(490g) Solubility of Carbon Dioxide in the Ionic Liquid Alkyl-3-Methylimidazolium Tricyanomethanide ([Cnmim]-[TCM]) Using a Magnetic Suspension Balance

Ionic liquids are potential candidates for carbon dioxide capture to replace the use of amine-based solvents. Absorption of carbon dioxide in amine-based solvents is a well-established technology. However, their volatility and inherent problems associated with methanol and amine-based capture motivate research for new solvents. Ionic liquids are preferred because of their negligible vapor pressure, thermal stability and tuneability of properties by modifying their molecular structure. In this work, the solubility of carbon dioxide was measured in alkyl-3-methylimidazolium tricyanomethanide ([C_nmim]-[TCM]) ionic liquids using an advanced magnetic suspension balance (MSB; Rubotherm GmbH) over a wide temperature and pressure range (20 to 65 ^oC and up to 100 bar) respectively. The magnetic suspension balance contactlessly measures the sample weight at all specified temperatures and pressures. The measurements reported in this study include carbon dioxide solubility measurements in the ionic liquids [C_nmim]-[TCM] with n=2, 3, 6 and 8. In addition, the viscosities and densities of the same ILs ([C_nmim]-[TCM]) were measured. The viscosities were compared with simultaneously measured values with a Stabinger viscometer (Rotational Coaxial system).

The dependency of the carbon dioxide solubility in the [C_nmim]-[TCM] ILs were considered as a function of the alkylchain length of these ILs, temperature and pressure.

Vacuum drying at 50 ^oC for 8 hrs. of the respective ionic liquid samples was carried out prior to the carbon dioxide solubility measurements. The measured solubility of CO₂ in [C_nmim]-[TCM] were compared with the available literature data measured in a PVT cell. Furthermore, it was observed that the carbon dioxide uptake in [C_nmim]-[TCM] increases with the increase of the carbon chain length and pressure and with a solubility decrease with temperature. It was also found that the gravimetric approach to measure carbon dioxide solubilities in ([C_nmim]-[TCM]) is in good agreement with the PVT cell measurements.