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Extramural Research

Final Report: Investigation of Room Temperature Ionic Liquids as Environmentally Benign Solvents for Industrial Separations (TSE99-A)

EPA Grant Number: R828257
Title: Investigation of Room Temperature Ionic Liquids as Environmentally Benign Solvents for Industrial Separations (TSE99-A)
Investigators: Rogers, Robin D.
Institution: University of Alabama - Tuscaloosa
EPA Project Officer: Karn, Barbara
Project Period: May 1, 2000 through April 30, 2003
Project Amount: $375,000
RFA: Technology for a Sustainable Environment (1999)
Research Category: Pollution Prevention/Sustainable Development

Description:

Objective:

The overall objectives of this research project were to: (1) develop and elaborate the classification of ionic liquids (ILs) to compare and contrast different ILs, (2) benchmark performance, and (3) discover new applications and uses of ILs. In addition to the scientific information developed, this research project provided an educational aspect that will provide information to train researchers about the scope, potential, and pitfalls of ILs; most importantly, that ILs can be utilized as much more than just nonvolatile solvents.

We proposed to construct and apply a screening protocol for the assessment of IL properties that will generate the necessary data to develop an understanding of structure-property relationships for classes of ILs. Materials and experimental methodologies were benchmarked against other procedures (e.g., liquid chromatographic screening), and comparison of the results with those of traditional solvents were made.

To achieve the objectives, we: (1) developed a screening protocol to rapidly study and evaluate all current, new, and emerging commercial ILs; (2) assessed solute partitioning in IL organic two-phase systems using Linear Free Energy Relationship analysis to develop ranking and categorization of ILs by solvent characteristics and utility in specific applications; (3) benchmarked the performance of different "representative" ILs identified using the screening studies above, to provide a set of "representative" ILs for evaluation; (4) applied clean syntheses of ILs to expand the range of materials for evaluation; and (5) instructed how to teach about ILs and their place within the paradigm of green chemistry.

Summary/Accomplishments (Outputs/Outcomes):

Twenty-eight refereed full papers, communications, and proceedings chapters have been published describing the major findings of this research. The research has served as the basis for a new proposal that was accepted for funding in 2003 by the U.S. Environmental Protection Agency's Science to Achieve Results (STAR) program.

During the project period, the research focused on generating new data leading to the development of a fundamental scientific-engineering knowledge base in IL properties (with particular emphasis on their use as alternatives to volatile organic compounds [VOCs] in liquid-liquid two-phase separations), a prerequisite to the development of new pollution prevention technologies using these neoteric solvents. We have tried to address the promotion of IL-based solutions as one part of a green chemistry tool kit, while acknowledging that general availability and cost issues have not been addressed by manufacturers. Some of our current explorations of low-cost, widely available ILs, making ILs more readily available for use in environmentally benign technologies, and the development of a rubric for the evaluation of different ILs in the context of green chemistry, will lead to significant advances as the field continues to mature.

Assessing Solute Partitioning in IL Two-Phase Systems To Develop Ranking and Categorization of ILs by Solvent Characteristics and Utility in Specific Applications

Studies of IL Aqueous Two-Phase Systems. Radiotracer partitioning of solutes has been used to help understand the characteristics and behavior of ILs. We also have analyzed partitioning data to extract linear solvent-free energy relationship (LFER) information that defines the performance of ILs. We have investigated and demonstrated pH-induced partitioning, as controlled by the ionization of organic solutes such as benzoic acid. We have studied the effects of complexing agents, pH and salt concentrations in the aqueous phase on metal ion partitioning, particularly with relevance to actinide and fission product separation and solvent extraction. Partitioning of organic molecules in IL/water systems has been shown to follow traditional octanol/water distributions, which has useful implications for applying hydrophobic ILs as direct replacements for solvents such as benzene, toluene, dichloromethane, or chloroform in two-phase system separation schemes.

Complexity in IL Mixtures. We have shown that mixtures of ILs with secondary solvents, particularly two-phase systems, are not necessarily simple combinations of the two components. For example, we have shown that even nominally hydrophobic ILs (such as 1-butyl-3-methylimidazolium hexafluorophosphate, [C4mim][PF6]) can be solubilized in water by the addition of an appropriate cosolvent.

