Volumetric Properties of 1-Butyl-3-methylimidazolium Chloride with

Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX-XXX

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Volumetric Properties of 1‑Butyl-3-methylimidazolium Chloride with Organic Solvents Fuxin Yang, Dongbo Wang, Xiaopo Wang,* and Zhigang Liu Key Laboratory of Thermo-Fluid Science and Engineering, Ministry of Education, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China ABSTRACT: Ionic liquids are considered green solvents and widely investigated. 1-Butyl-3-methylimidazolium chloride shows promise for making biofuels from biomass. In this work, the experimental densities of the binary mixtures, comprising ionic liquids of 1-butyl-3-methylimidazolium chloride and organic solvents (i.e., N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, and pyridine), are determined at atmospheric pressure (0.0967 MPa) from 303.15 to 353.15 K. The excess molar volumes are determined to understand the interaction between ionic liquid and organic solvents, and a Redlich−Kister type equation is used to describe the excess properties. Moreover, the derived volumetric properties of thermal expansion coefficients are calculated as well as the excess coefficients.

1. INTRODUCTION Ionic liquids (ILs) have been considered green solvents and show great promising for a large number of chemical and biochemical applications. ILs are defined as salts and present unique characteristics by the simple combination of the available inorganic or organic cations and organic anions, and that makes ILs more designable and tunable for special processes to meet target properties, e.g., low vapor pressure and volatility, high chemical and thermal stability, and large liquidus range, in contrast to the conventional compounds.1 Rogers et al. presented the results that chloride-based ILs can dissolve cellulose, one of the components of the biomass, and more studies are then focusing on the study of ILs for renewable energy.2 However, the chloride-based ILs are viscous and are not convenient for applications. Prausnitz et al. reported that the high viscosity would hinder the dissolution of biomass for making biofuels.3 Gericke et al. systematically researched 18 organic solvents on the effects of cellulose solutions; in these organic solvents, N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and pyridine (PYR) show great potential for lowing the viscosity of ILs and improving the dissolution of biomass.4 More studies are focusing on the mechanism of producing biofuels from biomass using IL with organic solvents, while a little attention has given to the research on the thermophysical properties of these binary mixtures.5−7 Govinda et al. studied the density on the binary system of IL with DMSO from 298.15 to 328.15 K.8 Yan et al. and Yang et al. reported the density for the mixture of IL with DMF from 288.15 to 318.15 K.5,9,10 The knowledge of the fundamental thermophysical properties plays an essential role in industrial design and scale-up processes as well as the scientific research. Furthermore, it provides further insight on the relationship between the ions and the measured properties © XXXX American Chemical Society

and on the understanding of the molecular interactions in samples.11,12 In this work, the densities of a chloride-based IL, 1-butyl-3methylimidazolium chloride ([C4mim][Cl]), with organic solvents of DMA, DMF, DMSO, and PYR are measured from 303.15 to 353.15 K at atmospheric pressure (0.0967 MPa). The excess properties are obtained to comprehend the interaction in the binary mixtures. Moreover, the thermal expansion coefficients as well as the excess coefficients are calculated.

2. EXPERIMENTAL SECTION 2.1. Materials. The details of the organic solvents and IL studied in this work are described in Table 1. The organic solvents were obtained from Sigma-Aldrich (St. Louis, MO) and were used without further purification. IL of 1-butyl-3-methylimidazolium chloride ([C4mim][Cl]) was purchased from the Center for Green Chemistry and Catalysis (CGCC), Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences (CAS). 2.2. Procedure. In order to reduce the effect of water and volatile substance on thermophysical properties of the IL, the 3A molecular sieves (Sigma-Aldrich, St. Louis, MO) were applied to dry the IL. Before the use of 3A, acetone and methanol solution were used to clean the 3A sieves, and they were then stable in a furnace with a preset temperature of 473.15 K for overnight. A small amount of IL with the sieves was dried in a furnace with the temperature of 353.15 K at the pressure of 2 ± 0.1 kPa for more than 24 h.13 The binary mixtures were determined by an analytical balance (Mettler-Toledo, AB204-N and ME204) with the uncertainty Received: July 17, 2017 Accepted: September 29, 2017

