Vapor Pressure Measurement of Ternary Systems LiCl + [Emim]Cl +

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Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Vapor Pressure Measurement of Ternary Systems LiCl + [Emim]Cl + H2O, LiBr + [Emim]Cl + H2O, and LiCl + [Emim]Br + H2O Yongmei Xuan,† Xianyu Ding,† Neng Gao,† Yaqi Ding,‡ Xin Meng,§ and Guangming Chen*,§ †

Ningbo Institute of Technology, Zhejiang University, Ningbo 315100, P. R. China Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou 310027, P. R. China § School of Mechanical Engineering, Shaanxi University of Technology, Hanzhong 723001, P. R. China

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‡

ABSTRACT: 1-Ethyl-3-methylimidazolium chlorine ([Emim]Cl) and 1ethyl-3-methylimidazolium bromide ([Emim]Br) as an additive to working fluid [lithium bromide aqueous solution (H2O/LiBr) and lithium chloride aqueous solution (H2O/LiCl)] of absorption cycles were proposed. The vapor pressure of H2O + LiCl + [Emim]Cl (mass ratio LiCl/[Emim]Cl = 2) in the temperature from 314.79 to 435.48 K, H2O + LiCl + [Emim]Br (mass ratio LiCl/[Emim]Br = 2) in the temperature from 317.62 to 431.27 K, and H2O + LiBr + [Emim]Cl (mass ratio LiBr/[Emim]Cl = 2) in the temperature from 303.10 to 409.91 K was measured by the boiling point method. The mass fractions of the absorbent were from 0.30 to 0.60. The experimental data were regressed using the Antoine-type equation, and the average absolute relative deviation (AARD %) between the experimental data and calculated values of three systems was 0.44, 0.51, and 0.54%. Compared with that of the previously reported ionic liquids, ([Emim]Ac) as an absorbent for LiBr + H2O, vapor pressure of these four systems follows the order LiCl + [Emim]Cl + H2O < LiCl + [Emim]Br + H2O < LiBr + [Emim]Cl + H2O < LiBr + [Emim]Ac + H2O. The proposed ternary systems have better water affinity and can be promising alternative working fluids in the absorption cooling system.

1. INTRODUCTION The refrigeration system is an essential part in industry and daily life. Electrical-driven refrigeration (such as vapor compression systems) and thermal-driven refrigeration (such as vapor absorption systems) are two commonly used refrigeration methods. Unlike electrical-driven refrigeration systems, thermal-driven refrigeration systems can be driven by low-grade thermal energy or renewable energy (e.g., waste heat and solar energy), which makes it electrical saving. Besides, a lot of refrigerants used in electrical systems have ozone depletion potential and global warming potential, whereas the refrigerants used in the absorption system are more environmentally friendly. Because of these advantages, the thermaldriven absorption refrigeration method is now receiving more and more attention under the increasing energy crisis and environmental protection background. The refrigerant/absorbent pair involved in the absorption system is of crucial importance to the system operating conditions and cycle performance. Lithium bromide aqueous solution (H2O/LiBr), lithium chloride aqueous solution (H2O/LiCl), and ammonia−water (NH3/H2O) are widely used working pairs in absorption cycle because of their outstanding physical properties and thermodynamic properties.1,2 However, both H2O/LiBr and H2O/LiCl are corrosive to the metals and tend to crystallize under low temperature. Although NH3/H2O has no risk of crystallization, it is corrosive, toxic and has relatively low volatility. © XXXX American Chemical Society

To overcome these inherent disadvantages, many research studies have been working on finding more effective additives or alternative working pairs to improve the performance of absorption refrigeration cycles. Among these candidates, ionic liquids (ILs) have been proved to be potential absorbents or additives in absorption systems. ILs are a family of molten salts at room temperature. Because of their particular properties, such as negligible vapor pressure, high thermal and chemical stability, a wide temperature range of liquid state, good solubility of gases, and no or very low corrosion to metals, ILs have been studied in many absorption refrigeration literatures.3−17 As is well known, the vapor liquid equilibrium is an important property to analyze the intermolecular force between solute and solvent; by using vapor pressure equilibrium data, it is possible to obtain information about other properties, which can give an idea about the applicability of the mixtures as working fluids. Therefore, it is particularly important to study the vapor pressure properties of ILs/ refrigerant mixtures. Till now, a lot of the literatures have dedicated to studying vapor pressure performance of ILs/H2O or mixtures of ammonia and ILs. The first vapor−liquid equilibrium (VLE) data of ammonia/ILs were reported by Received: December 17, 2018 Accepted: May 2, 2019

