Reactive Extraction of Oxoethanoic Acid (Glyoxylic Acid) Using

Jul 18, 2014 - ... Faculty, Chemical Engineering Department, Ayazağa, İstanbul 34433, Turkey ... Copyright © 2014 American Chemical Society ... K11...
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Reactive Extraction of Oxoethanoic Acid (Glyoxylic Acid) Using Amberlite-LA2 in Different Diluents Hasan Uslu,*,† Dipaloy Datta,‡ and Sushil Kumar§ Beykent University, Engineering and Architecture Faculty, Chemical Engineering Department, Ayazağa, Iṡ tanbul 34433, Turkey Department of Chemical Engineering, Thapar University, Patiala, Punjab 147004, India § Department of Chemical Engineering, Motilal Nehru National Institute of Technology (MNNIT), Allahabad, Uttar Pradesh 211004, India † ‡

ABSTRACT: An equilibrium distribution study of oxoethanoic acid (also known as glyoxylic acid, 0.93 kmol·m−3) between water and Amberlite-LA2 (0.24 to 1.67 kmol·m−3) is carried out at constant temperature, 298 ± 0.5 K. The extract phase is prepared using Amberlite-LA2 as extractant, and hexane, kerosene, methylbenzene (toluene), butane-2-one (methyl ethyl ketone, MEK), 2,6 dimethyl-4-heptanone (diisobutylketone, DIBK), hexane-2-one, and decane1-ol as diluents. The equilibrium data are presented by calculating parameters like loading factor, Z, extraction efficiency, %E, and distribution coefficients, KD. The highest value of KD is found to be 92 at higher concentration (1.67 kmol·m−3) of Amberlite-LA2 in hexane-2-one. The extraction ability of Amberlite-LA2 in different diluents in terms of KD and % E is found to be in the order of hexane-2one > methylbenzene > hexane > kerosene > DIBK > MEK > decane-1-ol. The values of stoichiometric coefficient (m) and equilibrium complexation constants (KE, K11, K21, and K12) are determined from the mass action law and using experimental data. From the values of m, it is proposed that the interaction between acid and amine molecule is mostly by 1:1 type but the values of m less than 1 indicate possible formation of 1:2 type complex and diluents also extract some acid molecule by physical extraction. The values of m greater than 1 point out the formation of little amount of 2:1 type complex in the organic phase.

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INTRODUCTION The production of carboxylic acids from renewable sources using biochemical synthesis route (fermentation technology) is considered to be an attractive alternative. This method is comparatively a clean and green technology and produces acids at very low acid concentration. Recovery of these acids can be obtained by separation enhanced by reaction, that is, reactive extraction. The reactive extraction studies of carboxylic acids were carried out by various investigators. They suggested that carboxylic acids are better extracted by using higher molecular weight, tertiary and quaternary amines such as N,N-dioctyloctan1-amine (TOA), trioctyl methylammonium chloride (Aliquat 336), Alamine 336 (trioctyl/decyl amine), Amberlite LA-2, and so forth when dilute aqueous solution is present.1−13 Generally, in the reactive extraction the interaction between the acid molecule and extractant molecule is strong and forms acidextractant complexes giving high distribution of acid at equilibrium. Additionally, the higher affinity of the extractant, selectivity recovers acid from a mixture of other nonacidic components. Reversible nature of the reaction enables easy recovery of the acid and recycling of the solvent.2,3,8 Debus,14 in a review on the history of oxoethanoic acid, mentioned that he had discovered the acid in 1856 as one of the products of the oxidation of ethyl alcohol by nitric acid at common temperatures. It is the simplest aldehydic acid. In commercial 50% aqueous solutions, this acid is predominantly © 2014 American Chemical Society

