Article pubs.acs.org/jced
Solubility of p‑Nitroaniline in Supercritical Carbon Dioxide with and without Mixed Cosolvents Jun-su Jin,† Yan-ying Ning,† Kai Hu,† Hao Wu,*,‡ and Ze-ting Zhang† †
College of Chemical Engineering, and ‡Department of Research Services, Beijing University of Chemical Technology, Beijing, 100029, China ABSTRACT: Using the dynamic-flow method, the solubility of p-nitroaniline in supercritical carbon dioxide was measured with and without mixed cosolvents at pressures of (11.0, 13.0, 15.0, 18.0, and 21.0) MPa, and in the temperature range of (308 to 328) K. The effects of cosolvents (ethanol + n-hexane (molar ratio of 1:1), ethanol, and n-hexane) were studied at a concentration of 4.0 mol %. The solubility of p-nitroaniline showed that it could be a slightly enhanced by n-hexane but decreased by ethanol and the mixed cosolvent. The data of pnitroaniline in pure SCCO2 were successfully correlated by Chrastil, Mendez-Santiago and Teja (MST), Bartle, and Kumar and Johnston (K-J) models, while the experimental ones with different cosolvents were calculated by modified Chrastil, modified MST, Sovova ,and modified Sovova models. All the correlation results were relatively satisfactory with the experiments.
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INTRODUCTION As the analogues of gases and liquids, supercritical fluids (SCFs) have some unique properties in surface tension, viscosity, and diffusivity. Supercritical fluid technology (SFT), which is regarded as one of the green separation techniques, has gained extraordinary developments in the past several decades. Carbon dioxide as a food additive is also used as an SCF because of its inertness, particularly because it has the proper critical constants (7.38 MPa and 304.2 K). Thus, supercritical carbon dioxide (SCCO2) is widely used in some fields, such as food extraction, the dye process, the pharmaceutical industry, and polymer foaming.1−4 The high-pressure equilibrium solubility of solid solute in SCCO2 is fundamental and important for SCF process design, and some solubility data in SCCO2 have been reported by some experts.5,6 However, the available experimental information about solutes in SCCO2 is still limited, especially the solubility of certain polar solids in SCCO2 with different kinds of cosolvents. Therefore, in order to meet industrial requirements, more solubility data of different solid solutes in SCCO2 with and without cosolvents should be determined and supplied. p-Nitroaniline, which has two typical functional groups, amino- and nitro-, is usually used as an intermediate for some organic materials syntheses and an important azoic dye for the dye industry, and it is also used as a pesticide and veterinary drug intermediate in the pharmaceutical industry, in particular for the production of right phenylenediamine, antioxidants, and preservatives. It is reported that p-nitroaniline existing in soil and natural water damages our environment and is difficult to be recovered.7 In addition, relevant information of p-nitroaniline in other SCFs, such as water and alcohols, has been reported.8 To our best knowledge, the solubility data of pnitroaniline in SCCO2 with and without cosolvents did not © 2013 American Chemical Society
appear in previous research reports. But, it is a necessary step to determine the solubility of p-nitroaniline in SCCO2 for using SFT recovery p-nitroaniline in soil or natural water. Furthermore, we try to know the effect of amino- and nitrofunctional groups of p-nitroaniline on solubility, which is an important part work of our long research. In this work, the equilibrium solubility data of p-nitroaniline in SCCO2 were measured by a dynamic-flow method at three temperature points, (308, 318, and 328) K. By the resistance to pressure of the high-pressure equilibrium cell, five pressures (11.0, 13.0, 15.0, 18.0, and 21.0) MPa are appropriately chosen. The effects of cosolvents, ethanol + n-hexane (molar ratio 1:1), ethanol, and n-hexane, were investigated at the same molar concentration and experimental conditions. Then, Chrastil,9 Mendez-Santiago and Teja (MST),10 Bartle,11 and Kumar and Johnston (K-J)12 models have better correlated the experimental data of the binary system (p-nitroaniline + SCCO2); Chrastil modified by González et al. (Chrastil-G),13 MST modified by Sauceau et al. (MST-S),14 Sovova,15 and Sovova modified by Tang et al. (Sovova-T)16 models were employed to correlate the experimental results with cosolvents.
