Ionic Liquids

Abstract

The article contains sections titled: 1. Introduction 2 Physical and Chemical Properties 2.1. Introduction 2.2. Melting Point 2.3. Density 2.4. Viscosity 2.5. Thermal Stability 2.6. Electrochemical Window 3 Synthesis/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 4 Applications 4.1 Potential Applications 4.1.1. Solvents for Synthesis and Catalysis 4.1.1.2 Solvents for Catalysis 4.1.1.3 Polymer Synthesis 4.1.1.4 Biocatalysis 4.1.2. Electrochemical Applications 4.1.3. Analytical Applications 4.1.4. Separations 4.1.4.1 Liquid Separations 4.1.4.2 Gas 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 4.2.2.1 Extractive Distillation 4.2.2.2. Extraction of Aromatic Hydrocarbons 4.2.3. Electroplating/Polishing 4.2.4. ILs as Performance Chemicals 4.2.4.1 Compatibilizers 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 5 Analysis 6 Toxicology and Occupational Health 6.1. (Eco)toxicology 6.2. Mutagenicity 6.3. Safety and Corrosion 7 References 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/cm 3 ) 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.

Effect of methylimidazole on cellulose/ionic liquid solutions and regenerated material therefrom

“…The possibility to pair anions with cations yields an almost endless library of ILs, and they are used in numerous fields, such as separation technology, electrochemistry, catalysis, and as solvents [3,4]. In the last decade, ILs as solvents for biomass in general and cellulose in particular have been widely investigated [5][6][7] since 2002 when Swatloski published the pioneering work on dissolution of cellulose in 1-butyl-3-methylimidazolium chloride (BMIMCl) [8].…”

Thermal and Viscoelastic Properties of Cellulosic Gels with Different Ionic Liquids and Coagulation Agents

“…Depending on the structure of the imidazolium cation and the anion, solutions with a cellulose content as high as 25% have been reported (Swatloski et al 2002). The IL's have a low vapor pressure and high thermal stability; thus they are considered to give negligible exposure to workers and environment and may therefore be a replacement for volatile organic compounds (VOC) in industrial chemistry (Meindersma et al 2007). Unlike other salts, ionic liquids are liquid (and can thus be used as solvents) at relatively low temperatures (Meindersma et al 2007).…”

“…The IL's have a low vapor pressure and high thermal stability; thus they are considered to give negligible exposure to workers and environment and may therefore be a replacement for volatile organic compounds (VOC) in industrial chemistry (Meindersma et al 2007). Unlike other salts, ionic liquids are liquid (and can thus be used as solvents) at relatively low temperatures (Meindersma et al 2007). As an example, the melting temperature of 1-butyl-3-methylimidazolium chloride is ca.…”

Design of high surface area poly(ionic liquid)s to convert carbon dioxide into ethylene carbonate

“…Successively, anion exchange was used to further modify the anionic moieties, that is one of the pivot factor for the IL chemical behavior and stability. 38 In particular, NaBF 4 was used to obtain poly(DVB-co-mVIm + BF 4 -) (1d, 2d). The completeness of the anion exchanges on the PILs were proven by means of EDX microanalysis.…”