found in nonvolatile hydrated and oligomeric forms. Generally, because of its bifunctionality, it is a versatile reagent in organic and fine chemicals synthesis. Oxoethanoic acid is used as a key intermediate in the pharmaceutical or agro industries. The acid is used to manufacture synthetic vanillin and ethyl vanillin which are used in the synthesis of antibiotic, amoxicillin, and as a starting material for the synthesis of iron chelates, a product group used as micronutrient in the agro industry. The nature of acid, compositions of acid and amine, and polarity of diluent are found to influence the equilibrium characteristics of amine extraction of carboxylic acids from aqueous solutions.9 Process considerations dealing with the competition between physical extraction and chemical interaction of highly hydrophobic acids still remain a challenging problem because such systems show extremely nonideal behavior.15 The present work is focused to intensify the recovery of oxoethanoic acid by using reactive extraction with AmerliteLA2 in a variety of diluents such as alkane (hexane), aromatic (kerosene and methylbenzene), ketone [butane-2-one (methyl ethyl ketone, MEK), 2,6 dimethyl-4-heptanone (diisobutylketone, DIBK), hexane-2-one], and alcohol (decane-1-ol). Received: May 6, 2014 Accepted: July 11, 2014 Published: July 18, 2014 2623

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where C̅ 0R2N is the initial extraction concentration in the organic phase. Theoretical Section. The mechanism of reactive extraction process may be proposed based on the following assumptions: (i) negligible physical extraction of acid by diluent compared to extractant, (ii) poor solubility of extractant and diluents in water, (iii) solute (oxoethanoic acid) carries less amount of water in the organic phase,2 and (iv) negligible change in the volume of each phase at equilibrium. The extraction of oxoethanoic acid (undissociated acid part, HA) with amine (R2N) is an interfacial reaction described by the following equation.

EXPERIMENTAL SECTION Reagents. Amberlite LA-2 (n-lauryltrialkyl-methyl amine, Merck, purity >0.99 wt) is a yellow liquid and an ion exchange extractant with a molecular weight of 353.67 having 24 to 28 carbon atoms. Oxoethanoic acid (Sigma-Aldrich, purity >0.98 wt) is an α-keto acid and has a ketone group on the carbon atom next to the acid group. Hexane, kerosene, methylbenzene, butane-2-one (methyl ethyl ketone, MEK), 2,6 dimethyl-4heptanone (diisobutylketone, DIBK), hexane-2-one, and decane-1-ol were procured from Merck and Fluka to dilute Amberlite LA-2 and to prepare organic solution. Purities of all chemicals used in this study were upper 98% in mass and were used without further purification. Procedure. A total of 0.93 kmol·m−3 of aqueous solution of oxoethanoic acid (8% in mass) was prepared as an initial concentration using distilled water. Seven different concentrations of Amberlite-LA2 (0.24 to 1.67 kmol·m−3) were considered to prepare the extract phase and by dissolving it in seven different diluents (hexane, kerosene, methylbenzene, butane-2-one, 2,6 dimethyl-4-heptanone, hexane-2-one, and decane-1-ol) to perform experiments on the equilibrium reactive extraction. Equal volumes (20 mL) of aqueous and organic phases were mixed in Erlenmeyer flaks (100 mL) for 6 h in a shaker at 298 ± 0.5 K and 40 rpm speed, followed by settling of mixtures for at least 2 h at the same temperature in digital controlled incubator. Preliminary tests showed that the 6 h is the sufficient time to achieve equilibrium. The pH of the aqueous phase was measured by a Metler Toledo pH meter. Acid concentration in the aqueous phase after the extraction was determined by using sodium hydroxide (0.1 N), which was standardized with 0.1 N HCl as titrant and 3,3-bis(4hydroxyphenyl)isobenzofuran-1(3H)-one or phenolphthalein as an indicator for titration. The relative uncertainty in the titration method was found to be not exceeding ±3%. The extracted acid concentration in the organic phase was calculated considering complete mass balance. The batch equilibrium results, that is, the measured values of aqueous and organic phase concentrations, are used to calculate distribution coefficient (KD), degree of extraction (%E), and loading ratio (Z) and given by eqs 1, 2, and 3, respectively. Distribution coefficient (KD) of oxoethanoic acid (HA) by Amberlite-LA2 (R2N) can be defined by a ratio of the total concentration of acid in the organic phase (C̅ HA) to the aqueous phase (CHA) at equilibrium. C̅ KD = HA CHA