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EXPERIMENT Materials. p-Nitroaniline (CAS Registry No. 100-01-6, purity of more than 99.5 %, analytical purity) was produced by Beijing Hengye Zhongyuan Co., Ltd. The physical properties and molecular structure of p-nitroaniline were given in Table 1. High-purity carbon dioxide (CAS Registry No. 124-38-9, mass
Received: August 6, 2012 Accepted: May 16, 2013 Published: May 29, 2013 1464
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Table 1. Basic Information about p-Nitroaniline
certain volume. An ultrasonic cleaner (Kunshan Ultrasonic Instrument Co., LTD, model KQ-250DE) was used to reduce the solute loss in the course of analysis. An UV−vis spectrophotometer (Unico (Shanghai) Instrument Co., LTD, model UV-2100) could assay the concentration of p-nitroaniline from the two U-shape tubes. The maximum UV absorption λmax of p-nitroaniline standard solution was detected as a fixed wavelength of 228 nm, and a standard curve with the regressed coefficient better than 0.9997 was obtained. Solubility Expression. The solubility (X) of p-nitroaniline in SCCO2 with and without cosolvents was that the mass of the solute was divided by the corresponding recorded volume of CO2, so the mole fraction (Yb) of p-nitroaniline in SCCO2 was calculated according to eq 1:
fraction of more than 99.9 %) was purchased from Beijing Praxair Industrial Gas Co., Ltd. Analytical grade of anhydrous ethanol and n-hexane, whose purity is more than 99.5 % and 95.0 %, respectively, were obtained from Beijing Chemical Reagent Factory. All selected chemicals were used without further purification. Apparatus and Procedure. The solubility of p-nitroaniline with and without mixed cosolvents in SCCO2 has been determined by a dynamic-flow system according to Figure 1. Our co-workers have summarized in detail the high-pressure apparatus and experimental procedure previously.18−20 First, carbon dioxide (CO2) from the high-pressure cylinder was pressurized to appropriate pressure by a Nova compressor. Then, the compressed CO2 entered into a high-pressure buffer vessel for reducing the impact of high-pressure gas on the preheating and mixing cell. Alternatively, in the cosolvent system, a high-pressure pump was used for cosolvents which could accurately control the flow rate of cosolvent to ± 0.01 mL·min−1, and the cosolvent concentration has been chosen as 4.0 mol % in our work. Then, the mixed fluids from the preheating and mixing cell consecutively flowed into a highpressure equilibrium cell with carrying solid solutes, which owns an effective volume of 150 mL, and the inaccuracy of the measured temperature and pressure of the cell is ± 0.1 K and ± 0.05 MPa, respectively. Next the saturated SCCO2 flowed out by controlling a decompression sampling valve, which temperature was supplied by wrapped heating coils, and then the solid solute was instantaneously separated from CO2 and mainly deposited in the first U-shape tube. The accurate volume of CO2 could be read out by the wet gas flow meter, whose uncertain range is ± 0.01 L under laboratory conditions. To maintain the reliability of equilibrium system in the whole experiment process, some experiments have been done to decide the suitable SCCO2 flow rate and the equilibrium time. As a result, all of experimental samples were obtained after 30 min at the flow rate of SCCO2 about 0.5 L·min−1. Analytical Method. p-Nitroaniline was slightly soluble in water, while it was very soluble in anhydrous ethanol, so the collected p-nitroaniline was dissolved in anhydrous ethanol of a
Yb =
XM1 XM1 + ρc M 2
(1)
where Yb/mol·mol−1 is the mole fraction of p-nitroaniline in SCCO2; X/g·L−1 is the solubility of p-nitroaniline for each volume of CO2; M1/g·mol−1 and M2/g·mol−1 are the molecular weights of CO2 and p-nitroaniline, respectively; ρc/g·L−1 is the density of CO2 at the indoor temperature and pressure. The mass solubility (S) of p-nitroaniline in the supercritical phase was calculated following eq 2: S=
YbM 2ρ M1(1 − Yb)
(2)
−1
where S/g·L is the mass solubility of p-nitroaniline in SCCO2; ρ/g·L−1 is the density of pure SCCO2; M1 and M2 have the same meaning as in eq 1. In this work, to ensure the veracity of reported datum, each data point was the average value of at least three replicated sample measurements, and the repeatabilities of sample data obtained were found about ± 5 %.
