Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Measurement of Critical Properties for Binary and Ternary Mixtures Containing n‑Butanol and n‑Alkane Chengjie Wang, Junshuai Chen, Muhammad Salman, Xiangyang Liu, Ying Zhang, and Maogang He*
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MOE Key Laboratory of Thermo-Fluid Science and Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, P. R. China ABSTRACT: The critical temperatures (Tc) and critical pressures (pc) of five binary mixtures of n-butanol + n-alkane (C = 6, 7, 8, 9, 10) as well as two ternary mixtures (n-butanol + hexane + heptane and n-butanol + heptane + octane) were measured over the whole concentration range using a flow method apparatus. The Tc of binary mixtures which contain heptane, octane, and nonane display a significant nonideality. The pc of binary mixtures increase with the increasing mole fraction of n-butanol and p c −x 1 curves rise up more obviously in richer n-butanol regions. The trends of the Tc−w1 curves of two ternary mixtures slightly change with the increasing mass fraction of corresponding n-alkane components in mixtures. By using the Redlich−Kister equations, average absolute deviations (AADs) of binary mixtures were less than 0.09% and 0.31% for Tc and pc, respectively. Tc and pc of ternary mixtures were correlated using Cibulka’s equations and Singh−Sharma’s equations.
1. INTRODUCTION The critical properties which include critical temperature, critical pressure, and critical volume are one of the most important thermophysical properties of fluids as well as viscosity,1−3 heat capacity,4−6 phase behavior,7−10 and diffusion coefficient.11−13 They are not only necessary for the use of equations of state (EOS) and corresponding states principle,14,15 but also the basis for the description of phase behavior of mixtures as the trajectory of the critical points represents the phase change boundaries in phase diagrams for mixtures.16 Furthermore, the critical properties of fluids are the crucial data for supercritical fluid technology which has been broadly used in many fields such as chemical reaction processes and extraction industries.17−19 Gasoline additives are widely used nowadays since they have achieved better and more complete combustion of gasoline, the main components of which are n-alkanes and other hydrocarbons.20 n-Butanol which has low exhaust emission and high octane number is also considered to be a potential gasoline additive just like ethanol, n-propanol, and methyl tert-butyl ether (MTBE).21−23 Knowledge of the critical properties of these mixtures of hydrocarbon and gasoline additive plays a pivotal role in the gasoline design with required characteristic and the optimization of fuel combustion.24 Currently, there are some reports for mixtures of different gasoline additives and hydrocarbons for which the critical properties have been proclaimed,24−33 but experimental critical parameters of n-butanol and n-alkane mixtures are very lacking. As far as we know the critical properties of five binary mixtures which are n-butanol + hexane, n-butanol + heptane, n-butanol + octane, n-butanol + nonane, and n-butanol + decane have been measured by Hicks et al.,31 Christou et al.,32,33 and Gil et al.27 In this work, Tc and pc of five binary mixtures of n-butanol + n-alkane (C = 6, 7, 8, 9, 10) as well as two ternary mixtures (n-butanol + hexane + heptane and n-butanol + heptane + octane) were reported. Our experimental data for binary mixtures was © XXXX American Chemical Society
determined in different mole fractions, and experimental critical properties for ternary mixtures were presented for the first time. Tc and pc of five binary mixtures were correlated using classical Redlich−Kister equations while those of ternary mixtures were correlated with Cibulka’s equations and Singh−Sharma’s equations.
2. EXPERIMENT 2.1. Materials. All chemicals studied in this work were used to perform experimental measurements without any further purification. Detailed information about the chemicals is presented in Table 1. 2.2. Experimental Apparatus. A flow method apparatus similar to that described in the literature34,35 was used to measure Tc and pc of pure substances and mixtures, which is shown in Figure 1 and has been introduced in our previous papers.24,36 In the measurement, the fluid was pumped into the system and heated evenly by the electric heater within the experimental cell. Once temperature slightly exceeded Tc, pressure was adjusted via a back pressure valve until the critical opalescence phenomenon could be observed through the window in the experimental cell. When the critical opalescence appeared and disappeared alternately, the fluid was considered to have reached the critical points. Then, the position of the phenomenon was adjusted slowly by controlling the temperature. When this phenomenon occurred stably near the bottom of the platinum resistance thermometer, the measured temperature and pressure were assumed to be Tc and pc, respectively. The accuracy of experimental apparatus was proven by measuring Tc and pc of n-butanol and five pure n-alkanes. Table 1 Received: July 7, 2018 Accepted: August 30, 2018
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DOI: 10.1021/acs.jced.8b00585 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
Table 1. Mass Purity, Supplier, and Critical Properties of Chemicals Used this worka
NIST (with error range)
chemical name
mass purity
CASRN
source
Tc/K
pc/MPa
Tc/K
pc/MPa
n-butanol hexane heptane octane nonane decane
≥0.995 ≥0.995 ≥0.995 ≥0.990 ≥0.990 ≥0.990
71-36-3 110-54-3 142-82-5 111-65-9 111-84-2 124-18-5
Tianli, Tianjin Guangfu, Tianjin Guangfu, Tianjin Guangfu, Tianjin Guangfu, Tianjin Guangfu, Tianjin
563.0 507.8 540.1 568.9 594.5 617.7
4.406 3.033 2.736 2.496 2.278 2.106
562.0 ± 2.0 507.6 ± 0.5 540.0 ± 2.0 568.9 ± 0.5 595.0 ± 1.0 617.8 ± 0.7
4.5 ± 0.4 3.02 ± 0.04 2.74 ± 0.03 2.49 ± 0.01 2.30 ± 0.04 2.11 ± 0.08
a
Standard uncertainties uc(Tc) = 0.2 K, and uc(pc) = 5.2 kPa.
Table 2. Experimental Uncertainties of Temperature, Pressure and Mole Fraction temperature
pressure
Figure 1. Experimental apparatus of flow method: FC, fluid container; PP, piston pump; VD, vacuum device; V1−V3, valve; PH, preheater; PT, platinum resistance thermometer; P, pressure transducer; EC, experimental cell; TC, thermocouple; BV, back pressure valve. mole fraction
factor of uncertainty
Uncertainty
PRT, u1 temperature measurement circuit, u2 temperature control system, u3 measurement repeatability, urep combined standard uncertainty, uc expandeduncertaintya, U pressure transducer, u1 pressure measurement circuit, u2 pressure control system, u3 measurement repeatability, urep combined standard uncertainty, uc expanded uncertaintya, U mole number of first component, u1 mole number of second component, u2 mole number of third component, u3 purity, up combined standard uncertainty, uc Expanded uncertaintya, Ux
0.02 K 0.001 K 0.005 K 0.2 K 0.2 K 0.4 K 1.25 kPa 0.2 kPa 0.8 kPa 5 kPa 5.2 kPa 0.01 MPa