A

DOI: 10.1021/acs.jced.7b00654 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. Descriptions of the Substances Studied in This Work substance

abbreviation

CAS no.

source

initial mass fraction purity

purification method

1-butyl-3-methylimidazolium chloride N,N-dimethylacetamide N,N-dimethylformamide dimethyl sulfoxide pyridine

[C4mim][Cl] DMA DMF DMSO PYR

171058-17-6 127-19-5 68-12-2 67-68-5 110-86-1

Chinese Academy of Sciences Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich

≥0.98 ≥0.98 ≥0.99 ≥0.99 ≥0.998

drying none none none none

where ρ (g·cm−3) is the density; parameters of a0 (g·cm−3), a1 (g·cm−3·K−1), and a2 (g·cm−3·K−2) are fitted by the experimental data in this work; and T (K) is the temperature. The average absolute relative deviation (AARD) is calculated by

of 0.0001 g. The water contents in the pure IL and binary solutions were detected by a Karl Fischer moisture titrator (Coulometric titration, MKC-710B, Kyoto Electronics Manufacturing Co., Ltd.) before and after the density measurements. The water contents in the samples before and after the measurements were under 3000 ppm; specifically, the content for the IL is 2532 ppm, which is specified as less than 5000 ppm provided by the manufacture. 2.3. Density Measurements. The experimental densities of pure substances and binary mixtures were measured using an Anton Paar DMA 5000 M digital vibrating U-tube densimeter with the temperature ranges from 303.15 to 353.15 K at atmospheric pressure (0.0967 MPa). The temperature in the U-tube cell was controlled and determined by the two integrated platinum thermometers with an uncertainty of 0.001 K. The repeatability of the U-tube densimeter provided by the manufacturer was specified as 1.0 × 10−6 g·cm−3. Considering the purity and preparation procedure, the relative standard uncertainty of the density was 0.001. The densimeter cell was cleaned and washed using water and acetone/methanol before and after the measurements. The densimeter was then calibrated regularly using the bidistilled water and dry air. During the measurements, the densities were determined in triplicate.

AARD (%) =

N

∑

(ρlit, i − ρcal, i ) ρlit, i

i=1

(2)

where N is the number of experimental points and ρlit and ρcal are the literature and calculated data by eq 1, respectively. The AARD for the pure IL between the literature data and the values calculated by eq 1 is 0.17%. The densities measured in this work agree well with those in the literature. However, the AARD from Govinda et al.8 is 0.80%, and that from Kavitha et al.14 is 0.77%. More literature data should be needed to discuss the differences. The experimental densities as well as the fitted data by eq 1 are also presented in Figures 2-5. 3.2. Effects of Organic Solvents on the Thermophysical Properties of the IL. To study the effects of organic solvents on the volumetric properties of the IL, the excess molar volume is introduced, and it is calculated by V E = Vm −

3. RESULTS AND DISCUSSION 3.1. Experimental Density Data. The experimental densities of pure substances and binary mixtures at atmospheric pressure from 303.15 to 353.15 K are tabulated in Tables 2-5. The densities of these four pure solvents have been reported in the previous publication.13 Figure 1 presents the relative deviation between the literature densities of pure IL and the calculated data using the following equation fitted by the measured values in this work: ρ = a0 + a1·T + a 2 ·T 2

100 N

∑ xiVi =

∑ xiMi − ρm

∑

xiMi ρi

(3)

where VE (cm3·mol−1) is the excess molar volume; Vm (cm3·mol−1), ρm (g·cm−3), and Mm (g·mol−1) are the molar volume, the density, and the molar mass of the binary mixture, respectively; xi, Vi, Mi, and ρi are the mole fraction, molar volume, molar mass and density of pure component i, respectively. ρm = Mm/Vm =

∑ xiMi /Vm

(4) E

In Figures 6−9, the excess molar volume V as a function of IL mole fraction is depicted. The excess molar volumes are negative, indicating that there is a volume contraction

(1)

Table 2. Experimental Densities of [C4mim][Cl] with DMA at (0.0967± 0.002) MPa x [C4mim][Cl] + (1 − x) DMA, ρ (g·cm−3) x

a

a

T (K)

