Liquid–Liquid Equilibrium Data for the Pseudoternary Model System of

Aug 1, 2016 - In this context, this work aimed to obtain liquid–liquid equilibrium data for pseudoternary model systems composed of refined sunflowe...
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Liquid−Liquid Equilibrium Data for the Pseudoternary Model System of Refined Sunflower Seed Oil + (n‑Hexanal, or 2‑Nonenal, or 2,4-Decadienal) + Anhydrous Ethanol at 298.15 K Perci O. B. Homrich and Roberta Ceriani* Departamento de Desenvolvimento de Processos e Produtos, Universidade Estadual de Campinas (UNICAMP), 13083-852, Campinas, São Paulo Brazil S Supporting Information *

ABSTRACT: In this work, experimental liquid−liquid equilibrium data for three pseudoternary systems containing {refined sunflower seed oil + aldehyde + anhydrous ethanol} were determined at a temperature T of 298.15 K with u(T) = 0.05 K and atmospheric pressure. Binodal curves and tie line compositions are reported for n-hexanal, 2-nonenal, or 2,4-decadienal as solutes. The nonrandom two-liquid1 and universal quasichemical2 models satisfactorily correlated experimental tie line data. Othmer−Tobias3 and Hand4 methods attested the quality of experimental data. Further, the predictive capabilities of four versions5−9 of the UNIFAC10 method were analyzed.

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steam stripping process. Deodorization is the final step of edible oil refining and is also intended for removing other contaminants, such as pesticides.30 Liquid−liquid extraction has been investigated as an alternative for the deacidification step in the chemical or physical refining of edible oils, currently done as a neutralization with caustic soda or a steam stripping process, respectively.31−34 In this configuration, liquid−liquid extraction avoids oil loss in the soap formed during neutralization and undesirable reactions caused by the high temperatures applied in the steam stripping process.35,36 Anhydrous and aqueous ethanol have been extensively37−40 studied as solvents in the liquid−liquid extraction, and provided both high partition coefficients of solutes (fatty acids) and adequate values of solvent selectivity.41 In this context, this work aimed to obtain liquid−liquid equilibrium data for pseudoternary model systems composed of refined sunflower seed oil (1) + n-hexanal (2), or 2-nonenal (3), or 2,4-decadienal (4) + anhydrous ethanol (5) at T = 298.15 K with u(T) = 0.05 K and under atmospheric pressure. Binodal curves were determined using the cloud point method. Tie line quantifications were done through an indirect method (lever-arm rule)42 for all systems. Othmer−Tobias3 and Hand4 methods were applied for qualifying experimental data. The nonrandom two-liquid (NRTL)1 and universal quasichemical (UNIQUAC)2 models were used for correlating tie line mass fractions. Further, the predictive capacities of four versions of

INTRODUCTION Odoriferous compounds are usually found in unprocessed vegetable oils, because of oxidation reactions that occur during storage.11,12 These unpleasant odors are removed in the deodorization step of oil refining using a steam stripping column under high temperatures (up to 265 °C) and very low pressures (up to 3 mmHg).13−15 As a consequence of these drastic processing conditions, typical undesirable effects are cis−trans isomerization, oxidation reactions, and 3-monochloropropane-1,2-diol (3-MCPD) contaminant formation, besides volatilization of nutraceutical compounds and neutral oil losses.16−20 Currently, efforts are focused on a mild deodorization process configuration,21 exposing the bleached oil to lower temperatures for improving refined edible oil quality. Oxidation reactions may form a number of molecules from different chemical classes, as aldehydes, carboxylic acids, ketones, and hydrocarbons, volatile and nonvolatile compounds, with different carbon chain lengths, depending on the fatty acid composition of vegetable oil.22,23 Among them, aldehydes figure as the main contributors to the odor profile of vegetable oils, due to their low threshold values, that is, the detectable concentration of a compound in a solution by an ordinary consumer.24 It is of note that aldehydes are also found in the odor of others foods, such as cheeses, fruits, and milk.25,26 Sunflower seed oil is rich in polyunsaturated fatty acids and possesses low concentrations of tocopherols (antioxidant compound).23,27 Consequently, it is more susceptible to oxidation than other oils, as soybean, rice bran, and corn oils.28,29 In industrial plants, odoriferous compounds of sunflower seed oil are removed by a deodorization step, which is configured as a © 2016 American Chemical Society

