Solubilities of n-Butyl Esters in Supercritical Carbon Dioxide - Journal

Article pubs.acs.org/jced

Solubilities of n‑Butyl Esters in Supercritical Carbon Dioxide Ram C. Narayan and Giridhar Madras* Department of Chemical Engineering, Indian Institute of Science, Bangalore 560012, India ABSTRACT: The solubilities of butyl stearate and butyl laurate were determined in the temperature range of 308 K to 323 K and 313 K to 328 K, respectively, at pressures of 10 MPa to 16 MPa. The solubility of butyl laurate was higher than that of butyl stearate by almost an order in magnitude. Retrograde behavior was observed throughout the investigated pressure range. Semiempirical models such as Mendez-Teja, Chrastil, and other density-based models were used to correlate the experimental data of our work as well as several other liquid solutes.

1. INTRODUCTION In the vicinity of the critical point of a fluid, the physical properties of a fluid change significantly. This is the basis of all supercritical fluid technologies, whose initial applications focused on the extraction of materials such as coffee, tea, hops, spices, and flavors, in which the tunable solvating power of the fluid was exploited.1 The use of these fluids also results in high rates of mass transfer and permits simpler downstream processing.2 Today, the horizons of this technology have widened to encompass many other applications such as the synthesis of biodiesel3 and other esters,4 lipid processing,5 pollution abatement,6 fractionation,7 material applications such as impregnation 8 and particle design, 9 and analytical applications.10 The solvent of choice for most applications is supercritical CO2 (SC-CO2) because it is cheap, nontoxic, and not flammable. Supercritical fluids have been extensively used for lipid processing. 5 In the purview of developing renewable technologies, there has been an impetus in the field of developing biodegradable and biobased lubricants.11,12 Many esters have been synthesized using various lipid sources.13,14 Fatty acid esters of higher alcohols have been investigated as a potential lubricant base stock.15−17 Reactions such as esterification, transesterification, and interesterification could be conducted in a supercritical fluid. It can also be used in further fractionation to obtain pure lubricant basestock. Thus, it is relevant to determine the solubility of fatty acid esters of higher alcohols in SC-CO2 to design such processes and operations. In this study, the solubilities of butyl stearate and butyl laurate in SC-CO2 were measured using a dynamic solubility measurement apparatus. To the best of our knowledge, this is the first study toward investigating the solubility of fatty acid esters of a higher alcohol in SC-CO2. These esters have been studied for potential use as lubricants,18,19 plasticizers, solvents, and flavors.20,21 The solubility data are correlated by various semiempirical models such as the Chrastil model after testing its consistency with the model developed by Mendez-Santiago © XXXX American Chemical Society

and Teja. The behavior of these systems is compared with other liquid solutes, especially other fatty acid methyl and ethyl esters.

2. MATERIALS Carbon dioxide gas of 0.99 mass fraction was purchased from Noble Gases (Bangalore, India). The purity was increased to 0.999 mass fraction by passing the gas through a silica bed column. Butyl stearate (CAS no. 123-95-5) was procured from TCI Chemicals (Japan). Gas chromatography−mass spectrometry (GC−MS) indicated that the sample was composed of 92.3 % butyl stearate, 6.1 % butyl eicosanoate, 1.2 % butyl palmitate and 0.4 % butyl docosanoate. Butyl laurate (CAS no. 106-18-3) with > 99 % (GC) purity was obtained from SigmaAldrich (USA). 3. EXPERIMENT AND PROCEDURE A flow saturation technique was used to measure the solubility of the liquid solute in supercritical conditions. Carbon dioxide from a gas cylinder was passed through a pump (PU-1580-CO2, Jasco International Company, Japan), where it is cooled to a liquid and then pumped to the desired pressure (within ± 0.2 MPa), maintained by a suitable back-pressure regulator (JascoPU-1580-81-BP). An appropriate volume of liquid solute (∼30 mL) was introduced into the high pressure vessel of volume 50 mL (EV-3-50-2 from Jasco). This was then placed in a thermostat, with a temperature control of ± 0.1 K. After sufficient time, the supercritical carbon dioxide which was passed through the column is completely saturated with liquid solute. The mixture was expanded and collected into a glass trap. The amount of solute collected was measured gravimetrically. The flow lines were flushed with hexane after each experiment in order to remove remaining traces of esters. The experiments for determining the solubility were carried out at a Received: April 8, 2014 Accepted: October 17, 2014

