Evaluation of Methanesulfonate-Based Deep ... - ACS Publications

Article pubs.acs.org/jced

Cite This: J. Chem. Eng. Data 2018, 63, 1896−1904

Evaluation of Methanesulfonate-Based Deep Eutectic Solvent for Ammonia Sorption Alsu I. Akhmetshina,†,‡ Anton N. Petukhov,† Amal Mechergui,† Andrey V. Vorotyntsev,† Alexander V. Nyuchev,§ Alexandr A. Moskvichev,∥ and Ilya V. Vorotyntsev*,† †

Nizhny Novgorod State Technical University n.a. R.E. Alekseev, 24 Minina Street, Nizhny Novgorod, 603950, Russian Federation Kazan National Research Technological University, 68 Karl Marks Street, Kazan, 420015, Russian Federation § N.I. Lobachevsky State University of Nizhny Novgorod, 23 Gagarin Avenue, Nizhny Novgorod 603950, Russian Federation ∥ Institute for Problems in Mechanical Engineering, Russian Academy of Sciences, 85 Belinskogo Street, Nizhny Novgorod 603024, Russian Federation

Downloaded via IOWA STATE UNIV on January 9, 2019 at 11:40:59 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

‡

ABSTRACT: The concept of eutectic solvents as a platform technology for a variety of applications including gas separation has become a popular approach. To date, the number of known deep eutectic solvents (DESs) is limited mainly to halide salts easily interacting with a hydrogen-bond donor (HBD) and resulting in the formation of a liquid phase. Actually, the DESs properties may be tuned by selecting the appropriate HBD, while the structure of the anion is not a decisive factor. However, the presence of other anions may be favorable for certain applications; therefore, expanding the range of deep eutectic solvents seems a relevant issue of chemistry and material science. In this study, we report the high absorption properties of the DES based on 1-butyl-3-methyl imidazolium methanesulfonate−urea toward ammonia. The structure features investigations have revealed the major contribution of C(2)-H to hydrogen bonding. To assess the possibility of selective separation, the solubility of ammonia and two acidic gases (H2S and CO2) in the absorbent has been measured. A superior gas sorption capacity was observed for ammonia, for which the Henry’s law constant was equal to 1.52 bar. The obtained results exceeded the solubility data reported in the literature for various ILs containing hydrogen-donating groups. The DESs demonstrated lower yet acceptable solubility toward hydrogen sulfide, whereas the solubility of CO2 was relatively poor. The thermostimulated desorption has demonstrated that the ability of gases to bind with DES molecules can be ranked as follows: NH3 > H2S > CO2. The physical sorption mechanism of ammonia, hydrogen sulfide, and carbon dioxide in the DES was proven by FTIR and thermal desorption analysis. The absorption was totally reversible, and the solubility of gases remains almost unchanged after three cycles.

1. INTRODUCTION

SO2 g mol/ILs g mol and 1.4 SO2 g mol/ILs g mol. ILs such as [bmim][MeSO3], [bmim][MeSO4], and [emim][MeSO4] showed lower yet acceptable solubilities ranging between 0.8 and 0.9 g mol/ILs g mol. In another work,23 Jung has tested the solubility of carbon dioxide in four different ILs with methanesulfonate anion. As concluded in previous works, the length of the alkyl chain linked to the imidazolium cation is functional in determining the gas solubility. CO2 solubility in the studied ILs ranged between 0.98 and 2.36 mol/kg depending on substituents at the imidazolium ring. Jin and co-workers have synthesized methanesulfonate ionic liquids and studied their physical properties and CO2 solubility.24 In general, methanesulfonate-based ILs have exhibited lower acidic gases solubilities than other ILs. However, according to the literature, the [MeSO3] anion has a significant ability to form hydrogen bonds with proton-donating groups.25 Only a few

Nowadays, molten salts and deep eutectic solvents (DESs) represent a prospective chemistry research field with many different applications including catalysis,1−3 electrochemistry,4,5 material chemistry,6−8 and separations,9−14 etc. In general, DESs are composed of two or more components forming a eutectic mixture (preferably liquid at room temperature) via hydrogen bonding. The formation of a liquid phase occurs due to the formation of anion−hydrogen-bond donor (HBD) supramolecular complexes following the change of the free energy in the eutectic system. Most of them are based on the quaternary ammonium salts mixed with HBDs, such as amides, carboxylic acids, or alcohols.15 Ionic liquids containing [MeSO3] were widely investigated as a reaction medium,16−18 solvating medium for polyelectrolytes,19 stationary phase for gas chromatography,20 and solvents for extraction.21 Gas solubility studies in such absorbents were performed by Lee and colleagues,22 which were hugely influenced by the type of the anions. [bmim][OAc] and [bmim][Cl] exhibited the highest SO2 with respectively 1.69 © 2018 American Chemical Society

Received: November 16, 2017 Accepted: April 26, 2018 Published: May 3, 2018 1896

DOI: 10.1021/acs.jced.7b01004 J. Chem. Eng. Data 2018, 63, 1896−1904

Journal of Chemical & Engineering Data

Article

Table 1. Chemicals Used in This Work compound 1-butyl-3-methyl imidazolium methanesulfonate

abbreviation [bmim] [MeSO3]

urea

supplier

final mass fraction purity

Sigma-Aldrich

0.995

Sigma-Aldrich

0.99 0.99 12 ± 2 ppm (H2O) 0.9999

[1-butyl-3-methyl imidazolium methanesulfonate]/ [urea] = 1:1

DES

this work

carbon dioxide

CO2

hydrogen sulfide

H2S

ammonia

NH3

Monitoring, Russia Monitoring, Russia Monitoring, Russia

0.9999 0.9999

purification method used without purification used without purification rotary evaporation

analysis method

NMR, Karl Fisher analysis

used without purification used without purification used without purification

Bearing this in mind, in our experiments we observed that the formation of the DES consisted of 1-butyl-3-methylimidazolium methanesulfonate and urea. On the basis of the above analysis, our study aims to determine the following targets: i. The structural features of 1-butyl-3-methylimidazolium methanesulfonate containing a deep eutectic solvent were investigated using FTIR and NMR spectroscopy; ii. The thermophysical properties such as density, viscosity, decomposition temperature, and melting point of the DES were determined; iii. The solubilities of ammonia and acidic gases (CO2 and H2S) were measured by the volumetric method, and the separation selectivity was calculated.

