Densities and viscosities of 1-propyl-2,3-dimethylimidazolium tetrafluoroborate + H2O at T = (298.15 to 343.15) K

Article abstract of DOI:10.1021/je800965t

Experimental data of densities and viscosities of l-propyl-2,3- dimethylimidazolium tetrafluoroborate ([PDMIM][BF₄]) + H₂O binary mixtures were measured over the entire mole fraction range from (298.15 to 343.15) K at atmospheric pre

Full text of DOI:10.1021/je800965t

1400
J. Chem. Eng. Data 2009, 54, 1400–1402
Densities and Viscosities of 1-Propyl-2,3-dimethylimidazolium Tetrafluoroborate +
H2O at T ) (298.15 to 343.15) K
Ming-Lan Ge,*,† Xiao-Guang Ren,† Yong-Ji Song,† and Li-Sheng Wang‡
Department of Chemical Engineering, Beijing Institute of Petrochemical Technology, Beijing 102617, People’s Republic of
China, and School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing 100081,
People’s Republic of China
Experimental data of densities and viscosities of 1-propyl-2,3-dimethylimidazolium tetrafluoroborate
([PDMIM][BF4]) + H2O binary mixtures were measured over the entire mole fraction range from (298.15
to 343.15) K at atmospheric pressure. Excess molar volumes and viscosity deviations as a function of mole
fraction average have been obtained and fitted to the Redlich-Kister equation. Estimated coefficients of the
Redlich-Kister equation and standard error calculated from the Redlich-Kister equation to the experimental
data were also presented.
Table 1. Experimental Densities, G, for Binary Mixture of H2O (1)
Introduction
+ [PDMIM][BF4] (2)
Ionic liquids (ILs) have been receiving increasing interest as
T/K
environmental friendly solvents recently because of their unique
physical and chemical properties.1-4 For ILs to be used
effectively as solvents, it is essential to know the thermodynamic
and thermophysical properties of ILs and, in particular, of
mixtures containing ILs.5,6 This work continues our studies on
the determination of the densities and viscosities of IL + H2O
binary mixtures.7,8
x1
298.15 303.15 308.15 313.15 318.15 323.15 333.15 343.15
F/g · cm-3
0.0000 1.2251 1.2218 1.2188 1.2174 1.2162 1.2154 1.2134 1.2119
0.0939 1.2219 1.2179 1.2148 1.2132 1.2119 1.2110 1.2089 1.2071
0.1932 1.2180 1.2140 1.2108 1.2093 1.2079 1.2068 1.2044 1.2026
0.2833 1.2136 1.2097 1.2065 1.2048 1.2032 1.2021 1.1997 1.1978
0.3944 1.2074 1.2037 1.2002 1.1982 1.1968 1.1956 1.1932 1.1912
0.4987 1.1998 1.1960 1.1926 1.1906 1.1890 1.1878 1.1853 1.1831
0.5995 1.1896 1.1861 1.1825 1.1805 1.1789 1.1776 1.1747 1.1723
0.6985 1.1757 1.1717 1.1683 1.1665 1.1650 1.1637 1.1607 1.1579
0.8009 1.1535 1.1499 1.1469 1.1447 1.1431 1.1417 1.1384 1.1343
0.8988 1.1130 1.1098 1.1074 1.1053 1.1033 1.1016 1.0978 1.0942
1.0000 0.9970 0.9957 0.9940 0.9922 0.9902 0.9881 0.9832 0.9778
1-Propyl-2,3-dimethylimidazolium tetrafluoroborate ([PD-
MIM][BF4], CAS no. 157310-72-0) is one of the air- and water-
stable hydrophilic ILs and is also thermally stable. The activity
coefficient γ∞i data of 34 organic solutes in [PDMIM][BF4] from
(303.15 to 363.15) K have been measured in our previous
works.9,10 However, no experimental density and viscosity data
of the mixtures of [PDMIM][BF4] and water have been reported
in the previous literature. In this work, the densities and
viscosities of mixtures consisting of [PDMIM][BF4] and water
were measured over the entire range of their compositions from
(298.15 to 343.15) K. The excess molar volume, VE, and
viscosity deviation, ∆η, of this binary system have been obtained
and fitted to the Redlich-Kister equation.