IL Aromatic Mixtures Form Liquid Clathrate Mixtures. Although it had long been recognized that individual examples of ILs could support liquid clathrate formation, studies have provided evidence that substantiates the general formation of liquid clathrates for ILs in contact with aromatics.

Determination of Heat Capacities and Evaluation of ILs as Thermal Fluid. The thermophysical properties of a key set of ILs have been investigated. Heat capacity data have been determined as a function of temperature, and have been correlated with data on changes in density with temperature to calculate volumetric heat capacities and thermal energy storage potentials of the ILs across a wide temperature range. The results are compared with those of common organic thermal fluids, and indicate that ILs could be considered as candidate thermal fluids for heat transfer applications.

QSPR (Quantitative Structure Property Relationships)/CODESSA Analyses for the Prediction of Melting Points of Imidazolium and Pyridinium Bromide Salts. Although a statistically effective model could be obtained, it proved not to be sufficiently robust for practical application. More "empirical" models, using a greater degree of "chemical intuition" and based on data collected from self-consistent (and necessarily more limited) sets of salts may prove to be more useful.

Methodologies for Preparing New and Existing ILs Using Syntheses That are Cleaner, More Atom Efficient, and Produce Less Hazardous Byproducts Than the Conventional Alkylhalide-Based Alkylation/Methathesis Procedures for IL Preparation

Alkylimidazolium Alkylsulfate ILs Have Been Prepared and Characterized. These materials have uses as new, low-cost commodity ILs with properties similar to other ILs containing water-miscible, moderately basic, and coordinating anions such as halide, nitrate, sulfonate, and carboxylates. We demonstrated that these ILs can be used as intermediates to prepare other ILs by metathesis (i.e., [PF6], and [NTf2]), which do not contain any halide contaminants from the initial IL.

New ILs Containing Pendant Hydroxyl Groups. These novel IL systems have been developed using clean, atom-efficient synthetic routes. These ILs can be easily prepared in high purity and in relatively large volumes. We have prepared, and are characterizing, the properties of these novel ILs. We also are investigating their applicability to chemical and biochemical applications. They offer the potential for the stabilization of enzyme catalysts though hydrogen bonding, and have interesting effects on aqueous miscibility. Additionally, if chiral epoxides are used as reactants, ILs containing chirality in the cation could be easily prepared. A patent application has been filed on the application and preparation of these new IL materials.

ILs Containing Fused Polycyclic N-Alkylisoquinolinium Cations. Novel ILs have been synthesized, characterized, and utilized in liquid/liquid partitioning from water. Changes in liquid/liquid solute distribution values as a function of the changed cation (compared to imidazolium containing ILs) was of particular interest.

ILs Containing Polyether Spacers Have Been Synthesized. Metal partitioning studies of mercury and cesium between the IL and water have been investigated. As anticipated, the incorporation of "task-specific" extracting functionalities into the cationic core of the IL led to enhanced partitioning of mercury to the IL phase when compared to conventional ILs, and is comparable to that of IL containing specific metal extractants. This simple, new IL demonstrates the proof of concept, that polyether-coordinating functions can be easily incorporated and used to facilitate metal extraction; although, at present, the mechanism for extraction has not been fully elucidated.

Application of the Knowledge Gained To Target the Properties Required and Defined by Synthetic Chemistry for Specific Reactions, Has Resulted in Enhanced Catalyst Stability and Increased Reactivities in Polymerization Chemistries

Transition Metal Catalyzed Polymerizations in ILs. The influence of IL solvents on CO/styrene copolymerization catalyzed by palladium catalysts has been studied. The understanding of IL solvent properties and interactions of the cation and anion components with the catalyst led to the investigation of a range of ILs as new solvents for these useful reactions. Catalyst turnover number (TON) and polymer quality produced was equal to or better than using the same standard catalysts in conventional solvents. They also indicated how new catalyst systems can be designed and optimized for use in IL solvents, allowing efficient sustained catalyst lifetimes combined with production of high-quality polymers with high TON.

