Status: Postdoctoral Researcher
Ph.D. Institution: Seoul National University
Motivated by rising oil prices, there is great interest in the production of ethanol, by fermentation of corn or agricultural residues, so it can be used as an alternative fuel stock. However, use of ethanol as a biofuel has some drawbacks including limited blend compatibility with gasoline (max ~ 10 %) and issues integrating with the existing gasoline supply infrastructure. Butanol, however, has some advantages over ethanol which may allow it to overcome these barriers. Butanol's energy content is 30% higher than ethanol's and it is more chemically similar to gasoline, giving it better blend compatibility. Because of this, butanol (either in a pure form or as a butanol-gasoline blend) can be used in conventional gasoline engines. In addition, butanol, because of its low vapor pressure, low water absorption, and low corrosivity, can be transported using the current piping networks used for gasoline transportation.
As butanol is highly toxic to fermentating organisms, engineering techniques are needed to simultaneously produce the butanol and quickly remove it from the fermentation broth; to prevent poisoning, the butanol concentration should be maintained below ~ 1 %. Traditionally, distillation has been used to recover the butanol from the fermentation broth, however, the energy required for this separation is larger than that produced by combustion of butanol in the first place. Therefore an alternative separation approach is needed. One of the most promising techniques is pervaporation, which allows for selective and energy-efficient removal of butanol from the fermentation broth via a membrane. Using this approach, the butanol vapor will selectively diffuse through the membrane after which it is condensed and collected for further use.
It is desirable for pervaporation membranes to exhibit both sufficient mechanical integrity and high flux and selectivity for the desired chemical. Typical random copolymer membranes can impart a large fraction of liquid-transporting moieties to the polymer chains allowing for higher flux, however, this generally results in deterioration of the mechanical integrity of the membranes. Therefore, in order to prepare pervaporation membranes with both high butanol flux and mechanical integrity, my work focuses on using block copolymer membranes in which one domain provides the separation and transport properties (allowing the butanol to pass through), while the other domain maintains the mechanical integrity of the membranes. To achieve this I will synthesize and characterize the desired block copolymers, deposit these as films to produce membranes (this will require ensuring that the domains possess out-of-plane orientation), and actually testing these membranes for butanol pervaporation.