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

Abstract

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/N₂/H₂, SO₂/CO₂/N₂, 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/N₂/H₂. The [DEA]Cl also exhibited the proper capacity to separate SO₂/CO₂/N₂, 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/N₂/H₂, with Cl⁻ contributing to the proper separation of SO₂ from SO₂/CO₂/N₂. This study provides experimental and theoretical basis for the industrial application of [DEA]Cl in the area of gas separation.