Equilibrium Study on the Extraction of Levulinic Acid from Aqueous

Article pubs.acs.org/jced

Equilibrium Study on the Extraction of Levulinic Acid from Aqueous Solution with Aliquat 336 Dissolved in Different Diluents: Solvent’s Polarity Effect and Column Design Dipaloy Datta,† Mustafa Esen Marti,‡ Dharm Pal,§ and Sushil Kumar*,∥ †

Department Department § Department ∥ Department ‡

of of of of

Chemical Chemical Chemical Chemical

Engineering, Engineering, Engineering, Engineering,

Malaviya National Institute of Technology, Jaipur, Rajasthan, India Selçuk University, Konya, Turkey National Institute of Technology, Raipur, Chhattisgarh, India Motilal Nehru National Institute of Technology, Allahabad, Uttar Pradesh, India

ABSTRACT: In the present study, the reactive extraction of levulinic acid (4-oxopentanoic acid) was investigated by using Aliquat 336 in various organic solvents [benzene, dichloromethane (DCM), dodecane, methyl isobutyl ketone (MIBK), 1-octanol] from dilute aqueous solution. Equilibrium data obtained at 298 K and 101.325 kPa were used to determine the values of distribution coefficient (KD), degree of extraction (E%), loading factor (Z), and complexation constants (KE). Among the diluents tested, DCM gave the highest extraction efficiency. Using 0.5454 mol·kg−1 of Aliquat 336 in DCM, KD and E% were obtained as 2.082 and 67.55%, respectively, at 0.2795 mol·kg−1 initial acid concentration in the aqueous solution. Z values were found to be between 0.033 and 1.628 depending on the nature of the diluent used and Aliquat 336 concentration in the organic phase. Using mass action law modeling, the stoichiometry of the extraction reaction was determined. It was observed that mostly 1:1, 2:1, and 3:1 types of complexes were formed. The results inferred that the polarity and the molecular size of the solvent were the important critical factors which decide the solubilization of the solvates in the organic phase. DCM was found to be the most appropriate solvent among tested ones for the reactive extraction of levulinic acid. The feasibility of the extraction process was also assessed by calculating the minimum solvent (extractant + diluent) to feed ratio and the number of theoretical stages required for the recovery of levulinic acid in the extraction column.

1. INTRODUCTION Levulinic acid is a monocarboxylic acid with a ketone group, used in the manufacture of several pharmaceuticals, polymers, plastics, industrial additives, foods, and beverages.1 Its potential use in the production of novel biofuels rapidly increases the significance of levulinic acid in the process industry. The chemical synthesis of this acid from sugar in the late 20th century suffered from expensive precursors, low yields, and lack of efficient separation procedures.2,3 Worldwide consumption of levulinic acid was estimated to be 2606.2 tons in 2013 and is expected to reach 3820 tons by 2020 with a CAGR of 5.7% from 2014 to 2020. The market revenue is expected to reach USD 19.65 million by 2020 with a growth rate of 4.8% CAGR from 2014 to 2020. Pharmaceuticals and agriculture applications have the highest requirement of this acid accounting 66% of global volumes in 2013. The industries like DuPont, Segetis, and Biofine have already developed patented technologies for the production of levulinic acid by using renewable sources. With a target price of less than USD 1 per kg (which is presently between USD 5 and 8 per kg), it is anticipated that the reduction in price will create more opportunities in the field of energy, transportation, green chemicals, and specialty polymers.4 However, its critical role necessitates © XXXX American Chemical Society

an increase in the production volume in the industry and encouraged the researchers to explore novel production techniques and recovery methods to reduce the total cost of levulinic acid. Particularly, the production of carboxylic acids from waste biomass using various catalysts or via biotechnology based methods is of great interest. Conventional recovery method for carboxylic acids is costly and damaging to the environment. Therefore, an efficient, low-cost, and environmentally friendly separation technique is needed for a sustainable process.5 The process developed has to be specific for the carboxylic acid recovery since several other chemicals/components may be formed/present during the production and will remain there in the media at the time of recovery of acid.6 Several techniques, e.g., adsorption, solvent extraction, ion exchange, electrodialysis, and reactive distillation, have been tested for the recovery of carboxylic acids from dilute aqueous solutions;7 however, none of them could completely replace the conventional method in the industry. On the other hand, reactive Received: February 24, 2016 Accepted: October 25, 2016

A

DOI: 10.1021/acs.jced.6b00164 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

B

0 5.34 9.31 0 8.74 1.40 (293 K) 0.41 (298 K) 0.58 (293 K) 0.65 (293 K) 7.36 (298 K) 750 1330 800 880 820 170.33 84.93 100.16 78.11 130.23 95.00 99.00 99.80 99.50 99.00 Spectrochem, India Fisher Scientific, India Spectrochem, India SISCO, India Spectrochem, India

