Densities, Viscosities, Refractive Indices, and Surface Tensions of

Article pubs.acs.org/jced

Densities, Viscosities, Refractive Indices, and Surface Tensions of Binary Mixtures of 2,2,4-Trimethylpentane with Several Alkylated Cyclohexanes from (293.15 to 343.15) K Chuanfeng Zhang, Guangqian Li, Lei Yue, Yongsheng Guo,* and Wenjun Fang Department of Chemistry, Zhejiang University, Hangzhou 310058, China S Supporting Information *

ABSTRACT: Densities and viscosities have been measured over the whole composition ranges for the binary mixtures of 2,2,4-trimethylpentane with methylcyclohexane, ethylcyclohexane, or n-butylcyclohexane at temperatures T = (293.15 to 343.15) K and atmospheric pressure. Meanwhile, the refractive indices and surface tensions were measured at T = (293.15 to 323.15) K and T = (293.15 to 308.15) K, respectively. The excess molar volumes, VmE, the viscosity deviations, Δη, and the surface tension deviations, Δγ, for these binary systems are calculated and fitted to the Redlich−Kister equation, and the regression coefficients and the standard deviations of the fittings are given. All of the VmE, Δη and Δγ values are negative over the whole composition range for these systems. The values of ΔnD for these binary mixtures are all small, even negligible. These results may be useful for the development of the hydrocarbon fuels.

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studied in the literature.15−19 Nevertheless, there is still a lack of some detailed information about the systems of 2,2,4trimethylpentane with alkylated cyclohexane. In the present work, densities, viscosities, refractive indices, and surface tensions for the binary mixtures of 2,2,4trimethylpentane with several alkylated cyclohexanes, such as methylcyclohexane, ethylcyclohexane, and n-butylcyclohexane were measured. Furthermore, the excess molar volumes, VmE, the viscosity deviations, Δη, the refractive index deviations, ΔnD, and the surface tension deviations, Δγ, of these systems were calculated. These obtained data were also qualitatively analyzed and discussed in terms of molecular structure and interaction.20

INTRODUCTION Aviation fuels contain large portions of iso-paraffinic compounds.1,2 JP-7 (a jet fuel developed by the U.S. Air Force for use in supersonic aircraft) consists of greater than 25 % of isoparaffinic species.3 Violi and Eddings note that iso-paraffinic is one of the predominant components in jet kerosene, accounting for as much as 29% of the fuel.4 Further researches indicate that the synthetic and alternative fuels can have higher content of iso-paraffins than the current logistic fuels.5 Consequently, it seems prudent that iso-paraffins should be taken into account to develop surrogate fuel and study fuel performance in detail. 2,2,4-Trimethylpentane (iso-octane) has been economically important as a primary reference for measuring the antiknock qualities of gasoline and aviation fuel for years.6 Fuels are seen to be composed primarily of straight-chained and branched paraffins, but cycloparaffins are also significant. For example, up to 20 % of Jet-A fuel, the commercial equivalent of JP-8 (a kerosene-based fuel used widely by the US Military) is composed of cycloalkanes. In addition to the role as a traditional fuel, cycloparaffin can also serve as coolant for hypersonic aircraft.7 As described above, iso-paraffinics and cycloparaffins are predominant components in jet kerosene.5,8−11 The investigations on the fundamental properties for binary systems of iso-paraffin with cycloparaffin seem to be of scientific and practical interest. Physicochemical properties such as viscosity, density, surface tension, refractive index, vapor-pressure and excess Gibbs energy for 2,2,4-trimethylpentane + cyclohexane system have been reported.12−14 Some properties for methylcyclohexane +2,2,4-trimethylpentane system are also © XXXX American Chemical Society

2. EXPERIMENTAL SECTION 2.1. Materials. Methylcyclohexane, ethylcyclohexane, nbutylcyclohexane, and 2,2,4-trimethylpentane are obtained from commercial sources. All have stated mass fraction purity of better than 0.99, which is consistent with our own routine analysis by an Agilent 7890A/5975C GC-MS. All samples are directly used without further purification in this work. The specifications of these chemicals are listed in Table 1. 2.2. Methods. The binary mixtures in the present work are prepared with a weighing method by using a Mettler ML 204 balance with a precision of 0.0001 g, the uncertainties of mole fractions are estimated to be within ± 0.0001. Densities for all Received: April 18, 2014 Accepted: July 26, 2015