reports describe the preparation and the application of DESs containing [MeSO3], and among them the imidazolium methanesulfonate-1H-1,2,4-triazole mixture26 was tested for electrochemical purposes and the mixtures of quaternary ammonium salt bearing methanesulfonate as the counterion, with p-toluenesulfonic acid as the reaction media for esterification of carboxylic acid with alcohols.27 It is worth noting that the presence of a sulfonate group contributes to intermolecular interactions with various hydrogen-bond donors. Bearing this fact in mind, the H-bond acceptor parameters of different anions were determined by Pike et al.,28 who suggested that the highest hydrogen-bond acceptor (HBA) properties among the sulfonate group containing ILs were found with the [MeSO3] anion. Thus, according to preliminary estimations, it is possible for [MeSO3] based salts to form eutectic liquids via a supramolecular interaction with HBDs. The introduction of various HBDs such as amides, carboxylic acids, or glycols would make a certain impact on the absorption behavior of DESs. In fact, those components are capable of intermolecular interactions through hydrogen bonding generating materials with adjustable and tunable properties. Because of the arising effects from the organic salt−hydrogen-bond donors’ interactions, in comparison with ILs, DESs are considered as a suitable platform for the development of new materials with higher gas solubilities. For instance, the highest absorption capacity toward acidic gases was observed in choline chloride−urea and choline chloride−glycerol mixtures,29−31 while carboxylic acids-based DESs had relatively lower sorption capacity.32−36 Lastly, with regard to ammonia, the highest absorption properties were observed for the protic ionic liquid [bim][NTf2] with strong hydrogen donating ability35 and hybrid deep eutectic solvents with hydrogenbonded supramolecular network.36 Nowadays the highest ammonia sorption capacities were observed with ILs and DESs containing proton-donating groups, such as the N−H in 1-methylimidazolium cation,35 the O−H in the quaternary ammonium and heterocyclic cations,39 the carboxyl group,35 and the O−H group in phenols.36 In fact, all the above-mentioned compounds are able to form hydrogen bonds, in turn; ammonia will interact as a hydrogen acceptor with some weaker bases. The use of compounds with higher acidity such as carboxylic acids or phenols is more effective for ammonia sorption. However, upon mixing the [bmim][MeSO3] salt with carboxylic acids the DES becomes unrecyclable due to the precipitation of ammonium salts when reaching a certain temperature, while phenols-based DES is more toxic. Therefore, we’ve selected urea as a safe component able to hydrogen bond.

2. EXPERIMENTAL SECTION 2.1. Materials. Ammonia (99.99%), hydrogen sulfide (99.99%), and carbon dioxide (99.99%) were supplied from Monitoring, Russia. 1-Butyl-3-methyl imidazolium methanesulfonate (99.5% purity) and urea (99% purity) were purchased from Sigma-Aldrich. 2.2. Preparation and Characterization of the DES. The binary eutectic system was prepared by mixing 1-butyl-3-methyl imidazolium methanesulfonate [bmim][MeSO3] and urea at a molar ratio of 1:1 under heat for few minutes. The resultant viscous yellowish transparent liquid was dried under vacuum for 48 h to obtain the final product. The water content of the sample was measured by 831 Karl Fisher coulometer (Metrohm AG, Switzerland) and had been equal to 24 ppm (Table 1). 2.3. NMR Spectroscopy. 1H NMR spectra of the DES were recorded on a DD2 400 (Agilent, USA) spectrometer in deuterochloroform (CDCl3). [bmim][MeSO3] 1H NMR (300 MHz, CDCl3): δ (ppm) 0.91−1.29 (t, 3H, CH3), 1.31−1.39 (m, 2H, CH2), 1.81−1.88 (m, 2H, NCH2CH2), 2.75 (s, 3H, (SO3)CH3), 4.02 (m, 3H, NCH3), 4.22−4.25 (t, 2H, NCH2), 7.32 (m, 1H, ArH), 7.42 (m, 1H, ArH), 9.77 (m, 1H, ArH). 2.4. FTIR Spectroscopy. The FTIR spectrum of the DES was taken from 300 to 4000 cm−1 with 4 cm−1 resolution (by 30 scans, IRAfinity-1, Shimadzu, Japan). The measurements were carried out in ambient air at room temperature. The accuracy of wavenumber measurements (±0.2 cm−1) was determined using the spectrum of polystyrene.40−42 2.5. Viscosity and Density Measurements. The density of the DES was determined in the temperature range between 293 and 343 K, at atmospheric pressure and by Stabinger Viscometer SVM 3000 (Anton Paar, Austria) with an error of 0.00005 g cm−3. This apparatus was utilized to measure the 1897



Article

viscosity of the sample.43 The instrument was calibrated at three different temperatures (293, 333, and 353 K) using standard oils: APN7.5, APN26, and APN415. 2.6. Refractive Index Measurements. The refractive indexes of the DES were determined using the automatic refractometer ABBEMAT 500 (Anton Paar, Austria) with an uncertainty of ±5 × 10−5. Preliminarily, it was calibrated by measuring the refractive index of distilled water. 2.7. Gases Solubility. In this study, the experimental method used for measurement of gases solubility was already reported in the literature.44,45 A detailed description of the apparatus was represented in our previous work.46 The high pressure equilibrium cell (4) with an internal volume of 16.72 cm3, and the gas container (3) for the introduction of 35.24 cm3 CO2 are shown in Figure 1. The volumes of different

resulting chromatographic peaks. Ionization in the massspectrometer was performed by means of electron impact (EI) at 70 eV, at the range of mass numbers between 12 and 500 amu (2000 s/scan). Reaction products were separated on a column made of Ultra ALLOY EGA (Frontier Laboratories, Japan) at 373.15 K for 45 min by using selected ion monitoring and identified utilizing ≪GCMS Real Time Analysis≫ software. 2.9. Differential Scanning Calorimetry. DSC curves were recorded with a Jupiter STA 449 F1 (NETSCH, Selb, Germany) thermal analyzer in the temperature interval 173− 303 K with a ramping rate of 10 K/min in the argon atmosphere. The instrument was calibrated by indium (Tm at 429.75 K).

