Density, Viscosity, and Freezing Point for Four Binary Systems of n

Article pubs.acs.org/jced

Density, Viscosity, and Freezing Point for Four Binary Systems of n‑Dodecane or Methylcyclohexane Mixed with 1‑Heptanol or Cyclohexylmethanol Jing Zhao,† Jianzhou Wu,† Yitong Dai,† Xinxin Cheng,† Haiyun Sun,‡ Yongsheng Guo,*,† and Wenjun Fang† †

Department of Chemistry, Zhejiang University, Hangzhou 310027, China Beijing Key Laboratory of Research and Application for Aerospace Green Propellants, Beijing Institute of Aerospace Testing Technology, Beijing 100000, China

‡

S Supporting Information *

ABSTRACT: Measurements on density and viscosity at T = (293.15, 298.15, 303.15, 308.15 313.15, 318.15, 323.15, 328.15, and 333.15) K and the pressure P = 0.1 MPa for binary mixtures of n-dodecane or methylcyclohexane with 1-heptanol or cyclohexylmethanol have been carried out over the whole composition range. Densities were measured with a vibrating-tube densimeter. Viscosities were determined by an automatic microviscometer based on the rolling-ball principle. The excess molar volumes (VEm) and viscosity deviations (Δη) were calculated with experimental data and fitted to the Redlich−Kister equation. The results of these excess or deviation functions are explained by molecular interactions and structural effects. Freezing points were measured with a differential scanning calorimeter. The fundamental data, VEm and Δη can be used to study the nature of mixing behaviors between new hydrocarbon fuels.

1. INTRODUCTION Thermodynamic and transport properties of liquid mixtures are important in chemical engineering applications such as the calculation of fluid mechanics, heat and mass transfer, and design of process equipment.1,2 Density, as a volumetric property, is related to the energy density of hydrocarbon fuels. Viscosity, as a transport property, is important to the heat and mass transportation of hydrocarbon fuels. Meanwhile, freezing point is a significant parameter, which can reflect the property of hydrocarbon fuels at low temperature. Hence, these fundamental data play an essential role in evaluating the performance of hydrocarbon fuels. Jet fuel is made up of hundreds of hydrocarbon compounds. n-Alkanes and cycloalkanes with alkyl chains are the most important main components of jet fuels.3 n-Alkanes are significant for low-temperature combustion owing to the shorter ignition delays than isoalkanes and aromatics with similar molecular weight.4 Alkyl-cycloalkane, like methylcyclohexane, ethylcyclohexane, and n-butylcyclohexane, is constantly suggested as a model component to represent the naphthene content of real fuels.5 n-Dodecane and methylcyclohexane as the representative linear alkane and alkylated cycloalkane are chosen for present study. As a consequence of environmental, economical, and safety concerns, adding additives to hydrocarbon fuels has attracted much attention. Among those additives, alcohol is considered as a good option. For example, some aliphatic alcohols are added to hydrocarbon fuels to reduce pollution and improve combustion performance in such © 2017 American Chemical Society

properties as octane number, heat of vaporization, and flammability limit.6 1-Heptanol and cyclohexylmethanol are chosen as linear and cyclic alcohols mixed with n-dodecane or methylcyclohexane for models of liquid mixtures. In the present work, the densities, viscosities, and freezing points of a series of binary mixtures of n-dodecane or methylcyclohexane with 1-heptanol or cyclohexylmethanol were measured. More specifically, the excess molar volumes and the viscosity deviations of the four binary systems were calculated. The experimental data and calculated results were important for understanding the physical properties of new hydrocarbon fuels and molecular interactions between mixture components.

2. EXPERIMENTAL SECTION 2.1. Materials. The sample of n-dodecane (CAS no. 11240-3, ω ≥ 0.99), methylcyclohexane (CAS no. 108-87-2, ω ≥ 0.99), 1-heptanol (CAS no. 111-70-6, ω ≥ 0.99), and cyclohexylmethanol (CAS no. 100-49-2, ω ≥ 0.99) were obtained from Aladdin Industrial Corporation, Shanghai, China. The purities of all the reagents are checked by GCMS (7890A/5975C, Agilent). The detailed information on Received: July 30, 2016 Accepted: January 16, 2017 Published: January 27, 2017 643

DOI: 10.1021/acs.jced.6b00688 J. Chem. Eng. Data 2017, 62, 643−652

Journal of Chemical & Engineering Data

Article

Table 1. Specifications of the Chemicals Used in This Work name

source

provided mass fraction purity

purification method

measured mass fraction purity

analysis method

n-dodecane methylcyclohexane 1-heptanol cyclohexylmethanol

Aladdin Aladdin Aladdin Aladdin

≥0.99 ≥0.99 ≥0.99 ≥0.99

none none none none

0.992 0.996 0.999 0.994

GC−MS GC−MS GC−MS GC−MS

Table 2. Densities (ρ) and Viscosities (η) of Pure Compounds Used in This Work Compared with Literature Data at Corresponding Temperatures and Atmospheric Pressure P = 0.1 MPaa T/K

expt

lit.

