Unifac Model For Ionic Liquid-Gas Systems

The application of UNIFAC model in the systems of ionic liqids and CO2gas is mainly studied in this paper, and the new group binary interaction parameters of UNIFAC model between CO2and21ionic liquid (IL) groups were obtained by means of correlating the solubility data of CO2in pure IL at different temperatures (above273.2K) exhaustively collected from literatures. UNIFAC model is not only enriched but also can be used to the systems of ionic liqids and CO2gas at above room temperature. Due to the gas absorpted in ionic liquids at the low temperature reported in the literature is few, so CO2solubility in the single IL ([OMIM][BF4] and [OMIM][Tf2N]) was measured at different pressures at low temperature (243.2,258.2,273.2K), and the results were predicted by UNIFAC model, it is found that the average relative deviation are2.54%,3.87%respectively. This indicates that UNIFAC model can be extended to single IL-CO2systems at low temperature from single IL-CO2systems at above room temperature. Besides, CO2solubility in the mixed ionic liquids [OMIM][BF4]+[OMIM][Tf2N] were also measured at different pressures at low temperature (243.2,258.2,273.2K), and the results were predicted by UNIFAC model and leverage law, it is excited to find the average relative deviations for two methods are small,8.59%for UNIFAC model,7.32%for leverage law. It extends the UNIFAC model to mixed ionic liquids-CO2systems. Moreover, UNIFAC model can be used to identify the structure-property relation between molecular structure of IL and CO2solubility, as the carbon number increases, the Henry’s law constants tend to decrease for all ILs as expected, however, it is surprising to find that when the carbon number increases to a certain degree, the Henry’s law constants approach a constant for all of the ILs investigated at298.15K.The application of UNIFAC model in IL-SO2systems is also studied in this paper, and the new group binary interaction parameters of UNIFAC model between SO2and5ionic liquid groups were obtained by means of correlating the solubility data of SO2from the published literature. It makes UNIFAC model parameters more richer and extends it to IL-sulfur dioxide systems at room temperature. Moreover, the predicted results by UNIFAC model, COSMO-RS model, and COSMO-thermX model are compared, in the most cases, COSMO-RS model underestimate the experimental values while COSMO-thermX overestimate the results, only the UNIFAC model predict best results. Moreover, the solubilities of SO2in different ionic liquids from the published works are slightly different at298.15K.