Thermodynamics and kinetics of novel amino functionalized ionic liquid organic solvent for CO2 capture

Abstract

The main disadvantage of commercial absorption solution for CO2 capture from flue gas is extensive energy consumption. A novel amino-functionalized ionic liquid (AFIL) organic solution of tetraethylene pentamine 2-methylimidazolium/N-propanol/ethylene glycol ([TEPAH][2-MI]/NPA/EG) is considered as a promising candidate absorption system because of its efficient CO2 capture performance and low energy consumption. The thermodynamics and kinetics studies are very essential for evaluating the absorbent and its potential of future practical industrial application. In this work, the performance in these two aspects of [TEPAH][2-MI]/NPA/EG solution were investigated. The regeneration energy consumption was 2.98 GJ·t−1 CO2, which was 21.6% lower than that of benchmark monoethanolamine (MEA) aqueous solution, and the energy saving advantage was embodied in sensible heat and latent heat. Kinetic analysis showed that chemical reaction of CO2 absorption into [TEPAH][2-MI]/NPA/EG solution took place in the pseudo-first-order reaction. The reaction rate constant and enhancement factor increased with the increase of absorption temperature, while those showed a decreasing trend with the increase of absorption loading. The relation between the second-order rate constant and temperature was expressed as k2=5.6192×108exp-3111.6T, and the activation energy was further calculated as 25.87 kJ·mol−1. Compared with those of MEA and several traditional ionic liquid solutions, these parameters indicated a stronger reaction ability of the novel system. Moreover, the mass transfer resistance of gas and liquid phase changed constantly during the absorption process, and the dominant role of mass transfer resistance gradually changed from the gas phase to liquid phase. The thermodynamics and kinetics of CO2 capture revealed that the [TEPAH][2-MI]/NPA/EG solution had an excellent application potential in the future.