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SEMIEMPIRICAL MODELS There are two major approaches to predict the solubility in SCF including the equation of state (EOS) and the semiempirical density model.22 The advantage of the semiempirical density model is that it does not require the additional solute properties, such as critical temperature Tc, critical pressure Pc, critical volume Vc, acentric factor ω, and so on. Therefore, the semiempirical density model is popular in research and industry. In this work, four common semi-
Figure 1. Schematic diagram of the experimental apparatus: 1, CO2 high-pressure cylinder; 2, pressure regulating valve; 3, Nova compressor; 4, delivery valve; 5, high-pressure buffer vessel; 6, pressure micrometering valve; 7, preheating and mixing cell; 8, cosolvent vessel; 9, high-pressure pump; 10, cosolvent regulating valve; 11, heater; 12, temperature controller; 13, high-pressure equilibrium cell; 14, constant-temperature stirred water bath; 15, calibrated pressure gauge; 16, decompression sampling valve; 17, heating coils; 18, two U-shape tubes; 19, gas rotameter; 20, wet gas flow meter. 1465
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where Ycal is the calculated mole fraction of p-nitroaniline; Yexp represents the experimental mole data; i is the number of experimental data points.
empirical density models (Chrastil, MST, Bartle, and K-J), whose expressions were summarized in Table 2, respectively, could correlate the experimental solubility of p-nitroaniline in pure SCCO2 using the temperature T/K and density ρ/g·L−1 of SCCO2.
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RESULTS AND DISCUSSION Solubility of p-Nitroaniline in Pure SCCO2. The solubility values (Yb) of p-nitroaniline in SCCO2 at temperatures of (308, 318, and 328) K and at the pressure range of (11.0 to 21.0) MPa, together with the density (ρ) of SCCO2,21 were listed in Table 4 at each operating condition. From Table
Table 2. Four Semiempirical Models Used in Pure SCCO2 models
expressions
reference
Chrastil MST Bartle K-J
ln S = a0 + (a1/T) + a2 ln ρ T ln(YbP) = b0 + b1T + b2ρ ln(YbP/Pref) = c0 + (c1/T) + c2(ρ − ρref) ln Yb = d0 + (d1/T) + d2ρ
9 10 11 12
Table 4. Mole Fraction Solubility (Yb) of p-Nitroaniline in Supercritical Carbon Dioxide
Following Table 2, in those expressions, the computational formula of S had been given as eq 2; P/MPa and T/K are the operating pressure and temperature, respectively. In the Bartle model, as a reference value, Pref is 0.1 MPa, and 700 g·L−1 of ρref. In addition, ai, bi, ci, and di are the adjustable parameters of each model, which could be obtained by the linear regression within a certain pressure and temperature. Because of cosolvents joining, the supercritical phase equilibrium system has changed to a ternary, or even quaternary, system from a binary system. Thus, Chrastil-G, MST-S, Sovova, and Sovova-T, as shown in Table 3, were chosen to correlate experimental results of p-nitroaniline in SCCO2 with cosolvents. In Table 3, Yb′/mol·mol−1 and S′/ g·L−1 are the mole and mass solubility of solute in SCCO2 with cosolvent, respectively; ei and ki are the parameters of Sovova and Sovova-T models; Yc/mol·mol−1 is the cosolvent’s molar fraction; Sc/g·L−1 is the mass concentration of cosolvent, which could be calculated in terms of eq 3:
Sc =
ρM3Yc M1(1 − Yc)
i 1
308
11.0 13.0 15.0 18.0 21.0 11.0 13.0 15.0 18.0 21.0 11.0 13.0 15.0 18.0 21.0
743.95 785.70 815.06 848.04 873.67 603.15 693.65 741.97 789.24 822.91 414.90 571.33 653.50 723.08 767.88
1.34 ± 0.06 1.70 ± 0.08 1.98 ± 0.09 2.11 ± 0.02 2.25 ± 0.03 1.10 ± 0.05 1.62 ± 0.07 2.35 ± 0.07 2.98 ± 0.06 3.34 ± 0.03 0.623 ± 0.03 1.71 ± 0.05 2.56 ± 0.05 3.50 ± 0.03 4.26 ± 0.04
The standard uncertainty u for temperature u(T) is 0.1 K. bThe standard uncertainty u for pressure u(P) is 0.05 MPa. cρ is the density of pure CO2 at different experimental temperatures and pressures, which is obtained from the NIST fluid property database.21 dThe relative standard uncertainty ur for the mole fraction solubility ur(Yb) is 0.05.
