γ-Alumina-supported
catalysts with varying copper loadings
(5–25 wt %) were prepared by incipient wet impregnation and
characterized by various characterization techniques. These catalysts
were tested for the selective hydrogenation of octanal in a mixture
containing 10 wt % octanal and 2 wt % octene diluted in octanol. The
reactions were carried out in a continuous flow fixed-bed reactor
in a down flow mode with varying pressures, liquid hourly space velocities,
and hydrogen (H
2
)-to-aldehyde molar ratios. The catalyst
activities were assessed over a temperature range between 100 and
180 °C using hydrogen gas as the hydrogen source. The results
obtained showed that under these experimental conditions, copper preferentially
hydrogenates the aldehyde and the copper content exhibited no significant
influence on the catalyst activity or product selectivity. Kinetic
modeling revealed that both octanal and octene hydrogenation were
first-order reactions, although octene conversion was very low until
octanal conversion had reached a significant level. The activation
energy for octanal hydrogenation is higher than the octene hydrogenation.
A maximum octanal conversion of >99% was obtained at 160 °C,
and the best selectivity toward octanol of 99% was achieved at 100
°C (53% conversion). The pressure played a small role with regards
to octanal conversion and selectivity toward octanol, whereas it exhibited
a significant influence on the octene conversion. Increasing the hydrogen-to-aldehyde
ratio was found to have a direct influence on both octanal and octene
conversion.