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Synthesis Of Titanium Silicalite-1 As Catalyst For The Epoxidation Of Propylene

Posted on:2011-02-16Degree:MasterType:Thesis
Country:ChinaCandidate:L WangFull Text:PDF
GTID:2121330338481229Subject:Chemical processes
Abstract/Summary:PDF Full Text Request
Titanium silicalite (TS-1) can catalyze the epoxidation of propylene to propylene oxide. This reaction has many advantages, such as mild reaction conditions, using aqueous H2O2 as oxidant, high reaction rate, high selectivity, no pollution. As a green technology to replace the traditional technologies, it obtains attention of researchers, and has been extensively studied.In this work, TS-1 is synthezised using ethyl silicate, butyl titanate as materials and self-synthesized tetrapropylammonium hydroxide as the template. The structure and morphology of TS-1 are characterized by XRD, XPS, FT-IR, UV-Vis, SEM, TGA, BET, etc. The catalytic properties of TS-1 are investigated for the reaction of propylene epoxidation.First, it has been found that addition of some substances such as sodium carbonate, sodium chloride, ammonium acetate, etc, in the reaction system to neutralize the acid sites on TS-1 effectively improves the catalytic properties of TS-1. while the conversion of hydrogen peroxide is kept at around 98.0%, the propylene oxide selectivity increases from 84.1% to 97.7%.Secondly, the factors such as SiO2/TiO2 molar ratio, C/TPAOH molar ratio, Br-/TPAOH molar ratio, TPAOH/SiO2 molar ratio influencing on the physicochemical properties and catalytic properties of TS-1 are systematically investigated. The results show that the titanium in TS-1 synthezised at SiO2/TiO2 ratio of 70 exists in the form of framework titanium and its catalytic activity is excellent, with the hydrogen peroxide conversion of about 98.0% and the propylene oxide selectivity of 91.8% being obtained; addition of a trace amount of C inhibites the formation of non-framework titanium and improves catalytic properties, with hydrogen peroxide conversion remaining at around 98.0%, the propylene oxide selectivity increased from 84.1% to 97.7%; addition of a trace amount of Br- does not improve the catalytic properties of TS-1; increasing the template content decreases the particle sizes of TS-1 from around 200 nm to around 100 nm, but does not improve the catalytic properties of TS-1.
Keywords/Search Tags:titanium silicalite, propylene, propylene oxide, reaction additives, metal ion
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