A study of structure–activity relationships of commercial tertiary amines for post-combustion CO₂ capture

This work examined the relationship between the structure of various commercial tertiary amines and their activity in CO₂ absorption/desorption in terms of rate of CO₂ absorption, equilibrium CO₂ loading, pKa and heat of CO₂ absorption in order to establish possible guidelines for selection of tertiary amine components for amine blends. Results show that any electron donating group linked directly to the nitrogen atom increases their reactivity with CO₂. In addition, the presence of steric hindrance effect and good water solubility also show enhancements in activity. In contrast, the existence of a hydroxyl group leads to a decrease in all the activity of the tertiary amine. The heat of CO₂ absorption of tertiary amines, which is closely related to the regeneration energy, can be reduced by decreasing the number of hydroxyethyl groups or by positing the hydroxyl group at the proper carbon relative to the nitrogen atom.