Application of CO_2-expandedsolvents in heterogeneous catalysis:a case study

摘要

CO_2-expanded liquid (CXL) solvents are known to provide optimum reaction and environmental benefits for certain homogeneously ctalyzed oxidations.In this work,CXL solvent media are applied to heterogenesouly catalyzed oxidations.The oxidationof cyclohexene isinvestigatedas a model reaction.Conversion/selectivity measurementswere made ina stirredbatchreactor on a MCM-41 encapsulated iron corphyrin chloride complex (p=1-127bar,T=25-50deg c,t=4-12h),using either dioxygen or iodosylbenzene as oxidant.Neat acetitonitrile and CO_2-expanded acetonitrilej are used as reaction media.The pressures required for reaction studies in CO_2-based media were determined by expansion studies as well as colud point measurements.For the oxidation with dioxygen,conversion and product yields in CO_2-expanded acetonitrile (approx 30(percent)CO_2)almost doubled compared to the neat organic solvent.In contrast,CO_2-replacement of the organic solvent had a negligible effect on conversion organic soletns as reaction media and also enhance catalyst stability against leaching.These advantages suggest that CXLs are promising media for developing green heterogeneous catalytic processes.