Fast CO2 desorption in amine solution using imidazole-based Brönsted acidic ionic liquids as green and efficient catalysts

Abstract

To encourage the industrial implementation of amine-based CO₂ capture technology, it is essential to effectively minimize the energy consumption for solvent regeneration. Herein, twelve different imidazole ionic liquids (ILs) were employed to catalytically boost CO₂ desorption in CO₂-rich monoethanolamine (MEA) solutions. These ILs involved [Mim]HSO₄, [Mim]NO₃, [Mim]H₂PO₄, [Mim]PTSA, [Emim]HSO₄, [Bmim]HSO₄, [HSO₃-Bmim]HSO₄, [Bmim]PF₆, HOOCMIMCl, AOEMIMPF₆, AOEMIMBF₄, and AOEMIMNTF₂. Most suggested IL catalysts facilitated the CO₂ desorption process, with HOOCMIMCl indicating the highest catalytic performance. In particular, HOOCMIMCl could raise the CO₂ release rate by 36.7% and cut down the relative heat duty by 38.6%. HOOCMIMCl maintained high stability after ten CO₂ absorption–desorption cycle tests. HOOCMIMCl also had no negative effect on the CO₂ absorption rate in fresh MEA solution. CO₂ absorption in MEA solutions. The primary causes of the HOOCMIMCl catalyst’s remarkable catalytic activity are its highly acidic site and low viscosity. Furthermore, based on the characterization results of FT-IR and ¹³C NMR, a prospective IL-catalyzed CO₂ desorption mechanism was presented. Because acid IL catalysts can be directly applied to existing CO₂ capture systems without necessitating equipment modification, these findings proved that they present significant opportunities for industrial CO₂ capture implementations. This work provides a workable strategy to lower the regeneration heat duty and operation cost for CO₂ capture technology in practical applications.