A

DOI: 10.1021/acs.jced.8b01217 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Yokozeki and Shiflett.3,4 Several further research studies were performed to study the VLE of ammonia with ILs or ternary system when ILs are used as an additive.5−8 There were also some studies on VLE models of IL-based working fluid.3,4,9−11 All of these research studies have proved that there is a great potential of using ILs in absorption working fluids. However, only a small amount of literatures is focused on assessing the performance of ILs with conventional working fluid (H2O/ LiBr or H2O/LiCl).12−14 In our group’s previous research,12 the VLE data of 1-ethyl-3-methylimidazolium acetate ([Emim]Ac) as an additive to H2O/LiBr have been measured (mass ratio LiBr/[Emim]Ac = 3). The experimental results indicated that compared with conventional H2O/LiBr system and two other ternary systems ([Dmim]DMP/LiBr/H2O and [Dmim]BF4/LiBr/H2O), the experimental ternary system has lower vapor pressures and can be used as a promising alternative working fluid in absorption systems. Despite the above pioneer studies on the ILs to H2O/ LiBr(LiCl) absorption refrigeration cycle, considering the diversity of ILs (about 1018 kinds) and also the continuous requirements to improve the performance of absorption refrigeration systems, further deeper research studies are still necessary to find better potential attractive ILs. ILs consisted of organic cations and typically smaller inorganic or organic anions. The hydrophilic property of ILs was influenced by the organic cation, the length of the side chain, and the anion. Existing research studies have showed that the anion is essential for the vapor pressure reduction of water and imidazole-based ILs. The anion such as acetate (Ac), chlorine (Cl), and bromine (Br) can be mutually soluble with water and may have a strong moisture absorption property.15−17 On the basis of the literature survey carried out and our group’s previous study,12 taking into account the properties that are desirable for an absorbent, two ILs [1-ethyl-3methylimidazolium chlorine ([Emim]Cl) and 1-ethyl-3-methylimidazolium bromide ([Emim]Br)] with different anions (Cl− and Br−) and the same cations [Emim] have been selected and measured experimentally to study the effect of ILs as an additive to H2O/LiBr and H2O/LiCl. Therefore, in this work, VLE data of three ternary mixtures ([Emim]Cl + LiBr + H2O, [Emim]Br + LiCl + H2O, and [Emim]Cl + LiCl + H2O) are measured at a temperature range from 303.10 to 409.91, 317.62 to 431.27, and 314.79 to 435.48 K, respectively. The mass fraction of the absorbent is from 0.30 and 0.60. To ensure that the vapor pressure of the system is sufficiently low, the mass ratio of LiBr/[Emim]Cl, LiCl/ [Emim]Br, and LiCl/[Emim]Cl is all set to 2. The vapor pressure was measured using the boiling point method. To the best of our knowledge, this is the first time that the vapor pressure of ILs ([Emim]Cl and [Emim]Br) with H2O/LiBr and H2O/LiCl has been measured experimentally within this temperature range. The obtained vapor pressure data were compared with ILs ([Emim]Ac) reported in our group’s previous work12 as an absorbent for LiBr/H2O.

The purity and detailed information of these reagents are listed in Table 1. The pure water was double-distilled and deionized. The mass of all of these components was determined by weighing with a precision electronic balance with an accuracy of 0.01 g. Table 1. Source and Purity of Chemical Samples chemical name

mass fraction purity (%)

CASRN

source

[Emim] Cla

65039-09-0

Lanzhou Green Chem ILS, Lanzhou Institute of Chemical Physics, China

[Emim] Brb lithium bromide lithium chloride sodium chloride

65039-08-9 7550-35-8

Aladdin Chemistry Co., Ltd., China

7447-41-8 7647-14-5

Sinopharm Chemical Reagent Co., Ltd., China

purification method

99

none

99

none

99.9

none

99

none

99.8

none

a

[Emim]Cl = 1-ethyl-3-methylimidazolium chlorine. b[Emim]Br = 1ethyl-3-methylimidazolium bromide.

2.2. Apparatus. The schematic diagram of the experimental apparatus is shown in Figure 1. The apparatus

Figure 1. Schematic diagram of the experimental apparatus: (1) computer; (2) oil bath with a magnetic stirrer; (3) water pump; (4) water tank; (5) Agilent dynamic signal analyzer; (6) equilibrium; (7) buffer bottle; (8) vacuum pump; (9) spherical condenser; (10) silicon pressure sensor; (11) temperature sensor; (12) clamp; (13) air inlet; and (14) high vacuum valve.

consisted of an equilibrium vessel of 500 cm3, an oil constant-temperature bath, a magnetic stirrer, a condenser, a PTX50A2-type GE Druck silicon pressure sensor, an air inlet, a vacuum pump, a high vacuum valve, and a buffer bottle, a water tank and a water pump, a temperature sensor calibrated with an uncertainty of 0.05 K, a silicon pressure sensor with an accuracy of ±0.064 kPa, a computer, and a 34970A-type Agilent dynamic signal analyzer.12 Because the vapor pressure of the ILs is neglectable compared with the vapor pressure of water, the vapor pressure can be measured by the boiling point method. During the experiments, water at the dew point temperature of indoor air was pumped to the condenser to maintain the initial concentration of the sample solutions. During the experiment, control the temperature of water in the tank to rise no more