amount of cooled deionized water five times until the aqueous
solution did not form any precipitate with AgNO3 solution. The
solvent dichloromethane was removed by rotary evaporation,
and the [PDMIM][BF4] was dried under high vacuum at 343 K
for 8 h to remove volatile impurities. Water mass fractions
analyzed by Karl Fischer analysis were less than 10-3. The
1
chemical shifts for the H NMR spectrum (δ, D2O) appear as
follows: 7.245 [s, 1H, H(4)], 7.216 [s, 1H, H(5)], 3.997 [t, 2H,
NCH2], 3.670 [s, 3H, NCH3], 2.487 [s, 3H, CH3], 1.760 [m,
2H, NCH2-CH2], and 0.840 [t, 3H, NCH2CH2-CH2-CH3].
Impurity peaks were not observed in the 1H NMR spectra. The
purity of the IL was > 99 %. The change in the pH value of
this IL between room temperature and 343 K was less than 1
%. This phenomenon showed that this IL will not hydrolyze at
343 K. Before use, the IL was subjected to vacuum evaporation
at (323 to 333) K over 24 h to remove possible traces of solvents
and moisture.
Apparatus and Procedure. The measurements apparatus and
procedure have been described in our previous work.7,8 The
mixtures of IL + H2O were prepared by mass. A TE2101-L
electronic digital balance accurate to within ( 0.1 mg was used.
The uncertainty in the mole fraction of the mixtures was
estimated to less than ( 0.0001. All molar quantities are based
on the IUPAC 2005 relative atomic mass table.12 The densities
of [PDMIM][BF4] and its mixtures were measured with a
Experimental Section
Materials. In this work, all of the aqueous solutions were
prepared with deionized water, and the chemicals for preparation
of [PDMIM][BF4] were of analytical grade and used without
further purification. [PDMIM][BF4] was prepared via the
traditional two steps.11 First, 1-propyl-2,3-dimethylimidazolium
bromide [PDMIM][Br] was prepared via the reaction of 1,2-
dimethylimidazole (0.1 mol) and 1-bromopropane (0.11 mol).
Second, [PDMIM][BF4] was synthesized by metathesis reactions
from [PDMIM][Br] and NaBF4 in water. The NaBr precipitate
was removed by filtration, and the remaining water was removed
by rotary evaporation. The crude product was dissolved in
dichloromethane, and the solution was washed with a small
* Corresponding author. E-mail: geminglan@bipt.edu.cn.
† Beijing Institute of Petrochemical Technology.
‡ Beijing Institute of Technology.
10.1021/je800965t CCC: $40.75
2009 American Chemical Society
Published on Web 03/02/2009

Journal of Chemical & Engineering Data, Vol. 54, No. 4, 2009 1401
Table 2. Experimental Viscosities, η, for Binary Mixture of H2O (1)
+ [PDMIM][BF4] (2)
T/K
x1
298.15 303.15 308.15 313.15 318.15 323.15 333.15 343.15
η/mPa · s
0.0000 377.28 271.90 201.99 152.20 117.44 92.29 60.45 40.74
0.0939 224.97 167.61 127.89 99.34 78.56 63.30 42.52 29.96
0.1932 134.95 103.29 81.12 64.54 52.07 42.80 34.62 21.84
0.2833 85.25 66.81 53.23 43.20 35.71 29.65 21.37 16.02
0.3944 50.58 40.44 32.95 27.18 22.79 19.32 14.38 11.04
0.4987 31.29 25.50 21.07 17.63 14.97 12.87
9.78
6.65
4.37
2.62
1.39
0.47
7.66
5.30
3.53
2.15
1.16
0.40
0.5995 19.71 16.21 13.58 11.52
9.88
6.34
3.71
1.89
0.60
8.58
5.55
3.29
1.69
0.55
0.6985 12.03 10.04
8.53
4.90
2.42
0.72
7.31
4.23
2.14
0.65
0.8009
0.8988
1.0000
6.69
3.23
0.89
5.67
2.78
0.80
Figure 1. Excess molar volume, VE, versus molar fraction of water for H2O
(1) + [PDMIM][BF4] (2). 9, 298.15 K; O, 303.15 K; 2, 308.15 K; 4,
313.15 K; b, 318.15 K; 3, 323.15 K; 1, 333.15 K; ×, 343.15 K. The
symbols represent experimental values; the solid curves are calculated with
the Redlich-Kister equation.
