Investigation on vapor–liquid equilibria for binary systems of metal ion-containing ionic liquid [bmim]Zn2Cl5/NH3 by experiment and modified UNIFAC model

• Vapor pressures of [bmim]Zn2Cl5/NH3 are measured with total uncertainty less than 4.3%.
• Experimental data are correlated to modified UNIFAC model with maximum RD less than 5%.
• Ammonia solubility in [bmim]Zn2Cl5 is much higher than that in other ionic liquids.
• Ammonia solubility in [bmim]Zn2Cl5 is a little lower than that in ZnCl2.
• [bmim]Zn2Cl5/NH3 may be useful in absorption refrigerators and heat pumps.

Total pressures of binary solutions of [bmim]Zn2Cl5 (1)/NH3 (2) at ammonia mole fractions of x2 = (0.83–0.94) for T = (323.15–563.15) K at interval of 20 K were measured by a static method. The experimental data were correlated by a modified UNIFAC model involving four groups and the new binary interaction parameters were obtained. The measurement uncertainties and the maximum deviation of the correlation are lower than 4.3% and 5%, respectively. It is found that the addition of metal ion-containing ionic liquid [bmim]Zn2Cl5 can sharply reduce the ammonia pressure. The ammonia partial pressures of [bmim]Zn2Cl5/NH3 solutions were compared with that of ZnCl2·6NH3 and four binary solutions containing different ionic liquids. It is indicated that the solubilities of ammonia in [bmim]Zn2Cl5 is higher than that in other ionic liquids but lower than that in ZnCl2. This work suggests that [bmim]Zn2Cl5/NH3 may be useful in absorption refrigerators and heat pumps.