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dx.doi.org/10.1021/je500309x | J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

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constant flow rate of 0.1 mL min−1 to ensure that saturation is attained. This flow rate was selected by conducting experiments by varying flow rate between (0.05 and 0.3) mL·min−1 and keeping other parameters such as temperature and pressure constant and determining the flow rate below which the solubility is unchanged. The solubility was expressed as mole fraction and calculated by using the expression: y2 =

Considering the modifications proposed by both del Valle and Aguilera and Adachi and Lu, a single equation can be formulated as eq 7, ln c(kg·m−3) = (α + βρ(kg·m−3) + γρ2 (kg·m−3)2 ) a b × ln ρ(kg·m−3) + + 2 2 +d T (K) T (K )

w M w M

+

(7)

⎛ Qtρ ⎞ ⎜ ⎟ ⎝ MCO2 ⎠

5. RESULTS AND DISCUSSION To validate the apparatus used for liquid solubility experiments, the solubility of 1-octanol was measured at 328 K at different pressures. This is represented in Figure 1. It can be seen that the data matches well with the published data.27−29

(1)

where w represents the weight of solute collected, M and Mco2 represents molecular weight of solute and carbon dioxide, respectively. Q is the flow rate of carbon dioxide through the liquid column, and t is the sample collection time. The density of carbon dioxide ρ is calculated from the 27-parameter equation of state.22 Each experiment was repeated in triplicate, and the standard deviation was less ± 5 %.

4. MODELS AND CORRELATIONS Mendez-Santiago and Teja23 (MT) related the enhancement factor to the density of the supercritical fluid as given by eq 2, ⎛ yp ⎞ T (K ) ln(E) = T ln⎜⎜ 2sub ⎟⎟ = A + Bρ(kg·m−3) ⎝ p2 ⎠

(2)

Psub 2

In the case of liquids, the sublimation pressure, can be replaced with the vapor pressure Pvap . Using the Antoine equation 2 for correlating vapor pressure with temperature a modified version of the MT model is given by eq 3, T (K) ln(y2 p) = A + Bρ(kg·m−3) + cT (K)

Figure 1. Solubility of 1-octanol in SC-CO2 at 328 K at different pressures: ■, ref 27; ●, ref 28 ; ▲, ref 29 ; ○, our data.

(3)

The solubilities of butyl stearate and butyl laurate were measured at temperatures, T= (308 to 323) K and T= (313 to 328) K, respectively, for pressures p= (10 to 16) MPa and are shown in Table 1. The solubilities of butyl laurate at 308 K and butyl stearate at 328 K were very high and very low, respectively, for which the equipment may not give accurate values. The densities of carbon dioxide at different pressures and temperatures were calculated using the 27-parameter equation of state.22 The graph of solubility (c, kg.m−3) with pressure (p, MPa) is plotted for both butyl laurate and butyl stearate in Figure 2. As mentioned earlier, the MT model was used to test the data consistency. The experimental data were regressed to minimize the average absolute relative deviation (AARD) of the solubility of the solute in supercritical carbon dioxide, defined as

A plot of T(ln(y2p) − cT) with ρ will be linear and provides an excellent tool to test the consistency of data at different temperatures. One of the first empirical models for correlating the solubilities of solids and liquids in supercritical fluids was developed by Chrastil.24 It was derived by considering equilibrium between the hypothesized solvato-complex with the solute and solvent molecules. The model is mathematically described by eq 4, a ln c(kg·m−3) = κ ln ρ(kg·m−3) + +b T (K) (4) relating the concentration of solute (c, kg·m−3) in the vapor/ supercritical phase to the density of carbon dioxide (ρ, kg·m−3) and the temperature of the system (T, K). κ indicates the association number, which is dimensionless. del Valle and Aguilera in their study on the solubility of vegetable oils25 empirically correlated the parameter with temperature yielding the following eq 5, ln c(kg·m−3) = κ ln ρ(k kg·m−3) +

