LIQUID-LIQUID EXTRACTION DATA TOLUENE AND ACETALDEHYDE SYSTEMS DONALD F. OTHMER AND PHILIP E. TOBIAS' Polytechnic Institute, Brooklyn, N. Y.
Following the methods of the previous would remain almost completely N T H E previous paper of this series (3), equilibrium with the solvent and change the paper (3), data were obtained and are preproperties of the solvent. This data were presented for sented for ternary systems involving acetadditional factor serves t o vary several systems in which acetic aldehyde, water, and several solvents greatly the action of a solvent in acid is present as the solute which have more or less utility in extracan extraction system. liquid. Bhatnagar and Ward tion and separation of aqueous acetaldeI n the present case the fourth ( 1 ) have, however, used anhyliquid, water, was added in very drous acetic acid as the solvent hyde solutions. A graphical method for small amounts t o ,minimize its in the extraction of aromatics readily applying the lever rule is developed, tendency to show up in the from straight-chain hydrocarwhich reduces the time required and indiluent a8 well as in the solvent bons in the purification of pecreases the accuracy of the application of troleum fractions, because of its phase. Because of the small the synthetic method of determining tie amount added and the tremenDreferential solubility for the rormer and substantial immiscilines. dous attraction of acetic acid for watep as compared to that bility with the latter. It was deof heptane, the solvent will be sired to determine the usefulness regarded as a single substance: 97 per cent acetic acid, of acetic acid as an extracting solvent for toluene made by the reforming of seven-carbon aliphatic hydrocarbons from the 98.1 per cent acetic acid, etc., where the difference between the indicated per cents and 100 represents the amount of excess seven-carbon aliphatic hydrocarbons which have subwater. The analytical method previously described was used stantially the same boiling points. Furthermore, it was desired to obtain solubility data on a series of different solvents to obtain the data of Tables I and 11,taken a t 23' C., which are plotted in Figure 1as mutual solubility curves for toluene, in relation to the separation of another low-boiling organic acetic acid of different strengths, and n-hept ane. liquid (acetaldehyde) from water, by the proposed method of If these solubility curves are regarded as traces of a surface Othmer and Trueger (2) for separating aqueous solutions of plotted within a triangular prism, having different acetic acid ethanol and acetone. percentages plotted along its axis, it will be seen that the Toluene Systems boundary surface is a part of a cone having its apex a t or below the end section representing 100 per cent acetic acid. It As representative of the seven-carbon aliphatic hydrocaris apparent that the immiscibility of solvent and diluent (hepbons, +heptane was used as the diluent or liquid in which the tane) is greatly increased by increasing amounts of water. toluene is regarded as being originally dissolved. Unlike the It would be necessary to balance the advantage of greater imless pure systems of Bhatnagar and Ward, anhydrous acetic acid is completely miscible with toluene and n-heptane at ordinary temperatures, so it cannot be used as a solvent for separating one from the other. Therefore a modification of Aceloldehyde the previous technique was used. To the system was added a fourth liquid, to promote mutual immiscibility. One with a much greater affinity for the solvent was selected, so that it
I
1
A
Present address, National Bureau of Standards, Washington, D. C
Toluene
FIQURE 1. MUTUALSOLUBILITY CURVESAND TIE LINESFOR TOLUENE, +HEPTANE,AND SOLVENTS CONSISTING OF ACETIC ACID WITH ADDEDAMOUNTSOF WATER,IN WEIGHTUNITS FIGURE2. MUTUALSOLUBILITY CURVESFOR SYSTEMSOF
Figures give the strength of acetic acid used as solvent, assuming no water in the heptane phase.
