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Progress and trends in CO2 capture/separation technologies: A review

Alkanolamine solutions are frequently used as solvent for the removal of acid compounds from industrial gases (Kohl and Riesenfeld, 1979). Depending on the process requirements, e.g., selective removal of H2S, CO2-bulk removal, several options for alkanolamine based treating solvents with varying compositions of the solution have been proposed. In this paper an overview is presented of the mechanisms that have been proposed in literature and the kinetic data for the various reactions are critically evaluated. Conclusions on the applicability and restrictions are discussed along with perspectives. In addition white spots in the present knowledge are indicated. The reaction between CO2 and primary/secondary amines both in aqueous and non-aqueous solutions can be described over a wide range of conditions and amine concentrations with the zwitterion-mechanism as originally proposed by Caplow (1968) and reintroduced by Danckwerts (1979). All published results, both non-aqueous and aqueous solutions, amine-prom...

On the kinetics between co2 and alkanolamines both in aqueous and non-aqueous solutions. an overview

Alkanolamines are the most popular absorbents used to remove CO2 from process gas streams. Therefore, the CO2 reaction with alkanolamines is of considerable importance. The aim of this article is to provide an overview on the kinetics of the reaction of CO2 with aqueous solutions of alkanolamines. The various reaction mechanisms that are used to interpret experimental kinetic data – zwitterion, termolecular and base-catalyzed hydration – are discussed in detail. Recently published data on reaction kinetics of individual amine systems and their mixtures are considered. In addition, the kinetic behavior of several novel aminebased solvents that have been proposed in the literature is analyzed. Generally, the reaction of CO2 with primary, secondary and sterically hindered amines is governed by the zwitterion mechanism, whereas the reaction with tertiary amines is described by the base-catalyzed hydration of CO2.

CO2‐Alkanolamine Reaction Kinetics: A Review of Recent Studies

Converting carbon dioxide into carbamato derivatives.

The capture of CO2 from fossil fuel combustion, particularly in coal-fired power plants, represents a critical component of efforts aimed at stabilizing greenhouse gas levels in the atmosphere. Alkanolamines have traditionally been used to this end; however, drawbacks such as volatility, degradation, and regeneration costs have been drivers for the development of new, superior technologies. Recently, several seminal studies with ionic liquids (ILs), both experimental and computational, have demonstrated their potential as CO2 capture agents. In traditional ILs, experimental studies with CO2 have revealed its unusually high physical solubility in these media. Complementary simulation studies have provided evidence that this is attributable to CO2 occupying void space within the liquid and favorably interacting with the anion. Recently, a series of second-generation task-specific ionic liquids (TSILs) containing amine functional groups have been synthesized and demonstrated to have much higher capacities fo...

Amine-functionalized task-specific ionic liquids: a mechanistic explanation for the dramatic increase in viscosity upon complexation with CO2 from molecular simulation.

Rate constants, ΔH‡ and ΔS‡ have been measured by the conductimetric stopped-flow technique for the reaction of carbon dioxide in aqueous solution with the primary amines 2-methoxyethylamine, 2-aminoethanol, 3-aminopropan-1-ol, 2-aminopropan-2-ol, DL-aminopropan-2-ol and the secondary amines 1,1′-iminodipropan-2-ol, 2-amino-2-(hydroxymethyl) propane-1,3-diol, 2,2′-iminodiethanol, 2,2,6,6-tetramethylpiperidin-4-ol, and morpholine. The observed first-order rate constants fit the equation kobs=kAM[R2NH]2+kW[R2NH][H2O]. The much-quoted Danckwerts mechanism is shown to be unlikely.

Kinetics and mechanism of the reaction between carbon dioxide and amines in aqueous solution

The rate of formation of N,N-dialkylcarbamate from diethanolamine and carbon dioxide in anhydrous ethanol has been found to depend on the square of the amine concentration. The rate and activation data are consistent with the two-step Danchwerts mechanism, in which a zwitterion intermediate is present at very low concentration and reacts with a second molecule of amine at the diffusion-controlled limit to give a final salt in the rate-determining step.

J. Paul Donnellan

Papers

Kinetics and mechanism of the reaction between carbon dioxide and amines in aqueous solution

Kinetics of the formation of N,N-dialkylcarbamate from diethanolamine and carbon dioxide in anhydrous ethanol