Study On The Reaction Intermediates For Propylene Epoxidation On TS-1

Propylene epoxidation on TS-1using H2O2solution as oxidant is a environmentally benign catalytic process. The high selectivity and yield of propylene oxide can be achieved under mild reaction condition. Therefore, the study on the TS-1/H2O2-H2O system is important for both theory and application.In this study the nano-scale TS-1was synthesized with hydrothermal-synthesis-method, and the TS-1/H2O2-H2O system was investigated by using in-situ UV-Raman spectroscopy. During the aging process of the TS-1/H2O2-H2O system a feature at837cm-1, which has been assigned to the O-O stretching mode in the Ti-OOH (η2) species, was observed in Raman study for the first time. The amount of the Ti-OOH (η2) species is found deeply influenced by water content. The results obtained by gas chromatography-Raman spectrometry (GC-Raman) during propylene epoxidation process shows the direct relationship between the amounts of Ti-OOH (η2) species and the generation rate o fPO, indicating that the6-coordinated Ti-OOH (η2) intermediates are important active sites for propylene epoxidation. In addition, Raman spectra show the co-existence of Ti-O-CH3moiety and6-coordinated Ti-OOH (η2) species. GC-Raman results show that the6-coordinated Ti-OOH (η2) species which may contain one CH3OH mollecule (or one H2O) are active sites in the methanol-included epoxidation reaction process.