CO2 capture from flue gas at high temperatures by new ionic liquids with high capacity

Abstract

Room-temperature ionic liquids (ILs) are widely investigated to capture CO₂ from flue gas and can capture a large amount of CO₂. However, almost all of the previous studies on the absorption of CO₂ by ILs were carried out at low temperatures, less than 60 °C and even at room temperature. When the temperatures reach the real flue gas temperatures, from 110 °C to 140 °C, these ILs might hardly absorb CO₂, as high temperatures decrease the CO₂ capacity. Therefore, it is necessary to design new task specific ILs to capture CO₂ at flue gas temperatures with high absorption capacity. In this work, a new type of polyamine based ILs were developed to absorb CO₂ from simulated flue gas at high temperatures and ambient pressure with large absorption capacities up to 0.944 mole ratio or 0.176 mass ratio of CO₂ to IL at 110 °C. These ILs could be easily synthesized by neutralization of polyamines and organic acids, and the number of amido groups on the ILs can be easily controlled. The CO₂ absorption is influenced by temperature, CO₂ volume fraction in the flue gas, and the number of amido groups on the ILs. Also a possible mechanism for the CO₂ absorption has been proposed.