Mechanism Of CO2 Absorption Research Articles

Determining whether hydrological processes drive carbon source and sink conversion shifts in a large floodplain-lake system in China

Lake carbon (C) cycling is a key component of the global C cycle and associated C source and sink processes. The partial pressure of carbon dioxide (pCO2) and carbon dioxide (CO2) exchange flux at the lake-air interface (Fc) are controlled by complex physical, chemical, and biological mechanisms. It would be instructively significant to determine whether hydrological processes drive conversion shifts between C sources and sinks in floodplain-lake systems. Findings from this study show that exogenous input and in situ metabolism related to photosynthesis, respiration, and organic matter degradation were the main driving mechanisms of CO2 absorption and release in a large floodplain-lake system (i.e., Lake Poyang). Moreover, the intense and frequent water-level fluctuations inherent to floodplain-lakes may also have a direct or indirect impact on C cycling processes and CO2 exchange rates in floodplain-lake systems via their effect on physical processes, inorganic C transport, in-situ metabolic processes. We confirmed the potential of C source and sink conversion in floodplain-lakes under hydrological fluctuations, and strengthen the understanding of driving mechanisms of C source and sink conversion in floodplain systems.

Performance and mechanism of CO2 absorption during the simultaneous removal of SO2 and NOx by wet scrubbing process

The co-removal of CO2 while removing SO2 and NOx from industrial flue gas has great potential of carbon emission reduction but related research is lacking. In this study, a wet scrubbing process with various urea solutions for desulfurization and denitrification was explored for the possibility of CO2 absorption. The results showed that the urea-additive solutions were efficient for NOx and SO2 abatement, but delivered < 10% CO2 absorption efficiency. The addition of Ca(OH)2 dramatically enhanced the CO2 absorption, remained the desulfurization efficiency, unfortunately restricted the denitrification efficiency. Among various operating parameters, pH of solution played a determining role during the absorption. The contradictory pH demands of CO2 absorption and denitrification were observed and discussed in detail. A higher pH of solution than 10 was favorable for CO2 absorption, while the oxidizing of NO to NO2, NO2− or NO3− by NaClO2 was inhibited in this condition. When 7 < pH < 10, it was favorable for the conversion and absorption of NO and NOx. However, the conversion of HCO3− to CO32− was significantly inhibited, hence preventing the absorption of CO2. Large part of Ca(OH)2 became CaCO3 with a finer particle size, which covered the unreacted Ca(OH)2 surface after the reaction. Kinetic analysis showed that the CO2 absorption in urea-NaClO2-Ca(OH)2 absorbent was controlled by chemical reaction in early stage, then by ash layer diffusion in later stage.

Study of Absorbing CO2 from Emissions Using a Spray Tower

In order to reduce the environmental impact caused by CO2 emissions from ships and achieve the goal of green shipping, a spray tower using NaOH solution for the absorption of CO2 has been established in this paper. Using the characteristics of a 6135G128ZCa marine diesel engine, the CO2 absorption system was designed and mathematical models of CO2 absorption efficiency were developed. The effects of the variation in engine exhaust gas temperature, the concentration of NaOH solution, the exhaust gas velocity, different load conditions, and different nozzle types on the absorption efficiency of CO2 were thoroughly investigated experimentally. Moreover, the mechanism of CO2 absorption was analyzed. The developed model was verified by comparing the test results with the simulation results. The results of the study proved that using NaOH solution to absorb CO2 from ship exhausts could reduce the level of CO2 emissions from ships by more than 20%, which indicates that this technology could be used in the future to reduce the level of CO2 emissions from ships.

Unraveling the Role of Glycine in K2CO3 Solvent for CO2 Removal

Carbon dioxide (CO2), a main composition of greenhouse gases, is believed to be responsible for global warming. Both potassium carbonate (K2CO3) and amino acids have been studied for CO2 removal. In this study, for the first time, carbamate formation in the absence of CO2 was discovered in K2CO3 solvents when small amounts of amino acids like glycine were added, and the mechanism of carbamate formation and CO2 absorption in such solvents are detailed and supported the observed fast CO2 absorption in the presence of amino acids. In the mixed solvent of K2CO3 and glycine, bicarbonate and hydroxide were formed from carbonate hydrolysis, and the deprotonated amino acid reacted with bicarbonate to form carbamate in the absence of CO2 and, in the presence of CO2, reacted with CO2 to form carbamate which could subsequently hydrolyze into bicarbonate. As a result, amino acid (even with a small amount) significantly enhanced the CO2 absorption kinetics in the mixed solvents, and a high CO2 loading (0.62 mol CO2/mol K2CO3) was achieved in multiple (e.g., 10) cycles. Such mixed solvents of K2CO3 and amino acid therefore may overcome the limitations of each individual component and may be ideal candidates for CO2 removal.