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The viscosities for all samples are measured with the Anton Paar AMVn viscometer under the same conditions. The viscometer can keep the efflux deflected time within ± 0.001 s and the temperature fluctuation within ± 0.01 K. The uncertainties of viscosity and viscosity deviation in the present work both are ± 0.004 mPa·s, and the relative standard uncertainty is 0.08. The refractive indices are measured on a WAY-2S refractometer at temperatures T = (293.15 to 323.15) K, which is first calibrated with double distilled water before sample testing. A HAAKE thermostatic circulator is used to maintain the constant temperature of tested systems with a precision of ± 0.01 K. The uncertainties of refractive index and refractive index deviation in the present work both are ± 0.0005. The data of surface tension for all systems are determined on A-100P tensiometer with temperature controlling within ± 0.01

Table 1. Specification of Chemicals in This Work compound

source

CAS number

mass fraction purity

methylcyclohexane ethylcyclohexane n-butylcyclohexane 2,2,4-trimethylpentane

Aladdin TCI TCI Aladdin

108-87-2 1678-91-7 1678-93-9 540-84-1

0.999 0.999 0.997 0.995

pure samples and binary mixtures are measured by an Anton Paar DMA 5000 M densimeter at pressure p = 0.1 MPa, and temperature range from (293.15 to 343.15) K. The automatic control equipment can keep the temperature fluctuation of tested systems within ± 0.01 K. Before samples testing, the densimeter should be self-checked first, then calibrated with dried air and double-distilled water. The uncertainty for density and corresponding VmE in the present work, is within ± 0.00005 g·cm−3 and ± 0.012 cm3·mol−1, respectively.

Table 2. Comparison of Experimental Density (ρ), Viscosity (η), Refractive Index (nD) and Surface Tension (γ) for Pure Compounds with Literature Data at Corresponding Temperatures and p = 0.1 MPaa ρ/g·cm−3

η/mPa·s

T/K

expt.

lit.

% ARD

293.15 298.15 303.15 308.15 313.15 318.15 323.15 333.15

0.69191 0.68782 0.68368 0.67951 0.67532 0.67105 0.66680 0.65820

0.6920b 0.6878d 0.6836f 0.6793f 0.6753a 0.6708g 0.6647e 0.6585a

0.013 0.003 0.012 0.031 0.003 0.037 0.316 0.046

293.15 298.15 303.15 308.15 313.15 318.15 323.15 333.15 343.15

0.76935 0.76505 0.76071 0.75637 0.75200 0.74758 0.74317 0.73429 0.72531

0.7693h 0.7651k 0.7607h 0.75636i 0.7519h 0.74760i 0.7431h 0.7343h 0.7253h

0.006 0.007 0.001 0.001 0.013 0.002 0.009 0.001 0.001

0.735 0.692 0.651 0.615 0.580 0.549

293.15 298.15 303.15 308.15 313.15 318.15

0.78798 0.78397 0.77993 0.77588 0.77182 0.76769

0.788p 0.78382q 0.77998i 0.77593i 0.77186i 0.76778i

0.003 0.019 0.006 0.006 0.005 0.012

0.848 0.793 0.745 0.702 0.663 0.628

293.15 298.15 303.15 308.15 313.15 318.15 323.15 333.15 343.15

0.79937 0.79563 0.79188 0.78812 0.78435 0.78049 0.77670 0.76909 0.76143

0.79944s 0.79546q 0.79196i 0.78820i 0.7845a 0.78065i 0.77716t 0.7698a 0.76188t

0.009 0.021 0.010 0.010 0.019 0.020 0.059 0.092 0.059

1.304 1.199 1.109 1.032 0.961 0.900 0.844 0.749 0.671

expt.

0.493 0.470 0.449

lit.

γ/mN·m−1

nD % ARD

expt.

2,2,4-Trimethylpentane 1.3921 0.480d 2.71 1.3886 0.466f 0.86 1.3876 0.441f 1.80 1.3848 1.3833 1.3785 1.3760 Methylcyclohexane 0.735i 0.00 0.6827l 1.36 1.4232 0.646i 0.77 1.4190 0.609i 0.99 0.576i 0.69 1.4150 0.546i 0.55

Ethylcyclohexane 0.842p 0.71 0.7842q 1.12 0.743i 0.27 1.4295 0.700i 0.29 0.661i 0.30 0.626i 0.32 n-Butylcyclohexane 1.296s 0.62 1.4403 1.1922q 0.57 1.111i 0.18 1.4355 1.032i 0.00 0.962i 0.10 0.899i 0.11 0.835t 1.08 0.741t 1.08 0.663t 1.21

lit.

