Synthesis, Characterization And Catalytic Properties Of Titania-silicalite Complez Materials

TS-1 zeolite with Ti(IV) in the framework of silicalite-1 is a new kind of zeolite catalyst developed in 1980s. It was found that TS-l has unique catalytic properties. It can activate aqueous hydrogen peroxide to oxide many organic compounds selectively. These oxidation reactions carried out at ambient conditions (near room temperature) with little byproducts. The titanium silicalite catalysts have attracted much attention and many environment-friendly selective-oxidation processes have been developed based on TS-1-H2O2 oxidation system.However the synthesis of standard TS-l requires large amount of expensive reagents and severe operation conditions. The standard TS-l is difficult to handle due to its small crystal size. To overcome these problems and to improve the catalytic property of this kind of the catalysts, researches have been made to search for the new synthesis routes of titanium silicalite and to develop the titanosilicate catalysts with new active catalytic structure. Add a new material to hydrothermal synthetic gel of titanium silicalite to prepare a complex catalyst in situ is a new research area. Prepare the TiO2-SiO2 mixed oxide with highly dispersed titanium species through sol-gel process is also a hot research area.The dissertation studies the above new research area and provided some new catalysts with novel catalytic properties. (1) Prepare TS/TiO2complex catalyst through in situ plantingSome amorphous Ti02 was prepared through hydrolyzation of TiCl4 or TBOT. The amorphous TiO2 was added to the synthetic gel composed of tetrapropylammonium bormide (TPABr), silica sol. a titanium source and a base solution. In hydrothermal crystallization condition, the titaniumsilicalite was growing on the amorphous TiO2. The complex catalysts TS/Ti02 in witch the titania and silicalite have strong interaction have new active catalytic structure.The X-ray diffraction (XRD) patterns of the TS/TiO2 catalysts exhibit lowcrystallinity. The triple peaks at 2 6 23 to 25 degrees indicate the catalysts contain MFI structure. However the triple peaks are small and the crystallinity calculated by the triple peaks is only about 30 to 40%. The XRD patterns of the calcined samples exhibit a new peak at 2 6 26 degrees which means the amorphous titania transform to anatase after calcined at 540 . The IR spectra of the samples show a strong adsorption band at 960 cm-1. The IR crystallinity calculated by 1550/I4SO is high- The C13-CP-MAS NMR of the as-synthesized sample show the typical signal of occluded TPA molecule in the micro pore of MFI zeolite. The high-resolution TEM photographs of the catalyst samples show the nanostructured titanosilicate contained in the titania substrate.The RF-UV spectra of TS/TiO2 exhibit an adsorption peak at 250nm which is different from the framework titanium adsorption of the common titanium silicalite which peaks at 210-220nm. TS/TiO2 contains a new kind of active titanium species. The .UV-Raman spectra of TS/TiO2 do not exhibit the resonance signal-of framework titanium at 1120cm-1 that also means the catalyst contains new catalytic structure.The TS/TiO2 catalyst is applied to catalyze the epoxidation of propylene witfe atpieous hydrogen peroxide. The initiated catalytic activity of the catalyst is higher than the standard TS-1 catalyst. The conversion of the hydrogen peroxide is higher than 95% and the selectivity of the propane oxide is higher than 95% at some conditions. The amorphous titania exhibits high activity in decomposition of H2O2 while the calcined titania (anatase) dose not decompose H2O2 but also has little catalytic activity for epoxidation reactions. The active catalytic center in TS/TiO2 is the highly dispersed non-framework titanium on the nanostructured MFI zeolite. TS/TiO2 was also applied to oxide ethylenebenzene .vwth H2O2 TS/TiO2 catalyst shows different product selectivity compared with The TS-1 catalyst.However thd catalytic activity of the TS/TiO2 in the ammoxidation of cyclohexandne and hydroxylation of phenol is very low compare...