Investigation of Nonidealities through an Extended Flory-Huggins Model of Ionic Liquid Mixtures with Ammonia

The phase behavior of ionic liquids and ammonia is critical due to their application in various fields such as sorption-based heating/cooling cycles and direct ammonia capture. To date, various ionic liquids have been developed and investigated to enhance the solubility of ammonia without compromising the reversibility due to recycling concerns and various thermodynamic models have been used to correlate the experimental vapor-liquid equilibria data. Surely, high ammonia sorption capacities are required and understanding the interaction between ammonia and ionic liquids can lead to synthesizing targeted ionic liquids for ammonia. In this study, we developed an extended Flory-Huggins model on ammonia and imidazolium-based ionic liquid systems, where both combinatorial and residual terms are considered, to understand the interaction between ammonia and ionic liquids. The results showed that the nonidealities in ammonia and imidazolium-based IL mixtures are due to both entropic and enthalpic contributions. Therefore, increasing the size of the IL would not be enough to achieve higher solubilities. A deeper understanding of the molecular-level interaction between ionic liquids and ammonia can be investigated via molecular simulations.