KE

mHA + R 2N ↔ (HA)m (R 2N)

With an expression of equilibrium constant as follows KE =

KD × 100 1 + KD

KD =

C̅ HA C̅ R0 2N

[HA]m C̅ R 2N

(5)

Cm̅ C̅ HA =m 1 CHA CHA

(6)

Oxoethanoic acid dissociates at equilibrium in the aqueous phase and the reaction is written as eq 7 HA ↔ H+ + A−

(7)

The dissociation constant (Ka) is given by eq 8 Ka =

[H+][A−] [HA]

(8)

Therefore, the total oxoethanoic acid concentration in the aqueous phase, CHA can be expressed in terms of undissociated acid concentration ([HA]), Ka, and proton concentration ([H+]). CHA = [HA] + C A−

⎛ Ka ⎞ CHA = [HA]⎜1 + ⎟ ⎝ [H+] ⎠

(9)

(10)

Substituting the values of C̅ m1 and [HA] from eqs 5 and 10, respectively, in eq 6, eq 11 is derived

(1)

KD =

mKEC̅ R 2NCmHA− 1

(1 +

Ka [H+]

m

)

(11)

The free extractant concentration, C̅ R2N in the organic phase at equilibrium is represented as

(2)

C̅ R 2N = C̅ R0 2N − C̅ m1

The extent of organic phase loading by the extractant and diluent with acid is expressed by the loading ratio, Z (a ratio of total acid concentration in the organic phase at equilibrium to the total initial extractant concentration in the extract phase). The loading ratio, Z can be expressed in the following form Z=

C̅ m1

The expression for the distribution coefficient, as shown in eq 1, can be represented as

The degree of extraction (% E) is defined at equilibrium as follows

E=

(4)

(12)

or C̅ R 2N = C̅ R0 2N −

KDCHA m

(13)

The value of C̅ R2N from eq 13 is substituted in eq 11, which results in eq 14

(3) 2624

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Table 1. Extraction Data of Oxoethanoic Acid from Aqueous Solution Using Amberlite LA-2 in Different Solvents at Temperature T = 298 K C̅ R0 2N

diluents

kmol·m hexane-2-one

0.24 0.47 0.71 0.94 1.18 1.41 1.67 0.24 0.47 0.71 0.94 1.18 1.41 1.67 0.24 0.47 0.71 0.94 1.18 1.41 1.67 0.24 0.47 0.71 0.94 1.18 1.41 1.67 0.24 0.47 0.71 0.94 1.18 1.41 1.67 0.24 0.47 0.71 0.94 1.18 1.41 1.67 0.24 0.47 0.71 0.94 1.18 1.41 1.67

methylbenzene

hexane

kerosene

DIBK

MEK

decane-1-ol

KD =

CHA −3

kmol·m 0.48 0.35 0.29 0.22 0.10 0.02 0.01 0.60 0.47 0.33 0.22 0.14 0.05 0.04 0.74 0.57 0.50 0.31 0.21 0.07 0.05 0.35 0.27 0.22 0.20 0.14 0.08 0.06 0.56 0.43 0.31 0.22 0.12 0.09 0.07 0.87 0.72 0.57 0.46 0.36 0.20 0.16 0.89 0.77 0.62 0.49 0.37 0.24 0.21

KD,exp

C̅ HA −3

kmol·m

−3

0.45 0.57 0.64 0.71 0.83 0.90 0.92 0.33 0.45 0.6 0.71 0.79 0.88 0.89 0.19 0.36 0.43 0.61 0.72 0.86 0.88 0.58 0.66 0.71 0.73 0.78 0.84 0.87 0.36 0.49 0.62 0.70 0.81 0.84 0.86 0.06 0.20 0.36 0.47 0.56 0.73 0.77 0.04 0.16 0.31 0.44 0.56 0.69 0.72

