Effect Of Extraframework Titanium Species In TS-1Zeolite For Propylene Epoxidation

The different titanium species existing in titanium silicalite TS-1prepared by conventional hydrothermal method have been investigated by ultraviolet (UV)-Raman and ultraviolet visible (UV-Vis) absorption spectroscopies,NH3temperature programmed desorption (NH3-TPD) method and the epoxidation of propylene with diluted H2O2solution (30%) in Situ UV Raman Spectroscopic study. The UV-Raman and UV-Vis spectroscopies are the suitable means to characterize and analysize different titanium species in TS-1zeolite. The TS-1samples with different titanium species can be used to study in situ Raman study. The results obtained by gas chromatography-Raman spectrometry (GC-Raman) during the propylene epoxidation process give direct evidence that the framework titanium species is the active center, the amorphous Ti species is harmful for oxidation reaction and the anatase TiO2species has no influence for the selective oxidation. The NH3-TPD results reveal that the amorphous Ti species are the main factor in the enhanced acidity of TS-1. Acid treating method has been proved effective in improving the catalytic activity by the elimination of amorphous Ti species.