Abstract: Using cumene hydroperoxide as an oxidant, the deactivation and regeneration of the Ti/HMS (titanium-containing hexagonal mesoporous silica) catalyst were studied for epoxidation of propylene to propylene oxide. The structure and surface species of the fresh and used catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and thermogravimetry analysis. The results indicated that the main reason for catalyst deactivation was that the active sites on the catalyst surface were covered by polymer molecules produced during the reaction. The catalyst deactivation was not due to the transformation of tetra-coordinated Ti species to hexa-coordinated, octa-coordinated, or even anatase species. Hot cumene washing could partly restore the catalyst activity, but the low-temperature carbon-burning could restore the catalyst activity nearly to the level of fresh one. Therefore, the deactivated Ti/HMS catalyst was renewable and its activity could be restored by a proper regeneration method.

Key words: titanium, HMS molecular sieve, deactivation, regeneration, propylene, epoxidation, propylene oxide