3. RESULTS AND DISCUSSION 3.1. FTIR and NMR Characterization. The FTIR spectra of neat [bmim][MeSO3] and the DES composed of [bmim][MeSO3]/urea = 1:1 are presented in Figure 2. In the IR

Figure 1. Experimental apparatus for the measurement of gas solubility. Sample of DES (1); vacuum post (2); container with gas (3); high pressure equilibrium cell (4); pressure transducers (5, 6); thermostatic bath (7); temperature sensor (8, 9); magnetic stirring system (10); valves (11,12,13); and cylinder with testing gas (14). Figure 2. IR spectra of [bmim][MeSO3] (1), the DES (2), and urea (3).

compartments of the apparatus were provisionally calibrated using a calibrated bulb of the known volume. The pressures in compartments (3) and (4) were measured with two pressure transducers CPG 1000 (5, 6) (WIKA GmbH, Germany) with an uncertainty of ±0.05% FS. The temperature within the thermostatic air bath (7) was controlled by a temperature sensor (8, 9) with an accuracy of ±0.1 K. The preweighted amount of the DES (1−2) was loaded into the cell, and the system was degassed for 24 h with valves 11 and 13 open. After the valves’ closure the exact amount of the gas (H2S or CO2) was introduced into the compartment (3) through valve 11. Thereafter, the valve to compartment (12) was opened in order to fully saturate the DES with absorbate. The determination of solubility at different temperature conditions was performed by changing the air thermostat set point with subsequent achievement of a new thermodynamic equilibrium. 2.8. Thermodesorption Analysis. The evolved gasanalysis (Direct EGA-MS) measurements were conducted by a Double-Shot Pyrolyzer EGA/PY-3030D (Frontier Laboratories, Japan) incorporated in GC−MS QP-2010Plus (Shimadzu, Japan). For our experiments, the deactivated stainless steel sample cup loaded with roughly 50 μg of sample was introduced into a quartz pyrolysis tube surrounded by a tubular furnace. The helium flow of 50 mL/min was held at the pyrolyzer and decreased to 1 mL/min at the capillary column. On the first stage of the temperature program, the temperature was maintained at 323.15 K for 10 min. Then, at the second stage the sample was heated from 323.15 to 773.15 K. At this stage, a mass selective detector was used to identify the

spectrum of [bmim][MeSO3], the bands in the region 2800− 3500 cm−1 are assigned to different C−H stretching vibrations of the imidazolium ring and methyl groups; among them, the broad peak at 3070 cm−1 corresponds to the C(2)-H stretching vibrations. The peaks between 1100 and 1347 cm−1 are addressed to S−OH bending, SO2− symmetric stretching, C−C stretching, (N)CH2 and (N)CH3CN stretching, and CH3 symmetric deformation vibrations. As for the peaks at 1058 and 785 cm−1, they are assigned to the S-CH3 rocking and C−S stretching mode, respectively.47 When [bmim][MeSO3] is mixed with urea several shifted peaks are observed. In general, the infrared spectrum of the DES exhibits the characteristic bands of both the pure [bmim][MeSO3] spectra and the pure urea spectra. Obviously, the peak assigned to C(2)-H vibrations at 3070 cm−1 is shifted by 10 cm−1 to a higher frequency at 3080 cm−1, indicating that the C(2)−H bond is strengthened as a result of diminishing the hydrogen-bond interaction between C(2)−H and methanesulfonate anion by the presence of urea.48 The peak at 1660 cm−1 on urea spectra corresponding to carbonyl group stretching vibrations was shifted to 1650 cm−1, displaying the weakening of the bond as well as the C−N bond shifted from 1452 cm−1 in urea to 1434 cm−1 in the DES. Other peaks in the spectra of DES have not changed substantially. According to the observed changes in IR spectra, the addition of urea leads to interaction between urea 1898



Article

Figure 3. 1H NMR spectra of the DES (1) and [bmim][MeSO3] (2).

Vm for a range of temperatures from 293.15 and 343.15 K are represented in Table 2.

hydrogens and methanesulfonate anion accompanied by the weakening of interactions between [bmim] and [MeSO3]. The additional information about the structure of the DES obtained by 1H NMR spectroscopy provides further evidence of the interaction between imidazolium salt and HBD. Pure [bmim][MeSO3] has the chemical shifts at 9.77, 7.42, and 7.32 ppm, which are assigned to C(2), C(4), and C(5) protons, respectively (Figure 3). With the addition of urea, the aforementioned peaks shift slightly downfield as well as the peaks at 4.01 and 2.74 ppm corresponding to the hydrogens in NCH2 and (SO3)CH3 groups which prove the formation of the hydrogen-bonded complex between urea and the IL.49 On the contrary, a slight shielding occurs for signals at 1.29−1.39, 0.91−0.96 ppm, associated with methyl groups in the butyl substituent of the imidazolium ring. Signals corresponding to other peaks have remained unchanged. 3.2. Thermophysical Properties. The thermophysical properties of DESs, such as density and viscosity, play a pivotal role in calculations of the thermodynamic properties and sorption capacity of absorbents. In particular, the density data allow analyzing the volumetric effect of mixing ammonium salt and HBD by considering the free volume Vfree.50 For this purpose, Florindo et al. suggested the determination of the free volume of DESs using the Lorenz−Lorenz equation,35 according to which the free volume can be calculated as follows: Vfree = Vm − R m

Table 2. Density, Molar Volume and Viscosity for the DES at Various Temperatures and Pressure P = 99.6 kPaa Vm/cm3/mol

η/mPa·s

293.15 303.15 313.15 323.15 333.15

1.2022 1.1956 1.1892 1.1827 1.1763

122.43 123.11 123.77 124.45 125.13

1892.9 686.69 295.72 145.85 80.406

The molar refraction Rm was found by the following expression using the refractive index measured at 293.15 K. Rm =

nD2 − 1 nD2 + 2

Vm

(4)

where nD and Vm are the refractive index (nD = 1.493 ± 0.001) and the molar volume of the DES, respectively. Since the calculated molar refraction was equal to 35.581 cm3/mol, the free volume of DES was found to be 86.85 cm3/mol. The density of the DESs decreases linearly with increasing temperature; therefore, the linear equation may be used to express the experimental data:

(1)

where Vm is the molar volume of the DES in cm /mol; Rm is the molar refraction of the DES in cm3/mol. The molar volume can be found using the density data represented in Table 1:

ρ = AT + B

(5)

where ρ corresponds to density in g/cm , T is the temperature in K, and A and B are the constants. The A and B values were equal to −0.0006 and 1.215, respectively, with a standard deviation of 0.0004. Viscosity as one of the important parameters in the study of liquids describes the intermolecular interactions between the molecules. In the case of DESs, the viscosity mainly depends on the strength of the hydrogen network, van der Waals 3

(2)

where Mr is the relative molar mass of the DES calculated from

M r = XaMa + XbMb

ρ/g/cm3

a Standard uncertainties u are u(T) = 0.03 K, u(P)= 0.5 kPa; the relative standard uncertainties Ur are Ur(ρ) = 0.1% and Ur(η) = 0.35%, which was calculated with a level of confidence of 0.95.

