SYNTHESIS AND CHARACTERIZATION OF SILICA-SUPPORTED PEG-400 Mo(VI)COMPLEX AND ITS CATALYTIC ACTIVITIES IN EPOXIDATION OF CYCLOHEXENE

Polyethylene glycol-400(PEG-400)grafted in silica(SiO 2)support as macromolecule ligand was synthesized, and the structure of the ligand was characterized by IR spectroscopy.The complex of silica-supported PEG-400 and molybdenum(Ⅵ)dioxo(2,4-pentanedione)[shortened form,SiO 2-PEG-Mo(Ⅵ)]was for the first time synthesized and characterized by infrared spectroscopy.The possible structure of the complex was discussed.As a catalyst, SiO 2-PEG-Mo(Ⅵ)complex was used in epoxidation process of cyclohexene,and its catalytic activity and selectivity was also investigated.Experimental results showed that the complex possessed excellent activity and selectivity for epoxidation of cyclohexene.A new analysis method of the amount of Mo in the catalyst and the analysis of epoxycyclohexane by gas chromatography were set up.For n(t-BuOOH) = 0.1 mol,n()∶n(t-BuOOH)=3.5∶1,the volume of solvent was about 10 ml, reaction temperature 80 ℃,reaction time 60 min,and the amount of SiO 2-PEG-Mo(Ⅵ)complex catalyst was 0.5 g.In this reaction condition, based on t-BuOOH,the yield of epoxycyclohexane was more than 99.2%,the purity of epoxycyclohexan was about 99.5% by GC analysis.The catalyst recycled for 3 times still possessed high catalytic activity and selectivity,and the yield of cyclohexene oxide approached 99% in the above-mentioned reaction condition.