% ARD

expt.

lit.

% ARD

1.3915b 1.3880d 1.3877f 1.3846f 1.3818g 1.3790g 1.3765e

0.043 0.043 0.007 0.014 0.109 0.036 0.036

18.9 18.4 18.0 17.6

19.06c 18.60e 18.20e 17.70e

0.63 1.13 1.15 0.68

23.9 23.0 22.6 22.1

23.74j 23.29n

0.56 1.16

m

1.42053 1.4192o

0.19 0.01

1.41272m

0.16

1.42865r

0.06

1.4408a

0.03

1.4364a

0.063

25.5 24.8 24.6 23.7

26.8 25.9 25.5 24.7

Standard uncertainties u (T) = 0.01 K, u (ρ) = 0.00005 g·cm−3, u (η) = 0.004 mPa·s, ur (η) = 0.08. u (nD) = 0.0005. u(γ) = 0.1 mN·m −1. Reference 22. cReference 23. dReference 15. eReference 12. fReference 24. gReference 25. hReference 26. iReference 20. jReference 27. kReference 28. lReference 29. mReference 30. nReference 31. oReference 32. pReference 33. qReference 34. rReference 35. sReference 36. tReference 39. a b

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Table 3. Densities (ρ) at Different Mole Fractions (x1) for the Binary Mixtures of Alkylated Cyclohexane (1) + 2,2,4Trimethylpentane (2) at T = (293.15 to 343.15) K and Pressure p = 0.1 MPaa ρ/g·cm−3 x1

a

293.15 K

298.15 K

0.0000 0.1012 0.2003 0.3001 0.4019 0.5008 0.6000 0.6998 0.8000 0.9000 1.0000

0.69191 0.69832 0.70487 0.71173 0.71901 0.72640 0.73415 0.74232 0.75091 0.75988 0.76935

0.68782 0.69422 0.70073 0.70758 0.71485 0.72223 0.72996 0.73811 0.74667 0.75561 0.76505

0.0000 0.1000 0.2000 0.3003 0.3997 0.5002 0.6005 0.7002 0.8003 0.8997 1.0000

0.69191 0.70076 0.70980 0.71907 0.72838 0.73796 0.74768 0.75750 0.76749 0.77758 0.78798

0.68782 0.69671 0.70571 0.71502 0.72434 0.73390 0.74364 0.75347 0.76346 0.77357 0.78397

0.0000 0.0999 0.2002 0.3001 0.3996 0.5005 0.6003 0.6994 0.8000 0.9001 1.0000

0.69191 0.70407 0.71588 0.72735 0.73844 0.74938 0.75990 0.77007 0.78014 0.78989 0.79937

0.68782 0.70002 0.71189 0.72339 0.73452 0.74549 0.75605 0.76627 0.77635 0.78612 0.79563

303.15 K

308.15 K

313.15 K

318.15 K

Methylcyclohexane (1) + 2,2,4-Trimethylpentane (2) 0.68368 0.67951 0.67532 0.67105 0.69006 0.68589 0.68169 0.67734 0.69657 0.69238 0.68817 0.68385 0.70340 0.69920 0.69497 0.69064 0.71066 0.70644 0.70220 0.69775 0.71801 0.71378 0.70952 0.70513 0.72572 0.72147 0.71719 0.71285 0.73385 0.72957 0.72527 0.72093 0.74238 0.73808 0.73375 0.72936 0.75130 0.74698 0.74263 0.73824 0.76071 0.75637 0.75200 0.74758 Ethylcyclohexane (1) + 2,2,4-Trimethylpentane (2) 0.68368 0.67951 0.67532 0.67105 0.69257 0.68843 0.68426 0.68005 0.70162 0.69749 0.69335 0.68916 0.71092 0.70680 0.70264 0.69838 0.72025 0.71614 0.71201 0.70780 0.72984 0.72574 0.72161 0.71738 0.73957 0.73547 0.73136 0.72709 0.74940 0.74532 0.74123 0.73702 0.75941 0.75535 0.75126 0.74705 0.76952 0.76546 0.76139 0.75721 0.77993 0.77588 0.77182 0.76769 n-Butylcyclohexane (1) + 2,2,4-Trimethylpentane (2) 0.68368 0.67951 0.67532 0.67105 0.69593 0.69183 0.68770 0.68364 0.70785 0.70380 0.69973 0.69556 0.71940 0.71540 0.71137 0.70724 0.73057 0.72661 0.72264 0.71860 0.74158 0.73766 0.73372 0.72973 0.75217 0.74829 0.74439 0.74043 0.76243 0.75858 0.75472 0.75082 0.77254 0.76872 0.76489 0.76098 0.78234 0.77855 0.77476 0.77084 0.79188 0.78812 0.78435 0.78049

