| Solubility of ionic liquids（ILs）in supercritical carbon dioxide（scCO2）is fundamental data for many fields such as material preparation,separation,catalysis reactions,and organic synthesis.Static method was employed to systematically determine the co-solvent-promoted solubility of ILs in scCO2 in this paper.The main research contents are shown as follows:First,solubility of ILs[Bmim]Ac,[Emim]Ac,[Bmim][NTf2]in scCO2/co-solvent were determined.Cosolvents included:ethanol,acetone,acetonitrile and DMSO.Temperature:40°C,50°C,60°C,pressure range:8-16 MPa.The effects of type of co-solvent,amount of co-solvent,temperature,and pressure on the solubility were investigated.The results showed that:（1）The addition of co-solvent can significantly enhance the ILs solubility.And the promotion effects of different co-solvents:ethanol>DMSO>acetone>acetonitrile,solubility increased with the increasing amount of co-solvent.The maximum solubility of[Emim]Ac is 4.99×10-3,which could be obtained when using 14.5 mol%ethanol at 40℃,14.59 MPa,and it was about 780 times that of same condition without co-solvent.（2）The effect of temperature on solubility was relatively complex,solubility ILs increased or decreased or maintained constant with increasing temperature.There was a cross pressure at solubility of[Emim]Ac in scCO2/DMSO,which is between 11 MPa and 12 MPa.（3）Solubility of ILs increased with increasing pressure.（4）The significance of the above four factors which influence the solubility followed the order:type of co-solvent>amount of co-solvent>temperature>pressure.In order to increase solubility of ILs further,double co-solvents systems were carried out and solubility of ILs[Bmim]Ac,[Emim]Ac,[Bmim][NTf2]in scCO2/ethanol/ethylene glycol were measured at 40°C.Pressure range was 8-15MPa,and the ethanol/ethylene glycol molar ratio were 5:1,20:3,10:1,and 20:1.The results showed that:（1）The addition of ethylene glycol promoted solubility of[Bmim]Ac relative to ethanol alone as co-solvent,but had no significant effect on the solubility of[Emim]Ac,and reduced solubility of[Bmim][NTf2].（2）In the double co-solvents systems,the promotion effect of the double co-solvents increased first and then decreased with increasing ratios of ethanol and ethylene glycol.Among the above four molar ratios,ethanol:ethylene glycol=10:1 exsited the best promotion effect.（3）The maximum solubility of[Bmim]Ac is 5.6×10-4,which could be obtained when using 14.5mol%ethanol/1.45 mol%ethylene glycol at 40℃,14.21 MPa,and it was about 70 times that of using ethanol alone as co-solvent.Finally,441 data of solubility of ILs in the scCO2/co-solvent were correlated by M-Christal,M-MST,M-AL,M-Bartle,M-JC,and M-SS equations in this paper.The results showed that the accuracy of M-Christal model was the highest（AARD=6.50%）.But M-MST model and M-Bartle model had the lowest correlation accuracy.A simplified M-Christal model was used to correlate the 79 data of solubility of ILs in scCO2/ethanol/ethylene glycol,and the accuracy of the simplified M-Christal model was high,AARD=3.97%. |
