A comparative kinetics study of CO₂ absorption into aqueous DEEA/MEA and DMEA/MEA blended solutions

Abstract

The kinetics of CO2 absorption into aqueous solutions of N,N‐diethylethanolamine (DEEA), and N,N‐dimethylethanolamine (DMEA), and their blends with monoethanolamine (MEA) have been studied in a stopped‐flow apparatus. The kinetics experiments were carried out at the concentrations of DEEA and DMEA varying from 0.075 to 0.175 kmol/m3, respectively, and that of MEA ranging between 0.0075 and 0.0175 kmol/m3, over the temperature range of 293–313 K. Two kinetics models are proposed to interpret the reaction in the blended amine systems and the results show that the model which incorporates the base‐catalyzed hydration mechanism and termolecular mechanism resulted in a better prediction. Furthermore, the kinetics behaviors of CO2 absorption into two blended systems are comprehensively discussed according to their molecular structures. It can be concluded that the interaction between tertiary amines and primary amines as well as the alkyl chain length of tertiary amines have a significant influence on the kinetics. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1350–1358, 2018

Density, Viscosity, and Excess Properties of Ternary Aqueous Mixtures of MDEA + MEA, DMEA + MEA, and DEEA + MEA

“…The work performed by Kim and Savage [17] on reaction kinetics of CO2 absorption in aqueous DEEA claimed that DEEA has a higher reaction rate than MDEA. Alongside the results found by Henni et al [18] on kinetics of DMEA, it was observed that DMEA and DEEA have a higher absorption performance compared to MDEA [9]. Chakravarty et al [19] demonstrated that CO2 absorption can be enhanced by adding a primary or secondary amine to the tertiary amine without changing the stripping characteristics.…”

“…The main disadvantage of MEA is that it requires a high amount of energy to release CO2 during the stripping. Tertiary amines like N-methyldiethanolamine (MDEA), dimethylethanolamine (DMEA), and diethylethanolamine (DEEA) have a low heat of reaction, which lowers the energy requirement in the stripping process [9][10][11]. MDEA is traditionally used for CO2 removal at high pressures.…”

“…Chakravarty et al [19] demonstrated that CO2 absorption can be enhanced by adding a primary or secondary amine to the tertiary amine without changing the stripping characteristics. Studies have been performed to investigate the performance of aqueous blends of tertiary and primary amines in CO2 absorption [9,[20][21][22]. Conway et al [21] showed improvements in the cyclic capacity of DMEA + MEA + H2O and DEEA + MEA + H2O mixtures compared to aqueous MEA mixtures.…”

Kinetics and new mechanism study of CO2 absorption into water and tertiary amine solutions by stopped‐Flow technique

“…The observed first‐order reaction rate constant ( k obs ) was determined by using a stopped‐flow apparatus (SF‐61DX, Hi‐Tech Scientific, Ltd. [United Kingdom]), which was the same as in our reported work . Two seal syringes were first filled with pure water (or aqueous amine solution) and aqueous CO 2 solution, respectively.…”

“…Tertiary amines have therefore attracted the attention of many researchers, because of their high CO 2 absorption capacities, resistance to degradation and corrosion and considerably lower energy consumption for solvent regeneration. These advantageous properties are due to the fact that tertiary amine cannot directly react with CO 2 in aqueous solutions to produce carbamate, while the primary and secondary amine do . However, the wide use of tertiary amines has been impeded by their slow reaction rate with CO 2 , which would result the requirement for a gigantic scale of absorber.…”