We need to separate a mixture in a column distillation using an extractive distillation system.
see the article of William L. Luyben* Control of the Heterogeneous Azeotropic n-Butanol/Water Distillation System, Energy & Fuels 2008, 22, 4249–4258 at
http://pubs.acs.org/doi/pdf/10.1021/ef8004064
You may try a fairly polar solvent, such as ethyl acetate or something alike.
Actually, the optimum solvents must have low water sulubilities yet a reasonable affinity for ethanol and butanol. I have successfully used several different non-polar solvents in earlier projects.
Hi Joel
Do you want to break the azeotrope? F.E. a separation of water and alcohol inside a destilliation column or do you want to extract something polar from an aqueos Phase..or maybe both?
To break azeotropes you can try to destill under overpressure, this is a suitable method for some difficult mixtures, even if the boiling points are very close, you might have to optimize or enlarge your theoretical destillation bottoms and look om the capacity of your colon.
The choice of solvents is a balance between selectivity and capacity. Isopariffinic type solvents can have very high selectivity and can be used to break water azeotropes but may have lower capacities that other more polar solvents. More polar solvents may have greater capacities and higher extraction efficiencies, but may have more water carryover in the extracted alcohol and more solvent in the aqueous stream which would need to be stripped out and recovered. I have even seen some blends proposed to increase the concentraton of alcolhol in the solvent stream. Years ago, I designed and operated a continous system that fermented ethanol, extracted it, stripped off the dry ethanol, and recycled the solvent. You can probably find good references to this work in early work sponsored the the U.S. Department of Energy.
It depends on the composition of your mixture. You can use for example a complex of distillation columns with a splitting vessel (limited mutual solubility of water and butanol). If you consider extractive distillation the only way for separation try as an extractive agent DMSO or DMFA. Perhaps water can be used as autoextractive agent. But you need to check it.
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