0.938 1.629 2.207 3.227 8.300 45.000 92.000 0.550 0.957 1.818 3.227 5.643 17.600 22.250 0.257 0.632 0.860 1.968 3.429 12.286 17.600 1.657 2.444 3.227 3.650 5.571 10.500 14.500 0.643 1.140 2.000 3.182 6.750 9.333 12.286 0.069 0.278 0.632 1.022 1.556 3.650 4.813 0.045 0.208 0.500 0.898 1.514 2.875 3.429

mKEC̅ R0 2NC HA m − 1

(1 +

Ka [H+]

m

)

+ mKEC HA m

KD,pred

E

eq 14

%

0.384 1.027 1.866 3.237 8.707 44.916 92.020 0.338 0.836 1.758 3.368 6.278 16.625 22.793 0.242 0.609 1.042 2.157 3.861 11.695 17.871 0.612 1.494 2.664 3.800 6.206 10.525 14.397 0.408 1.009 2.009 3.482 6.605 9.258 12.356 0.146 0.343 0.646 1.048 1.656 3.404 4.934 0.134 0.301 0.558 0.921 1.502 2.667 3.564

48.40 61.96 68.82 76.34 89.25 97.83 98.92 35.48 48.90 64.51 76.34 84.95 94.62 95.70 20.45 38.73 46.24 66.31 77.42 92.47 94.62 62.36 70.96 76.34 78.49 84.78 91.30 93.55 39.14 53.27 66.67 76.09 87.10 90.32 92.47 6.45 21.75 38.73 50.54 60.88 78.49 82.80 4.31 17.22 33.33 47.31 60.22 74.19 77.42

Z

pHeq

1.875 1.213 0.901 0.755 0.703 0.638 0.551 1.375 0.957 0.845 0.755 0.669 0.624 0.533 0.792 0.766 0.606 0.649 0.610 0.610 0.527 2.417 1.404 1.000 0.777 0.661 0.596 0.521 1.500 1.043 0.873 0.745 0.686 0.596 0.515 0.250 0.426 0.507 0.500 0.475 0.518 0.461 0.167 0.34 0.437 0.468 0.475 0.489 0.431

2.04 2.11 2.15 2.21 2.38 2.75 2.92 1.99 2.04 2.12 2.21 2.31 2.54 2.59 1.94 2.00 2.03 2.13 2.22 2.46 2.54 2.11 2.16 2.21 2.23 2.31 2.43 2.50 2.00 2.06 2.13 2.21 2.34 2.41 2.46 1.91 1.95 2.00 2.05 2.10 2.23 2.28 1.90 1.93 1.98 2.03 2.09 2.19 2.22

mean-square deviation, rmsd) to minimize the error between the experimental and predicted values of KD, eq 15 (14) N

rmsd =

To estimate the values of equilibrium constant (KE) and stoichiometric coefficient (m) of the reactive extraction of

∑1 (KD,exp − KD,pred)2 N−1

(15)

where N is the number of data points.

oxoethanoic acid, an error function is defined (know as root2625

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Based on the predicted values of m per extractant molecule, the formation of different types of complexes like 1:1, 2:1, and 1:2 between acid and amine are considered. The stoichiometric equations are represented by the following eqs 16 to 18. K11