AARD(%) =

(8)

where N represents the number of data points and y2 represents the solubility of solute mole fraction. The superscripts “calc” and “exp” represent the calculated and experimental values, respectively. All multiple linear regressions were done using the software Polymath 5.1. In case of the Chrastil model and derived equations such as those from Adachi and Lu or del Valle Aguilera, AARD (%) values are calculated in terms of solubilities (c) in kg·m−3 rather than mole fraction (y2). It can be observed from Figure 3, that different isotherms almost collapse to a single line in case of both butyl stearate and butyl laurate. The AARD (%) values for the MT model for these compounds are 10.2% and 17.3%, respectively.

a b + 2 2 +d T (K) T (K ) (5)

Both Chrastil and del Valle and Aguilera assumed that the association number is a constant, independent of the model parameters, temperature (T) and density (ρ). Adachi and Lu in ref 26 proposed a quadratic expression for the association number with density as a parameter, given by eq 6, κ = α + βρ(kg·m−3) + γρ2 (kg·m−3)2

⎛ N |y calc − y exp | ⎞ 1⎜ ∑ 2 exp 2 ⎟⎟100 N ⎜⎝ i = 1 y2 ⎠

(6) B



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Table 1. Experimental Mole Fraction Solubilities (y2) of Liquid Solutes, Butyl Stearate and Butyl Laurate (2, Vapor Phase Mole Fraction of Liquid Solute) in SC-CO2 (1) at Temperature T and Pressure pa T

p

butyl stearate

butyl laurate

K

MPa

y2·10

y2·103

308

10 12 13 14 16 10 12 13 14 16 10 12 13 14 16 10 12 13 14 16 10 12 13 14 16

3.0 4.6 5.4 5.5 6.0 1.3 2.7 4.6 5.0 5.5 0.5 2.2 2.8 3.8 5.1 0.3 0.7 1.9 2.1 3.3

313

318

323

328

3

15.8 16.5 19.4 20.0 23.0 9.9 12.0 15.9 16.7 19.0 2.5 13.0 15.8 16.1 19.3 1.3 5.4 11.5 13.5 18.2

Figure 2. Solubility of (a) butyl stearate at ●, 308 K; ■, 313 K; ▲, 318 K; ⧫, 323 K; and (b) butyl laurate at ■, 313 K; ▲, 318 K; ⧫, 323 K; ▼, 328 K in SC-CO2. The solid lines represent the model given by eq 7 with b = γ = 0.

a Standard uncertainties u are u(T) = 0.1 K, u(p) = 0.2 MPa, and ur(y2) = 0.05.

In general, an isothermal increase in pressure leads to an increase in solubility. At a particular temperature and pressure, the solubility of butyl stearate was always lower than that of butyl laurate. This phenomenon was also observed in the case of other liquid and solid compounds (homologous series). For example, in the case of solids, solubility of lauric acid was always higher than that of stearic acid, myristic acid, or palmitic acid.30−35 In the case of liquids, solubility of methyl stearate was lower than that of methyl myristate or methyl palmitate.36 Considering the effect of the alkyl group, the solubility of butyl stearate was lower than that of methyl and ethyl stearate.36,37 The fatty acid esters in general have a considerably higher solubility than corresponding fatty acids. This is shown in Figure 4 where solubility is plotted against pressure for homologous fatty acid esters such as methyl, ethyl, butyl stearate, and stearic acid. Thus, esterification/transesterification in general increases the solubility of fatty acids and triglycerides. This is due to lower polarity of esters as compared to the corresponding fatty acid. Figure 4 represents the variation of solubility with pressure for stearic acid30,38 and its esters: methyl stearate,36 ethyl stearate,37 and butyl stearate (this work). It can be seen that the esters have a higher solubility than the corresponding fatty acid. As the number of carbon atoms in the alcohol moiety of the ester increases, the solubility decreases. This can be attributed to the lower vapor pressure of butyl stearate or ethyl stearate when compared to methyl stearate. An exhaustive review39 on the solubility of various lipid classes like fatty acids, triglycerides and fatty acid esters discusses

Figure 3. Solubility of (a) butyl stearate at ●, 308 K; ■, 313 K; ▲, 318 K; ⧫, 323 K; and (b) butyl laurate at ■, 313 K; ▲, 318 K; ⧫, 323 K ; ▼, 328 K in SC-CO2. The solid lines represent the correlation based on the MT-model (eq 3). C



