Main > IONIC LIQUIDS. > Uses. > BioOrganic Chemistry > Org.: USA. U (ABE Fermentation) > BioMass Microbial Fermentation To > Aq. Soln.: Acetone, BuOH & EtOH> > Butanol Sepn. from Aq. Soln. By: > Ionic Liquid+PerVaporation > NPLS Contents
IONIC LIQUIDS IN A RENEWABLE FERMENT
Designer solvents show potential for recovery of fuel, chemical feedstock from biomass.
Room-temperature ionic liquids could enhance the recovery of butanol, an important chemical feedstock and potential biofuel, from fermentation broth. AUTHORS use the ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate--[8-mim][PF6]--to extract butanol from an aqueous solution of the alcohol. They then use a technique known as pervaporation to remove the butanol from the ionic liquid. Butanol is one of the products of a bioprocess known as ABE fermentation-- the microbial fermentation of carbohydrates to acetone, butanol, and ethanol. ABE fermentation is a potentially attractive process for converting biomass, a renewable resource, into fuels and chemical feedstock. For example, agricultural wastes--such as mycotoxin-contaminated corn that is unsuitable for use as animal feed--and agricultural by-products can be used as inexpensive substrates for the process.
BUTANOL IS USED industrially in the production of resins, coatings, plasticizers, and a variety of other products. It is used as a solvent in the food and flavors industry. "Biobutanol is also a potential biofuel." "However, the economics of the fermentation are not that great, and advances in the fermentation and separation stages are required before the process becomes economically feasible."
Distillation to recover butanol from fermentation broth is not economical. The most promising technology for recovering butanol has been pervaporation, a combination of two processes: permeation and evaporation. Their work now shows that ionic liquids may have a role to play. "We have found that the overall selectivity of the extractive-pervaporative separation exceeds the selectivity of conventional pervaporation. AUTHORS employ a commercial polydimethylsiloxane membrane for the permeation process.
"A liquid feed is applied to one side of a nonporous membrane and a vacuum to the other side."
"The pressure-concentration gradient across the membrane provides a driving force for the separation. The components of the feed dissolve into the polymer, diffuse through the membrane, and evaporate on the other side." The difference in the permeation rate enriches the permeate with some of the feed components.
"The nonvolatility of ionic liquids makes them ideal media for pervaporation since they do not permeate through the pervaporation membrane." "For example, comparing butanol-water and butanol-ionic liquid feeds under the same conditions, the pervaporation selectivity of the butanol-ionic liquid feed is enormous, given that the permeate is pure butanol.
"A part of the fermentor could be filled with an ionic liquid which is continuously recycled through the pervaporation module," he continues. "That way, you would have continuous fermentation coupled with pervaporation, enabling continuous fermentation product recovery."
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