Unifac Model For Ionic Liquid-Co （H₂） Systems:an Experimental And Modeling Study

In recent years, ionic liquids (ILs) have attracted increasing attention as novel green solvents due to their unique properties. It’s difficult and time-consuming to select the proper ionic liquids (ILs) due to their tunable chemical structures. The UNIFAC model for ionic liquids (ILs) has become very popular due to its simplicity and availability via modern process simulation softwares, which can play a guiding role for the actual work.This work mainly explores the the CO and H2gas liquid equilibriu m in ionic liquids at high pressure and low temperature. In this work,5and5new group binary interaction parameters (amn and anm) between CO (H2) and IL groups were obtained by correlating the solubility data in pure ILs at high temperatures collected from literature.We measured the solubility data of CO in pure ILs [BMIM][BF4],[OMIM][BF4],[OMIM][Tf2N] and mixed ILs50wt%[OMIM][BF4]+50wt%[OMIM][Tf2N], the solubility data of H2in pure ILs [EMIM][BF4],[BMIM][BF4],[OMIM][Tf2N], and in mixed ILs [EMIM][BF4](2)+[OMIM][Tf2N](3) and [BMIM][BF4](2)+[OMIM][Tf2N](3)(w3=0.2,0.5, 0.8) at temperatures from243.2to333.2K and pressures up to6.0MPa.It was found that the UNIFAC model can well predict the solubility in pure and mixed ILs at both high and low (below273.2K) temperatures.We also studied the structure-property relation for IL/CO (H2) sys tems, it can be seen that at the temperature293.2K the Henry’s consta nts of CO and solubility selectivity in ILs roughly exhibit the same tren d. The solubility of H2in ILs will increase with the increasing carbon number in the alkyl chain on cation.However, unlike CO, Henry’s cons tants of H2and solubility selectivity in different ILs roughly exhibit the reverse trend. Moreover, Henry constants and selectivity of mixed ionic liquids are between each value in the pure ionic liquids for both CO/CO2and H2/CO2system.We go a further step to investigate the influence of temperature on solubility selectivity of CO (H2) to CO2. A low temperature is not only favorable for increasing the solubility selectivity of both CO/CO2and H2/CO2gas pairs, but also for increasing the CO2solubility. This explains why the world-famous Rectisol process, in which the gas separation task is very strict, is operated at low temperatures.