Thermodynamic modeling the solubility of CO2 in pure ionic liquid using the UNIQUAC model and GE-EOS model

Sweetening processes are used to remove acid gases such as hydrogen sulfide and carbon dioxide from natural gas that is the main step in gas industry. Ionic liquids as a green solvent are used in gas absorption process to remove the acid gases. The ionic liquid present several advantages such as the similar melting points or nearing melting point to room temp, and negligible vapor pressure that caused to be non-volatile. Due to specific properties and solubility of many components such as inorganic, organic, polar and non-polar solutes in ionic liquids, this type of material is known as green solvent. Ionic liquids are widely used for separation processes like striping process in removal acid unit. In this work, the solubility of CO2 are studied in three ionic liquids of 1-butyl-3-methylimidazolium dicyanamide ([C4 mim][Tf2N]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([C4mim][Tf2N)] ) and 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide([C4mim][Tf2N)]) at 290-363k and pressure up to 74 Mpa. A thermodynamic model based on the Peng-Robinson and Modified Peng-Robinson equations of state with the Wong-Sandler mixing rule using the UNIQUAC activity coefficient model is applied. The results show that the present model gives good results so that the calculated data are in good agreement with the experiment.

Keywords:

ionic liquid , solubility , equation of state , thermodynamic model