Title : Investigation of physical properties and carbon dioxide solubility in tetramethylammonium bromide and tetraethylammonium bromide ionic liquids solutions using multi-non-linear regression analysis
Abstract:
Carbon dioxide is a major greenhouse gas that is responsible for global warming and renders harmful effects on the atmosphere. The unconstrained release of CO2 into the atmosphere should be prevented and various techniques have been developed in this regard to capture CO2 using different solvents and other compounds. Ionic liquids are a suitable candidate to capture CO2 due to their better solubility behaviour. In this work, two ionic liquids namely tetramethylammonium bromide (TMAB) and tetraethylammonium bromide (TEAB) are employed experimentally to capture CO2 and investigate their solubility behaviour. The study is performed at the temperature values of 303 K, 313 K, and 323 K and the pressure values of 5, 10, 15, and 20 bar equivalent to 0.5, 1.0, 1.5, and 2.0 MPa respectively. The concentrations of both ionic liquid solutions are 2.5 wt%, 5.0 wt%, and 10.0 wt%. The solubility results are considered in terms of mol fraction which is the ratio of moles of CO2 captured per moles of ionic liquid. The density and viscosity values are also determined for both compounds at respective conditions. COSMO-RS is used to generate the sigma profile, sigma surface, and Henry’s constant of the ions involved in the study. CO2 is found to be soluble in both ionic liquids, but TEAB showed better solubility. Outliers’ analysis is performed using the boxplot method to determine the suitability of ranges of the selected input parameters. The preceding literature does not predict the activity coefficient in relatively lower to higher temperature and pressure ranges for CO2 solubility in ionic liquids. Initially, the activity coefficient values from COSMO-RS were obtained and compared with the correlation results. The COSMO-RS and the correlation predicted results were subsequently validated with the experimental data. The average absolute error (AAE%) of the predicted correlation values is 19.53% while the root mean square error (RMSE) value is 0.465. The correlation can be used in the future to predict the CO2 activity coefficient values in ionic liquids to facilitate qualitative analyses of their CO2 capture efficiency.
