Journal of Chemical and Engineering Data, Vol.60, No.6, 1544-1562, 2015
Solubility and Diffusivity of CO2 in the Ionic Liquid 1-Butyl-3-methylimidazolium Tricyanomethanide within a Large Pressure Range (0.01 MPa to 10 MPa)
Ionic liquids (ILs) ate promising,solvents for carbon capture because of their high sorption, capacity and low regeneration, energy compared to conventional amine-based solvents. Previously, tetracyanoborate-based ILs have shown enhanced carbon dioxide (CO2) absorption capacity and absorption kinetics due to their low viscosity. In this work, the related IL 1-butyl-3-methylimidazolium tricyanomethanide ([bmim][tcm]) is studied for the first time as a solvent for CO2 capture. The physicochemical properties (e.g., density, viscosity, electrical conductivity, surface tension, thermal decomposition temperature, glass transition point) of pure [bmim)][tcm] were experimentally determined and successfully described using appropriate correlations. [Bmim][tcm] was found to be a low-viscous IL with a relatively high thermal stability (T-decomp = 473.15 K. The solubilities of CO (2) in [bmim][tcm] were measured at temperatures ranging from (288.15 to 363.15) K and a pressure range of (0.01 to 10) MPa using two different methods (volumetric vs gravimetric), which show good agreement with each other. [Bmim][tcm] shows higher solubilities and therefore, higher sorption capacity compared to other nonfluorous ILs. The Peng-Robinson equation of state was applied to correlate the experimental data. Henry's law constants (4 MPa to 13 MPa) and partial molar enthalpies of absorption (-14 kJ center dot mol(-1)) at different temperatures were also calculated from the measured solubility data. The diffusion coefficients of CO (2) in [bmim][tcm] were determined at temperatures ranging from (308.15 to 353.15) K using the gravimetric method only. The diffusivity data of CO2 in [bmim][tcm] (similar to 5 center dot 10(-10) m(2)center dot s(-1)) are comparable to those in other low-viscous ILs, and show that high rates of absorption are possible. Therefore, it can be concluded that [bmim][tcm] is a promising candidate for carbon capture.