Table 3. Excess Molar Volume, VE, for Binary Mixture of H2O (1)
+ [PDMIM][BF4] (2)
T/K
x1
298.15 303.15 308.15 313.15 318.15 323.15 333.15 343.15
V E/cm3 · mol-1
0.0939 0.13
0.1932 0.24
0.2833 0.33
0.3944 0.39
0.4987 0.42
0.5995 0.45
0.6985 0.42
0.8009 0.31
0.8988 0.19
0.22
0.33
0.41
0.45
0.49
0.48
0.48
0.36
0.21
0.24
0.36
0.44
0.50
0.53
0.54
0.52
0.38
0.22
0.27
0.37
0.48
0.57
0.59
0.58
0.54
0.41
0.23
0.28
0.40
0.53
0.58
0.61
0.61
0.55
0.41
0.24
0.29
0.43
0.55
0.61
0.62
0.62
0.57
0.42
0.25
0.31
0.47
0.59
0.63
0.65
0.66
0.59
0.44
0.26
0.34
0.50
0.61
0.66
0.68
0.69
0.62
0.50
0.27
Table 4. Viscosity Deviation, ∆η, for Binary Mixture of H2O (1) +
[PDMIM][BF4] (2)
T/K
x1
298.15 303.15 308.15 313.15 318.15 323.15 333.15 343.15
∆η/mPa · s
0.0939 -117.0 -78.8 -55.2 -38.6 -27.9 -20.4 -12.3 -7.0
0.1932 -169.6 -116.2 -82.0 -58.4 -42.8 -31.8 -17.2 -11.1
0.2833 -185.4 -128.3 -91.7 -66.1 -48.6 -36.7 -22.1 -13.3
0.3944 -178.3 -124.5 -89.7 -65.2 -48.6 -36.8 -22.4 -13.8
0.4987 -158.3 -111.2 -80.5 -59.0 -44.2 -33.7 -20.8 -13.0
0.5995 -131.9 -93.2 -67.8 -49.8 -37.5 -28.7 -17.8 -11.3
0.6985 -102.3 -72.5 -52.9 -39.0 -29.5 -22.7 -14.2 -9.0
Figure 2. Viscosity deviation, ∆η, versus molar fraction of water for H2O
(1) + [PDMIM][BF4] (2). 9, 298.15 K; O, 303.15 K; 2, 308.15 K; 4,
313.15 K; b, 318.15 K; 3, 323.15 K; 1, 333.15 K; ×, 343.15K. The
symbols represent experimental values; the solid curves are calculated with
the Redlich-Kister equation.
0.8009 -69.1 -49.1 -35.9 -26.6 -20.2 -15.5 -9.8
0.8988 -35.8 -25.5 -18.7 -13.8 -10.5 -8.1 -5.1
-6.3
-3.3
Table 5. Coefficients of the Redlich-Kister Equation for VE and
∆η of the H2O (1) + [PDMIM][BF4] (2) System
pycnometer (10 mL), and because its volume varied with
temperature, it was calibrated with pure water from (298.15 to
343.15) K. The temperature was controlled by a water bath to
within an uncertainty of ( 0.05 K. The capillary was calibrated
for kinetic energy and end corrections with double-distilled water
over the experimental temperature range
property
V E/cm3 ·mol-1 298.15
303.15
T/K
A0
A1
A2
A3
σ
1.77
0.53
0.45
0.40
0.28
0.02
0.09
0.16
0.27
0.03 -0.36 0.011
0.84 -0.98 0.011
0.76 -1.00 0.020
0.49 -0.75 0.023
0.45 -0.32 0.028
0.56 -0.45 0.028
0.72 -0.73 0.030
1.16 -1.11 0.025
1.95
2.14
2.44
2.53
2.55
2.64
2.72
308.15
313.15
318.15
323.15
333.15
343.15
298.15 -628.9
303.15 -442.5
308.15 -320.8
313.15 -235.2
318.15 -176.2
323.15 -134.5
333.15
343.15
η
F
∆η/mPa·s
462.5
-362.3
-230.0
-151.3
-97.6
-65.8
-43.9
-6.5
210.1
123.4
75.9
42.7
27.1
13.6
0.3
0.99
0.54
0.43
0.26
0.14
0.10
0.48
0.07
ν ) ) k1t - k2/t
(1)
315.1
221.1
156.3
112.2
83.0
where t is the flow time, k1, is the Ubbelhode capillary
microviscometer constant, and k2 is the Hagenbach correction.