1.5 × 106 (303 K) 1130−1150 887−890 116.12 404.17 98.00 80.00 Sigma-Aldrich, India S. D. Fine, India

n-dodecane dichloromethane MIBK benzene 1-octanol

4-oxopentanoic acid N-methyl-N,N,N-trioctylammonium chloride dodecane dichloromethane 4-methyl pentan-2-one benzene octan-1-ol levulinic acid Aliquat 336

purity (%) supplier

The reagents used in the present equilibrium study are listed in Table 1 with their physical properties. The initial levulinic acid concentration was changed from 0.1099 to 0.5105 mol·kg−1 and prepared in distilled water.15 The organic solutions were prepared by dissolving the extractant, Aliquat 336, at varied concentrations in various diluents (DCM, MIBK, 1-octanol, benzene, and dodecane). A portion of 20 mL aqueous solution of acid was contacted with 20 mL of organic solution in a conical flask of 100 mL volume. This sample was placed in a reciprocating water shaker bath with temperature control (HS 250 basic REMI Laboratories, India) at 100 rpm, at 298 K and at 101.325 kPa for 6 h. For the clear separation of phases, this mixture was kept in a separating funnel of 60 mL volume for 2 h at 298 K. Now, the levulinic acid concentration in the aqueous phase at equilibrium was measured by titration using fresh NaOH solution of 0.01 M and phenolphthalein as an indicator. The acid concentration in the extract phase was determined from the mass balance. The reproducibility of data was checked for selected points and found to be reproducible within ±5% of accuracy. The organic phase chemicals used in this study have poor solubility in aqueous solution.

IUPAC name

2. MATERIALS AND METHODS

reagents

Table 1. Physical Characteristics of Reagents Used in the Experimental Study

mol wt(g·mol−1)

density (kg·m−3)

viscosity (mPa·s)

dipole moment, μ (× 1030)(C·m)

2 8.93 13.11 2.27 7.6

relative permittivity, εr (−)

extraction, an improved solvent extraction process, is proposed to be a promising candidate for this purpose. Besides the physical extraction, ion pair formation occurs between the target solute and the extractant present in the organic phase. The reaction results in a complex formation which gets solubilized in the organic phase. King and Kertes proposed that the nature of the acid, type of the diluent, and amount of extractant are the main factors influencing the extraction efficiency.5 Thus, the recovery efficiency of this process can be manipulated to the optimum by selecting organic phase components and adjusting process parameters such as pH, concentration, and temperature.8 Reactive extraction of levulinic acid has been considered by several researchers using various types of extractants and diluents. Senol studied the partitioning of levulinic acid between aqueous and organic phase using Alamine 308 (triisooctylamine) as the extractant dissolved in several diluents.9 Among the systems tested, cyclic alcohol/amine showed to be the most effective organic solvent for the recovery process. Uslu et al. carried out several studies on the separation of levulinic acid using trioctylamine, tripropylamine, and Amberlite LA-2 dissolved in different diluents such as alcohols, esters, and ketones to prepare the organic phase.10−13 According to their results, isoamyl alcohol was the most effective diluent for the process. Kumar and co-workers performed equilibrium and kinetic studies on the extraction of levulinic acid from aqueous solutions by using trioctylamine in 1-octanol.14 The researchers showed that the stoichiometry of levulinic acid-amine complex in the diluent was 2:1. In the present study, Aliquat 336, a quaternary ammonium salt, was used as an extractant dissolved in various types of organic diluents [benzene, dichloromethane (DCM), dodecane, methyl isobutyl ketone (MIBK), and 1-octanol] to prepare the organic phase of different compositions. Using these organic phases, the reactive extraction of levulinic acid from aqueous solution was investigated. Effect of types of diluent used in the organic phase and initial acid and extractant concentrations were analyzed on the extraction efficiency.



Article

3. RESULTS AND DISCUSSION 3.1. Physical Extraction. The experiments were carried out by equilibrating the aqueous solution of levulinic acid and organic solvent. The distribution coefficients for each solvent at different initial acid concentrations (0.1099−0.5105 mol·kg−1) were calculated and are presented in Table 2. According to the