3

Vm = M r /ρ

T/K

(3)

where X is the mole fraction and M the relative molar mass of the two components a and b in g/mol. The calculated values of 1899



Article

interactions, and the presence of free volume in the liquid.51 The viscosity data measured between 293 and 343 K are listed in Table 1. Because of the linear correlation existing between the logarithm of viscosity and the temperature, the Arrhenius equation can be used as a fitting model:

η = η0 e E / RT

(6)

where η is the viscosity (mPa·s); E is the activation energy of viscous flow (kJ·mol−1); T is the temperature (K); R is the universal gas law constant (J·K−1·mol−1); η0 is the viscosity at the infinite temperature (mPa·s). E and η0 values were equal to 61.1 kJ/mol and 0.02 × 10−6 mPa·s, respectively, with correlation coefficient 0.9936. The prepared DES exhibits a relatively higher activation energy value than those typically found in deep eutectic solvents,35,51−53 probably, owing to the ability of [MeSO3] to form strong interactions (especially hydrogen bonds) with both urea and [bmim] cation. The lowest E values were reported for DESs consisting of choline chloride with glycerol,51 succinic acid, malonic acid, and oxalic acid35 in different ratios. The thermal properties of the absorbents such as glass transition temperature (Tg) and decomposition temperature determine the operating temperature range in which it is preferable to perform the capture of gases. The range of temperature at which the DES maintained its liquid state was investigated by EGA and DSC methods. The DSC thermogram is depicted in Figure 4 showing the glass transition temperature

Figure 5. Thermal degradation profiles of the DES observed by directEGA−MS.

Figure 6. Spectra of thermostimulated desorption (TSD) for H2S (m/ z 34), CO2 (m/z 44), and NH3 (m/z 16).

on the results of the TSD spectra (Table 2). The TSD signals attributed to ions of mass (m/z) 34, 44, 16 varied in intensity (Figure 6 and Table 3). The maximum desorption temperatures of gases from the DES corresponded to the range of temperatures from 356 to 360 K, revealing a low value of the binding energy of sorbate and the DES molecules. The significant feature of thermal desorption peaks is the significant difference in their shape observed when comparing high-temperature (HTA) and low-temperature areas (LTA) of the spectra. In the presently studied absorbents, the ratio of LTA (τ) and HTA (δ) half-widths was found to be 0.99 (NH3), 0.98 (H2S), and 1.70 (CO2). The shape of the desorption spectra is intrinsically linked to the desorption order56 and, therefore, may be used to clarify the order of reactions. A symmetric shape (τ ≈ δ) of a peak points to second-order reactions, whereas a peak of the first order is characterized by an asymmetric form (τ > δ). In the case of NH3 and H2S, the areas of the low- and high-temperature areas of the desorption peaks were almost identical (within RSD = 3%). The latter highlights the possibility of a second-order reaction for NH3 and H2S, in contrast to CO2, where the first order of reaction is realized. Since δ and Tmax were found from TSD spectra, the desorption activation energy Ed may be calculated by means of the Redhead equation:54

Figure 4. DSC thermogram of the DES with a 10 K/min temperatureramping rate.

of the eutectic solvent. We found that the glass transition, observed at 218 K, is substantially lower than the melting points of both raw materials (urea, 406 K; [bmim][MeSO3], 348 K). The relative expanded uncertainty Ur was Ur(Tg) = 4%, which was calculated with a level of confidence of 0.95. The decomposition temperature of the DES was determined using a temperature-programmed desorption (TPD) analysis and was found to be 378.15 K (Figure 5). The decomposition of the eutectic mixture was passed on through the stage corresponding to ammonium acetate formation evidenced by m/z 43, 60, and 97. The total dehydration (m/z 18) of the DES occurs in the temperature range 314.07−458.15 K. Estimating the activation energy of H2S, CO2, and NH3 desorption processes at different temperature conditions was conducted by means of decomposing the obtained spectra into the sum of the peaks described by the Gauss distribution.54 All peaks are in the temperature range of 310−420 K (Figure 6). The calculations corresponding to the reaction order and activation energies of the desorption process were made based

E = χRTmax 2/δ

(7)

where χ is the order of the reaction (1 or 2 for the first and second order reactions, respectively), Tmax is the temperature of the maximal TD signal, δ is the half-width of the desorption peak at half-height. The calculated activation energy of desorption Ed was 87.62 kJ/mol for NH3 and 78.59 for H2S. At the same time, the Ed 1900



Article

Table 3. Gases Desorption Energy from the DES compound

m/z

Tmax/K

τ LTA/K

δ HTA/K

χ

Ed/kJ/mol

NH3 H2S CO2

17 34 44

356.8 ± 0.1 357.3 ± 0.1 359.7 ± 0.1

23.89 ± 0.72 26.42 ± 0.79 31.58 ± 0.95

24.16 ± 0.73 27.01 ± 0.81 18.59 ± 0.56

2 2 1

87.62 ± 2.63 78.59 ± 2.36 57.86 1.74

Table 4. CO2, H2S, and NH3 Solubility mi (on Molality Scale) in the DESa T/K

P/bar

mCO2/(molCO2/kgDES)

P/bar

mH2S/(molH2S/kgDES)

P/bar

mNH3/(molNH3/kgDES)

303.2

2.847 4.237 5.450 6.984 3.124 4.369 5.826 7.292 3.291 4.559 5.995 7.392 3.434 4.777 6.103 7.661

0.161 0.245 0.321 0.422 0.170 0.243 0.332 0.425 0.171 0.241 0.324 0.407 0.168 0.237 0.309 0.396

2.633 3.941 5.330 6.450 2.806 4.046 5.476 6.567 2.969 4.205 5.634 6.675 3.157 4.359 5.834 6.806

0.436 0.645 0.862 1.034 0.438 0.625 0.836 0.994 0.442 0.620 0.823 0.967 0.460 0.629 0.834 0.966

1.236 2.112 2.914 4.326 1.726 2.456 3.494 5.258 2.318 2.750 4.156 5.976 3.010 3.612 4.708 6.589