Received: February 19, 2016 Accepted: July 11, 2016 Published: August 1, 2016 3069

DOI: 10.1021/acs.jced.6b00152 J. Chem. Eng. Data 2016, 61, 3069−3076

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the UNIFAC10 method, namely, Magnussen et al.5 (UNIFAC-LL), Hirata et al.6 (UNIFAC-FS), Weidlich and Gmehling7 and Gmehling et al.8 (UNIFAC-DMD), and Larsen et al.9 (UNIFAC-LYB) were analyzed. Hirata et al.6 have readjusted the group interaction parameters of UNIFAC using several experimental liquid−liquid equilibrium data comprising pseudoternary or pseudoquaternary systems composed of edible oils plus fatty acids plus pure solvent (methanol or ethanol) or mixed solvents (alcohols and water).

u(T) = 0.05 K. In brief, homogeneous binary mixtures of oil + aldehyde or anhydrous ethanol + aldehyde were prepared in equilibrium glass cells connected to an ultrathermostatic bath (Marconi, model MA-184), by adding known amounts of each compound measured by an analytical balance (Radwag, model AS 220.R2), accurate to ±0.0001 g. This mixture was vigorously stirred with a magnetic stirrer (Fisatom, model 752). Then, the third component was added dropwise to the homogeneous solution followed by gentle mixing until a cloudy solution was formed. Then the turbid mixture was stirred for 10 min to ensure cloud point detection. This procedure was repeated until a representative binodal curve was created for each pseudoternary system. The experimental binodal data were fitted by least-squares regression using the Curve Fitting Toolbox 3.5.1 in MatLab R2015a (The MathWorks Inc.). Equations 1 and 2 represent the extract and raffinate phases, respectively:

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EXPERIMENTAL SECTION Materials. Refined sunflower seed oil (Liza, Cargill, Brazil) was purchased in a local market. Its fatty acid composition was determined by Official AOCS methods Ce 1f-96 and Ce 1-6243 and is presented in Table 1. Table 1. Fatty Acid Profile of Refined Sunflower Seed Oil symbol

fatty acid

CX:Ya

MW/g·(g·mol−1)b

% mass

% molar

M P Po S O Li Le A Ga Be Lg

myristic palmitic palmitoleic stearic oleic linoleic linolenic arachidic gadoleic behenic lignoceric

C14:0 C16:0 C16:1 C18:0 C18:1 C18:2 C18:3 C20:0 C20:1 C22:0 C24:0

228.38 256.43 254.41 284.48 282.47 280.45 278.44 312.54 310.52 340.59 368.63

0.07 5.88 0.08 3.08 32.84 56.71 0.17 0.23 0.15 0.59 0.21

0.09 6.42 0.09 3.03 32.57 56.65 0.17 0.21 0.13 0.48 0.16

EP wsolute = 1 − A exp(Bw5EP4)

(1)

RP wsolute = 1 − C exp(Dw5RPk1 − Cw5RP)

(2)

where wsolute is the mass fraction of solute, w5 is the mass fraction of solvent (anhydrous ethanol), A, B, C, and D are regressed constants, k1 is an exponent, and superscripts EP and RP refer to extract and raffinate phases, respectively. Tie Line Quantification and Quality. Samples of 20 g of pseudoternary mixtures were prepared in equilibrium glass cells (23 mL) and stirred vigorously for 2 h. The turbid mixtures were allowed to rest for at least 12 h at T = 298.15 K with u(T) = 0.05 K. After phase split, both top and bottom phases were carefully weighed, and tie line compositions were determined by the application of the lever-arm rule, originally described by Merchuk et al.42 The solution of the system of four RP EP RP equations (eqs 1−4) with four unknowns (wEP solute, wsolute, w5 , w5 ) gives the mass fractions of solute and solvent in the top and bottom phases, extract (superscript EP), and raffinate (superscript RP) phases, respectively. Parameter α in eqs 3 and 4 is the ratio between the solvent-rich phase (EP) weight (g) and the overall mixture (OM) weight (g).

a

X = number of carbons, Y = number of double bonds. bMolecular weight.