0.000

303.15 308.15 313.15 318.15 323.15 328.15 333.15 338.15 343.15 348.15 353.15

0.93185 0.92726 0.92266 0.91806 0.91344 0.90881 0.90416 0.89953 0.89487 0.89019 0.88551

0.177

0.332

0.428

0.538

0.664

0.816

0.904

1.000

0.98028 0.97620 0.97220 0.96823 0.96427 0.96032 0.95638 0.95245 0.94853 0.94461 0.94067

1.01024 1.00661 1.00298 0.99936 0.99575 0.99215 0.98855 0.98497 0.98138 0.97780 0.97422

1.02506 1.02160 1.01815 1.01471 1.01128 1.00786 1.00446 1.00106 0.99767 0.99429 0.99092

1.03852 1.03510 1.03170 1.02835 1.02485 1.02156 1.01833 1.01516 1.01207 1.00903 1.00606

1.05240 1.04919 1.04595 1.04278 1.03956 1.03644 1.03337 1.03034 1.02737 1.02445 1.02159

1.06629 1.06328 1.06020 1.05721 1.05427 1.05133 1.04841 1.04552 1.04267 1.03987 1.03713

1.07317 1.07028 1.06741 1.06454 1.06166 1.05885 1.05606 1.05326 1.05047 1.04769 1.04491

1.07941 1.07658 1.07378 1.07099 1.06819 1.06536 1.06260 1.05987 1.05715 1.05442 1.05169

Published in ref 13. The standard uncertainties (u) are u(x) = 2.0 × 10−4, u(T) = 0.01 K, and ur(ρ) = 0.001. B



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Table 3. Experimental Densities of [C4im][Cl] with DMF at (0.0967± 0.002) MPa x [C4mim][Cl] + (1 − x) DMF, ρ (g·cm−3) x

a

a

T (K)

0.000

303.15 308.15 313.15 318.15 323.15 328.15 333.15 338.15 343.15 348.15 353.15

0.93918 0.93441 0.92964 0.92486 0.92007 0.91526 0.91044 0.90560 0.90074 0.89587 0.89098

0.151

0.295

0.385

0.493

0.626

0.790

0.887

1.000

0.98764 0.98355 0.97945 0.97535 0.97126 0.96716 0.96307 0.95897 0.95487 0.95078 0.94668

1.01634 1.01263 1.00893 1.00524 1.00156 0.99789 0.99421 0.99055 0.98689 0.98324 0.97959

1.03008 1.02656 1.02305 1.01954 1.01605 1.01257 1.00910 1.00566 1.00224 0.99882 0.99540

1.04312 1.03978 1.03646 1.03315 1.02985 1.02656 1.02329 1.02003 1.01678 1.01355 1.01033

1.05589 1.05275 1.04960 1.04660 1.04335 1.04024 1.03716 1.03408 1.03103 1.02798 1.02494

1.06773 1.06472 1.06175 1.05883 1.05591 1.05299 1.05007 1.04716 1.04426 1.04139 1.03853

1.07265 1.06974 1.06684 1.06395 1.06097 1.05813 1.05531 1.05248 1.04967 1.04688 1.04411

1.07941 1.07658 1.07378 1.07099 1.06819 1.06536 1.06260 1.05987 1.05715 1.05442 1.05169

Published in ref 13. The standard uncertainties (u) are u(x) = 2.0 × 10−4, u(T) = 0.01 K, and ur(ρ) = 0.001.

Table 4. Experimental Densities of [C4im][Cl] with DMSO at (0.0967± 0.002) MPa x [C4mim][Cl] + (1 − x) DMSO, ρ (g·cm−3) x

a

T (K)

0.000a

0.161

0.309

0.401

0.509

0.641

0.801

0.894

1.000

303.15 308.15 313.15 318.15 323.15 328.15 333.15 338.15 343.15 348.15 353.15

1.09029 1.08528 1.08030 1.07531 1.07032 1.06533 1.06034 1.05534 1.05035 1.04534 1.04033

1.09042 1.08685 1.08314 1.07958 1.07576 1.07219 1.06887 1.06513 1.06144 1.05769 1.05372

1.09372 1.08998 1.08625 1.08254 1.07883 1.07514 1.07145 1.06776 1.06410 1.06044 1.05679

