Ionic liquids are known as environmentally benign solvents because of their low vapour pressure which minimise solvent losses during industrial operations. Recently they have been proposed for CO2 capture as alternative solvents to the more established alkanolamine systems. There are several reported works on using Ionic liquids for CO2 absorption. So far ionic liquids have not been used in industry due to some problems such as lower CO2 absorption capacity, higher viscosity and price compared to conventional amines. The use of mixtures of ionic liquids with alkanolamines is an interesting alternative since it combines the advantages of both systems.
In this work, an experimental investigation is carried out in order to evaluate the effects of an ionic liquid [bmim][acetate] addition on the absorption of CO2 in AMP a sterically hindered alkanolamine. The solubility studies were carried out in a semi-batch stirred cell reactor operated under various operating conditions. The reaction of CO2 with the mixture was monitored using online pH measurement system. The results are compared with CO2 absorption by AMP without IL. The addition of the ionic liquid resulted in a decrease of CO2 solubility. The magnitude of capacity reduction was proportional to the concentration of IL. This reduction in CO2 loading was accompanied by an increase in the overall rate of reaction. This increase in rate of absorption is probably due to the higher concentration of molecular CO2 in the liquid in presence of the IL.
Keywords: CO2 absorption, Ionic liquids, AMP, CO2 loading, Task specific ionic Liquids