Pathways of the Chemical Reaction of Carbon Dioxide with Ionic Liquids and Amines in Ionic Liquid Solution

Kortunov, Pavel; Baugh, Lisa Saunders; Siskin, Michael

doi:10.1021/acs.energyfuels.5b00876

Cited by 25 publications

(20 citation statements)

References 68 publications

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“…has been reported previously by Besnard et al (2012) and Kortunov et al (2015), who showed that the signal at 141.5 ppm corresponds to the carboxylated C3 position in EMIM ? .…”

Section: Chemical Structures Of Dissolved and Regenerated Cellulosesupporting

confidence: 68%

“…These findings indicate that a possible reaction takes place between the cellulose-sorbed CO 2 and the EMIM?, yielding a carboxylated EMIM ? with characteristic NMR signals (Besnard et al 2012;Kortunov et al 2015) coincident with the signals observed at 154.3 and 141.5 ppm. It is, however, important to bear in mind that the carbonate band seen in the ATR-IR spectroscopy in which no EMIMAc was present shows that the signal at 154.3 ppm does not originate from the EMIMAc but is introduced during the dissolution of cellulose in NaOH(aq).…”

Section: Chemical Structures Of Dissolved and Regenerated Cellulosesupporting

confidence: 62%

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Chemisorption of air CO2 on cellulose: an overlooked feature of the cellulose/NaOH(aq) dissolution system

2017

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A natural abundance of the air CO 2 in NaOH(aq) at low temperature was investigated in terms of cellulose-CO 2 interactions upon cellulose dissolution in this system. An organic superbase, namely 1,8-diazabicyclo[5.4.0]undec-7-ene, DBU, known for its ability to incorporate CO 2 in carbohydrates, was employed in order to shed light on this previously overlooked feature of NaOH(aq) at low temperature. The chemisorption of CO 2 onto cellulose was investigated using spectroscopic methods in combination with suitable regeneration procedures. ATR-IR and NMR characterisation of regenerated celluloses showed that chemisorption of CO 2 onto cellulose during its dissolution in NaOH(aq) takes place both with and without employment of the CO 2 -capturing superbase. The chemisorption was also observed to be reversible upon addition of water: CO 2 desorbed when water was used as regenerating agent but could be preserved when instead ethanol was used. This finding could be an important parameter to take into consideration when developing processes for dissolution of cellulose based on this system.

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“…has been reported previously by Besnard et al (2012) and Kortunov et al (2015), who showed that the signal at 141.5 ppm corresponds to the carboxylated C3 position in EMIM ? .…”

Section: Chemical Structures Of Dissolved and Regenerated Cellulosesupporting

confidence: 68%

Section: Chemical Structures Of Dissolved and Regenerated Cellulosesupporting

confidence: 62%

Chemisorption of air CO2 on cellulose: an overlooked feature of the cellulose/NaOH(aq) dissolution system

2017

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“…The formation of the ylide complex by the deprotonation step is the crucial factor for the chemisorption of CO 2 by the cation. In previous 44 work, the authors did not report the transition states of the chemisorption reaction of CO 2 by ylide complex as well as an anion. However, we found the transition states for both the pathways and the formation of the ylide complex are the most energetic processes.…”

Section: Resultsmentioning

confidence: 99%

Reaction Mechanism and Free Energy Barriers for the Chemisorption of CO₂ by Ionic Entities

Gorantla

Mallik

2020

J. Phys. Chem. A

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Ionic liquids, a class of alternative solvents, are known for their ability to capture carbon dioxide (CO 2 ). The understanding of the role of the individual ionic entity of the ionic liquid (IL) and the involved mechanism is essential to design a better solvent for the capture process. In the present study, we employed density functional theory based electronic structure calculations and metadynamics method based first-principles molecular dynamics (FPMD) simulations to investigate the roles of the cation and anion of the IL by analyzing the energetics and free energy profile of the involved chemical reactions. The mechanism of chemisorption of CO 2 by the aprotic N-heterocyclic and phenolate anions paired with tetrapropyl phosphonium cation [P 3333 ] were studied to understand the reaction mechanism of the initial capture process. The process of uptaking of CO 2 by the [P 3333 ][1,2,4-Triz] was studied by the first-principles calculations. The transition states in the reaction pathways were computed by the synchronous transit-guided quasi-Newton method and confirmed by the intrinsic reaction coordinate calculations using first-principles simulations. The dynamics of the energetics of the chemisorption process were studied by constructing the free energy surface using metadynamics-based FPMD simulations. First, the nucleophilic center was generated at the α-carbon of the cation by transferring a proton to the anion with the formation of the phosphorus ylide. The formed cation ylide chemisorbs CO 2 through the formation of a bond between the α-carbon of ylide and the carbon of CO 2 . The direct addition of CO 2 to the anion of the ionic pair was studied as the second pathway. We find that the chemisorption of CO 2 by the anion is more favorable than that by the cation. By comparing the chemisorption of CO 2 by the ions, we observe that the deprotonation of the alkyl chain is the more deciding factor, which depends on the basicity of anion and the length of the alkyl chain. We computed the free energy landscapes for the ionic pairs by varying another four anions like cyclohexanolate, 2,4,6trifluorophenolate, imidazolate, and benzotriazolide paired with tetrapropyl phosphonium cation. The effect of the alkyl chain on the proton transfer was studied by tetrabutyl and tetrapentyl phosphonium cations paired with 1,2,4-triazolide anion. The carbonated product, formed from the anion, is thermodynamically controlled, while the carboxylated product (formed from cation) is kinetically controlled. We hope that our findings will enhance the knowledge of the selectivity of ionic entities for designing IL-based solvents for the capture process of CO 2 .

