October 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
RESISTABCE TO SYNTHETIC LUBRICANTS
Synthetic lubricants based on esters of dicarboxylic acids are finding important uses in military vehicles and aircraft. As indicated in Table 111, quaternixed gasket stocks are substantially superior to the Paracril A stock in resistance to the two esters of this type which were inchded in this group of solvents. Subsequent tests with dihexyl azelate, diiso-octyl sebacate, diiso-octyl adipate, and dinonyl adipate have confirmed the fact that quaternized rubbers are resistant to these solvents.
2245
Data are presented in Table IV for gasket stocks exposed to diiso-octyl adipate a t 70' and 204' C. Although few compounding studies have been made in an effort to develop optimum compounding recipes for this particular application, the comparison of general purpose nitrile and quaternized stocks is revealing. When immersed in solvent a t 70" C., the nitrile stocks develop two to three times the volume swelling of the quaternized rubber and are generally inferior in stress-strain properties. After immersion in solvent at 204" C. the quaternized rubbers exhibit tensiles of as much as 870 pounds per square inch compared to 150 pounds per square inch or less for the nitrile stocks.
RESISTANCE TO PHOSPHATE ESTERS
Volume swelling tests in ethyl phosphate and diiso-octylphenyl phosphate (Table 111)reveal that quaternized stocks are superior to nitrile rubber in resistance to these solvents. Detailed tests on stocks immersed in a phosphate ester type of hydraulic fluid (Skydrol) show that the quaternized rubber exhibits tensile values of 1200 to 1300 pounds per square inch compared to 400 to 500 pounds per square inch for nitrile stocks. In addition, the volume swelling for quaternized rubber in this solvent is little more than a third that of the Paracril compounds.
LITERATURE CITED (1) Am. Soc. Testing Materials, Philadelphia, "ASTM Standards on Rubber Products," pp. 949-57, Test D 471-49T, April 1950. (2) Folz, J. M., Mahan, J. E., and White, D. H., Petroleum Proeessing, 7, 1802 (1952). (3) Svetlik, J. F., and Sperberg, L. R., India Rubber W o d d , 124, 182 (1951). RECEIVED for review January 28, 1954. ACCEPTEDJune 19, 1954. Presented a t the Regional Conclave of the Southeastern and Southwestern New Orleans, La., December 10 t o Sections, AMERICAN CHEMICAL SOCIETY, 12, 1953.
Liquid-Liquid Equilibria ACETIC ACID IN WATER, WITH 1-BUTANOL, METHYL ETHYL KETONE, FURFURAL, CYCLOHEXANOL, AND NITROMETHANE ADAM E. SKRZEC' AND NELSON F. -MURPHY Virginia Polytechnic Institute, Blacksburg, Vu.
F
OR investigations into the fundamental nature of the mechanism of material transfer between two liquid phases, it is desirable to have information on solubility of a number of systems with variable solubility and properties. The systems investigated in this study all contained acetic acid as the solute and water as one of the phase solvents. The second phase solvents were chosen so that there would be a difference in the mutual solubility, densities, and selectivities (6)of the components. These solvents were 1-butanol, nitromethane, furfural, cyclohexanol, and methyl ethyl keLone. Such data for solvents, acetic acid, and water have been presented by Othmer, White, and Trueger (3). MATERIALS
The 1-butanol used in this investigation was obtained from Commercial Solvents Corp., labeled technical grade, 99.5% as alcohol. The methyl ethyl ketone was distributed by Shell Chemical Corp., labeled as highest purity, 99% minimum ketone. The furfural was obtained from Quaker Oats Co., and marked purified, 99 to 100% as aldehyde. The cyclohexanol was from E. I. du Pont de Nemours & Co., Inc., purified, 100% as alcohol The nitromethane was from the Commercial Solvents Corp., technical grade, 99.5% as nitroparaffin. The acetic acid wed was from Fisher Scientific Co., glacial, c.P., 99.5 minimum
%. PROCEDURE
Various procedures have been proposed for determinationof the equilibrium data. The procedures adopted have followed recommended practices ( 3 ) . The values of the refractive indices of the mixtures are given because along with titration of the acetic acid, they serve as a convenient method of analysis for the system. Present address, Briatol Laboratories, Inc., Syracuse, N. Y.