323.15 K

333.15 K

343.15 K

0.66680 0.67308 0.67958 0.68635 0.69344 0.70081 0.70852 0.71659 0.72508 0.73386 0.74317

0.65820 0.66446 0.67092 0.67766 0.68472 0.69207 0.69974 0.70779 0.71625 0.72503 0.73429

0.64944 0.65569 0.66212 0.66884 0.67587 0.68323 0.69090 0.69890 0.70733 0.71608 0.72531

0.66680 0.67582 0.68495 0.69419 0.70363 0.71322 0.72295 0.73288 0.74293 0.75310 0.76359

0.65820 0.66727 0.67643 0.68573 0.69520 0.70482 0.71458 0.72455 0.73462 0.74481 0.75535

0.64944 0.65857 0.66778 0.67713 0.68664 0.69631 0.70612 0.71612 0.72623 0.73646 0.74703

0.66680 0.67945 0.69142 0.70316 0.71456 0.72573 0.73649 0.74695 0.75716 0.76706 0.77670

0.65820 0.67099 0.68312 0.69498 0.70646 0.71770 0.72853 0.73906 0.74937 0.75938 0.76909

0.64944 0.66240 0.67466 0.68664 0.69825 0.70963 0.72057 0.73121 0.74157 0.75162 0.76143

Standard uncertainties u are u(x) = 0.0001, u(T) = 0.01 K, u(ρ) = 0.00005 g·cm−3.

K. The operating method has been described in detail before.21 The uncertainties of surface tension and surface tension deviation in the present work both are ± 0.1 mN·m−1.

Table 3 and Table 4, respectively. Obviously, the density values decrease with increasing tested temperature (T) and the mole fraction of 2,2,4-trimethylpentane (x2) in every binary system. The experimental values of densities are used to calculate the corresponding VmE, as the following equation:

3. RESULTS AND DISCUSSION The measured properties data of all pure samples at designated temperatures and p = 0.1 MPa are listed in Table 2, and compared with the corresponding literature data.12,15,22−36 The percent absolute relative deviations (% ARD) are calculated by the following equation and are also given in Table 2: %ARD = 100

|Plit − P| Plit

Vm E =

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

(2)

where ρm, ρ1, and ρ2 are the densities of binary mixture, alkylated cyclohexane, and 2,2,4-trimethylpentane, respectively; M1, M2 and x1, x2 are the corresponding molar masses and molar fractions for the two components, respectively. The viscosity deviations, Δη, were calculated using

(1)

where P stands for the experimental value of density, viscosity, refractive index, or surface tension in the present work, and Plit is the corresponding value from the literature. The measured density and viscosity values for binary mixtures of alkylated cyclohexane +2,2,4-trimethylpentane at different temperatures and atmospheric pressure are listed in

Δη = ηm − (x1η1 + x 2η2)

(3)

where ηm is the viscosity of the binary mixture and ηi represents that for the ith component. The calculated values of VmE and Δη for all the binary systems at nine different temperatures are C

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Table 4. Viscosities (η) at Different Mole Fractions (x1) for the Binary Mixtures of Alkylated Cyclohexane (1) + 2,2,4Trimethylpentane (2) at T = (293.15 to 343.15) K and Pressure p = 0.1 MPaa η/mPa·s x1

