In the early 2000's Dr. Brennecke's research shifted from supercritical CO2 to Ionic Liquids. Ionic liquids (ILs) are molten salts with a melting temperature below 100°C, but are typically liquid around room temperature. They are normally composed of bulky, organic cations and inorganic or organic, polyatomic anions. ILs have many unique properties that make them attractive for a wide range of applications. ILs have immeasurable vapor pressure and are thus non-flammable and non-volatile. They are able to solvate a variety of compounds, both polar and nonpolar. In addition, ILs have a large liquidus range, typically from room temperature to their decomposition temperatures around 300-500°C. These attributes, along with the fact that IL properties can be tailored by judicious choice of anions and cations, contribute to the increasing interest in IL applications. In our group we work in collaboration with the Dr. Schneider and Dr. Maginn research groups at Notre Dame in order to design ionic liquids for use in many different applications. We also collaborate with the Stadtherr group to model the process design and Dr. Ashfeld's group from the University of Notre Dame Department of Chemistry for some of the ionic liquid synthesis
Ionic Liquids for CO2 capture
One of many energy application that we look at in our group is the use of ionic liquids for CO2 capture. By tuning the reaction of IL with CO2 we are designing a solvent for both pre- and post-combustion gas separation. Our group and collaborators introduced a new class of ILs that contain aprotic heterocylic anions and chemically react with CO2. These ILs react stoichometrically with CO2 greatly increasing the CO2 solubility. In addition we are examining ILs that are actually solid at room temperature, but phase change in the presence of CO2 to take advantage of energy from the heat of fusion.
In our lab we synthesize and characterize the ionic liquids investigating the gas solubilites (H2, N2, and CO2), reaction mechanism, IL densities, viscosities, decomposition temperatures, and melting points. We work with the Schneider group who does DFT simulations and the Maginn group who use simulations to predict the IL properties.
Co-solvent Air Conditioning Unit With Ionic Liquid Based Refridgerants
We are looking at operating a co-solvent refrigeration cycle to utilize CO2 in air conditioning units at low pressures. We have designed ionic liquids, specifically the aprotic heterocylic anion ILs, that are promising for this application. We are working to characterize the physical and chemical properties of various ionic liquids and testing them in actual large scale applications.
Electrochemical Reduction of CO2 in Ionic Liquids
The intrinsic ion conductivity, wide chemical windows and significant CO2 capture potential make ILs promising candidates for electrochemical reduction of CO2. It has been found that certain ILs are effective in lowering the overpotential, or namely, energy barrier, of electrochemical reduction of CO2, one of the primary challenges that need to be addressed before this process becomes economically viable. We are interested in applying ionic liquids as supporting electrolyte and co-catalyst for CO2 electrochemical reduction to generate certain value-added chemicals with high selectivity.
Electrochemical Properties of Ionic Liquids
Ionic liquids as green designer solvents have opened new possibilities in electrochemical industry during the past decades. The investigations of ionic liquids in electrochemical aspect in our lab focus on their application potential as alternative electrolyte in Lithium-ion battery and supercapacitor. The characterization of pure ionic liquids and lithium salts doped ionic liquid mixtures includes ionic conductivity, electrochemical window, self-diffusion coefficient and ionicity. Work on this project is done with collaboration with the Kamat group at The University of Notre Dame.
Ionic Liquids as Solvents for f Element Separations
Ionic liquids offer several advantages for an f element separation process such as wide electrochemical windows, high thermal stability, resistance to radiolysis processes, relatively low melting points and reduced criticality risks. Current research efforts are directed towards synthesis and characterization of new functionalized ionic liquids, investigation of aqueous – ionic liquid biphasic systems for solvent extraction, the dissolution of rare earths into ionic liquid systems and the effect of water as a cosolvent on the dissolution of rare earths. The lanthanide series are utilized as surrogates for actinide elements, which are studied by collaborators at Los Alamos National Lab.
Separation of Organic Compounds From an Ionic Liquid Using CO2
Phase equilibrium measurements for a determined binary or multicomponent system are useful for designing separation processes in complex mixtures. Ionic liquids have been successfully used in several solute separations with high pressure CO2, taking advantage of their low volatility along with the non-toxicity and high vapor pressure of CO2, to obtain a clean product at room conditions. In this work, organic compounds are selected and mixed with a series of ionic liquids to understand the phase behavior of adding CO2 to the liquid phase, inducing a liquid-liquid-vapor or solid-liquid-vapor equilibrium. Solubility of CO2 in the liquid phases and conditions for phase separation are obtained. These data could be useful for determine new procedures for separation of organics from ionic liquids.