HA + R 2N ↔ (HA)(R 2N) K 21

2HA + R 2N ← → (HA)2 (R 2N) K12

HA + 2R 2N ← → (HA)(R 2N)2

solvents from different categories such as hexane, kerosene, methylbenzene, butane-2-one, 2,6 dimethyl-4-heptanone, hexane-2-one, and decane-1-ol to analyze the effect of solvent polarity on the distribution of acid between water (aqueous phase) and extractant-diluent (organic phase). The results of reactive extraction of oxoethanoic acid with Amberlite-LA2 with the calculated values of distribution coefficient (KD), degrees of extraction (%E), and loading ratio (Z) are shown in Table 1. The concentrations of Amberlite-LA2 in different diluents are changed between 0.24 and 1.67 kmol· m−3 to investigate the effect of organic phase composition on the distribution coefficient. Initial concentration of oxoethanoic acid in the aqueous phase is kept constant 0.93 kmol·m−3. It is observed that the extraction ability of (Amberlite-LA2 + solvents) mixtures changes with an increase in the initial amine concentration in the extract phase. In the reactive extraction of oxoethanoic acid by Amberlite-LA2, the total amine concentration does not affect the loading incase of acid−amine complex with only one extractant molecule. If there are more amine molecule per complex, then there is an increase in the amount of loading by acid. 16 Generally, with an increase in the concentration of amine in the organic phase the extraction efficiency is found to increase and reaches a constant value.17,18 The values of the distribution coefficient, KD (degree of extraction, %E) are found to vary in the range of 0.938 to 92 (48.40% to 98.92%) for hexane-2-one, 0.55 to 22.25 (35.48% to 95.70%) for methylbenzene, 0.257 to 17.6 (20.45% to 94.62%) for hexane, 1.657 to 14.5 (62.36% to 93.55%) for kerosene, 0.643 to 12.286 (39.14% to 92.47%) for DIBK, 0.069 to 4.813 (6.45% to 82.80%) for MEK, and 0.045 to 3.429 (4.31% to 77.42%) for decane-1-ol with the increase in the concentration of amine (0.24 to 1.67 kmol·m−3) at fixed acid concentration of 0.93 kmol·m−3 (Figure 1). The diluents’ power of extraction with amine extractant, shown in terms of maximum distribution coefficient (KD,max), is found to be in the order of hexan-2-one (KD,max = 92) > methylbenzene (KD,max = 22.25) > hexane (KD,max = 17.6) > kerosene (KD,max = 14.5) > DIBK (KD,max = 12.286) > MEK

(16) (17) (18)

The corresponding equilibrium constants (K11, K21, and K12) are written in the following form (eqs 19 to 21) K11 =

C̅ 11 [HA]C̅ R 2N

(19)

K 21 =

C̅ 21 [HA]2 C̅ R 2N

(20)

C̅ 12 [HA]C̅ 2R 2N

(21)

K12 =

C̅ 11, C̅ 21, and C̅ 12 are the concentrations of the complexes 1:1, 2:1, and 1:2 formed in the organic phase at equilibrium, respectively. The acid concentration and free extractant concentration in the organic phase are represented by eqs 22 and 23, respectively C̅ HA = C̅ 11 + 2C̅ 21 + C̅ 12 = K11[HA]C̅ R 2N + 2K 21[HA]2 C̅ R 2N + K12[HA]C̅ 2R 2N (22)

C̅ R 2N = C̅ 0R 2N − (C̅ 11 + C̅ 21 + 2C̅ 12) = C̅ 0R 2N − (K11[HA]C̅ R 2N + K 21[HA]2 C̅ R 2N + 2K12[HA]C̅ 2R 2N)

(23)

The eq 23 is used to determine the value of C̅ R2N and written in the following form 2K12[HA]C̅ 2R 2N + (1 + K11[HA] + K 21[HA]2 )C̅ R 2N − C̅ 0R 2N = 0

(24)

This value of C̅ R2N is substituted in eq 22 and the total acid concentration in the organic phase is calculated. The values of the individual equilibrium constants (K11, K21, and K12) are estimated based on the total acid concentration in the aqueous phase at equilibrium, and minimizing the error between the experimental and predicted values of organic phase acid concentration at equilibrium, C̅ HA N

rmsd =

∑1 (C̅ HA,exp − C̅ HA,pred)2 N−1

(25)

where N is the number of data points.