The results shown in Table 1 indicate that refined sunflower seed oil has a high content of polyunsaturated fatty acids (57% m/m, mainly linoleic), followed by monounsaturated fatty acids (33% m/m, mainly oleic acid). Acidity was determined by titration (official method 2201 of the IUPAC)44 in triplicate. As expected for a refined oil, a very low value of free fatty acids (FFA) was obtained, 0.14 with a u(FFA) = 0.02, expressed as percentage of oleic acid. The oil stability index (OSI), defined as the point of maximum change of the rate of oxidation, was conducted using AOCS Method Cd 12b-9243 with a Rancimat instrument (Metrohm, model 743) at 100 °C and 20 L/h of air flow rate. The induction period for refined sunflower seed oil, which is related to the time during which oil has a natural resistance to oxidation, was 5.71 h with u(OSI) = 0.02 h. Table 2 lists the reagents used in this work (CAS Registry numbers, purities in mass fraction, IUPAC names and suppliers). All chemicals were used without any further purification step. Binodal Curve Determination. The binodal curves of the systems composed of refined sunflower seed oil, aldehyde, and anhydrous ethanol were determined experimentally by using the cloud point titration method at T = 298.15 K with

EP = wsolute

w5EP =

OM wsolute ⎛ 1 − α ⎞ RP ⎟w −⎜ ⎝ α ⎠ solute α

(3)

w5OM ⎛ 1 − α ⎞ RP ⎟w −⎜ ⎝ α ⎠ 5 α

(4)

The quality of the liquid−liquid equilibrium data was verified by the semiempirical tests of Hand (eq 5)4 and Othmer−Tobias3 (eq 6): ⎛ w EP ⎞ ⎛ w RP ⎞ ⎟ = kH log⎜ solute ⎟ + CH log⎜ solute RP EP ⎝ w1 ⎠ ⎝ w5 ⎠

(5)

⎛ 1 − w EP ⎞ ⎛ 1 − w RP ⎞ 5 1 ⎟ = k OT log⎜ ⎟ + COT log⎜ RP EP w w ⎠ ⎝ ⎠ ⎝ 1 5

(6)

where kH, CH, and kOT, COT are the fitting parameters.

Table 2. Source and Purity of Chemicals Used in This Work compounds

IUPAC name

CAS Registry No.

supplier

purity (mass fraction)

n-hexanal 2-nonenal 2,4-decadienal anhydrous ethanol

hexanal (2E)-2-nonenal (2E,4E)-deca-2,4-dienal ethanol

66-25-1 18829-56-6 25152-84-5 64-17-5

Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich

0.98 >0.93 >0.89 0.995

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Table 3. Experimental (Liquid + Liquid) Equilibrium Data for (Refined Sunflower Seed Oil, [n-Hexanal (2), or 2-Nonenal (3), or 2,4-Decadienal (4)] and Anhydrous Ethanol (5)) Pseudoternary Systems at T = 298.15 K and p = 0.094 MPaa sunflower seed oil-rich phase replicate 1 w2 0.0000 0.0213 0.0421 0.0598 0.0752 0.1056 0.1240 0.1400 0.1500 w3 0.0000 0.0216 0.0421 0.0616 0.0792 0.0970 0.1113 0.1359 w4 0.0000 0.0228 0.0430 0.0628 0.0827 0.0977 0.1129 0.1376 0.1505 a

anhydrous ethanol-rich phase replicate 2

w5 0.1167 0.1498 0.1834 0.2069 0.2396 0.3076 0.3852 0.4467 0.5084 w5 0.1167 0.1400 0.1582 0.1780 0.2007 0.2265 0.2516 0.3227 w5 0.1167 0.1322 0.1510 0.1740 0.1973 0.2247 0.2490 0.3174 0.3982

w2 0.0000 0.0216 0.0421 0.0594 0.0785 0.1051 0.1238 0.1402 0.1509 w3 0.0000 0.0214 0.0419 0.0614 0.0801 0.0962 0.1123 0.1360 w4 0.0000 0.0224 0.0428 0.0630 0.0818 0.0974 0.1120 0.1361 0.1518

