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Density functional theory and molecular dynamic simulations were used to understand the microscopic-level interactions of pectin-based thin films with moisture (H2O), carbon dioxide (CO2), and oxygen (O2). Galacturonic acid (GA), which forms ~65% of the smooth region of pectin polymer, was chosen for the current study. The electrostatic potential and Fukui function maps indicate that oxygen atoms of –OH groups of GA are the most reactive sites for electrophilic attack and hydrogen atoms on the carboxylic group (–COOH) are the reactive sites for nucleophilic attack. The GA molecule has shown strong interaction via hydrogen bonding with H2O (E= ~ 40 kJ/mol) followed by CO2 (E = ~ −13 kJ/mol). Nucleophilic O2 showed insignificant interaction with GA. Surface interaction, adsorption, and diffusion of sorbate molecules on the GA film followed the order of H2O &gt;CO2 &gt; O2. Molecular interaction studies provided atomistic insights into the weak moisture and high gas barrier properties of pectin films. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

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Chemical Engineering

(SoE) School of Engineering

Journal of Molecular Modeling

Molecular Simulations to Understand the Moisture, Carbon Dioxide, and Oxygen Barrier Properties of Pectin Films

Atomistic level understanding of the interactions of thiophene and iso-octane with various organic solvents such as N-methylpyrrolidone (NMP), sulfolane, furfural, diethyleneglycol (DEG), 2-aminoethanol (ETA), tetraethyleneglycol (TEG), dimethylformamide (DMF) and cyrene to find an optimum solvent for selective extraction of thiophene, was presented by using DFT and MD simulations. As per the reactivity descriptors computed from Koopmans’ theorem based on quantum mechanics, for the eight solvents studied, furfural is most reactive followed by cyrene while sulfolane has the least reactivity. Based on the interaction energies (IE) of solute–solvent systems using DFT, cyrene presented strongest interaction with thiophene followed by TEG, furfural and DEG indicating that cyrene can show good thiophene removal capacity. The difference in the IE values of thiophene and isooctance was considered as a measure of possible sulphur selectivity over hydrocarbon. Among the eight solvents considered, furfural, DEG, TEG and cyrene observed to show good desulfurization selectivity. The favourable positions on solvent molecules for potential interactions with thiophene and isooctane were identified using orbitals, electrostatic potential maps, fukui function maps for electrophilic and nucleophilic attack, match well with the trends in IE values and RDFs from MD simulation. The solute–solvent concentration profiles and radial distribution functions computed using MD simulations evidently show that furfural and cyrene show better capacity and selectivity for Thiophene which are in correspondence with DFT results. The detailed analysis using QM and MM methods, concludes that cyrene, furfural and TEG are the optimum organic solvents for thiophene removal from gasoline using extractive desulfurization method (EDS). © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

Environmental Science and Engineering

Screening of Organic Solvents for Separation of Thiophene and Iso-octane: Density Functional Theory and Molecular Dynamic Simulations

The effectiveness of CO2 absorption in ionic liquids (ILs) depends on the physical properties of cations/anions of the IL and their influence on ion-ion and ion-CO2 interactions. A molecular understanding of these cation-anion and ion-CO2 interactions is vital to identify promising ILs for CO2 capture. Koopmans' theorem based on quantum mechanics was used to compute several interaction descriptors, such as ionization potential (IP), electron affinity (EA), chemical potential, chemical hardness, softness, and electrophilicity index for cations/anions/ILs. Density Functional Theory (DFT) studies were performed to obtain interaction energies (IE) for ion-ion and ion-CO2 interactions. Several cations (imidazolium-based and pyridinium-based), inorganic (F¯, BF4¯, etc.) and organic anions ([TF2N]¯, [bFAP]¯, etc.) and cation-anion combinations were considered in the present study. The analysis of different interaction descriptors provided a better understanding of the relationships between the EA of cation, the IP of anion, and cation-anion IE values with the experimental CO2 solubility. Several inferences can be made based on the results obtained: a) the cation-anion interaction energy and IP of the anion have a strong correlation with the CO2 solubility, b) the IE trends of ion-CO2 and CO2-IL alone do not correlate well with the experimental CO2 solubility trends, (c) free molecular volume or interstitial spaces resulting from entropic effects of cation-anion interactions due to the nature/structure of cation and anion, play a dominant role for an effective CO2 absorption, (d) for a particular anion, changing the cation does not significantly influence cation-anion IE and ion-CO2 IE values, while for a particular cation, the nature of anion dramatically influences cation-anion IE and ion-CO2 IE values – consistent with the experimental CO2 solubility trends. Of the anions and cations studied, the combination of anions containing fluoroalkyl groups, such as [TF2N]¯ and [bFAP]¯, with the cations, such as [hmim]+ and [hmpy]+ constitute promising solvents for efficient CO2 capture. The findings of this study emphasize the importance of assessing cation-anion and ion-CO2 interactions in conjunction with other interaction descriptors to design efficient solvents for CO2 capture. © 2020

