Effect of Temperature and Initial Acid Concentration on the Reactive

Article pubs.acs.org/jced

Effect of Temperature and Initial Acid Concentration on the Reactive Extraction of Carboxylic Acids Hasan Uslu† and Ş. Iṡ mail Kırbaşlar‡ Chemical Engineering Department, Beykent University, Ayazağa, Iṡ tanbul, Turkey Chemical Engineering Department, Iṡ tanbul University, Avcılar, Iṡ tanbul, Turkey

† ‡

ABSTRACT: Temperature effect and initial acid concentration are significant factors of study on the reactive extraction process. Both the effect of temperature and of initial acid concentration on the extraction of levulinic acid and malic acid have been studied and compared to each other. Extractions have been carried out at the temperatures 298 K, 318 K, and 328 K. The results showed that an increase in temperature reduced distribution coefficients for all solvents used as the organic phase. The enthalpy and entropy of reaction have been calculated. Reactive extraction of these acids by amines resulted in negative values of enthalpy. Thus, the reactive extraction process is an exothermic process. Different initial concentrations of both acids have been studied in the range of 0.08 wt % to 0.15 wt %. For all solvents in organic phase the distribution coefficients decreased with increasing initial concentration of acids.

1. INTRODUCTION Industrial production of the carboxylic acids is expensive and harmful to the environment. Biocultivation is a ecofriendly choice for production, but to date commercialization is still unavailable. The reason for this is the high price of improvement and separation of the product acid. Traditionally, propionic acid has been extracted from the fermentation medium by calcium salt precipitation. This method is expensive and unfriendly to the environment. The fermented medium contains either the pure acid or its salt or a mixture of both. The search for an advantageous process allowing for the removal of carboxylic acid is based on an approach that removes acids from the fermentation broth or other mixture, while leaving the soluble salts behind in the fermentation broth. Industrial scale fermenters for production of carboxylic acids operate at a different temperatures from 0 °C to 100 °C according to product selectivity. Therefore, the reactive extraction process for the recovery of carboxylic acids requires an extractant that can operate efficiently in different operation ranges.1 Some studies on the effect of temperature and initial acid concentration on the recovery of carboxylic acids from aqueous fermentation media have been reported in literature. Baniel et al.2,3 have studied the temperature effect on the citric acid extraction by trioctyl amine using some modifiers such as alcohol(octan-1-ol), 1,2-dimethylbenzene, and nitrobenzene. The results showed a quick decrease of distribution coefficient with increasing temperature. Wennersten4 reported experimental data for the citric acid extraction by using Alamine 335 diluted with different solvents at different temperatures (25 to 60) °C. King and Tamada5 have investigated the effect of temperature on the succinic and lactic acid extraction by © 2013 American Chemical Society

Alamine 336 in methyl isobutyl ketone (MIBK) in a temperature range from 0 °C to 75 °C . Harrington and Hossain6 studied the effect of temperatures (10 to 40) °C on the lactic acid extraction using 20% trioctylamine (TOA) in sunflower oil. Keshav et al.7 studied the temperature effect (32 to 60) °C on the reactive extraction for some carboxylic acids (acrylic, propionic, and butyric acid) using quaternary amine extractant (Aliquat 336) in oleyl alcohol. They observed that the distribution coefficient decreases with increasing temperature. Apart from the above-mentioned works, there are no significant studies on the extraction of levulinic acid and malic acid in terms of temperature and initial acid concentration effects. Other critical factors as the effect of solvent, pH, and kinetics were studied by Uslu et al. in previous studies.8−15 In this study other parts which need process design for the reactive extraction of malic acid and levulinic acid by different amines [secondary amine “Amberlite LA-2”, tertiary amine “trioctyl amine” (TOA), quaternary amine “trioctyl methyl ammonium chloride” (TOMAC)] in 3-methyl-1butanol were studied. 3-Methyl-1-butanol was chosen as it gave the highest distribution coefficients in previous studies.

2. MATERIALS AND METHODS 2.1. Materials. Amines Amberlite La-2 (M = 353 g·mol−1 to 395 g·mol−1) (purity > 0.99 wt %), TOA (M = 353.67 g·mol−1) (purity > 0.99 wt %), TOMAC (M = 404.16 g·mol−1) (purity > 0.99 wt %); acids levulinic acid (purity > 0.99 wt %), malic acid Received: March 5, 2013 Accepted: May 9, 2013 Published: May 24, 2013 1822

dx.doi.org/10.1021/je4002202 | J. Chem. Eng. Data 2013, 58, 1822−1826

Journal of Chemical & Engineering Data

Article

Table 1. Effect of Temperature on Levulinic Acid (0.08 wt %) Extraction in Different Amine Concentration Dissolved in 3Methyl-1-butanola 298 K extractants

