A Computational Exploration of H2S and CO2 Capture by Ionic

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A Computational Exploration of HS and CO Capture by Ionic Liquids Based on #-Amino Acid Anion and N,N-Dimethyladeninium Cation 7

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Badrosadat Seyedhosseini, Mohammad Izadyar, and Mohammad Reza Housaindokht J. Phys. Chem. A, Just Accepted Manuscript • Publication Date (Web): 18 May 2017 Downloaded from http://pubs.acs.org on May 19, 2017

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The Journal of Physical Chemistry

A Computational Exploration of H2S and CO2 Capture by Ionic

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Liquids Based on α-Amino Acid Anion and N7,N9-

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dimethyladeninium Cation

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Badrosadat Seyedhosseini a, Mohammad Izadyar b* , Mohammad Reza Housaindokht b

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Department of Chemistry, Ferdowsi University of Mashhad, International Campus, Mashhad, Iran

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b

Department of Chemistry, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, Iran

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* Corresponding author. E-mail address: [email protected] (M. Izadyar).

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a

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1 ACS Paragon Plus Environment


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Abstract

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Hydrogen sulfide (H2S) and carbon dioxide (CO2) adsorption on a series

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of the aliphatic amino acid ionic liquids (AAILs) composed of N7,N9-

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dimethyladeninium cation with amino acid anions (AA= Gly, Ala, Val, Leu and

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Ile) as the functionalized ILs with dual groups of amine have been investigated.

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Based on the obtained data, the possible sites of H2S adsorption are twice as CO2

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on the ionic liquids and also the average adsorption energy of H2S (∆E=-51.5

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kJ.mol-1) in the most stable region of adsorption is twice greater than that of CO2

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(∆E=-25.5 kJ.mol-1). An increase in the length of the side chain of the amino acids

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increases the interaction energy of the H2S and CO2 capture (on the amine group

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of the [AA]- anions). Quantum theory of atoms in molecules analysis confirmed

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the non-covalent nature of the N…C bond formed between CO2 and N atom in

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both of the amine groups and S-H…O and S-H…N bond critical points of H2S

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on [dMA][AA]. Natural bond orbital analysis indicates that charge transfer in H2S

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adsorption is more important than CO2 capture. Finally, a correlation between the

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adsorption energy and the sum of stability energies (∑E(2)) in the most stable

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region has been obtained and discussed.

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1. Introduction

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Fossil fuels are currently the main energy source, thus remain the most

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important energy sources in the world in the near future.1,2 Particularly, demands

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on natural gas for fuels and for hydrocarbon-based material manufactures have

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been significantly increased.2 However, there are numerous impurities present in

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the oil and gas production process; along with hydrocarbons, the acid gases CO 2

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and H2S are co-produced in various concentrations depending on the underground

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soil characteristics and locations.3 Acid gases must be removed to avoid

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technological problems during the transport of oil and gas. Hydrogen sulfide is a

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toxic and corrosive compound, and prolonged exposure is proven to cause severe

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health problems and efficiency of energy utilization.3,4

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Aqueous alkanolamine solutions are widely used for the removal of acid

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gases, such as CO2 and H2S from industrial, flue and natural gases.

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Alkanolamines present several disadvantages such as loss of amine reagent,

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toxicity, degradation of amine to form corrosive by-product, high energy

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consumption and transfer of water into the gas stream during the desorption

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stage.5,6 These mentioned disadvantages allusion to find alternative methods for

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acid gas capture. In recent years, a promising new solvent such as ionic liquids

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(ILs) for CO2 and H2S is investigated as absorbents.4

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Ionic liquids (ILs) have been recognized as novel designable solvents,

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which are liquids over a wide temperature range controlled by tailoring their

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cationic and anionic structures to optimize their physicochemical properties. As

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a kind of extraction solvent, IL does not remain in the organic phase, which can

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be greatly convenient for separation and therefore, the desulfurization of oil and

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gas using ILs has received growing attention.7-10

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Design and optimization of the acid gas removal units need the

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experimental data of physical properties and acid gas solubility.11 ILs which are

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immiscible with oil and containing halogen-free materials were used for oxidative

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desulfurization as both the catalyst and extraction.12,13 The ILs can be recycled

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five times without any apparent loss of the catalytic activity.13

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ILs as the selective extraction agents of sulfur compounds are discussed

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separately, because of their novelty and theoretical interest.8 The use of ionic

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liquids for selective extraction of sulfur compounds from gas oil was described

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for the first time by Bösman et al..14

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Hydrogen bonds play a major role in determining the RTIL structure,

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aggregation state, and solvation behavior.15,16 Hydrogen bonds are usually created

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between the heterocyclic ring of the cation and polar moiety of the anion.

