Distillation Design In Recovering Butanol Produced From Extractive Fermentation Processes

            Butanol is an important industrial chemical with a variety of applications, such as use as a fuel additive, as a blend component to diesel fuel, as a feedstock chemical in the plastics industry, and as a foodgrade extractant in the food and flavor industry.  Each year 10 to 12 billion pounds of butanol are produced by petrochemical means.  As the projected demand for butanol increases, interest in producing butanol from renewable resources such as corn, sugar cane, or cellulosic feeds by fermentation is expanding.

            In a fermentative process to produce butanol, in situ product removal advantageously reduces butanol inhibition of the microorganism and improves fermentation rates and butanol concentrations.  Technologies for in situ product removal include stripping, adsorption, pervaporation, membrane solvent extraction, and liquid-liquid extraction.  In liquid-liquid extraction, an extractant is contacted with the fermentation broth to partition the butanol between the fermentation broth and the extractant phase.  The butanol and the extractant are recovered by a separation process, for example by distillation.  In the recovery process, the butanol can also be separated from any water, noncondensable gas, and/or fermentation by-products which may have been removed from the fermentation broth through use of the extractant.

            This presentation will focus on design tools and methodologies for distillation processes recovering butanol from a butanol-containing organic phase obtained from an extractive fermentation process. The extractive fermentation product mixture contains butanol, water, extractant, and other byproducts and impurities created from the fermentation process. Design considerations for sustainability is addressed.