Cs/mol·kg−1

D

Amberlite LA-2

0.590 0.861 1.158 1.431 1.731 0.371 0.743 1.115 1.487 1.859 0.464 0.763 1.101 1.393 1.692

11.461 32.155 45.349 57.447 68.017 1.107 1.871 2.871 5.207 11.303 0.757 1.069 1.400 1.778 2.588

TOA

TOMAC

a

318 K

KE /kg·mol−1

9.383 20.657 24.266 30.583 35.095 1.056 1.767 2.684 4.741 9.439 0.731 1.026 1.335 1.681 2.427

39.29

6.08

1.53

338 K

KE /kg·mol−1

D

D

KE /kg·mol−1

8.594 17.04 19.486 23.452 26.071 1.026 1.712 2.569 4.468 8.569 0.709 0.997 1.289 1.619 2.328

20.27

5.08

1.43

15.06

4.61

1.38

Cs is the concentration of amine in the organic phase. D is the distribution coefficient.

Table 2. Effect of Temperature on Malic Acid (0.08 wt %) Extraction in Different Amine Concentration Dissolved in 3-Methyl1-butanola 298 K extractants Amberlite LA-2

TOA

TOMAC

a

Cs/mol·kg 0.590 0.861 1.158 1.431 1.731 0.371 0.743 1.115 1.487 1.859 0.464 0.763 1.101 1.393 1.692

−1

D 16.228 43.072 56.910 70.302 83.807 1.240 2.252 3.494 6.272 17.181 0.894 1.255 1.676 2.094 2.674

318 K −1

KE /kg·mol

D

KE /kg·mol

13.815 31.000 35.363 37.095 46.059 1.203 2.174 3.347 5.837 14.384 0.869 1.216 1.614 2.007 2.571

48.41

9.24

1.58

338 K −1

26.61

7.74

1.52

D 12.333 25.667 27.571 29.769 35.363 1.174 2.125 1.758 5.557 13.035 0.847 1.192 1.572 1.963 2.493

KE /kg·mol−1

20.43

7.02

1.47

Cs is the concentration of amine in the organic phase. D is the distribution coefficient.

3. RESULTS AND DISCUSSION Reactive extraction of malic acid and levulinic acid were performed at 298 K, 318 K, and 338 K. The results are presented in Tables 1 and 2 and shown in Figures 1 and 2. The results for 298 K were taken from the literature.8−14 According to the results the distribution coefficients explained by eq 1 (the ratio of concentration of acid in the organic phase to acid concentration in aqueous phase)

(purity > 0.99 wt %), and 3-methyl-1-butanol (purity > 0.99 wt %) were supplied from Merck Co. and Fluka. All chemicals were used without further purification. 2.2. Methods. The extraction experiments have been made in a shaker incubator (GFL) at the controlled temperatures of 298 K, 318 K, and 338 K. Solutions of different initial acid concentrations (0.08 wt %, 0.10 wt %, and 0.15 wt %) were prepared. Equal volumes (20 mL) of aqueous phase and organic phase have been shaken for 3 h at 50 rpm, followed by settling of the mixture for at least 3 h at the same temperature in the shaker. Then the acid concentration in the aqueous phase was determined by titration with 0.1 N NaOH. The relative uncertainty of these determined in the aqueous phase was about 1 %. The deviation of the amount of acid in both phases was 1 %. The solubilities of organic compounds used in this study in the aqueous phase were negligible.

D=

Corg Caq

(1)

decrease with increasing temperature. The higher the concentration of amines, the stronger the decrease of D with increasing temperature. Especially for Amberlite La-2, D values decreased from 68 to 26 for levulinic acid, and for malic acid from 83 to 35 with increasing temperatures from 298 K to 338 K. Such high distribution coefficients as presented in the tables are due to intermolecular hydrogen bonding or ion exchange of 1823



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involving amines, except from Amberlite LA-2. This is an advantage as these extractants, especially TOA and TOMAC, provide a uniform performance in the studied temperature range. The highest KE value has been obtained by using Amberlite LA-2 dissolved in 3-methyl-1-butanol as concentration of 1.731 mol·kg−1. TOMAC in 3-methyl-1-butanol shows a slight decrease in KE values as temperature was varied in the range from 298 K to 338 K. King et al.16 evaluated an organic phase heat of mixing using distribution coefficient values (D) for the extraction of acid using the following equation

d(ln D) = −ΔHtransfer d(1/T )

(6)

In eq 6 ΔHtransfer is the heat of transfer from organic to aqueous phase. If the reaction enthalpy and reaction entropy are assumed to be stable in excess of the temperature range,5 the equilibrium complexation constant is linked to temperature, enthalpy, and entropy by eq 7,

Figure 1. D values of the levulinic acid extraction at different temperatures in the maximum amine concentration dissolved in 3methyl-1-butanol.

