Chapter 6
Green Synthesis of Ionic Liquids for Green Chemistry
Downloaded by CORNELL UNIV on July 18, 2012 | http://pubs.acs.org Publication Date: August 26, 2003 | doi: 10.1021/bk-2003-0856.ch006
Rex X. Ren Max Tishler Laboratory of Organic Chemistry, Department of Chemistry, Wesleyan University, Middletown, CT 06459
A n environmentally friendly ("green") method for synthesis of ionic liquids has been developed. A number of useful ionic liquids have been prepared in large scale in a solvent-free and waste-free manner and in one reaction vessel, where halide-based ionic liquids were converted to non-halide-based ionic liquids in the presence o f Brønsted acids and primary alcohols (ethanol, 1-propanol, 1-butanol). The alkyl halides can be recovered and reused. This novel, innovative technology eliminates the shortcomings in the previously widely used methods of making ionic liquids via the anion metathesis approaches which employ conventional organic solvents, generate aqueous and solid wastes and have a technical difficulty in industrial scale-up. The utilization of such a novel synthetic method for ionic liquids should facilitate further development of green chemistry and green chemical technologies.
70
© 2003 American Chemical Society In Ionic Liquids as Green Solvents; Rogers, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2003.
71
Downloaded by CORNELL UNIV on July 18, 2012 | http://pubs.acs.org Publication Date: August 26, 2003 | doi: 10.1021/bk-2003-0856.ch006
Introduction Green chemistry represents a trend in chemically related research, aiming at waste minimization and cost effectiveness (/). Recently, there has been a gradual but steadfast rise of general interest in environmental science, technology and practice, which aims at improving health, aesthetics and in many cases, the economics of individual chemical operations (2). In the chemical world, this can be achieved via designing new reactions or modifying existing chemical processes. Conventional organic solvents are used in a range of industrial applications (J). However, volatile organic compounds readily evaporate, which often have complex negative effects on the environment. They have been implicated as one of the sources of ozone depletion, global climate change and smog formation. The avoidance of hazardous, volatile organic solvents is essential in future industrialization of green chemistry technologies. On the other hand, reactivity and selectivity as well as product separation are important issues for efficient chemical synthesis and process chemistry (4). Waste minimization and pollution prevention represent significant challenges that will require alternative chemistries and processes. In response to theses challenges, several strategies have been developed: (a) chemistry and chemical reaction-based as well as non-reaction-based engineering for pollution avoidance and prevention, (b) green design, manufacturing and industrial ecology for sustainability. Recently, solvent-free reactions (5), supercritical CO2 (