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Furthermore, the cation can be functionalized to offer competitive hydrogen

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bonding sites, instead of the inert hydrocarbon chain.17 Both the cation and anion

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can participate in solvation and gas capture. The specific behavior depends on the

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chemical identities of the cation, anion, and the solute.18

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Pomelli and coworkers showed the potential of RTILs in oil desulfurization

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and reported an acceptable correlation between the experimental solubility and

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calculated binding energy of small complexes of the H2S anion.19 These

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complexes did not include the cation, however. Although the correlation has been

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successfully established, neglecting the cation may have a dramatic consequence.

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The effect of the liquid phase can only be captured if both ions are considered in

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the calculations. Furthermore, it is better to include an ion pair than a single cation

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or anion.

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Damas and coworkers studied the interactions between the polar gas

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molecules (CO2, SO2, and H2S) and ions constituting RTILs at the B3LYP/6-

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311+G(d,p) level of theory.20 The experimentally observed high CO2 solubility

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in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide is caused by

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weakening the cation-anion binding. This weakening increases the free volume

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in RTIL providing more space to absorb gases (entropic contribution). Therefore,

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the interactions between cation−anion in the ion pair are the most important to

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evaluate the solubility, considering the magnitude of the binding energy values

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in comparison to anion−gas and cation−gas ones, which are approximately ten

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times lower.20

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The amount of information, theoretical or experimental for the H2S−IL

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system is limited and exists only for some ionic liquids, such as [C4mim][PF 6],

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[C4mim][BF4], [Cnmim]- [Tf2N], and [C4mim][Cl].19,21-23 In contrast, the amount

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of information available for CO2 is large and continues to grow. 20,23-28

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As the initial step in this work, we focused on the design and investigation

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of H2S capture on several AAILs composed of the N7, N9 - dimethyladeninium

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cation and amino acid anions ([dMA]+[AA]− (AA = Gly, Ala, Val, Leu, Ileu)).

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Adenine is a purine and it is an integral part of DNA, RNA, and ATP. It has the

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ability to store and transfer information through Watson–Crick base pairing and

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a major energy source that is derived from the cellular respiration. Moreover,

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Adenine, in comparison to imidazole, has a larger volume and lower symmetry.

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Thus, the ILs based on adenine not only could improve its thermal stability, but

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also have a higher selectivity to nucleic acid, and so more favorable for some

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biological reactions. Also, the N7,N9-dimethyladeninium cation with respect to

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the imidazolium cation has several suitable sites for H2S adsorption and is able to

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react with CO2. Thermodynamic parameters of H2S capture with the [dMA][AA]

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ILs as an AAIL functionalized with dual amine groups on the cation and anion

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were characterized. As well as, the effects of the alkyl side chain length of the

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aliphatic amino acid functional group on the performance of H2S adsorption have

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been investigated. The adsorption of CO2 in the same ILs was also investigated

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in order to compare the behavior of H2S adsorption with that of CO2. Binding

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energy considerations based on the density functional theory (DFT) (utilizing the

138

B3LYPand M06-2X functionals) have been performed for a variety of simple

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gas-phase complexes. Moreover, properties extracted from the quantum theory

140

of atoms in molecules (QTAIM) and natural bond orbital analysis (NBO) were

141

used to determine the nature and strength of CO2 and H2S adsorption.

