Ind. Eng. Chem. Res. 2011, 50, 1003–1011
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Reactive Extraction of Itaconic Acid Using Quaternary Amine Aliquat 336 in Ethyl Acetate, Toluene, Hexane, and Kerosene Kailas L. Wasewar,*,† Diwakar Shende,† and Amit Keshav‡ Department of Chemical Engineering, VisVesVaraya National Institute of Technology, Nagpur 440010, India, and Department of Chemical Engineering, National Institute of Technology (NIT) Raipur, Chhattisgarh 492010, India
The synthesis method of producing itaconic acid by catalytic condensation of succinic acid and formalin is unsustainable and expensive because it requires huge chemicals, consumes more energy, and discharges harmful chemicals. Production of this acid by fermentation is a relatively clean and less expensive process. The highest cost factor for the acid is the recovery of acid present in dilute form. Reactive extraction is one of the cleaner and more energy-efficient technologies for the recovery of carboxylic acids from dilute streams. Reactive extraction of itaconic acid from aqueous solution using Aliquat 336 (quaternary amine) as the extractant in various diluents was studied. The study highlighted the effects of ester (ethyl acetate), inert (kerosene), aromatic (toluene), and alkane (hexane) on the degree of solvation/ion exchange of the extractants. A comparison among the different categories of diluents was made. The results were presented in the form of distribution coefficient, loading ratio, and equilibrium complexation constant. In most cases, a 1:1 acid-amine complex was observed. Also, attempts were made to relate the distribution coefficient with the various physicochemical properties of the diluent. 1. Introduction Itaconic acid is a dicarboxylic acid that is soluble in water, acetone, and ethanol, moderately soluble in acetic acid, slightly soluble in organic solvents, and very slightly soluble in benzene, chloroform, ether, carbon disulfide, and petroleum ether. Itaconic acid is a functionalized analogue of acrylic acid, the simplest conjugated alkenoic acid.1 Itaconic acid finds its place in various industrial applications. It is used in paints to improve the quality and as a fiber carpet sizing agent to make carpet more durable. Itaconic acid can react with acrylic and methacrylic acid or their esters to prepare resins that can be widely used in emulsion coating, leather coating, and coatings for cars, refrigerators, and other electrical appliances to improve adhesion, color, and weather resistance. With (chloroalkyl)dimethylbenzylammonium chloride added, they can be used to prepare a water-soluble coating for food packaging to reduce bacteria contamination. Esters of itaconic acid can be used in paint, ion-exchange resin, lubricant, binder, plasticizer, and sealant and molding plastics. Itaconic acid polymer has a special luster and transparency; it is fit for making synthetic cut stone and special lens. Itaconic acid can be manufactured by the catalytic condensation of succinic acid derivatives with formaldehyde.2 Although the synthesis process is simple, it still suffers from a number of disadvantages: consumption of lot of chemicals, high energy utilization, and harmful byproduct generation. Fermentation is a relatively clean method to manufacture itaconic acid. Aspergilluss terreus species, grown under phosphate-limited conditions, are known to produce itaconic acid by fermentation.3 Fermentation is an important replacement in the petrochemical route for the production of a wide range of carboxylic acids like propionic acid, lactic acid, acetic acid, citric acid, etc. A stumbling block in the use of fermentation to produce these * To whom correspondence should be addressed. Phone: +91-7122801561. Fax: +91-712-2223230 or -2223969. E-mail: k_wasewar@ rediffmail.com. † Visvesvaraya National Institute of Technology. ‡ National Institute of Technology (NIT) Raipur.
