Monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA) and triethanolamine (TEA) are used in industrial processes for CO2 capture. However, these substances have some disadvantages because they are volatile, oxidised easily and their regeneration consumes large amounts of energy. The objective of this work was to study the thermal behaviour of these species. Utilising thermogravimetry, it was possible to study the kinetics of their thermal decomposition/volatilisation, enabling the estimation of the activation energy (Ea) and other kinetic parameters. Other techniques were also utilised for the characterisation of these materials: elemental analyses and gas chromatography coupled with mass spectrometry (GC/MS). TEA had the highest thermal stability of the ethanolamines studied. The thermal decomposition of DEA occurred in two steps: the first was due to an intramolecular reaction producing MEA and ethylene oxide and the second was the decomposition of residual material. The order of thermal stability is: primary amine<secondary amine<tertiary amine. However, the efficiency of CO2 capture is inversely related to the thermal stability. Steric impediment inhibits the reaction between the ethanolamine and CO2. Thus, although MEA is less stable than the other ethanolamines, it is the species that with the greater CO2 capture efficiency.
