(382ag) Prediction of the CO2 Solubility in Ionic Liquids: A Comparison between Cubic and Group Contribution Equations of State

The increasing demand for energy implies a dramatic increase in the usage of fossil fuels, e.g.: coal, oil and natural gas. Natural gas is considered as a primary heating source for domestic usage and as a “fuel” for electric power plants to produce electricity. The combustion of fossil fuels becomes a major concern due to their adverse effects on the environment, particularly related to the emission of carbon dioxide (CO₂), a major anthropogenic greenhouse gas (GHG). The CO₂ emissions to the atmosphere will continue to increase due to rise in fossil fuel consumption. It is observed that approximately 55% of global warming is caused by CO₂ emission to the environment [1, 2]. CO₂ capture and storage (CCS) is vital. However, a primary hurdle to commercialize the CCS process at industrial scale is the energy cost associated with CO₂ separation. Currently, the most commonly used commercial technique for removing CO₂ from the natural gas is the amine-based (alkanolamines) absorption process. These amines are commonly used solvents for CO₂ removal due to their high CO₂ absorption capacity as well as high reactivity with CO₂.The use of amine based solvent is questioned because of associated disadvantages including low thermal stability, loss of water into gas stream causing corrosiveness in pipelines, loss of volatile solvent, degradation and sensitivity of solvents [3,4]. However, ILs prove themselves as innovative solvents capable to efficient CO₂ removal.. Extensive experimental work was carried out to scrutinize the best ionic liquid in terms of CO₂ absorption capacity . However, the time and cost associated with the experimental techqniques limit the testing of a wide range of possible ionic liquids. Instead, a predictive phase equilibria model can accurately predict the solubility of CO₂ in ILs for varous ILs/CO₂ systems. In addition to the thermophysical properties, vapor/liquid equilibria were also predicted using group contribution equations of state over a range of T and P conditions. In this work, the solubility of CO₂ in imidazolium based ([C_nmim][TCM]) ionic liquids (with n = 2, 4, 6, 7, 8) was predicted by using the Group Contribution (GC) EoS. Moreover, interaction parameters between groups [mim][TCM] and were estimated by fitting the bubble point data of [bmim][TCM]. It was observed that the GC EoS was successful in predicting all the VLE data points within an absolute deviation of 15% compared to the experimental values. Moreover, Peng Robinson equation of state is also employed to calculate the solubility of CO₂ in various ionic liquids. The predictive accuracy of the GC EoS was compared with the PR EoS for various isotherms. It was concluded that for all isotherms the GC EoS performs better than the PR EoS.

References

[1] E. A. Parson and D. W. Keith, “Fossil Fuels Without CO 2 Emissions,” vol. 282, no. 5391, pp. 1053–1054, 1998.

[2] A. M. Wolsky, E. J. Daniels, and B. J. Jody, “CO2 capture from the flue gas of conventional fossil-fuel-fired power plants,” Environmental Progress, vol. 13, no. 3, pp. 214–219, Aug. 1994.

[3] J. C. Abanades, E. S. Rubin, and E. J. Anthony, “Sorbent Cost and Performance in CO ₂ Capture Systems,” Industrial & Engineering Chemistry Research, vol. 43, no. 13, pp. 3462–3466, Jun. 2004.

[4] M. Ramdin, T. W. de Loos, and T. J. H. Vlugt, “State-of-the-Art of CO ₂ Capture with Ionic Liquids,” Industrial & Engineering Chemistry Research, vol. 51, no. 24, pp. 8149–8177, Jun. 2012.