Validation and Prediction of the Temperature-Dependent Henry's Constant for CO₂–Ionic Liquid Systems Using the Conductor-like Screening Model for Realistic Solvation (COSMO-RS)

Abstract

Henry's constant H of carbon dioxide in a number of ionic liquids (ILs) has been studied using the predictive method COnductor-like Screening MOdel for Realistic Solvation (COSMO-RS). Experimental H values for 14 CO2–IL systems spread over a temperature range of (283 to 333) K have been used to estimate the parameters λ1 and λ2 of the combinatorial term to calculate the chemical potential. The H values of CO2 in 18 other ILs have been validated and found to be in good agreement with the experimental data with a relative deviation of less than 10 %. Cation groups like imidazolium, pyridinium, ammonium, uronium, thiouronium, and phosphonium have been studied. A total of 12 anions such as L–, BF4 –, EtSO4 –, TFA–, OctSO4 –, Tf2N–, mFAB–, eFAB–, mFAP–, eFAP–, pFAP–, and bFAP– were studied to find the most favorable cation and anion combination for high CO2 solubility. It was observed that increasing the fluorination of organic anions containing fluoro alkyl groups gave lower Henry's constant values (following the trend TFA– > Tf2N– > mFAB– > eFAB– > mFAP– > eFAP– > pFAP– > bFAP–), thus showing higher CO2 solubility. Among the cations studied, phosphonium-based cations are found to be most promising for higher solubility. It was observed that the entropic effects (combinatorial) arising due to the size and shape of ILs play a major role in the estimation of H values, whereas the enthalpic effects (residual) arising due to molecular interactions have a minor but significant role. A correlation has been developed to predict the H of the [R n mim]+ cation-based IL by considering a reference value H 2 of [R2mim]+. A common predictive equation has been developed to determine the temperature-dependent H values of CO2 in any cation/anion combination of ILs.

Recent Advances in Anhydrous Solvents for CO2 Capture: Ionic Liquids, Switchable Solvents, and Nanoparticle Organic Hybrid Materials

“…Interestingly, imidazolium-based ILs exhibited remarkable CO2 capture capacity (Anthony et al, 2002;Kamps et al, 2003;Husson et al, 2010). Semi-empirical studies were also conducted to determine the Henry constant of several ILs (Mortazavi-Manesh et al, 2011;Sistla and Khanna, 2011). Overall, it was found that the shape and size of ILs played a major role in the value of the Henry constant of ILs.…”

“…They revealed that the anions played a critical role in interacting with CO2 (Cadena et al, 2004 (Anthony et al, 2005). Among the anions, those with fluoride have drawn significant interest (Aki et al, 2004;Bara et al, 2009;Sistla and Khanna, 2011). For instance, a detailed study on the effect of anions on CO2 capture was conducted focusing on the influence of fluorination on CO2 solubility in ILs (Aki et al, 2004…”

Systematic Investigation of the Photopolymerization of Imidazolium‐Based Ionic Liquid Styrene and Vinyl Monomers

“…To better understand the relationship between monomer structure and reactivity, the volume contributions of the nonpolymerizable monomer substituents were calculated using COSMOtherm, a thermodynamics software program that has previously been used to estimate IL properties . Using a set of 71 imidazolium‐based PIL monomers and NPILs with the Tf 2 N − anion, a regression analysis was used to model the volume contributions of different functional groups (e.g., vinyl, methylene groups) to the molar volumes of the monomers in our study.…”

“…Using TURBOMOLE, density functional theory (DFT) level calculations were used to obtain optimized structures for a series of 71 imidazolium cations with the Becke–Purdew (b–p) functional and the triple ζ valence polarization (TZVP) basis set . The computational thermodynamics software package COSMOtherm (v. C30_1301) was used to calculate molar volume for the series of ILs composed of these cations and the [Tf 2 N] − anion at the TZVP level, consistent with previous work using this software package to investigate IL properties . Numerical values corresponding to the number of functional groups were assigned to each IL and a regression analysis was used to determine molar volume contributions of IL structural components.…”

Atomistic modeling toward high-efficiency carbon capture: A brief survey with a few illustrative examples

“…Therefore, one can still expect to obtain useful trends from such calculations. There have been several recent reports on COSMO-RS computation of CO 2 solubility in different ILs [70][71][72][73][74] with the aim of uncovering trends that can serve as a guide to solvent optimization.…”