3.3 Pilot-scale cyclohexene esterification–hydrogenation
Taking into account of the reaction characteristics of cyclohexene
esterification, we transferred this reaction onto a reactive
distillation reactor, which is capable of breaking through the
thermodynamic limitation imposed on the conversion while retaining the
high reaction rate for the exothermic reaction.36 On
conventional slurry-phase reactor or fixed-bed reactor, the intrinsic
conflict between the conversion and reaction rate in cyclohexene
esterification cannot be disentangled. On the basis of the above
experimental thermodynamic and kinetic data and Aspen Plus simulations,
a reactive distillation reactor was built for cyclohexene
esterification, on which the operation parameters were further
experimentally optimized, which are out of the scope of the present
work. The optimized operation parameters for the reactive distillation
reactor are presented in Table S5. And the corresponding temperature and
composition profiles in the reactive distillation reactor are
illustrated in Figure S3. Then, we established a pilot-scale
demonstration unit with a capacity of 8000 t/a using the reactive
distillation reactor for cyclohexene esterification in conjugation with
a fixed-bed reactor for ester hydrogenation at Baling Petrochemical
Company, SINOPEC (Figure S4). On the reactive distillation reactor, the
cyclohexene conversion is further improved to >99.2% with
high selectivity to cyclohexyl acetate of ~99.0%
(Figure 6A). Moreover, the reaction proceeds smoothly for more than 1000
h on stream with no indication of deactivation.
The cyclohexyl acetate produced from the reactive distillation reactor
was directly fed into the successive fixed-bed reactor for
hydrogenation. Figure 6B shows that the conversion of cyclohexyl acetate
is always close to 100%, and the cyclohexanol selectivity is always
>99% during more than 1000 h on stream, giving rise to the
conversion of 99.8% and the selectivity of 99.4% on average. In
addition, the ethanol selectivity is 99.5% on average during the whole
reaction span.