2. EXPERIMENT 2.1. Materials. ILs, [Emim]Cl and [Emim]Br, used in experiments were supplied by Lanzhou Green Chem ILS, Lanzhou Institute of Chemical Physics, China. Lithium bromide and lithium chloride reagent were supplied by Aladdin Chemistry Co., Ltd., China. The sodium chloride reagent which was used to test the validity of the system was supplied by Sinopharm Chemical Reagent Co., Ltd., China. B

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Table 2. Vapor Pressure Data of Pure Water and NaCl Aqueous Solution with a Mass Fraction of 0.25 from Experiment and Literature pure water

NaCl aqueous solution (w = 0.25) a

T/K

Pexp/kPa

Plit/kPa

RD %

T/K

Pexp/kPa

Plit/kPa

RD %a

325.003 333.998 341.704 347.626 352.571 357.986 362.298 366.101 369.263 372.154 AARD %b

13.667 20.815 29.423 37.697 45.976 57.445 67.611 78.183 87.568 97.389

13.533 20.742 29.301 37.757 46.314 57.496 67.941 78.424 88.134 97.866 0.47

0.990 0.352 0.416 −0.159 −0.730 −0.089 −0.486 −0.307 −0.642 −0.487

304.785 325.460 339.974 347.721 356.270 359.767 365.851 370.753 373.110 380.134

3.691 10.915 21.435 29.815 42.415 48.402 59.791 73.350 78.595 102.779

3.697 10.908 21.331 29.675 42.043 48.127 60.059 72.794 78.587 101.345 0.53

−0.162 0.064 0.488 0.472 0.885 0.571 −0.446 0.764 0.010 1.415

Pexp − Plit y N i zz/N , N is the number of measured points. Pexp and Plit are the vapor pressure data AARD % = ∑i = 1 jjj100%· P z lit k { from experiment and literature, respectively. Standard uncertainties u are u(T) = 0.07 K, u(w) = 4 × 10−5, and u(p) = 0.067 kPa. a

RD % = 100%·

(

Pexp − Plit Plit

).

b

than 2 °C. The buffer bottle was connected to the vacuum pump in order to prevent the rapid fluctuations of pressure. 2.3. Test Procedure. First, a certain amount of the sample solution (with an approximate volume of 250 cm3) was prepared to the desired concentration, stirred thoroughly, cooled well, and poured into the equilibrium vessel. Then, the vessel with the sample was put into the oil bath and was evacuated to a proper degree of pressure, a little higher than the vapor pressure of each sample. The sample solution was heated and stirred well with a magnetic stirrer to prevent overheating. When thermal equilibrium was reached, the VLE data were measured and read on the computer. Controlling the air inlet to increase pressure, another equilibrium can be reached. 2.4. Verification of the System. The accuracy of the system was first verified by testing the vapor pressure of pure water and NaCl aqueous solution with a mass fraction of 0.25 as standard solutions. Comparing the measured vapor pressure data with those from REFPROP and literature,18,19 the average absolute relative deviations (AARD %) of pure water and NaCl aqueous solution (mass fraction of 0.25) were determined to be 0.47 and 0.53%, respectively. The experimental data and relative deviation (RD %) of two above liquids are illustrated in Table 2 and Figure 2. It can be seen that the test data are in good agreement with the literature. The measurement accuracy of the system and the reliability of the procedure was verified and confirmed.

Figure 2. RDs Δp/p = (pexp − plit)/plit of the experimental vapor pressures pexp with the vapor pressure data from literatures plit for pure water18 and NaCl aqueous solution (with mass ratio of 0.25).19 ■, this work, pure water; □, this work, NaCl aqueous solution (with mass ratio of 0.25).

where p is the vapor pressure in kPa; T is the temperature in K; w is the mass fraction of all absorbent species. Ai, Bi, and Ci are the Antoine parameters, listed in Table 4. In the LiCl + [Emim]Cl + H2O system, the average absolute relative deviation (AARD %) between experimental data and calculated values was 0.44%, showing good consistency and accuracy. The fitted curves from the Antoine-type equation and experimental values with temperature at different mass ratios are shown in Figure 3. Vapor pressures increased with temperature but decreased greatly with the increase of mass fractions. The RDs of most points (LiCl + [Emim]Cl + H2O) between experimental and calculated data are presented in Figure 4. Most of the deviations are less than 1%, which indicated that there is good consistency between experimental data and calculated results. 3.2. Experimental Data of LiCl + [Emim]Br + H2O. The vapor pressure of LiCl + [Emim]Br + H2O was measured in the temperature from 317.62 to 431.27 K and in the mass

