Excess molar volumes and viscosities of poly(ethylene glycol) 300 + water at different temperatures

Fluid Phase Equilibria 313 (2012) 7–10

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Excess molar volumes and viscosities of poly(ethylene glycol) 300 + water at different temperatures Na Zhang a , Jianbin Zhang a,b,∗ , Yongfeng Zhang a,b , Jie Bai a,b , Tianrui Huo a , Xionghui Wei c,∗∗ a b c

College of Chemical Engineering, Inner Mongolia University of Technology, Huhhot 010051, China Insititute of Coal Conversion & Cyclic Economy, Inner Mongolia University of Technology, Huhhot 010051, China Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100190, China

a r t i c l e

i n f o

Article history: Received 31 January 2011 Received in revised form 28 September 2011 Accepted 28 September 2011 Available online 5 October 2011 Keywords: Density Excess molar volume Poly(ethylene glycol) 300 Viscosity

a b s t r a c t Density was measured over the whole concentration range for the binary system of poly(ethylene glycol) 300 (PEG 300) + water at five temperatures from (298.15 to 318.15) K. The density () is fitted to E calculate the excess molar volume (Vm ) and viscosity deviation (). The computed results are fitted to a Redlich–Kister equation to obtain the coefficients and estimate the standard deviations between the E experimental and calculated quantities. The values of Vm for all mixtures are negative, while the values of  are positive over the entire composition range. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved.

1. Introduction Sulfur dioxide (SO2 ), which is one of the main air pollutants in the environment [1,2], mainly comes from the burning of fuels with high sulfur content from 0.03 mg m−3 in the air up to several mg m−3 in a typical flue gas [3]. The removal of SO2 has been seen as an important challenge with the seriously increasing emissions as it can bring harm especially to humans and the environment. Among all of the methods developed, the wet desulfurization method [4] is one of the most important because of its high desulfurization efficiency and ease of obtaining the reagent. However, some disadvantages, such as huge magnitude of capital investment, high operating cost, and secondary pollution caused by the single purpose of the product gypsum, still blocked its development. In recent years, there has been a growing interest in the use of organic solvents for acid gas removal [5,6]. Among the numerous organic solvents, alcohols show favorable absorption and desorption capabilities for the removal of SO2 in the industrial processes [7,8]. Therefore, in a number of studies, great attention has been paid to alcohol + water systems for the SO2 removal [9–14]. This paper is a continuation of the systematic program on the properties of binary solution of ethylene glycol (EG) and its similar

∗ Corresponding author at: College of Chemical Engineering, Inner Mongolia University of Technology, Huhhot 010051, China. Tel.: +86 010 62751529; fax: +86 010 62670662. ∗∗ Corresponding author. Tel.: +86 010 62751529; fax: +86 010 62670662. E-mail addresses: [email protected] (J. Zhang), [email protected] (X. Wei).

complexes + water for the removal of SO2 . Based on the previous work, in order to remove SO2 from flue gas, poly(ethylene glycol) 300 (PEG 300) had been introduced as an important industrial organic solvent because of its favorable properties, such as low vapor pressure, low toxicity, high chemical stability, and low melting point. The physical properties of PEG 300 + water (PEGW) binary system, especially density (), excess molar volume, and viscosity () data, were only partly reported in the previous Refs. [15–19]; however, these physical properties are extremely important for the theoretical viewpoints and application aspects of PEGW in the absorption and desorption processes of SO2 . Therefore, we have to carry out the measurements for densities and viscosities of PEGW. In this work, the density and viscosities of PEG 300 + water were determined over the whole concentration range at the temperature of T = (298.15–318.15) K with a step of 5 K. Meanwhile, the excess molar volume and the deviation of the viscosity were calculated. The peculiarity of this work is used to provide important basic data for the design and operation of the absorption and desorption process in flue gas desulfurization (FGD) with potential industrial application of the solutions containing PEG 300. 2. Experimental 2.1. Materials Analytical grade PEG 300 with the average molecular weight of 300 (280–320) was purchased from Beijing Reagent Company (Beijing, China). PEG 300 was dried over 0.4 nm molecular sieves

0378-3812/$ – see front matter Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.fluid.2011.09.036

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N. Zhang et al. / Fluid Phase Equilibria 313 (2012) 7–10 1.14

Table 1 Comparison of experimental densities (), viscosities (), and kinematic viscosities () of PEG 300 with literature values at various temperatures.

Expt.

Lit.

Expt.

298.15

1.1218

44.906

39.93

303.15 308.15

1.1186 1.1147

1.121634 [15] 1.12236 [16] 1.11877 [15] 1.11505 [15] 1.113497 [16] 1.11328 [17], a 1.11358 [18,19]a 1.11221 [15]

33.477 26.662

29.93 23.92

313.15 318.15 a

1.1115 1.1066

1.12

106  (m2 s−1 )

 (mPa s)

Expt.

1.10

Lit.

1.08 -3

Lit.

ρ/(g cm )

 (g cm−3 )

T (K)

21.323 16.411

1.06 1.04

1.02

19.18 14.83

1.00

PEG 300 (Mn = 274; Mw /Mn = 1.11).