0.894 1.650 2.458 4.256 1.049 1.565 2.395 4.150 1.129 1.366 2.211 3.507 1.144 1.400 1.895 2.843

313.2

323.2

333.2

a

Standard uncertainty u is u(T) = 0.01 K; the relative expanded uncertainty Ur is Ur(m) = 4%, which was calculated with a level of confidence of 0.95, the expanded uncertainty (k = 2) U is U(p) = 0.01 bar

Table 5. Thermodynamic Properties of Gases in the DES ΔsolG°/kJ·mol−1

H(0) 21.m/bar

ΔsolH°/kJ·mol−1

ΔsolS°/J·mol−1·K−1

T/K

CO2

H2S

NH3

CO2

H2S

NH3

CO2

H2S

NH3

CO2

H2S

NH3

303.2 313.2 323.2 333.2

16.32 16.92 17.85 19.11

5.93 6.30 6.61 6.72

1.52 1.82 2.27 2.89

7.04 7.36 7.74 8.17

1.06 4.79 5.07 5.28

1.06 1.56 2.20 2.93

−3.75 −4.18 −4.64 −5.14

−2.97 −3.47 −4.00 −4.59

−14.51 −16.84 −19.37 −22.12

−35.58 −36.86 −38.32 −39.94

−51.35 −26.36 −28.08 −29.60

−51.35 −58.75 −66.73 −75.19

law constants shown in Table 3 were obtained by extrapolating the present gas in ionic liquid solubility data:

energy for CO2 was found to be significantly lower than 57.86 kJ/mol. Consequently, desorption activation energy for the studied absorbates underscores the physical sorption of gases in the DES. 3.3. Gas Sorption Properties. Nowadays, intensive studies of eutectic solvents various applications, including gas separation processes are a top priority due to their promising gas solubility features, low synthesis cost, negligible toxicity, and high thermal and chemical stability. The majority of recent researches on gases solubility are mainly devoted to the capture of flue gases, containing CO2 and SO2. The literature data in this area have focused mostly on the systems that contain the choline chloride family, but there are also other DES types investigated as gas absorbents. The largest CO2 uptake was found to withhold by choline chloride mixed with glycerol in a molar ratio of 1:1.51 Other promising results have been observed with DESs prepared from the combination of choline chloride with urea31 and ethylene glycol.29 The results of CO2, H2S, and NH3 solubility measurements at the temperatures 303.2, 313.2, 323.2, and 333.2 K and pressures up to 7.28 bar are summarized in Tables 4 and 5. The reliability and accuracy of the measurement method have been checked using bmim[Tf2N],44,45 and the average reproducibility of the solubility data was well within ±1%. The Henry’s

⎡ f (T , P ) ⎤ ⎥ H(T ) = limP → 0⎢ i 0 ⎣ mi /m ⎦

(8)

where i is CO2, H2S of NH3 index, f i(T,P) is the fugacity of i gas in the gas phase, mi is the solubility of i gas in the IL (on molality scale), and mo is the reference solubility (1 mol/kg). The Henry’s Law constant at the ambient temperature was the parameter characterizing the absorption capacity. NH3 and H2S solubilities in the DES were found to be relatively high, their Henry’s law constants at 303.2 K in absorbent has achieved 1.52 and 5.93 bar, respectively. The DES exhibited lower affinity toward CO2 with a solubility value around 16.32 bar. Most probably, this observation can be explained by the formation of hydrogen bonding between H2S or NH3 with the DES components, while the CO2 is incapable of such interaction. Within the studied temperature region, the solubility practically linearly increases with the increase of pressure at a given temperature. This is clearly a physical solubility behavior in accordance with literature observations, which does not exclude hydrogen bonding. On the other hand, the solubility of gases in the DES clearly decreases with rising temperature. 1901



Article

particular, we’ve obtained eutectic solvents based on [bmim][MeSO3] with acidic HBDs, namely oxalic acid, fumaric acid, and maleic acid. But the present work demonstrates the possibility to form deep eutectic solvents with an unconventional hydrogen-bond acceptor (methanesulfonate-anion instead of chloride-anion) with acceptable ammonia sorption properties.

Subsequently, the changes of Gibbs free energy and entropy of gases absorption in the DES at different temperatures could be calculated from the following equations. Thermodynamic properties of solution (in absorbents) were obtained from the correlation of Henry’s constant given above by the application of well-known thermodynamic relations:55−57 Δsol G = RT ln(H21, m(T , p)/p°)

(9)

⎛ ∂ ln(H21, m(T , p)/p°) ⎞ ⎟ Δsol H = R ⎜ ∂(1/T ) ⎠p ⎝

(10)

Δsol S = (Δsol H − Δsol G)/T

(11)

4. CONCLUSIONS In the present work, a deep eutectic solvent was prepared through the interaction of an IL, 1-butyl-3-methyl imidazolium methanesulfonate, and a hydrogen-bond donor, namely urea, at a molar ratio 1:1. The FTIR and NMR studies have evidenced the formation of a hydrogen-bonded complex between urea and the IL and demonstrated that the C(2)-H bond makes a major contribution to hydrogen bonding. Physical properties (density, viscosity) were investigated in the temperature range of 293.15 to 333.15 K. The melting point and the decomposition temperature were determined. The activation energy of desorption obtained by the thermal desorption technique pointed to the physical sorption of ammonia, hydrogen sulfide, and carbon dioxide in the DES. The thermostimulated desorption spectra demonstrated that the ability of gases to bind with DES molecules can be ranked as follows: NH3 > H2S > CO2. The results of gas sorption show that the highest sorption capacity was observed with ammonia which exhibited Henry law constant equal to 1.52 bar. The comparison between the sorption properties of the DES synthesized and literature data reveals acceptable ammonia sorption properties of the DES. In the case of acidic gases, a poorer CO2 absorption capacity in the DES was observed in comparaison to H2S, which is capable of hydrogen bonding. In view of possible applications, the methanesulfonate-based DESs may be proposed as recyclable absorbents for NH3 removal from industrial gas streams, for biogas upgrading purposes, and in absorption refrigeration cycles, as well as for the fields of application, which are known for [MeSO3]-based ILs.