3. RESULTS AND DISCUSSION 3.1. Experimental Data of LiCl + [Emim]Cl + H2O. The vapor pressures of LiCl + [Emim]Cl + H2O were measured by using the boiling point method in the temperature from 314.79 to 435.48 K and in the mass fraction of [Emim]Cl + LiCl from 0.30 to 0.60. The experimental data are listed in Table 3 and fitted to an Antoine-type equation ARD % = 100|Pexp − Pcal|/ Ä P − P ÑÉ Å exp cal Ñ N Å 1 pcal, AARD % = N ∑i = 1 ÅÅÅ P ÑÑÑ. Here, N is the number of ÅÇ cal ÑÖ measured points. Pexp are vapor pressures from experiments; Pcal are vapor pressures calculated by Antoine-type eq 1. 3

log(p) =

∑ {Ai + [1000Bi /(T /K − C)]}wi i=0

(1) C

DOI: 10.1021/acs.jced.8b01217 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Table 3. Experimental and Calculated Vapor Pressures for the Ternary System of LiCl (1) + [Emim]Cl (2) + H2O (LiCl/ [Emim]Cl Mass Ratio = 2:1)a T/K w1+2 = 0.3 314.79 339.51 348.58 356.03 361.45 370.97 374.89 378.40 380.82 384.28 387.22 w1+2 = 0.5 329.15 360.67 375.01 383.78 391.52 398.94 401.04 404.92 408.97 411.76 414.90

Pexp/kPa

Pcal/kPa

ARD %

6.231 18.487 26.621 35.393 43.619 60.479 68.947 77.499 84.030 94.066 103.313

6.228 18.524 26.627 35.389 43.217 60.496 69.144 77.735 84.184 94.161 103.411

0.048 0.200 0.023 0.011 0.930 0.028 0.285 0.304 0.183 0.101 0.095

3.988 14.713 25.751 35.621 46.787 60.531 65.255 74.788 85.592 92.357 102.744

3.999 14.706 25.537 35.322 46.646 60.470 64.999 74.178 84.951 93.203 103.288

0.275 0.048 0.838 0.846 0.302 0.101 0.394 0.822 0.755 0.908 0.527

T/K w1+2 = 0.4 326.40 350.35 363.16 374.95 378.44 387.35 392.15 395.83 399.75 402.12 404.92 w1+2 = 0.6 358.30 387.33 399.97 409.45 414.19 419.71 424.52 427.96 430.07 432.37 435.48

Pexp/kPa

Pcal/kPa

ARD %

5.959 15.758 25.295 38.631 43.499 58.865 68.762 77.850 87.380 94.763 102.508

5.964 15.826 25.608 38.930 43.895 59.087 69.029 77.600 87.700 94.363 102.767

0.084 0.430 1.222 0.768 0.902 0.376 0.387 0.322 0.365 0.424 0.252

4.291 15.217 26.177 38.048 45.384 56.330 68.202 77.633 83.542 91.622 102.653

4.337 15.377 25.939 37.937 45.709 56.612 68.039 77.458 83.826 91.300 102.373

1.061 1.041 0.918 0.293 0.711 0.498 0.240 0.226 0.339 0.353 0.274

a w is the mass fraction of all solute species, pexp values are vapor pressures from the experiment, and pcal values are calculated by the Antoine-type equation. The vapor pressure was measured over the liquid phase. AARD % = 0.44%. Standard uncertainties u are U(T) = 0.07 K, U(w) = 4 × 10−5, and U(p) = 0.20 kPa. The uncertainty of the mass ratio (LiCl/[Emim]Cl) was 9.19 × 10−6.

Table 4. Regressed Parameters of Antoine-Type Equation for LiCl + [Emim]Cl + H2O i

A

B

C

0 1 2 3

25.702971 −69.808438 148.540412 −45.826769

−3.547088 −22.966119 2.264742 −48.681293

58.176686 −22 356.611690 179.130485 −224.197341

Figure 4. RDs of the vapor pressures from experiment and calculation by the Antoine-type equation for the LiCl + [Emim]Cl + H2O system (LiCl/[Emim]Cl mass ratio = 2:1): Δp/p = (pexp − pcal)/pcal.

fraction of [Emim]Br + LiCl from 0.30 to 0.60. The experimental vapor pressure data of the ternary mixture (LiCl + [Emim]Br + H2O) are listed in Table 5 and fitted by eq 1. The regressed parameters of Antoine-type equation for LiCl + [Emim]Br + H2O (Ai, Bi, and Ci) are listed in Table 6. The corresponding AARD % value was 0.51%. The fitted curves from the Antoine-type equation and experimental values with temperature are plotted in Figure 5. The RDs between experimental data and calculated value are showed in Figure 6.

