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In-situ UV Raman Study On The Active Sites Of TS-1 Catalyst For Epoxidation Of Propylene

Posted on:2011-06-30Degree:MasterType:Thesis
Country:ChinaCandidate:Z ZhaoFull Text:PDF
GTID:2121360305956138Subject:Industrial Catalysis
Abstract/Summary:PDF Full Text Request
Propylene oxide (PO) is one of the most important chemical intermediates for the production of polyether polyol polymers, e. g. polyurethane. Currently, PO is produced mainly through chlorohydrin and hydroperoxidation processes. However, these processes suffer from the production of chlorinated by-products and stoichiometric co-products. The epoxidation of propylene with hydrogen peroxide using Titanium silicalite-1 (TS-1) catalyst is an environmentally friendly alternative route. For this reason, TS-1 has been one of the most extensively studied zeolitic materials. Much attention is focused on its active sites and reaction intermediant. This study focuses on the surface structure of TS-1 and absorption species of TS-1/H2O2/H2O system. In particular, for the first time, UV Raman spectroscopy is used to explore the active sites and reaction intermediants of TS-1 for epoxidation of propylene.TS-1 was synthesized using a conventional method, and characterized by Raman spectroscopy, X-ray diffraction (XRD) and Infared spectroscopy (FT-IR) techniques. The color of the sample turns to yellow after dosing H2O2/H2O on TS-1. Two new peaks at 617 and 875 cm-1 are appeared. They are assigned to symmetric stretching mode of Ti(O)2 and O-O stretching mode of H2O2/H2O solution being physisorbed into the zeolite channels. Under reaction condition the peak at 875 cm-1 shifts to 883 cm-1, indicating that the formation of TiOOH via the interaction of framework Ti4+ and physisorbed H2O2. In-situ UV Raman spectroscopic study shows that the intensity of 883 cm-1 decreases while that of 617 cm-1 increases with increasing the reaction time. Combining the results from GC it is concluded that TiOOH is the active site..
Keywords/Search Tags:in-situ UV Raman, the epoxidation of propylene, active sites, TS-1
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