Ether-functionalization of monoethanolamine (MEA) for reversible CO₂ capture under solvent-free conditions with high-capacity and low-viscosity

Abstract

CO2 absorption and desorption performance of novel ether-functionalized MEAs under solvent-free condition and their thermodynamic features as well as structure–property relationships are reported.

Review of carbon capture absorbents for CO2utilization

“…65,107,[120][121][122][123] To resolve these limitations, researchers have ventured into synthesizing novel absorbents via hybrid mixing and incorporating promoters or enhancers into CO 2 capture systems. 32,38,65,66,83,118,[124][125][126] The purpose of these initiatives is to combine the advantages of the different absorbents to enhance their CO 2 capture performance and overcome their limitations. 89,127 As numerous hybrid absorbents are being proposed over the years, this subsection only highlights some of the recent development of different hybrid absorbents.…”

“…These include toxicity of amine absorbents group and ILs, low CO 2 capture absorption rate for MDEA, limited application data of carbonate absorbents in CO 2 capture, limited direct utilization option of hydroxide absorbents and CaCO 3, and uncertainty on the post‐absorption product by amino acid salts 65,107,120–123 . To resolve these limitations, researchers have ventured into synthesizing novel absorbents via hybrid mixing and incorporating promoters or enhancers into CO 2 capture systems 32,38,65,66,83,118,124–126 . The purpose of these initiatives is to combine the advantages of the different absorbents to enhance their CO 2 capture performance and overcome their limitations 89,127 .…”

Alkoxy-Functionalized Amines as Single-Component Water-Lean CO2 Absorbents with High Efficiency: The Benefit of Stabilized Carbamic Acid

“…In our continuous efforts to develop new concepts as well as efficient strategies for CO 2 capture and further transformation, − we envision that the viscosity of several traditional aliphatic amines at the CO 2 -saturated state could be significantly reduced though careful alkoxy functionalization. , The alkoxy arm embedded within the amine structure could create more free volume through its high conformational flexibility, thereby greatly enhance the flowability, and would ultimately intensify the interior mass transfer behavior to increase CO 2 capacity and thermoreversibility. , Ether-functionalized ionic liquids has also been separately studied for CO 2 /SO 2 capture through chemi- and/or physisorption. − Meanwhile, carbamic acid is considered to be a feasible form of sequestrated CO 2 in the amine scrubbing process due to the full utilization of the nitrogen moiety (1:1 stoichiometry between CO 2 and nitrogen) and its relatively easy reversal compared with that of ammonium carbamate. ,, Furthermore, intramolecular hydrogen bonding is preferable if carbamic acid as an uncharged species dominates within the chemisorption system after CO 2 uptake, thus leading to lower operating viscosity than in the intermolecular hydrogen bonding scenarios . Notably, the alkoxy chain has been proved by recent reports to be a viable hydrogen bond acceptor that could bind the acidic proton to form multiple complexation. , We then propose a simple structural modification method for aliphatic primary amines that involves fixation of an appropriate alkoxy substituent to such a cheap and versatile industrial commodity, aiming to acquire reduced operating viscosity that enables smooth processing at the water-lean status under industrially relevant conditions and, in the meantime, increase capture capacity via stabilization of the in situ formed carbamic acid through intramolecular hydrogen bonding.…”

“…In our continuous efforts to develop new concepts as well as efficient strategies for CO 2 capture and further transformation, 45−47 we envision that the viscosity of several traditional aliphatic amines at the CO 2 -saturated state could be significantly reduced though careful alkoxy functionalization. 48,49 The alkoxy arm embedded within the amine structure could create more free volume through its high conformational flexibility, thereby greatly enhance the flowability, and would ultimately intensify the interior mass transfer behavior to increase CO 2 capacity and thermoreversibility. 50,51 Etherfunctionalized ionic liquids has also been separately studied for CO 2 /SO 2 capture through chemi-and/or physisorption.…”

“…Herein, we would like to disclose a series of alkoxyfunctionalized methylamines that are not only economical with low-cost precursors as well as convenient and scalable synthesis but also able to reversibly capture CO 2 with enhanced capacity and mild operating viscosity in a single-component manner (Scheme 1). Although both aliphatic amines and ionic liquids modified with an ether attachment have been reported by us 48,49 and others 52−56 to achieve better flowability after CO 2 incorporation, this work constitute the first example of performance enhancement via the formation of carbamic acid species promoted by the introduction of an appropriate alkoxy functionality under the water-lean condition. The stabilization mechanism for in situ formed carbamic acid along with capture release thermodynamics of these newly devised absorbents were systematically interpreted using density functional theory (DFT) calculations, in situ Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) measurements, vapor−liquid equilibrium (VLE) measurements, and designed control experiments, and their potential as competent candidates for industrial application was fully unveiled.…”