoxidation of Cyclohexene

Ti/BMMs (Ti supported bimodal mesoporous silica) catalysts have been prepared via self-assembly route combined with ship-in-a-bottle method. The recovery and recycling performances of Ti/BMMs were investigated in the epoxidation of cyclohexene. In order to the evaluate the regeneration methods and to examine the deactivation behaviors, the deactivated Ti/BMMs catalysts were washed in chloroform or calcinated at 450 °C for 6 h and then activity of the recovery catalysts were examined. Meanwhile, the structure features and surface properties of the regenerated catalysts were characterized by X-ray diffraction, N2-sorption analysis, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, UV visible spectroscopy and X-ray photoelectron spectroscopy. The results showed that the typical bimodal mesoporous structure of recycled Ti/BMMs catalysts was still maintained, and the phenomenon of Ti leaching during the catalytic process and recovery was negligible. In particular, spectroscopic observations indicated that the effects of the regeneration methods on the tetrahedrally-coordinated Ti species and catalytic deactivation were remarkable. The main reasons were related to the polarities of used solvents during recovery tests, the environment medium of adsorbed water inside mesopore channels and the deposition of bulky molecules of by-products on the mesoporous surface.

The recovery and recycling properties of Ti/BMMs mesoporous catalysts were investigated by means of various characterizations and epoxidation of cyclohexene. The deactivated Ti/BMMs catalysts were regenerated with the different recycle times by washing in chloroform or calcinations at 450 °C. The results showed that calcination is an effective approach to regenerate Ti/BMMs catalyst, which is not only beneficial to remove sediment inside the mesoporous channels, but also to prevent the leaching or transforming of the tetrahedrally-coordinated Ti species.Figure optionsDownload as PowerPoint slide