Experimental and computational study of the thermal degradation of primary amines used in CO2 capture

• Published in: Chemical engineering science 2024-04, Vol.288, p.119786, Article 119786
• Main Authors: Ouyang, Yan, Liu, Qi, Luo, Tong, Luo, Qinlan, Xiao, Min, Gao, Hongxia, Liang, Zhiwu
• Format: Article
• Language: English
• Subjects: Carbon dioxide; DFT calculation; Primary amine; Structure–activity relationship; Thermal degradation
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2024.119786

•Thermal degradation of primary amines was studied experimentally and computationally.•Results show that the primary amines follow a similar thermal degradation mechanism.•The amine loss during the experiment was ranked as: AMB > MEA > 2-AP > 1-AP > AMP.•The ring closure is the limiting step in the thermal degradation of primary amine.•The methyl group at β-carbon hinders the ring closure reaction of 1AP. CO2 loaded amine polymerizes during solvent regeneration at temperatures above 100 °C, resulting in the deterioration of solvent performance. Herein, five primary amines were heated to 120, 135 and 150 °C with CO2 loading of 0.4C/N to study thermal degradation. It was found that 2-amine-1-butanol showed the greatest amine loss of 38.5 % after heating to 135 °C for 672 hrs while 2-amino-2-methyl-1-propanol was most stable with amine loss of 17.4 % under the same conditions. The degradation products were identified and the reaction pathway was studied through density functional theory (DFT) calculation. Furthermore, the transition state for ring closure and opening reactions was analyzed. The ring closure reaction to form oxazolidinones had a higher energy barrier, showing that it was the limiting step. This is further supported by the good agreement with experimental results. The structure–activity relationship showed the strong steric hindrance effect and the methyl group at β-carbon improved the amine stability.