The kinematic viscosity, ν, for calibration was obtained from
literature values of the absolute viscosity and density.13 An
electronic digital stopwatch with a readability of ( 0.01 s was
used for flow-time measurement. Experiments were repeated
at least four times at each temperature for all mixtures, and the
results were averaged. The uncertainty of viscosity measure-
ments depends on equilibrium temperature, flow time, mole
fraction, and calibration fluid.
-83.2
-51.7
40.7
25.9
-10.5
2.5
to be about ( 1 %. Accordingly, the relative deviations of VE
and ∆η were estimated to be about ( 2 %.
Result and Discussion
The densities and viscosities of the [PDMIM][BF4] + H2O
mixture, as a function of water content over the temperature
range from (298.15 to 343.15) K, are presented in Tables 1 and
From a propagation of error analysis, the experimental
average uncertainties of density and viscosity were estimated

1402 Journal of Chemical & Engineering Data, Vol. 54, No. 4, 2009
2. An increase in water content or temperature causes density
or viscosity to decrease.
properties of ILs for binary system of H2O + [PDMIM][BF4].
Furthermore, the present results add useful data on imidazolium-
based ILs to the growing database on IL properties, a database
that is essential for the many applications of these liquids
currently under exploration.
The excess molar volumes, VE, and the viscosity deviations,
∆η, were calculated from the measurements according to the
following equations14,15
x1M1 + x2M2
x1M1
x2M2
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∆η ) η - (x1η1 + x2η2)
where F and η are density and viscosity of mixtures, respec-
tively, x1 and x2 are mole fractions, M1 and M2 are molar masses,
F1 and F2 are densities, and η1 and η2 are the viscosities of H2O
(1) and [PDMIM][BF4] (2), respectively.
All values of VE and ∆η for the mixtures of H2O (1) +
[PDMIM][BF4] (2) were fitted to the Redlich-Kister polynomi-
nal equation16,17
m-1
Y ) x (1 - x )
A (2x - 1)i
(4)
∑
1
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i
1
i)0
where Y ) VE or ∆η, Ai is adjustable parameter, and x1 is the
mole fraction of water (1). The optimum number of coefficients,
Ai, was determined from an examination of variation of standard
derivation
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∑
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where n is the number of experimental data and m is the number
of coefficients of the Redlich-Kister equation.
The data of excess molar volume, VE, and viscosity deviation,
∆η, are given in Tables 3 and 4. The VE and the ∆η versus the
mole fraction of water are, respectively, shown in Figures 1
and 2. Table 5 lists the value of the parameters, Ai, together
with the standard deviations.
The excess thermodynamic properties, which depend on the
composition, temperature, or both, are of great importance in
understanding the nature of molecular interaction that exists in
the binary mixtures. As shown in Figure 1, the values of V E
were positive for H2O + [PDMIM][BF4] mixtures from (298.15
to 343.15) K over the entire range of composition s and increase
slightly with the increase in temperature.
The dependence of ∆η on mole fraction, x1, is presented in
Figure 2. The values of viscosity deviations were negative over
the whole range of composition, and the minimum existed at
x1 ) 0.3 within the whole region of experimental temperatures.
Simultaneously, viscosity deviations increased slightly from
(298.15 to 343.15) K.
Received for review December 15, 2008. Accepted February 5, 2009.
This work was supported by Beijing Municipal Organization Department
Training Programme for the Excellent Talents (grant no.
20081D0500500140).
Conclusions
The experimental results show that water content has stronger
effects on the physical properties and excess thermodynamic
JE800965T