η /mPa·s

% AARD

ρ/g·cm−3 293.15 298.15 303.15

0.74882 0.74520 0.74157

308.15 313.15 318.15 323.15 328.15 333.15

0.73794 0.73430 0.73064 0.72698 0.72331 0.71964

293.15 298.15 303.15

0.76933 0.76500 0.76067

308.15 313.15 318.15 323.15 328.15 333.15

0.75632 0.75195 0.74756 0.74315 0.73873 0.73428

293.15 298.15

0.82224 0.81874

303.15 308.15 313.15 318.15 323.15 328.15 333.15

0.81522 0.81168 0.80811 0.80452 0.80088 0.79720 0.79349

293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15

0.92996 0.92643 0.92287 0.91928 0.91566 0.91200 0.90831 0.90457 0.90078

n-Dodecane 0.74892b, 0.74900c, 0.74889d, 0.74874f 0.74517b, 0.74538c, 0.7453e, 0.74514f 0.74166b, 0.74175c, 0.74163d, 0.7415e, 0.74152f 0.73795b, 0.73812c, 0.7378e, 0.73788f 0.73438b, 0.73448c, 0.73434d, 0.73424f 0.73069b, 0.73060f 0.72707b, 0.72703d, 0.72695f 0.72356b, 0.72329e, 0.72329f 0.71973b, 0.71969d Methylcyclohexane 0.76935i, 0.7693j, 0.769m 0.76505i, 0.7650k, 0.76071i, 0.7607j, 0.7607k, 0.76039l, 0.7604m 0.75637i, 0.7563j, 0.7563k 0.75200i, 0.7519j, 0.7517m 0.74758i 0.74317i, 0.7431j, 0.74250l, 0.7429m i

m

0.73429 , 0.7339 1-Heptanol 0.82228o, 0.8223r 0.81879o, 0.818732p, 0.8187q, 0.8188r, 0.81881u 0.81528o, 0.815287p, 0.8153r 0.81170o, 0.811737p, 0.8118r, 0.81173u 0.80816o, 0.808162p, 0.8080q, 0.8082r 0.80456o, 0.8046r, 0.80455u 0.80092o, 0.8010r 0.79724o, 0.7974r, 0.79722u, 0.79352o, 0.7933q Cyclohexylmethanol 0.92976o 0.92625o 0.92271o 0.91914o 0.91553o 0.91188o 0.90819o 0.90445o 0.90067o

0.014 0.012 0.012 0.013 0.012 0.006 0.008 0.019 0.010 0.016 0.003 0.017 0.005 0.016 0.003 0.033 0.027 0.006 0.006 0.008 0.008 0.009 0.006 0.010 0.011 0.014 0.022 0.019 0.017 0.015 0.014 0.013 0.013 0.013 0.012

293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15

1.485 1.359 1.250 1.155 1.073 0.998 0.932 0.873 0.819

293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15

0.727 0.681 0.640 0.604 0.571 0.542 0.515 0.491 0.469

293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15

6.890 5.805 4.941 4.233 3.648 3.165 2.762 2.423 2.137

293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15

36.959 28.353 22.043 17.320 13.827 11.143 9.099 7.521 6.283

n-Dodecane 1.489b, 1.500c, 1.49d, 1.468h 1.359b, 1.376c, 1.330e, 1.3528g 1.246b, 1.265c, 1.218e, 1.25d 1.148b, 1.167c, 1.122e 1.061b, 1.081c, 1.06d, 1.057h 0.984b, 0.987f 0.916b, 0.9260g 0.855b 0.800b, 0.799d, 0.805h Methylcyclohexane 0.735i, 0.7293n 0.692i, 0.676k, 0.6827n 0.651i, 0.631k, 0.639l, 0.6385n 0.615i, 0.590k, 0.5997n 0.580i 0.549i 0.522i, 0.501l 0.476i

0.691 0.969 1.034 1.526 1.153 1.423 1.197 2.105 2.206 0.702 0.859 0.877 1.626 1.552 1.275 2.068 1.471

1-Heptanol 6.887o, 7.026s 5.812o, 5.944p, 5.947s, 5.744t, 5.851u 4.950o, 5.069p, 5.041s 4.245o, 4.333p, 4.263t, 4.26u 3.654o, 3.726p 3.170o, 3.184u, 3.156t 2.768o, 2.428o, 2.364t, 2.434u 2.141o Cyclohexylmethanol 37.751o 28.67o 22.339o 17.573o 14.093o 11.429o 9.354o 7.766o 6.462o