−ΔH ΔS + (7) RT R Equation 7 explains that a plot of ln KE vs 1/T gives a straight line. The slope gives the enthalpy of reaction, and the intercept gives the entropy of reaction. The values of ΔH and ΔS were calculated from Figures 3 and 4. For both acids they are ln KE =

Figure 2. D values of the malic acid extraction at different temperatures in the maximum amine concentration dissolved in 3methyl-1-butanol. Figure 3. Plot of ln KE vs 1/T for levulinic acid extraction by different amines. ◆, Amberlite LA-2; ■, TOA; ▲, TOMAC.

the extractant group with the acid. The extraction of levulinic or malic acid (HA) with extractant (E) gives a reaction complex (E:(HA)) which remains mainly in the organic phase.1

presented in Table 3. As can be seen negative values for both thermodynamic functions have been obtained. Negative values

KE1

(HA)aq + Eorg ← → (E: HA)org

(2)

KE2

(HA)aq + (E: HA)org ←→ (E: (HA)2 )org

(3)

KE(n − 1)

(HA)aq + (E: (HA)n − 1)org ←⎯⎯⎯→ (E: (HA)n )org

(4)

The subscripts “aq” and “org” refer to aqueous and organic phases, and n is the number of acid molecules forming complexes with extractant. The equilibrium complexation constant (KE) can be calculated according to eq 5,

KE =

[E: (HA)]org [E]org · [HA]aq

(5)

KE values were calculated for high amine concentrations; see Table 1. Throughout the studied temperature range, only moderate decreases in KE values were found in extractions

Figure 4. Plot of ln KE vs 1/T for malic acid extraction by different amines. ◆, Amberlite LA-2; ■, TOA; ▲, TOMAC. 1824



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Table 3. Thermodynamic Parameters of Reactive Extraction extractants levulinic acid

malic acid

Amberlite LA-2 TOA TOMAC Amberlite LA-2 TOA TOMAC

−1

ΔH/J·mol −4827 −1391 −518 −4343 −1380 −360

−1

ΔS/J·mol ·K −37.7 −4.6 −3.8 −29.1 −0.99 −1.3

−1

Table 5. Effect of Initial Malic Acid Concentration in Different Amine Concentrations Dissolved in 3-Methyl-1butanol at 298 Ka

2

r

0.968 0.982 0.980 0.966 0.983 1

D extractants

of ΔH mean that all reactions carried out by amines in this study are exothermic. The higher the negative value of ΔH, the more exothermic the reaction. The following order has been obtained for the exothermic nature of reactive extraction related both acid (malic and levulinic) using 3-methyl-1-butanol as diluent as:

TOMAC

Similar results were obtained with entropy for all amine extractants used in this study. The entropy of a system is a measure for its randomness. A decrease in entropy indicates an increase of the order of system, for example, due to complex formation.1 By the formation of complexes the number of degrees of freedom decreases as two molecules are combined to form one entity. Effect of initial acid concentration on the reactive extraction was studied in a range from 0.08 wt % to 0.15 wt %. For each extractant extractions of organic acid solutions of varying concentration were performed. As presented in Tables 4 and 5

0.08 wt %

0.10 wt %

0.15 wt %

Amberlite LA-2

0.590 0.861 1.158 1.431 1.731 0.371 0.743 1.115 1.487 1.859 0.464 0.763 1.101 1.393 1.692

11.461 32.155 45.349 57.447 68.017 1.107 1.871 2.871 5.207 11.303 0.757 1.069 1.400 1.778 2.588

10.634 31.142 41.524 50.325 61.125 1.052 1.834 2.810 5.149 11.263 0.743 1.053 1.384 1.762 2.571

9.232 28.264 33.353 42.512 52.462 0.943 1.764 2.713 5.021 11.132 0.711 1.029 1.361 1.745 2.552

TOMAC

0.15 wt %

15.123 41.894 52.256 64.900 76.635 1.174 2.195 3.429 6.207 17.097 0.881 1.242 1.655 2.068 2.646

13.242 39.325 45.326 57.476 68.841 1.068 2.081 3.305 6.103 16.868 0.851 1.210 1.618 2.023 2.612

4. CONCLUSION The effect of thermodynamic and initial acid concentration on the extraction of levulinic acid and malic acid by different amines was studied. The extraction enthalpy and entropy were calculated as negative values for each amine + 3-methyl-1butanol sytem. This extraction showed that the reaction processes of these acid extractions with these amines are exothermic. The systems went to a more ordered process after extraction with negative entropy. Decreases of initial acid concentration effected a negative extraction efficiency for both acids.