where ΔsolG, ΔsolH and ΔsolS are Gibbs free energy of solvation, enthalpy of solvation, and entropy of solvation, respectively. Thereby, the thermodynamic properties of CO2, H2S, and NH3 in the studied absorbents calculated at standard condition (p° = 1 bar) and ambient temperature (T° = 298.15 K), are presented in Table 4. The ΔsolH and ΔsolS values are negative for all absorbents at any temperature. The temperature increase is accompanied by the diminishing of those thermodynamic parameters. The DES + H2S and DES + NH3 systems were found to have similar values of ΔsolS (−51.35 J·mol−1·K−1), although the absorption of NH3 and H2S were somewhat higher than that observed for CO2 (H(0) 21.m = 1.52 and 5.39 vs 16.32 bar at 303.2 K, respectively). Since a more negative ΔsolH value leads to lower ΔsolG in the absorption, the dissolution of NH3 and H2S in the DES is thermodynamically more favorable than that of CO2. Interestingly, the results of gas sorption measurements are in a good agreement with thermal desorption data. In particular, according to thermostimulated desorption spectra, the ability of gases to bind with the DES molecules can be ranked as follows: NH3 > H2S > CO2. The gas solubility measurements revealed this observation. The gases separation selectivity was found as a ratio of Henry’s law constants and was equal to 10.7 and 3.9 bar for CO2/NH3 and H2S/NH3, respectively. Throughout the literature, the molecular simulations and the experimental measurements have revealed the formation of hydrogen bonds between the imidazolium cation and ammonia.55 Therefore, in order to enhance the solubility of ammonia in ILs, it is favorable to introduce additional hydrogen-bond donor groups. This assumption was explored in the work of Li et al., where authors systematically investigated NH3 absorption capacities of hydroxyl-functionalized ILs.39 We compared the Henry’s constants observed in their work39 with our experimental results and found that, among all the task-specific ILs, [EtOHmim][Tf2N] exhibited the lowest Henry’s constant and, consequently, was characterized by the largest absorption capacity. The values of ammonia solubility in the DES exceeded the corresponding values in [EtOHmim][Tf2N] by nearly 3.5 times. However, and up to date, the top-performing hybrid DES for ammonia capture was based on the choline chloride/resorcinol/glycerol eutectic mixture (ChCl/Res/Gly).38 In the most recent work, 1-butylimidazolium bis(trifluoromethylsulfonyl)imide was reported to show a NH3 mass solubility close to ChCl/Res/Gly, due to the presence of the acidic N−H group.37 Nevertheless, the [bmim][MeSO3] forming eutectic solvents with various HBDs, including carboxylic acids, phenols or glycols, may be tuned in order to acquire higher affinity to ammonia than the studied DES. In

■

AUTHOR INFORMATION

Corresponding Author

*Tel.:+7 831 4-360-361. +7 920 060 90 30. E-mail: [email protected]. ORCID

Alexander V. Nyuchev: 0000-0002-0460-0543 Ilya V. Vorotyntsev: 0000-0003-2282-0811 Funding

This work was supported by the Russian Science Foundation (Grant No. 17-79-20286) in a case of NH3 research and development; by the Grant of the President of the Russian Federation for early stage researchers (MD-4990.2018.3) in a case of H2S research and development. Part of the CO2 sorption study was supported by PhosAgro/UNESCO/ IUPAC (Grant “Green Chemistry for Life-2016”). Notes

The authors declare no competing financial interest.

■

REFERENCES

(1) Khandelwal, S.; Tailor, Y. K.; Kumar, M. Deep eutectic solvents (DESs) as eco-friendly and sustainable solvent/catalyst systems in organic transformations. J. Mol. Liq. 2016, 215, 345−386.

1902



Article

(2) Liu, P.; Hao, J.; Mo, L.; Zhang, Z. Recent advances in the application of deep eutectic solvents as sustainable media as well as catalysts in organic reactions. RSC Adv. 2015, 5, 48675−48704. (3) Paiva, A.; Craveiro, R.; Aroso, I.; Martins, M.; Reis, R. L.; Duarte, A. R. C. Natural Deep Eutectic Solvents − Solvents for the 21st Century. ACS Sustainable Chem. Eng. 2014, 2, 1063−1071. (4) Nkuku, C. A.; LeSuer, R. J. Electrochemistry in Deep Eutectic Solvents. J. Phys. Chem. B 2007, 111, 13271−13277. (5) Abbott, A. P.; Barron, J. C.; Frisch, G.; Ryder, K. S.; Silva, A. F. The effect of additives on zinc electrodeposition from deep eutectic solvents. Electrochim. Acta 2011, 56, 5272−5279. (6) Smith, E. L.; Abbott, A. P.; Ryder, K. S. Deep Eutectic Solvents (DESs) and Their Applications. Chem. Rev. (Washington, DC, U. S.) 2014, 114, 11060−11082. (7) Neves, C. M. S. S.; Batista, M. L. S.; Cláudio, A. F. M.; Santos, L.M.N.B.F.; Marrucho, I. M.; Freire, M. G.; Coutinho, J. A. P. Thermophysical Properties and Water Saturation of [PF6]−Based Ionic Liquids. J. Chem. Eng. Data 2010, 55, 5065−5073. (8) Gouveia, A. S. L.; Tomé, L. C.; Marrucho, I. M. Density, Viscosity, and Refractive Index of Ionic Liquid Mixtures Containing Cyano and Amino Acid-Based Anions. J. Chem. Eng. Data 2016, 61, 83−93. (9) Uma Maheswari, A.; Palanivelu, K. Carbon Dioxide Capture and Utilization by Alkanolamines in Deep Eutectic Solvent Medium. Ind. Eng. Chem. Res. 2015, 54, 11383−11392. (10) Ruckart, K. N.; Zhang, Y.; Reichert, W. M.; Peterson, G. W.; Glover, T. G. Sorption of Ammonia in Mesoporous-Silica Ionic Liquid Composites. Ind. Eng. Chem. Res. 2016, 55, 12191−12204. (11) Verevkin, S. P.; Sazonova, A.Yu.; Frolkova, A. K.; Zaitsau, D. H.; Prikhodko, I. V.; Held, C. Separation Performance of BioRenewable Deep Eutectic Solvents. Ind. Eng. Chem. Res. 2015, 54, 3498−3504. (12) García, G.; Aparicio, S.; Ullah, R.; Atilhan, M. Deep Eutectic Solvents: Physicochemical Properties and Gas Separation Applications. Energy Fuels 2015, 29, 2616−2644. (13) McDanel, W. M.; Cowan, M. G.; Barton, J. A.; Gin, D. L.; Noble, R. D. Effect of Monomer Structure on Curing Behavior, CO2 Solubility and Gas Permeability of Ionic Liquid-Based Epoxy−Amine Resins and Ion-Gels. Ind. Eng. Chem. Res. 2015, 54, 4396−4406. (14) Abdelrahim, M. Y. M.; Martins, C. F.; Neves, L. A.; Capasso, C.; Supuran, C. T.; Coelhoso, I. M.; Crespo, J. G.; Barboiu, M. Supported ionic liquid membranes immobilized with carbonic anhydrases for CO2 transport at high temperatures. J. Membr. Sci. 2017, 528, 225− 230. (15) Zhang, Q.; Vigier, K. D. O.; Royer, S.; Jérôme, F. Deep eutectic solvents: syntheses, properties and applications. Chem. Soc. Rev. 2012, 41, 7108−7146. (16) Uzagare, M. C.; Sanghvi, Y. S.; Salunkhe, M. M. Application of ionic liquid 1-methoxyethyl-3-methyl imidazolium methanesulfonate in nucleoside chemistry. Green Chem. 2003, 5, 370−372. (17) Golding, J.; Forsyth, S.; MacFarlane, D. R.; Forsyth, M.; Deacon, G. B. Methanesulfonate and p-toluenesulfonate salts of the Nmethyl-N-alkylpyrrolidinium and quaternary ammonium cations: novel low cost ionic liquids. Green Chem. 2002, 4, 223−229. (18) Brinchi, L.; Germani, R.; Savelli, G. Ionic liquids as reaction media for esterification of carboxylate sodium salts with alkyl halides. Tetrahedron Lett. 2003, 44, 2027−2029. (19) Sun, J. Lithium polyelectrolyte−ionic liquid systems. Solid State Ionics 2002, 147, 333−339. (20) Poole, C. F.; Poole, S. K. Ionic liquid stationary phases for gas chromatography. J. Sep. Sci. 2011, 34, 888−900. (21) Ventura, S. P. M.; Neves, C. M. S. S.; Freire, M. G.; Marrucho, I. M.; Oliveira, J.; Coutinho, J. A. P. Evaluation of Anion Influence on the Formation and Extraction Capacity of Ionic-Liquid-Based Aqueous Biphasic Systems. J. Phys. Chem. B 2009, 113, 9304−9310. (22) Lee, K. Y.; Gong, G. T.; Song, K. H.; Kim, H.; Jung, K. D.; Kim, C. S. Use of ionic liquids as absorbents to separate SO2 in SO2/O2 in thermochemical processes to produce hydrogen. Int. J. Hydrogen Energy 2008, 33, 6031−6036.