Mechanism study on CO2 capture by ionic liquids made from TFA blended with MEA and MDEA

Ionic liquids are presenting a great potential to increase the efficiency and reduce the cost of CO2 capture process. TFA was selected as anion in the produced ionic liquids to study its absorption capacity, and CO2 capture by [3-AP][TFA] and [MDEA][TFA] were tested under different conditions with various solvents such as water, MEA and MDEA. Results showed that ionic liquids blended with MEA improved the absorption capacity up to 0.50 mol CO2/mol absorbent, which was much higher than that of aqueous ionic liquid solution (less than 0.30 mol CO2/mol absorbent), and the aqueous solution of ionic liquids blended with MDEA could improve its absorption capacity up to 0.93 mol CO2/mol absorbent. Different ratios of ionic liquids blended with MDEA were investigated, and ratios of ionic liquids versus MDEA was set from 2:1 to 1:6. The CO2 absorption capacity reached the maximum of 0.91 mol CO2/mol IL at ratio 1:6 for [3-AP][TFA] and 0.93 mol CO2/mol IL at ratio 1:4 for [MDEA][TFA], which indicated that the CO2 absorption capacity increased with ascending amount of MDEA. Characterizations of aqueous blends were performed by FT-IR and 13C NMR, which showed that the formation of bicarbonate was observed, indicating the mechanism of CO2 absorption was a two-step reaction via the formation of zwitterion. The produced zwitterions contributed to CO2 absorption by increasing both the capacity and reaction rate. Reaction of MDEA with CO2 in water was considered to be a catalyzed hydrolysis, because the lack of eliminating hydrogen atom prevented MDEA from forming carbamate but produced bicarbonate instead.

An experimental/computational study of steric hindrance effects on CO2 absorption in (non)aqueous amine solutions

AbstractThe reaction kinetics and molecular mechanisms of CO2 absorption using nonaqueous and aqueous monoethanolamine (MEA)/methyldiethanolamine (MDEA)/2‐amino‐2‐methy‐1‐propanol (AMP) solutions were analyzed by the stopped‐flow technique and ab initio molecular dynamics (AIMD) simulations. Pseudo first‐order rate constants (k0) of reactions between CO2 and amines were measured. A kinetic model was proposed to correlate the k0 to the amine concentration, and was proved to perform well for predicting the relationship between k0 and the amine concentration. The experimental results showed that AMP/MDEA only took part in the deprotonation of MEA‐zwitterion in nonaqueous MEA + AMP/MEA + MDEA solutions. In aqueous solutions, AMP can also react with CO2 through base‐catalyzed hydration mechanism beside the zwitterion mechanism. Molecular mechanisms of CO2 absorption were also explored by AIMD simulations coupled with metadynamics sampling. The predicted free‐energy barriers of key elementary reactions verified the kinetic model and demonstrated the different molecular mechanisms for the reaction between CO2 and AMP.

CO2 Absorption Mechanism by the Deep Eutectic Solvents Formed by Monoethanolamine-Based Protic Ionic Liquid and Ethylene Glycol.

Deep eutectic solvents (DESs) have been widely used to capture CO2 in recent years. Understanding CO2 mechanisms by DESs is crucial to the design of efficient DESs for carbon capture. In this work, we studied the CO2 absorption mechanism by DESs based on ethylene glycol (EG) and protic ionic liquid ([MEAH][Im]), formed by monoethanolamine (MEA) with imidazole (Im). The interactions between CO2 and DESs [MEAH][Im]-EG (1:3) are investigated thoroughly by applying 1H and 13 C nuclear magnetic resonance (NMR), 2-D NMR, and Fourier-transform infrared (FTIR) techniques. Surprisingly, the results indicate that CO2 not only binds to the amine group of MEA but also reacts with the deprotonated EG, yielding carbamate and carbonate species, respectively. The reaction mechanism between CO2 and DESs is proposed, which includes two pathways. One pathway is the deprotonation of the [MEAH]+ cation by the [Im]− anion, resulting in the formation of neutral molecule MEA, which then reacts with CO2 to form a carbamate species. In the other pathway, EG is deprotonated by the [Im]−, and then the deprotonated EG, HO-CH2-CH2-O−, binds with CO2 to form a carbonate species. The absorption mechanism found by this work is different from those of other DESs formed by protic ionic liquids and EG, and we believe the new insights into the interactions between CO2 and DESs will be beneficial to the design and applications of DESs for carbon capture in the future.