phase prepared by using Aliquat 336 at different concentrations in different solvents at 298 K. The equilibrium data on the extraction of levulinic acid were given in Tables 3 to 7. The results showed that the extractability of the organic phase (amine extractant + organic diluent) varies with the initial concentrations of the reactants, levulinic acid, and Aliquat 336. The KD values were found to be in the range of 0.023−0.702, 0.1−1.755, 0.147−0.350, 0.415−1.266, and 0.174−2.082 for dodecane, benzene, 1-octanol, MIBK, and DCM, respectively. With the exceptions, for all solvent types and initial amine concentrations, the values of KD (= m̅ HL ; mHL = molality of acid in mHL the aqueous phase in mol·kg−1; m̅ HL = equilibrium molality of acid in the organic phase in mol·kg−1) and E% (= m̅ HL ; mHLin = mHLin initial molality of acid in the aqueous phase in mol·kg−1) increased with the increase in the initial Aliquat 336 composition in the organic system. The increase was noticeable for DCM, MIBK, and benzene. Interestingly, the increase was lowest for 1-octanol, which is a relatively polar solvent. It is most probably due the inappropriate use of Aliquat 336 with 1-octanol. Aliquat 336, a quaternary ammonium salt, has the potential of extracting carboxylic acid molecules by two mechanisms such as ion pair formation and ion exchange. The data showed that there is no consistency observed in the trend of KD with the initial concentration of acid. According to the results, the order of the distribution coefficient or degree of extraction was observed to be DCM > MIBK > benzene > 1-octanol > dodecane. In some cases, 1-octanol provided lower KD values than dodecane. However, the first three is the same for all initial concentrations of Aliquat 336 and levulinic acid. Thus, among all diluents, DCM yielded the maximum value for each acid and amine concentration levels due to the polarity and hydrogen bonding ability with the acid−amine complex. The highest reactive extraction efficiency was obtained as 67.55% (KD = 2.082) with 0.5454 mol·kg−1 Aliquat 336 in DCM for the initial levulinic acid concentration of 0.2795 mol·kg−1. Dodecane, the aliphatic hydrocarbon, exhibited the lowest extraction ability. Uslu and Kirbaslar explained that the variety of KD with solvent type is due to the difference in polarity and molecular size (diameter, cavity) of the solvents.11,12 Solvents having functional groups and intermediate molecular weights are generally proposed to have sufficient polarities for the extractive processes. Among the solvents tested in this study, DCM, 1-octanol, and MIBK are having higher polarities and suitable for reactive extraction. However, the extraction efficiency changed depending on the extent of the polarity of the solvent with the molecular structure. 3.3. Mathematical Modeling, Parameter Estimation, and Stoichiometry. The route in which the extraction of levulinic with an amine extractant (Aliquat 336) dissolved in an organic diluent at equilibrium could be explained by the mass action law. An equilibrium reaction between one levulinic acid molecule (HL represents the undissociated part of the levulinic acid molecule in the aqueous phase) and n molecules of Aliquat 336 forming 1:n complexes in the organic phase15 could be written as

Table 2. Values of Distribution Coefficient, KD (−), and Extraction Efficiency, E (%), for the Levulinic Acid Physical Extraction using Dodecane, Benzene, 1-Octanol, Methyl-isobutyl ketone (MIBK), and Dichloromethane (DCM) as Solvents at a Temperature of 298 K and a Pressure of 101.325 kPaa,b diluents

mHLin

mHL

dodecane

0.1099 0.1595 0.2795 0.4125 0.5105 0.1099 0.1595 0.2795 0.4125 0.5105 0.1099 0.1595 0.2795 0.4125 0.5105 0.1099 0.1595 0.2795 0.4125 0.5105 0.1099 0.1595 0.2795 0.4125 0.5105

0.0997 0.1469 0.2717 0.4064 0.5103 0.1054 0.1525 0.2648 0.3897 0.4813 0.0788 0.1169 0.2046 0.3496 0.4487 0.0651 0.0997 0.1867 0.3134 0.4012 0.0899 0.1356 0.2472 0.3866 0.4884

benzene

1-octanol17

MIBK

DCM

m̅ HL 0.0102 0.0126 0.0078 0.0061 0.0002 0.0045 0.0070 0.0147 0.0228 0.0292 0.0311 0.0426 0.0749 0.0629 0.0618 0.0448 0.0598 0.0928 0.0991 0.1093 0.0200 0.0239 0.0323 0.0259 0.0221

KD

E

0.103 0.087 0.030 0.016 ∼0 0.043 0.047 0.057 0.061 0.064 0.400 0.371 0.378 0.189 0.146 0.697 0.610 0.513 0.332 0.289 0.225 0.179 0.135 0.070 0.048

9.34 8.00 2.91 1.57 ∼0 4.12 4.49 5.39 5.75 6.02 28.57 27.06 27.43 15.90 12.74 41.07 37.89 33.91 24.92 22.42 18.37 15.18 11.89 6.54 4.58

a mHLin, initial molality of acid in the aqueous phase in mol·kg−1; mHL, equilibrium molality of acid in the aqueous phase in mol·kg−1; m̅ HL = equilibrium molality of acid in the organic phase in mol·kg−1. bRelative standard uncertainties in molalities, ur(mHL) = 0.10; standard uncertainties in temperature, u(T) = 0.58 K; standard uncertainties in pH, u(pH) = 0.006; standard uncertainties in pressure, u(p) = 0.10 kPa.

data, extraction efficiencies varied with the initial amount of acid in the aqueous phase and the type of the solvent used. The KD values were in the range of 3.70 × 10−4 to 0.103, 0.043 to 0.064, 0.146 to 0.400, 0.289 to 0.697, and 0.048 to 0.225 for dodecane, benzene, 1-octanol, MIBK, and DCM, respectively. Levulinic acid showed low distributions in the organic diluents. The highest partition was obtained with MIBK. This was most probably due to its relatively higher polarity. The degree of extraction was only 41% at the highest physical extraction trial. Thus, the use of amine extractant is required to increase the recovery efficiency of levulinic acid and to achieve higher KD values. 3.2. Reactive Extraction. In general, only the use of organic solvent results in a low distribution ratio for the recovery of levulinic acid, and this causes the need for the use of an amine based extractant with the organic solvent. In this study, equilibrium extraction experiments were performed by using an aqueous solution of levulinic acid (pKa = 4.5916) and the organic