ACETALDEHYDE, WATER,AND SOLVENT, IN WEIGHTUNITS
690
INDUSTRIAL AND ENGINEERING CHEMISTRY
June, 1942
-97% Acetic aoid
AcidToluene
-98.170 Aoetic acid
n-Heptane
2-1 g W 3 0
AcidToluene
I
W
TABLE I. MUTUALSOLUBILITY OF ACETIC ACID-TOLUENE+HEPTANE n-Heptane
69 1
%
\
0.9
-3
0.8
Toluene Benzene n-Amyl Alcohol
-t-r
TABLE 11. DISTRIBUTION DATAFOR ACETIC ACID-TOLUENEWHEPTANE
--
97% Acid--98.1% Acetic acid n-Heptane Acetic aoid layer layer layer 7 Per cent toluene 0.5 1.2 12.0 8.3 19.0 5.3 14.2 27.0
Acetaldehyde Systems Substantially the method previously described was used for the determination of the ternary solubility curve for the systems involving acetaldehyde, water, and each of the solvents, benzene, toluene, furfural, and n-amyl alcohol, at the respective temperatures indicated, which were maintained by use of a constant-temperature bath. These data are given in Table 111and the curves are plotted in Figure 2. The tie lines, distribution curves and coefficients, and concentration data, are based on equilibrium between the coexisting phases; and these equilibrium data were determined by the synthetic method described in the first paper of this series (3) and by the graphical method described below. While exact analyses would appear to be desirable for the determination of phase compositions, it is often difficult or even impossible to devise means of chemical analysis for the several liquids involved; and physical methods also are not always possible. The synthetic meihod has been found to be reasonably accurate when carefully handled and was therefore used. These data are shown in Table IV and plotted in Figures 3 and 4.
O
FIGURE 4. EFFECTIVE CONCENTRATION IN SYSTEMS OF ACETALDEHYDE,WATER,AND SOLVENT, IN WEIGHT UNITS
7
2.0 7.1
miscibility against the several disadvantages attendant on the use of more dilute acid in specifying what concentration would be used for the acetic acid-water ratio in the solvent.
'5 0
c ~ ~ c H o IN+ WATER ~ ~ ~LAYER
Acidn-Heptane layer
I
Graphical Application of the Lever Rule The lever rule, as applied to ternary liquid mixtures having two conjugate phases, indicated by the extremities of a tie line, may be stated: The weights of the two conjugate phases will be in the inverse ratio of the line segments from the point on the tie line indicating the over-all composition to the intersections of the tie line with the ternary solubility curve. The converse is equally important and may be stated as follows: The line drawn through the point indicating the over-all composition, which intersects the ternary solubility curve so that segments between the composition point and the
TABLE111. MUTUALSOLUBILITY DATAFOR SYSTEMS WITH ACETALDEHYDE AND WATER 70in System:? AcetSolvent aldehyde Water Toluene as Solvent (17' C . ) 0.055 0.0 99.955 0.2 20.0 79.8 0.4 30.0 69.6 0.5 36.0 63.5 1.0 49.0 50.0
--Weight
2.0 5.0 4.9 7.7
55.8 60.0 63.6 67.2
42.2 35.0 31.5 25.1
10.8 12.9 16.7 24.7
69.1 70.2 70.9 68.2
20.1 16.9 12.4 7.1
42.0 58.3 79.8 99.960
55.2 40.3 20.0 0.0
2.8 1.4 0.2 0.045
n-Amyl Aloohol as Solvent (18O C . ) 2.64 0.0 94.40 3.5 5.2 91.3 4.2 10.2 85.6 5.3 17.3 77.4 6.0 21.7 72.3
Percent Acetoldehyde- Aqueous Phase
FIGURE 3. DISTRIBUTION OF ACETALDEHYDE BETWEEN WATERAND SOLVENT, IN WEIGHT UNITS
70in System:AcetSolvent aldehyde Water Furfural as Solvent (16' C . ) 7.0 5.2 87.8 8.4 10.2 81.4 9.7 20.2 70.1 11.0 26.8 62.2
--Weight
16.7 18.9 30.8 43.8
33.3 34.0 35.1 35.0
50.0 47.1 34.1 21.2
54.0 64.2 72.9 84.1 93.2
32.2 25.8 20.1 10.8 2.6
13.8 10.0 7.0 5.1 4.2
Benzene as Solvent (18O C.) 0.170 0.0 99.835 16.8 81.7 1.5 26.5 71.5 2.0 3.0 35.4 61.6 3.2 38.2 58.6 3.4 3.9 3.8 5.0
44.0 49.3 52.7 59.0
52.6 46.8 43.5 36.0
7.0 9.9 13.1 16.7
26.5 29.4 35.3 37.3
66.5 60.7 51.6 46.0
7.2 9.1 12.0 13.5
61.8 66.0 67.0
68.0
31.0 24.9 21.0 18.5
20.3 23.0 28.2 35.7
39.3 40.0 40.6 39.6
40.4 37.0 31.2 24.7
20.1 26.1 39.1 53.8
68.4 66.2 58.2 45.0
11.5 7.7 2.7 1.2
47.5 62.2 72.9 84.2
34.8 24.4 15.0 4.8
17.7 13.4 12.1 11.0
74.4 89.8 99.954
25.0 10.0 0.0
4
Mutual solubility of solvent and water from Seidell
(4).