acids is the difficulty in recovery from dilute solutions, in which they are produced. The main problem with fermentation technology is that, as the acid is generated, the pH of the system falls. Lowering of the pH destroys the bacterial species responsible for growth. This leads to low acid product yield and concentration. A number of recovery methods are available like precipitation, distillation, membrane bioreactor, liquid surfactant membrane extraction, adsorption, direct distillation, electrodialysis, reactive extraction, reverse osmosis, anionexchange distillation, supported membranes, etc.4 Calcium hydroxide precipitation is the industrially used recovery method. However, it has a few shortcomings: consumption of large quantities of reagents (H2SO4 and lime); a huge amount of waste generation per ton of acid produced; waste disposal problem, and very poor sustainability. Dialysis has good potential but has drawbacks of the need for frequent cleaning, membrane fouling, and the requirement of a large dialysis unit compared to the fermenter. Electrodialysis allows the simultaneous separation and concentration of the acid but requires higher power consumption. Ion exchange is a reliable technology but requires a large amount of chemicals and has huge waste generation. The distillation method is a well-established technology. Its drawbacks are the formation of high-boiling internal esters and dimers and consumption of more power.4 Reactive extraction with the proper selection of diluents and extractants can provide high selectivity and extraction but suffers from toxicity problems of the solvents toward microbial strains. Recovery of solute species can be achieved by solvent extraction, and reactive extraction has received increasing attention.5-10 Each of the above separation methods has their advantages and disadvantages, yet reactive extraction is one of the sustainable technologies, widely used for carboxylic acid extraction. With proper selection of the extractant and diluents, reactive extraction can be proven to be an efficient and reliable process with higher concentration and recovery of the acid. Generally, the acid content in fermentation broth/waste stream sources is less than 10% w/w. The separation, purification, and preconcentration of itaconic acid is rather difficult due to its
10.1021/ie1011883 2011 American Chemical Society Published on Web 12/15/2010
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Ind. Eng. Chem. Res., Vol. 50, No. 2, 2011
chemical behavior because it has a strong affinity to water. The high solubility in water causes traditional solvents such as alcohols, ethers, esters, and inert diluents (hexane, n-heptane), etc., to give low distribution coefficients. Thus, physical extraction with conventional solvents is not an efficient method for the recovery of itaconic acid. In order to increase the selectivity and yield of acid, a combination of diluent with an extractant, which can chemically complex with acid, was tried.4-9 The improved results laid down the establishment of technology of reactive extraction for the recovery of carboxylic acids. The advantages for extractive fermentation include high reactor productivity, ease in reactor pH control without requiring base addition, and use of a high-concentration substrate as the process feed to reduce process wastes and production costs. Extractive fermentation also allows the process to produce and recover the fermentation product in one continuous step and to reduce the downstream processing load and recovery costs. Reactive extraction involves the use of an extractant-diluent system to extract the acid. Extractants are usually classified as (i) anion-exchange extractants (e.g., aliphatic primary, secondary, and tertiary amines), which form ion pairs (salts) in an acidic medium, (ii) cation-exchange extractants (e.g., phosphine and phosphoric acid), which exchange proton with the cation, (iii) solvating extractants (e.g., phosphoric and phosphinic acid, esters, and phosphinoxides), which are Lewis bases and form nonstoichiometric compounds with neutral solutes, and (iv) chelate-forming extractants (e.g., aliphatic and aromatic hydroxyines), which exchange the cation and form coordinate binding.7 Extractants are generally viscous or solid, so they are dissolved in diluents, which improve their physical properties like the surface tension and viscosity. Diluents provide the solution of the extractants and also general and specific solvation to the acid-extractant complexes formed. Polar diluents are more favorable than zero-polarity, low-dielectric-constant, aliphatic or aromatic hydrocarbons. Solvation of the whole extractant-acid complex is based on dipole-dipole interaction and was found to play an important role in the neutralization reaction between acid and extractant, which is promoted by increasing the polarity of the diluent. Wide literature is available on reactive extraction of different carboxylic acids from aqueous streams, but very few can be found for extraction of itaconic acid from dilute streams. The extraction of dicarboxylic acids (itaconic, maleic, malic, oxalic, tartaric, and succinic acid) from aqueous solutions with tributylphosphate dissolved in dodecane was studied at different volume-phase ratios.10 Hano et al.11 (1990) studied the extraction equilibria of different organic acids using tri-n-octylphosphine oxide (TOPO) in hexane. TOPO + hexane, a relatively nontoxic extractant-diluent combination, was used, and an equilibrium complexation constant value of 80.8 was obtained for itaconic acid. The selective separation of itaconic acids by amine extractants was studied by Bressler and Braun.12 Loading and distribution curves as well as Fourier transform IR and fluorescence spectra were recorded. Acid-base-coupled extractants composed of di-2-ethylhexylphosphoric acid and a methyltriocylammonium cation in dichloromethane were found to be selective for the more hydrophobic itaconate, which is located in the apolar envelope of the reverse micelle.13 In the present paper, reactive extraction of itaconic acid using Aliquat 336 in various diluents was studied. The study highlighted the effects of ester (ethyl acetate), inert (kerosene), aromatic (toluene), and alkane (hexane) on the degree of solvation/ion exchange of the extractant. Physical and chemical
Figure 1. Physical extraction of itaconic acid in various diluents at 305 K.
