Highly Catalytic Epoxidation Of Olefins With Aqueous H₂O₂ Over Heterogeneous Peroxo-phosphotungstic Catalysts

The epoxidation is a kind of very important reactions,and the epoxy compounds or ring opening diols have shown important applications in chemical industry.Also,the epoxy compounds can be used as the intermediates in synthetic polymers,pharmaceuticals,fine chemical and biological materials.In recent years,some heterogeneous catalysts with anion resins as the carriers have been reported,but the preparation methods of these catalysts are relatively complex with the limited catalytic efficiency.The target of this work aims to develop a simple anion-exchange method for the preparation of high-efficiency catalysts on the epoxidation of large olefins.Firstly,D201,D261,D262,D296 and 201 anion resins were exchanged with peroxo phosphotungstic acid solutions of different P contents(0.70,0.78,0.84,0.99 and 1.23 wt%).Thus-prepared catalysts were characterized by X-ray diffraction(XRD),specific surface area and pore size analysis(BET),scanning electron microscopy(SEM),thermal gravimetric analysis(TG),the solid diffuse reflectance ultraviolet(UV-Vis),X-ray photoelectron spectroscopy(EDS).Thus-prepared materials possessed typical Keggin structures,irregular morphologies and high metal content.UV-vis,Raman and XPS spectra proved the high dispersionof peroxo phosphotungstic acid anions on the resin.Under the optimal conditions of 50 ?,6h and n(H2O2):n(olefin)ratio =1.2:1,using D201-PWAR(4)as the catalyst and acetonitrile as the solvent,the cyclohexene conversion was reached 92.4 mol%with 98.1%selectivity of epoxide.In addition,the recycling uses of the catalyst D201-PWAR(4)were studied,which proved recyclable stability of this catalyst.D261-PWAR catalyst showed the best activity for the mono-epoxidation of cyclododecatriene with H2O2 at 60 ? for 4h,in which the substrate conversion reached 72.6 mol%with 74.6%selectivity of mono-epoxide.In addition,this catalyst displayed highly catalytic efficiency for the mono-epoxidation of 1,5-cyclooctadiene with H2O2,in which the conversion of 1,5-cyclooctadiene was 16.2 mol%with 74.0%selectivity of mono-epoxide.However,for the mono-epoxidation of dicyclopentadiene with H2O2,D262-PWAR catalyst catalyzed the conversion of 85.2 mol%and the mono-epoxide selectivity of 85.7%at 60 ? for 6h.Finally,we discussed the preparation and catalytic activity of chloride-form anionic resin supported peroxo phosphotungstic acid catalysts,in which spherical resin had to be pre-treated with organic amine.Among these solid catalysts,PSC-3 exhibited the best activity for the mono-epoxidation of dicyclopentadiene with H2O2 to obtain 91.8 mol%conversion of dicyclopentadiene and 90.0%selectivity of mono-epoxide.