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Indexed by:期刊论文

Date of Publication:2016-01-07

Journal:PHYSICAL CHEMISTRY CHEMICAL PHYSICS

Included Journals:SCIE、PubMed、Scopus

Volume:18

Issue:1

Page Number:190-196

ISSN No.:1463-9076

Abstract:Titanium silicalite (TS-1) zeolites with different titanium species were synthesized and characterized by ultraviolet (UV)-Raman, ultraviolet visible (UV-Vis) diffuse reflectance spectroscopies and by the NH3 temperature programmed desorption (NH3-TPD) method. The roles of different titanium species in TS-1 samples have been investigated by gas chromatography-Raman spectrometry (GC-Raman) during the propylene epoxidation process. For the first time, a positive correlation was found among the concentration of framework Ti species, the amount of active intermediate Ti-OOH (eta(2)) and the conversion of propylene by the in situ GC-Raman technique. The results give evidence that the framework titanium species is the active center and Ti-OOH (eta(2)) is the active intermediate. The presence of extra framework Ti species is harmful to propylene epoxidation. Furthermore, the amorphous Ti species has a more negative effect on the yield of propylene oxide (PO) than the anatase TiO2. The NH3-TPD results reveal that the amorphous Ti species are more acidic and thus should be mainly responsible for the further conversion of PO.