Ionic liquids offer new possibilities for solvent engineering for biocatalytic reactions. They may just simply replace organic solvents. Ionic liquids (ILs) have been widely applied for CO2 separation owing to their distinctive properties, such as nonvolatility, tunability of structures, and good affinity with CO2. IL-based membranes exhibit hybrid properties of both ILs and membranes, which is a prospective method to achieve efficient CO2 separation from other light gases. ILs are fast emerging as a new technology with huge potential in multidimensional applications. The graph below shows the number of publications about ionic liquids published in journals. Though the data are a bit old nonetheless show interest in ILs. This reflects on the growing academic and industrial interest in Ionic Liquid technology. Today about 1000 Ionic Liquids are described in the literature, and approximately300 are commercially available. Currently, the amine is used for CO2 separation. Because it is highly corrosive it adds a huge burden on the capital costs of equipment. Current results indicated the technical viability of ILs-based CO2 capture processes compared to available technologies, but further analysis (i.e cost estimations, environmental impacts, and life cycle assessment) are required to ensure the sustainability of a new process.

1. Ionic liquids [ILs] – New emerging technology
Ionic liquids offer new possibilities for solvent engineering for biocatalytic reactions. They may just simply replace
organic solvents. Ionic liquids (ILs) have been widely applied for CO2 separation owing to their distinctive
properties, such as nonvolatility, tunability of structures, and good affinity with CO2. IL-based membranes exhibit
hybrid properties of both ILs and membranes, which is a prospective method to achieve efficient CO2 separation
from other light gases. ILs are fast emerging as a new technology with huge potential in multidimensional
applications. The graph below shows the number of publications about ionic liquids published in journals. Though
the data are a bit old nonetheless show interest in ILs. This reflects on the growing academic and industrial interest
in Ionic Liquid technology. Today about 1000 Ionic Liquids are described in the literature, and approximately300 are
commercially available.
Currently, the amine is used for CO2 separation. Because it is highly corrosive it adds a huge burden on the capital
costs of equipment.
Current results indicated the technical viability of ILs-based CO2 capture processes compared to available
technologies, but further analysis (i.e cost estimations, environmental impacts, and life cycle assessment) are
required to ensure the sustainability of a new process.
CO2 capture and sequestration are huge challenges today for the growth H2 business
The total estimated value of the market for hydrogen raw materials is $ 115 billion, and it is expected that it will
only grow, reaching $ 155 billion by 2022. Demand for hydrogen has grown more than threefold since 1975. But it
almost entirely supplied from fossil fuels, with 6% of global natural gas and 2% of global coal generating around 830
million tons of carbon dioxide per year. Only a small fraction of global hydrogen is produced today from non-carbon
emitting water electrolysis. Until non-carbon emitting new technologies are developed and scaled up sequestration
of CO2 play a very important role if the H2 market has to grow
What is Ionic liquid?
In contrast to ordinary liquids like water or petrol which are made of electrically neutral molecules with no
electricity in the molecules, an ionic liquid is made of ions. These substances are variously called liquid electrolytes.
They have melting points lower than 100 °C. ILs have many advantages over traditional organic solvents including
negligible vapor pressure at room temperature because of strong ionic bonds as well as high thermal stability,
making them nearly ideal solvents in extraction techniques. The physical and chemical properties including thermal