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RESULTS AND DISCUSSION Amberlite-LA2 is chosen as an extractant in the concentration range of 0.24 to 1.67 kmol·m−3 to conduct the equilibrium extraction experiments of oxoethanoic acid (0.93 kmol·m−3) from aqueous solution. The organic phase is diluted using

Figure 1. Degree of extraction (%E) for the reactive extraction of oxoethanoic acid (0.93 kmol·m−3) with Amberlite-LA2 (0.24 to 1.67 kmol·m−3) dissolved in different diluents at temperature T = 298 K. Symbols: +, hexane-2-one; Δ, methylbenzene; ●, hexane; ○, kerosene; *, DIBK; ■, MEK; □, decane-1-ol. 2626

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(KD,max = 4.813) > decane-1-ol (KD,max = 3.429). These maximum values are observed at 1.67 kmol·m−3 of Amberlite-LA2 concentration. Figure 2 represents the comparison of the

Table 2. Values of Number of Acid Molecules Reacting with Amine m, Equilibrium Constants KE, and rmsd in Different Diluents at Temperature T = 298 K diluents

m

KE

rmsd

hexane-2-one methylbenzene hexane kerosene DIBK MEK decane-1-ol

0.78 0.89 0.79 1.03 1.05 0.57 0.54

112.39 32.18 25.22 20.94 18.15 14.58 11.32

0.3996 0.5372 0.3363 0.6768 0.1800 0.1268 0.1171

accordance with the observed values of distribution coefficient. The values of KD are predicted using model eq 14 for the extraction of oxoethanoic acid with Amberlite-LA2 in different diluents and presented in Table 1. The model prediction shows a good match with the experimental values having maximum rmsd = 0.6768. The predicted values of KD using model eq 14 for the extraction of oxoethanoic acid with Amberlite-LA2 in different diluents are calculated and compared with the experimentally determined values of KD (Figure 3). Figure 2. Maximum distribution coefficients of oxoethanoic acid (0.93 kmol·m−3) at 1.67 kmol·m−3 of Amberlite-LA2 dissolved in different diluents at temperature T = 298 K.

maximum values of distribution coefficient of different diluents with Amberlite-LA2 (1.67 kmol·m−3) at constant concentration of oxoethanoic acid (0.93 kmol·m−3). The dissociation of carboxylic acid molecules takes place at higher pH values and it is reported that extraction is more favorable at lower pH of the aqueous solution. Also, the ratio of dissociated to undissociated molecules increases with increase in the value of pH. Therefore, pH is one of the most important and effective parameter for the stability of the acid molecule and formation of dissociated acid in the aqueous phase. In the present study, the values of pH using Amberlite-LA2 with all diluents are found between 1.91 and 2.92, which are less than the value of pKa (= 3.32)19 of acid at 298 K. In the extraction of the undissociated molecules of oxoethanoic acid by using Amberlite-LA2, the values of loading ratios are observed in the range of 0.527 to 0.792 for hexane, 0.521 to 2.417 for kerosene, 0.533 to 1.375 for methylbenzene, 0.25 to 0.461 for MEK, 0.515 to 1.5 for DIBK, 0.551 to 1.875 for hexane-2-one, and 0.167 to 0.431 for decane-1ol. The values of Z indicate that the amine extractant is overloaded with acid using diluents like hexane, kerosene, methylbenzene, DIBK, and hexane-2-one. The overloading is not observed with MEK and decane-1-ol. Hence, there is a possible formation of complexes like 1:1, 1:2, 2:1, and so forth in the organic phase. The values of number of reacting acid molecule/s (m) per extractant molecule, and the equilibrium constants (KE) are estimated by minimizing the error between experimental and predicted values of KD using eq 14 and presented in Table 2. The estimated values of m less than one for hexane (0.79), methylbenzene (0.89), MEK (0.57), decane-1-ol (0.54), and hexane-2-one (0.78) confirm the formation of 1:1 and 1:2 acid− amine complexes in the organic phase. The m values greater than one for kerosene (1.03) and DIBK (1.05) suggest that the amine extract the acid by making both types of 1:1 and 2:1 complexes. The apparent value of KE is found to be highest for hexane-2-one (KE = 112.39) > methylbenzene (KE = 32.18) > hexane (KE = 25.22) > kerosene (KE = 20.94) > DIBK (KE = 18.15) > MEK (KE = 14.58) > decane-1-ol (KE = 11.32). The trend is

Figure 3. Model predicted (eq 14) versus experimental values of distribution coefficient of oxoethanoic acid (0.93 kmol·m−3) with Amberlite-LA2 (0.24 to 1.67 kmol·m−3) dissolved in different diluents at temperature T = 298 K. Symbols: +, heptane-2-one; Δ, methylbenzene; ●, hexane; ○, kerosene; *, DIBK; ■, MEK; □, decane-1-ol.