Article

Case 1: a=b=β=γ=0

Three-parameter models: Case (2a): a=b=γ=0

Case 2(b); Chrastil equation: b=β=γ=0

Four-parameter models: Case 3(a); Adachi and Lu model with four parameters: Figure 4. Solubilities of ■, stearic acid (ref 38); ●, methyl stearate (ref 36); ▲, ethyl stearate (ref 37); and ▼, butyl stearate at 323 K in SC-CO2. The solid lines represent the model given by eq 7, with b = γ = 0.

b=γ=0

Case 3(b); Valle and Aguilera model:

β=γ=0

various general patterns on the solubilities in SC-CO2. These patterns were based on the literature on the solubility data of different lipid classes. According to this review, liquid solutes like oleic acid, linoleic acid, fatty acid esters (methyl and ethyl esters) etc. show retrograde solubility behavior in the temperature and pressure range studied. The temperature range for these methyl and ethyl esters was 313 K to 343 K and pressures up to 20 MPa. An inverse relationship exists between solubility and temperature at isobaric conditions. In the temperature and pressure ranges in which we measured the solubility data of butyl laurate butyl stearate, no crossover region was observed, complete retrograde behavior was observed, as with other liquid solutes. As described earlier, the experimental data was fitted according to eq 2 (Chrastil equation) and its modified forms such as eq 5 and 7. In the case of butyl stearate and butyl laurate an AARD of 13.3 % and 13.7 % was estimated from the Chrastil equation. The AARD (%) values for the MT-model and Chrastil model of different liquids is shown in Table 2. To represent experimental data better, different modifications of the Chrastil model are combined into eq 7. On the basis of eq 7, seven equations were modeled: Two-parameter model:

Five-parameter models: Case 4(a); Adachi and Lu model with five parameters:

b=0 Case 4(b); Sparks model: γ=0

The AARD (%) of the above-defined cases are shown in Table 2. Case 1 is a simple linear correlation between the logarithms of solubility and density. In the case of certain compounds like butyl laurate, butyl stearate, ethyl EPA, and ethyl DHA, the AARD (%) values are almost the same as in case 2(b), but are higher than that of case 2(a) suggesting a linear correlation of association number with density. Thus, these compounds have a strong density dependence and weak temperature dependence of solubility. In cases 1 and 2(a), the AARD (%) for triolein was found to be greater than 100 %. The average shown in the table does not consider the case of triolein. Among the three parameter models, case 2(a) showed a good correlation with AARD (%), 8.9 % and 8.2 % for butyl stearate and butyl laurate, respectively. Among the four parameter models, case 3(a) performed much better than case 3(b).

Table 2. AARD (%) Values of Different Models for Modeling the Solubilities of Various Liquids in SC-CO2 AARD (%) cmpd

T/K

p/MPa

N

MT

case 1

case 2(a)

case 2(b)

case 3(a)

case 3(b)

case 4(a)

case 4(b)

butyl stearate butyl laurate methyl palmitate methyl oleate methyl oleate methyl stearate methyl linoleate ethyl linoleate ethyl oleate ethyl stearate ethyl EPA ethyl DHA oleic acid 1-octanol 1-octanol triolein average

308−323 313−328 313−343 313−353 313−333 313−343 313−333 313−333 313−333 313−333 313−333 313−333 308−333 313−348 308−348 313−353

10.0−16.0 10.0−16.0 8.6−18.3 9.5−22.3 9.5−18.2 9.0−20.4 7.8−20.3 9.0−17.0 9.1−18.6 8.9−18.3 9.0−21.1 9.0−21.1 9.6-31.1 8.5−19.0 8.0−16.0 8.1−2.5

18 20 16 14 20 12 19 16 21 19 24 26 33 13 21 20

10.2 17.3 22.8 14.9 20.3 19.9 21.9 17.4 14.5 23.5 14.6 14.1 14.4 19.8 19.6 47.1 19.5

13.3 14.5 32.0 49.5 28.7 34.7 27.9 25.5 23.8 26.5 16.9 19.3 33.9 42.7 24.5 >100 27.5

10.1 8.0 18.9 49.2 28.4 30.0 20.7 22.4 22.4 23.1 12.9 19.0 30.9 42.0 21.0 >100 23.9

13.3 13.7 31.5 26.0 19.1 12.3 27.5 17.7 16.5 24.6 16.9 19.3 13.9 24.6 13.6 3.5 18.4