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“…consequence of these different reaction pathways, and the motivation for the amine work described in this and related publications, 1,49,50 is that theoretical CO 2 sorption capacity for an amine system is a function of the products that are formed. When ammonium carbamates are the preferred reaction product under non-aqueous conditions, the theoretical CO 2 sorption capacity is only 50 mol% per amine (2:1 amine:CO 2 ratio).…”

Section: Reaction Chemistry Of Amine/co 2 Sorptionmentioning

confidence: 99%

In Situ Nuclear Magnetic Resonance Mechanistic Studies of Carbon Dioxide Reactions with Liquid Amines in Non-aqueous Systems: Evidence for the Formation of Carbamic Acids and Zwitterionic Species

et al. 2015

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In a previous study, we reported the use of in situ 1 H-and 13 C-NMR to elucidate mechanistic pathways for the reaction of carbon dioxide with a broad range of amines (pKa ~4.5-15.5), including alkanolamines of commercial interest, in water. In the aqueous systems of that study, water most importantly functions as a Brønsted acid/Lewis base and as the amine is consumed and pH decreases hydrolyzes the initially formed carbamate species (1:2 CO 2 :amine stoichiometry), into the alkyl ammonium bicarbonate with a more beneficial 1:1 CO 2 :amine stoichiometry. This study has been extended herein to amines, amidines and guanidines dissolved in non-aqueous solvent systems such as dimethylsulfoxide, sulfolane, toluene, 1-methyl-2-pyrrolidinone and the ionic liquid 1-ethyl-3-methyl-imidazolium acetate. The use of non-aqueous organic solvents shuts off some CO 2 reaction pathways available in aqueous solution. However, more importantly, it opens up new possibilities and reaction pathways for amine based carbon capture. Two important aqueous-system pathways are eliminated: the direct hydration of CO 2 with tertiary amines or guanidines to form bicarbonates, and the hydrolysis of carbamates at lower pH to form bicarbonates. In non-aqueous solution, the initial step for the reaction of primary and secondary amines with CO 2 is the same as in aqueous solution -nucleophilic attack by the amine nitrogen on CO 2 . However, additional mechanistic pathways are enabled in non-aqueous solvents, particularly the stabilization of carbamic acid(s) (rather than carbamates) products in certain organic solvents. The formation of carbamates requires no water and is favored by higher amine concentrations and basicities (higher amine pKa). In contrast, carbamic acid/zwitterion formation is favored by lower amine concentrations, higher CO 2 partial pressures, lower amine pKa, and selection of more polar organic solvents that promote hydrogen bonding. The new amine-CO 2 reaction pathways enabled here by the use of non-aqueous solvents introduce stabilizing interactions between the non-aqueous solvent and the amine-CO 2 reaction products, facilitating higher capacity and selectivity for carbon capture than in water solutions. The effects of temperature, amine basicity, solvent electronic structures, and concentration on amine-CO 2 reaction products (carbamic acid/zwitterion/carbamate and equilibria between neutral and ion-paired forms) are discussed in detail herein.

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Pathways of the Chemical Reaction of Carbon Dioxide with Ionic Liquids and Amines in Ionic Liquid Solution

Cited by 25 publications

References 68 publications

Chemisorption of air CO2 on cellulose: an overlooked feature of the cellulose/NaOH(aq) dissolution system

Chemisorption of air CO2 on cellulose: an overlooked feature of the cellulose/NaOH(aq) dissolution system

Reaction Mechanism and Free Energy Barriers for the Chemisorption of CO₂ by Ionic Entities

In Situ Nuclear Magnetic Resonance Mechanistic Studies of Carbon Dioxide Reactions with Liquid Amines in Non-aqueous Systems: Evidence for the Formation of Carbamic Acids and Zwitterionic Species

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Pathways of the Chemical Reaction of Carbon Dioxide with Ionic Liquids and Amines in Ionic Liquid Solution

Cited by 25 publications

References 68 publications

Chemisorption of air CO2 on cellulose: an overlooked feature of the cellulose/NaOH(aq) dissolution system

Chemisorption of air CO2 on cellulose: an overlooked feature of the cellulose/NaOH(aq) dissolution system

Reaction Mechanism and Free Energy Barriers for the Chemisorption of CO2 by Ionic Entities

In Situ Nuclear Magnetic Resonance Mechanistic Studies of Carbon Dioxide Reactions with Liquid Amines in Non-aqueous Systems: Evidence for the Formation of Carbamic Acids and Zwitterionic Species

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Reaction Mechanism and Free Energy Barriers for the Chemisorption of CO₂ by Ionic Entities