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Monte Carlo Simulations of Pure and Mixed Gas Solubilities of CO2 and CH4 in Nonideal Ionic Liquid–Ionic Liquid Mixtures
journal contribution
posted on 2019-08-23, 17:49 authored by Utkarsh Kapoor, Jindal K. ShahThe knowledge of
mixed gas solubility in ionic liquids at high
pressures, which becomes relevant in applications such as tertiary
oil recovery and landfill gas utilization, is critical for the design
of gas separation technologies. In this study, we examine ionic liquid
mixtures for tuning the solubility of carbon dioxide (CO2) and methane (CH4). Using Gibbs ensemble Monte Carlo
simulations, absorption isotherms of pure CO2 and CH4 are computed in the binary ionic liquid mixtures containing
the common cation 1-n-butyl-3-methylimidazolium [C4mim]+ and the anions chloride Cl– and bis(trifluoromethanesulfonyl)imide [NTf2]− using five molar compositions at 353 K and the pressures ranging
from 1 to 100 bar. Additionally, mixture gas solubilities of CO2 and CH4 with the starting gas phase mole ratios
of 5:95 and 15:85 at a total pressure of 100 bar are determined and
compared with the ideal predictions obtained from the solubilities
calculated in pure ionic liquids. Results show that the mixture solubilities
deviate from the ideal mixing rule at high pressures with improved
solubilities in ionic liquid mixtures having up to 10% of [C4mim][NTf2] in [C4mim]Cl. Furthermore, for the
entire ionic liquid mixture composition range, the CO2/CH4 solubility selectivities exhibited a nonlinear behavior.
Interestingly, simulated CO2/CH4 solubility
selectivities at the mole ratios of 05:95 and 15:85 do not differ
significantly from the ideal solubility selectivities suggesting independent
gas absorption, except for 05:95 at 10% of [C4mim][NTf2] in [C4mim]Cl. Thus, there is a potential for
improving CO2/CH4 selectivity in pure [C4mim]Cl with the addition of a small amount of [C4mim][NTf2] ionic liquid.