The roles of different titanium species in TS-1 zeolite in propylene epoxidation studied by in situ UV Raman spectroscopy. Issue 1 (25th November 2015)

• Record Type: Journal Article
• Authors: Xiong, Guang; Cao, Yuanyuan; Guo, Zhendong; Jia, Qianying; Tian, Fuping; Liu, Liping
• Is Part Of: Physical chemistry chemical physics. Volume 18:Issue 1(2016)
• Page Start: 190
• Page End: 196
• Publication Date: 2015-11-25
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c5cp05268h
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : The role of different titanium species in TS-1 zeolite has been investigated by gas chromatography-Raman spectrometry during the propylene epoxidation process. 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 ( η 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 ( η 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.