1.09213 1.08858 1.08504 1.08151 1.07800 1.07450 1.07101 1.06754 1.06407 1.06063 1.05719

1.08944 1.08609 1.08274 1.07935 1.07605 1.07270 1.06947 1.06613 1.06288 1.05965 1.05642

1.08622 1.08296 1.07973 1.07652 1.07333 1.07018 1.06709 1.06406 1.06111 1.05817 1.05525

1.08366 1.08069 1.07769 1.07471 1.07178 1.06887 1.06595 1.06304 1.06014 1.05725 1.05438

1.08172 1.07888 1.07599 1.07312 1.07022 1.06739 1.06459 1.06179 1.05899 1.05619 1.05341

1.07941 1.07658 1.07378 1.07099 1.06819 1.06536 1.06260 1.05987 1.05715 1.05442 1.05169


Table 5. Experimental Densities of [C4im][Cl] with PYR at (0.0967± 0.002) MPa x [C4im][Cl] + (1 − x) PYR, ρ (g·cm−3) x

a

a

T (K)

0.000

303.15 308.15 313.15 318.15 323.15 328.15 333.15 338.15 343.15 348.15 353.15

0.97309 0.96806 0.96302 0.95797 0.95290 0.94782 0.94272 0.93760 0.93246 0.92730 0.92212

0.163

0.313

0.404

0.514

0.644

0.803

0.895

1.000

1.01320 1.00909 1.00497 1.00085 0.99673 0.99260 0.98847 0.98434 0.98021 0.97606 0.97191

1.03567 1.03205 1.02843 1.02482 1.02121 1.01760 1.01400 1.01040 1.00681 1.00322 0.99963

1.04560 1.04219 1.03878 1.03539 1.03201 1.02863 1.02525 1.02189 1.01853 1.01517 1.01179

1.05449 1.05120 1.04794 1.04472 1.04152 1.03833 1.03514 1.03193 1.02866 1.02527 1.02181

1.06334 1.06026 1.05718 1.05411 1.05104 1.04799 1.04496 1.04194 1.03893 1.03592 1.03289

1.07241 1.06951 1.06659 1.06366 1.06072 1.05781 1.05492 1.05208 1.04929 1.04657 1.04402

1.07589 1.07302 1.07016 1.06730 1.06445 1.06165 1.05886 1.05609 1.05331 1.05053 1.04777

1.07941 1.07658 1.07378 1.07099 1.06819 1.06536 1.06260 1.05987 1.05715 1.05442 1.05169


concerning the binary mixtures of IL with organic solvents. In these four binary mixtures, VE for the system of IL with PYR has the highest absolute value, while for the system of IL with DMSO, it has the lowest absolute value. The curves of the excess molar volumes are quite symmetric, and there are sharp changes in the solvent-rich range with a minimum when the mole fraction of IL occurs from 0.2 to 0.5. In the view of molecular insight,

DMA (CH3C(O)N(CH3)2) and DMF ((CH3)2NC(O)H) have similar structures. Therefore, they performed similar behaviors when they were mixed with IL. PYR is a heterocyclic organic solvent with the formula of C5H5N. DMSO is an organosulfur solvent with the formula of (CH3)2SO. In the binary mixtures of IL with these organic solvents, the new hydrogen bonding is preferred to be formed. C



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Figure 1. Relative deviations for pure IL densities between the literature values (ρlit) and the calculated data (ρcal) using eq 1 fitted with the experimental values in this work: ■, ref 8; □, ref 16; ●, ref 17; ○, ref 14; ▲, ref 18; △, ref 19; ▼, ref 20; ★, this work.

Figure 4. Densities of [C4mim][Cl] with organic solvent of DMSO as a function of temperature: ■, x = 0; □, x = 0.161; ●, x = 0.309; ○, x = 0.401; ▲, x = 0.509; △, x = 0.641; ▼, x = 0.801; ▽, x = 0.894; ◆, x = 1.000; solid line calculated by eq 1.

Figure 2. Densities of [C4mim][Cl] with organic solvent of DMA as a function of temperature: ■, x = 0; □, x = 0.177; ●, x = 0.332; ○, x = 0.428; ▲, x = 0.538; △, x = 0.664; ▼, x = 0.816; ▽, x = 0.904; ◆, x = 1.000; solid line calculated by eq 1.