Figure 3. Curves of the vapor pressure for the LiCl + [Emim]Cl + H2O system (LiCl/[Emim]Cl mass ratio = 2:1) at temperatures from 314.79 to 435.48 K; experimental data: ■, w = 0.3; ●, w = 0.4; ▲, w = 0.5; and ⧫, w = 0.6; curves of calculated data: , from the Antoinetype equation. D

DOI: 10.1021/acs.jced.8b01217 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Table 5. Experimental and Calculated Vapor Pressures for the Ternary System of LiCl (1) + [Emim]Br (2) + H2O (LiCl/ [Emim]Br Mass Ratio = 2:1)a T/K w1+2 = 0.3 317.62 340.13 347.83 360.83 366.38 369.33 375.51 378.17 381.66 384.49 387.49 w1+2 = 0.5 338.81 360.46 372.71 382.27 387.83 394.24 399.47 403.33 407.25 411.09 412.75

Pexp/kPa

Pcal/kPa

ARD %

5.605 16.318 23.043 39.338 47.923 54.401 67.922 74.928 84.081 93.067 102.098

5.678 16.503 23.016 39.027 48.330 53.995 67.715 74.473 84.198 92.856 102.844

1.286 1.121 0.117 0.797 0.842 0.752 0.306 0.611 0.139 0.227 0.725

6.484 16.111 26.177 37.057 45.072 55.702 67.197 75.069 84.707 95.214 101.639

6.418 16.257 26.179 37.125 45.115 56.067 66.571 75.327 85.161 95.815 100.720

1.028 0.898 0.008 0.183 0.095 0.651 0.940 0.343 0.533 0.627 0.912

T/K

Pexp/kPa

Pcal/kPa

ARD %

7.813 16.547 27.513 36.794 47.780 56.655 67.505 74.838 84.911 94.677 101.844

7.821 16.600 27.698 36.952 47.757 56.552 67.697 75.225 84.462 94.569 101.892

0.102 0.319 0.668 0.428 0.048 0.182 0.284 0.514 0.532 0.114 0.047

5.010 14.012 24.704 34.264 46.018 56.474 66.885 75.464 86.981 93.386 100.238

5.007 13.907 24.384 34.095 45.790 56.211 67.734 75.963 86.811 93.106 100.335

0.060 0.755 1.312 0.496 0.498 0.468 1.253 0.657 0.196 0.301 0.097

w1+2 = 0.4 334.41 351.48 364.17 371.73 378.75 383.52 388.74 391.87 395.37 398.85 401.18 w1+2 = 0.6 345.52 370.19 385.43 395.21 404.29 410.90 417.16 421.14 425.90 428.47 431.27

The vapor pressure was measured over the liquid phase. AARD % = 0.51%. Standard uncertainties u are U(T) = 0.07 K, U(w) = 4 × 10−5, and U(p) = 0.25 kPa. The uncertainty of the mass ratio (LiCl/[Emim]Br) was 9.19 × 10−6.

a

Table 6. Regressed Parameters of Antoine-Type Equation for LiCl + [Emim]Br + H2O i

A

B

C

0 1 2 3

21.113320 −24.478759 63.375158 −40.048727

−4.575033 −0.920008 −119.563542 0.034747

11.214994 −46.605635 −10 879.578400 489.014250

It can be seen that most of the deviation fluctuating between ±1%, indicating good consistency. 3.3. Experimental Data of LiBr + [Emim]Cl + H2O. The vapor pressure of LiBr + [Emim]Cl + H2O was measured in the temperature from 303.10 to 409.91 K and in the mass fraction of [Emim]Cl + LiBr from 0.30 to 0.60. The experimental data of ternary mixtures (LiBr + [Emim]Cl + H2O) are listed in Table 7 and fitted to eq 1. The regressed parameters of the Antoine-type equation for LiBr + [Emim]Cl + H2O (Ai, Bi, and Ci) are shown in Table 8. The AARD % value was found to be 0.54%. The fitted curves from eq 1 and experimental data with temperature are plotted in Figure 7. The RDs between experimental data and calculated value are presented in Figure 8. 3.4. Uncertainty. The uncertainty of temperature measurement UT consists of three parts, uncertainty of the calibrated temperature sensor UT1 = 0.05 K, uncertainty of the Agilent data acquisition unit UT2 = 0.006 K, and uncertainty from the reading fluctuations UT3 = 0.05 K. Therefore, the combined uncertainty of temperature can be obtained by

Figure 5. Curves of the vapor pressure of the LiCl + [Emim]Br + H2O system (LiCl/[Emim]Br mass ratio = 2:1) at temperatures from 317.62 to 431.27 K; experimental data: ■, w = 0.3; ●, w = 0.4; ▲, w = 0.5; and ⧫, w = 0.6; curves of calculated data: , from the Antoinetype equation. 3

UT =

∑ UT 2 i

i=1

= 0.07 K (2)

The uncertainty of mass fraction Uw was 4 × 10−5 because the accuracy of the electronic balance was 0.01 g and the chemical samples weighed between 300 and 600 g. For the uncertainty of pressure up, it is determined by three parts, uncertainty of the silicon pressure sensor up1 = 0.064 kPa, E

DOI: 10.1021/acs.jced.8b01217 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Table 8. Regressed Parameters of Antoine-Type Equation for LiBr + [Emim]Cl + H2O i