8.9 8.2 15.9 8.2 16.7 10.6 20.7 14.1 11.1 15.1 13.1 9.0 10.5 14.4 12.5 2.5 12.0

13.2 13.7 31.4 25.9 19.1 12.3 27.5 17.7 15.1 23.5 14.9 14.1 13.8 24.6 13.3 3.4 17.7

7.2 7.8 12.4 7.9 10.8 10.5 20.7 13.9 11.0 14.5 12.9 8.3 10.1 12.4 12.4 2.4 11.0

8.9 8.2 15.9 7.4 16.3 10.6 20.7 14.1 11.0 15.1 8.5 8.8 10.5 14.2 12.4 2.5 11.6

D

ref this work this work 36 41 42 36 43 44, 37 37 37 37 37 33 35 45 46, 27 28 24



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Among the five parameter models, case 4(a) had lower AARD (%) than case 4(b), proposed by Sparks et al.40 These indicated that the compensation for temperature dependence of heat of vaporization is not necessary. Cases 4(a) and 4(b) have five parameters and have a marginally low AARD (%) compared to case 3(a). This indicates that Chrastil (case 2(b)) is the best three parameter model and the Adachi and Lu model (case 3(a), b = γ = 0) is the best four-parameter model. To determine the best overall model, Akaike information criterion, which deals with the trade-off between goodness of fit and model complexity, may be used to compare models with different numbers of parameters.

(8) Guney, O.; Akgerman, A. Synthesis of controlled release products in supercritical medium. AIChE J. 2002, 48, 856−866. (9) Hezave, A. Z.; Esmaeilzadeh, F. Micronization of drug particles via RESS process. J. Supercrit. Fluids 2010, 52, 84−98. (10) Guiochon, G.; Tarafder, A. Fundamental challenges and opportunities for preparative supercritical fluid chromatography. J. Chromatogr. A 2011, 1218, 1037−1114. (11) Wagner, H.; Luther, R.; Mang, T. Lubricant base fluids based on renewable raw materials: Their catalytic manufacture and modification. Appl. Catal., A 2001, 221, 429−442. (12) Gryglewicz, S.; Oko, F. Synthesis and biosynthesis of oligomeric sebacates as lubricant oils. Ind. Eng. Chem. Res. 2005, 44, 1640−1644. (13) Madankar, C. S.; Dalai, A. K.; Naik, S. Green synthesis of biolubricant base stock from canola oil. Ind. Crop. Prod 2013, 44, 139− 144. (14) Chowdhury, A.; Mitra, D.; Biswas, D. Biolubricant synthesis from waste cooking oil via enzymatic hydrolysis followed by chemical esterification. J. Chem. Technol. Biotechnol. 2013, 88, 139−144. (15) Dörmő , N.; Bélafi-Bakó, K.; Bartha, L.; Ehrenstein, U.; Gubicza, L. Manufacture of an environmental-safe biolubricant from fusel oil by enzymatic esterification in solvent-free system. Biochem. Eng. J. 2004, 21, 229−234. (16) Oh, J.; Yang, S.; Kim, C.; Choi, I.; Kim, J. H.; Lee, H. Synthesis of biolubricants using sulfated zirconia catalysts. Appl. Catal., A 2013, 455, 164−171. (17) Salimon, J.; Salih, N.; Yousif, E. Biolubricants: Raw materials, chemical modifications and environmental benefits. Eur. J. Lipid Sci. Technol. 2010, 112, 519−530. (18) Chen, L.; Yin, P.; Qu, R.; Chen, X.; Xu, Q.; Tang, Q. Production of n-butyl stearate over PA/NaY catalyst. Chem. Eng. J. 2011, 173, 583−591. (19) Zhang, X.; Wang, S. T.; Sun, J. L.; Ding, G. H. Research on Lubricating Properties of Alcohol and Ester in Stainless Steel Cold Rolling Process. Adv.Mater.Res. 2012, 557, 1427−1431. (20) White, C.; Pejcic, B.; Myers, M.; Qi, X. Development of a plasticizer-poly (methyl methacrylate) membrane for sensing petroleum hydrocarbons in water. Sensor. Actuat. B-Chem. 2014, 193, 70− 77. (21) Mugo, S. M.; Ayton, K. Lipase immobilized microstructured fiber based flow-through microreactor for facile lipid transformations. J. Mol. Catal. B 2010, 67, 202−207. (22) Span, R.; Wagner, W. A new equation of state for carbon dioxide covering the fluid region from the triple point temperature to 1100 K at pressures up to 800 MPa. J. Phys. Chem. Ref. Data 1996, 25, 1509− 1596. (23) Méndez-Santiago, J.; Teja, A. S. The solubility of solids in supercritical fluids. Fluid Phase Equilib. 1999, 158, 501−510. (24) Chrastil, J. Solubility of solids and liquids in supercritical gases. J. Phys. Chem. 1982, 86, 3016−3021. (25) Del Valle, J. M.; Aguilera, J. M. An improved equation for predicting the solubility of vegetable oils in supercritical carbon dioxide. Ind. Eng. Chem. Res. 1988, 27, 1551−1553. (26) Adachi, Y.; Lu, B. C.-Y. Supercritical fluid extraction with carbon dioxide and ethylene. Fluid Phase Equilib. 1983, 14, 147−156. (27) Weng, W.; Lee, M. Phase equilibrium measurements for the binary mixtures of 1-octanol plus CO2, C2H6, and C2H4. Fluid Phase Equilib. 1992, 73, 117−127. (28) Fourie, F.; Schwarz, C.; Knoetze, J. Phase equilibria of alcohols in supercritical fluids: Part I. The effect of the position of the hydroxyl group for linear C8 alcohols in supercritical carbon dioxide. J. Supercrit. Fluids 2008, 47, 161−167. (29) Chang, C. J.; Chiu, K.-L.; Day, C.-Y. A new apparatus for the determination of P−x−y diagrams and Henry’s constants in high pressure alcohols with critical carbon dioxide. J. Supercrit. Fluids 1998, 12, 223−237. (30) Garlapati, C.; Madras, G. Solubilities of palmitic and stearic fatty acids in supercritical carbon dioxide. J. Chem. Thermodyn. 2010, 42, 193−197.

