The Effect of Water Content on the Viscosity of
Tetrafluoroborate Containing Ionic Liquids
Bradley Buchheit, Ruth Baltus, PhD.
Department of Chemical and Biomolecular Engineering
Ionic liquids are salts that are in liquid form at room temperature. One of the interesting
properties of ionic liquids is that they have an extremely low vapor pressure. Within the last twenty
years, research involving these unique liquids has grown exponentially. Ionic liquids have shown
potential as green solvents, electrochemical agents, lubricants and compressor fluids. As more and more
ionic liquids are being manufactured, it is often difficult to obtain physical and chemical data needed to
perform feasibility tests. Before an ionic liquid can be implemented into an industrial process, certain
information must be known. For example: how it reacts with common chemicals, the density at different
temperatures, viscosity, hygroscopicity, etc. Here I analyze the effect that water content has on the
viscosity of certain ionic liquids containing the tetrafluoroborate anion.
The project consisted of two parts. The first part was to measure the viscosity of multiple ionic
liquids containing no more water than that present from the manufacturing process. The ionic liquids
used were 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), 1-methyl-3-octylimidazolium
tetrafluoroborate ([Omim][BF4]), and 1-butyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide
([BMPIm][Tf2N]). After some measurement discrepancies were observed, the capillary viscometer was
calibrated using different concentrated solutions of sucrose. The constants derived from this
experimentation were slightly different than those measured by the company and were determined to be
more accurate. After the initial viscosities were measured at 10°C, 20°C, 25°C, 30°C, 40°C and 50°C,
measurements of viscosity and water content were taken at twenty four and forty eight hours. The results
showed little change in the viscosity of [BMPIm][Tf2N], when compared to changes observed in the
liquids containing BF4.
The second step will be to take [Bmim][BF4] and [Omim][BF4] and introduce a specific amount
of water, via water saturated nitrogen gas, in order to analyze the magnitude of the effect that an increase
in water content will have on the viscosity. Water content analysis will be performed by a Karl Fischer
Titrator (Metrohm 795 Titrino).
In the future ionic liquids containing different cations in hand with the tetrafluoroborate anion
would like to be investigated, giving us a better idea as to the role that the specific anion plays in the
affect of water content on the viscosity. It would also be beneficial to compare the affect of water content
on other physical properties besides viscosity. This information will help to determine the feasible uses
of ionic liquids in not only industry, but perhaps academic and personal applications as well.
Clarkson University, Chemical Engineering/Pre-Med, Class of 2008
Honors/Environmental Science and Engineering REU
Ruth Baltus, PhD.
Oral Presentation