extraction experiments were conducted. Values of the distribution coefficient and degree of extraction using physical and chemical extraction were compared. Also, attempts were made to relate the equilibrium complexation constant with the diluent properties. 2. Experimental Section 2.1. Chemicals. Aliquat 336 (trioctylmethylammonium chloride, Himedia, India), a quaternary amine, is a mixture of C8-C10 with a minimum assay of 80%, a molecular weight of 404.17, and a density of 0.888 g/cm3. Itaconic acid was purchased from Himedia, India. Diluents ethyl acetate, toluene, hexane, and kerosene of analytical grade were purchased from Ranbaxy, India, and were used without further purification. For titration, NaOH was used and obtained from S.d. Fine-Chem Ltd., India. A phenolphthalein solution (pH range 8.2-10.0) was used as an indicator. A low initial aqueous concentration of acid (0.05-0.2 kmol/ m3) was used with the goal of finding the effectiveness reactive extraction for the recovery of acid present in dilute form, and the concentration is not expected to be greater than 0.2 kmol/m3 in waste streams and in fermentation broths. 2.2. Extraction Method. The experiments were carried out in conical flasks (100 mL). Extraction experiments involved the shaking of equal volumes (20 cm3) of aqueous and organic phases for 12 h in a constant-temperature (305 K) water bath (Remi, India), followed by settling of the mixture for at least 2 h at the same temperature (305 K). The aqueous-phase pH was measured by an Orion 3 star pH benchtop (Thermo Electron Corp., Marietta, OH). The aqueous-phase acid concentration was determined by titration with NaOH. The results of the above methods were noted when NaOH was prepared fresh every time before titration was to be carried out. The acid content in the organic phase was determined by mass balance. The few experiments were repeated to check the consistency and found to be within the limit of (2%. 3. Results and Discussion 3.1. Physical Extraction. Physical extraction of itaconic acid using ethyl acetate, kerosene, toluene, and hexane was performed and is shown in Figure 1. Extraction of itaconic acid by diluent alone was accounted for by three phenomena: (i) ionization of acid in the aqueous phase (KHA); (ii) partition of the undissociated acid in the organic phase (P); (iii) dimerization of acid in the organic phase (D).7 These have been described as follows:
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Table 1. Partition Coefficient, Dimerization Constant, Distribution Coefficient, and Degree of Extraction for Itaconic Acid Extracted from Water into Organic Solvents at 305 K ([HA]org ) P[HA]aq + D[HA]aq2) diluent
partition coefficient (P)
dimerization coefficient (D)
range of KD
avg. KD
range of E %
avg. E %
ethyl acetate kerosene toluene hexane
0.457 0.009 0.13 0.15
3.578 0.389 2.374 0.345
0.5-0.83 0.005-0.06 0.01-0.2 0.04-0.24
0.72 0.047 0.08 0.14
36-47 2-6.2 1.3-17.3 4-19
41.6 4.4 8.55 11.97
1. Ionization of the acid in an aqueous solution HAaq T H+ + AKHA ) [H+][A-]/[HA] ) 1.41 × 10-4 kmol/m3
(1) (2)
2. Partition of the undissociated molecular acid between the two phases, aqueous (aq) and organic (org) HAaq T HAorg (3) P ) [HA]org /[HA]aq 3. Dimerization of the acid in the organic phase: 2HAorg T HA2,org D ) [HA]2,org /[HA]org2
(4) (5) (6)
The overall distribution coefficient for physical extraction (KDdiluent) can be written in terms of these parameters as KDdiluent
are offered by the reactive extraction technique by employing organophosphorous compounds and amines, which have proven to be effective in the recovery of carboxylic acids.7 3.2. Chemical Extraction. Aliquat 336, a quaternary amine, was used in the concentration range of 10-30% (0.19-0.59 kmol/m3) for extraction of itaconic acid. Quaternary ammonium chloride (Aliquat 336) extracts both the dissociated and undissociated forms of the acids.14 A higher concentration of Aliquat 336 was not taken because it was highly viscous and would lead to the problem of third-phase formation during extraction. Because Aliquat 336 is highly viscous, a diluent was used in association with it to improve its physical properties, thus allowing easier handling. The diluent lowered the viscosity of Aliquat 336 and decreased the surface tension at the interface. For extraction of itaconic acid by Aliquat 336 with chemical interaction, the distribution coefficient and degree of extraction (E%) were defined as KDoverall )