6. CONCLUSIONS The solubilities of butyl stearate and butyl laurate in SC-CO2 were determined in the temperature range T = (308 to 323) K and T = (313 to 328) K, respectively, in the pressure range p = (10 to 16) MPa using a dynamic flow technique. The pure component solubility of butyl laurate was about a magnitude higher than that of butyl stearate. The solubility data of esters investigated in this work and several other liquid solutes was modeled using simple empirical models. The solubility of butyl stearate and butyl laurate was well correlated using a three parameter simple density correlation. Adachi and Lu equation with four parameters seemed sufficient to correlate the data for liquid solutes with an average absolute relative deviation (AARD %) of around 12 %.

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AUTHOR INFORMATION

Corresponding Author

*Tel. +91 80 22932321. Fax: +91 80 23600683. E-mail: [email protected]. Funding

The authors thank the council of scientific and industrial research (CSIR), India for financial support. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors gratefully acknowledge the help of Prof. K.R. Prabhu of Organic Chemistry, Indian Institute of Science, for help in GC−MS analysis.

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REFERENCES

(1) Daintree, L.; Kordikowski, A.; York, P. Separation processes for organic molecules using SCF technologies. Adv. Drug Delivery Rev. 2008, 60, 351−372. (2) Rezaei, K.; Temelli, F.; Jenab, E. Effects of pressure and temperature on enzymatic reactions in supercritical fluids. Biotechnol.Adv. 2007, 25, 272−280. (3) Varma, M. N.; Deshpande, P. A.; Madras, G. Synthesis of biodiesel in supercritical alcohols and supercritical carbon dioxide. Fuel 2010, 89, 1641−1646. (4) Varma, M. N.; Madras, G. Synthesis of isoamyl laurate and isoamyl stearate in supercritical carbon dioxide. Appl. Biochem. Biotechnol. 2007, 141, 139−147. (5) Temelli, F. Perspectives on supercritical fluid processing of fats and oils. J. Supercrit. Fluids 2009, 47, 583−590. (6) Madras, G.; Erkey, C.; Akgerman, A. Supercritical extraction of organic contaminants from soil combined with adsorption onto activated carbon. Environ. Prog. 1994, 13, 45−50. (7) Perretti, G.; Motori, A.; Bravi, E.; Favati, F.; Montanari, L.; Fantozzi, P. Supercritical carbon dioxide fractionation of fish oil fatty acid ethyl esters. J. Supercrit. Fluids 2007, 40, 349−353. E