Figure 5. Densities of [C4mim][Cl] with organic solvent of PYR as a function of temperature: ■, x = 0; □, x = 0.163; ●, x = 0.313; ○, x = 0.404; ▲, x = 0.514; △, x = 0.644; ▼, x = 0.803; ▽, x = 0.895; ◆, x = 1.000; solid line calculated by eq 1.

Figure 3. Densities of [C4mim][Cl] with organic solvent of DMF as a function of temperature: ■, x = 0; □, x = 0.151; ●, x = 0.295; ○, x = 0.385; ▲, x = 0.493; △, x = 0.626; ▼, x = 0.790; ▽, x = 0.887; ◆, x = 1.000; solid line calculated by eq 1.

Figure 6. VE of [C4mim][Cl] with organic solvent of DMA as a function of IL mole fraction: ■, 303.15 K; □, 308.15 K; ●, 313.15 K; ○, 318.15 K; ▲, 323.15 K; △, 328.15 K; ▼, 333.15 K; ▽, 338.15 K; ◆, 343.15 K; ◇, 348.15 K; ★, 353.15 K; solid line calculated by eq 5.

For further understanding of the mixtures, VE/(x·(1 − x)), reflecting the interactions in the case of apparent or partial molar volumes, as a function of IL mole fraction is presented in

Figures 10−13.12 VE/(x·(1 − x)) for the systems of IL with DMA and PYR increase with the increase of IL mole fraction D



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Figure 7. VE of [C4mim][Cl] with organic solvent of DMF as a function of IL mole fraction: ■, 303.15 K; □, 308.15 K; ●, 313.15 K; ○, 318.15 K; ▲, 323.15 K; △, 328.15 K; ▼, 333.15 K; ▽, 338.15 K; ◆, 343.15 K; ◇, 348.15 K; ★, 353.15 K; solid line calculated by eq 5.

Figure 10. VE/(x·(1 − x)) of [C4mim][Cl] with organic solvent of DMA as a function of IL mole fraction: ■, 303.15 K; □, 308.15 K; ●, 313.15 K; ○, 318.15 K; ▲, 323.15 K; △, 328.15 K; ▼, 333.15 K; ▽, 338.15 K; ◆, 343.15 K; ◇, 348.15 K; ★, 353.15 K.

Figure 8. VE of [C4mim][Cl] with organic solvent of DMSO as a function of IL mole fraction: ■, 303.15 K; □, 308.15 K; ●, 313.15 K; ○, 318.15 K; ▲, 323.15 K; △, 328.15 K; ▼, 333.15 K; ▽, 338.15 K; ◆, 343.15 K; ◇, 348.15 K; ★, 353.15 K; solid line calculated by eq 5.

Figure 11. VE/(x·(1 − x)) of [C4mim][Cl] with organic solvent of DMF as a function of IL mole fraction: ■, 303.15 K; □, 308.15 K; ●, 313.15 K; ○, 318.15 K; ▲, 323.15 K; △, 328.15 K; ▼, 333.15 K; ▽, 338.15 K; ◆, 343.15 K; ◇, 348.15 K; ★, 353.15 K.

Figure 9. VE of [C4mim][Cl] with organic solvent of PYR as a function of IL mole fraction: ■, 303.15 K; □, 308.15 K; ●, 313.15 K; ○, 318.15 K; ▲, 323.15 K; △, 328.15 K; ▼, 333.15 K; ▽, 338.15 K; ◆, 343.15 K; ◇, 348.15 K; ★, 353.15 K; solid line calculated by eq 5.

Figure 12. VE/(x·(1 − x)) of [C4mim][Cl] with organic solvent of DMSO as a function of IL mole fraction: ■, 303.15 K; □, 308.15 K; ●, 313.15 K; ○, 318.15 K; ▲, 323.15 K; △, 328.15 K; ▼, 333.15 K; ▽, 338.15 K; ◆, 343.15 K; ◇, 348.15 K; ★, 353.15 K.

and then decrease, while VE/(x·(1 − x)) for the mixture of IL with DMF only increases. It is interesting that VE/(x·(1 − x))

for the system of IL with DMSO decreases at low temperature (less than 328.15 K) and then increases at high temperature E