KE

HL + nT̅ ↔ (T)n (HL)

(1)

where n is the solvation number of Aliquat 336. As the levulinic acid−Aliquat 336 complex is formed, it is quickly extracted into the organic phase, and the equilibrium constant of complex formation may be written by using the law of mass action.8 C



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Table 3. Values of Distribution Coefficient, KD (−), Extraction Efficiency, E (%), Loading Ratio, Z (−), Equilibrium Constant, KE, and Solvation Number of Aliquat 336, n, with the Coefficient of Linear Regression, R2, and Standard Deviation, SD: Equilibrium Results of Levulinic Acid Using Aliquat 336 in Dodecane as Solvent at a Temperature of 298 K and a Pressure of 101.325 kPaa,b mHLin 0.1099

0.1595

0.2795

0.4125

0.5105

m̅ A336in 0.1438 0.2850 0.5599 0.8252 0.1438 0.2850 0.5599 0.8252 0.1438 0.2850 0.5599 0.8252 0.1438 0.2850 0.5599 0.8252 0.1438 0.2850 0.5599 0.8252

mHL 0.1052 0.0881 0.0814 0.0747 0.1541 0.1352 0.1223 0.1117 0.2731 0.2468 0.2223 0.1986 0.3480 0.2890 0.2722 0.2572 0.4051 0.3161 0.3081 0.3000

m̅ HL 0.0047 0.0218 0.0285 0.0352 0.0054 0.0243 0.0372 0.0478 0.0064 0.0327 0.0572 0.0809 0.0645 0.1235 0.1403 0.1553 0.1054 0.1944 0.2024 0.2105

KD

E

Z

n

KE

R2

SD

0.045 0.247 0.350 0.471 0.035 0.18 0.304 0.428 0.023 0.132 0.257 0.407 0.185 0.427 0.515 0.604 0.260 0.615 0.657 0.702

4.28 19.83 25.93 32.03 3.39 15.24 23.33 29.97 2.29 11.70 20.47 28.95 15.63 29.94 34.01 37.64 20.65 38.08 39.65 41.24

0.033 0.076 0.051 0.043 0.038 0.085 0.066 0.058 0.044 0.115 0.102 0.098 0.448 0.433 0.251 0.188 0.733 0.682 0.361 0.255

1.29

0.764

0.877

0.198

1.38

0.689

0.924

0.162

1.59

0.677

0.947

0.154

0.65

0.797

0.891

0.093

0.53

0.949

0.777

0.117

a mHLin, initial molality of acid in the aqueous phase in mol·kg−1; mHL, equilibrium molality of acid in the aqueous phase in mol·kg−1; m̅ HL = equilibrium molality of acid in the organic phase in mol·kg−1; m̅ A336in, initial molality of Aliquat 336 in the organic phase in mol·kg−1. bRelative standard uncertainties in molalities, ur(mHL) = 0.10; standard uncertainties in temperature, u(T) = 0.58 K; standard uncertainties in pH, u(pH) = 0.006; standard uncertainties in pressure, u(p) = 0.10 kPa.

Table 4. Values of Distribution Coefficient, KD (−), Extraction Efficiency, E (%), Loading Ratio, Z (−), Equilibrium Constant, KE, and Solvation Number of Aliquat 336, n, with the Coefficient of Linear Regression, R2, and Standard Deviation, SD: Equilibrium Results of Levulinic Acid Using Aliquat 336 in Benzene as Solvent at a Temperature of 298 K and a Pressure of 101.325 kPaa,b mHLin 0.1099

0.1595

0.2795

0.4125

0.5105

m̅ A336in 0.1237 0.2472 0.4939 0.7401 0.1237 0.2472 0.4939 0.7401 0.1237 0.2472 0.4939 0.7401 0.1237 0.2472 0.4939 0.7401 0.1237 0.2472 0.4939 0.7401

mHL 0.0999 0.0765 0.0651 0.0531 0.1431 0.1167 0.101 0.0869 0.2477 0.2109 0.1905 0.1681 0.3131 0.2129 0.1967 0.1776 0.3629 0.213 0.1999 0.1853

m̅ HL 0.0100 0.0334 0.0448 0.0568 0.0164 0.0428 0.0585 0.0726 0.0318 0.0686 0.0890 0.1114 0.0994 0.1996 0.2158 0.2349 0.1476 0.2975 0.3106 0.3252

KD

E

Z

n

KE

R2

SD

0.100 0.437 0.688 1.07 0.115 0.367 0.579 0.835 0.128 0.325 0.467 0.663 0.317 0.938 1.097 1.323 0.407 1.397 1.554 1.755