replicate 1 w5 0.1197 0.1496 0.1823 0.2071 0.2441 0.3087 0.3801 0.4466 0.5074 w5 0.1197 0.1418 0.1578 0.1811 0.1963 0.2287 0.2558 0.3212 w5 0.1197 0.1386 0.1484 0.1797 0.2027 0.2286 0.2516 0.3192 0.3953

w2 0.0000 0.0536 0.1335 0.0926 0.0234 0.0689 0.1115 0.1419 0.1518 w3 0.0000 0.0461 0.0695 0.0934 0.1112 0.1276 0.1378 0.1476 w4 0.0000 0.0241 0.0697 0.0909 0.1113 0.1287 0.1410 0.1575 0.1670

replicate 2 w5 0.9548 0.8814 0.7489 0.8195 0.9244 0.8670 0.7931 0.7211 0.6847 w5 0.9548 0.8911 0.8538 0.8079 0.7681 0.7236 0.6898 0.6374 w5 0.9548 0.9238 0.8541 0.8155 0.7713 0.7272 0.6985 0.6281 0.4979

w2 0.0000 0.0555 0.1345 0.0931 0.0235 0.0692 0.1111 0.1434 0.1513 w3 0.0000 0.0466 0.0691 0.0928 0.1110 0.1265 0.1385 0.1466 w4 0.0000 0.0248 0.0694 0.0907 0.1107 0.1280 0.1419 0.1561 0.1654

w5 0.9568 0.8795 0.7466 0.8206 0.9241 0.8600 0.7920 0.7163 0.6843 w5 0.9568 0.8893 0.8545 0.8101 0.7665 0.7253 0.6892 0.6363 w5 0.9568 0.9270 0.8580 0.8187 0.7653 0.7231 0.6998 0.6230 0.4948

Standard uncertainties u are u(T) = 0.05 K, u(w) = 0.0001 and u(p) = 0.5 kPa.

Data Correlation with Molecular Models and Prediction with UNIFAC Method. Liquid−liquid equilibrium data were correlated with the NRTL and UNIQUAC models. Further, liquid−liquid equilibria were predicted with the UNIFAC method using four versions: UNIFAC-LL (Magnussen et al.5), UNIFAC-FS (Hirata et al.6), which was readjusted for lipid technology systems, UNIFAC-DMD (Weidlich and Gmehling7 and Gmehling et al.8), and UNIFAC-LYB (Larsen et al.9). Tables S1−S4 give the values of the interaction parameters considered by these four UNIFAC versions. All calculations were performed using Aspen Plus V8.4. On the basis of the fatty acid composition of refined sunflower seed oil given in Table 1, the probable triacylglycerol (TAG) composition was estimated using the procedure of Antoniosi Filho et al.,45 which determined a representative TAG (LiLiO), 3-[(9Z)-9-octadecenoyloxy]-1,2-propanediyl(9Z,12Z,9′Z,12′Z)bis(−9,12-octadecadienoate) with a molecular weight of 878.5 g·(g·mol−1). So, to represent refined sunflower seed oil, the triacylglycerol LiLiO, a pseudocomponent,6 was considered in data correlation. The structural parameters (r and q) of LiLiO, ethanol, n-hexanal, 2,4-decadienal, and 2-nonenal for UNIQUAC and UNIFAC, and group interaction parameters for UNIFAC were calculated considering the following functional groups: CH3, CH2, CH, CH2COO, CHO, OH, and HCCH. The Britt-Luecke algorithm was used to obtain binary parameters (bij/J·mol−1) for UNIQUAC and NRTL models, and the nonrandomness parameter (αij) for the

NRTL model, with the Deming initialization method. Global deviations (δw) were calculated using eq 7 to evaluate the agreement between experimental and calculated (or predicted) mass fractions for UNIQUAC, NRTL, UNIFAC-LL, UNIFAC-FS, UNIFAC-DMD, and UNIFAC-LYB: N

P

δw = 100[( ∑ ∑ {(wi , n RP,exp − wi , n RP,calc)2 n=1 i=1

+ (wi , n

EP,exp

− wi , n EP,calc)2 })/(2NP)]1/2

(7)

where N is the total number of tie lines in each system, P is the total number of components in each system, and the superscripts exp and calc refer to experimental and calculated (or predicted) values, respectively.