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(more than 333.15 K); moreover, at IL-rich range, VE/(x·(1 − x)) decreases. Generally, VE of the binary systems can be fitted by the Redlich−Kister equation. In this work, a Redlich−Kister type equation is introduced:15 V E = xi(1 − xi)(A 0 + A1T + A 2 xi)

data. The parameters are correlated and presented in Table 6. Figure 14 presents the relative deviations for the binary mixture densities of IL with DMF between the literature data and the calculated values using eq 4 fitted with the experimental values in this work. The AARD is 0.54% from Yan et al.,9 0.43%

(5)

−1

where V (cm ·mol ) is the excess molar volume; xi is the mole fraction of pure component i; T (K) is the temperature; and A0 (cm3·mol−1), A1 (cm3·mol−1·K−1), and A2 (cm3·mol−1) are the empirical parameters determined by the experimental E

3

Figure 14. Relative deviations for the binary mixture densities of IL with DMF between the literature values (ρlit) and the calculated data (ρcal) using eq 4 fitted with the experimental values in this work: ■, ref 9; □, ref 5; ●, ref 10; ★, this work. Figure 13. VE/(x·(1 − x)) of [C4mim][Cl] with organic solvent of PYR as a function of IL mole fraction: ■, 303.15 K; □, 308.15 K; ●, 313.15 K; ○, 318.15 K; ▲, 323.15 K; △, 328.15 K; ▼, 333.15 K; ▽, 338.15 K; ◆, 343.15 K; ◇, 348.15 K; ★, 353.15 K.

Table 6. Parameters Fitted by Experimental Data in This Work for Equation 1 and Equation 5 system IL DMA DMF DMSO PYR system IL IL IL IL

+ + + +

DMA DMF DMSO PYR

a0 (g·cm−3)

a1 (g·cm−3·K−1) −4

a2 g·cm−3·K−2

1.275 −7.258 × 10 1.191 −7.925 × 10−4 1.200 −7.746 × 10−4 1.389 −9.741 × 10−4 1.245 −7.915 × 10−4 A0 (cm3·mol−1) A1 cm3·mol−1·K−1

2.610 × 10−7 −2.046 × 10−7 −2.880 × 10−7 −3.753 × 10−8 −3.468 × 10−7 A2 cm3·mol−1

−0.0336 −0.0338 −0.0228 −0.0483

8.280 8.993 5.403 12.826

−4.999 −6.772 −2.833 −5.835

Figure 15. Relative deviations for the binary mixture densities of IL with DMSO between the literature values (ρlit) and the calculated data (ρcal) using eq 4 fitted with the experimental values in this work: ■, ref 8; ★, this work.

Table 7. Thermal Expansion Coefficients for [C4im][Cl] with Organic Solvent of DMA x [C4mim][Cl] + (1 − x) DMA, α (104·K−1) x T (K)

0.000

0.177

0.332

0.428

0.538

0.664

0.816

0.904

1.000

303.15 308.15 313.15 318.15 323.15 328.15 333.15 338.15 343.15 348.15 353.15

9.836 9.906 9.978 10.050 10.123 10.197 10.272 10.348 10.425 10.503 10.581

8.165 8.220 8.275 8.331 8.388 8.446 8.505 8.564 8.623 8.684 8.746

7.122 7.163 7.204 7.246 7.288 7.331 7.375 7.419 7.463 7.509 7.555

6.634 6.666 6.698 6.732 6.765 6.799 6.834 6.869 6.905 6.941 6.977

6.190 6.213 6.236 6.260 6.284 6.308 6.333 6.358 6.384 6.410 6.436

5.800 5.813 5.826 5.840 5.853 5.867 5.881 5.896 5.910 5.925 5.940

5.480 5.482 5.483 5.485 5.487 5.490 5.492 5.494 5.496 5.498 5.500

5.353 5.349 5.345 5.340 5.336 5.332 5.327 5.323 5.318 5.314 5.309

5.258 5.247 5.236 5.226 5.215 5.204 5.193 5.182 5.171 5.159 5.148

F



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where αi (K−1) is the thermal expansion coefficient of the pure component i and VEm is the excess molar volume of the binary system. The excess thermal expansion coefficient is obtained by