9.10 30.39 40.76 51.68 10.28 26.84 36.68 45.52 11.38 24.54 31.84 39.86 24.09 48.38 52.31 56.94 28.92 58.28 60.85 63.71

0.081 0.135 0.091 0.077 0.133 0.173 0.118 0.098 0.257 0.278 0.180 0.151 0.804 0.808 0.437 0.317 1.194 1.204 0.629 0.439

1.27

1.815

0.935

0.140

1.08

1.306

0.953

0.099

0.88

0.947

0.961

0.074

0.75

2.000

0.850

0.132

0.77

2.839

0.788

0.167

mHLin, initial molality of acid in the aqueous phase in mol·kg−1; mHL, equilibrium molality of acid in the aqueous phase in mol·kg−1; m̅ HL = equilibrium molality of acid in the organic phase in mol·kg−1; m̅ A336in, initial molality of Aliquat 336 in the organic phase in mol·kg−1. bRelative standard uncertainties in molalities, ur(mHL) = 0.10; standard uncertainties in temperature, u(T) = 0.58 K; standard uncertainties in pH, u(pH) = 0.006; standard uncertainties in pressure, u(p) = 0.10 kPa. a

KE =

[(HL)·(T)n ] n [HL]·(mA336 ̅ )

KD =

(2)

The distribution coefficient for the extraction reaction as shown in eq 1 may be expressed as

[(HL)·(T)n ] [HL] + [L−]

(3)

The dissociation reaction of levulinic acid in the aqueous phase at equilibrium is shown as D



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Table 5. Values of Distribution Coefficient, KD (−), Extraction Efficiency, E (%), Loading Ratio, Z (−), Equilibrium Constant, KE, and Solvation Number of Aliquat 336, n, with the Coefficient of Linear Regression, R2, and Standard Deviation, SD: Equilibrium Results of Levulinic Acid Using Aliquat 336 in 1-Octanol as Solvent at a Temperature of 298 K and a Pressure of 101.325 kPaa,b mHLin 0.1099

0.1595

0.2795

0.4125

0.5105

m̅ A336in 0.1322 0.2633 0.5223 0.7771 0.1322 0.2633 0.5223 0.7771 0.1322 0.2633 0.5223 0.7771 0.1322 0.2633 0.5223 0.7771 0.1322 0.2633 0.5223 0.7771

mHL 0.0903 0.0869 0.0842 0.082 0.1316 0.1283 0.1231 0.1185 0.2299 0.2251 0.2157 0.2071 0.3536 0.349 0.3352 0.3241 0.4452 0.4384 0.423 0.4109

m̅ HL 0.0196 0.023 0.0257 0.0279 0.0279 0.0312 0.0364 0.041 0.0496 0.0544 0.0638 0.0724 0.0589 0.0635 0.0773 0.0884 0.0653 0.0721 0.0875 0.0996

KD

E

Z

n

KE

R2

SD

0.217 0.265 0.305 0.340 0.212 0.243 0.296 0.346 0.216 0.242 0.296 0.35 0.167 0.182 0.231 0.273 0.147 0.164 0.207 0.242

17.83 20.93 23.38 25.38 17.49 19.56 22.82 25.71 17.75 19.46 22.83 25.90 14.28 15.39 18.74 21.43 12.79 14.12 17.14 19.51

0.148 0.087 0.049 0.036 0.211 0.118 0.07 0.053 0.375 0.207 0.122 0.093 0.446 0.241 0.148 0.114 0.494 0.274 0.168 0.128

0.25

0.374

0.994

0.008

0.27

0.372

0.981

0.016

0.27

0.377

0.966

0.021

0.28

0.298

0.950

0.027

0.29

0.271

0.970

0.021


Table 6. Values of Distribution Coefficient, KD (−), Extraction Efficiency, E (%), Loading Ratio, Z (−), Equilibrium Constant, KE, and Solvation Number of Aliquat 336, n, with Coefficient of Linear Regression, R2, and Standard Deviation, SD: Equilibrium Results of Levulinic Acid Using Aliquat 336 in Methyl-iso-butyl Ketone as Solvent at a Temperature of 298 K and a Pressure of 101.325 kPaa,b mHLin 0.1099

0.1595

0.2795

0.4125

0.5105

m̅ A336in 0.1353 0.2692 0.5325 0.7903 0.1353 0.2692 0.5325 0.7903 0.1353 0.2692 0.5325 0.7903 0.1353 0.2692 0.5325 0.7903 0.1353 0.2692 0.5325 0.7903

mHL 0.0651 0.0658 0.0574 0.0485 0.0949 0.0907 0.0812 0.0739 0.1681 0.1517 0.1412 0.1315 0.2786 0.2468 0.2365 0.2232 0.3607 0.3186 0.3044 0.2902

m̅ HL 0.0448 0.0441 0.0525 0.0614 0.0646 0.0688 0.0783 0.0856 0.1114 0.1278 0.1383 0.1480 0.1339 0.1657 0.1760 0.1893 0.1498 0.1919 0.2061 0.2203