a

293.15 K

298.15 K

0.0000 0.1012 0.2003 0.3001 0.4019 0.5008 0.6000 0.6998 0.8000 0.9000 1.0000

0.518 0.532 0.546 0.562 0.580 0.599 0.620 0.644 0.671 0.701 0.735

0.493 0.506 0.519 0.533 0.549 0.566 0.585 0.606 0.631 0.660 0.692

0.0000 0.1000 0.2000 0.3003 0.3997 0.5002 0.6005 0.7002 0.8003 0.8997 1.0000

0.518 0.540 0.565 0.591 0.619 0.650 0.684 0.719 0.758 0.801 0.848

0.493 0.513 0.536 0.560 0.586 0.613 0.644 0.677 0.712 0.751 0.793

0.0000 0.0999 0.2002 0.3001 0.3996 0.5005 0.6003 0.6994 0.8000 0.9001 1.0000

0.518 0.567 0.623 0.679 0.744 0.816 0.896 0.981 1.078 1.184 1.304

0.493 0.537 0.588 0.640 0.698 0.763 0.835 0.912 0.998 1.093 1.199

303.15 K

308.15 K

313.15 K

318.15 K

Methylcyclohexane (1) + 2,2,4-Trimethylpentane (2) 0.470 0.449 0.430 0.414 0.482 0.460 0.440 0.422 0.494 0.471 0.450 0.432 0.507 0.483 0.461 0.443 0.521 0.496 0.473 0.453 0.537 0.510 0.486 0.465 0.554 0.525 0.500 0.478 0.573 0.543 0.516 0.493 0.595 0.564 0.535 0.509 0.621 0.587 0.556 0.528 0.651 0.615 0.580 0.549 Ethylcyclohexane (1) + 2,2,4-Trimethylpentane (2) 0.470 0.449 0.430 0.414 0.489 0.466 0.446 0.429 0.509 0.485 0.464 0.445 0.531 0.505 0.482 0.461 0.555 0.527 0.503 0.481 0.581 0.550 0.524 0.500 0.609 0.577 0.548 0.522 0.638 0.604 0.573 0.548 0.671 0.634 0.601 0.573 0.706 0.666 0.630 0.598 0.745 0.702 0.663 0.628 n-Butylcyclohexane (1) + 2,2,4-Trimethylpentane (2) 0.470 0.449 0.430 0.414 0.510 0.486 0.464 0.446 0.556 0.528 0.502 0.482 0.605 0.573 0.544 0.519 0.657 0.621 0.588 0.561 0.717 0.675 0.638 0.607 0.781 0.734 0.691 0.654 0.851 0.797 0.749 0.708 0.929 0.868 0.814 0.765 1.014 0.945 0.883 0.829 1.109 1.031 0.961 0.900

323.15 K

333.15 K

343.15 K

0.398 0.406 0.415 0.426 0.435 0.446 0.458 0.471 0.486 0.503 0.522

0.371 0.378 0.386 0.395 0.402 0.411 0.421 0.433 0.445 0.460 0.476

0.348 0.355 0.361 0.368 0.375 0.383 0.391 0.401 0.411 0.424 0.439

0.398 0.412 0.427 0.442 0.460 0.478 0.499 0.522 0.546 0.569 0.597

0.371 0.383 0.396 0.409 0.425 0.440 0.457 0.478 0.498 0.518 0.541

0.348 0.358 0.369 0.380 0.395 0.408 0.423 0.441 0.458 0.476 0.496

0.398 0.427 0.460 0.496 0.534 0.575 0.620 0.668 0.721 0.779 0.844

0.371 0.396 0.424 0.454 0.487 0.522 0.560 0.601 0.646 0.695 0.749

0.348 0.369 0.394 0.420 0.448 0.480 0.510 0.545 0.584 0.626 0.671

Standard uncertainties u are u(x) = 0.0001, u(T) = 0.01 K, u(η) = 0.004 mPa·s, ur(η) = 0.08. n

listed in Table S1 and Table S2 of the Supporting Information, respectively. Deviations in refractive index, ΔnD, were calculated using the following equation: ΔnD = n Dm − (x1n D1 + x 2n D2)

Y = x1·(1 − x1) ∑ Ai (2x1 − 1)i i=0

where x1 is the mole fraction of alkylated cyclohexane, n is the number of estimated parameters, and Ai is the polynomial coefficients. The values of Ai can be obtained with the leastsquares correlation and F-test. The standard deviations, σ, for VmE and Δη are defined as

(4)

where nDm is the refractive index of the binary mixture and nDi is the refractive index of ith component. The deviation in the surface tension, Δγ, was calculated from the experimental data according to the following equation: Δγ = γm − (x1γ1 + x 2γ2)

(6)

σ = [∑ (Yexpt − Ycal)2 /(n − k)]1/2

(7)

where n is the number of data points and k is the number of coefficients. The standard deviations, σ, are given in Table S3 of the Supporting Information. The VmE values of these binary systems at different temperatures fitted with eq 6 are plotted as a function of x1 (alkylated cyclohexane) in Figure 1. The experimental data for the system of methylcyclohexane + 2,2,4-trimethylpentane is compared with reported results in Figure S1, and show acceptable agreement.15,16 It can be seen in Figure 1 that binary