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2. Theoretical methods

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The hybrid density functional theory (DFT) methods of the B3LYP and

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M06-2X functionals as implemented in the Gaussian 09 program were used with

146

the standard 6-311++G(d,p) basis set at 298 K and 1 atm.29-31 Previous studies

147

demonstrated that the DFT method is suitable for the calculation of ILs and shows

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good agreement with the experimental data.20 According to Izgorodina et al.42 the

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presence of extended alkyl chains in cations from ILs results in nanoscale

150

segregation, where nonpolar domains are controlled by dispersive forces, the

151

contributions from these forces in the equilibrium structure and the

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binding/interaction energies becoming significant. M06-2X functional was

153

applied to overcome the problem of the dispersion forces in DFT methods. To

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make sure that the most stable geometries were taken, different initial geometries

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were chosen for the studied AAILs.

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Selected anions were arranged around the cation at the positions where

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there was some probability of interaction with the hydrogen atoms in the cation.

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Based on the previous study, five regions (S1–S5) were analyzed for

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intermolecular H-bond and [dMA][AA]S1 configurations were used as the most

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stable forms in the study of H2S and CO2 capture on the ILs.32

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All of the optimized geometries were confirmed to be located as the

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minima on the potential energy surfaces by performing the normal vibration

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frequency analysis. Changes in enthalpy, Gibbs energy and entropy of H2S (or

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CO2) adsorption on the AAILs were obtained according to equations 1-3,

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respectively.

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∆H=H(H2S-[dMA][AA])-(H[dMA][AA] +H[H2S])

(eq.1)

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∆G=G(H2S-[dMA][AA])-(G[dMA][AA] +G[H2S])

(eq.2)

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∆S=S(H2S-[dMA][AA])-(S[dMA][AA] +S[H2S])

(eq.3)

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Where H, G and S are the thermodynamic parameters obtained from the

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frequency calculation outputs, including the thermal corrections and zero-point

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vibrational energies. (H2S-[dMA][AA]), [dMA][AA] and [H2S] means the

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corresponding complex of the adsorbed gas by [dMA][AA], isolated ionic liquids

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and H2S, respectively.

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Natural bond orbital (NBO) description has been carried out to explore the

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distribution of the electrons into the atomic and molecular orbitals.33 On the basis

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of this analysis, donor-acceptor interactions for [dMA][AA] (AA= Gly, Ala, Val,

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Leu and Ile) ion pairs, H2S and CO2 were fully investigated.

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The electron localization function (ELF), localized orbital locator (LOL)

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and topological analyses were performed, using the quantum theory of atoms in

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molecules (QTAIM) by MultiWFN 3.1 with the wave functions generated from

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the B3LYP/6-311++G(p,d) results.

34-36

In this tool, there is one bond critical

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point (BCP) between each pair of atoms bonded or interacting, where a critical

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point is defined by the point localized between two attractors. The electron

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density associated with all critical points (ρtotal) involved in the interaction is

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correlated to its strength. On the other hand, the Laplacian of the density (∇2ρ)

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indicates regions with a concentration of local charge and presents a negative sign

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when a bond occurs, and a positive one defining a weak interaction.37

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3. Results and discussion

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3.1. Structural and energy analysis

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At first, H2S adsorption processes were designed by [dMA][AA] ILs from

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different active sites and locally stable conformations were determined. The

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reaction of the amino acids or amino salts with H2S is thought to take place by a

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proton transfer mechanism:38

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RNH2 + H2S

HS- + RNH3+ (eq.4)


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Therefore, a specific interaction between the H2S molecule and the

196

nitrogen and the oxygen atoms of the carboxyl and amine groups of AAIL is

197

found. For this purpose, H2S was located at the favorable sites on the AAILs and

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several initial configurations were constructed for geometry optimization to

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explore the highest interaction energy. Based on these analyses, four suitable

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regions were determined as the most appropriate configurations, described by r1,

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r2, r3 and r4 as shown in Scheme1. For this system, adsorption energy (∆E) was

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evaluated according to equation 5.

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∆E=E(H2S-[dMA][AA])-(E[dMA][AA] +E[H2S]) (eq.5)

204

Where E(H2S-[dMA][AA]), E[dMA][AA] and E[H2S] are the energies of the H2S-

205

[dMA][AA] complex and energy of the isolated [dMA][AA] ILs and H2S,

206

respectively. Figure 1 shows four stable configurations for the H2S adsorption on

207

the [dMA][Gly] as an example.