A

B

C

0 1 2 3

23.653949 −32.434803 87.047486 −75.734834

−5.384665 −114.984299 0.012932 −1.846908

−9.771712 −25 419.077950 283.819010 839.518866

Figure 6. RDs of the vapor pressures from experiment and calculation by the Antoine-type equation for the LiCl + [Emim]Br + H2O system (LiCl/[Emim]Br mass ratio = 2:1): Δp/p = (pexp − pcal)/pcal.

uncertainty of the Agilent data acquisition unit up2 = 0.002 kPa, and uncertainty from the reading fluctuations up3 = 0.02 kPa. Therefore, up of can be calculated by

Figure 7. Curves of the vapor pressure of the LiBr + [Emim]Cl + H2O system (LiBr/[Emim]Cl mass ratio = 2:1) at temperatures from 303.10 to 426.31 K; experimental data: ■, w = 0.3; ●, w = 0.4; ▲, w = 0.5; and ⧫, w = 0.6; curves of calculated data: , from the Antoinetype equation.

3

up =

∑ u p2 i

= 0.067 kPa (3)

i=1

Table 7. Experimental and Calculated Vapor Pressures for the Ternary System of LiBr (1) + [Emim]Cl (2) + H2O (LiBr/ [Emim]Cl Mass Ratio = 2:1)a T/K w1+2 = 0.3 303.10 335.22 347.44 355.32 361.18 364.34 368.47 371.74 374.27 376.01 378.43 w1+2 = 0.5 313.28 333.60 349.37 361.49 367.25 372.97 377.74 382.58 385.06 388.62 391.17

Pexp/kPa

Pcal/kPa

T/K

ARD %

3.507 17.534 30.130 42.000 53.332 60.291 70.600 79.772 87.500 93.267 103.110

3.524 17.539 30.259 42.311 53.430 60.416 70.728 79.938 87.757 93.510 102.048

0.482 0.029 0.426 0.735 0.183 0.207 0.181 0.208 0.293 0.260 1.041

3.601 9.961 20.000 33.293 42.215 52.540 62.719 74.710 81.575 92.345 102.945

3.666 10.067 20.148 33.465 42.414 52.717 62.915 74.980 81.908 92.823 102.399

1.773 1.053 0.735 0.514 0.469 0.336 0.312 0.360 0.407 0.515 0.533

w1+2 = 0.4 302.40 336.03 347.70 355.67 362.63 367.93 373.75 377.45 379.95 381.91 385.52 w1+2 = 0.6 328.11 353.24 367.33 377.60 384.13 389.78 395.81 399.22 403.33 406.58 409.91

Pexp/kPa

Pcal/kPa

ARD %

3.072 15.265 25.061 34.823 45.309 55.055 67.560 76.675 84.170 90.647 103.025

3.031 15.551 25.070 34.601 45.321 54.872 67.635 77.452 84.763 90.904 103.225

1.353 1.839 0.036 0.642 0.026 0.334 0.111 1.003 0.700 0.283 0.194

4.428 12.990 22.865 33.425 42.433 51.901 64.294 72.566 83.467 91.894 102.924

4.483 12.790 22.590 33.442 42.524 52.065 64.276 72.238 82.974 92.429 103.084

1.227 1.564 1.217 0.051 0.214 0.315 0.028 0.454 0.594 0.579 0.155

The vapor pressure was measured over the liquid phase. AARD % = 0.54%. Standard uncertainties u are U(T) = 0.07 K, U(w) = 4 × 10−5, and U(p) = 0.28 kPa. The uncertainty of the mass ratio (LiBr/[Emim]Cl) was 9.19 × 10−6.

a

F

DOI: 10.1021/acs.jced.8b01217 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Figure 9. Vapor pressure of a ternary system in the literature containing LiBr + [Emim]Ac + H2O and the measured systems in this paper: ■, LiCl + [Emim]Cl + H2O, mass ratio = 2:1, w = 0.4;  ●, LiCl + [Emim]Br + H2O, mass ratio = 2:1, w = 0.4; ★, LiBr + [Emim]Cl + H2O, mass ratio = 2:1, w = 0.4; ▲, LiBr + [Emim]Ac + H2O, mass ratio = 3:1, w = 0.4.

Figure 8. RDs of the vapor pressures from experiment and calculation by the Antoine-type equation for the LiBr + [Emim]Cl + H2O system (LiBr/[Emim]Cl mass ratio = 2:1): Δp/p = (pexp − pcal)/pcal.

As proved in the previous study, the ternary system [Emim] Ac + LiBr + H2O has lower vapor pressure than the conventional LiBr + H2O system; the proposed ternary systems in this work (LiCl + [Emim]Cl + H2O, LiCl + [Emim]Br + H2O, and LiBr + [Emim]Cl + H2O) have better water absorption ability. The combined actions of absorbent and ILs can reduce the vapor pressure of the fluid. It is reasonable to use [Emim]Cl and [Emim]Br as additives in working fluids of the absorption refrigeration system. The effect of [Emim]Cl and [Emim]Br on lower vapor pressure is superior to that of adding [Emim]Ac. As vapor pressure is an important factor which particularly affects the performance of an absorption cycle, the three proposed ternary fluids in this work are the potential absorption working substance.

