The structure–activity relationship for CO2 absorption heat of chain diamines: Effects of amino types, methyl/ethyl groups, and chain lengths

Chain diamines, exhibiting favorable CO 2 capture properties, including a large absorption capacity and a high absorption rate, have been extensively utilized in CO 2 capture technology. It has been demonstrated that the molecular structure of chain diamines has an impact on CO 2 absorption properties. The importance of absorption heat as a main component of regeneration energy consumption can not be ignored. However, the influence of the chain diamine molecular structure on CO 2 absorption heat remained unclear. In this study, twelve chain diamines were examined to investigate their structure–activity relationship with CO 2 absorption heat. The results indicated that chain diamines with a high percentage of secondary or tertiary amino groups had a low CO 2 absorption heat. Chain diamines with methyl groups on tertiary amino groups demonstrated a diminished CO 2 absorption heat than those with ethyl groups. Compared to amino types and methyl/ethyl groups, chain lengths had a slight effect on the CO 2 absorption heat of chain diamines. Chain diamines containing two carbon atoms exhibited a slightly low CO 2 absorption heat. Furthermore, it was observed that TMDEA, with two tertiary amino groups, exhibited a high CO 2 equilibrium solubility (0.98 mol CO 2 /mol amine) and a low CO 2 absorption heat (57.52 kJ/mol). The findings of this work are of significant relevance for the screening and development of low energy-consuming chain diamines suitable for CO 2 capture industrial applications.