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RESULTS AND DISCUSSION Binodal Curves. Three novel pseudoternary phase diagrams were determined for refined sunflower seed oil (1), aldehydes [n-hexanal (2), or 2-nonenal (3), or 2,4-decadienal (4)] and anhydrous ethanol (5) at T = 298.15 K with u(T) = 0.05 K under atmospheric pressure (Table 3). Equations 1 and 2 fitted well the binodal data for all systems, providing very suitable coefficients of determination, R2, higher than 0.9929, and standard deviations, SD, lower than 0.0043 (Table 4). Fitted parameters for eqs 1 and 2 are given in Table 4. 3071

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Table 4. Values of Parameters of eqs 1 (Extract Phase) and 2 (Raffinate Phase), and Their Standard Deviations (SD) and Coefficients of Determination (R2) for Pseudoternary Systems Containing n-Hexanal (2), 2-Nonenal (3), or 2,4-Decadienal (4) as Solute extract phase (EP)

a

solute

A

95% confidence bounds

2 3 4

0.7981 0.8176 0.8140

(0.7947, 0.8015) (0.8160, 0.8191) (0.8111, 0.8170)

solute

C

95% confidence bounds

2 3 4

1.112 1.143 1.130

(1.110, 1.114) (1.141, 1.146) (1.126, 1.134)

95% confidence bounds

SDa

R2

(0.2671, 0.2829) (0.2386, 0.2463) (0.2402, 0.2547)

0.0029 0.0014 0.0036

0.9970 0.9992 0.9960

D

95% confidence bounds

SDa

R2

0.9392 8.309 2.628

(0.9307, 0.9477) (7.898, 8.720) (2.507, 2.748)

0.0018 0.0024 0.0043

0.9988 0.9974 0.9929

B 0.2750 0.2425 0.2475 raffinate phase (RP)b

Standard deviation is calculated as M

SD =

exp calc 2 − wsolute )i /M ]0.5 ∑ [(wsolute i=1

calc where wexp solute is the experimental mass fraction of solute, wsolute is the calculated mass fraction of solute using eq 1 or 2, and M is the number of b solubility data for each solute in Table 3. Exponent k1 in eq 2: for n-hexanal k1 = 1.7, for 2-nonenal k1 = 4.0, and for 2,4-decadienal k1 = 3.0.

Table 5. Liquid−Liquid Equilibrium Data (mass fractions w) for Model Systems Containing Refined Sunflower Seed Oil (1), [n-Hexanal (2), or 2-Nonenal (3), or 2,4-Decadienal (4)] and Anhydrous Ethanol (5) at T = 298.15 K and p = 0.094 MPaa overall mixture (OM) w1 0.4978 0.4857 0.4512 0.4221 0.4093 0.3225 w1 0.4858 0.4687 0.4524 0.4296 0.4109 0.3802 w1 0.4873 0.4695 0.4561 0.4283 0.4051 0.3818 a

w2 0.0000 0.0147 0.0439 0.0712 0.0900 0.1223 w3 0.0147 0.0312 0.0457 0.0700 0.0902 0.1205 w4 0.0150 0.0298 0.0452 0.0701 0.0904 0.1191

w5 0.5022 0.4996 0.5049 0.5067 0.5007 0.5552 w5 0.4995 0.5001 0.5019 0.5004 0.4989 0.4993 w5 0.4977 0.5007 0.4987 0.5016 0.5045 0.4991

raffinate phase (RP) w1 0.867 0.861 0.796 0.752 0.730 0.692 w1 0.855 0.822 0.797 0.757 0.717 0.651 w1 0.860 0.830 0.804 0.749 0.698 0.626

u(w1) 0.005 0.005 0.005 0.005 0.006 0.012 u(w1) 0.003 0.002 0.002 0.003 0.003 0.004 u(w1) 0.005 0.005 0.005 0.005 0.005 0.006

w2 0.000 0.009 0.035 0.052 0.059 0.072 w3 0.014 0.031 0.043 0.062 0.081 0.108 w4 0.015 0.029 0.042 0.067 0.089 0.117