Journal of Molecular Liquids

Molecular understanding of carbon dioxide interactions with ionic liquids

Carbon dioxide permeation studies were conducted on polyether-sulfone (PES) microspheres fabricated using phase-inversion technique by loading various amine-functionalized imidazolium cation ILs with a common anion bis-trifluoromethylsulfonylamide ([TF2N]−) on PES-polymer matrix. The cations include: Aminopropyl-butyl-imidazolium [APBIM], Diethyl-aminoethyl-imidazolium [DEAEBIM], Diaminopropyl-butyl-imidazolium [DMAPBIM]. Breakthrough adsorption of CO2 and CH4 was studied with a feed composition of 20\% CO2, 20\% CH4 and 60\% N2 by weight (4.835 mmol/L of CO2, 13.296 mmol/L of CH4 and 22.794 mmol/L of N2), at flow rates of 22 and 36 mL/min (superficial gas velocities are 0.29 cm/s and 0.47 cm/s). Among the ILs studied, [APBIM] showed maximum CO2 permeation. Results indicate that pore size and porosity are crucial for better CO2 absorption and need of further modification to microspheres morphology. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

Adsorption

Ionic liquid loaded polyether sulfone microspheres for CO2 separation

Several amino acid anion (aminate) based ionic liquids (ILs) were synthesized, characterized and tested for CO2 absorption capacity. Butylmethyl imidazolium ([bmim]+) was chosen as the cation for all the ILs studied. Among all the aminate-ILs studied, arginate anion ([ARG]) IL has shown more CO2 absorption capacity followed by lysinate ([LYS]) and histidinate ([HIS]) in terms of mol CO2/mol IL. The high CO2 absorption capacity of [ARG] anion was attributed to the availability of more accessible amine (N) groups. The CO2 molar uptake in aminate-ILs studied is in the order of [ARG] (4N)&gt;[LYS] (2N)&gt;[HIS] (3N)&gt;[MET] (1N)&gt;[LEU] (1N)&gt;[GLY] (1N)&gt;[VAL] (1N)&gt;[ALA] (1N)&gt;[PRO] (1N). The FTIR of the CO2 absorbed aminate-ILs confirms the chemical absorption of CO2 through the formation of carbamate species. The aminate-ILs showed higher CO2 solubility compared to amine functionalized cation ILs and non-functionalized ILs. On mass basis (gCO2/kg IL), aminate-ILs showed 70% more CO2 absorption capacity than primary amine-cation ILs, 150% more than tertiary amine-cation ILs and 600% more than non-functionalized ILs. © 2014 Elsevier B.V.

Chemical Engineering Journal

CO2 absorption studies in amino acid-anion based ionic liquids

Several amine-functionalized cation ILs were successfully synthesized, characterized and tested for CO2 absorption studies. Non-functionalized ILs were studied for comparison purpose. The primary amine-ILs have shown higher CO2 solubilities both on molar basis (mol of CO2/mol of IL) and on volume basis (g of CO2/L of IL), compared to non-functionalized and tertiary-amine ILs. Besides amine-functionalization of the cation, anion of the IL has strong influence on CO2 solubility due to its contribution by physical absorption. As a result, the [TF2N]-anion amine-ILs have higher CO2 solubility than [BF4]-anion amine-ILs. Among non-amine functionalized ILs, [P(14)666][TF2N] has the highest CO2 solubility. © 2013 The Korean Society of Industrial and Engineering Chemistry.

