Prediction of carbon-dioxide activity coefficient for solubility in ionic liquids using multi-non-linear regression analysis.

Activity coefficient values offer insight into the intermolecular interactions between the solute and the solvent and the deviation from the ideal behavior. CO₂ capture from different industrial processes is a globally pertinent issue and the search for suitable chemicals is required. To address the issue, knowledge of activity coefficient values is crucial for CO₂ separation-based process. In this regard, a correlation is developed that predicts the coefficient of CO₂ activity in ionic liquids by multi-nonlinear regression analysis. The correlation is developed between the pressure range of 1–50 bar and the temperature range of 298.15–33.15 K for mole fractions of 0.3, 0.5, and 0.7. 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.