Evaluating diethanolammonium chloride as liquid solvent for gas separation from experiments and theoretical calculations

This study explored diethanolammonium chloride ([DEA]Cl) as a potential ionic liquid from low-cost and commercial ones for gas separation. There are three kinds of functional sites in [DEA]Cl: acidic -NH2+, hydrogen-bond -OH, and nucleophilic Cl-. The separation of NH3/N-2/H-2, SO2/CO2/N-2, and H2S/CO2/CH4 was considered, because the three mixtures are extensively involved in many industrial processes. The experimental results demonstrated that [DEA]Cl exhibited excellent ability to separate the mixture of NH3/N-2/H-2. The [DEA]Cl also exhibited the proper capacity to separate SO2/CO2/N-2, but the capacity of [DEA]Cl for the separation of H2S/CO2/CH4 was inferior. The theoretical calculations revealed that -NH2+ and -OH worked synergistically to contribute to the ability of [DEA]Cl for excellent separation of NH3 from NH3/N-2/H-2, with Cl- contributing to the proper separation of SO2 from SO2/CO2/N-2. This study provides experimental and theoretical basis for the industrial application of [DEA]Cl in the area of gas separation.