Toxicological Studies. We have nominated the ILs 1-butyl-3-methyl-imidazolium chloride, N-butyl-pyridinium chloride, and 1-butyl-1-methyl-pyrrolidinium chloride for toxicological testing based on their widespread interest as possible solvent alternatives to VOCs to the National Toxicology Program of the National Institute of Environmental Health Sciences. To set the direction for future research in this area, we believe it is vital that early testing on these candidate materials be conducted. Without the guidance this testing could provide, true "green" applications of these new solvent classes could be severely delayed.

Toxicological Screening and Comparison of IL Toxicity. Most of the current research that is being conducted at universities, national laboratories, and industry on these neoteric solvents shows them as potentially "green" or environmentally benign alternative solvents. In fact, we have begun studies with Professors Guy and Kim Caldwell of the University of Alabama's Department of Biological Sciences to conduct toxicity screening of 1-butyl-3-methylimidazolium chloride using nematodes.

Enzyme-Catalyzed Reactions and Bioactive Films. The potential for performing enzyme-catalyzed reactions in ILs is gaining increased attention in the literature. Our discovery that cellulose dissolves in 1-butyl-3-methylimidazolium chloride ([bmim]Cl) led us to investigate cellulose-catalyzed hydrolysis of cellulose in [bmim]Cl. A systematic study was conducted on the irreversible solvent and ionic strength-induced inactivation and unfolding of cellulase from Trichoderma reesei (E.C. #3.2.1.4). Experiments indicate that [bmim]Cl and several other ILs inactivate cellulase under these conditions.


Journal Articles on this Report : 17 Displayed | Download in RIS Format

Other project views: All 28 publications 19 publications in selected types All 17 journal articles