KD

E

Z

n

KE

R2

SD

0.688 0.670 0.915 1.266 0.681 0.759 0.964 1.158 0.663 0.842 0.979 1.125 0.481 0.671 0.744 0.848 0.415 0.602 0.677 0.759

40.76 40.12 47.77 55.86 40.51 43.14 49.10 53.68 39.86 45.73 49.48 52.95 32.46 40.17 42.66 45.89 29.35 37.59 40.38 43.16

0.331 0.164 0.099 0.078 0.477 0.256 0.147 0.108 0.823 0.475 0.260 0.187 0.989 0.616 0.330 0.240 1.107 0.713 0.387 0.279

0.34

1.266

0.796

0.072

0.30

1.239

0.958

0.026

0.29

1.258

0.992

0.011

0.30

0.980

0.948

0.029

0.33

0.903

0.940

0.034


Ka

HL ↔ H+ + L−

(4)

Ka =

[H+][L−] [HL]

(5) −

The dissociation constant (Ka) of levulinic acid in water is given by eq 5.

From eq 5, the concentration of dissociated part ([L ]) of levulinic acid may be written in terms of undissociated acid E



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Table 7. Values of Distribution Coefficient, KD (−), Extraction Efficiency, E (%), Loading Ratio, Z (−), Equilibrium Constant, KE, and Solvation Number of Aliquat 336, n, with Coefficient of Linear Regression, R2, and Standard Deviation, SD: Equilibrium Results of Levulinic Acid Using Aliquat 336 in Dichloromethane as Solvent at a Temperature of 298 K and a Pressure of 101.325 kPaa,b mHLin 0.1099

0.1595

0.2795

0.4125

0.5105

m̅ A336in 0.0832 0.1693 0.3507 0.5454 0.0832 0.1693 0.3507 0.5454 0.0832 0.1693 0.3507 0.5454 0.0832 0.1693 0.3507 0.5454 0.0832 0.1693 0.3507 0.5454

mHL 0.0627 0.0562 0.0466 0.0370 0.0877 0.0758 0.0643 0.0519 0.1440 0.1257 0.1073 0.0907 0.3121 0.2600 0.2043 0.1508 0.4350 0.3607 0.2786 0.1969

m̅ HL 0.0472 0.0537 0.0633 0.0729 0.0718 0.0837 0.0952 0.1076 0.1355 0.1538 0.1722 0.1888 0.1004 0.1525 0.2082 0.2617 0.0755 0.1498 0.2319 0.3136

KD

E

Z

n

KE

R2

SD

0.753 0.956 1.358 1.970 0.819 1.104 1.481 2.073 0.941 1.224 1.605 2.082 0.322 0.587 1.019 1.735 0.174 0.415 0.832 1.593

42.94 48.86 57.59 66.33 45.02 52.48 59.70 67.47 48.48 55.03 61.61 67.55 24.34 36.97 50.47 63.44 14.79 29.35 45.43 61.43

0.567 0.317 0.180 0.134 0.863 0.494 0.271 0.197 1.628 0.908 0.491 0.346 1.206 0.901 0.594 0.480 0.907 0.885 0.661 0.575

0.50

2.572

0.965

0.042

0.48

2.719

0.981

0.029

0.41

2.709

0.990

0.018

0.88

2.945

0.993

0.033

1.15

3.265

0.995

0.036


log[KD(1 + 10 pH − pKa)] = log KE + n log(mA336in ) ̅

concentration ([HL]), pKa, and pH of the aqueous solution as [L−] = [HL](1 + 10 pKa − pH)

The graphs between log[KD(1 + 10pH−pKa)] and log(m̅ A336in) were drawn and best fitted to estimate the value of equilibrium constant (log KE) from the intercept and n from the slope. Figure 1a−e shows these plots, and the results are presented in Tables 3 to 7 for different solvents. The values of n were mostly obtained as about 1 for inactive diluents (dodecane and benzene) at low acid concentrations. This suggests the existence of a stoichiometric association between the individual acid and extractant molecules. The values of n deviated in case of active diluents (1-octanol, MIBK, and DCM) showing higher order of stoichiometric reactions between acid and amine such as 2:1, 3:1, etc. Higher values of dielectric constant for polar diluents were responsible for the values of n less than 1. The calculated experimental values of Z (= m̅ HL ; m̅ HL = equilibrium molality of acid

(6)

Then, substituting the [(HL)·(T)n ] and [L−] from eq 3 and eq 6, respectively, in eq 3, eq 7 was obtained. KD =

n KE(mA336 ̅ )

(1 + 10 pH − pKa)

(7)

The remaining amine concentration which is unreacted with the levulinic acid molecule in the extract phase at equilibrium (m̅ A336) is represented as = mA336in − n[(HL)(T)n ] mA336 ̅ ̅

(8)

