CO₂ capture with hybrid absorbents of low viscosity imidazolium-based ionic liquids and amine

In this work, nonaqueous binary absorbents were investigated for CO₂ capture by mixing conventional amines (i.e. monoethanolamine MEA, methyldiethanolamin MDEA) and ionic liquids. Four ionic liquids [BMIM]BF₄, [BEIM]BF₄, [BPIM]BF₄ and [BBIM]BF₄ were synthesized. The thermal stability of the ionic liquids was evaluated and viscosity was measured over the temperature range of 298–348 K. The CO₂ absorption performance of the pure ionic liquids was studied at ambient pressure and compared with the hybrid absorbents. The influence factors including temperature, stir rate and cycling numbers were then investigated. Finally, the CO₂ absorption mechanism was verified using NMR spectroscopy. Results showed that additional amine could greatly promote the CO₂ absorption performance of ionic liquids and mixed absorbents revealed different CO₂ absorption behavior depending on the amine type. This work proved that the mixed absorbent MDEA + [BEIM]BF₄ yields high cycling CO₂ capacity, energy saving, good regenerability and especially, low viscosity.