Standard Article

Ionic Liquids

  1. G. Wytze Meindersma1,
  2. Matthias Maase2,
  3. André B. De Haan1

Published Online: 15 JUL 2007

DOI: 10.1002/14356007.l14_l01

Ullmann's Encyclopedia of Industrial Chemistry

Ullmann's Encyclopedia of Industrial Chemistry

How to Cite

Meindersma, G. W., Maase, M. and De Haan, A. B. 2007. Ionic Liquids. Ullmann's Encyclopedia of Industrial Chemistry. .

Author Information

  1. 1

    Process Systems Engineering Group/Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Eindhoven, The Netherlands

  2. 2

    BASF Aktiengesellschaft/Global New Business Development/Chemical Intermediates for Industrial Applications, Ludwigshafen, Germany

Publication History

  1. Published Online: 15 JUL 2007

Abstract

The article contains sections titled:

1.Introduction
2Physical and Chemical Properties
2.1.Introduction
2.2.Melting Point
2.3.Density
2.4.Viscosity
2.5.Thermal Stability
2.6.Electrochemical Window
3Synthesis/Production
3.1.Introduction
3.2.Synthesis
3.2.1.Lewis Acid-Based ILs
3.2.2.Anion Metathesis
3.2.3.Synthesis of Chloride Free ILs
3.2.4.Preparation with Microwaves
3.3.Producers of Ionic Liquids
4Applications
4.1Potential Applications
4.1.1.Solvents for Synthesis and Catalysis
4.1.1.2Solvents for Catalysis
4.1.1.3Polymer Synthesis
4.1.1.4Biocatalysis
4.1.2.Electrochemical Applications
4.1.3.Analytical Applications
4.1.4.Separations
4.1.4.1Liquid Separations
4.1.4.2Gas Separations
4.1.5.Fluid Applications: Thermal Fluids and Lubricants
4.2.Applications in Pilot Plants and Industry
4.2.1.Reactions
4.2.1.1.Acid Scavenging
4.2.1.2.Production of 2,5-dihydrofuran
4.2.1.3.Chlorination of Alcohols/Cleavage of Ethers
4.2.1.4.Hydrosilylation
4.2.1.5.Fluorination
4.2.1.6.Dimerization and Oligomerization of Olefins
4.2.2.Separations
4.2.2.1Extractive Distillation
4.2.2.2.Extraction of Aromatic Hydrocarbons
4.2.3.Electroplating/Polishing
4.2.4.ILs as Performance Chemicals
4.2.4.1Compatibilizers for Pigment Pastes
4.2.4.2.Antistatic Additives for Cleaning Fluids
4.2.5.ILs in Gas Processing
4.2.5.1.Storage of Gases
4.2.5.2.Ionic Compressor
5Analysis
6Toxicology and Occupational Health
6.1.(Eco)toxicology
6.2.Mutagenicity
6.3.Safety and Corrosion
7References

The common definition of an ionic liquid (IL), or a room temperature ionic liquid (RTIL), is that it is a liquid composed entirely of ions, which is fluid below 100 °C. Ionic liquids are generally much denser (ρ = 1 − 1.6 g/cm3) and more viscous (η = 10 − 500 mPa · s) than conventional solvents. Ionic liquids can be stable up to temperatures of 500 °C. They can easily be synthesized and the variability of the cation and anion may be used to adjust the properties of the ionic liquids. Therefore, the possibility arises to optimize an ionic liquid for a specific application by stepwise tuning the relevant solvent properties. For this reason ionic liquids have been referred to as “designer solvents”.

The potential to use ionic liquids as novel solvents or fluids for a diverse range of applications has become increasingly apparent. The intrinsic nonvolatile nature of ILs provides an opportunity to reduce, or even completely eliminate, hazardous and toxic emissions to the atmosphere, thus providing the promise for significant environmental benefits. In synthesis and catalysis, ILs have been used as solvents (or solvents and catalysts), with the greatest current effort on using the ILs as alternatives to volatile organic compounds (VOCs). Electrochemical studies have utilized the fact that ILs are liquids rather than solids to provide liquid electrolytes without needing to add an additional solvent. Ionic liquids are also used in separations, replacing volatile solvents. The number of applications on pilot-plant and commercial scale is still limited, but growing.

Although ionic liquids are also known as “green solvents”, this is not always true. They can be corrosive, flammable, or toxic. Due to their nonvolatile nature, ionic liquids are generally considered as having a low impact on the environment and human health, and thus recognized as solvents for green chemistry. However, the impact of ionic liquids on aquatic ecosystems is important given their mild to high solubility in water. Before ionic liquids will be widely used in industry, the effects of ILs on the aquatic environment must be known.