The expanded combined uncertainty of the vapor pressure Up can be calculated by ij ∂p yz zz (u )2 Up = k ∑ jjj j ∂Xi zz Xi { i=1 k 3

2

(4)

where Xi includes all of the variables (temperature T, mass fraction w, and vapor pressure p). k is the coverage factor and k ≈ 2 for 95% confidence interval. According to eq 4, the final Up values of ternary systems LiCl + [Emim]Cl + H2O, LiCl + [Emim]Br + H2O, and LiBr + [Emim]Cl + H2O were determined to be 0.20, 0.25, and 0.28 kPa (k = 2). See more details in the previous study.12 3.5. Comparison with the Previous Study. The measured vapor pressure of LiCl + [Emim]Cl + H2O, LiCl + [Emim]Br + H2O, and LiBr + [Emim]Cl + H2O was compared with our group’s previous study (LiBr + [Emim]Ac + H2O)12 and is illustrated in Figure 9. In the comparison, the mass fractions of absorbent species were all 0.4. As can be seen from Figure 9, under the same temperature, the measured vapor pressure of this work is lower than our previous work. The vapor pressures of these four systems follow the order LiCl + [Emim]Cl + H2O < LiCl + [Emim]Br + H2O < LiBr + [Emim]Cl + H2O < LiBr + [Emim]Ac + H2O. By comparison, two comparison conclusions can be made. First, when using the same ILs, the LiCl aqueous solution system has lower vapor pressure, LiCl + [Emim]Cl + H2O < LiBr + [Emim]Cl + H2O. This is because the lithium chloride aqueous solution has better water absorption ability than the lithium bromide aqueous solution. Second, under the same temperature, the proposed IL mixtures have lower vapor pressure than our previous work, the vapor pressure of LiCl + [Emim]Cl + H2O < LiCl + [Emim]Br + H2O, and LiBr + [Emim]Cl + H2O < LiBr + [Emim]Ac + H2O. The primary reason is because of the water affinity of different ILs. As the VLE properties of IL-based mixtures have a strong dependency on the anion, better water affinity leads to lower vapor pressure. Under experimental conditions, the water affinity of [Cl]− > [Ac]−, [Cl]− > [Br]−.

4. CONCLUSIONS (1) ILs are particularly attractive as potential absorbents or additives in absorption systems. Using the reliable boiling point method, the vapor pressure data of three different ionic systems, LiCl + [Emim]Cl + H2O (mass ratio LiCl/[Emim]Cl = 2), LiCl + [Emim]Br + H2O (mass ratio LiCl/[Emim]Br = 2), and LiBr + [Emim]Cl + H2O (mass ratio LiBr/[Emim]Cl = 2), were measured at a temperature from 314.79 to 435.48, 317.62 to 431.27, and 303.10 to 409.91 K, respectively. The mass fractions of the absorbent are in the range from 0.30 to 0.60. (2) By regressing using the Antoine-type equation, the average absolute relative deviation (AARD %) values between experimental data and calculated value were 0.44, 0.51, and 0.54%, respectively. The comparison between experimental data and calculated data showed good consistency and accuracy. (3) The experimental data proved that the vapor pressures of the three proposed ternary systems (LiCl + [Emim]Cl + H2O, LiCl + [Emim]Br + H2O, and LiBr + [Emim]Cl + H2O) have lower vapor pressures than that of LiBr + [Emim]Ac + H2O. LiCl + [Emim]Cl + H2O had the lowest vapor pressures among the three tested ternary G

