A strategy of development and selection of absorbent for efficient CO2 capture: An overview of properties and performance

CO2 absorption using benign cost-effective absorbents is an essential unit operation not only in the process industry for CO2 separation and recovery from industrial off-gas streams but also for direct absorption from air to reduce the carbon footprint. Several absorbents are identified, by researchers, with high CO2 capture efficiency due to their favorable chemical and physical properties, interaction mechanism with CO2, and low regeneration energy cost. However, with the current Environmental Protection Agency (EPA) norms, more efficient low-cost benign absorbents need to be developed. Hence, the primary aim of this work is to comprehensively review various factors which are recently being considered in determining all these crucial parameters for best absorbents selection. The merits and demerits for establishing the physical and chemical absorbents have been discussed. Absorbent properties such as structural, transportation, and chemical properties are also discussed, along with various methods used to determine them. The pKa value based absorbent selection methodology seems an ideal way for absorbent selection. Further, the role of contactors for absorption performance is also reviewed, with a significant focus on the mass transfer coefficients, and the anal that a circular microchannel reactor provides a 2-4 order of magnitude higher mass transfer coefficient value than a conventional reactor. The interaction mechanism of reactive absorbents has been discussed, as they show much better absorption kinetics. A comparative assessment of relative heat duties of these reported absorbents revealed that the catalyst doped, and blend amines systems provide lower regeneration heat duties. A relative cost of the absorption processes focusing on the recent ionic liquid solvent synthesis costs is described. Overall, this review provides a systematic insight that will assist researchers and engineers in understanding an absorption solvent's efficacy for CO2 capture comprehensively. (c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.

Automated summary

This article comprehensively reviews various factors that are recently being considered in determining the best absorbent selection for CO2 absorption. The merits and demerits of physical and chemical absorbents are discussed, along with the methods used to determine their structural, transportation, and chemical properties. The importance of mass transfer coefficients and the advantages of circular microchannel reactors in improving mass transfer coefficients are emphasized. The interaction mechanism of reactive absorbents and the relative cost of the absorption processes are also discussed.