(5)

where γm is the surface tension of the binary mixture and γi is the surface tension of ith component. The composition dependence of VmE and Δη for all binary mixtures is represented using the Redlich−Kister type polynomial equation: D

DOI: 10.1021/acs.jced.5b00105 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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VmE values for the whole composition range. The minimum values of VmE for the three binary systems at given temperatures in this work are at the mole fraction x1 from 0.4 to 0.6. With the increase of temperature, the absolute values of VmE for all three observed binary systems show a slight upward trend. The VmE values result from molecular structure, specific forces and physical intermolecular forces of liquids. As for the present work, all the three systems studied are nonpolar molecules, so the VmE values of these mixtures are attributed to a balance between physical intermolecular forces and structural effects, and the main effect may be the second factor. Hence, the negative values of VmE can be visualized as being due to a closer approach of the unlike molecules with significantly different molecular structures and sizes. Excess molar volumes become more negative with rising temperature, implying a closer approach between two different molecules. The alkyl chain of alkylated cyclohexane plays an important role in the absolute values of VmE for the tested systems. The alkylated cyclohexane with longer alkyl chain can be closer to the 2,2,4trimethylpentane molecule. That is why the maximum negative value is obtained for the n-butylcyclohexane +2,2,4-trimethylpentane mixture. The absolute values of VmE are in the order: VmE (a) < VmE (b) < VmE (c), where a, b, or c denotes the binary system of 2,2,4-trimethylpentane with methylcyclohexane, ethylcyclohexane, or n-butylcyclohexane. The Δη values for all tested systems at different temperatures fitted with eq 6 are plotted as a function of x1 in Figure 2. Some data for methylcyclohexane + 2,2,4-trimethylpentane mixture are compared with reported results and shown in Figure S2,15,17 Owing to the existence of the lower interaction between alkylated cyclohexane and 2,2,4-trimethylpentane molecule, a noticeable decrease in viscosities occurs and consequently the viscosity deviations present negative values. The absolute values of Δη decrease with the rising temperature, indicating that the interaction of different molecules is reduced. The sign and magnitude of Δη also can be affected by the structural characteristic of liquid components arising from the geometrical fitting of one molecule into the structure of another molecule.37,38 In our present study, the n-butylcyclohexane molecule can match better with 2,2,4-trimethylpentane geometrically compared with methylcyclohexane and ethylcyclohexane. The measured data of refractive indices, nD, for all studied binary systems at temperature T = (293.15 to 313.15) K are listed in Table S4 of the Supporting Information. The results show that the values of refractive indices decrease upon increasing the temperature. For each temperature, the values increase with an increase in the mole fraction of alkylated cyclohexane in the mixtures. The refractive index deviations, ΔnD, are listed in Table S5. The experimental values for the system of methylcyclohexane +2,2,4-trimethylpentane are also shown in Figure S3 with literature data.15,18 It can be seen that all the ΔnD values are very small, even negligible according to the experimental uncertainty. The measured data of surface tension, γ, as a function of x1 for the three studied binary systems at temperature T = (293.15 to 308.15) K are shown in Table S6 and Figure S4 of the Supporting Information. It is easily found that the values of surface tension for the three binary mixtures increase with the rise in percentage composition of the alkylated cyclohexane. The corresponding surface tension deviations, Δγ, are listed in Table S7, and they also fit with eq 5 and are shown in Figure 3. The correlated polynomial coefficients and the standard

Figure 1. Excess molar volumes, VmE, as a function of mole fraction of alkylated cyclohexane for three binary systems (a, methylcyclohexane +2,2,4-trimethylpentane; b, ethylcyclohexane +2,2,4-trimethylpentane; c, n-butylcyclohexane +2,2,4-trimethylpentane) at temperatures T = (293.15 to 343.15) K and pressure p = 0.1 MPa: ■, 293.15 K; ▲, 298.15 K; ▼, 303.15 K; ⧫, 308.15 K, ●, 313.15 K, ◀, 318.15K; ▶, 323.15; □, 333.15K; ★,343.15 K; , the Redlich−Kister correlations.

mixtures of methylcyclohexane, ethylcyclohexane, or nbutylcyclohexane with 2,2,4-trimethylpentane exhibit negative E

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Figure 3. Surface tension deviations, Δγ, as a function of mole fraction of alkylated cyclohexane for three binary systems (a, methylcyclohexane + 2,2,4-trimethylpentane; b, ethylcyclohexane + 2,2,4-trimethylpentane; c, n-butylcyclohexane + 2,2,4-trimethylpentane) at temperatures T = (293.15 to 308.15) K and pressure p = 0.1 MPa: ■, 293.15 K; ●, 298.15 K; ▼, 303.15 K; ▲, 308.15 K; , the Redlich−Kister correlations.