208

r4

209 210

r1

CH3 N

N

7

9

N

N

NH2

8

23

27 H O

212

NH2

3 C CH

CH3 O26

211

H 2S

213 214

R

215

r2

216

r3 217

Scheme 1: The most probable regions of H2S interaction, r1-r4, with [dMA][AA] within atom numbering.

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Fig 1.Different optimized configurations of the H2S adsorption on the [dMA][Gly].

222 223

Region r2 is related to the most stable configuration and shows the highest

224

interaction energy. In order to study the role of alkyl side chain of the amino acids

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on the H2S adsorption energy, the most stable structures of the [dMA][AA]

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([AA]=Ala, Val, Ileu and Leu) were optimized and four regions were selected for

227

interaction with H2S. Thermodynamic parameters have been calculated and

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reported in Table 1. The calculated adsorption energies of these AAILs

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demonstrated that configurations of r2 and r4 have the lowest and the highest

230

energy of adsorption, respectively. The final complexes of the H2S-[dMA][AA]

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at region are shown in Figure 2.

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Fig 2. Final optimized complexes of the H2S-[dMA][AA] at r2 region.

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To compare the interaction energies of the H2S and CO2 adsorption on the

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ILs of [dMA][AA], the probable geometries were designed and thermodynamic

238

parameters were calculated. As an example, Figure 3 shows four optimized

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configurations obtained by CO2 capture on the possible regions of the

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[dMA][Gly] within the energies of adsorption. According to Figure 3, (1) and (3)

241

states as the most stable complexes were obtained. To study the alkyl side chain

242

effect in the amino acid part of the AAILs on the CO2 adsorption a similar

243

procedure as previously mentioned on the H2S adsorption was considered.

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Fig 3. Optimized structures obtained by CO2 adsorption on the IL of the [dMA][GLy] at four regions of 1-4 within the adsorption energies.

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In this case, the most stable geometries of (1) and (3) were obtained which

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are shown in Figure 4. Thermodynamic parameters for all the studied

251

configurations of the CO2 and H2S adsorption have been reported in Table 1.

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According to the obtained results, CO2 and H2S adsorption on the amine

253

group of the amino acid anions are thermodynamically more favorable than other

254

regions (ΔG 0 ). Adsorption energies of H2S at the r2

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configuration, [dMA] [AA] -H2S (r2), is twice the corresponding value of the CO2

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capture.

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Fig 4. The most stable complexes of the CO2-[dMA][AA] ILs (AA= Ala, Val, Ile and Leu) in

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the configurations of (1) and (3).

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Table 1. Calculated thermodynamic parameters: E(energy, au), ∆G, ∆E, ∆H (kJ.mol-1) and ∆S(J.mol-1K-1) for H2S and CO2 capture on the [dMA][AA] ILs at the B3LYP/6311++G(d,p) level. Structure E ∆E ∆G ∆H ∆S [dMA][Gly]-H2S(r1) -1230.02815 -23.629 -5.513 -17.696 -41.35 [dMA][Gly]-H2S(r2) -1230.02886 -25.467 -2.363 -18.772 -55.09 [dMA][Gly]-H2S(r3) -1230.02491 -15.228 6.301 -9.740 -53.95 [dMA][Gly]-H2S(r4) -1230.02262 -9.189 -1.05 -4.253 -11.32 [dMA][Ala]-H2S(r1) -1269.35512 -23.104 -0.788 -19.326 -62.00 [dMA][Ala]-H2S(r2) -1269.35410 -25.730 2.153 -21.004 -65.16 [dMA][Ala]-H2S(r3) -1269.35114 -15.228 7.719 -12.182 -66.81 [dMA][Ala]-H2S(r4) -1269.34886 -9.171 6.222 -6.695 -43.36 [dMA][Val]-H2S(r1) -1347.99991 -22.579 1.573 -16.173 -59.22 [dMA][Val]-H2S(r2) -1348.00106 -25.730 1.838 -18.615 -68.49 [dMA][Val]-H2S(r3) -1347.99714 -15.228 9.137 -9.688 -63.03 [dMA][Val]-H2S(r4) -1347.99483 -9.189 8.743 -4.069 -42.93 [dMA][Leu]-H2S(r1) -1387.32538 -22.317 -0.026 -18.562 -62.24 [dMA][Leu]-H2S(r2) -1387.32664 -25.730 1.05 -21.398 -75.31 [dMA][Leu]-H2S(r3) -1387.32264 -15.228 7.22 -12.156 -65.06 [dMA][Leu]-H2S(r4) -1387.32032 -9.189 5.829 -6.590 -41.79 [dMA][Ile]-H2S(r1) -1387.32244 -22.579 -9.399 -16.304 -23.13 [dMA][Ile]-H2S(r2) -1387.32354 -25.467 -6.406 -18.326 -39.94 [dMA][Ile]-H2S(r3) -1387.31968 -15.49 1.838 -9.609 -38.33 [dMA][Ile]-H2S(r4) -1387.31737 -9.451 -1.103 -4.279 -10.60 CO2-[dMA][Gly] -1019.24821 -12.392 -3.964 -7.141 -10.71 [dMA][Gly]-CO2 -1019.24848 -13.101 -5.437 -7.640 -7.40 CO2-[dMA][Ala] -1058.57445 -12.917 -2.652 -7.614 -16.63 [dMA][Ala]-CO2 -1058.57427 -12.445 -3.282 -6.879 -12.03 CO2-[dMA][Val] -1137.22045 -12.917 4.673 -10.187 -49.91 [dMA][Val]-CO2 -1137.21999 -11.710 -1.995 -8.795 -22.93 CO2-[dMA][Leu] -1176.54592 -12.944 8.270 -10.029 -61.38 [dMA][Leu]-CO2 -1176.54557 -11.762 4.752 -8.874 -45.69 CO2-[dMA][Ile] -1176.54298 -12.812 4.988 -10.161 -50.75 [dMA][Ile]-CO2 -1176.54253 -11.893 2.179 -8.900 -37.09