Innovative cycling reaction mechanisms of CO2 absorption in amino acid salt solvents

Amino acid salt (AAS) solvents with equimolar base (used to obtain the salt) to amino acid (AA) have been well studied for CO2 absorption, however, very little is known about the reactions when more base is applied. This study determined the reaction mechanisms of AAS solvents with base to AA ratio over equimolar and the potential benefits of such solvents for CO2 absorption. The CO2 loading capacity was found to be dictated by the molar concentration of the base and was approximately half of the base applied. The reaction mechanisms were investigated based on the compositions of carbamate, carbonate/bicarbonate, and AA using 13C-quantitative nuclear magnetic resonance (13C qNMR). An innovative cycling reaction mechanism of CO2 absorption was proposed and experimentally confirmed for AAS solvents with base/AA > 1. Besides all steps of the current widely accepted Zwitterion mechanism, this reaction pathway also contains two cycles: 1) The extra base (i.e., OH−) may react with the protonated AA generated during CO2 absorption to form deprotonated AA which further absorbs CO2 to form more carbamate. 2) The carbamate, as a product of reaction cycle 1, undergoes hydrolysis to yield bicarbonate and deprotonated AA, which further absorbs CO2. As a result, high CO2 loadings were achieved. Compared to the use of alkaline solutions like KOH alone for CO2 absorption, AAS solvents with base to AA ratio over equimolar resulted in lower pH and temperature while maintaining high CO2 loading. These innovative cyclic mechanisms will enable advanced CO2 management approaches using AAS solvents with base/AA > 1.

Molecular Simulation and Experimental Study on Low-Viscosity Ionic Liquids for High-Efficient Capturing of CO2

In recent decades, ionic liquids (ILs) have been developed as an ideal and reversible decarbonization solvent. However, some pitfalls, such as the low CO2 capacity and high viscosity of ILs, limit their further scale up and industrial application. Therefore, in this work, three novel functional ILs [N8881][NIA], [N8881][For], and [N8881][Ac] were synthesized after using a molecular design method to capture CO2 at 303.15–333.15 K and pressures up to 1000 kPa. The experimental results illustrate that [N8881][NIA] presents the smallest viscosity and the highest CO2 solubility. The capacity order is [N8881][NIA] > [N8881][For] > [N8881][Ac] under the same experimental conditions. The CO2 recyclability experiments using [N8881][NIA] show the stability of CO2 solubility after 5 cycles. The quantum chemistry simulations at the level of DFT/B3LYP with 6-311++G(d,p) basis sets were used to study the CO2 absorption mechanism in the studied ILs from the molecular viewpoint. Simulation results illustrated that the higher interaction energy between CO2 and ILs means more CO2 absorbed in these ILs, which agreed well with the experimental results. The atoms in molecules theory and the function of the reduced density gradient were also used to calculate the interactions in these IL–CO2 systems. Results show that the majority of these interactions present an electrostatic character.

Enhancing Absorption Performance of CO2 by Amine Solution through the Spiral Wired Channel in Concentric Circular Membrane Contactors.

The CO2 absorption rate by using a Monoethanolamide (MEA) solution through the spiral wired channel in concentric circular membrane contactors under both concurrent-flow and countercurrent-flow operations was investigated experimentally and theoretically. The one-dimensional mathematical modeling equation developed for predicting the absorption rate and concentration distributions was solved numerically using the fourth Runge–Kutta method under various absorbent flow rate, CO2 feed flow rate and inlet CO2 concentration in the gas feed. An economical viewpoint of the spiral wired module was examined by assessing both absorption flux improvement and power consumption increment. Meanwhile, the correlated average Sherwood number to predict the mass-transfer coefficient of the CO2 absorption mechanisms in a concentric circular membrane contactor with the spiral wired annulus channel is also obtained in a generalized and simplified expression. The theoretical predictions of absorption flux improvement were validated by experimental results in good agreements. The amine solution flowing through the annulus of a concentric circular tube, which was inserted in a tight-fitting spiral wire in a small annular spacing, could enhance the CO2 absorption flux improvement due to reduction of the concentration polarization effect. A larger concentration polarization coefficient (CPC) was achieved in the countercurrent-flow operations than that in concurrent-flow operations for various operations conditions and spiral-wire pitches. The absorption flux improvement for inserting spiral wire in the concentric circular module could provide the maximum relative increment up to 46.45%.

