Comparison of CO₂ absorption performance between methyl‐di‐ ethanolamine and tri‐ethanolamine solution systems and its analysis in terms of amine molecules

Abstract

The present study analyzes the features of chemical CO2 absorption using tertiary amine solvents by comparing the absorption performance and electrical properties between methyl‐di‐ethanolamine (MDEA) and tri‐ethanolamine (TEA) systems. The results are mostly attributed to the different structures of the two amine molecules. Absorption performance is significantly affected by the molecular structure and water concentration in the amine solution. The absorption performance of the MDEA system is better than that of TEA, which is basically ascribed to the MDEA molecule's more asymmetric and irregular shape than that of TEA, which thus enhances the catalytic activity of MDEA and the reactivity of the −OH moiety in water. The difference of electrical properties such as ionic conductivities (ICs) of the two protonated amines and real ionic activity coefficients (RIAC) between the two systems might be also caused by the different molecular structures of the two amines. The IC of protonated MDEA is estimated to be 23.70% higher than that of protonated TEA, because of the higher ionic mobility and charge density of MDEA. The RIAC of the MDEA system is higher than that of TEA, which is explained by the different physicochemical interactions between the molecules in the two systems. Since water is one of the reactants in the absorption, its concentration in solution significantly affects the results of the systems. In addition, the absorption using tertiary amine is a base‐catalyzed reaction, and thus variations of the overall absorption rate follow a parabolic curve. Therefore, it is maximized to be 14.2 and 9.8 mmol CO2·L−1·min−1 in the 15 wt% MDEA and TEA solutions, respectively. Finally, the correlated equations for in situ estimation of chemical absorption capacity by electrical conductivity measured during the absorption are derived in the two systems. © 2021 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons, Ltd.

The Ratio of Chemical and Physical CO2 Absorption Capacity in Triethanolamine and Methyl-diethanolamine Solution Systems

“…EC calculated in this manner is represented as calculated EC (EC c ) to differentiate from measured EC (EC m ), which is practically and directly measured during the absorption. The λ i and z i values of the four ions in the solutions are summarized in Table , and the λ i values of TEAH + and MDEAH + used for the calculation were our previously reported values. , …”

“…The λ i and z i values of the four ions in the solutions are summarized in Table 2, and the λ i values of TEAH + and MDEAH + used for the calculation were our previously reported values. 27,28 By applying these set values to eqs 7 and 8, k o and IS were respectively calculated. Then, γ was calculated using either eq 9 or 10 according to the ranges of calculated IS values, after which EC c was finally estimated.…”

Interrogating the chemical mechanism for carbon dioxide (CO2) reactivity in aqueous tertiary amine solutions: Can a simple parallel hydration reaction mechanism work?

“…Global warming is becoming a critical issue in 21st century therefore ways to exploring alternative clean energy and reducing greenhouse gases emissions are emerging in recent years 1–3 . Cyclic chemical absorption/regeneration process is the most mature and widely utilized treatment and separation technology for the removal of carbon dioxide (CO 2 ) from industrial exhaust gas streams for the purpose of reducing greenhouse gas emission 4–7 . The alkanolamine solutions are used frequently for the chemical absorption‐based CO 2 capture process in fossil‐fuel‐fired power industry 8–12 .…”

“…[1][2][3] Cyclic chemical absorption/regeneration process is the most mature and widely utilized treatment and separation technology for the removal of carbon dioxide (CO 2 ) from industrial exhaust gas streams for the purpose of reducing greenhouse gas emission. [4][5][6][7] The alkanolamine solutions are used frequently for the chemical absorption-based CO 2 capture process in fossil-fuel-fired power industry. [8][9][10][11][12] The large amount of energy required to regenerate the solvent is one of the key characteristics that hindered the wide application of the amine-based CO 2 capture system.…”