0.98

before measurements, and it was degassed by ultrasound just before the experiment. The solutions of binary mixtures were prepared by distilled water at room temperature. Solvent mixtures were prepared by mass using an analytical balance (Sartorius BS 224S), which shows a precision of ±0.0001 g. The uncertainty in the mole fraction for each binary mixture is less than ±0.0001. Then for each ratio, a series of solutions of different concentrations were made. Meanwhile, distilled water and high-performance liquid chromatography (HPLC) grade ethanol were used. 2.2. Measurements Densities of pure liquids and their mixtures were determined using a calibrated glass pycnometer having a bulb volume of 10 cm3 . The volume of the pycnometer was calibrated as a function of temperature using distilled, deionized, and degassed water at various temperatures [20–22]. The pycnometer filled with liquid was kept in a thermostatically controlled, and well-stirred water bath (maintained constant to ±0.01 K) for (20–25) min to attain thermal equilibrium. The density measurements were carried out at the temperatures of (298.15, 303.15, 308.15, 313.15, and 318.15) K. Each experimental density value was an average of at least three measurements. The uncertainty of the density measurement was estimated to be ±0.02%. The kinematic viscosity in both the pure liquids and their mixtures were performed with a commercial capilary viscometer of the Ubbelohde type, which has a capillary diameter of 0.90 mm. The Ubbelohde type was calibrated with high pure water and ethanol (HPLC grade) at the experimental temperature whose viscosity and density were well-known, as has been described in literatures [20–25] and shown in Table 1. Care was taken to reduce evaporation during the measurements. The flow time was determined with a hand-held digital stopwatch capable of measuring time within ±0.01 s. All the measurements were accomplished in a transparent glass-walled water bath with the thermal stability 0.01 K. Each measurement was repeated at least eighteen times and the results were averaged. The kinematic viscosity () was calculated from the following equation  = At −

B t

(1)

where  is the kinematic viscosity, t is its flow time in the viscometer, and A and B are viscometer constants, respectively. A and B are determined from measurements with the calibration fluids water and ethanol. The absolute viscosity () was obtained by multiplying the determined kinematic viscosity () by the measured density  = . Each experimental point was the average of 16 sets with a maximum deviation of ±0.3% in the flow time.

0.0

0.2

0.4

0.6

0.8

1.0

X1 Fig. 1. Experimental densities with mole fraction for PEG 300 (1) + water (2): , 298.15 K; , 303.15 K; , 308.15 K; + 313.15 K; and ×, 318.15 K.

3. Results and discussion A comparison of present measurements of density and viscosity with the data in the literatures was shown in Table 1. A reasonable agreement was found between this experimental values and those of the literatures [15–19]. Experimental densities under atmospheric pressure for the binary solution of PEG 300 + water over the temperature range from (298.15 to 318.15) K at intervals of 5 K throughout the whole concentration range and the measured densities at different temperatures are plotted in Fig. 1. Fig. 1 shows that the density values increase with the increasing PEG 300 concentration in binary solution over the whole concentration range, and the values quickly increase between x1 = 0 and x1 = 0.2. Meanwhile, at the same concentration, the density values decrease with the increment of temperature. E was calculated from density meaThe excess molar volume Vm surements according to the following equation E = Vm



M1 M2 x1 M1 + x2 M2 − x1 + x2 m 1 2

 (2)

where m is the density of the mixture and x1 , 1 , M1 , x2 , 2 , and M2 are the mole fractions, densities, and molecular weights of the E and the pure PEG 300 and pure water, respectively. The results of Vm E at various temperatures are displayed in Fig. 2. dependence of Vm E values are negative for all the mixtures Fig. 2 shows that the Vm over the entire range of composition with a minimum around molar fraction 0.20 for PEG 300 at all temperatures, as is common for other completely miscible (organic + water) solvents. Additionally, these E values become less negative with the increasing temperatures. Vm The negative indicates that there is a volume contraction on mixing. It can also be observed that this kind of interaction is affected by temperature and composition. A Redlich–Kister relation was used to correlate the excess volume data according to the following equation E Vm (cm3 mol−1 ) = x1 x2

n 

Ai (2x1 − 1)i

(3)

i=0

where x1 is the mole fraction of PEG 300 and x2 is the mole fraction of water; Ai are the polynomial coefficients; and n is the polynomial degree.

N. Zhang et al. / Fluid Phase Equilibria 313 (2012) 7–10

25

0.0

20

-0.8

Δη/(mPa s)

3

-0.4

E

-1

(Vm /(cm mol )

-0.2

-0.6

9

15

10

5

-1.0 -1.2

0 0.0

0.2

0.4

0.6

X1

0.8

1.0

0.0

0.2

0.4

X1

0.6

0.8

1.0

Fig. 2. Excess molar volumes with mole fraction for PEG 300 (1) + water (2): , 298.15 K; , 303.15 K; , 308.15 K; + 313.15 K; and ×, 318.15 K.

Fig. 4. Viscosity deviations with mole fraction for PEG 300 (1) + water (2): , 298.15 K; , 303.15 K; , 308.15 K; + 313.15 K; and ×, 318.15 K.