4, the values range of Yb was 0.623 × 10−5 to 4.26 × 10−5. A crossover pressure region around (12.0 to 14.0) MPa, where the three isotemperature lines had obviously intersected each other, is shown in Figure 2 for the binary (p-nitroaniline + SCCO2) system. We also can see that, with the effect of pressure, the equilibrium solubility of p-nitroaniline increases following the elevation of pressure when the temperature keeps constant. The increase of pressure leads to the enhancement of the solvent’s density; as a result, there is a remarkable increase of solvent dissolving ability. Moreover, the interactions between the solute molecules and the solvent molecules would be stronger at higher pressure. For the temperature factor, because the system temperature affects the solvent density, solute vapor pressure, and intermolecular interactions, the effect of temperature is more complicated. When over the crossover pressure region, the solubility of p-nitroaniline is gradually increasing with the increasing temperature, but it displays a contrary trend under the crossover region. As an increase of temperature, the
|Ycal − Yexp| Yexp
105·Ybd
a
(3)
∑
ρc/g·L−1
328
in which M3/g·mol is the cosolvent’s molecular weight. In the MST-S equation, ρz is the mixed density of SCCO2 + cosolvent, in this work, because the concentration of SCF far outweighs that of cosolvent in the SCF phase, the density of mixture phase is approximately the density of pure SCCO2; P0 is the standard pressure (0.101325 MPa). In this work, the concentration of mixed cosolvents was 4.0 mol % at three different temperatures; then, the simplified expression 1 was obtained as shown in Table 3. For different cosolvents, the experiments were done at the same cosolvent concentration and temperature; therefore, eq 1 would be further simplified to eq 2, which was also listed in Table 3. The average absolute relative deviation (AARD) shows the quality of correlated models following eq 4: 100 i
Pb/MPa
318
−1
AARD(%) =
Ta/K
(4)
Table 3. Four Semiempirical Models Used in SCCO2 with Cosolvent model
expression
simplified expression 1
simplified expression 2
reference
Chrastil-G MST-S Sovova Sovova-T
ln S′ = a0 + (a1/T) + a2 ln ρ + a3 ln Sc T ln(Y′bP/P0) = b0 + b1T + b2ρz + b3Yc e e Yb′ − Yb = eYc0Yb1 k k Yb′ − Yb = kYc0Yb1ek2/T
ln S′ = A0 + (a1/T) + a2 ln ρ T ln(Y′bP/P0) = B0 + b1T + b2ρ ln|Y′b − Yb| = E + e1 ln Yb ln|Yb′ − Yb| = K + k1 ln Yb + (k2/T)
ln S′ = A0 + a2 ln ρ T ln(Y′bP/P0) = b0 + b2ρz ln|Y′b − Yb| = E + e1 ln Yb ln|Yb′ − Yb| = K + k1 ln Yb
13 14 15 16
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Table 5. Mole Fraction Solubility (Yb′) of p-Nitroaniline in a Quaternary or Ternary System and Solubility Effect Factor ( f)
Figure 2. Experimental data of p-nitroaniline in SCCO2 as a function of pressure: ■, 308 K; ●, 318 K; ▲, 328 K.
solute’s vapor pressure increases, and the solvent’s density decreases, and the former results in an increase of solute solubility, while the latter leads to a decrease of solute solubility in SCCO2. Below the crossover pressure point, with increasing temperature, the decreasing solvent’s density could be a more important influence on solute solubility than that of the increasing solute’s vapor pressure, and beyond the crossover pressure, the increasing solute’s vapor pressure could be the more important one on solute solubility in SCCO2. Solubility of p-Nitroaniline in SCCO2 with Cosolvents. In this work, we have chosen three kinds of cosolvents: the mixture of ethanol + n-hexane (mole ratio 1:1), ethanol, and nhexane at a concentration of 4.0 mol %. The solubility in SCCO2 with cosolvents is expressed in terms of p-nitroaniline mole fraction (Yb′) and listed in Table 5. The mole fraction of p-nitroaniline in SCCO2 with mixed cosolvents was in the range of 0.251 × 10−5 to 3.13 × 10−5. While, according to Figure 3, for the quaternary system (p-nitroaniline + SCCO2 + ethanol + n-hexane), the crossover pressure region has enhanced the scope as (14.0 to 16.0) MPa compared with the binary system at the constant condition. Our previous research19 has also reported the phenomenon of “crossover” shifts. For revealing the cosolvent effect more clearly, the effect factor f is defined as follows: f=