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(31) Garlapati, C.; Madras, G. Solubilities of hexadecanoic and octadecanoic acids in supercritical CO2 with and without cosolvents. J. Chem. Eng. Data 2008, 53, 2913−2917. (32) Garlapati, C.; Madras, G. Solubilities of dodecanoic and tetradecanoic acids in supercritical CO2 with and without entrainers. J. Chem. Eng. Data 2008, 53, 2637−2641. (33) Yu, Z.-R.; Singh, B.; Rizvi, S. S.; Zollweg, J. A. Solubilities of fatty acids, fatty acid esters, triglycerides, and fats and oils in supercritical carbon dioxide. J. Supercrit. Fluids 1994, 7, 51−59. (34) Bamberger, T.; Erickson, J. C.; Cooney, C. L.; Kumar, S. K. Measurement and model prediction of solubilities of pure fatty acids, pure triglycerides, and mixtures of triglycerides in supercritical carbon dioxide. J. Chem. Eng. Data 1988, 33, 327−333. (35) Maheshwari, P.; Nikolov, Z.; White, T.; Hartel, R. Solubility of fatty acids in supercritical carbon dioxide. J. Am. Oil Chem. Soc. 1992, 69, 1069−1076. (36) Inomata, H.; Kondo, T.; Hirohama, S.; Arai, K.; Suzuki, Y.; Konno, M. Vapourliquid equilibria for binary mixtures of carbon dioxide and fatty acid methyl esters. Fluid Phase Equilib. 1989, 46, 41− 52. (37) Bharath, R.; Inomata, H.; Arai, K.; Shoji, K.; Noguchi, Y. Vapor−Liquid equilibria for binary mixtures of carbon dioxide and fatty acid ethyl esters. Fluid Phase Equilib. 1989, 50, 315−327. (38) Noh, M. J.; Kim, T. G.; Hong, I. K.; Yoo, K.-P. Measurements and correlation of effect of cosolvents on the solubilities of complex molecules in supercritical carbon dioxide. Korean J. Chem. Eng. 1995, 12, 48−55. (39) Gücļ ü-Ü stündag, Ö .; Temelli, F. Correlating the solubility behavior of fatty acids, mono-, di-, and triglycerides, and fatty acid esters in supercritical carbon dioxide. Ind. Eng. Chem. Res. 2000, 39, 4756−4766. (40) Sparks, D. L.; Hernandez, R.; Estévez, L. A. Evaluation of density-based models for the solubility of solids in supercritical carbon dioxide and formulation of a new model. Chem. Eng. Sci. 2008, 63, 4292−4301. (41) Fang, T.; Goto, M.; Yun, Z.; Ding, X.-l.; Hirose, T. Phase equilibria for binary systems of methyl oleate−supercritical CO2 and α-tocopherol−supercritical CO2. J. Supercrit. Fluids 2004, 30, 1−16. (42) Crampon, C.; Charbit, G.; Neau, E. High-pressure apparatus for phase equilibria studies: Solubility of fatty acid esters in supercritical CO2. J. Supercrit. Fluids 1999, 16, 11−20. (43) Chang, C.-m. J.; Lee, M.-s.; Li, B.-c.; Chen, P.-y. Vapor−liquid equilibria and densities of CO2 with four unsaturated fatty acid esters at elevated pressures. Fluid Phase Equilib. 2005, 233, 56−65. (44) Zou, M.; Yu, Z.; Kashulines, P.; Rizvi, S.; Zollweg, J. Fluid− liquid phase equilibria of fatty acids and fatty acid methyl esters in supercritical carbon dioxide. J. Supercrit. Fluids 1990, 3, 23−28. (45) Nilsson, W. B.; Gauglitz, E. J.; Hudson, J. K. Solubilities of methyl oleate, oleic acid, oleyl glycerols, and oleyl glycerol mixtures in supercritical carbon dioxide. J. Am. Oil Chem. Soc. 1991, 68, 87−91. (46) Foster, N.; Yun, S.; Ting, S. Solubility of oleic acid in supercritical carbon dioxide. J. Supercrit. Fluids 1991, 4, 127−130.

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Solubilities of n-Butyl Esters in Supercritical Carbon Dioxide - Journal

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