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low temperature characteristics in the resin. Although the presence of the oxygen-containing ring in the pimelic acid derivative results in a sacrifice of low temperature characteristics, there is less difference in its performance in the two resins, both as to modulus and compatibility. I n addition, it exhibits a better permanence and heat stability than either the same alkyl pinates or sym-homopinates. Where compatibility is borderline] the incorporation of primary plasticizers-e.g., dioctyl phthalate-with such esters might be desirable. The terpene-derived acids described, two of which yield esters comparable to those of sebacic acid in phyEica1 properties and performance as lubricants and plasticizers, can be made from constituents of domestic turpentine. LITERATURE CITED
( 1 ) Delepine, AT., Bull. SOC. chim., France, 3 (5), 1369-82 (1936).
(2) Guha, P. C., and Ganapathi, K., Current Sci. ( I n d i a ) , 5, 244 (1936).
Vol. 41, No. 4
(3) Halbrook, K.J., and Lawrence, R. V., private communication. (4) Kent, D. L., and Weaver, P. J., India Rubber World, 115, 813-16 (1 947). (5) Magne, F. C., and Mod, R. R., I N D . ENG.CHEM.,4 5 , 1546-7 (1953). (6) Murphy, C. M., O'Rear, J. G., and Zisman, W. A., Ibid., 45, 11930 (1953). (7) Ratchford, W. P., and Rehberg, C. E., Anal. Chem., 21, 1417-19 (1949). (8) Rider, D. K., Sumner, J. K., and Myers, R. J., I N D .E N G .CHEM., 41,709-15 (1949). (9) Stinson, J. S., and Lawrence, R. V., J . 070. Chem., 19, 1047-53 (1954). RECEIVED for review July 15, 1954. ACCEPTED November 4, 1984. Southern Regional Research Laboratory and the Naval Stores Research Section, laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture. Mention of the names of firms or trade products does not imply that they are endorsed or recommended by the U. 9. Department of Agriculture over other firms or similar products not mentioned.
Lactic Acid Purification by Extraction J
ROBERT B. WEISER' AND CHRISTIE J. GEANKOPLIS T h e Ohio State University, Columbus 10, Ohio
ISOAMYL ALCOHOL
.. .is
a good selective solvent for liquid-liquid extraction of crude lactic acid
. . .with steam distillation for solvent recovery offers some industrial possibilities for obtaining high purity lactic acid
A
CCORDING to Needle and Aries (14) the potential annual market for lactic acid is about 200,000,000 pounds if the price of the purer grades can be reduced significantly. Principal new markets would be for the manufacture of alkyd, acrylic, and other resins. Considerable recent work has been carried out to study methods of purification, which represent a considerable portion of lactic acid production costs. One method that has received attention and is currently used is the esterification of the acid in the crude solution and consequent separation of the ester (2,6-7). Liquid-liquid extraction has also been investigated as a possible purification method (11-13, 17-19). I n a patent, Waite (20) has discussed the extraction of the acid with amyl alcohol. Background information on the various purification methods and physical properties of lactic acid are also available ( 4 , 16, 21). Bass (1)reports that usual impurities in crude lactic acid solutions are alkaline earth metal salts, sugars, and volatile impurities such as acetic and butyric acids. The separation of lactic acid from these impurities is complicated by the formation of a self-polymer of lactic acid when the acid concentration rises above about 20%. Because liquid-liquid extraction seemed promising as a . purification method, this research investigation was 1 Present address, Polychemicals Department, E. I . du Pont de Nemours and Co., Inc., Wilmington, Del.
