Experimental and thermodynamic analysis of NH3 absorption in dual-functionalized pyridinium-based ionic liquids

A novel type of dual-functionalized pyridinium-based ionic liquids (ILs) with acidic protons and hydroxyl groups , were designed and synthesized for ammonia (NH 3 ) absorption. The NH 3 absorption isotherms in dual-functionalized pyridinium-based ILs at temperatures from 303.15 to 343.15 K and pressures up to 600 kPa were computed using gas-liquid equilibrium method. It revealed that 4-pyridinemethanol bis(trifluoromethane)sulfonamide [4-MeOHPy][NTf 2 ] showed the maximum NH 3 solubility of 3.43 mol NH 3 /mol IL at 313.15 K and atmospheric pressure, surpassing any nonmetallic ILs previously reported. Furthermore, the characteristics of isotherms under low pressures behaved an obvious chemical reaction between ILs and NH 3 , and all experimental solubilities were regulated by a reaction equilibrium thermodynamic model (RETM). The thermodynamic properties were further obtained to better understand the NH 3 absorption process. The results indicated that this model endorses the 1:1 (NH 3 -IL) mole ratio of chemical reaction mechanism and the reaction enthalpy is main driving force of NH 3 absorption in ILs.