On the basis of calculated values of m, that is, number of reacting acid molecule per extractant molecule, the corresponding equilibrium constants (K11, K21, and K12) for the formation of 1:1, 2:1, and 1:2 acid−amine complexes in the organic phase are determined (Table 3) using eq 25. The values of K11, K21, and K12 are estimated based on the total amount of acid transferred in the organic phase at equilibrium and minimizing the error between the experimental and predicted values of organic phase acid concentration at equilibrium, C̅ HA. The formation of different types of acid−amine complexes generally depend on the nature of diluent used which controls the basicity of the amine and stabilizes the ion pair formed in the extract phase. The diluents such as hexane-2-one, methylbenzene, hexane, MEK, and decane-1-ol form mainly 1:1 and 2:1 acid−amine complex in the organic phase. The acid molecule interacts with amine 2627

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Table 3. Values of Individual Equilibrium Constants (K11, K21, and K12) for the Reactive Extraction of Oxoethanoic Acid by Amberlite-LA2 Dissolved in Different Diluents at Temperature T = 298 K diluents

K11

hexane-2-one methylbenzene hexane kerosene DIBK MEK decane-1-ol

222.42 45.96 56.59 57.38 16.65 9.37 5.60

K21

K12

rmsd

185.53 40.71 38.25

0.1251 0.0612 0.0421 0.1259 0.0746 0.0696 0.0748

259.63 60.06 5.12 2.96

molecule by forming 1:1 and 1:2 solvates in the extract phase in the presence of kerosene and DIBK. In these diluents, the formation of 1:2 (K12 = 259.63 kmol−2·m6 for kerosene; K12 = 60.06 kmol−2·m6 for DIBK) solvates is much more prominent that 1:1 type of solvates (K11 = 57.38 kmol−1·m3 for kerosene; K11 = 16.65 kmol−1·m3 for DIBK). In case of hexane-2-one, the formation of 1:1 complex is much stronger than other diluents with K11 equal to 222.42 kmol−1·m3. Therefore, the diluents, hexane-2-one, methylbenzene, hexane, MEK and decane-1-ol favor the extraction process by forming mostly 1:1 and 1:2 acid− amine complex, and kerosene and DIBK by 1:1 and 2:1 complexes in the organic phase. The concentrations of acid−amine complexes and free amine in the organic phase at equilibrium are also determined using eqs 19, 20, 21, and 23 for C̅ 11, C̅ 21, C̅ 12, and C̅ R2N, respectively. The concentration profiles are drawn in Figures 4a, b, and c and 5, respectively. It is observed from Figure 4a, b, and c that the formation of C̅ 11 is almost linear with amine concentration up to 1.18 kmol·m−3 for all the diluents. The nonlinearity is observed after this concentration for heptane-2-one, methylbenzene, hexane, MEK, and decane-1-ol. This is due to the formation of 1:2 type complexes and consumption of more amine molecule per acid molecule in the organic phase. In case of kerosene and DIBK, a slightly nonlinear trend is seen but which is increasing in nature. The formation of 2:1 acid−amine complexes may be the reason for this behavior as no extra amine is used up by the acid. Figure 5 shows the trend of amine consumed (i.e., free amine) by the acid molecule in the respective diluents. At lower amine concentration (up to 1.18 kmol·m−3), almost all the amine molecules (>90% for all diluents and >95% for hexane-2-one) take part in the extraction process, but at the higher side, 30% amine is left unused by the acid molecules. At higher AmberliteLA2 concentration, diluent may become more active and extract acid molecule by physical extraction.