P + 2P2D[HA]aq [HA]org,total [HA]org + 2[HA]2 ) ) ) [HA]aq,total [HA]aq + [A-] 1 + KHA /[H+]aq
(7) For the dilute concentration of acid (used in the study), it can be fairly assumed that the second term in the denominator of the above equation can be neglected KDdiluent ) P + 2P2D[HA]aq
(8)
[HA]org [HA]aq + [A-]aq
(11)
and E% )
100 × KDoverall 1 + KDoverall
(12)
Extraction involves a chemical reaction between the quaternary amine and acid. Figures 2-5 show the chemical equilibria of
or it can be written in another form as [HA]org ) P[HA]aq + 2P2D[HA]2aq
(9)
The degree of extraction (E %) of itaconic acid in respective diluents is expressed as E % ) KDdiluent × 100/(1 + KDdiluent)
(10)
Equation 9 was fitted to the experimental value (Figure 1) to yield the values of P and D. The values of the partition coefficient, dimerization constant, distribution coefficient, and degree of extraction are given in Table 1. The values of P and D are found as 0.457 and 3.578 for ethyl acetate, 0.009 and 0.389 for kerosene, 0.15 and 0.345 for hexane, and 0.13 and 2.374 for toluene. The trend of the P and KD values is observed as ethyl acetate (ester) > hexane (alkane) > toluene (aromatic) > kerosene (inert). The KDdiluent values for all diluents lie between 0.005 and 0.83, which is not sufficiently high. Also, the degree of extraction is very low. The values of the distribution coefficients were found to be higher in ethyl acetate than in other diluents. Itaconic acid has a high affinity to water and a low relative volatility, which renders it difficult to separate. The low activity of itaconic acid toward these diluents, i.e., its higher solubility in water than in organic solvents, is the cause of the low distribution coefficient ( hexane (alkane) > toluene (aromatic) > kerosene (inert). The KDdiluent values for all diluents lies between 0.005 and 0.83, which is not sufficiently high. Also, the degree of extraction is very low. Reactive extraction enhanced significantly the extraction of itaconic acid in the organic phase. Reactive extraction was represented in terms of equilibrium complexation constants, loading ratios, and distribution coefficients. 1:1 and 2:1 acid-amine complexes were formed in the present case. The results obtained are useful for the design of the reactive extraction process for the recovery of itaconic acid.
Ind. Eng. Chem. Res., Vol. 50, No. 2, 2011
Nomenclature -
[A ] ) concentration of dissociated acid in the aqueous phase (kmol/m3) [B] ) concentration of extractant in the organic phase (kmol/m3) [H+] ) H+ ion concentration in the aqueous phase (kmol/m3) [HA] ) acid concentration (kmol/m3) [R4N+Cl-:(HA)2] ) concentration of the 2:1 acid-extractant complex (kmol/m3) [R4N+Cl-:(HA)n] ) concentration of the n:1 acid-extractant complex (kmol/m3) [R4N+Cl-:HA] ) concentration of the 1:1 acid-extractant complex (kmol/m3) D ) dimerization constant (m3/kmol) E % ) degree of extraction KD ) distribution coefficient of acid in the organic phase KE(1:1) ) extraction equilibrium constant for the 1:1 acid-extractant complex (m3/kmol) KE(2;1) ) extraction equilibrium constant for the 2:1 acid-extractant complex (m3/kmol)2 KE(n:1) ) extraction equilibrium constant for the n:1 acid-extractant complex (m3/kmol)n KHA ) ionization constant of itaconic acid ) 1.41 × 10-4 kmol/ m3 P ) partition coefficient z ) loading ratio Subscripts aq ) aqueous phase org ) organic phase 0 ) initial Superscripts diluent ) for diluent only overall ) for extractant + diluent
Literature Cited (1) Tate, B. E., Grayson, M., Eckroth, D., Eds. Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed.; John Wiley & Sons: New York, 1981; Vol. 13. (2) Shekhawat, D.; Jackson, J. E.; Miller, D. J. M. Process Model and Economic Analysis of Itaconic Acid Production from Dimethyl Succinate and Formaldehyde. Bioresour. Technol. 2006, 2, 342. (3) Shekhawat, D.; Kirthivasan, N.; Jackson, J. E.; Miller, D. J. U.S. Patent 6,504,055, 2003.
