Research on influencing factors and mechanism of CO2 absorption by poly-amino-based ionic liquids

Ionic liquids (ILs) are varieties of green solvents that can capture CO 2 effectively. In this research, five synthesized amino ILs were evaluated for their CO 2 absorption performance. Experimental results showed that more amino groups in ILs led to higher CO 2 absorption capacities. For factors such as temperature, gas flow rate, and water content, water content had the most significant impact on the capacity to absorb CO 2 . A CO 2 absorption capacity of 0.96   mol-CO 2 /mol-IL was achieved with [TETAH] + [BF 4 ] − , with the IL containing 0% water and a gas flow rate of 100   ml/min at 293   K. However, when the water content of [TETAH] + [BF 4 ] − reached 40%, CO 2 absorption capacity increased to as high as 2.04   mol-CO 2 /mol-IL. Also, the CO 2 absorption capacity of [TETAH] + [BF 4 ] − increased rapidly with temperature in the range of 283–333   K, but decreased at temperatures greater than 333   K. According to the absorption–desorption recycling experiment of IL 3#, the regeneration rates of ILs increase with water content from 0% to 40%, while raising temperature does not improve regeneration rates. The FT-IR, 13 CNMR, pH and conductivity characterization results indicate that CO 2 reacted with NH 2 and NH in [TETAH] + [BF 4 ] − and formed carbamate. Simultaneously, CO 2 reacted with H 2 O and released H + , thus enhancing the absorption of CO 2 . This has important implications for various projects.