Studies On Immobilization Of Titanium Tartrate Complexes Over The Supports And Catalytic Properties For The Epoxidation Of Cinnamyl Alcohol With TBHP

Ti tartrate complex has been successfully grafted onto mesoporous silicas HMS and macromolecule polymer (PSt-PEG) or encapsulated into microporous NaY zeolite by chemically bonding or "ship in bottle" methods. FT-IR , UV-Vis diffuse reflection spectra and N2 volumetric adsorptions were adopted to characterize these catalysts. The epoxidation of cinnamyl alcohol was employed to check the catalytic performances of these catalysts. The result as follows:Comparing with the Ti loading of three catalysts, the measured Ti loading was the highest on the Ti tartrate grafted HMS samples as a result of the plenty of surface hydroxyls of HMS support, and the lowest on the Ti tartrate grafted PSt-PEG samples. The UV-Vis diffuse reflection spectra confirmed that Ti sites anchored the supports was the mixture coordination states with tetrahedron>, pentahedron and octahedron, but the Ti tartrate encapsulated NaY was mainly focus on the coordination states of pentahedron and octahedron. FT-IR confirmed that the exchange of Ti complexes with the surface hydroxyls of the HMS caused the distortion of the supports Si-04 tetrahedron and resulted in the appearance of a weak adsorption band near 960cm ' in their IR spectra. While there was not this absorption band in the IR spectra of the Ti tartrate encapsulated NaY samples. This indicated that titanium tartrate has not been chemically grafted to NaY but encapsulated in the super cage of NaY. There was a ligand' s carbonyl band at 1740cm-1 in the IR spectra of all fresh and cycling samples, this indicated that Ti tatrate complexes could be steadily embedded these supports. The surface area and pore volume of HMS materials after Ti complexes grafting have been significantly reduced, further confirming the introduction of Ti complexes into the channels of HMS by chemically grafting.In catalyzing the epoxidation of cinnamyl alcohol withtetrabutyl hydroperoxide (TBHP), these kinds of catalysts showed the better catalytic activity and selectivity for the epoxides. There was better corresponding relation between the conversion of cinnamyl alcohol and Ti loading. Comparing with the catalytic activity of single Ti turnover number, it was found that Ti tartrate grafted PSt-PEG catalysts had the highest turnover number, this is mainly due to the substrate is easily access to the Ti sites anchored the organic carrier as result of it' s affinity to the organic carrier. Ti grafted HMS catalysts had the lowest turnover number and epoxidative selectivity, this is mainly due to Lewis acidity of the Ti complex anchored HMS may catalyze some by-reactions such as the polymerization of cinnamyl alcohol and ring-opening of epoxides and so on, because the HMS carrier is a dimension mesoporous structure, so it can not restrain these by-reactions and will lead the decreases on the catalytic activity and especially the selectivity. The excellent selectivity for the epoxides could be obtained the Ti tartrate encapsulated NaY catalysts, it is mainly due to the Na* located in the super cages and the particular microporous structure of NaY can efficiently restrain the by-reactions.The recovered catalysts can be recycled many times without significant loss of activity. These indicate that Ti tartrate complex has been steadily bond to HMS and polystyrene or encapsulated into microporous NaY zeolite.