192
T. J. S. Schubert
8.1 General Aspects of Ionic Liquids Production Methods
8.1.1 Aspects of Purity
For many R&D-related purposes, researchers will typically—for quite understandable reasons—use the highest available quality. In physical chemistry and electrochemistry, it is often essential for many reasons to operate with the highest available
purity. Nevertheless, early investigations of published data about melting points or
viscosities of common ionic liquids led to some viscosity deviations of more than
30% depending on the source of the material. In addition, in our own labs, we
had a couple of surprises when ionic liquids for some customers were synthesized.
In one case, triethylsulfonium bis(trifluoromethylsulfonyl)imide ([S 2 2 2 ][TFSI] or
[S 2 2 2 ][NTf 2 ]) was described in the literature as a room-temperature ionic liquid,
and it also appeared as a liquid after bottling it. However, during transport to the
customer, it became a solid, and it never became liquid again at room temperature.
The reason for the higher melting point was a higher purity because impurities reduce
the melting point. As one can imagine, it led to a customer complaint, since they
expected to receive a liquid material.
In another case, a very common ionic liquid [C 1 C 6 im][Cl] was described in the
literature to be a liquid at room temperature. When it was synthesized in a 25 kg
batch size following an advanced synthesis protocol (in terms of purification of the
corresponding starting materials), it had a nearly colorless appearance. During the
work-up, after removing the solvent, it surprisingly crystallized overnight causing a
lot of trouble to remove it from the reaction vessel.
If someone needs commercial quantities of an ionic liquid, it is essential that the
customer has a clear understanding with the producer what quality is required or
what quality is sufficient for the application. This is an important question because
any additional purification step in general increases the production costs.
8.1.2 Aspects of Price
The price often determines the scope of applications. This is of importance, especially
if an ionic liquid-based technology is in competition with established technologies,
where typically a high cost pressure exists. A lower sensitivity to the cost of the IL
can be observed in fields where an ionic liquid is part of a system or process creating
a completely novel field of application (“disruptive technologies”).
In order to save valuable time in applied science and even more in corporate R&D,
it could be useful to consider the following questions before starting experiments for
implementing a proof of concept of an ionic liquid-based technology:
I. Added value: Is there really an added value?
Look at the product through the eyes of a user of your technology.
T. J. S. Schubert
8.1 General Aspects of Ionic Liquids Production Methods
8.1.1 Aspects of Purity
For many R&D-related purposes, researchers will typically—for quite understandable reasons—use the highest available quality. In physical chemistry and electrochemistry, it is often essential for many reasons to operate with the highest available
purity. Nevertheless, early investigations of published data about melting points or
viscosities of common ionic liquids led to some viscosity deviations of more than
30% depending on the source of the material. In addition, in our own labs, we
had a couple of surprises when ionic liquids for some customers were synthesized.
In one case, triethylsulfonium bis(trifluoromethylsulfonyl)imide ([S 2 2 2 ][TFSI] or
[S 2 2 2 ][NTf 2 ]) was described in the literature as a room-temperature ionic liquid,
and it also appeared as a liquid after bottling it. However, during transport to the
customer, it became a solid, and it never became liquid again at room temperature.
The reason for the higher melting point was a higher purity because impurities reduce
the melting point. As one can imagine, it led to a customer complaint, since they
expected to receive a liquid material.
In another case, a very common ionic liquid [C 1 C 6 im][Cl] was described in the
literature to be a liquid at room temperature. When it was synthesized in a 25 kg
batch size following an advanced synthesis protocol (in terms of purification of the
corresponding starting materials), it had a nearly colorless appearance. During the
work-up, after removing the solvent, it surprisingly crystallized overnight causing a
lot of trouble to remove it from the reaction vessel.
If someone needs commercial quantities of an ionic liquid, it is essential that the
customer has a clear understanding with the producer what quality is required or
what quality is sufficient for the application. This is an important question because
any additional purification step in general increases the production costs.
8.1.2 Aspects of Price
The price often determines the scope of applications. This is of importance, especially
if an ionic liquid-based technology is in competition with established technologies,
where typically a high cost pressure exists. A lower sensitivity to the cost of the IL
can be observed in fields where an ionic liquid is part of a system or process creating
a completely novel field of application (“disruptive technologies”).
In order to save valuable time in applied science and even more in corporate R&D,
it could be useful to consider the following questions before starting experiments for
implementing a proof of concept of an ionic liquid-based technology:
I. Added value: Is there really an added value?
Look at the product through the eyes of a user of your technology.