Deactivation and regeneration of TS-1/SiO_2 catalyst for epoxidation of propylene with hydrogen peroxide in a fixed-bed reactor

摘要

TS-1/SiO_2 catalyst for the epoxidation of propylene with hydrogen peroxide in a fixed-bed reactor has been investigated. The catalyst activity decreases gradually with the online reaction time, but the selectivity of propylene epoxide is kept at about 93%. The fresh, deactivated and regenerated catalysts were characterized with X-ray diffraction, Fourier transform infrared spectro-scopy, ultra-violet-visible diffuse reflectance, Brunner-Emmett-Teller method and thermogravimetric analysis, and the deactivated catalyst was regenerated with H_2O_2/ methanol solution. Compared with the fresh catalyst, both the framework structure and the content of titanium in the framework of the deactivated and regenerated TS-1/SiO_2 catalysts were not changed. The major reason of the catalyst deactivation was the blockage of the channels of the catalyst by bulky organic by-products, which covered the active centers of titanium in TS-1. The deposited materials on the deactivated TS-1/SiO_2 catalyst could be removed by treatment with hydrogen peroxide/methanol solution or pure methanol; the higher the treatment temperature and the higher the concentration of H_2O_2 in methanol, the higher the extent of the regeneration. The regeneration treatment did not influence the product selectivity in the propylene epoxidation.