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(4) Wasewar, K. L.; Yawalkar, A. A.; Moulijn, J. A.; Pangarkar, V. G. Fermentation of Glucose to Lactic Acid Coupled with Reactive Extraction: A Review. Ind. Eng. Chem. Res. 2004, 43, 5969. (5) Tamada, J. A.; King, C. J. Extraction of Carboxylic Acids with Amine Extractants, (3) Effect of Temperature, Water Co-extraction, and Process Considerations. Ind. Eng. Chem. Res. 1990, 29, 1333. (6) Wasewar, K. L.; Heesink, A. B.; Versteeg, G. F.; Pangarkar, V. G. Equilibria and Kinetics for Reactive Extraction of Lactic Acid Using Alamine 336 in Decanol. J. Chem. Technol. Biotechnol. 2002, 77, 1068. (7) Kertes, A. S.; King, C. J. Extraction Chemistry of Fermentation Product Carboxylic Acids. Biotechnol. Bioeng. 1986, 28, 269. (8) Ricker, N. L.; Pittman, E. F.; King, C. J. Solvent Extraction with Amines for Recovery of Acetic Acid from Dilute Aqueous Industrial Streams. J. Sep. Process Technol. 1980, 1 (2), 23. (9) Jung, M.; Schierbaum, B.; Vogel, H. Extraction of Carboxylic Acids from Aqueous Solutions with the Extractant System Alcohol /Tri-nalkylamines. Chem. Eng. Technol. 2000, 23, 70. (10) Kyuchoukov, G.; Morales, A. F.; Albet, J.; Malmary, G.; Molinier, J. On the Possibility of Predicting the Extraction of Dicarboxylic Acids with Tributylphosphate Dissolved in a Diluent. J. Chem. Eng. Data 2008, 53 (3), 639. (11) Hano, T.; Matsumoto, M.; Ohtake, T.; Sasaki, K.; Hori, F.; Kawano, Y. Extraction Equilibria of Organic acid with Tri-n-octylphosphine Oxide. J. Chem. Eng. Jpn. 1990, 6, 734. (12) Bressler, E.; Braun, S. Separation Mechanisms of Citric and Itaconic Acids by Water-Immiscible Amines. J. Chem. Technol. Biotechnol. 1999, 74 (9), 891. (13) Matsumoto, M.; Otono, T.; Kondo, K. Synergistic Extraction of Organic Acids with Tri-n-octylamine and Tri-n-butylphosphate. Sep. Purif. Technol. 2001, 24, 337. (14) Kyuchoukov, G.; Yankov, D.; Molinier, J.; Albet, J. Mechanism of Lactic Acid Extraction with Quaternary Ammonium Chloride (Aliquat 336). Ind. Eng. Chem. Res. 2005, 44, 5733. (15) Kahya, E.; Bayraktar, E.; Mehmetoglu, U. Optimization of Process Parameters for Reactive Lactic Acid Extraction. Turk. J. Chem. 2001, 25, 223. (16) Tamada, J. A.; Kertes, A. S.; King, C. J. Extraction of Carboxylic Acids with Amine Extractants, (1) Equilibria and Law of Mass Action Modeling. Ind. Eng. Chem. Res. 1990, 29, 1319. (17) Bora, M. M. Study of Reactive Extraction of Certain Beta-lactum Antibiotics: Equilibrium and Kinetics. Ph.D. Dissertation, Gauhati University, Gauhati, India, 2000. (18) Kosower, M. The Effect of Solvent on Spectra. I. A New Empirical Measure of Solvent Polarity: Z values. J. Am. Chem. Soc. 1958, 80, 3253. (19) Tamada, J. A.; King, C. J. Extraction of Carboxylic Acids with Amine Extractants. 2. Chemical Interaction and Interpretation of Data. Ind. Eng. Chem. Res. 1990, 29, 1327.
ReceiVed for reView May 30, 2010 ReVised manuscript receiVed October 29, 2010 Accepted November 26, 2010 IE1011883
