Degradation processes of protic ionic liquids for NH3 separation

Abstract

Protic ionic liquids (PILs) have been the focus of research both domestically and internationally because PILs have demonstrated improved NH₃ separation capabilities and have been applied to separate NH₃ from industrial tail gas. As the stabilities of PILs are overestimated, it is important to study their long-term stability as well as the degradation mechanism of PILs to slow down their degradation and improve their long-term stability. In this work, degradation experiments on 7 PILs were carried out at up to 120 °C for 600 h in N₂ and O₂ atmospheres. The impacts of different anions, cations, and NH₃ contents on the degradation processes of PILs were explored. High-performance liquid chromatography (HPLC) was used to quantify the degradation ratios of the PILs. The degradation products of PILs were identified and quantified via gas chromatography (GC)/mass spectrometry (MS), and the degradation mechanisms of the PILs were extrapolated according to the degradation products. Our results revealed that degradation occurred mainly in the cations, although the anions also affected the degradation processes of the PILs. The degradation ratios of the PILs decreased with an increase in the NH₃ content. This study on the degradation processes of PILs provides theoretical support for the industrial applications of PILs in NH₃ separation.