DETERXINATION OF PHASE DI.4GRA&fS. To obtain the mutual solubility curves a t 26.7' C. for each of the five systems studied, the following procedure was adopted. Forty milliliters of the solvent were added from a buret to a glass-stoppered Erlenmeyer flask of 125-ml. capacity. Measured volumes of acetic acid were added dropwise to the solventsolute solution until the mixture became turbid and remained so for about 3 seconds. The flask was then stoppered and kept a t a constant temperature of 26.7" =!= 0.5" C. overnight. Drops of water were again added until the mixture became turbid and remained so for a t least 20 minutes. This procedure yielded data for the solvent side of the solubility or binodal curve. The procedure for obtaining data on the water side of the solubility curve consisted of adding the solvent to the mixture of water and acetic acid as described above. DETERMIXATION OF TIE LINES. The tie line data were obtained by preparing various mixtures of the three components within the area of the binodal curve and analyzing the solvent and water layers for acetic acid. Mixtures were placed in 125-ml. glass-stoppered Erlenmeyer flasks and shaken vigorously. The flasks were kept for a t least 12 hours a t a constant temperature of 26.7' C. Samples of the light and heavy layers mere pipetted from the flasks into another set of glass-stoppered flasks and weighed. Each layer was then diluted with water and titrated with sodium hydroxide using phenolphthalein as indicator. Titrations of the two layers in the furfural-acetic acid-water system were performed using methyl red indicator because of the difficulty in detecting the color end point with phenolphthalein.
As a check on the titrations of the solvent layer, which is insoluble in water, it was found that the same end point was obtained when sufficient ethyl alcohol was added to make the two phases completely miscible during titration. DETERMINATION OF REFRACTIVE IXDICES OF KNOWN COMPOSITION. Mixtures of known composition were prepared by addition of the second component to a known weight of the initial pure component contained in a weighed, stoppered weighing
INDUSTRIAL AND ENGINEERING CHEMISTRY
2240
/
25 X
CYCLOHEXANOL
5 IO 15 20 25 PER CENT A C E T I C A C I D I N WATER PHASE X u
Figure 1. Distribution Diagrams for Acetic Acid at 27" C. bottle, obtaining the weights of materials added by difference in initial and final weights, and computing the composition of the resulting mixture of liquids on a weight basis. Tap Rater was used for preparing the solutions, because this water was to be used later for extiaction operations. The refractive index of this tap water varied somewhat from month to month (1.3319 to 3.3326 at 26' '2.;. Corrections can be made for the use of the data with tap water of other refractive indices by shifting the refractive index curves proportional to the water content. The temperature coefficient of the refractive index for pure water at 25" i 3" C. is: =
0.000112
where I = refractive index for the D line and 7' = temperature in C. The refractive indices were measured at a controlled temperature, by means of a Zeiss-Abbe iefractometer. The procedure follou ed mas that recommended by A4STlItest D 445-465T. Experimental data for the various systems were plotted on a large scale and the data are summarized for Table I, by reading values from the curve a t the corresponding weight fraction of water.
