Thermal degradation of amino acid salts in CO2 capture

The resistance of amine-based CO2 capture solutions to thermal degradation is a critical characteristic that helps to determine their potential for use as a post-combustion CO2 capture solvent. In this research, sodium salts of glycine, sarcosine, alanine and β-alanine were thermally degraded at 125 °C, 135 °C and 145 °C, respectively, to discover the structural reasons for their thermal stability. These four amino acids have enhanced thermal degradation rates compared to reference monoethanolamine (MEA) solvent. The stability order for amino acid salts tested to date is: sarcosinate > alaninate > β-alaninate. Steric hindrance at the amine group plays a positive role in protecting the amino acid against degradation. Calculated activation energies for the degradation processes are lower than that of MEA. β-Alaninate (β-Ala) thermal degradation generates β-Ala dimer (major degradation product), β-Ala dimer carbamate and tetrahydro-1,3-oxazin-6-one. The relative yields of these three β-alanine degradation routes are discussed.