0.990 1.339 1.564 0.982 1.129 0.347 0.217 1.051 0.187 2.098 1.106 1.325 1.440 1.887 2.502 2.726 3.155 2.770

a

Standard uncertainties u(T) = 0.01 K, u(p) = 1000 Pa, ur(ρ) = 0.001, ur(η) = 0.01. bReference 16. cReference 3. dReference 17. eReference 18. fReference 19. gReference 20. hReference 21. iReference 22. j Reference 23. kReference 24. lReference 25. mReference 26. n Reference 27. oReference 28. pReference 29. qReference 30. r Reference 1. sReference 31. tReference 32. uReference 33.

these chemicals are shown in Table.1. All of these reagents are adopted without further purification. 2.2. Methods. The binary mixtures are prepared by mass with an analytical balance (Mettler Toledo AL204) with an uncertainty of 0.0001 g.

The densities are measured by a vibrating-tube densimeter (Anton Paar, model DMA 5000M, Wundshuh, Austria) at a temperature range from T = (293.15 to 333.15) K and atmospheric pressure P = 0.1 MPa. Dry air and double-distilled water are used to calibrate the densimeter. The accuracy of 644



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Table 3. Densities at Different Mole Fractions (x1) for the Binary Mixtures of n-Dodecane (1) + 1-Heptanol (2), n-Dodecane (1) + Cyclohexylmethanol (2), Methylcyclohexane (1) + 1-Heptanol (2), Methylcyclohexane (1) + Cyclohexylmethanol (2) at Temperatures from T = (293.15 to 333.15) K and Atmospheric Pressure P = 0.1 MPaa ρ/g·cm−3 x1

a

293.15 K

298.15 K

0.0998 0.2005 0.3020 0.3991 0.4989 0.5994 0.6975 0.7959 0.8984

0.81076 0.80065 0.79128 0.78340 0.77602 0.76940 0.76354 0.75820 0.75319

0.80724 0.79707 0.78766 0.77977 0.77237 0.76574 0.75988 0.75454 0.74953

0.1014 0.1991 0.2990 0.3997 0.4992 0.6005 0.7008 0.7986 0.8996

0.89817 0.87204 0.84906 0.82881 0.81130 0.79557 0.78183 0.76990 0.75873

0.89459 0.86846 0.84544 0.82518 0.80771 0.79192 0.77816 0.76622 0.75505

0.1004 0.1991 0.3134 0.3990 0.4994 0.5997 0.6987 0.7995 0.8995

0.81738 0.81234 0.80643 0.80191 0.79651 0.79098 0.78557 0.77994 0.77456

0.81381 0.80871 0.80270 0.79810 0.79262 0.78700 0.78149 0.77577 0.77030

0.0998 0.1996 0.2999 0.3998 0.5004 0.6007 0.6997 0.7984 0.9012

0.91404 0.89807 0.88182 0.86556 0.84897 0.83261 0.81664 0.80082 0.78455

0.91042 0.89434 0.87799 0.86158 0.84491 0.82851 0.81248 0.79658 0.78024

303.15 K

308.15 K

313.15 K

318.15 K

n-Dodecane (1) + 1-Heptanol (2) 0.80368 0.80009 0.79648 0.79281 0.79346 0.78982 0.78616 0.78246 0.78402 0.78035 0.77666 0.77294 0.77611 0.77242 0.76872 0.76498 0.76869 0.76500 0.76128 0.75754 0.76206 0.75835 0.75463 0.75088 0.75619 0.75248 0.74876 0.74501 0.75085 0.74714 0.74342 0.73967 0.74585 0.74215 0.73843 0.73471 n-Dodecane (1) + Cyclohexylmethanol (2) 0.89099 0.88735 0.88369 0.87999 0.86486 0.86123 0.85757 0.85391 0.84179 0.83808 0.83437 0.83077 0.82150 0.81779 0.81407 0.81031 0.80402 0.80032 0.79659 0.79283 0.78823 0.78452 0.78079 0.77704 0.77447 0.77076 0.76703 0.76328 0.76253 0.75882 0.75509 0.75135 0.75137 0.74767 0.74396 0.74024 Methylcyclohexane (1) + 1-Heptanol (2) 0.81021 0.80659 0.80294 0.79926 0.80504 0.80133 0.79760 0.79383 0.79892 0.79512 0.79130 0.78742 0.79425 0.79037 0.78647 0.78253 0.78868 0.78472 0.78073 0.77670 0.78298 0.77893 0.77485 0.77074 0.77738 0.77324 0.76907 0.76487 0.77156 0.76732 0.76306 0.75876 0.76600 0.76167 0.75731 0.75293 Methylcyclohexane (1) + Cyclohexylmethanol (2) 0.90677 0.90308 0.89936 0.89560 0.89057 0.88677 0.88293 0.87905 0.87413 0.87024 0.86631 0.86235 0.85762 0.85363 0.84961 0.84556 0.84088 0.83692 0.83282 0.82869 0.82438 0.82024 0.81606 0.81186 0.80829 0.80407 0.79982 0.79554 0.79232 0.78803 0.78371 0.77936 0.77591 0.77156 0.76717 0.76276

