(392n) Supercritical CO2 Extraction of 1-Butanol From Aqueous Solutions Using a Hollow Fibre Membrane Contactor

Hollow fibre membrane contactors have recently
received much attention in a number of separation or purification processes due
to their large specific areas, enhancing mass transfer and therefore extraction
efficiencies. The so called porocritical extraction process couples the
porosity of a hollow fibre membrane contactor (HFM) with the high diffusivity
of a supercritical fluid (generally carbon dioxide) to create a non-dispersive
contact between solvent and aqueous feed, allowing a high throughput capacity
without flooding or foaming issues independently of density difference between
phases. This study presents the application of this technique to the separation
of 1-butanol from aqueous solutions. 1-butanol, or ?biobutanol? is a
second generation biofuel that can be produced by anaerobic fermentation; however,
its yield is currently limited to less than 5 % by mass of the fermentation
broth and is normally recovered by distillation, which is highly energy
intensive. In this work, the
efficiency of a lab-scale HFM contactor in the supercritical CO₂
extraction of 1-butanol from a model water/1-butanol mixture and from an actual
fermentation broth is studied under a range of different flow rates,
solvent-to-feed ratios and pressure conditions. Packed column fractionation was
also carried out to enable comparison of extraction efficiency under a limited
range of conditions.