(23) Jung, Y. H.; Jung, J. Y.; Jin, Y. R.; Lee, B. C.; Baek, I. H.; Kim, S. H. Solubility of Carbon Dioxide in Imidazolium-Based Ionic Liquids with a Methanesulfonate Anion. J. Chem. Eng. Data 2012, 57, 3321− 3329. (24) Jin, Y. R.; Jung, Y. H.; Park, S. J.; Baek, I. H. Study of CO2 Absorption Characteristic and Synthesis of 1-(2-methoxyethyl)-3methylimidazoLium Methanesulfonate Ionic Liquid. Hwahak Konghak 2012, 50, 35−40. (25) Reiss, G. J.; Meyer, M. K. Diisopropylammonium methanesulfonate. Acta Crystallogr., Sect. E: Struct. Rep. Online 2011, 67, 2169− 2169. (26) Luo, J.; Tan, T. V.; Conrad, O.; Vankelecom, I. F. J. 1H-1,2,4Triazole as solvent for imidazolium methanesulfonate. Phys. Chem. Chem. Phys. 2012, 14, 11441−11447. (27) De Santi, V.; Cardellini, F.; Brinchi, L.; Germani, R. Novel Brønsted acidic deep eutectic solvent as reaction media for esterification of carboxylic acid with alcohols. Tetrahedron Lett. 2012, 53, 5151−5155. (28) Pike, S. J.; Hutchinson, J. J.; Hunter, C. A. H-Bond Acceptor Parameters for Anions. J. Am. Chem. Soc. 2017, 139, 6700−6706. (29) Leron, R. B.; Li, M. H. Solubility of carbon dioxide in a choline chloride−ethylene glycol based deep eutectic solvent. Thermochim. Acta 2013, 551, 14−19. (30) Leron, R. B.; Caparang, A.; Li, M. H. Carbon dioxide solubility in a deep eutectic solvent based on choline chloride and urea at T = 303.15−343.15 K and moderate pressures. J. Taiwan Inst. Chem. Eng. 2013, 44, 879−885. (31) Li, X.; Hou, M.; Han, B.; Wang, X.; Zou, L. Solubility of CO2 in a Choline Chloride + Urea Eutectic Mixture. J. Chem. Eng. Data 2008, 53, 548−550. (32) Su, W. C.; Wong, D. S. H.; Li, M. H. Effect of Water on Solubility of Carbon Dioxide in (Aminomethanamide + 2-HydroxyN,N,N-trimethylethanaminium Chloride). J. Chem. Eng. Data 2009, 54, 1951−1955. (33) Li, G.; Deng, D.; Chen, Y.; Shan, H.; Ai, N. Solubilities and thermodynamic properties of CO2 in choline-chloride based deep eutectic solvents. J. Chem. Thermodyn. 2014, 75, 58−62. (34) Bazhenov, S.; Ramdin, M.; Volkov, A.; Volkov, V.; Vlugt, T. J. H.; De Loos, T. W. CO2 Solubility in Biodegradable Hydroxylammonium-Based Ionic Liquids. J. Chem. Eng. Data 2014, 59, 702−708. (35) Florindo, C.; Oliveira, F. S.; Rebelo, L. P. N.; Fernandes, A. M.; Marrucho, I. M. Insights into the Synthesis and Properties of Deep Eutectic Solvents Based on Cholinium Chloride and Carboxylic Acids. ACS Sustainable Chem. Eng. 2014, 2, 2416−2425. (36) Zhang, Q.; Vigier, K. De O.; Royer, S.; Jérôme, F. Deep eutectic solvents: syntheses, properties and applications. Chem. Soc. Rev. 2012, 41, 7108. (37) Shang, D.; Zhang, X.; Zeng, S.; Jiang, K.; Gao, H.; Dong, H.; Yang, Q.; Zhang, S. Protic ionic liquid [Bim][NTf2] with strong hydrogen bond donating ability for highly efficient ammonia absorption. Green Chem. 2017, 19, 937−945. (38) Li, Y.; Ali, M. C.; Yang, Q.; Zhang, Z.; Bao, Z.; Su, B.; Xing, H.; Ren, Q. Hybrid Deep Eutectic Solvents with Flexible HydrogenBonded Supramolecular Networks for Highly Efficient Uptake of NH3. ChemSusChem 2017, 10, 3268−3377. (39) Li, Z.; Zhang, X.; Dong, H.; Zhang, X.; Gao, H.; Zhang, S.; Li, J.; Wang, C. Efficient absorption of ammonia with hydroxyl-functionalized ionic liquids. RSC Adv. 2015, 5, 81362−81370. (40) Davletbaeva, I. M.; Nurgaliyeva, G. R.; Akhmetshina, A. I.; Davletbaev, R. S.; Atlaskin, A. A.; Sazanova, T. S.; Efimov, S. V.; Klochkov, V. V.; Vorotyntsev, I. V. Porous polyurethanes based on hyperbranched amino ethers of boric acid. RSC Adv. 2016, 6, 111109− 111119. (41) Davletbaeva, I. M.; Emelina, O.Yu.; Vorotyntsev, I. V.; Davletbaev, R. S.; Grebennikova, E. S.; Petukhov, A. N.; Akhmetshina, A. I.; Sazanova, T. S.; Loskutov, V. V. Synthesis and properties of novel polyurethanes based on amino ethers of boric acid for gas separation membranes. RSC Adv. 2015, 5, 65674−65683. 1903



