Thermal Conductivity of Metastable Ionic Liquid [C₂mim][CH₃SO₃]

Area of Science:

• Materials Science
• Chemical Engineering
• Thermodynamics

Background:

• Ionic liquids are proposed as advanced engineering fluids for heat transfer applications.
• Current heat transfer fluids degrade above 200°C and present environmental concerns.
• 1-ethyl-3-methylimidazolium methanesulfonate ([C2mim][CH3SO3]) exhibits favorable thermophysical and toxicological properties.

Purpose of the Study:

• To investigate the phase behavior of 1-ethyl-3-methylimidazolium methanesulfonate, specifically liquid metastability below its melting point.
• To accurately measure the thermal conductivity of this ionic liquid across a relevant temperature range.
• To determine a precise melting temperature for [C2mim][CH3SO3].

Main Methods:

• Accurate thermal conductivity measurements were performed between 278 K and 355 K.
• Experimental data were analyzed to identify liquid metastability and phase transitions.
• Standard thermal conductivity models were employed for comparison.

Main Results:

• A new melting temperature of 307.8 ± 1 K was determined for [C2mim][CH3SO3].
• Experimental results support the existence of liquid metastability in the solid-phase region.
• Thermal conductivity was measured with an estimated uncertainty of 2% at a 95% confidence level.
• Existing thermal conductivity models failed to predict the experimental data accurately.

Conclusions:

• 1-ethyl-3-methylimidazolium methanesulfonate exhibits liquid metastability, allowing its use as a heat transfer fluid below its melting point.
• The findings expand the potential operating temperature range for this ionic liquid.
• Accurate thermal conductivity data are crucial for modeling and application of novel heat transfer fluids.