u(w2) 0.003 0.003 0.003 0.003 0.003 0.005 u(w3) 0.002 0.002 0.002 0.002 0.002 0.002 u(w4) 0.003 0.003 0.003 0.003 0.003 0.002

extract phase (EP) w5 0.133 0.130 0.169 0.196 0.210 0.235 w5 0.131 0.148 0.160 0.181 0.203 0.241 w5 0.126 0.141 0.154 0.184 0.213 0.258

u(w5) 0.004 0.004 0.004 0.005 0.005 0.011 u(w5) 0.002 0.002 0.002 0.002 0.002 0.003 u(w5) 0.004 0.004 0.004 0.004 0.004 0.005

w1 0.034 0.051 0.059 0.080 0.106 0.149 w1 0.049 0.054 0.062 0.083 0.106 0.161 w1 0.048 0.053 0.061 0.076 0.093 0.134

u(w1) 0.006 0.006 0.006 0.005 0.005 0.005 u(w1) 0.003 0.003 0.003 0.003 0.003 0.003 u(w1) 0.006 0.006 0.005 0.005 0.005 0.006

w2 0.000 0.021 0.054 0.091 0.119 0.146 w3 0.016 0.032 0.049 0.078 0.100 0.131 w4 0.016 0.030 0.049 0.074 0.092 0.122

u(w2) 0.004 0.003 0.003 0.003 0.003 0.002 u(w3) 0.002 0.002 0.002 0.002 0.002 0.001 u(w4) 0.004 0.004 0.003 0.003 0.003 0.003

w5 0.966 0.928 0.887 0.829 0.775 0.705 w5 0.935 0.914 0.889 0.839 0.794 0.709 w5 0.936 0.917 0.890 0.850 0.816 0.745

u(w5) 0.005 0.005 0.005 0.005 0.005 0.005 u(w5) 0.002 0.002 0.002 0.002 0.002 0.003 u(w5) 0.004 0.004 0.004 0.004 0.004 0.005

Standard uncertainties u are u(T) = 0.05 K, u(wiOM) = 0.0001, for i = 1 to 5, and u(p) = 0.5 kPa.

Table 6. Constants and Coefficient of Determination (R2) for the Hand (eq 5) and Othmer−Tobias (eq 6) Tests Hand test

Othmer−Tobias test 2

solute

kH

CH

R

n-hexanal (2) 2-nonenal (3) 2,4-decadienal (4)

0.9372 1.0565 0.9489

0.1666 0.0925 −0.0823

0.9594 0.9959 0.9951

Tie Line Data and Correlation. Tie line data for pseudoternary systems investigated in this work are given in Table 5. Table 6 presents the constants and the coefficient of determination (R2) for the semiempirical tests of Hand and Othmer−Tobias used for checking the quality of experimental liquid−liquid equilibrium data presented in Table 5. As one can see, for all

kOT

COT

R2

2.0116 1.5864 1.2275

0.3165 0.0484 −0.1854

0.9379 0.9975 0.9950

pseudoternary systems linearization was achieved, indicating a reasonable goodness of fitting for both tests. Tables 7 and 8 present the parameters adjusted for the NRTL and UNIQUAC models, respectively. Table 9 shows the global deviations (eq 7) between experimental data, and calculated values using NRTL and UNIQUAC, or predicted 3072

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Table 7. NRTL Parameters for Refined Sunflower Seed Oil (1), [n-Hexanal (2), or 2-Nonenal (3), or 2,4-Decadienal (4)] and Anhydrous Ethanol (5) bij [ J·mol−1]

i-j

bji [ J·mol−1]

αij

Refined Sunflower Seed Oil (1) + n-Hexanal (2) + Anhydrous Ethanol (5) 1-2 1786.712 3766.974 0.6000 1-5 8.081 13075.020 0.4730 2-5 −6092.932 14735.068 0.2000 Refined Sunflower Seed Oil (1) + 2-Nonenal (3) + Anhydrous Ethanol (5) 1-3 156728.952 329.525 0.6000 1-5 −5875.695 20481.173 0.2096 3-5 10534.453 −19680.086 0.2637 Refined Sunflower Seed Oil (1) + 2,4-Decadienal (4) + Anhydrous Ethanol (5) 1-4 −71.908 −161.408 0.6000 1-5 −6183.089 21101.622 0.2000 4-5 −826.561 3819.659 0.6000

