Summary of Activities/Interests
Joan Brennecke's interests are in the development of environmentally benign solvents and processes. Of particular interest is the use of ionic liquids and carbon dioxide for extractions, separations, and reactions.
Ionic liquids are organic salts that in their pure state are liquids at ambient temperatures. Although ionic liquids are organic solvents, they exhibit vanishingly small vapor pressures. Negligible volatility means that the most prevalent route for escape to the atmosphere and also exposure to workers - evaporation - is absent. Supercritical fluids are compounds that have been heated and pressurized above their critical temperatures and pressures. At conditions near the critical point, the density of the fluid can be varied from a gas-like to liquid-like with small changes in temperature or pressure to mimic a wide variety of solvents. Supercritical CO2 is nontoxic, nonflammable, abundant and inexpensive. Although it is a greenhouse gas, the use of CO2 in processes does not contribute to global warming since CO2 is not produced.
Although water stable ionic liquids are a relatively new class on compounds, it has been shown that they are suitable solvents for a wide variety of industrially important reactions. Professor Brennecke's group has been investigating the phase behavior of ionic liquids and has shown that nonvolatile organic products can be separated from them without resorting to the use of traditional volatile organic solvents, as had been done previously. They have also shown that various gases have vastly different solubilities in ILs so they can be used for performing gas separations, either in a conventional absorber/stripper configuration or by using a supported liquid membrane. The overall goal of this work is to understand how the choice of anion, cation and substituents on the cation affects thermophysical properties and phase behavior. Towards this end, Professor Brennecke's group collaborates extensively with the molecular modeling group of Professor Maginn. Current work focuses on the design and testing of new ionic liquids that possess particularly desirable physical property and phase behavior characteristics, necessary for important separation problems.
B.S. Chemical Engineering, University of Texas (1984)
M.S. University of Illinois (1987)
Ph.D. University of Illinois (1989)
Ficke, L. E., Rodriguez H. Brennecke J. F. Heat capacities and excess enthalpies of 1-ethyl-3-methylimidazolium-based ionic liquids and water. JOURNAL OF CHEMICAL AND ENGINEERING DATA, 53:2112-2119, 2008. view abstract Heat capacities and excess enthalpies were determined for three different binary water + ionic liquid systems, from (283.15 to 348-15) K, and covering the entire composition range. Specifically, the three completely water-miscible ionic liquids used were 1-ethyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, and 1-ethyl-3-methylimidazolium trifluoroacetate. The influence of temperature and composition was assessed, and suitable equations, were used to correlate the experimental data. In addition, it was found that 1-ethyl-3-methylimidazolium ethylsulfate decomposes in the presence of water to form 1-ethyl-3-methylimidazolium hydrogen sulfate and ethanol under ambient conditions.
Ficke L. E. and Brennecke J. F. Interactions of Ionic Liquids and Water. JOURNAL OF PHYSICAL CHEMISTRY B, 114:10496-10501, 2010. view abstract Experimental excess enthalpies of ionic liquid and water mixtures in combination with calculated CHELPG atomic charges were used to investigate the interactions between the species in solution. The excess enthalpies of ionic liquids in water were obtained by calorimetry, using a Setaram C80 calorimeter, including temperatures from (313.15 to 348.15) K and the entire range of composition. The ionic liquids investigated all contain the 1-ethyl-3-methylimidazolium cation except one, which has an added hydroxyl group on the cation (1-(2-hydroxyethyl)-3-methylimidazolium cation). The anions investigated are ethylsulfate, methylsulfate, hydrogensulfate, trifluoromethanesulfonate, methanesulfonate, and trifluoroacetate, and these will demonstrate the effect of systematically varying the substituents on the anion. The CHELPG atomic charges on the cations and anions were calculated using the Gaussian 03 program. The CHELPG atomic charges are consistent with the observed trends in excess enthalpy and provide insight into cation/water, anion/water, and cation/anion interactions.
Chapeaux A., Simoni L. D., Ronan T. S., Stadtherr M. A. and Brennecke J. F. Extraction of alcohols from water with 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. GREEN CHEMISTRY, 10:1301-1306, 2008. view abstract Ethanol production in the U.S. has increased 36% between 2006 and 2007 (J.M. Urbanchuk, Contribution of the Ethanol Industry to the Economy of the United States, LECG, LLC, Renewable Fuels Association, 2008) in response to a growing demand for its use as a commercial transportation fuel. 1-Butanol also shows potential as a liquid fuel but both alcohols require high energy consumption in separating them from water. 1-Butanol, in particular, is considered an excellent intermediate for making other chemical compounds from renewable resources, as well as being widely used as a solvent in the pharmaceutical industry. These alcohols can be synthesized from bio-feedstocks by fermentation, which results in low concentrations of the alcohol in water. To separate alcohol from water, conventional distillation is used, which is energetically intensive. The goal of this study is to show that, using an ionic liquid, extraction of the alcohol from water is possible. Through the development of ternary diagrams, separation coeffcients are determined. The systems studied are 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide/ethanol/ water, which exhibits Type 1 liquid-liquid equilibrium (LLE) behavior, and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide/1-butanol/water, which exhibits Type 2 LLE behavior. Based on the phase diagrams, this ionic liquid (1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide) can easily separate 1-butanol from water. It can also separate ethanol from water, but only when unreasonably high solvent/feed ratios are used. In addition, we use four excess Gibbs free energy (g(E)) models (NRTL, eNRTL, UNIQUAC and UNIFAC), with parameters estimated solely using binary data and/or pure component properties, to predict the behavior of the ternary LLE systems. None of the models adequately predicts the Type 1 system, but both UNIQUAC and eNRTL aptly predict the Type 2 system.
Muldoon M. J., Aki S. N. V. K. , Anderson J. L., Dixon J.K. , Brennecke J.F. Improving carbon dioxide solubility in ionic liquids. JOURNAL OF PHYSICAL CHEMISTRY B, 111:9001-9009, 2007.