Figure 2. Viscosity deviations, Δη, as a function of mole fraction of alkylated cyclohexane for three binary systems (a, methylcyclohexane + 2,2,4-trimethylpentane; b, ethylcyclohexane + 2,2,4-trimethylpentane; c, n-butylcyclohexane + 2,2,4-trimethylpentane) at temperatures T = (293.15 to 313.15) K and pressure p = 0.1 MPa: ■, 293.15 K; ▲, 298.15 K; ▼, 303.15 K; ⧫, 308.15 K, ●, 313.15 K; ◀, 318.15K; ▶, 323.15; □, 333.15K; ★, 343.15 K; , the Redlich−Kister correlations.

are at the mole fraction x1 from 0.4 to 0.6. The deviations of surface tension are associated with molecular interatomic forces in the process of mixing.39 These negative surface tension

deviations are listed in Table S8. The surface tension deviations for the three systems are all negative, and the minimum values F

DOI: 10.1021/acs.jced.5b00105 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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(5) Zeppieri, S. P.; Zafiris, G. S.; Marek A.; Wójtowicz, M. A.; Michael A.; Serio, M. A. Iso-dodecane pyrolysis model development. 50th AIAA Annual Conference, Nashville, TN, 2012. (6) El-Masri, H. A.; Dowd, S.; Pegram, R. A.; Harrison, R.; Yavanhxay, S. J.; Simmons, J. E.; Evans, M. Development of an inhalation physiologically based pharmacokinetic (PBPK) model for 2,2,4-trimethylpentane (TMP) in male Long-Evans rats using gas uptake experiments. Inhalation Toxicol. 2009, 21, 1176−1185. (7) Orme, J. P.; Curran, H. J.; Simmie, J. M. Experimental and modeling study of methyl cyclohexane pyrolysis and oxidation. J. Phys. Chem. A 2006, 110, 114−131. (8) Hong, Z. K.; Lam, K. Y.; Davidson, D. F.; Hanson, R. K. A comparative study of the oxidation characteristics of cyclohexane, methylcyclohexane, and n-butylcyclohexane at high temperatures. Combust. Flame 2011, 158, 1456−1468. (9) Ciajolo, A.; Tregrossi, A.; Mallardo, M.; Faravelli, T.; Ranzi, E. Experimental and kinetic modeling study of sooting atmospheric pressure cyclohexane flame. Proc. Combust. Inst. 2009, 32, 585−591. (10) Aguilar, F.; Alaoui, F. E. A.; Segovia, J. J.; Montero, E. A. Excess enthalpies of ternary mixtures of oxygenated additives + hydrocarbon mixtures in fuels and bio-fuels: Dibutyl ether (DBE) and 1-butanol and 1-hexene or cyclohexane or 2,2,4 trimethylpentane at 298.15 and 313.15 K. J. Chem. Thermodyn. 2013, 56, 6−11. (11) Aguilar, F.; Alaoui, F. E. A.; Segovia, J. J.; Villamanán, M. A.; Montero, E. A. Ether + alcohol + hydrocarbon mixtures in fuels and bio-fuels: Excess enthalpies of binary mixtures containing dibutyl ether (DBE) or 1-butanol and 1-hexene or methylcyclohexane or toluene or cyclohexane or 2,2,4-trimethylpentane at 298.15K and 313.15K. Fluid Phase Equilib. 2012, 315, 1−8. (12) Gomez-Dıaz, D.; Mejuto, J. C.; Navaza, J. M. Physicochemical properties of liquid mixtures. 1.† viscosity, density, surface tension and refractive index of cyclohexane + 2,2,4-trimethylpentane binary liquid systems from 25 to 50 °C. J. Chem. Eng. Data 2001, 46, 720−724. (13) Segura, H.; Reich, R.; Galindo, G. Phase equilibria in the systems cyclohexane + 2,2,4-trimethylpentane and ethyl 1,1dimethylethyl ether + cyclohexane + 2,2,4-trimethylpentane at 94.00 kPa. J. Chem. Eng. Data 2000, 45, 600−605. (14) Jain, D.; Yadav, O. Vapor-pressures and excess Gibbs energies for the system cyclohexane + iso-octane (2,2,4- trimethylpentane). Indian. J. Chem. B 1974, 12, 721−723. (15) Baragi, J. G.; Aralaguppi, M. I.; Kariduraganavar, M. Y.; Kulkarni, S. S.; Kittur, A.; Aminabhavi, T. M. Excess properties of the binary mixtures of methylcyclohexane + alkanes (C6 to C12) at T = 298.15 K to T = 308.15 K. J. Chem. Thermodyn. 2006, 38, 75−83. (16) Oswal, S. L.; Maisuria, M. M. Speeds of sound, isentropic compressibilities, and excess molar volumes of cycloalkane, alkanes and aromatic hydrocarbons at 303.15 K. I. Results for cycloalkane + cycloalkanes, and cycloalkane + alkanes. J. Mol. Liq. 2002, 100, 91− 112. (17) Oswal, S. L.; Maisuria, M. M.; Gardas, R. L. Viscosity of binary mixtures of cycloalkane with cycloalkane, alkane and aromatic hydrocarbon at 303.15 K. J. Mol. Liq. 2003, 108, 199−215. (18) Gelus, E.; Marple, S.; Miller, M. E. Vapor-liquid equilibria of hydrocarbon systems above atmospheric pressure. Ind. Eng. Chem. 1949, 41, 1757−1761. (19) Monton, J. B.; Pena, M. P.; Martinez-Soria, V. Densities, refractive indices, and derived excess properties of the binary systems toluene + isooctane and methylcyclohexane + isooctane and the ternary systems tert-butyl alcohol + toluene + isooctane and tert-butyl alcohol + methylcyclohexane + isooctane at 298.15 K. J. Chem. Eng. Data 2000, 45, 518−522. (20) Li, G. Q.; Chi, H.; Guo, Y. S.; Fang, W. J.; Hu, S. L. Excess molar volume along with viscosity and refractive index for binary systems of tricyclo[5.2.1.02.6]decane with five cycloalkanes. J. Chem. Eng. Data 2013, 58, 3078−3086. (21) Zhang, L. L.; Guo, Y. S.; Xiao, J.; Gong, X. J.; Fang, W. J. Density, refractive index, viscosity, and surface tension of binary mixtures of exo-tetrahydrodicyclopentadiene with some n-alkanes from (293.15 to 313.15) K. J. Chem. Eng. Data 2011, 56, 4268−4273.