undertaken to determine the distribution of lactic acid and the various impurities between water and a wide variety of organic solvents under various operating conditions. Then, the best selective solvent was chosen, and the remaining processing problems were investigated to determine the potentialities of the extraction process. SOLVENT SEARCH
Materials and Analytical Methods. The lactic acid used for the majority of the tests was C.P. grade. A few tests were also run with the 22y0 technical grade of lactic acid. All the chemicals employed for analysis met ACS standards of purity. The organic solvents were used as obtained for the preliminary solvent search. Wherever possible, acid solutions were analyzed by colorimetric titration with standard base. When the concentration of lactic acid in water solution is above about 20% analysis, it is complicated by the presence of a self-polymer of lactic acid (3, 10). I n this case, excess base was added t o the solution and the mixture was heated for about 10 minutes in a boiling water bath. During this time the flask was stoppered, but a fine drawn-out tube cut down carbon dioxide absorption from the air. The excess base was then immediately back-titrated with standard sulfuric acid. This method was accurate within f0.2%. The presence of inorganic salts had no effect on the analysis of the acid, For analysis of acid in the solvent layer, water was added so that the colored end point could easily be detected. I n every analysis of all types, blanks were determined. A semiautomatic titrimeter was used for acid-base analysis in colored solutions. The end point setting was between 7.0 and 7.8 pH for lactic acid solutions. The method of Friedemann and Graeser (8) was used when other acids were present in the lactic acid solution. I n this method lactic acid is oxidized to acetaldehyde, and the aldehyde is collected in bisulfite. The bound bisulfite is determined with standard iodine, and a measure of the lactic acid content is obtained. This method was accurate within &0.2y0when compared with knowns. This method will yield erroneous values in the presence of sugars. I n some cases the distribution coefficient of sugars alone between water and organic solvents was determined. Sugars were analyzed
INDUSTRIAL AND ENGINEERING CHEMISTRY
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859
Table I. Distribution Ratios of Lactic Acid between Water and Various Organic Solvents Cw = concn. of solute in mater phase, g./100 ml. Solvent n-Butyl alcohola
sec-Butyl alcohol (high soly.) Isobutyl alcoholn
n-Amyl alcoholQ
Isoamyl alcohola tert-Amyl alcohol
n-Hexyl alcohola 2-Octanol a n-Octyl alcohola (high visc.)
CyclohexanolD (high visc.) Phenola (high soly.) Benzyl alcohola (slow eettling) Methyl isopropyl ketone Methyl isobutyl ketonea
Methyl n-amyl ketonea Diethyl ketone Di-n-propyl ketone Ethyl n-butyl ketone Diisobutyl ketonea Cyclohexanonea Acetophenonea
Temp.,
c.
25.0 25.0 25.0 25.0 40.0 54.5 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 40.0 54.5 25.0 25.0 25.0 25.0 40.0 54.5 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 40.0 54.5 25.0 25.0 25.0 25.0 26.0 25.0 25.0
cw 1.80 3.12 6.40 9,57 3.48 3.37 3.19 1.88 3.28 6.92 10 20 2.20 4.37 8.17 12.04 4.28 1.72 3.42 6.39 9.54 3.47 3.48 4.79 5.15 5 21 14.68 5.14 5.09 3.95 11.06 3.60 4.27 12.00 4.69 2.71 5.40 10.05 15.05 5.37 5.33 5.59 5.04 5.74 5.73 5.87 3.86 5.46
Cs = concn. of solute in organic phase, g./lOO ml.
K 0.725 0.721 0.780 0.810 0.775 0.813 0.929 0.634 0.630 0.676 0.714 0.418 0.418 0.445 0.468 0.447 0.803 0.813 0.825 0.844 0.789 0.775 0.313 0.195 0.198 0.210 0.214 0,230 0.578 0.618 0.72 0.446 0.485 0.253 0.113 0.116 0.123 0.130 0.130 0.138 0.095 0.164 0.048 0.06 0.023 0.524 0.109
n-Propyl acetate n-Butyl acetatea 4-Methyl amyl acetate Ethyl propionate n-Butyl lactate" (hydrolyzes rapidly) Ethyl acetoacetatea (hydrolyzes rapidly) n-Butyl phosphate Ethyl ethera Isopropyl etherR
Hexane Cyclohexane Benzene Toluene Chloroform a Carbon tetrachloride o-Dichlorobenzene Furfurala Aniline Tri-n-butylamine Isophoronea Octylene glycol (high visc.) 2,5-Dimethyl furan Ethylene glycol monoethyl ether acetate (high soly.) Ethylene glycol dibutyl ether
cw
25.0 25.0 25.0 25.0 40.0 54.5 25.0 25.0 26.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 40.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0
2,82 5.03 9.32 14.23 5 31 5.74 5.43 5.45 5.83 5.55 4.26 11.90 4.47 3.19 5.16 5.78 16.21 5.80 5.97 5.85 6.02 5.22 5.69 5.86 5.87 5.98 5.16 5.16 5.94 5.16 5.85 5.97 5.18 4.64 5.33 4.68 4.27 12.04 4.20 5.87
25.0 25.0
4.03 5.82
K 0.289 0.259 0.286 0.264 0.304 0.388 0.114 0.107 0,039 0 10 0.569 0.636 0.27 0.907 0 092 0.028 0.029 0.029 0.009 0.026
