Evaluation of Amine Solutions for CO2 Absorption by TOC/TN

Significance of Topic

Rising atmospheric CO2 concentrations are a major driver of climate change, prompting development of carbon capture, utilization, and storage (CCUS) technologies. Amine-based chemical absorption is well suited for low‐pressure CO2 streams such as flue gas and offers high reactivity. Reliable quantification of absorbed CO2 and monitoring of amine concentration are essential to optimize capture processes and reduce energy consumption.

Objectives and Study Overview

The article evaluates two amine solvents—2-amino-2-methyl-1-propanol (AMP) at 20 wt% and monoethanolamine (MEA) at 30 wt%—for CO2 absorption. By integrating a TNM-L total nitrogen module into a Shimadzu TOC-L total organic carbon analyzer, the study quantifies inorganic carbon (IC), total organic carbon (TOC), and total nitrogen (TN) before and after controlled CO2 exposure, demonstrating both capture efficiency and solvent integrity.

Methodology and Instrumentation

CO2 absorption experiments were conducted by flowing 4.74 vol% CO2 in N2 at 100 mL/min through 20 mL of each amine solution for 2 hours. Post-absorption samples were diluted (100× for IC, 500× for TOC/TN). IC was measured via acidification/sparging and infrared detection, isolating carbonate species. TOC was determined after removing inorganic carbon. TN was quantified using the TNM-L unit. Instrumentation included the Shimadzu TOC-LCPH analyzer with TOC/TN catalyst and TNM-L accessory.

Main Results and Discussion

• IC levels rose from ~0.001 %C to >1 %C for both AMP and MEA, indicating over 1000-fold increase in dissolved carbonate forms.
• TOC and TN measurements remained essentially unchanged, confirming minimal degradation or loss of amine concentration during CO2 uptake.
• AMP showed efficient conversion via the bicarbonate pathway (1:1 amine/CO2 stoichiometry), suggesting lower heat duty and faster kinetics compared to MEA’s bimolecular carbamate route (2:1).

Benefits and Practical Applications

• The combined TOC/TNM analysis enables direct quantification of CO2 captured as carbonate without interference from amine background.
• Stable TOC and TN readings allow real-time monitoring of solvent degradation and concentration, supporting process control.
• Methodology is adaptable to research and industrial settings aiming to optimize energy consumption and solvent management in CCUS operations.

Future Trends and Applications

• Development of advanced amine derivatives and blended solvents to further reduce regeneration energy and enhance absorption rates.
• Integration of online TOC/TN monitoring with automated process control for dynamic solvent management.
• Coupling with membrane and hybrid capture systems to achieve higher throughput and lower operational costs.
• Application in pilot and full-scale CCUS facilities for real‐time performance evaluation and regulatory compliance.

Conclusion

The Shimadzu TOC-L analyzer with TNM-L extension provides a robust analytical platform for quantifying CO2 uptake and monitoring amine solvent integrity. Significant IC increases confirm effective capture, while stable TOC/TN levels ensure accurate concentration control. This approach supports development of energy-efficient CCUS technologies and can guide both laboratory research and industrial implementation.

Reference

Shimadzu Corporation, "Evaluation of Amine Solutions for CO2 Absorption by TOC/TN", First Edition: March 2022.