deviations can be explained according to the Gibbs adsorption isotherm.40 When a mixture is formed, the component with lower surface tension is usually repulsed from the bulk solution to the surface. That is the main reason leading to the negative surface tension deviations.

4. CONCLUSION In the present work, the fundamental physical properties were measured over the whole composition range for the binary mixtures of 2,2,4-trimethylpentane with methylcyclohexane, ethylcyclohexane, or n-butylcyclohexane. The VmE and Δη for these studied systems were obtained and fitted to the Redlich− Kister equation. For these nonpolar systems, the sign and magnitude of VmE and Δη depend on a balance between molecular interaction and the matching degree of molecular geometrical structure. The alkyl chain of alkylated cyclohexane plays an important role in the absolute values of VmE and Δη for these tested systems. The alkylated cyclohexane with longer alkyl chain can be closer to the 2,2,4-trimethylpentane molecule. That is why the maximum negative value is obtained for the n-butylcyclohexane + 2,2,4-trimethylpentane mixture. In addition, the ΔnD and Δγ values are also obtained from the experimental data. The surface tension deviations can be explained according to the Gibbs adsorption isotherm and molecular interatomic forces in the process of mixing.

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ASSOCIATED CONTENT

S Supporting Information *

The values of excess molar volumes (VmE), viscosity deviations (Δη), refractive indices (nD), refractive index deviations (ΔnD), surface tension deviations (Δγ), correlation coefficients (Ai) of the Redlich−Kister equation for VmE, Δη and Δγ; the figure for surface tensions (γ) versus compositions. The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.5b00105.

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AUTHOR INFORMATION

Corresponding Author

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

The authors are grateful for financial support from the National Natural Science Foundation of China (Grant No. 21173191 and No. 21273201). Notes

The authors declare no competing financial interest.

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REFERENCES

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H

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