Table 8. UNIQUAC parameters for Refined Sunflower Seed Oil (1), [n-Hexanal (2), or 2-Nonenal (3), or 2,4-Decadienal (4)] and Anhydrous Ethanol (5) bij [ J·mol−1]

i-j

bji [ J·mol−1]

Sunflower Seed Oil (1) + n-Hexanal (2) + Anhydrous Ethanol (5) 1-2 1428.029 −5691.623 1-5 1970.077 −9788.538 2-5 763.441 −2850.563 Sunflower Seed Oil (1) + 2-Nonenal (3) + Anhydrous Ethanol (5) 1-3 −1845.375 538.090 1-5 −2944.345 317.636 3-5 61.349 −1979.580 Sunflower Seed Oil (1) + 2.4-Decadienal (4) + Anhydrous Ethanol (5) 1-4 −457.353 938.002 1-5 −2928.715 310.029 4-5 102.828 −149.386

values using UNIFAC-LL, UNIFAC-FS, UNIFAC-DMD, and UNIFAC-LYB. Figures 1A−C depict liquid−liquid equilibrium diagrams (experimental binodal curves, and experimental/estimated tie lines) in terms of wsolute versus w5, where the binary system containing anhydrous ethanol (5) + refined sunflower seed oil is partially miscible and the binary system containing anhydrous ethanol (5) or refined sunflower seed oil + solutes (2, 3, or 4) are totally miscible, comprising Type-1 liquid−liquid equilibria. Table 10 presents the partition coefficients for solutes (ksolute) and diluent (k1), together with solvent selectivity (Si/1) for each solute i. Results reveal that n-hexanal, a saturated aldehyde, tends to solubilize in the solvent in higher amounts than unsaturated molecules (2-nonenal and 2,4-decadienal), presenting higher distribution coefficients and better affinity with anhydrous ethanol. All systems showed high solvent selectivity values, especially

Figure 1. Liquid−liquid equilibria for the pseudoternary system composed by refined sunflower seed oil (1), solute (2, 3, or 4), and anhydrous ethanol (5) at 298.15 K and under atmospheric pressure: (×) experimental binodal curve (refined sunflower seed oil rich phase); (+) experimental binodal curve (anhydrous ethanol rich phase); (●) experimental equilibrium data; () NRTL; (---) UNIQUAC. (a) n-Hexanal (2), (b) 2-nonenal (3), and (c) 2,4-decadienal (4).

within a low solute concentration region, which is, in fact, the region of interest in the deodorization process of edible oils, considering that odoriferous compounds are presented in low concentrations in unrefined oils. To illustrate the predictive capacity of the UNIFAC-LL, UNIFAC-FS, UNIFAC-DMD, and UNIFAC-LYB methods,

Table 9. Global Deviations (eq 7) for the NRTL and UNIQUAC Models, and for the UNIFAC-LL, UNIFAC-FS, UNIFAC-DMD, and UNIFAC-LYB Methods for Refined Sunflower Seed Oil (1), [n-Hexanal (2), or 2-Nonenal (3), or 2,4-Decadienal (4)] and Anhydrous Ethanol (5) δw solute

NRTL

UNIQUAC

UNIFAC-LL

UNIFAC-FS

UNIFAC-DMD

UNIFAC-LYB

n-hexanal (2) 2-nonenal (3) 2,4-decadienal (4)

0.7152 0.2955 0.2322

0.8097 0.1337 0.2549

7.5249 6.9782 6.0367

14.7016 9.7144 6.6954

8.8032 8.9667 8.8869

11.0421 11.1918 11.0989

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DOI: 10.1021/acs.jced.6b00152 J. Chem. Eng. Data 2016, 61, 3069−3076