DOI: 10.1021/acs.jced.8b01217 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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(12) Zhang, X.; Gao, N.; Wu, Y.; Chen, G. Vapor Pressure Measurement for the Ternary System of Water, Lithium Bromide, and 1-Ethyl-3-methylimidazolium Acetate. J. Chem. Eng. Data 2018, 63, 781−786. (13) Rafiee, H. R.; Frouzesh, F. The study of thermodynamic properties of the ternary (1-ethyl-3-methylimidazolium hydrogen sulfate + lithium chloride + water) system and corresponding binary systems at different temperatures and ambient pressure. J. Chem. Thermodyn. 2016, 102, 95−104. (14) Jing, L.; Zheng, D.; Fan, L.; Wu, X.; Li, D. Vapor Pressure Measurement of the Ternary Systems H2O + LiBr + [Dmim]Cl, H2O + LiBr + [Dmim]BF4, H2O + LiCl + [Dmim]Cl, and H2O + LiCl + [Dmim]BF4. J. Chem. Eng. Data 2011, 56, 97−101. (15) Merkel, N.; Weber, C.; Faust, M.; Schaber, K. Influence of anion and cation on the vapor pressure of binary mixtures of water +ionic liquid and on the thermal stability of the ionic liquid. Fluid Phase Equilib. 2015, 394, 29−37. (16) Freire, M. G.; Santos, L. M. N. B. F.; Fernandes, A. M.; Coutinho, J. A. P.; Marrucho, I. M. An overview of the mutual solubilities of water−imidazolium-based ionic liquids systems. Fluid Phase Equilib. 2007, 261, 449−454. (17) Guo, K.; Bi, Y.; Sun, L.; Su, H.; Hungpu, L. Experiment and Correlation of Vapor−Liquid Equilibrium of Aqueous Solutions of Hydrophilic Ionic Liquids: 1-Ethyl-3-methylimidazolium Acetate and 1-Hexyl-3-methylimidazolium Chloride. J. Chem. Eng. Data 2012, 57, 2243−2251. (18) NIST. Reference Fluid Thermodynamic and Transport Properties Database (REFPROP), version 9.0; NIST, 2010. (19) Clarke, E. C. W.; Glew, D. N. Evaluation of the Thermodynamic Functions for Aqueous Sodium Chloride from Equilibrium and Calorimetric Measurements below 154 °C. J. Phys. Chem. Ref. Data 1985, 14, 489−610.

systems. Lower pressure is more beneficial to the absorption cooling and dehumidification cycles. The VLE properties of IL-based mixtures have a strong dependency on the anion. As better water affinity leads to lower vapor pressure, it can be concluded from these experimental data that under experimental conditions, the water affinity of [Cl]− > [Ac]−, [Cl]− > [Br]−. (4) Comparing the vapor pressure of LiBr + [Emim]Cl + H2O and LiCl + [Emim]Cl + H2O, it can be seen that when using the same ILs, the LiCl aqueous solution system have lower vapor pressure because of its better water absorption ability. (5) The ILs’ ternary systems proposed in this research have potential to be promising alternative working fluids in the absorption cooling system.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Yongmei Xuan: 0000-0002-8100-7612 Funding

This work is financially supported by the National Natural Science Foundation of China (NSFC) (no. 51706167). Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Konwar, D.; Gogoi, T. K. Performance of double effect H2O− LiCl absorption refrigeration systems and comparison with H2O− LiBr systems, Part 1: Energy analysis. Therm. Sci. Eng. Prog. 2018, 8, 184−203. (2) She, X.; Yin, Y.; Xu, M.; Zhang, X. A novel low-grade heat-driven absorption refrigeration system with LiCl−H2O and LiBr−H2O working pairs. Int. J. Refrig. 2015, 58, 219−234. (3) Yokozeki, A.; Shiflett, M. B. Ammonia Solubilities in RoomTemperature Ionic Liquids. Ind. Eng. Chem. Res. 2007, 46, 1605− 1610. (4) Yokozeki, A.; Shiflett, M. B. Vapor−liquid equilibria of ammonia +ionic liquid mixtures. Appl. Energy 2007, 84, 1258−1273. (5) Zheng, D.; Dong, L.; Huang, W.; Wu, X.; Nie, N. A review of imidazolium ionic liquids research and development towards working pair of absorption cycle. Renewable Sustainable Energy Rev. 2014, 37, 47−68. (6) Khamooshi, M.; Parham, K.; Parham, K. Overview of ionic liquids used as working fluids in absorption cycles. Adv. Mech. Eng. 2013, 5, 620592. (7) Huang, W.; Sun, G.; Zheng, D.; Dong, L.; Wu, X.; Chen, J. Vapor−Liquid Equilibrium Measurements of NH3 + H2O + Ionic Liquid ([Dmim]Cl, [Dmim]BF4, and [Dmim]DMP) Systems. J. Chem. Eng. Data 2013, 58, 1354−1360. (8) Cera-Manjarres, A.; Salavera, D.; Coronas, A. Vapour pressure measurements of ammonia/ionic liquids mixtures as suitable alternative working fluids for absorption refrigeration technology. Fluid Phase Equilib. 2018, 476, 48−60. (9) Wang, M.; Becker, T. M.; Infante Ferreira, C. A. Assessment of vapor−liquid equilibrium models for ionic liquid based working pairs in absorption cycles. Int. J. Refrig. 2018, 87, 10−25. (10) Chen, W.; Liang, S.; Guo, Y.; Gui, X.; Tang, D. Investigation on vapor−liquid equilibria for binary systems of metal ion-containing ionic liquid [bmim]Zn2Cl5/NH3 by experiment and modified UNIFAC model. Fluid Phase Equilib. 2013, 360, 1−6. (11) Chen, W.; Liang, S.; Guo, Y.; Tang, D. Thermodynamic analysis of an absorption system using [bmim]Zn2Cl5/NH3 as the working pair. Energy Convers. Manage. 2014, 85, 13−19. H

DOI: 10.1021/acs.jced.8b01217 J. Chem. Eng. Data XXXX, XXX, XXX−XXX