New insights into the functional group influence on CO2 absorption heat and CO2 equilibrium solubility by piperazine derivatives

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-11, Vol.500, p.157528, Article 157528
• Main Authors: Tang, Xi, Xu, Bin, Jiang, Wufeng, Li, Xiaoshan, Gao, Ge, Wu, Fan, Luo, Cong, Zhang, Liqi
• Format: Article
• Language: English
• Subjects: CO2 absorption heat; CO2 capture; CO2 equilibrium solubility; Piperazine derivatives; Quantum chemical calculation
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.157528

•The structure–activity relationship between PZ derivatives with two amines and ΔHabs and αe.•Cyclic methyl side chains on the N atom of PZ derivatives decreased ΔHabs and increased αe.•PZ derivatives with cyclic methyl side chains, steric hindrance effect, and no hydroxy group are favorable for CO2 capture. Piperazine (PZ) derivatives which have been widely used in CO2 capture technology exhibit stable physicochemical properties, such as resistance to thermal degradation and low regeneration energy consumption. Both two parameters of CO2 absorbents, low CO2 absorption heat (ΔHabs) and large CO2 equilibrium solubility (αe), are important to CO2 capture performance. However, the influence of functional group types of PZ derivatives on their CO2 capture performance remained unclear. This research aimed to study the functional group influence on the ΔHabs and αe by PZ derivatives with two amines using experimental and quantum chemical methods. The results indicated that PZ derivatives with the ethyl side chain had larger ΔHabs and αe than those with the methyl side chain. The presence of the hydroxy group in PZ derivatives reduced the ΔHabs and the αe. The presence of cyclic methyl side chains on the N atom of PZ derivatives decreased the ΔHabs and increased αe at the same time. The findings show that PZ derivatives with cyclic methyl side chains, steric hindrance effect, and no hydroxy group are favorable for CO2 capture. Among the eight PZ derivatives, TEDA with lower ΔHabs (48.99 kJ/mol) and higher αe (0.917 mol CO2/mol amine) is an excellent absorbent. The results of this study are very important for screening efficient and low-energy consumption absorbents for CO2 capture.