323.15 K

328.15 K

333.15 K

0.78912 0.77874 0.76919 0.76122 0.75377 0.74711 0.74123 0.73590 0.73096

0.78539 0.77497 0.76540 0.75743 0.74997 0.74331 0.73744 0.73212 0.72721

0.78162 0.77118 0.76159 0.75360 0.74614 0.73949 0.73361 0.72831 0.72343

0.87625 0.85016 0.82701 0.80653 0.78905 0.77326 0.75951 0.74758 0.73650

0.87247 0.84636 0.82320 0.80271 0.78524 0.76945 0.75571 0.74379 0.73274

0.86864 0.84252 0.81935 0.79887 0.78141 0.76562 0.75189 0.73998 0.72897

0.79554 0.79003 0.78352 0.77855 0.77264 0.76659 0.76064 0.75443 0.74852

0.79178 0.78618 0.77958 0.77454 0.76855 0.76241 0.75636 0.75006 0.74407

0.78798 0.78230 0.77560 0.77050 0.76442 0.75817 0.75205 0.74566 0.73959

0.89181 0.87515 0.85835 0.84147 0.82452 0.80762 0.79123 0.77499 0.75833

0.88797 0.87124 0.85431 0.83735 0.82032 0.80335 0.78689 0.77058 0.75386

0.88409 0.86726 0.85023 0.83314 0.81609 0.79905 0.78243 0.76613 0.74937

Standard uncertainties u are u(x) = 0.0001, u(p) = 1000 Pa, u(T) = 0.01 K, ur(ρ) = 0.001

temperature is ±0.01 K, and the relative standard uncertainty of density is 0.001. The viscosities are determined by an automatic microviscometer (Anton Paar, model AMVn) at different temperatures from T = (293.15 to 333.15) K and atmospheric pressure P = 0.1 MPa. The rolling ball principle is used in the measurement of viscosities, and the viscosity values are calculated in the following equation

η = k(ρball − ρ)t

is shorter than 200 s, the tube with 1.6 mm diameter is chosen and k is 0.01059. When the efflux time of the sample is longer than 200 s, the tube with 1.8 mm diameter is chosen and k is 0.15342. The relative standard uncertainty of viscosity is 0.01. The freezing points are measured through a differential scanning calorimeter (DSC; TA Instruments, Q2000, New Castle, DE, USA). The calibration of temperature is undertaken with indium (ω = 0.99, purchased from TA Instruments). The sample is sealed in a Tzero pan and scanned for cooling at a constant rate as reported previously.7 The measurement of each sample is carried out under a dry nitrogen atmosphere at a flow rate of 50 mL/min.

(1)

where k is a constant of the viscometer, ρball is the density of rolling ball, ρ is the density of the sample, and t is the averaged efflux time of the sample. There are two kinds of capillary/ball with different diameters (1.6 mm and 1.8 mm) used in the measurements of viscosities. When the efflux time of the sample 645



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3. RESULTS AND DISCUSSION The experimental data of densities and viscosities of the pure samples used in this work at corresponding temperatures and 0.1 MPa are compared with the literature data in Table 2. The percent absolute average relative deviations (%AARD) are calculated by the following equation: n

%AARD = (100/n) ×

∑ i=1

|Plit − P| |Plit|

(2)

where Plit represents the experimental value of the literature and P stands for the measured property. The deviations between the literature data and experimental data of densities and viscosities are in acceptable agreement. The results for the binary systems of n-dodecane, methylcyclohexane with 1-heptanol or cyclohexylmethanol are provided and discussed in the following parts. 3.1. Volumetric Properties. The measured densities for the four binary systems at temperatures from T = (293.15 to 333.15) K and at pressure P = 0.1 MPa are listed in Table 3. The excess molar volumes (VEm) for the four binary systems are calculated using the following equation: VmE =