Journal of Industrial and Engineering Chemistry

Carbon dioxide absorption studies using amine-functionalized ionic liquids

The present study attempts to screen a number of ionic liquids (ILs) for CO 2 capture and its separation from flue gas mixture based on Hildebrand solubility parameter (δ). Solubility parameters of various ILs have been computed through molecular dynamic simulations in Material Studio. Initially the density and solubility parameters of seven ILs have been validated with experimental values available in the literature and are found to be in close correspondence. A group contribution correlation for δ of IL is developed and expressed as the weighted sum of attractions and repulsions of cation and anion as: δIL2=0.6 δcaδan-0. 2δca2-0.2δan2. This correlation was used to find out the δ values of cation and anion. The solubility parameters of 21 cations and 10 anions have successfully been determined by using δ values of 31 ILs and the correlation. Furthermore, using δ values of 21 cations and 10 anions and the group contribution correlation, the δ values of 210 ILs have been predicted. The δ values obtained by correlation match well with the δ values obtained by direct molecular simulations for twenty seven ILs, suggesting that correlation equation is reliable to predict the δ values of several ILs. Furthermore, comparison of the literature solubility data of different gases in ILs with that of solubility parameters in the present study reveals that the δ values are able to successfully explain the experimental solubility trends. Of all ILs studied, δ values of phosphonium cation based ILs (δ = 20.7-18.3 MPa 0.5) and ILs containing tris(nonafluorobutyl)trifluorophosphate ([bFAP] -) anion (δ = 20.5-18.3 MPa 0.5) are observed to be closer to that of CO 2 (δ = 17.85 MPa 0.5) and are significantly far from that of other flue gases like CH 4, N 2, H 2 and H 2O. Thus, by using the fluorinated anion and phosphonium cation based ILs, CO 2 can be more selectively separated from the major flue gases. © 2012 Elsevier B.V. All rights reserved.

Separation and Purification Technology

Validation and prediction of solubility parameters of ionic liquids for CO 2 capture

Henry's constant H of carbon dioxide in a number of ionic liquids (ILs) has been studied using the predictive method COnductor-like Screening MOdel for Realistic Solvation (COSMO-RS). Experimental H values for 14 CO2-IL systems spread over a temperature range of (283 to 333) K have been used to estimate the parameters λ1 and λ2 of the combinatorial term to calculate the chemical potential. The H values of CO 2 in 18 other ILs have been validated and found to be in good agreement with the experimental data with a relative deviation of less than 10 %. Cation groups like imidazolium, pyridinium, ammonium, uronium, thiouronium, and phosphonium have been studied. A total of 12 anions such as L-, BF4-, EtSO4-, TFA-, OctSO4-, Tf2N-, mFAB-, eFAB-, mFAP-, eFAP-, pFAP-, and bFAP- were studied to find the most favorable cation and anion combination for high CO2 solubility. It was observed that increasing the fluorination of organic anions containing fluoro alkyl groups gave lower Henry's constant values (following the trend TFA- &gt; Tf 2N- &gt; mFAB- &gt; eFAB- &gt; mFAP- &gt; eFAP- &gt; pFAP- &gt; bFAP -), thus showing higher CO2 solubility. Among the cations studied, phosphonium-based cations are found to be most promising for higher solubility. It was observed that the entropic effects (combinatorial) arising due to the size and shape of ILs play a major role in the estimation of H values, whereas the enthalpic effects (residual) arising due to molecular interactions have a minor but significant role. A correlation has been developed to predict the H of the [Rnmim]+ cation-based IL by considering a reference value H2 of [R2mim]+. A common predictive equation has been developed to determine the temperature-dependent H values of CO2 in any cation/anion combination of ILs. © 2011 American Chemical Society.

Journal of Chemical and Engineering Data

Validation and prediction of the temperature-dependent Henry's constant for CO2-ionic liquid systems using the Conductor-like Screening Model for Realistic Solvation (COSMO-RS)