The value of m̅ A336 from eq 8 is placed in eq 7 resulting in eq 9. KD =

mA336in ̅

in the organic phase in mol·kg−1; m̅ A336in = initial molality of Aliquat 336 in the organic phase in mol·kg−1) were observed to be in the range of 0.033−0.733 for dodecane, 0.081−1.194 for benzene, 0.036−0.494 for 1-octanol, 0.078−1.107 for MIBK, and 0.134−1.628 for DCM. These values also suggested an overloading of acid on Aliquat 336 and the possibility of formation of higher order complex formation in the organic phase. The diluent’s strength of the complex solvation was observed in the following order with Aliquat 336: DCM > MIBK > benzene > dodecane > 1-octanol. Among the tested diluents, DCM (chlorinated hydrocarbon) provided best solvating medium for the levulinic acid−Aliquat 336 complex. An extremely low value of equilibrium constant was found with dodecane. The acid−amine solvates are stabilized by hydrogen bonding between the diluent and the complex. This is confirmed from the significant difference between the KE values of diluents used. Uslu and Kirbaslar10 studied the recovery of levulinic acid by TOA dissolved in five

KE(mA336in − n[(HL)(T)n ])n ̅ (1 + 10 pH − pKa)

(9)

For the estimation of KE and n it may be assumed that initial concentration of Aliquat 336 (m̅ A336in) is more compared to that of levulinic acid-Aliquat 336 complex concentration in the organic phase(i.e., m̅ A336in ≫ n[(HL)(T)n ]. With this simplification, eq 9 may be represented as KD =

KE(mA336in )n ̅ (1 + 10 pH − pKa)

(11)

(10)

When the concentration of the solute (i.e., levulinic acid) is more in the aqueous phase, then this particular assumption is not valid as the concentration of acid−amine solvate in the organic phase will increase. Now, eq 10 is linearized by taking log on both sides to determine the equilibrium parameters, n and KE. F



Article

Figure 1. Determination of KE and n using Aliquat 336 dissolved in (a) dodecane, (b) benzene, (c) 1-octanol, (d) MIBK, and (e) DCM, for levulinic acid reactive extraction. Symbols: ■, 0.1099 mol·kg−1; ○, 0.1595 mol·kg−1; *, 0.2795 mol·kg−1; ×, 0.4125 mol·kg−1; +, 0.5105 mol·kg−1; ---, linear fit lines.

diethyl carbonate by Uslu and Kırbaslar.11 Kinetic and equilibrium studies were also performed with tripropylamine (TPA) diluted in toluene by Uslu at 298.15 K.12 He found a maximum KD of 15.4 at 2.79 mol·kg−1 TPA concentration. In another study by

different alcohols and two different ketones. A maximum removal efficiency of levulinic acid was found to be 91.87% with isoamyl alcohol and TOA system (2.16 mol·kg−1). The maximum value of KD (= 5.754) was obtained with TOA (= 2.16 mol·kg−1) + G



Article

Uslu and his co-workers13 isoamyl alcohol with Amberlite LA-2 (2.24 mol·kg−1) gave a maximum KD of 68.02. In the present study, a highest KD of 2.082 achieved with 0.8252 mol·kg−1 Aliquat 336 in DCM. 3.4. Calculation of Minimum Solvent to Feed (S/F) Ratio and Number of Theoretical Stages of Extraction Column. The feasibility of the extraction process was assessed by calculating minimum S/F ratio required for the recovery of levulinic acid and the number of theoretical stages.18

x − xout ⎛S⎞ ⎜ ⎟ = in ⎝ F ⎠min Dx in − yin

size are the important parameters for the selection of organic phase diluent.

■

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■

where xin and xout are the concentrations in the feed and the raffinate, and yin is the initial acid concentration in the extract phase. Therefore, the (S/F)min was calculated and shown in Table 8 for different diluent systems with ALA2. As a rule of thumb for an Table 8. Minimum Solvent-to-Feed (S/F) Ratio and Number of Theoretical Stages of Extraction Column solvent

KD (−)

(S/F)min

NTS

0.023−0.702 0.100−1.755 0.147−0.350 0.415−1.266 0.174−2.082

0.587−0.996 0.363−0.910 0.740−0.870 0.441−0.707 0.324−0.850

0.32−1.18 0.50−1.87 0.58−0.84 0.92−1.59 0.62−2.04

extraction process with a finite number of extraction stages, the actual S/F ratio is 1.5 times the minimum S/F ratio.19 Now, for a counter-current extraction process, the theoretical stages (NTS = number of theoretical stages) were found using the modified Kremser equation given in eq 13 with the extraction factor (ε) from eq 14.