M1x1 + M 2x 2 ⎛ M1x1 Mx ⎞ − ⎜⎜ + 2 2 ⎟⎟ ρm ρ2 ⎠ ⎝ ρ1

(3)

where M1 and M2 are the mole masses, x1 and x2 are the mole fractions, and ρ1 and ρ2 are the densities of pure components 1 and 2, respectively. ρm is the density of the binary mixture. The values and uncertainty of VmE for the four systems at temperatures from T = (293.15 to 333.15) K are listed in detail in Table S1 of Supporting Information. The excess molar volumes of the binary systems are fitted to the Redlich−Kister polynomial equation: n

Y = x1(1 − x1) ∑ Ai (2x1 − 1)i i=0

(4)

where x1 is the mole fractions. The values of Ai are determined by using the least-squares regression method and are summarized in Table S3, together with the standard deviation (σ), which is defined as follows: ⎡ ∑ (Y − Y )2 ⎤1/2 i cal ⎥ σ=⎢ ⎣ (n − k ) ⎦

(5)

where n is the number of experimental data points and k is the number of fitted parameters. Figure 1 shows comparisons of physical properties obtained in this work with literature values8,9 for methylcyclohexane +1heptanol at 298.15 and 303.15 K. Figure 1 panels a and b illustrate that the experimental values of density in this work are in good agreement with density data reported. Subsequently, Figure 1 panels c and d present comparisons of the excess molar volumes calculated in this work with literature values.8,9 In Figure 1c, the VEm values from this work are in good agreement with the literature values at 298.15 K. Figure 1d shows that the values of VEm from this work and the literature have similar trends for methylcyclohexane +1-heptanol at 303.15 K. A comparison of the densities of pure samples in this work with those from the literature shows that the maximum deviation is 0.012%. The slight increase in the density value leads to a significant change in the derived value of VEm.10 Figure

Figure 1. Comparisons of physical properties obtained in this work with literature data for methylcyclohexane (1) + 1-heptanol (2) mixtures: (a) density at T = 298.15 K; (b) density at T = 303.15 K; (c) excess molar volume at T = 298.15 K; (d) excess molar volume at T = 303.15 K; ●, this work; △, Oswal et al;8 □, Iloukhani et al.9 646



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2 includes comparisons of density and excess molar volume, respectively, of dodecane +1-heptanol system at 298.15 K with

Figure 2. Comparisons of physical properties obtained in this work with literature data for n-dodecane (1) + 1-heptanol (2) mixtures at T = 298.15 K: (a) density; (b) excess molar volume; ●, this work; □, Mahajan et al;11 ★, El-Hefnawy et al.12

data available in literature.11,12 The experimental values in this work are in good agreement with literature data. The VEm values of these binary systems at temperatures from T = (293.15 to 333.15) K fitted with eq 4 are shown in Figure 3. For the systems of n-dodecane with alcohol, the values of VEm are all positive and maximum value is observed when the mole fraction of n-dodecane is 0.6. A positive excess molar value means the actual volume will expand from a macroscopic point of view when compounds are mixed.13 Excess molar values are affected by many factors, such as intermolecular forces, space resistance, and physical interactions. Among intermolecular forces, including dispersion force, induction force, and orientation force, the dispersion force plays the dominant role between most molecules. Dispersion forces become stronger as the molecular weight becomes larger. Stronger dispersion forces lead to more positive excess molar values. Hydrogen bonds tend to be formed when alcohols exist. Two alcohols, 1-heptanol and cyclohexylmethanol, were employed in the present systems, respectively. The models of 1-heptanol and cyclohexylmethanol molecules and hydrogen bond between two molecules are shown in Figure 4. When nonpolar n-dodecane was added to 1-heptanol or cyclohexylmethanol, the destruction of hydrogen bonds led to an increase of excess molar volume. For the system of methylcyclohexane with 1-heptanol, the values of VEm are positive and maximum value is observed when the mole fraction of methylcyclohexane is 0.8. For the system of

Figure 3. Excess molar volumes, VEm, as a function of mole fraction of n-dodecane or methylcyclohexane for the binary systems of (a) ndodecane +1-heptanol; (b) n-dodecane + cyclohexylmethanol; (c) methylcyclohexane +1-heptanol; (d) methylcyclohexane + cyclohexylmethanol at 0.1 MPa and nine different temperatures: ■, 293.15 K; ●, 298.15 K; ▲, 303.15 K; ▼, 308.15 K; ⧫, 313.15 K; ◀, 318.15 K; ▶, 323.15 K; ⬢, 328.15 K; ★, 333.15 K; , the Redlich− Kister correlations. 647



