CO2 capture performance and mechanism of blended amine solvents regulated by N-methylcyclohexyamine. (15th January 2021)

• Record Type: Journal Article
• Authors: Wang, Rujie; Liu, Shanshan; Li, Qiangwei; Zhang, Shihan; Wang, Lidong; An, Shanlong
• Is Part Of: Energy. Volume 215(2021)Part B
• Publication Date: 2021-01-15
• Subjects: CO2 capture -- Blended amines -- Hybrid amines -- Absorption rate -- Regeneration heat; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Energy consumption -- Periodicals; 333.7905
• DOI: 10.1016/j.energy.2020.119209
• Languages: English
• ISSNs: 0360-5442

Abstract

Abstract: Blended amine solvents are considered potential alternatives to monoethanolamine for CO2 capture, for the fast absorption kinetics of primary/secondary amine and low regeneration penalty of tertiary amine. In this research, blended amine solvents comprising N, N-dimethylcyclohexylamine (DMCA) and N-methylcyclohexyamine (MCA) were proposed. CO2 absorption increased the polarity of the products and ensured the absorbent remained homogenous throughout the absorption/desorption cycles. Through quantum chemical calculation, the low stability of MCA-carbamate was confirmed by a ΔΔG3 value of −6.41 kcal/mol, and a possible reaction route from carbamate to bicarbonate was revealed. Thus, the CO2 capacity of DMCA-MCA reached 0.875–0.985 mol CO2 /mol amine. Moreover, MCA exhibited considerably low forward energy barrier for zwitterion formation (2.7 kcal/mol), and the CO2 absorption of DMCA could be accelerated through the proton transfer reaction with the MCA-zwitterion. Accordingly, the total mass transfer coefficient of CO2 in DMCA-MCA approached 2.02 × 10 −10 mol/cm 2 s Pa, which was 1.2-fold higher than that of 5 M MEA. The total regeneration energy of DMCA-MCA blend was estimated at 2.20 GJ/t CO2, which was 44.9% lower than 5 M MEA. This study developed a novel DMCA-MCA blended solvent with rapid absorption rate, huge CO2 capacity and efficient regeneration for CO2 capture. Graphical abstract: Image 1 Highlights: The biphasic DMCA-MCA absorbent became homogenous at a CO2 loading above 0.41 mol/L. MCA-carbamate converted to bicarbonate and ensured a CO2 capacity near 1 mol/mol. MCA accelerated the CO2 absorption, leading to a faster mass transfer than MEA. The total regeneration energy was 2.20 GJ/t CO2, 45% lower than 5 M MEA.