NTS =

⎡⎛ x − y / K ⎞ 1⎤ ln⎢⎜ xin ‐ yin / KD ⎟(1 − 1/ε) + ε ⎥ ⎣⎝ out in D ⎠ ⎦ ln ε

REFERENCES

(1) Bozell, J. J.; Moens, L.; Elliott, D. C.; Wang, Y.; Neuenscwander, G. G.; Fitzpatrick, S. W.; Bilski, R. J.; Jarnefeld, J. L. Production of levulinic acid and use as a platform chemical for derived products. Resour., Conserv. Recycl. 2000, 28, 227−239. (2) Corma, A.; Iborra, S.; Velty, A. Chemical routes for the transformation of biomass into chemicals. Chem. Rev. 2007, 107, 2411−2502. (3) Galletti, A. M. R.; Antonetti, C.; De Luise, V.; Licursi, D.; O Di Nasso, N. N. Levulinic acid production from waste biomass.Levulinic acid production from waste biomass. BioResources 2012, 7, 1824−1835. (4) https://www.grandviewresearch.com/press-release/globallevulinic-acid-market (accessed May 23, 2016). (5) Kertes, A. S.; King, C. J. Extraction Chemistry of Fermentation Product Carboxylic Acids. Biotechnol. Bioeng. 1986, 28, 269−282. (6) Marti, M. E.; Gurkan, T. Selective recovery of pyruvic acid from two and three acid aqueous solutions by reactive extraction. Sep. Purif. Technol. 2015, 156, 148−157. (7) Lopez-Garzon, C. S.; Straathof, A. J. J. Recovery of carboxylic acids produced by fermentation. Biotechnol. Adv. 2014, 32, 873−904. (8) Martı, M. E.; Gürkan, T.; Doraiswamy, L. K. Equilibrium and kinetic studies for reactive extraction of pyruvic acid with trioctylamine in 1-octanol. Ind. Eng. Chem. Res. 2011, 50, 13518−13525. (9) Senol, A. Extraction equilibria of formic and levulinic acids using Alamine 308/diluent and conventional solvent systems. Sep. Purif. Technol. 2000, 21, 165−179. (10) Uslu, H.; Kirbaslar, S. I. Investigation of levulinic acid distribution from aqueous phase to organic phase with TOA extractant. Ind. Eng. Chem. Res. 2008, 47, 4598−4606. (11) Uslu, H.; Kirbaslar, S. I. Equilibrium Studies of Extraction of Levulinic Acid by (Trioctylamine (TOA) + Ester) Solvents. J. Chem. Eng. Data 2008, 53, 1557−1563. (12) 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. (13) Uslu, H.; Kirbaslar, S. I.; Wasewar, K. L. Reactive extraction of levulinic acid by Amberlite LA-2 Extractant. J. Chem. Eng. Data 2009, 54, 712−718. (14) Kumar, T. P.; Vishwanadham, B.; Prasanna Rani, K. N.; Mallikarjun, M.; Basava Rao, V. V. Reactive extraction of levulinic acid from aqueous solutions with tri-n-octylamine (TOA) in 1-octanol: Equilibria, Kinetics and Model Development. Chem. Eng. Commun. 2010, 198, 572−589. (15) Kumar, S.; Uslu, H.; Datta, D.; Rarotra, S. Rajput, K. Investigation of extraction of 4-oxopentanoic acid by n,n-dioctyloctan-1-amine in six different diluents: equilibrium study. J. Chem. Eng. Data 2015, 60, 1447−1453. (16) John, A. D. Lange’s Handbook of Chemistry, XXth ed.; McGrawHill Book Co. Inc.: New York, 1972. (17) Datta, D.; Marti, M. E.; Uslu, H.; Kumar, S. Extraction of levulinic acid using tri-n-butyl phosphate and tri-n-octylamine in 1-octanol: Column design. J. Taiwan Inst. Chem. Eng. 2016, 66, 407−413. (18) Krzyzaniak, A.; Schuur, B.; de Haan, A. Equilibrium studies on lactic acid extraction with N,N-didodecylpyridin-4-amine (DDAP) extractant. Chem. Eng. Sci. 2014, 109, 236−243. (19) Seader, J. D.; Henley, E. J.; Roper, D. K. Separation Process Principles, 3rd ed.; John Wiley & Sons. Inc.: New York, 2009.

(12)

dodecane benzene 1-octanol MIBK DCM

AUTHOR INFORMATION

(13)

S (14) F The values of NTS showed that at maximum two theoretical stages would be sufficient to achieve the desired extraction efficiency of levulinic acid in a continuous extraction column. ε = KD

4. CONCLUSION Here in this study, the extraction power of Aliquat 336 for levulinic acid was investigated for different compositions of the components in the aqueous and organic phases. The extractant was dissolved in five different solvents [benzene, dichloromethane (DCM), dodecane, methyl isobutyl ketone (MIBK), 1-octanol], and the effect of the solvent type was explained. The equilibrium data were used to calculate distribution coefficient (KD), degree of extraction (E%), loading ratio (Z), and complexation constant (KE). Among the tested diluents, DCM yielded the highest extraction efficiency with 0.5454 mol·kg−1 Aliquat 336 in DCM, and at 0.2795 mol·kg−1 levulinic acid. KD and E% were obtained as 2.08 and 67.55%, respectively. The proposed model showed that 2:1 and 3:1 levulinic acid− Aliquat 336 complexes were formed in 1-octanol, DCM, and MIBK during the reactive extraction along with 1:1 type of complexes. The results clearly show that polarity and molecular H


Equilibrium Study on the Extraction of Levulinic Acid from Aqueous

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