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The minimum and maximum are observed when the mole fraction of methylcyclohexane is 0.3 and 0.9, respectively. When the concentration of methylcyclohexane is high, the dispersion force gradually holds the dominant effect with the addition of cyclohexylmethanol, which leads to the positive values of VEm. When the concentration of cyclohexylmethanol rises, the hydrogen bonding leads to the molecules clinging tightly together, thus causes the negative values of VEm. The absolute excess molar values of the systems with methylcyclohexane are slightly smaller than those systems with n-dodecane. This might be explained by the larger steric hinder of the systems with methylcyclohexane. 3.2. Viscometric Properties. Experimental viscosities (η) of binary systems at the temperature T = (293.15 to 333.15) K

Figure 4. Model of (a) 1-heptanol and (b) cyclohexylmethanol molecules and hydrogen bond between two molecules: gray ball, carbon atom; white ball, hydrogen atom; red ball, oxygen atom; dash line, hydrogen bond.

methylcyclohexane with cyclohexylmethanol, the values of VEm decreased to the minimum and then increase to the maximum.

Table 4. Viscosities at Different Mole Fractions (x1) for the Binary Mixtures of n-Dodecane (1) + 1-Heptanol (2), n-Dodecane (1) + Cyclohexylmethanol (2), Methylcyclohexane (1) + 1-Heptanol (2), Methylcyclohexane (1) + Cyclohexylmethanol (2) at Temperatures from T = (293.15 to 333.15) K and Atmospheric Pressure P = 0.1 MPaa η/mPa·s x1

a

293.15 K

298.15 K

0.0998 0.2005 0.3020 0.3991 0.4989 0.5994 0.6975 0.7959 0.8984

5.346 4.224 3.358 2.778 2.363 2.052 1.835 1.677 1.538

4.555 3.626 2.917 2.444 2.098 1.837 1.653 1.516 1.397

0.1014 0.1991 0.2990 0.3997 0.4992 0.6005 0.7008 0.7986 0.8996

18.355 9.786 6.177 4.307 3.223 2.542 2.087 1.809 1.594

14.587 7.990 5.179 3.688 2.813 2.251 1.873 1.633 1.447

0.1004 0.1991 0.3134 0.3990 0.4994 0.5997 0.6987 0.7995 0.8995

5.541 4.404 3.336 2.649 2.055 1.603 1.275 1.030 0.845

4.649 3.773 2.924 2.325 1.830 1.448 1.165 0.951 0.790

0.0998 0.1996 0.2999 0.3998 0.5004 0.6007 0.6997 0.7984 0.9012

22.559 12.817 7.902 4.953 3.225 2.164 1.555 1.159 0.891

17.674 10.282 6.500 4.176 2.832 1.920 1.407 1.065 0.817

303.15 K

308.15 K

313.15 K

318.15 K

n-Dodecane (1) + 1-Heptanol (2) 3.910 3.381 2.940 2.573 3.144 2.745 2.412 2.134 2.559 2.260 2.009 1.795 2.168 1.935 1.736 1.566 1.878 1.690 1.528 1.388 1.655 1.500 1.365 1.247 1.498 1.364 1.247 1.145 1.380 1.262 1.158 1.066 1.276 1.172 1.080 0.999 n-Dodecane (1) + Cyclohexylmethanol (2) 11.730 9.573 7.900 6.588 6.621 5.545 4.691 4.005 4.403 3.779 3.271 2.854 3.197 2.795 2.461 2.183 2.479 2.201 1.966 1.767 2.010 1.806 1.631 1.480 1.690 1.532 1.395 1.276 1.481 1.351 1.237 1.138 1.321 1.211 1.115 1.031 Methylcyclohexane (1) + 1-Heptanol (2) 4.037 3.484 3.027 2.643 3.261 2.838 2.485 2.188 2.548 2.235 1.932 1.749 2.055 1.827 1.633 1.468 1.640 1.476 1.335 1.213 1.314 1.197 1.094 1.004 1.068 0.983 0.907 0.840 0.879 0.816 0.759 0.708 0.736 0.702 0.645 0.607 Methylcyclohexane (1) + Cyclohexylmethanol (2) 14.092 11.369 9.257 7.638 8.368 6.888 5.729 4.813 5.421 4.567 3.884 3.332 3.567 3.075 2.672 2.340 2.446 2.155 1.912 1.706 1.715 1.542 1.393 1.264 1.279 1.167 1.069 0.983 0.980 0.905 0.839 0.779 0.769 0.718 0.672 0.631

