Selective oxidation of alkenes that possess allylic hydrogen typically requires the use of expensive and/or environmentally unfriendly oxidants such as peroxides, hydroperoxides, nitrous oxide, oxychlorides, and oxometal complexes. A much more desirable oxidant is molecular oxygen, which, however, only achieves good yield with alkenes without allylic hydrogen or by use with H2, which is potentially explosive. Highly selective epoxidation of propene and butene can be achieved using molecular oxygen in a dilute solution of water in methanol, catalyzed by a suspension of supported Au catalyst and titanium silicalite (TS-1), and using CO as the sacrificial reductant. Results of isotope labeling experiments further infer that the dominant reaction pathway proceeds via the formation of methyl hydroperoxide. The results can be explained with Au-support interface being the active site, where molecular oxygen is adsorbed as a peroxy, which reacts to form an alkyl peroxide that migrates to TS-1 to effect epoxidation.
ASJC Scopus subject areas
- Chemical Engineering(all)