This behavior is consistent with the interaction energy observed for

268

[C2mim][Tf2N] to [C8mim][Tf2N] in which the interaction of H2S with the anion

269

and cation parts of the IL is more energetic than those of CO2.21 Also, the enthalpy

270

changes of the H2S capture on the carboxyl group of amino acid part (r2) is more

271

than twice the value of CO2 adsorption on the ILs in both of regions (1) and (2).

272

These changes are the opposite of the entropy changes in all regions of r1 to r4.

273

Because of the importance of the dispersion interactions during the H2S

274

and CO2 capture, M06-2X functional have also been used on the optimized

275

structures within 6-311++G(d,p) basis set. Table 2 shows that the M06-2X results

276



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are in agreement with the B3LYP and the inclusion of the dispersion interactions

277

modified the B3LYP data on the adsorption energies. For example, at the lowest

278

state (r2), the average value of the adsorption energy for H2S is -55.5 kJ.mol-1

279

which is more than the corresponding value obtained by the B3LYP functional (-

280

25 kJ.mol-1).

281

Increasing the length of the alkyl side chain of the amino acids does not

282

have an important effect on the adsorption energy values and slightly decreases

283

the adsorption energies of the r2, r3 and r4 regions in contrast to r1 region. These

284

theoretical trends obtained by two functionals of M06-2X and B3LYP are the

285

same.

286

All complexes of H2S-[dMA][AA] are thermodynamically favorable

287

(∆Gr1>r3> r4.

290

Comparison between the M06-2X data and B3LYP shows a greater value

291

of absolute exothermicity for the first functional, showing the importance of the

292

dispersion interactions in this type of molecular interactions. The presence of the

293

alkyl chains in the cation parts of the AAILs results in nonpolar domains, which

294

are controlled by dispersion forces whose contribution in the equilibrium

295

structures, adsorption energies and thermodynamic parameters is of significance.

296

To compare H2S and CO2 adsorption, M06-2X functional calculations with

297

the basis set 6-311 ++ G (d, p) for all combinations of CO2 adsorption on the ionic

298

liquids of the [dMA] [AA] were performed. Based on the results, H2S adsorption

299

energy obtained in the stable region (r2) is twice as the value of CO2 in the regions

300

(1) and (3). As shown in Table 2, CO2 adsorption on both of the regions of (1)

301

and (3) is thermodynamically exothermic and favorable (ΔH CO2. Binding energies were obtained in the

474

range of -20 to -25 kJ.mol-1 for the cation-gas and -16 to -57 kJ.mol-1 for the

475

anion-gas complexes. In this study, the results indicated that CO 2 capture is

476

suitable on both of the anion and cation amine groups of [dMA][AA] ILs. Also,

477

there are more suitable sites for H2S adsorption on [dMA][AA] ILs; this type of

478

ILs is therefore a better candidate than traditional ILs for H2S and CO2 adsorption.