The Influence of Hydrogen Bond Donors on the CO2 Absorption Mechanism by the Bio-Phenol-Based Deep Eutectic Solvents.

Recently, deep eutectic solvents (DESs), a new type of solvent, have been studied widely for CO2 capture. In this work, the anion-functionalized deep eutectic solvents composed of phenol-based ionic liquids (ILs) and hydrogen bond donors (HBDs) ethylene glycol (EG) or 4-methylimidazole (4CH3-Im) were synthesized for CO2 capture. The phenol-based ILs used in this study were prepared from bio-derived phenols carvacrol (Car) and thymol (Thy). The CO2 absorption capacities of the DESs were determined. The absorption mechanisms by the DESs were also studied using nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and mass spectroscopy. Interestingly, the results indicated that CO2 reacted with both the phenolic anions and EG, generating the phenol-based carbonates and the EG-based carbonates, when CO2 interacted with the DESs formed by the ILs and EG. However, CO2 only reacted with the phenolic anions when the DESs formed by the ILs and 4CH3-Im. The results indicated that the HBDs impacted greatly on the CO2 absorption mechanism, suggesting the mechanism can be tuned by changing the HBDs, and the different reaction pathways may be due to the steric hinderance differences of the functional groups of the HBDs.

Tuning the CO2 absorption and physicochemical properties of K+ chelated dual functional ionic liquids by changing the structure of primary alkanolamine ligands

To reveal the effects of the alkyl substitutions at alpha (α) or beta (β) position adjacent to amino group of primary alkanolamine ligands on CO2 absorption and physicochemical properties of metal chelated dual functional ionic liquids (DFILs), four DFILs were prepared by reacting potassium imidazole salt (KIm) with alkanolamine ligands, including 2-amino-2-methyl-1-propanol (AMP), 2-amino-1-butanol (AMB), DL-1-amino-2-propanol (DLAMP), and monoethanolamine (MEA). CO2 absorption behavior and mechanism of DFILs were studied, and density (ρ), speed of sound (u), and viscosity (η) of DFILs were measured to correlate with the CO2 absorption performance. DFT calculations were employed to explore the influence of the interactions between K+ and alkanolamine on the CO2 absorption and physicochemical properties of DFILs. The results show that CO2 capacity at 333.2 K is as follows: [K(AMP)2][Im] > [K(AMB)2][Im] > [K(DLAMP)2][Im] > [K(MEA)2][Im], indicating that the introduction of alkyl group at α or β position of alkanolamines can enhance CO2 capacity, and the effect of the α position is more significant than the β position. Both ρ and u follow the order: [K(AMP)2][Im] < [K(AMB)2][Im] < [K(DLAMP)2][Im] < [K(MEA)2][Im], while η is in the reverse order. Moreover, the saturated CO2 capacity of DFILs has an approximately linear relation with the thermal expansion coefficient. DFT calculations show that the presence of the alkyl group at α or β position of alkanolamines reduces the Mulliken charge of N and O atom, thereby weakening the cation coordination interaction between K+ with ligand, resulting in the decrease in ρ and u of DFILs. Moreover, the decrease in the Mulliken charge of N and O atom in alkanolamine leads to the increase of chelated cation-[Im]− interaction, thereby increasing η of DFILs. Consequently, [K(AMP)2][Im] exhibits higher CO2 capacity and good reversibility, due to the fact that CO2 can react with the chelated cation and [Im]– simultaneously. The present study provides a new method for effectively regulating the performance of DFILs.

Synthesis and properties of symmetric glycerol-derived 1,2,3-triethers and 1,3-diether-2-ketones for CO2 absorption

Five compounds bearing glycerol skeletons: 1,3-diethoxypropan-2-one ([E, K, E]), 2,5,9,12-tetraoxatridecan-7-one ([ME, K, ME]), 1,3-bis(2,2,2-trifluoroethoxy)propan-2-one ([F, K, F]), 7-(2-methoxyethoxy)-2,5,9,12-tetraoxatridecane ([ME, ME, ME]) and 2-(2-methoxyethoxy)-1,3-bis(2,2,2-trifluoroethoxy)propane ([F, ME, F]) – were synthesized from epichlorohydrin at molar scales with high regioselectivity. Density and viscosity were measured over a temperature range of 293.15 to 353.15 K. Henry’s constants for CO2 were obtained under moderate pressures (2 to 10 atm) at 303.15, 318.15, 333.15 and 348.15 K. Comparison of CO2 affinity with dimethyl ethers of polyethylene glycol (DMPEG) and ionic liquids (ILs) indicated that [ME, ME, ME] and [F, ME, F] are excellent candidates as novel physical solvents for CO2 capture. DFT calculations were performed to understand the structure–property-performance relationships for the CO2 absorption mechanism. All five compounds were miscible with most common solvents except hexanes and water. In addition to gas absorption applications, these compounds might also find use as general purpose green solvents.

