Vapor-phase deoxydehydration of 2,3-butanediol to 2-butene over MoO3/SiO2 catalyst

Abstract

Abstract The deoxydehydration (DODH) of 2,3-butanediol (2,3-BDO) to butene isomers proceeded over silica-supported molybdenum oxide (MoO3/SiO2) catalyst without any external reductants. In the DODH of 2,3-BDO over MoO3/SiO2 catalyst, cis- and trans-2-butene were produced with negligible 1-butene. The MoO3/SiO2 catalyst was inefficient for the hydrogenation of butanone and the dehydrogenation of 3-hydroxy-2-butanone, suggesting that the production of butenes did not proceed via the dehydration of 2-butanol. X-ray photoelectron spectroscopy and energy calculations by density functional theory suggest that the condensation of 2,3-BDO to form Mo(VI) diolate species initiates the DODH of 2,3-BDO. The C–C cleavage of diolate species produces acetaldehyde and Mo(IV). The coordination of 2,3-BDO to Mo(IV) leads to the parallel formation of an alkoxide and diolate species. The alkoxide produces 2-butene via 2-hydroxybutyl radical and Mo(V), while diolate generates only cis-2-butene via concerted scission of (C–O)2Mo(IV) bonds.