Epoxidation Of Styrene With Hydrogen Peroxide Over Cao Catalysts

Epoxyethylbenzene is an important industrial chemicals that have been used as chemicalintermediates. Catalytic epoxidation of styrene affords an interesting technology for theirproduction. With regards to this, the reaction of epoxidation of styrene to epoxyethylbenzenehas become a more popular research topic in the catalytic.The paper reports the effect of CaO on the epoxidation of styrene. In this paper,A seriesof CaO samples have been prepared by calcination of commercially available and synthesis ofcalcium salt precursors such as calcium acetate, carbonate, hydroxide, oxalate and these havebeen found to be effective for the epoxidation of styrene using hydrogen peroxide as anoxidant in the presence of acetonitrile. To determine the influence of the physicochemicalproperties and surface basicity on the catalytic activity the prepared CaO samples have beencharacterized using thermogravimetry （TG）, X-ray diffraction （XRD）, scanning electronmicroscopy （SEM）, N₂adsorption and temperature programmed desorption （TPD） of CO₂.The results indicate that the amounts of very strong basic sites and higher basicity strength onthe CaO sample are the key factors for the excellent performance of the catalysts. In contrast,the surface area, porosity and the surface structure of CaO samples have a relatively minoreffect on catalytic activity. The CaO sample obtained by decomposition of Ca（OH）2preparedby precipitating calcium nitrate with sodium hydroxide in ethylene glycol solution, whichshows the highest amount of very strong basic sites and the strength of basic sites, catalyzesthe epoxidation of styrene with higher rates. Using appropriate conditions conversion inexcess of99%with97.5%selectivity to epoxyethylbenzene could be obtained.Preparation conditions of catalyst had different effects on the epoxidation of styrene. Theresults indicate that the optimized reaction condition were calcination temperature800℃,acetonitrile as solvent, styrene/acetonitrile=1:20molar ratio, catalyst/styrene=14%qualityratio, styrene/H₂O₂=1:6molar ratio,60℃, and10h. And the recovered catalysts after hightemperature activation still showed good catalytic activity under the same conditions. Withthe increase of frequency of use, the catalyst activity gradually decreased.Other solid bases, such as La₂O₃、KNO₃/γ-Al₂O₃、K₂CO₃/γ-Al₂O₃have low catalyticcativity.