CO2 absorption mechanism in aqueous ternary solutions of alkanolamines: Experimental and thermodynamic modeling approaches

The absorption mechanism of CO2 in an aqueous solution containing three alkanolamines was analyzed experimentally and theoretically. The vapor–liquid equilibrium of a CO2–monoethanolamine (MEA)–diisopropanolamine (DIPA)–2-amino-2-methyl-propanol (AMP)–H2O system was evaluated experimentally over a wide temperature range (323.15–393.15 K) at several MEA:DIPA:AMP:H2O blending ratios (15:10:5:70, 10:10:10:70, 7.5:7.5:15:70, and 5:15:10:70 wt%). The successive substitution method was used to calculate the concentrations of five molecules (CO2, MEA, DIPA, AMP, and H2O) and nine electrolytes (four cations and five anions) in the liquid phase by solving eight equilibrium equations, four mass balance equations, and one charge balance equation. The Deshmukh–Mather model, which is based on an activity coefficient approach, and the fugacity coefficient model were used to evaluate the nonideality of the liquid and vapor phases, respectively. Thereafter, the effect of the MEA:DIPA:AMP blending ratio was evaluated using the triangular diagrams of the carbamate, bicarbonate and carbonate molar fractions in liquid phase, CO2 loading ratio, CO2 cyclic capacity, and heat of CO2 absorption.

CO2 Capture at Medium to High Temperature Using Solid Oxide-Based Sorbents: Fundamental Aspects, Mechanistic Insights, and Recent Advances.

Carbon dioxide capture and mitigation form a key part of the technological response to combat climate change and reduce CO2 emissions. Solid materials capable of reversibly absorbing CO2 have been the focus of intense research for the past two decades, with promising stability and low energy costs to implement and operate compared to the more widely used liquid amines. In this review, we explore the fundamental aspects underpinning solid CO2 sorbents based on alkali and alkaline earth metal oxides operating at medium to high temperature: how their structure, chemical composition, and morphology impact their performance and long-term use. Various optimization strategies are outlined to improve upon the most promising materials, and we combine recent advances across disparate scientific disciplines, including materials discovery, synthesis, and in situ characterization, to present a coherent understanding of the mechanisms of CO2 absorption both at surfaces and within solid materials.

CO2 Absorption Mechanism by Diamino Protic Ionic Liquids (DPILs) Containing Azolide Anions

Protic ionic liquids have been regarded as promising materials to capture CO2, because they can be easily synthesized with an attractive capacity. In this work, we studied the CO2 absorption mechanism by protic ionic liquids (ILs) composed of diamino protic cations and azolide anions. Results of 1H nuclear magnetic resonance (NMR), 13C NMR, 2-D NMR and fourier-transform infrared (FTIR) spectroscopy tests indicated that CO2 reacted with the cations rather than with the anions. The possible reaction pathway between CO2 and azolide-based protic ILs is proposed, in which CO2 reacts with the primary amine group generated from the deprotonation of the cation by the azolide anion.

DFT Study on the Chemical Absorption Mechanism of CO2 in Diamino Protic Ionic Liquids.

Diamino protic ionic liquids (DPILs) possess a wide application prospect in the field of acid gas absorption. In this work, two representative DPILs, that is, dimethylethylenediamine 4-fluorophenolate ([DMEDAH][4-F-PhO]) and dimethylethylenediamine acetate ([DMEDAH][OAc]), which had been proved to display favorable CO2 absorption performance in experiments, were selected. Based on the solvation model, the different mechanisms of CO2 absorption by [DMEDAH]+ cations combined with different anions were investigated using the dispersion-corrected density functional theory method. Above all, the possible active sites of the reaction between DPILs and CO2 were analyzed by electrostatic potential (ESP) and electronegativity, and the transition states in each path were searched and verified by frequency calculation and intrinsic reaction coordinate calculation. Furthermore, the Gibbs free energy and reaction heat of each path were calculated, and the free energy barrier and enthalpy barrier diagrams were shown. It was found that the absorption path by the anion of [DMEDAH][4-F-PhO] was favorable in kinetics, while the absorption path by the cation was thermodynamically beneficial. In addition, [DMEDAH][OAc] only showed the possibility of cation absorption, and the mechanism of the transfer of active protons to weak acid anions and the formation of acetic acid molecules was more favorable. Moreover, through the structural analysis, bond order and bond energy calculation, ESP analysis of the ion pair absorption configuration, and comparison with the products of CO2 absorbed by isolated ions, it was found that the interaction between anions/cations and CO2 could weaken or enhance the interaction between anions and cations in different reaction steps. Hopefully, this study is helpful to understand the absorption mechanism of CO2 by DPILs and provides a theoretical basis for the R&D of multi-active site functionalized ILs.