323.15 K

328.15 K

333.15 K

2.266 1.896 1.612 1.417 1.265 1.143 1.054 0.986 0.928

2.006 1.694 1.454 1.288 1.158 1.051 0.974 0.915 0.864

1.785 1.522 1.317 1.175 1.063 0.970 0.902 0.851 0.807

5.525 3.447 2.507 1.947 1.594 1.348 1.171 1.050 0.957

4.696 2.990 2.216 1.746 1.446 1.233 1.079 0.973 0.891

3.987 2.614 1.972 1.574 1.318 1.132 0.997 0.904 0.832

2.322 1.937 1.559 1.324 1.106 0.924 0.779 0.662 0.572

2.050 1.723 1.396 1.200 1.011 0.853 0.725 0.621 0.540

1.820 1.541 1.254 1.092 0.928 0.789 0.676 0.584 0.512

6.350 4.082 2.882 2.064 1.539 1.152 0.907 0.726 0.594

5.322 3.491 2.512 1.831 1.379 1.054 0.839 0.679 0.561

4.526 3.011 2.204 1.634 1.250 0.967 0.778 0.637 0.531

Standard uncertainties u are u(x) = 0.0001, u(p) = 1000 Pa, u(T) = 0.01 K, ur(η) = 0.01. 648



Article

and pressure P = 0.1 MPa are summarized in Table 4. It is observed that the viscosity of the four binary systems increased with the increase of the mole fraction of 1-heptanol or cyclohexylmethanol. The values of viscosities decreased as the temperature increased. On the basis of these experimental data, the viscosity deviations (Δη) are calculated by the following equation: Δη = ηm − (x1 × η1 + x 2 × η2)

(6)

where ηm represents the viscosity of the mixture, η1, η2 stand for the viscosity of pure component 1 and 2, respectively. x1 is the mole fraction of n-dodecane or methylcyclohexane, and x2 is the mole fraction of 1-heptanol or cyclohexylmethanol. Comparisons of viscosity and viscosity deviation in this work with literature data11 for n-dodecane +1-heptanol at 298.15 K are shown in Figure 5. There are some differences between the

Figure 5. Comparisons of physical properties obtained in this work with literature data for n-dodecane (1) + 1-heptanol (2) mixtures at T = 298.15 K: (a) viscosity; (b) viscosity deviation; ●, this work; □, Mahajan et al.11

experimental values in this work and literature data measured by Mahajan et al.11 It is worth noting that viscosity values reported by Mahajan et al. were measured with a calibrated Ubbelohde suspended level viscometer, in contrast with our data which were determined by automatic microviscometer calculated from experimental density data. The values and uncertainty of Δη are listed in Table S2. Δη of the four binary systems at different temperatures are shown in Figure 6. It is indicated that all of the values of Δη are negative. The absolute values of Δη decrease with the increasing temperature. The maximum negative Δη value of the systems with 1-heptanol can be observed when the mole fraction of x1 is 0.4. For the systems with cyclohexylmethanol,

Figure 6. Viscosity deviations, Δη, as a function of mole fraction of ndodecane or methylcyclohexane for the binary systems of (a) ndodecane + 1-heptanol; (b) n-dodecane + cyclohexylmethanol; (c) methylcyclohexane +1-heptanol; (d) methylcyclohexane + cyclohexylmethanol at 0.1 MPa and nine different temperatures: ■, 293.15 K; ●, 298.15 K; ▲, 303.15 K; ▼, 308.15 K; ⧫, 313.15 K; ◀, 318.15 K; ▶, 323.15 K; ⬢, 328.15 K; ★, 333.15 K; , the Redlich− Kister correlations. 649



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3.3. Freezing Point. The freezing points (Tf) for four binary systems are measured in the whole concentration range. The experiment data of Tf are listed in Table 6. The freezing point of pure cyclohexylmethanol is beyond the measure range of DSC used in this work. Because of the freezing point depression, the freezing points of the binary system of methylcyclohexane and cyclohexylmethanol can not be observed. In the systems with n-dodecane, it can be observed that the addition of alcohol causes an obvious decrease of the freezing points of the mixtures. Typically, aerocrafts flying at high altitudes always suffer low environmental temperature, which can lead to the partial solidification of hydrocarbon fuels. Consequently, the frozen fuels can block filters and damage aerocrafts. Researches on freezing points of hydrocarbon fuels with additives can provide helpful data toward the safe operation of aircraft at low temperatures.

the maximum negative value appeared when the mole fraction of x1 is 0.3. Moreover, the absolute values of Δη of the systems with cyclohexylmethanol are much larger than those systems with 1-heptanol. These observed phenomena can be explained by the following aspects. First, hydrogen bonding is one of the most important factors to affect the viscosity deviations. With the enhancement of temperature, the hydrogen bonding becomes weaker, causing the absolute values of Δη to be smaller. To investigate the molecular interactions, Ab initio force field calculations were employed via Materials Studio Forcite module.14,15 Detailedly, the two alcohols are built and their geometries are full optimized with the condensed-phase optimized molecular potentials for atomistic simulation studies (COMPASS) force field. Afterward, two molecules of the same alcohol are assembled within a certain distance to form a single hydrogen bond. The two molecular system is also geometrically optimized via the COMPASS force field, both for 1-heptanol and cyclohexylmethanol. The stabilization energies for these systems are calculated with the following equation, Es = E h − 2E0

