Study on the effectiveness of ionic liquid-based biphasic amine solvent in removing H₂S, NH₃ and CO₂ from biogas and its influential characteristics

The biphasic amine solvent based on ionic liquid could effectively improve the efficiency of carbon dioxide capture and regeneration, greatly reduce the energy consumption of regeneration, and hold an excellent application prospect in the field of large-scale biogas upgrading. In this work, a biphasic mixed amine system consisting of Methyl monoethanolamine (MMEA), N-methyldiethanolamine (MDEA), and 1-butyl-3-methylimidazolium tetrafluoroborate (BF) was prepared for the removal of trace components and CO2 during biogas upgrading and compared with traditional 30 wt% MEA and mixed amine solution of MMEA and MDEA for biogas upgrading. The results showed that H2S and NH3 would chemically react with the biphasic solvent and thus facilitate the removal of trace components, and that the reacted solution would not affect its regeneration characteristics and could basically be recycled at a regeneration temperature of 125 degrees C. In addition, the phase separation efficiency of the biphasic agent was not affected by the introduction of trace components, and all reaction products except the ionic liquid were enriched in the rich phases and the carbon enrichment rate reached about 98%, which reduced regeneration energy consumption by 44.07% compared to 30 wt% MEA. Finally, the mechanism of phase separation of reaction products and ionic liquids was discussed in the context of quantum chemical calculations, and the importance of intermolecular van der Waals forces in the phase separation process was clarified, and the reasons for the appearance of phase separation phenomena were explained.