2. stability, viscosity, and solubility in water and other organic solvents can be varied by simply changing the
combination of cations and anions.
Technical
What is liquid?
A liquid is a nearly incompressible fluid that retains a (nearly) constant volume independent of pressure. As such, it
is one of the four fundamental states of matter (the others being solid, gas, and plasma), and is the only state with a
definite volume but no fixed shape. A liquid is made up of tiny vibrating particles of matter, such as atoms, held
together by intermolecular bonds. Most liquids resist compression, although others can be compressed. Unlike a
gas, a liquid does not disperse to fill every space of a container and maintains a fairly constant density. A distinctive
property of the liquid state is surface tension, leading to wetting phenomena. Water is, by far, the most common
liquid on Earth.
What is the difference between a molecule and an ion?
Application of ionic liquids
CO2 separation and sequestration
by ionic liquids
Process
A typical CO2 absorption process consists of a feed gas, an absorption column, a stripper column, and output
streams of CO2-rich gas to be sequestered, and CO2-poor gas to be released to the atmosphere.
Properties of molecules vs ions:
A molecule is when a bunch of non-charged atoms bond together to form the smallest and
most basic unit of an element or a compound. If they are the same type of atoms, they form an
element and if they are different types of atoms, they form a compound. Molecules usually
hold the chemical properties of the elements or compounds they make up. An ion is basically an
atom or molecule that has lost or gained one or more electrons, causing it to have an unequal
number of protons in the nucleus and electrons in the orbitals so that it now has a positive (if it
loses electrons) or negative (if it gains electrons) charge.
A typical amine gas treating process flow diagram.
Ionic liquids for use in CO2 capture by absorption could follow a
similar process.
How does it work?
Principle: Amines are the most prevalent absorbent in post combustion
carbon capture technology today. In particular, mono-ethanolamine
(MEA) has been used in industrial scales in post combustion carbon
capture, as well as in other CO2 separations, such as "sweetening" of
natural gas. However, amines are corrosive, degrade over time, and
require large industrial facilities. Ionic liquids on the other hand, have
low vapor pressures due to the strong ionic (Coulomb-) attractive forces
within these substances. Vapor pressure remains low through the
substance's thermal decomposition point (typically >300 °C). In
principle, this low vapor pressure simplifies their use and makes them
"green" alternatives. Additionally, it reduces risk of contamination of
the CO2 gas stream and of leakage into the environment. The solubility
of CO2 in ionic liquids is governed primarily by the anion, less so by the
cation. The hexafluorophosphate (PF6–) and tetrafluoroborate (BF4–)
anions have been shown to be especially amenable to CO2 capture.

3. It is obvious that some of the unique properties of ions have made ionic liquids so special.
Molecule’s properties
In simple words, a molecule is an electrically neutral group of two or more atoms held together by chemical
bonds. Molecules are distinguished from ions by their lack of electrical charge. Molecules are held together by
either covalent bonding or ionic bonding.
Covalent bonding
A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs
are termed shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms,
when they share electrons, is termed covalent bonding
Ionic bonding
Ionic bonding is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions
and is the primary interaction occurring in ionic compounds. The ions are atoms that have lost one or more
electrons (termed cations) and atoms that have gained one or more electrons (termed anions) This transfer of
electrons is termed electrovalence in contrast to covalence.
The ionic bond is usually stronger than the Van der Waals forces between the molecules of ordinary liquids.
Ion’s properties
An ion is a particle, atom, or molecule with a net electrical charge.
Properties of ions: That makes ions unique
Ions in their gas-like state are highly reactive and will rapidly interact with ions of opposite charge to give neutral
molecules or ionic salts. Ions are also produced in the liquid or solid state when salts interact with solvents (for
example, water) to produce solvated ions, which are more stable, for reasons involving a combination of energy and
entropy changes as the ions move away from each other to interact with the liquid. Electrons, due to their smaller
mass and thus larger space-filling properties as matter waves, determine the size of atoms and molecules that
possess any electrons at all. Thus, anions (negatively charged ions) are larger than the parent molecule or atom, as
the excess electron(s) repel each other and add to the physical size of the ion because its size is determined by its
electron cloud. Cations are smaller than the corresponding parent atom or molecule due to the smaller size of the
electron cloud. One particular cation (that of hydrogen) contains no electrons and thus consists of a single proton -
much smaller than the parent hydrogen atom.
Ionic liquid emerging technologies
Unique properties of ionic liquids
[1] are liquid at unusually low temperatures.
[2] the melting point below room temperature, some of them even have melting points below 0 °C
[3] liquid over a wide range of temperature range (300–400 °C)
[4] negligible vapor pressure due to the strong ionic (Coulomb-) interaction within these substances
[5] non-flammable
[6] high thermally, mechanically as well as an electrochemically stable product
[7] flexible, properties can be tailored according to needs. The choice of the cation has a strong impact on the
properties of the Ionic Liquid and will often define the stability.
What makes ionic liquids unique solvent? One property that is ionic bonds
Everything of ionic liquids hinges on their ionic bonds

4. Ionic bonds form stronger than van der Waals attractive forces gives it low vapor pressure, melting points below
room temperature; some of them even have melting points below 0 degc and stay as a liquid over a wide
temperature range (300–400 degc). Most importantly flexibility to insert anions and cations to tailor the
During the CO2 capture process, the anion and cation play a crucial role in the dissolution of CO2. Furthermore,
intermolecular forces, such as hydrogen bonds, van der Waals bonds, and electrostatic attraction, contributes to
the solubility of CO2 in ionic liquids. This makes ionic liquids promising candidates for CO2 capture because the
solubility of CO2 can be modeled accurately by the regular solubility theory (RST), which reduces operational costs
in developing more sophisticated model to monitor the capture process.