The application of life cycle assessment to the synthesis of ionic liquids

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THE APPLICATION OF LIFE CYCLE ASSESSMENT TO THE
SYNTHESIS OF IONIC LIQUIDS
SERENA Righi and LUIGI Galasso
Interdepartmental Centre for Research in Environmental Science, University of Bologna, via
dell’Agricoltura 5, 48100 Ravenna, Italy
[email protected]; [email protected]
Abstract
Ionic liquids (ILs) are ionic, salt-like materials that are liquid below 100 °C. They are a group
of new chemicals offering advantages in many industrial applications. Their use can be
classified as process chemicals (e.g., solvents, separation media) and performance chemicals
(e.g., electrolytes, lubricants). Used as a novel type of reaction medium, they provide the
chemical industry even today with more efficient processes giving higher yields.
One of the primary driving forces behind research into ionic liquids is the perceived benefit of
substituting traditional industrial solvents, most of which are volatile organic compounds
(VOCs), with non-volatile ionic liquids. For this reason, they are often labelled with “green
chemistry”. Unfortunately, until now only few environmental data are available for this group
of chemicals. More information is needed to assess ionic liquids with regard to sustainability.
Life Cycle Assessment (LCA), as an environmental sustainability tool, has received a high
level of interest. The main purpose of an LCA is to provide a quantitative assessment of the
environmental impact of products over their entire life cycle, with a view to making
improvements. Application to processes, which are key parts of the life cycle, is important in
the context of process design and development, and in the analysis of processing chains. In
this preliminary study, LCA is used to evaluate the environmental impacts “from cradle to
gate” of some chemicals belonging to the class of ILs.
Among the several ILs present in literature, the production of [Bmim][BF4] has been selected
as a case study; as a matter of fact wide literature exists as to this IL, which also includes ecocompatibility studies. The LCA methodology has been used to assess the environmental
impact caused by the [Bmim][BF4] production, as well as the relevant contributions of
precursor chemicals. Two are the goals to be achieved: the first is the optimization of the
[Bmim][BF4] production process that could be obtained by searching alternative solutions
having a reduced environmental impact as against current production steps. The second goal
aims at providing the starting point for synthesizing an ionic liquid being more ecocompatible than the [Bmim][BF4] but having analogous solvation, recycling and disposal
performances. This ionic liquid might be obtained by replacing some precursors with others
whose production turns out to have a lighter environmental impact.
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