Table 2 E , for PEG Coefficients and standard deviations of excess molar volumes, Vm 300 + water.

Table 3 Coefficients and standard deviations of viscosity deviations, , for PEG 300 + water.

T (K)

A0

A1

A2

A3

A4

 (cm3 mol−1 )

298.15 313.15 308.15 313.15 318.15

−3.351 −3.337 −3.173 −3.283 −3.249

3.603 2.965 3.411 2.672 2.698

−1.654 −2.037 −1.811 −2.804 −2.293

3.541 5.025 4.337 4.796 3.634

−3.622 −2.937 −2.981 −2.060 −2.945

0.0219 0.0227 0.0187 0.0003 0.0201

The standard deviation values, , between the calculated and experimental data points are obtained by the following equation

 V E =

 (V E − VmE )2 calc

1/2 (4)

N−m

m

where N is the total number of experimental points and m is the number of Ai coefficients considered. The coefficients Ai and corresponding standard deviations, , are listed in Table 2. Experimentally measured viscosities of the binary solutions of PEG 300 + water at (298.15, 303.15, 308.15, 313.15, and 318.15) K are shown in Fig. 3. In all cases, the viscosities increase with the 50

T (K)

B0

B1

B2

B3

B4

 (mPa s−1 )

298.15 313.15 308.15 313.15 318.15

71.39 51.44 39.48 30.94 23.65

−61.40 −46.76 −37.08 −26.01 −20.19

61.21 40.83 35.28 37.19 23.42

67.25 53.81 35.08 23.66 17.949

−143.46 −90.42 −76.73 −68.41 −44.91

0.485 0.339 0.296 0.179 0.177

increasing PEG 300 concentrations and decrease with the increasing temperatures. The experimental values of  for the various mixtures have been used to calculate the viscosity deviation, , defined by  =  − (x1 1 + x2 2 )

where  is the viscosity of the mixture; 1 and 2 are the viscosities of pure PEG 300 and pure water, respectively; and x1 is the mole fraction of PEG 300 and x2 is the mole fraction of water; The results of the viscosity deviation,  are plotted in Fig. 4. Fig. 4 shows that in all cases the  values are positive over the whole composition range for mixtures. The  versus x1 curves shift toward the water-rich region, and the observed results are E results. The viscosity deviations, , decrease similar to the Vm with the increasing temperatures. The viscosity deviations, , were also represented by the Redlich–Kister equation as follows

40

 (mPa s) = x1 x2 30

η/(mPa S)

(5)

n 

Bi (2x1 − 1)i

(6)

i=0

The coefficients Bi and the standard deviation are presented in Table 3.

20

4. Conclusion

10

0 0.0

0.2

0.4

X1

0.6

0.8

1.0

Fig. 3. Experimental viscosities with mole fraction for PEG 300(1) + water (2): , 298.15 K; , 303.15 K; , 308.15 K; + 313.15 K; and ×, 318.15 K.

This paper reports experimental data for the densities and viscosities of the binary system of aqueous PEG 300 solutions over the temperature range from (298.15 to 318.15) K. The data of pure PEG 300 and water are in good agreements with available literature data. These data have been used to compute excess properties of the E values for the aqueous PEG 300 solutions system. The calculated Vm were negative, while the viscosity deviations of the PEG 300 + H2 O system were positive at all temperatures and compositions.

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N. Zhang et al. / Fluid Phase Equilibria 313 (2012) 7–10

Acknowledgments This work was supported by the National Natural Science Foundation of China (21166017), the Natural Science Foundation of Inner Mongolia Autonomous Region (2011BS0601, China), Inner Mongolia Autonomous Region’s Educational Commission (NJ10079), and Yongfeng Boyuan Industry Co., Ltd. (Jiangxi Province, China). References [1] Z.G. Tang, W.Q. Xu, C.C. Zhou, X.C. Lu, Ind. Eng. Chem. Res. 45 (2006) 704–711. [2] L. Philip, M.A. Deshusses, Environ. Sci. Technol. 37 (2003) 1978–1982. [3] M.A. Siddiqi, J. Krissmann, P. Peters-Gerth, P.P. Gerth, M. Luckas, K. Lucas, J. Chem. Thermodyn. 28 (1996) 685–700. [4] X. Gao, R.T. Guo, H.L. Ding, Z.Y. Luo, K.F. Cen, J. Hazard. Mater. 168 (2009) 1059–1064. [5] K. Maneeintr, R.O. Idem, P. Tontiwachwuthikul, A.G.H. Wee, Energy Procedia 1 (2009) 1327–1334. [6] R. De Kermadec, F. Lapicque, D. Roizard, C. Roizard, Ind. Eng. Chem. Res. 41 (2002) 153–163. [7] C.N. Schubert, W.I. Echter, The Method of Polymer Ethylene Glycol for Removal Pollution from Gases, CN. Patent 1364096A (2002). [8] J.B. Zhang, P.Y. Zhang, G.H. Chen, F. Han, X.H. Wei, J. Chem. Eng. Data 53 (2008) 1479–1485.

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