4. CONCLUSION

(7)

In this work, the experimental data of density, viscosity, freezing point for the four binary systems of n-dodecane, methylcyclohexane with 1-heptanol or cyclohexylmethanol were measured over the whole composition range at different temperatures T = (293.15 to 333.15 K) and pressure P = 0.1 MPa. The excess molar volumes and deviations in viscosity are calculated and corrected with the Redlich−Kister-type polynomial equation. Apparently, different relationships of the excess molar volume against composition are observed for the four binary systems, which are mainly caused by different contributions of the intermolecular forces, space resistance, and physical interactions. The values of viscosity deviations for these four binary mixtures are all negative. The absolute values of Δη of the systems with cyclohexylmethanol are much larger than those systems with 1-heptanol due to the larger molecular interactions proved by ab initio force field calculations. The addition of alcohols with a lower freezing point makes an obvious drop in the freezing point of the binary mixtures. These results provide constructive data toward preparation of potential hydrocarbon fuels employed in different temperatures.

where Es is the stabilization energy, Eh is the total energy of two molecules with single hydrogen bond, and E0 is the initial total energy of a single molecule. Relevant energies are listed in Table 5. As shown in the table, Es for cyclohexylmethanol is Table 5. Calculated Relevant Energies for 1-Heptanol and Cyclohexylmethanol item

Eh/kcal·mol−1

E0/kcal·mol−1

Es/kcal·mol−1

1-heptanol cyclohexylmethanol

−41.64 −35.42

−17.46 −13.89

−6.73 −7.63

larger than the one for 1-heptanol, which means the interaction between cyclohexylmethanol molecules is stronger. Due to the stronger molecular interactions, the systems with cyclohexylmethanol have much larger viscosity deviations. The data of Δη versus composition are fitted to the Redlich−Kister type polynomial equation using eq 4, and the standard deviation (σ) is calculated with eq 5. The correlation parameters and standard deviations are listed in Table S3.

Table 6. Freezing Points (Tf) at Different Mole Fractions (x1) for the Binary Mixtures of n-Dodecane (1) + 1-Heptanol (2), nDodecane (1) + Cyclohexylmethanol (2), Methylcyclohexane (1) + 1-Heptanol (2), Methylcyclohexane (1) + Cyclohexylmethanol (2)a n-dodecane (1) + 1-heptanol (2)

a

n-dodecane (1) + cyclohexylmethanol (2)

methylcyclohexane (1) + 1-heptanol (2)

methylcyclohexane (1) + cyclohexylmethanol (2)

x1

Tf/°C

x1

Tf/°C

x1

Tf/°C

x1

Tf/°C

0.0000 0.0998 0.2005 0.3020 0.3991 0.4989 0.5994 0.6975 0.7959 0.8984 1.0000

−34.1 −33.2 −15.9 −12.9 −11.7 −10.8 −10.4 −9.9 −9.2 −9.2 −8.2

0.0000 0.1014 0.1991 0.2990 0.3997 0.4992 0.6005 0.7008 0.7986 0.8996 1.0000

b −17.1 −13.3 −11.5 −11.0 −10.6 −10.2 −10.0 −9.6 −9.0 −8.2

0.0000 0.1004 0.1991 0.3134 0.3990 0.4994 0.5997 0.6987 0.7995 0.8995 1.0000

−34.1 −35.2 −37.0 −39.4 −38.6 −45.7 −46.1 −48.8 −48.3 −53.0 −125.3

0.0000 0.0998 0.1996 0.2999 0.3998 0.5004 0.6007 0.6997 0.7984 0.9012 1.0000

b b b b b b b b b b −125.3

Standard uncertainties u are u(x) = 0.0001, u(p) = 1000 Pa, u(Tf) = 3 K, bNot observed in this work 650



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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.6b00688. The values of excess molar volumes (VEm), viscosity deviations (Δη), and correlation coefficients (Ai) of the Redlich−Kister equation for VEm and Δη (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel.: 86−571−88981416. Fax: +86−571−88981416. ORCID

Yongsheng Guo: 0000-0001-7609-1891 Funding

The authors are grateful for financial support from the National Natural Science Foundation of China (Grant No. 21173191). Notes

The authors declare no competing financial interest.

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Density, Viscosity, and Freezing Point for Four Binary Systems of n

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