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Adsorbent monoliths are gaining increasing interest in gas phase separation processes, but have rarely been studied for liquid phase separations. In this work, we investigate an activated carbon monolith for the recovery of biobutanol from model liquid mixtures as well as compare the obtained column dynamics with the adsorption of biobutanol from gas mixtures. Single solute adsorption isotherms of acetone, n-butanol and ethanol revealed the carbon’s larger affinity for n-butanol (0.11 g/g adsorbed at 2 wt%), while dynamic separations on a fixed-bed of crushed monolith granules proved its capability to effectively separate an aqueous mixture of these three fermentation products. In contrast, liquid phase breakthrough experiments of n-butanol on the monolith column were marked by almost instantaneous detection of adsorbate at the outlet (< 5 min.) and broad tailing of the concentration curve. Measures to improve inlet flow distribution or increasing temperature to enhance mass transfer were unsuccessful. In contrast, using the same inlet flow distributors, a sharp breakthrough profile could be obtained in vapor phase, while the gas contact time (17 s) was much lower than in liquid phase (1300 s). A comparison of characteristic mass transfer times of the adsorption process highlighted the important role of the external film resistance in liquid compared to vapor phase adsorption.

[EN] Isobutanol is a promising renewable platform chemical, produced via fermentation. In the conventional downstream processing, isobutanol is recovered from the fermentation broth via evaporation or gas-stripping, followed by purification via distillation. Alternatively, an adsorptive separation can be used to recover isobutanol from the generated vapor mixture, however this has remained unexplored in the literature. In this work, we investigate the use of a hydrophobic all-silica beta zeolite (Si-BEA) to recover isobutanol from model vapor mixtures via adsorption. The Si-BEA zeolite shows a high selectivity for isobutanol over water (? = 35) and ethanol (? = 10) and excellent mass transfer properties under dynamic conditions. Sharp isobutanol breakthrough profiles were obtained, leading to a fraction of unused bed of only 6% at a gas residence time of only 0.6 s. The adsorbed isobutanol could be fully desorbed via thermal regeneration and an isothermal purge allows to remove co-adsorbed ethanol and water. The results of this work thus show the promising properties of Si-BEA for the recovery of renewable isobutanol from vapor mixtures., Julien Cousin-Saint-Remi is grateful to the FWO for financial support (grant number 12P2217N and 1512118N).