Drying of Ionic Liquid

Room Temperature Ionic Liquids (RTILs) are salts in liquid phase. Continuous use of
RTIL in a process may cause it to be contaminated with water and organic impurities over time
making it necessary to regenerate and purify the RTIL for recycle purposes. Thus, drying is
needed during pre-treatment and purification of IL solution before it can be used in any
application to reduce weight, increase ease of handling and eliminate unwanted effects of
moisture content towards IL properties. Drying process of ionic liquid is important since
moisture levels that are too high may affect performance and reliability in most applications such
as during synthesis of RTILs using aqueous solution to necessitate anion exchange and also in
concentrating Benfield solution for recycles purposes during removal of CO2. Therefore, to
obtain the most optimum condition of drying for ionic liquids, the study on kinetic of drying is
reported here by investigating the effects of drying temperatures, initial water content, types of
ionic liquid cation and anion and different drying methods on drying curves and their subsequent
kinetic parameters. Drying was done at 100, 120, 140, 160 and 180°C. The ratios of ionic liquid
to water used were 1:4, 1:3, 1:2, 1:1 and 2:1. Ionic liquids containing [bmim] cation with [SO4]-
or Phosphate-containing anion were used and drying methods applied were halogen lamp and
vacuum drying methods. Thermogravimetric analysis which measures change of mass over time
throughout the drying process was used to generate primary drying curves which were then
manipulated to get secondary kinetic data. The drying process mainly occurred during falling
rate period. Samples dried under higher temperature using vacuum drying have higher maximum
drying rates, lower final moisture contents, higher drying constants and shorter drying times. The
same result is observed for samples containing smaller anion and higher ratio of IL to water.