O F SOLVEXTS USED AND REFRXTIVE I. DEESITIES ISDICES O F SOLLTIOXS OF T-ARIOUS SOLVESTS IN RATER
TkBLE
Sol-ent 1-Butanol Vieight
Fraction
27
0.00 0.01 0.02
1.3957 1,3952 1.3949 1,3948 1.3937 1.3930 1.3919 1,3900
of Water
0.03
0.05 0.07 0.10 0.16 0.84 0.86 0.88 0.90 0.92 0.94 0.95 0.96 0.97 0.98 0.99 1.00
Cyclohexanol
KitroFuifural methane Temperature, C. 27 25.6 26.7 Refractive Indices
1,4600 1 4585 1.4572 1 4559 1 4531
1.5180 1,5177 1,5168 1.5156 1.5135
1.3816 1.3792 1.3787 1.3783
TABLE 11. EQUILIBRIKM DATAFOR SYSTEMS AT 26.70" C Mutual Solubility, 1-Butanol-Tater-Acetic Acid, Wt. % 1-Butanol Acetic acid Water 7 30 0.00 92.70 3.15 7.13 moo 86.50 5 46 8.04 14 25 12.75 73,00 15.20 13.10 71.70 30 90 54.no lZ.10 49.35 14.15 36.60 56.16 31 .TO 12 14 60.82 6.02 24.16 0.00 79. SO 20.50 Estimated Plait Point 27.5 14.9 57.5 Tie Line Data __Acetic acid in 1-Butanol layer, Acetic acid in wator layer, 57 t . 7 , wt. yo 1.42 0.88 2.50 1.82 3.G8 2.63 4.90 3.64 6.04 4.37 8 49 6.35 10.70 8.20 15.00 i2.on
Y E T r l L LTWYL KETONE
dl dT
Vol. 46,No. 10
Methyl ethyl ketone
25.6 1.3762 1.3764 1.A765 1,3766 1,3789 1.3771 1.3775
?iIurual Solubility, Cyclohexanol-Water-Acetic Acid,___ Wt. % _ __
Cyclohexanol 3.60 3.97 5 01 5.58 7.00 12.00 19.70 39.00 41 00 58.50 75.50 82.30 86.00
30.7
Water
Acetic acid 0.00
96.4
2.83 6.79 13,02 14,30 20.73 23.40 24.10 23.80
93 2 88.2 81.4 78.7 67.25 56.90 36.90 35.20
19.60
25,OO 16.78 13.95 11.00
7.72 3.75 0.00
Estimated Plait Point 252-
43.8
~ - _ _ _
Tie Line Data Acetic acid in cyclohexano! layer, Acetic acid in water layer, Wt. yo wt. % 2.81 2.12 10.40 8.35 11.40 9.65 11.30 13.10 (20.1) 20.50 22.80 23.20 N u t u a l Soluhility, Furfural-\Vater-.lcetic ___Acid, W t "$ Acetic acid Watei 0.00 91.5 8.50 10.05 5.15 84.8 14.38 75.2 10.44 l5,G?J 28.00 58.3 31.50 51.5 17.00 16.55 42.60 40.8 23.4 14.20 62.40 11.20 16.8 72.00 14.15 Z.85 78.00 9.20 s a . 00 85.80 5.50 94,50 0.00
Furiulal
Estimated Plait Point ____ 40.4 17 0 Tie Line D a t a Acetic acid in water layer, Acetic acid in furfural layer, Wt. % wt. yG 1.86 2.36 4.18 3.48 6.50 5.72 8.50 7.72 10.20 8.90 12.25 ii.on 11.80 12.80
42.5
(Continued on p a g e 8247
1.3469
1.3432 1.3436 1.3415 1.3387 1.3380 1,3371 1,3362 1.3353
1 ,3145 1.3369 1.3360 1,3425 1.3367 1.3399 1.3352 1.3344 1,3359 1.3385 1.3344 1.3335 1.3347 1.3365 1.3337 1.3344 1.3327 1.3336 1.3346 1.3331 1.3335 1.3319 1 3333 1.3325 1,3323 1.3325 Specific Gravity of Pure Solrent at 20' C. n.8109 0.9493 1.160 1.139 0.8045
EXPERIBIENTA L RESULTS
The experimental data on equilibrium and mutual solubility for the systems are given in Table 11. The data Lvere correlated and the plait point was determined by the method of Treybal, Keber, and Daley ( 7 ) . The distribution diagrams, Figure 1, indicate the range of curves for the systems chosen. Sone of the systems exhibit solutropy _ .( 4 ) . Furfural and nitromethane favor the higher conceritrntion in the water phase.