Article

(42) Akhmetshina, A.; Davletbaeva, I.; Grebenschikova, E.; Sazanova, T.; Petukhov, A.; Atlaskin, A.; Razov, E.; Zaripov, I.; Martins, C.; Neves, L.; Vorotyntsev, I. The Effect of Microporous Polymeric Support Modification on Surface and Gas Transport Properties of Supported Ionic Liquid Membranes. Membranes 2016, 6, 4−8. (43) Akhmetshina, A. I.; Gumerova, O. R.; Atlaskin, A. A.; Petukhov, A. N.; Sazanova, T. S.; Yanbikov, N. R.; Nyuchev, A. V.; Razov, E. N.; Vorotyntsev, I. V. Permeability and selectivity of acid gases in supported conventional and novel imidazolium-based ionic liquid membranes. Sep. Purif. Technol. 2017, 176, 92−106. (44) Jacquemin, J.; Husson, P.; Majer, V.; Gomes, M. F. C. Lowpressure solubilities and thermodynamics of solvation of eight gases in 1-butyl-3-methylimidazolium hexafluorophosphate. Fluid Phase Equilib. 2006, 240, 87−95. (45) Jacquemin, J.; Gomes, M. F. C.; Husson, P.; Majer, V. Solubility of carbon dioxide, ethane, methane, oxygen, nitrogen, hydrogen, argon, and carbon monoxide in 1-butyl-3-methylimidazolium tetrafluoroborate between temperatures 283K and 343K and at pressures close to atmospheric. J. Chem. Thermodyn. 2006, 38, 490−502. (46) Akhmetshina, A.; Petukhov, A.; Vorotyntsev, A.; Nyuchev, A.; Vorotyntsev, I. Absorption Behavior of Acid Gases in Protic Ionic Liquid/Alkanolamine Binary Mixtures. ACS Sustainable Chem. Eng. 2017, 5, 3429−3437. (47) Zakzeski, J.; Bruijnincx, P. C. A.; Weckhuysen, B. M. In situ spectroscopic investigation of the cobalt-catalyzed oxidation of lignin model compounds in ionic liquids. Green Chem. 2011, 13, 671−680. (48) Hong, S. Y.; Im, J.; Palgunadi, J.; Lee, S. D.; Lee, J. S.; Kim, H. S.; Cheong, M.; Jung, K. D. Ether-functionalized ionic liquids as highly efficient SO2 absorbents. Energy Environ. Sci. 2011, 4, 1802. (49) Cao, L.; Huang, J.; Zhang, X.; Zhang, S.; Gao, J.; Zeng, S. Imidazole tailored deep eutectic solvents for CO2 capture enhanced by hydrogen bonds. Phys. Chem. Chem. Phys. 2015, 17, 27306−27316. (50) Jansen, J. C.; Clarizia, G.; Bernardo, P.; Bazzarelli, F.; Friess, K.; Randova, A.; Schauer, J.; Kubicka, D.; Kacirkova, M.; Izak, P. Gas transport properties and pervaporation performance of fluoropolymer gel membranes based on pure and mixed ionic liquids. Sep. Purif. Technol. 2013, 109, 87−97. (51) Abbott, A. P.; Harris, R. C.; Ryder, K. S.; D’Agostino, C.; Gladden, L. F.; Mantle, M. D. Glycerol eutectics as sustainable solvent systems. Green Chem. 2011, 13, 82−90. (52) Karaszova, M.; Simcik, M.; Friess, K.; Randova, A.; Jansen, J. C.; Ruzicka, M.; Sedlakova, Z.; Izak, P. Comparison of theoretical and experimental mass transfer coefficients of gases in supported ionic liquid membranes. Sep. Purif. Technol. 2013, 118, 255−263. (53) Yadav, A.; Pandey, S. Densities and Viscosities of (Choline Chloride + Urea) Deep Eutectic Solvent and Its Aqueous Mixtures in the Temperature Range 293.15 to 363.15 K. J. Chem. Eng. Data 2014, 59, 2221−2229. (54) Woodruff, D. P.; Delchar, T. A. Modern Techniques of Surface Science; Cambridge University Press: Cambridge, 1994. (55) Akhmetshina, A. I.; Petukhov, A. N.; Vorotyntsev, A. V.; Nyuchev, A. V.; Vorotyntsev, I. V. Absorption Behavior of Acid Gases in Protic Ionic Liquid/Alkanolamine Binary Mixtures. ACS Sustainable Chem. Eng. 2017, 5, 3429−3437. (56) Vorotyntsev, I. V.; Drozdov, P. N.; Mochalov, G. M.; Smirnova, N. N.; Suvorov, S. S. Sorption of ammonia and nitrogen on cellulose acetate. Russian Journal of Physical Chemistry A 2006, 80 (12), 2020− 2023. (57) Shi, W.; Maginn, E. J. Molecular simulation of ammonia absorption in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]). AIChE J. 2009, 55, 2414−242.

1904


Evaluation of Methanesulfonate-Based Deep ... - ACS Publications

Recommend Documents