from Yang et al.,5 0.33% from Yang et al.10 Similarly, in Figure 15, the relative deviations are depicted for the binary mixture of IL with DMSO. The AARD is 0.40% from Govinda et al.8 The thermal expansion coefficient can be calculated using the measured density data by the following equation:

n

αE = α −

⎛ ∂ρ ⎞ α (K−1) = − ρ−1⎜ ⎟ ⎝ ∂T ⎠ p

(8)

i

(6)

where φi is the volume fraction of the pure component i, and it is calculated by

Using eq 3, the equation for thermal expansion coefficient is changed to ⎛ ∂V E ⎞ α = V m−1[⎜ m ⎟ + ⎝ ∂T ⎠ p , x

∑ φα i i

n

n

φi = xiVi /∑ xiVi

∑ (xiαiVi )] (7)

i

(9)

i

Table 8. Thermal Expansion Coefficients for [C4im][Cl] with Organic Solvent of DMF x [C4mim][Cl] + (1 − x) DMF, α (104·K−1) x T (K)

0.000

0.151

0.295

0.385

0.493

0.626

0.790

0.887

1.000

303.15 308.15 313.15 318.15 323.15 328.15 333.15 338.15 343.15 348.15 353.15

10.106 10.189 10.272 10.356 10.441 10.528 10.615 10.704 10.793 10.884 10.976

8.341 8.404 8.469 8.534 8.601 8.668 8.736 8.805 8.875 8.947 9.019

7.214 7.261 7.309 7.358 7.407 7.458 7.509 7.560 7.613 7.666 7.720

6.693 6.731 6.770 6.809 6.849 6.889 6.930 6.972 7.014 7.057 7.100

6.211 6.239 6.267 6.295 6.324 6.353 6.383 6.413 6.444 6.475 6.507

5.789 5.805 5.821 5.837 5.854 5.871 5.889 5.906 5.924 5.942 5.961

5.459 5.463 5.466 5.470 5.473 5.477 5.481 5.485 5.489 5.493 5.497

5.340 5.337 5.333 5.330 5.327 5.324 5.320 5.317 5.313 5.310 5.307

5.258 5.247 5.236 5.226 5.215 5.204 5.193 5.182 5.171 5.159 5.148

Table 9. Thermal Expansion Coefficients for [C4im][Cl] with Organic Solvent of DMSO x [C4mim][Cl] + (1 − x) DMSO, α (104·K−1) x T (K)

0.000

0.161

0.309

0.401

0.509

0.641

0.801

0.894

1.000

303.15 308.15 313.15 318.15 323.15 328.15 333.15 338.15 343.15 348.15 353.15

9.143 9.189 9.235 9.281 9.328 9.375 9.423 9.471 9.519 9.569 9.618

7.636 7.669 7.703 7.736 7.770 7.805 7.840 7.875 7.910 7.946 7.983

6.734 6.757 6.780 6.803 6.827 6.850 6.874 6.898 6.923 6.948 6.973

6.331 6.348 6.365 6.383 6.400 6.418 6.436 6.454 6.472 6.491 6.510

5.969 5.980 5.991 6.002 6.013 6.025 6.036 6.047 6.059 6.071 6.083

5.656 5.660 5.664 5.668 5.673 5.677 5.682 5.686 5.690 5.695 5.700

5.412 5.409 5.406 5.403 5.400 5.397 5.394 5.391 5.388 5.385 5.382

5.323 5.316 5.310 5.303 5.296 5.289 5.282 5.275 5.268 5.261 5.254

5.258 5.247 5.236 5.226 5.215 5.204 5.193 5.182 5.171 5.159 5.148

Table 10. Thermal Expansion Coefficients for [C4im][Cl] with Organic Solvent of PYR x [C4im][Cl] + (1 − x) PYR, α (104·K−1) x T (K)