October 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
Let the distribution' coefficient for acetic acid between solvent and water be
TABLE I1 (Continued) Mutual Solubility, Methyl Ethyl Ketone-Water-Acetic Acid, W t . % Methyl ethyl ketone Acetic acid Water 76.0 0.00 24.0 68.8 2.20 29.0 60.2 4.30 35.5 38.0 5.30 56.7 20.1 4.00 75.9 12.5 0.00 87.5 Estimated Plait Point 45.6 4.81 49.6 Tie Line Data Acetic acid in water layer, Acetic acid in methyl ethyl ketone, wt. % wt. % 1.53 2.29 2.43 3.15 2.85 3.90 3.08 4.21 1.41 1.78 0.82 1.00 Mutual Solubility, Xitromethane-Water-Acetic h'itromethane Acetic acid 0.00 9.60 12.60 5.40 11.7 14.30 19.4 18.20 22.3 21.7 24.6 25.4 25.9 37.8 25.5 44.2 23.8 51.6 2 0.8 60.0 18.05 66.0 12.88 77.1 9.90 83.2 7.00 86.9 3.66 93.0 0.00 98.1 Estimated Plait Point 54.3 22.7 Tie Line Data dcetic Acetic acid in nitromethane, wt. 70 2.75 5.01 6.50 7.43 11.90
Acid, Wt. 3 Water 90.4 82.0 74.0 62 5 56 0 50.0 36.3 30.3 24.6 19.15 15.95 10.02 7 90 6.10 3.34 1.89
where
Mc = distribution coefficient for acetic acid between solvent, B, and water, A X C B = concentration of acetic acid in the solvent phase X C A = concentration of acetic acid in the water phase and let the distribution coefficient for water between the solvent layer and the water layer be =
&!A
XAB XAA ~
where
MA
distribution coefficient for xater between the solvent phase and the water phase X A B = concentration of water in the solvent phase X A A = concentration of water in the aqueous phase Then the selectivity ( 5 ) would be the ratio of the two distribution c*oefficients,or =
XCBXAA Me XCAXAB M A
where
p
= selectivity of the particular system
Since
XG ,YAB
23.0
= ratio
of acid to water in the solvent phase on it. solvent-free basis
and
acid in water, wt.
'WC = X C B
@=-=-
%
xs= ratio of acid to water in the nater phase on a solvent-free
6.74 11.40 14.15 16.30 20.60
XAA
basis
the selectivity is also the ratio of these two ratiop. If @ is greater than unity, enrichment is accomplished in the solvent phase. Likewise, if p is less than unity, water has been extracted away from the original acid-water feed and the raffinate will be more concentrated in acetic acid. Selectivities for the four systems have been plotted in Figure 2. None of the selectivity values approach that of isopropyl ether (J), which is shown on Figure 2 for comparison. Data on distribution of acetic acid between water and 1butanol have been reported by Archibald ( 1 )and Leonard, Peterson, and Johnson ( 8 ) . Archibald gives distribution of acetic acid between water and methyl ethyl ketone. Leonard and associates give distribution of acetic acid between water and furfural. The above-mentioned data are reported on a weight per volume basis, and have been converted (approximately) to a weight percentage basis for comparison with the present results. Taking into consideration the experimental error, previously published data are in fairly good agreement with those published here, Then plotted on a correlation chart as used by Treybal, Weber, and Daley ('7). Furfural is unstable in an acetic acid solution, and butanol would esterify with the acid, making practical use of these solvents unlikely.
METHYL ETUVL KETONE I - BUTANOL NITROYETHANB FURFURAL CVCLOHEXAM OL i80PROPlL n w E R
\
12
2247
LITERATURE CITED
(1) Archibald, R. C., J . Am. Chzm. SOC.,54, 3180 (1932). ( 2 ) Leonard, R. H., Peterson, W. H., a n d Johnson, M. J., IND.ENG.
CHEM.,40, 64 (1948). (3) Othmer, D. F., White, R. E., a n d Trueger, E., I b i d . , 33, 1240 (1941). Smith, A . S., I b i d . , 42, 1206 (1950). ( 5 ) Treybal, R. E., "Liquid Extraction," McGraw-Hill Book Co., 1951. (4)
0 0
4 0 I2 16 20 PER CENT ACETIC ACID INSOLVENT RICH PHASE. X,,.
Figure 2.
24
Selectivity of Solvents for Acetic Acid at 27" C;
pp. 7 0 , 86, New Y o r k ,
(6) I b i d . , p. 88. (7) Treybal, R. E., Weber, L. D., and Daley, J. F., IND.ENG.CHEM., 38,817 (1946).
RECEIVED for review November 24, 1953.
ACCEPTIED M a y 14, 1954.