479 480

4. Conclusion

481

In this work, we summarized new and promising developments in H2S and

482

CO2 capture media, focusing on novel amine acid-based ILs. [dMA][AA]

483

(AA=Gly, Ala, Val, Leu and Ile) as the ILs with two groups of amine in anion

484

and cation parts were designed. DFT calculations in the gas phase have been

485

employed to investigate the ability of the [dMA][AA] ILs in H2S and CO2

486

capture. The main conclusions are as follows:

487

1. Physical adsorption processes of CO2 and H2S on [dMA][AA] were

488

studied and compared with B3LYP and M06-2X functionals. According to

489

obtained results, more accurate results were obtained by considering dispersion

490

forces.

491


Page 25 of 31

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2. Suitable sites of H2S adsorption are four regions which are twice of the suitable

sites

for

CO2

adsorption.

M06-2X

functional

492

predicted

493

thermodynamically favorable all four regions, but B3LYP functional only r1

494

region the thermodynamically possible.

495

3. Interaction energy and thermodynamic parameters of the H2S adsorption

496

in the stable region (r2) is twice as the values obtained for the CO2 capture in the

497

stable regions (1) and (2).

498

4. Natural bond orbital analysis and further assessments of the LOL and

499

ELF showed that the H2S capture is more favorable than CO2 adsorption and side-

500

chain length elongation of the [AA]− does not affect the adsorption energies.

501

5. Acknowledgment

502

Research Council of the Ferdowsi University of Mashhad, International

503

Campus, is gratefully acknowledged for financial supports (Grant No. 3/31938,

504

12/7/93).

505 506

References

507

(1) Shell energy scenario to 2050, Royal Dutch Shell, The Hague, Netherland.

508

2008.

509

(2) World Energy Outlook 2012, International Energy Agency, Paris, France.

510

2012.

511

(3) Handy, H.; Santoso, A.; Widodo, A.; Palgunadi, J.; Soerawidjaja, T. H.;

512

Indarto, A. H2S–CO2 separation using room temperature ionic liquid

513

[BMIM][Br]. Separ. Sci.Technol. 2014, 49, 2079–2084.

514

(4) Huang, K.; Feng, X.; Zhang, X.M.; Wu, Y.T.; Hu, X.B. The ionic liquid-

515

mediated claus reaction: A highly efficient capture and conversion of hydrogen

516

sulfide. Green Chem. 2016, 18, 1859-1863.

517



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 31

(5) Munder, B.; Lidal, H.; Sandall, O. C. Physical solubility of hydrogen sulfide

518

in aqueous solutions of 2-(tert-butylamineo)ethanol. J. Chem. Eng. Data 2000,

519

45, 1201−1204.

520

(6) Huttenhuis, P. J. G.; Agrawal, N. J.; Hogendoorn, J. A.; Versteeg, G. F. Gas

521

solubility of H2S and CO2 in aqueous solutions of N-methyldiethanolamine. J.

522

Pet. Sci. Eng. 2007, 55, 122−134.

523

(7) Zhang, S.G.; Zhang, Q.L.; Zhang, Z.C. Extractive desulfurization and

524

denitrogenation of fuels using ionic liquids. J. Ind. Eng. Chem. Res. 2004, 43,

525

614-622.

526

(8) Morsy, S. M. I.; Shaban, S. A. Investigation of ionic liquid with and without

527

suspension of nanomaterials as catalysis for sulfur removal from gas oil at room

528

temperature. Int.J.Curr.Microbiol.App.Sci. 2014, 3, 167-180.

529

(9) Xuemei, C.; Yufeng, H.; Jiguang, L.; Qianqing, L.; Yansheng, L.; Xianming,

530

Z.; Xiaoming, P.; Wenjia, Y. Desulfurization of diesel fuel by extraction with

531

[BF4]- -based ionic liquids. Chin. J. Chem. Eng. 2008, 16, 881-884.