Carbon dioxide capture using water-imidazolium ionic liquids-amines ternary systems

Ionic liquids (ILs) mixtures with water, amines, and other solvents have been receiving attention as alternative CO2 absorbents that could offer energy savings compared with traditional aqueous MEA processes and mitigate the high cost or viscosity of pure ionic liquids. In this work, mixtures of two ionic liquids (1-butyl-3-methylimidazolium acetate [bmim][OAc], 1-ethyl-3-methylimidazolium octylsulphate [emim][OcSO4]) and five amines (1,1,3,3-tetramethylguanidine (TMG), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO), triethylamine (TEA), and 2,2′-aminodiethanol (DEA)) were used for CO2 capture. In total, ten model systems were investigated. Generalized patterns of composition-CO2 absorption relationships were identified depending on the underlying mechanism of absorption. Viscosity, degradation and regeneration potential of the selected systems were determined. DBU-[emim][OcSO4] systems showed the temperature of regeneration as low as 60 °C. The viscosity of all systems was greatly reduced by the addition of water. Some CO2-rich solutions displayed non‐Newtonian behavior. Mechanism of CO2 absorption in imidazolium ionic liquids in the presence of DBU was confirmed based on 13C NMR.

CO2 Absorption Mechanism by the Nonaqueous Solvent Consisting of Hindered Amine 2-[(1,1-dimethylethyl)amino]ethanol and Ethylene Glycol.

In this work, we studied the CO2 absorption mechanism by nonaqueous solvent comprising hindered amine 2-[(1,1-dimethylethyl)amino]ethanol (TBAE) and ethylene glycol (EG). The NMR and FTIR results indicated that CO2 reacted with an -OH group of EG rather than the -OH of TBAE by producing hydroxyethyl carbonate species. A possible reaction pathway was suggested, which involves two steps. In the first step, the acid–base reaction between TBAE and EG generated the anion HO-CH2-CH2-O-; in the second step, the O− of HO-CH2-CH2-O− attacked the C atom of CO2, forming carbonate species.

Effect of non-aqueous solvents on kinetics of carbon dioxide absorption by tBu3P/B(C6F5)3 frustrated Lewis pairs

Frustrated Lewis pairs (FLPs), combinations of sterically hindered Lewis acids and bases, are known for their ability to capture CO2. Although there have been several theoretical studies on the mechanisms of the reactions between CO2 and some FLP systems, experimental studies on the reaction kinetics have been inconclusive. In this study, the mechanism and kinetics of CO2 absorption by an FLP system consisting of tri-tert-butylphosphine (tBu3P) and tris(pentafluorophenyl)borane (B(C6F5)3) in bromobenzene, cyclopentyl methyl ether (CPME), and tert-butyl methyl ether (MTBE) were investigated using the stopped-flow method. The pseudo-first-order reaction rate constants, ko (s−1), were measured for a concentration range of 0.02–0.035 M and over a temperature range of 298–323 K. The experimental data were fitted according to modified termolecular mechanisms with average absolute relative deviations of 4.34%, 4.63%, and 3.51% for the CO2–FLP:bromobenzene, CO2–FLP:CPME, and CO2–FLP:MTBE systems, respectively. The forward reaction rate constants, k (m3 kmol−1 s−1), were calculated based on the proposed reaction mechanism. The forward reaction rate constants were higher than those for various aqueous tertiary amine systems but lower than those for aqueous monoethanolamine and piperazine systems. Moreover, the activation energies were estimated from Arrhenius plots. They were calculated to be 22.0, 19.7, and 21.8 kJ mol−1 for the CO2–FLP:bromobenzene, CO2–FLP:CPME, and CO2–FLP:MTBE systems, respectively. This study promotes the development of novel efficient solvent formulations for CO2 capture.