Cyclohexene esterification--hydrogenation for green and efficient
production of cyclohexanol
Abstract
A novel process based on cyclohexene esterification–hydrogenation for
the production of cyclohexanol, the key intermediate for the production
of ε-caprolactam, was devised and validated for the first time. In this
process, cyclohexene obtained from the partial hydrogenation of benzene
is esterified with acetic acid to cyclohexyl acetate, followed by
hydrogenation to cyclohexanol. The experimentally determined equilibrium
conversion of cyclohexene for cyclohexene esterification at the
stoichiometric ratio is always 68% in the temperature range of
333–373 K over the commercial Amberlyst 15 catalyst, which is
substantially higher than that of cyclohexene hydration. The apparent
activation energy (Ea) for the esterification of cyclohexene with acetic
acid is 60.0 kJ mol–1, also lower than that of cyclohexene hydration.
On the other hand, the hydrogenation of cyclohexyl acetate to
cyclohexanol is not thermodynamically limited, and high conversion of
99.5% and high selectivity of 99.7% are obtained on the La-promoted
Cu/ZnO/SiO2 catalyst.