532

(10) Alonso, L.; Arce, A.; Francisco, M.; Soto, A. Solvent extraction of thiophene

533

from n-alkanes (C7, C12, and C16) using the ionic liquid [C8mim][BF4]. J. Chem.

534

Thermodyn. 2008, 40, 966-972.

535

(11) L.Anthony, J.; Maginn, E. J.; Brennecke, J. F. Solubilities and

536

thermodynamic properties of gases in the ionic liquid 1-n-butyl-3-

537

methylimidazolium hexafluorophosphate. J. Phys. Chem. B 2002, 106,

538

7315−7320.

539

(12) Rang, H.; Kann, J.; Oja, V. Advances in desulfurization research of liquid

540

fuel, Oil Shale. 2006, 23, 164-176.

541

(13) Guia, J.; Liu, D.; Sun, Z.; Liu, D.; Min, D.; Song, B.; Peng, X. Deep oxidative

542

desulfurization with task-specific ionic liquids: An experimental and

543

computational study. J. Mol. Catal. 2010, 331, 64-70.

544


Page 27 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(14) Bosman, A.; Datsevich, L.; Jess, A.; Lauter, A.; Schmitz, C.; Wasserscheid,

545

P. Deep desulfurization of diesel fuel by extraction with ionic liquids. J. Chem.,

546

Comm. 2001, 23, 2494-2495.

547

(15) Deng, L.; Shi, R.; Wang, Y. T.; Ou-Yang, Z. C. Hydrogen-bond rich ionic

548

liquids with hydroxyl cationic tails. Chem. Phys. Lett. 2013, 560, 32-36.

549

(16) Nishimura, Y.; Yokogawa, D.; Irle, S. Theoretical study of cellobiose

550

hydrolysis to glucose in ionic liquids. Chem. Phys. Lett. 2014, 603, 7-12.

551

(17) Chaban, V. V.; Prezhdo, O. V. Ionic and molecular liquids: Working

552

together for robust engineering. J. Phys. Chem. Lett. 2013, 4, 1423-1431.

553

(18) Chaban, V. The thiocyanate anion is a primary driver of carbon dioxide

554

capture by ionic liquids. Chem. Phys. Lett. 2015, 618, 89-93.

555

(19) Pomelli, C. S.; Chiappe, C.; Vidis, A.; Laurenczy, G.; Dyson, P. J. Influence

556

of the interaction between hydrogen sulfide and ionic liquids on solubility:

557

Experimental and theoretical investigation. J. Phys. Chem. B 2007, 111, 13014-

558

13019.

559

(20) Damas, G. B.; Dias, A. B. A.; Costa, L. T. A quantum chemistry study for

560

ionic liquids applied to gas capture and separation. J. Phys. Chem. B 2014, 118,

561

9046-9064.

562

(21) Jalili, A. H.; Safavi, M.; Ghotbi, C.; Mehdizadeh, A.; Hosseini-Jenab, M.;

563

Taghikhani, V. Solubility of CO2, H2S, and their mixture in the ionic liquid

564

1-Octyl-3-methylimidazolium Bis(trifluoromethyl)sulfonylimide. J. Phys. Chem.

565

B 2012, 116, 2758−2774.

566

(22) Jou, F. Y.; Mather, A. E. Solubility of hydrogen sulfide in [bmim][PF6].

567

Int. J. Thermophys. 2007, 28, 490−495.

568

(23) Liu, H.; Dai, S.; Jiang, D. Solubility of gases in a common ionic liquid

569

from molecular dynamics based free energy calculations. J. Phys. Chem.

570

B 2014, 118, 2719−2725.

571

(24) nchez-Badillo, J. S.; Gallo, M.; Alvarado, S.; Glossman-Mitnik, D. Solvation

572

thermodynamic properties of hydrogen sulfide in [C4mim][PF6], [C4mim][BF4],

573



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 31

and [C4mim][Cl] ionic liquids, determined by molecular simulations. J. Phys.

574

Chem. B 2015, 119, 10727−10737.

