Gas Capture By Ionic Liquids:Experimental And Predictive Thermodynamic Model Study

The capture of carbon dioxide (CO2) and carbon monoxide (CO) by ionic liquids (ILs) and the mixture of ILs and zeolitic imidazolate frameworks (ZIFs) was proposed at low temperature in this work. Firstly, ZIF-7 and ZIF-8 were prepared with solvothermal methods, and the structure and appearance of the obtained ZIFs were characterized by X-ray diffraction (XRD).The adsorption of CO2 and CO in ZIF-7 and ZIF-8 was calculated by GCMC (Grand Canonical Monte Carlo) method in Materials Studio simulation software. The comparison of simulation results and literature data was used to prove the information including unit cell and force field details in simulation process to be correct. The solubility of CO2 in [BMIM][BF4] (1-butyl-3-methylimidazolium tetrafluoroborate) at temperature 298.2 K and CO in [BMIM][BF4] at temperature 293.2 K using isochoric saturation method was measured, and the experimental results were compared with the literature data to verify the accuracy of experimental method.The solubility of CO2 and CO in [BMIM] [BF4] was measured at fives temperatures (298.2,288.2,273.2,258.2, and 243.2 K) and pressures up to 35 bar. The prediction data by UNIFAC are close to the experimental results. The ARDs (average relative deviation) between the predicted and experimental data are 4.47% for CO and 7.98% for CO2, respectively, ensuring the valid application of UNIFAC model.Then the solubility of CO2 in mixtures of ILs and ZIFs ([BMIM][BF4]+ ZIFs-7, wZIF-7= 0.05 and 0.10; and [BMIM][BF4]+ZIF-8, wZIF-8= 0.05 and 0.10) and CO in ILs and ZIFs ([BMIM][BF4]+ZIF-7, wZIF-7=0.05,0.10, and 0.15; and [BMIM][BF4]+ZIF-8, wZIF.8= 0.05,0.10, and 0.15) were measured at a range of temperatures from 243.2 K to 298.2 K and pressures up to 35 bar. The results show that the addition of ZIFs into ILs can obviously increase gas solubility, and the enhancement effect of ZIF-8 is stronger than that of ZIF-7. Moreover, the lever rule combining UNIFAC model and GCMC simulation together was used to predict the CO2/CO solubility in the ILs and ZIFs mixtures. The predicted results agree well with experimental data, indicating the applicability of predictive model established in this work for ILs-ZIFs-CO2/CO systems.