D Cs/mol·kg−1

0.10 wt %

16.228 43.072 56.910 70.302 83.807 1.240 2.252 3.494 6.272 17.181 0.894 1.255 1.676 2.094 2.674

a Cs is the concentration of amine in the organic phase. D is the distribution coefficient.

Table 4. Effect of Initial Levulinic Acid Concentration in Different Amine Concentrations Dissolved in 3-Methyl-1butanol at 298 Ka extractants

0.08 wt %

0.590 0.861 1.158 1.431 1.731 0.371 0.743 1.115 1.487 1.859 0.464 0.763 1.101 1.393 1.692

TOA

Amberlite LA‐2 > TOA > TOMAC

TOA

Cs/mol·kg

Amberlite LA-2

−1

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■

REFERENCES

(1) Keshav, A.; Wasewar, K. L.; Chand, S.; Uslu, H.; Iṅ ci, I.̇ Thermodynamics of reactive extraction of propionic acid. i-Manager J. Fut. Eng. Technol. 2008−2009, 4, 42−50. (2) Baniel, A. M.; Blumberg, R.; Hajdu, K. Recovery of acids from aqueous solutions. U.S. Patent 4275234, 1982. (3) Baniel, A. M.; Blumberg, R.; Hajdu, K. Recovery of acids from aqueous solutions. British Patent 1426018, 1973. (4) Wennersten, R. The extraction of citric acid from fermentation broth using a solution of a tertiary amine. J. Chem. Technol. Biotechnol. 1983, 33, 85−94. (5) Tamada, J. A.; King, C. J. Extraction of carboxylic acids with amine extractants. 3. Effect of temperature, water coextraction, and process considerations. Ind. Eng. Chem. Res. 1990, 29, 1327−1333. (6) Harrington, T.; Hossain, M. M. Extraction of lactic acid into sunflower oil and its recovery into an aqueous solution. Desalination 2008, 218, 287−296. (7) Keshav, A.; Wasewar, K. L.; Chand, S. Extraction of acrylic, propionic and butyric acid using Aliquat 336 in oleyl alcohol: equilibria and effect of temperature. Ind. Eng. Chem. Res. 2009, 48, 888−893.

a Cs is the concentration of amine in the organic phase. D is the distribution coefficient.

the distribution coefficients (D) with all solvent loading organic phases decreased with increasing initial concentration of acids at 298 K. Especially, D decreased from 68 to 52 with increasing initial acid concentration from 0.08 wt % to 0.15 wt % at 1.731 mol·kg−1 of Amberlite LA-2. At all concentrations of TOA and TOMAC a significant increase in distribution coefficients was not observed. 1825



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(8) Uslu, H.; Kirbaslar, Ş. I.̇ Solvent effects on the extraction of malic acid from aqueous solution by secondary amine extractant. Sep. Purif. Technol. 2010, 71, 22−29. (9) Uslu, H.; Kirbaslar, Ş. I.̇ Extraction of aqueous of malic acid by trioctylamine extractant in various diluents. Fluid Phase Equilib. 2010, 287, 134−140. (10) Uslu, H.; Kirbaslar, Ş. I.̇ Purification of L-Malic Acid from Aqueous Solution by a Method of Reactive Extraction. J. Chem. Eng. Data 2009, 54, 2819−2826. (11) Uslu, H.; Kirbaslar, Ş. I.̇ Investigation of phase equilibria of levulinic acid distribution between aqueous phase to organic phase by Aliquat 336 in different modifiers. J. Chem. Thermodyn. 2009, 41, 1042−1048. (12) Uslu, H.; Kirbaslar, Ş. I.̇ ; Wasewar, K. L. Reactive Extraction of Levulinic Acid by Amberlite LA-2 Extractant. J. Chem. Eng. Data 2009, 54, 712−718. (13) Uslu, H.; Kirbaslar, Ş. I.̇ Equilibrium studies of extraction of levulinic acid by (trioctylamine (TOA) plus ester) solvents. J. Chem. Eng. Data 2008, 53, 1557−1563. (14) Uslu, H.; Kirbaslar, Ş. I.̇ Investigation of levulinic acid distribution from aqueous phase to organic phase with TOA extractant. Ind. Eng. Chem. Res. 2008, 47, 4598−4606. (15) Uslu, H. Reactive extraction of levulinic acid using TPA in toluene solution: LSER modeling, kinetic and equilibrium studies. Sep. Sci. Technol. 2008, 43, 1535−1548. (16) King, C. J.; Tamada, J. A.; Kertes, A. S. Extraction of carboxylic acids with amine extractants. (1) Equilibria and law of mass action modeling. Ind. Eng. Chem. Res.. 1990, 29, 1319−1326.

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Effect of Temperature and Initial Acid Concentration on the Reactive

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