Y ′b (P , T , Yc = 0.04) Yb(P , T , Yc = 0)
cosolvent
Ta/K
Pb/MPa
ethanol + n-hexane
308
11.0 13.0 15.0 18.0 21.0
ethanol + n-hexane
318
11.0 13.0 15.0 18.0 21.0
ethanol + n-hexane
328
11.0 13.0 15.0 18.0 21.0
ethanol
318
11.0 13.0 15.0 18.0 21.0
n-hexane
318
11.0 13.0 15.0 18.0 21.0
105·Yb′c
1.00 ± 0.05 1.36 ± 0.06 1.46 ± 0.04 1.71 ± 0.03 1.81 ± 0.01 average value 0.676 ± 0.03 1.11 ± 0.05 1.54 ± 0.04 2.03 ± 0.06 2.31 ± 0.02 average value 0.251 ± 0.01 0.624 ± 0.02 1.37 ± 0.03 2.39 ± 0.05 3.13 ± 0.03 average value 0.361 ± 0.01 0.778 ± 0.03 1.21 ± 0.04 1.64 ± 0.02 2.00 ± 0.01 average value 1.27 ± 0.06 1.86 ± 0.08 2.64 ± 0.05 3.19 ± 0.06 3.66 ± 0.03 average value
f 0.75 0.80 0.74 0.81 0.81 0.78 0.61 0.69 0.66 0.68 0.69 0.67 0.40 0.37 0.53 0.68 0.73 0.54 0.33 0.48 0.51 0.55 0.60 0.49 1.15 1.15 1.13 1.07 1.10 1.12
a
The standard uncertainty u for temperature u(T) is 0.1 K. bThe standard uncertainty u for pressure u(P) is 0.05 MPa. cThe relative standard uncertainty ur for the mole fraction solubility ur(Yb) is 0.05.
(5)
According to the values of f shown in Table 5, only n-hexane cosolvent enhances the solubility of solute slightly at 318 K, when the average value of f is about 1.12; while the effect of ethanol is obviously reduced larger than that of the ethanol + nhexane mixture, for which the average values of f are 0.49 and 0.67, respectively. It can be seen that the effect of cosolvent follows as the order ethanol < ethanol +n-hexane < n-hexane. pNitroaniline has the functional groups amino- and nitro- on the benzene ring, which forms the stronger steric hindrance effect. As a result, the hydrogen bonding between p-nitroaniline and ethanol was hardly established. The interaction force between solute and n-hexane is a dispersion force. The solute solubility order with cosolvent in SCCO2 is mainly influenced by the physical properties of solute and cosolvent.23−25 For the solute, it may be the solute functional groups, molecular structure,
Figure 3. Mole fraction solubility (Yb′) of p-nitroaniline in SCCO2 with the mixed cosolvent (ethanol + n-hexane) of 4.0 mol % as a function of pressure.: ■, 308 K; ●, 318 K; ▲, 328 K.
steric hindrance, fusion point, and molecular volume, and for the cosolvent, it may be the cosolvent polarity, hydrogen bond, molecular weight, and dispersion forces, and so forth. In 1467
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Table 6. Correlation Parameters for the Solubility of p-Nitroaniline in SCCO2 for the Binary, Ternary, and Quaternary Systems and AARD (%) of Different Models systems binary system (p-nitroaniline + SCCO2)
quaternary system (p-nitroaniline + SCCO2 + ethanol + n-hexanea)
ternary system (p-nitroaniline + SCCO2 + ethanolb) ternary system (p-nitroaniline + SCCO2 + n-hexanec)
models
correlation parameters
i
AARD (%)
Chrastil MST Bartle K-J Chrastil-G MST-S Sovova Sovova-T Chrastil-G MST-S Sovova Chrastil-G MST-S Sovova
a0 = −14.326; a1 = −5234.0; a2 = 4.2154 b0 = −9742.8; b1 = 16.941; b2 = 2.4600 c0 = 18.672; c1 = −7833.4; c2 = 7.5983 × 10−3 d0 = 2.3060; d1 = −5253.5; d2 = 4.7199 × 10−3 A0 = −22.893; a1 = −4494.5; a2 = 5.0994 B0 = −9480.2; b1 = 16.893; b2 = 2.9316 E = −4.1053; e1 = 0.72702 K = 6.6821; k1 = 0.65750; k2 = −3668.8 A0 = −47.152; a2 = 6.5871 B0 = −4573.9; b2 = 3.4406 E = −5.1688; e1 = 0.58480 A0 = −32.346; a2 = 4.4651 B0 = −3627.6; b2 = 2.5087 E = −8.2946; e1 = 0.43180
15 15 15 15 15 15 15 15 5 5 5 5 5 5
3.90 4.53 5.70 4.73 6.58 5.94 16.6 8.68 2.09 1.65 4.28 3.19 4.32 1.52
a With a concentration of 4.0 mol % at different temperatures. bWith a concentration of 4.0 mol % at 318 K. cWith a concentration of 4.0 mol % at 318 K.