575

(25) Yang, Q.; Wang, Z.; Bao, Z.; Zhang, Z.; Yang, Y.; Ren, Q.; Xing, H.; ai,

576

S.D. New insights into CO2 absorption mechanisms with amino-acid ionic

577

liquids. ChemSusChem. 2016, 9, 806–812.

578

(26) Kerle, D.; Ludwig, R.; Geiger, A.; Pascheck, D. Temperature dependence of

579

the solubility of carbon dioxide in imidazolium-based ionic liquids. J. Phys.

580

Chem. B 2009, 113, 12727−12735.

581

(27) Wu, H.; Maginn, E. J. Water solubility and dynamics of CO2 capture ionic

582

liquids having aprotic heterocyclic anions. Fluid Phase Equilib. 2014, 368,

583

72−79.

584

(28) Jacquemin, J.; Husson, P.; Majer, V.; Costa Gomes, M. F. Low-pressure

585

solubilities and thermodynamics of solvation of eight gases in 1-butyl-3-

586

methylimidazolium hexafluorophosphate. Fluid Phase Equilib. 2006, 240,

587

87−95.

588

(29) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G.E.; Robb, M. A.;

589

Cheeseman, J. R.; Montgomery, J. A.; Barone, V.; Kudin, K. N.; Petersson, G.

590

A.; et al. Gaussian 09, Revision A.02; Gaussian. Inc.: Wallingford, CT, 2009.

591

(30) Hohenstein, E. G.; Chill, S. T.; Sherrill, C. D. Assessment of the

592

performance of the M05-2X and M06-2X exchange-correlation functionals for

593

noncovalent interactions in biomolecules. J. Chem. Theory Comput. 2008, 4,

594

1996-2000.

595

(31) Walker, M.; Harvey, A.J.M.; Sen, A.; Dessent, C.E.H. Performance of M06,

596

M06-2X, and M06-HF density functionals for conformationally flexible anionic

597

clusters: M06 functionals perform better than B3LYP for a model system with

598

dispersion and ionic hydrogen-bonding interactions. J. Phys. Chem. A 2013, 117,

599

12590- 12600.

600


Page 29 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(32) Seyedhosseini, B.; Izadyar, M.; Housaindokht, M.R. Ionic liquids based on

601

α-amino acids; a structural insights into [dMA][AA] and computational

602

evaluation of the hydrogen bonds. J. Mol. Liq. 2014, 200, 439–447.

603

(33) Ghiasi, R.; Mokaram, E. Natural bond orbital (NBO) population analysis of

604

iridabenzene (C5H5Ir)(PH3)3. J. Appl. Chem. Res. 2012, 20, 7- 13.

605

(34) Tsirelson, V.; Stash, A. Determination of the electron localization function

606

from electron density. Chem. Phys. Lett. 2002, 351, 142-148.

607

(35) Jacobsen, H. Localized-orbital locator (LOL) profiles of chemical bonding,

608

Can. J. Chem. 2008, 86, 695-702.

609

(36) Lu, T.; Chen, F.W. Multiwfn: A multifunctional wavefunction analyzer. J.

610

Comput. Chem. 2012, 33, 580-592.

611

(37) Bader, R. F. W. Atoms in Molecules: A Quantum Theory, 2nd ed.; Oxford

612

University Press: Oxford, UK, 1994.

613

(38) Zare Aliabad, H.; Mirzaei, S. Removal of CO2 and H2S using aqueous

614

alkanolamine solusions. Int. J. Chem. Mol. Nucl. Mater. Metall. Eng. 2009, 3, 50-

615

59.

616

(39) Causa, M.; D’Amore, M.; Gentile. F.; Menendez, M.; Calatayud, M.

617

Electron localization function and maximum probability domains analysis of

618

semi-ionic oxides crystals, surfaces and surface defects. Comput. Theoretical

619

Chem. 2015, 1053, 315–321.

620

(40) Lu, J.-G.; Lu, Z.-Y.; Gao, L.; Cao, S.; Wang, J. T.; Gao, X.; Tang Y.-Q.;

621

Tan, W.-Y. Property of diethanolamine glycinate ionic liquid and its performance

622

for CO2 capture. J. Mol. Liq. 2015, 211, 1–6.

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628 629 630 631 +

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632 633 634 635

"TOC Graphic"

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