0.000

0.163

0.313

0.404

0.514

0.644

0.803

0.895

1.000

303.15 308.15 313.15 318.15 323.15 328.15 333.15 338.15 343.15 348.15 353.15

10.294 10.384 10.474 10.565 10.658 10.752 10.847 10.943 11.040 11.139 11.239

8.222 8.293 8.364 8.436 8.509 8.583 8.658 8.734 8.811 8.890 8.969

6.977 7.030 7.083 7.137 7.192 7.248 7.304 7.362 7.420 7.479 7.539

6.436 6.478 6.521 6.565 6.609 6.654 6.700 6.746 6.793 6.841 6.890

5.955 5.986 6.017 6.049 6.082 6.115 6.148 6.182 6.216 6.251 6.287

5.575 5.594 5.612 5.631 5.651 5.670 5.690 5.710 5.731 5.752 5.774

5.325 5.329 5.334 5.339 5.343 5.349 5.354 5.359 5.364 5.370 5.375

5.265 5.262 5.259 5.256 5.254 5.251 5.249 5.246 5.243 5.240 5.237

5.258 5.247 5.236 5.226 5.215 5.204 5.193 5.182 5.171 5.159 5.148

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Article

Figure 19. Excess thermal expansion coefficient αE for [C4mim][Cl] with organic solvent of PYR as a function of IL mole fraction: ■, 303.15 K; □, 308.15 K; ●, 313.15 K; ○, 318.15 K; ▲, 323.15 K; △, 328.15 K; ▼, 333.15 K; ▽, 338.15 K; ◆, 343.15 K; ◇, 348.15 K; ★, 353.15 K.

Figure 16. Excess thermal expansion coefficient αE for [C4mim][Cl] with organic solvent of DMA as a function of IL mole fraction: ■, 303.15 K; □, 308.15 K; ●, 313.15 K; ○, 318.15 K; ▲, 323.15 K; △, 328.15 K; ▼, 333.15 K; ▽, 338.15 K; ◆, 343.15 K; ◇, 348.15 K; ★, 353.15 K.

The calculated thermal expansion coefficients are summarized in Tables 7−10. The coefficients of pure IL decrease with the increase of temperature, while those of pure solvents increase with the increase of temperature. Furthermore, the values of thermal expansion coefficient for the binary systems at IL-rich ranges perform the similar behavior as that of pure IL. The excess thermal expansion coefficient as a function of IL mole fraction is presented in Figures 16−19.

■

CONCLUSIONS IL of [C4mim][Cl] shows great promises in chemical and biochemical processes. In this work, the experimental densities for the binary mixtures of IL with organic solvents of DMA, DMF, DMSO, and PYR are determined by an Anton Paar DMA 5000 M digital vibrating U-tube densimeter with the temperature ranges from 303.15 to 353.15 K at atmospheric pressure. The negative excess molar volumes are observed in all the binary systems, indicating that volume contraction occurs. Large negative VE exhibits in the system of IL with PYR, while small negative VE exhibits in the system of IL with DMSO. The thermal expansion coefficients as well as the excess properties are obtained, and the coefficients of pure IL decrease with the increase of temperature, while those of pure solvents increase with the increase of temperature.

Figure 17. Excess thermal expansion coefficient αE for [C4mim][Cl] with organic solvent of DMF as a function of IL mole fraction: ■, 303.15 K; □, 308.15 K; ●, 313.15 K; ○, 318.15 K; ▲, 323.15 K; △, 328.15 K; ▼, 333.15 K; ▽, 338.15 K; ◆, 343.15 K; ◇, 348.15 K; ★, 353.15 K.

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AUTHOR INFORMATION

Corresponding Author

*Xiaopo Wang. Tel.: +86 (0)29-82668210. Fax: +86 (0)2982663584. E-mail: [email protected]. ORCID

Fuxin Yang: 0000-0001-9640-3231 Xiaopo Wang: 0000-0002-5550-2193 Funding

The work is supported by the National Natural Science Foundation of China (No. 51606147) and the Fundamental Research Funds for the Central Universities. Notes

The authors declare no competing financial interest.

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Figure 18. Excess thermal expansion coefficient α for [C4mim][Cl] with organic solvent of DMSO as a function of IL mole fraction: ■, 303.15 K; □, 308.15 K; ●, 313.15 K; ○, 318.15 K; ▲, 323.15 K; △, 328.15 K; ▼, 333.15 K; ▽, 338.15 K; ◆, 343.15 K; ◇, 348.15 K; ★, 353.15 K. E

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Volumetric Properties of 1-Butyl-3-methylimidazolium Chloride with

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