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Table 10. Partition Coefficients for Solutes (ksolute) and for Diluent (k1), and Solvent Selectivity (Si/1) for Model Systems Containing Refined Sunflower Seed Oil (1), [n-Hexanal (2), or 2-Nonenal (3), or 2,4-Decadienal (4)] and Anhydrous Ethanol (5) at T = 298.15 K and p = 0.094 MPaa k1 0.04 0.06 0.07 0.11 0.15 0.22 a

k2

S2/1 b

NA 2.34 1.52 1.76 2.00 2.01

b

NA 39.80 20.44 16.58 13.70 9.35

k1

k3

S3/1

k1

k4

S4/1

0.06 0.07 0.08 0.11 0.15 0.25

1.14 1.04 1.13 1.25 1.24 1.21

19.80 15.69 14.49 11.41 8.33 4.92

0.06 0.06 0.08 0.10 0.13 0.21

1.07 1.04 1.18 1.10 1.03 1.04

19.14 16.41 15.64 10.84 7.76 4.88

Standard uncertainties u are u(T) = 0.05 K and u(p) = 0.5 kPa. bTie line for the binary system solvent−diluent. k2 and S2/1 are NA (not applicable).

As shown in Figure 2, the UNIFAC-LL, UNIFAC-DMD, and UNIFAC-LYB methods predict a larger heterogeneous region for all systems investigated, and correct tie line inclinations (ksolute > 1) in comparison with experimental results. On the other hand, UNIFAC-FS predicts a shorter two-phase coexistence region than the experimental data with incorrect tie line inclinations for 2-nonenal and 2,4-decadienal (ksolute < 1). UNIFAC-LL predicts that refined sunflower seed oil is immiscible in anhydrous ethanol for all studied tie lines, which is not the case as revealed by experimental data. Similar behavior is observed for the UNIFAC-DMD and UNIFAC-LYB methods, since these two UNIFAC modifications virtually predicted immiscibility between diluent and solvent. To sum up, Hirata et al.6 report the same observation for carboxylic acids as solutes. These results are an indicative of the necessity of new experimental liquid−liquid equilibrium data for fatty systems in general, allowing a combination of different functional groups in a variety of mixtures of interest in lipid technology and refinement of group contribution methods.

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CONCLUSION Novel liquid−liquid equilibrium data for the pseudoternary model systems composed of refined sunflower seed oil, n-hexanal, or 2-nonenal, or 2,4-decadienal, and anhydrous ethanol at 298.15 K and under atmospheric pressure were measured experimentally, and were correlated using NRTL and UNIQUAC models, with acceptable global deviations. Further, this work compared the predictive capacity of four versions of the UNIFAC method, namely UNIFAC-LL, UNIFAC-FS, which was readjusted for lipid technology systems, UNIFAC-DMD, and UNIFAC-LYB. In general, the four methods predicted experimental values poorly, indicating the necessity of improvements of group contribution methods based on additional experimental data.

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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.6b00152. Matrix of UNIFAC-LL, UNIFAC-DMD, UNIFAC-LYB, and UNIFAC-FS interaction parameters; calculated liquid−liquid equilibrium data for the studied systems (PDF)

Figure 2. Liquid−liquid equilibrium for pseudoternary system composed by refined sunflower seed oil (1), solute (2, 3, or 4) and anhydrous ethanol (5) at 298.15 K and under atmospheric pressure: (●) experimental equilibrium data; (×) UNIFAC-LL; (∗) UNIFACFS; (○) UNIFAC-DMD; (△) UNIFAC-LYB. (a) n-Hexanal (2), (b) 2-nonenal (3), and (c) 2,4-decadienal (4).

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel.: +55 19 35213961. Fax: +55 19 35213965.

Figure 2 presents predicted and experimental data for the three pseudoternary systems studied. The values of the calculated tie lines by these four versions of UNIFAC method are presented in Table S5 (Supporting Information).

Notes

The authors declare no competing financial interest. 3074

DOI: 10.1021/acs.jced.6b00152 J. Chem. Eng. Data 2016, 61, 3069−3076

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Funding

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P.O.B.H. acknowledges CNPq and FAPESP (2013/11868-1) for his scholarships. R.C. acknowledges the FAPESP (2013/ 12735-5) for financial support and CNPq (304303/2013-5) for her individual grant.

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ACKNOWLEDGMENTS The authors are thankful to Professor Geci José Pereira da Silva (Institute of Mathematics and Statistics, Federal University of Goiás) for his support with uncertainty calculations.

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