addition, the density of mixture fluid may have some effect on it. To explain the actual reasons affecting on this solubility order with cosolvent, we used some software, such as Gaussview 03, to calculate the energy of intermolecular forces between the solute and the cosolvent, which may pay an important role in the solute solubility change in SCCO2 with cosolvent. Correlation Results. The experimental data in pure SCCO2 have been correlated by four semiempirical models. The correlation parameters were presented in Table 6. In the binary systems, all values of AARD, which are less than 6.0 %, show better results. The AARD of Chrastil model is 3.90 %, which is the best result of the correlated experimental data. In comparison with the four semiempirical models, it shows that the ln ρ produced a reasonable solubility estimation. As the experimental solubilities of p-nitroaniline in pure SCCO2 at all isotherms followed the predominant trend of linearity on a graph which plots T ln(YbP) − b1T versus ρ, as shown in Figure 4, the solubility data of p-nitroaniline in SCCO2 are considered consistently good with the thermodynamics. The solubility of p-nitroaniline in SCCO2 with cosolvents is correlated by the simplified expressions of Chrastil-G, MST-S, Sovova, and Sovova-T models, shown in Table 3. At the same temperature and molar fraction of cosolvent, five points of experimental data’s AARD are less than 5.0 % in the ternary system from Table 6, while at different temperatures, the correlated results of 15 experimental points in quaternary system show that the AARDs of each simplified eq 1 are all worse than that of the ternary system. Comparing the four expressions, one explanation is that the factor T has an important effect in the system with cosolvents. It is a better suggestion that the solubility of solid solute in SCCO2 with cosolvents at different temperatures would be better correlated by the models with temperature T, such as Chrastil-G, MST-S, and Sovova-T. According to the equation MST-S model, as shown in Figure 5, a single straight line, which plots T ln(Yb′P/ P0) − b1T versus ρ, shows well that all of the experimental data follow a conspicuous trend of linearity.
Figure 4. Comparison of experimental solubility of p-nitroaniline in pure SCCO2 and calculated results by the MST model at (308, 318, and 328) K. ■, experimental results; , calculated results by the MST model.
points of temperature (308, 318, and 328) K and the pressure range as (11.0 to 21.0) MPa. The crossover pressure region for the binary system (p-nitroaniline + SCCO2) was (12.0 to 14.0) MPa, which was transferred to (14.0 to 16.0) MPa for the quaternary system (p-nitroaniline + SCCO2 + ethanol + nhexane). The concentration of cosolvent (ethanol + n-hexane, ethanol, and n-hexane) was 4.0 mol %. The nonpolar cosolvent n-hexane showed a slight enhancement on the solubility, while ethanol and mixed ethanol + n-hexane decreased. Four semiempirical models were employed to correlate the experimental data of p-nitroaniline in SCCO2, and the Chrastil model obtained the best calculated result with AARD of 3.90 %. In addition, Chrastil-G, MST-S, Sovova, and Sovova-T models could be used to correlate the solubility of p-nitroaniline in SCCO2 with cosolvent (ethanol + n-hexane) at three different temperatures, and the MST-S model gave a better correlated result than those of other three models.
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CONCLUSIONS The high-pressure equilibrium solubility of p-nitroaniline was first measured in SCCO2 with and without cosolvents at three 1468
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Figure 5. Comparison of experimental solubility of p-nitroaniline in SCCO2 with ethanol + n-hexane and calculated results by MST-S model at (308, 318, and 328) K. ■, experimental results; , calculated results by the MST-S model.
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AUTHOR INFORMATION
Corresponding Author
*Tel.: +86-10-64434788. Fax: +86-10-64436781. E-mail:
[email protected]. Funding
This research was financially supported by the funds awarded by National Natural Science Foundation of China (No. 21176012) and National Natural Science Foundation of Jiangsu Province (No. BK2012595) and by Science and Technology Bureau of Changzhou City (No. CJ20110013). The authors are grateful for the support of this research from the Mass Transfer and Separation Laboratory at the Beijing University of Chemical Technology. Notes
The authors declare no competing financial interest.
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dx.doi.org/10.1021/je300987d | J. Chem. Eng. Data 2013, 58, 1464−1469