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CONCLUSIONS The extractability study of Amberlite-LA2 using diluents from different categories [alkane (hexane), aromatic (kerosene and methylbenzene), ketone [butane-2-one (methyl ethyl ketone, MEK), 2,6 dimethyl-4-heptanone (diisobutylketone, DIBK), hexane-2-one], and alcohol (decane-1-ol)] for the reactive extraction of oxoethanoic acid has been investigated. Distribution coefficients, loading factors, and extraction efficiency are calculated using the equilibrium experimental results. The extraction equilibrium is interpreted as a result of simultaneous formation of 1:1, 2:1, and 1:2 acid−amine complexes. Equilibrium extraction constants, KE, are calculated for each diluent. The highest synergistic extraction efficiency is found

Figure 4. Concentration profiles of acid−amine complex formation (a) C̅ 11, (b) C̅ 21, and (c)C̅ 12 at equilibrium of oxoethanoic acid (0.93 kmol· m−3) with Amberlite-LA2 (0.24 to 1.67 kmol·m−3) dissolved in different diluents at temperature T = 298 K. Symbols: +, heptane-2-one; Δ, methylbenzene; ●, hexane; ○, kerosene; *, DIBK; ■, MEK; □, decane1-ol. 2628

dx.doi.org/10.1021/je5003972 | J. Chem. Eng. Data 2014, 59, 2623−2629

Journal of Chemical & Engineering Data

Article

(10) Uslu, H.; Inci, I. (Liquid + Liquid) Equilibria of the (Water + Propionic Acid + Aliquat 336 + Organic Solvents) at T 298.15. J. Chem. Thermodyn. 2007, 39, 804−809. (11) Uslu, H.; Bayat, C.; Gokmen, S.; Yorulmaz, Y. Reactive Extraction of Formic Acid by Amberlite LA-2 Extractant. J. Chem. Eng. Data 2009, 54, 48−53. (12) Vogel, H.; Starr, J. N.; King, C. J. Extraction of Carboxylic Acids from Aqueous Solutions with the Extractant System Alcohol/Tri-nAlkylamines. Chem. Eng. Technol. 2000, 23, 70−74. (13) Datta, D.; Kumar, S. Intensification of Recovery of Formic Acid from Aqueous Stream Using Reactive Extraction with N,N-Dioctyloctan-1-Amine: Effect of Diluent and Temperature. Chem. Eng. Commun. 2013, 200, 678−700. (14) Debus, H. CXLI. - Contributions to the History of Glyoxylic Acid. J. Chem. Soc., Trans. 1904, 85, 1382−1403. (15) Senol, A. Extraction Equilibria of Valeric Acid Using (Alamine 336/Diluent) and Conventional Solvent Systems. Modeling Considerations. Chem. Eng. Proces. 2002, 41, 681−692. (16) Inci, I. Distribution of Glycolic Acid between Water and Different Organic Solutions. Chem. Biochem. Eng. Q. 2002, 16, 81−85. (17) Qin, W.; Zhang, Y.; Li, Z.; Dai, Y. Extraction Equilibria of Glycolic and Glyoxylic Acids with Trialkylphosphine Oxide and Trioctylamine as Extractant. J. Chem. Eng. Data 2003, 48, 430−434. (18) Asci, Y. S.; Inci, I. Extraction of Glycolic Acid from Aqueous Solutions by Amberlite LA-2 in Different Diluent Solvents. J. Chem. Eng. Data 2009, 54, 2791−2794. (19) Dawson, R. M. C. Data for Biochemical Research; Clarendon Press: Oxford, 1959.

Figure 5. Concentration profiles of free amine concentration (C̅ R2N) at equilibrium of oxoethanoic acid (0.93 kmol·m−3) with Amberlite-LA2 (0.24 to 1.67 kmol·m−3) dissolved in different diluents at temperature T = 298 K. Symbols: +, heptane-2-one; Δ, methylbenzene; ●, hexane; ○, kerosene; *, DIBK; ■, MEK; □, decane-1-ol.

with Amberlite-LA2 + hexane-2-one, extractant-diluent system with value of KD and KE of 92 and 112.39, respectively.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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REFERENCES

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dx.doi.org/10.1021/je5003972 | J. Chem. Eng. Data 2014, 59, 2623−2629