Type Citation Project Document Sources
Journal Article Abraham MH, Zissimos AM, Huddleston JG, Willauer HD, Rogers RD, Acree Jr. WE. Some novel liquid partitioning systems: water-ionic liquids and aqueous biphasic systems. Industrial and Engineering Chemistry Research 2003;42(3):413-418. R828257 (Final)
not available
Journal Article Gutowski KE, Broker GA, Willauer HD, Huddleston JG, Swatloski RP, Holbrey JD, Rogers RD. Controlling the aqueous miscibility of ionic liquids: Aqueous biphasic systems of water-miscible ionic liquids and water-structuring salts for recycle, metathesis, and separations. Journal of the American Chemical Society 2003;125(22):6632-6633 R828257 (Final)
not available
Journal Article Holbrey JD, Reichert WM, Swatloski RP, Broker GA, Pitner WR, Seddon KR, Rogers RD. Efficient, halide free synthesis of new, low cost ionic liquids: alkylimidazolium salts containing methyl- and ethyl-sulfate anions. Green Chemistry 2002;4(5):407-413. R828257 (Final)
not available
Journal Article Holbrey JD, Reichert WM, Nieuwenhuyzen M, Johnson S, Seddon KR, Rogers RD. Crystal polymorphism in 1-butyl-3-methylimidazolium halides: supporting ionic liquid formation through inhibition of crystallization. Chemical Communications 2003;14:1636-1637. R828257 (Final)
not available
Journal Article Holbrey JD, Reichert WM, Nieuwenhuyzen M, Sheppard O, Hardacre C, Rogers RD. Liquid clathrate formation in ionic liquid-aromatic mixtures. Chemical Communications 2003;(4):476-477
abstract available  
R828257 (Final)
not available
Journal Article Holbrey JD, Visser AE, Spear SK, Reichert WM, Swatloski RP, Broker GA, Rogers RD. Mercury(II) partitioning from aqueous solutions with a new, hydrophobic ethylene-glycol functionalized bis(methylimidazolium) ionic liquid. Green Chemistry 2003;5(2):129-135. R828257 (Final)
not available
Journal Article Holbrey JD, Turner MB, Reichert WM, Rogers RD. New ionic liquids containing an appended hydroxyl functionality from the atom-efficient, one-pot reaction of 1-methylimidazole and acid with propylene oxide. Green Chemistry 2003;5(6):731-736 R828257 (Final)
not available
Journal Article Huddleston JG, Visser AE, Reichert WR, Willauer HD, Broker GA, Rogers RD. Characterization and comparison of hydrophilic and hydrophobic room temperature ionic liquids incorporating the imidazolium cation. Green Chemistry 2001;3(4):156-164. R828257 (Final)
not available
Journal Article Katritzky AR, Jain R, Lomaka A, Petrukhin R, Karelson M, Visser AE, Rogers RD. Correlation of the melting points of potential ionic liquids (imidazolium bromides and benzimidazolium bromides) using the CODESSA program. Journal of Chemical Information and Computer Science 2002;42(2):225-231. R828257 (Final)
not available
Journal Article Katritzky AR, Lomaka A, Petrukhin R, Jain R, Karelson M, Visser AE, Rogers RD. QSPR correlation of the melting point for pyridinium bromides, potential ionic liquids. Journal of Chemical Information and Computer Science 2002;42(1):71-74. R828257 (Final)
not available
Journal Article Klingshirn MA, Broker GA, Holbrey JD, Shaughnessy KH, Rogers RD. Polar, non-coordinating ionic liquids as solvents for the alternating copolymerization of styrene and CO catalyzed by cationic palladium catalysts. Chemical Communications 2002;(13):1394-1395
abstract available  
R828257 (Final)
not available
Journal Article Swatloski RP, Visser AE, Reichert WM, Broker GA, Farina LM, Holbrey JD, Rogers RD. Solvation of 1-butyl-3-methylimidazolium hexafluorophosphate in aqueous ethanol-a green solution for dissolving "hydrophobic" ionic liquids. Chemical Communications 2001;20:2070-2071. R828257 (Final)
not available
Journal Article Swatloski RP, Visser AE, Reichert WM, Broker GA, Farina LM, Holbrey JD, Rogers RD. On the solubilization of water with ethanol in hydrophobic hexafluorophosphate ionic liquids. Green Chemistry 2002;4(2):81-87. R828257 (Final)
not available
Journal Article Swatloski RP, Holbrey JD, Rogers RD. Ionic liquids are not always green: hydrolysis of 1-butyl-3-methylimidazolium hexafluorophosphate. Green Chemistry 2003;5(4):361-363 R828257 (Final)
not available
Journal Article Turner MB, Spear SK, Huddleston JG, Holbrey JD, Rogers RD. Ionic liquid salt-induced inactivation and unfolding of cellulase from Trichoderma reesei. Green Chemistry 2003;5(4):443-447. R828257 (Final)
not available
Journal Article Visser AE, Holbrey JD, Rogers RD. Hydrophobic ionic liquids incorporating N-alkylisoquinolinium cations and their utilization in liquid-liquid separations. Chemical Communications 2001;23:2484-2485. R828257 (Final)
not available
Journal Article Visser AE, Swatloski RP, Reichert WM, Mayton R, Sheff S, Wierzbicki A, Davis JH, Rogers RD. Task-specific ionic liquids incorporating novel cations for the coordination and extraction of Hg2+ and Cd2+: Synthesis, characterization, and extraction studies. Environmental Science & Technology 2002;36(11):2523-2529
full text available
R828257 (Final)
not available
Supplemental Keywords:

ionic liquids, benign solvents, liquid/liquid separations, linear free energy relationship, quantitative structure property relationship, QSPR, ionic liquid physical properties, ionic liquid clean synthesis, neoteric solvents, chemical transport, alternative media, chemicals, toxics, green chemistry, alternatives, sustainable development, clean technologies, environmentally conscious, volatile organic compounds, VOCs, cleaner production, environmentally benign solvents, green process systems, industrial innovations, industrial process, industrial separators, innovative technology, linear solvent free energy relationships, physicochemical data, room temperature ionic liquids, solvents, source reduction., RFA, Scientific Discipline, Sustainable Industry/Business, cleaner production/pollution prevention, Environmental Chemistry, Sustainable Environment, Technology for Sustainable Environment, New/Innovative technologies, Environmental Engineering, linear solvent free energy relationships, solvent substitutes, cleaner production, physicochemical data, environmentally benign solvents, room temperature ionic liquids, green process systems, industrial process, toxicity, innovative technology, ionic liquids, industrial innovations, industrial separators, pollution prevention, source reduction, Volatile Organic Compounds (VOCs), green chemistry

Relevant Websites:

http://www.bama.ua.edu/~rdrogers Exit
http://www.bama.ua.edu/~cgm Exit

Progress and Final Reports:
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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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