0.6 0.2 0.050
INDUSTRIAL AND ENGINEERING CHEMISTRY
692
Vol. 34, No. 6
I n the example shown, the over-all composition of two-phase mixture on ternary diagram a t point 0 is 36.5 per cent solvent, 43 per cent diluent, and 20.5 per cent solute. There is 2.0 times as much of diluent phase as of solvent phase. A fine pin pierces the celluloid sheet (on top of t h e triangular graph), therefore, a t calibrated point 2.0 on t h e A B scale and point 0 on the graph beneath. The upper edge of a straight bar (solid black band) is placed against t h e needle. Sheet s,nd straight edge are rotated independently until parallel linea through A and B intersect the aolubility curve t o give a straight line between the intersections and point 0-i. e., line L O M , t h e required tie line. Point L indicates 14.8 per cent solute in the solvent layer and point M indicates 28.3 per cent solute in the diluent layer.
FIGURE5. GRAPHICAL APPLICATION OF LEVERRULEIN LOCATING TIE LINES ON THE TERNARY SOLUBILITY DIAGRAM, USINGRATIO OF WEIGHTS OF CONJUGATE PHASES
curve are in inverse ratio to the weights of the respective conjugate phases, will be the tie line (and, of course, the only tie line) through the point of given over-all composition. A rapid method for determining the line possessing the required ratio of its segments was developed and is indicated in Figure 5. Two parallel lines are drawn on a sheet of transparent paper or celluloid. Between these lines is drawn an oblique line AB. This line is then calibrated so that, for any point 0 on AB, the ratio of OA to OB may be read directly. Let distance A B = unity g = calibration value starting at A x = distance OA 1 - z = distance OB Then y = 2/(1 5)
corresponding to the observed ratio of the weights of the conjugate phases, and through the point on the ternary diagram on the sheet beneath, representing the composition of the mixture. Against the pin, and on top of the transparent sheet, is a straight edge; the transparent sheet and straight edge are independently rotated until an intersection of the solubility curve with line A , point 0, and m intersection of the solubility curve with line B are all on a straight line. Points L and M are the intersections of the solubility isotherm with the two parallel lines found in this manner. The line LOM will then be the required tie line. From the geometry of the figure (similar triangles) it is obvious that
-
O M= _
OL
Of more use in calibrating so that convenient intervals of y may be indicated, is the form: =
Y/(Y
+ 1)
In the usual cases the points near the middle of the line are the only ones used. The transparent sheet is placed upon the solubility diagram and a pin is stuck through A B a t the calibrated point,
OA OB
- weight of diluent phase - weight of solvent phase
Care must be taken, of course, that the required ratio of the segments of line A B is the inverse ratio of the amounts of the respective phases, and that the distance between the parallel lines is smaller than any tie line t o be determined. This distance, however, should not be so small that the intersections give angles which are too acute.
Aclsnowledgment Thanks are due A. Marsh of the McKinley Technical High DATAFOR SYSTEMS WITH ACETALDETABLEIV. DISTRIBUTION School, Washington, D. C., for assistance in the experimental HYDE AND WATER -Wt. Yo Acetaldehyde in:Water Toluene layers layer a 54.7 62.2 35.3 48.7 19.8 30.3 18.0 27.8 13.8 22.2 9.0 17.0 4.3 9.0 n-Amyl alcohol Water layers layere 12 8.4 23.3 14.8 a 1 7 O C. b 16" C. C 18' C.
-Wt. yo Acetaldehyde in:Furfural Water layer b layerb 14.3 14.8 21.2 24.2 18.3 20.3 Benzene layere
Water layer0
A 7
A 9
16:k 14.2 19.0
9.1 13.2 17.6
work.
Literature Cited (1) Bhatnagar, S. S., and Ward, P. J., IND.E m . CHEM.,31, 195
(1939). (2) Othmer, D. F., and Trueger, E., Trans. Am. Inst. Chem. Engre.,
37,597(1941). (3) Othmer, D. F., White, R . E., and Trueger, E., IND.ENO.CHEM., 33. 1240 (1941). (4) eldell, A.,'"Solubilities of Organic Compounds", 3rd ed., Vol.
11,New York, D. Van Noatrand Co., 1941.
PRESENTEDbefore the Division of Industrial and Engineering Chemistry CHEMICAL SOCIETY, Memphis, Tenn. a t the 103rd Meeting of the AMERICAN
