Ternary Liquid Systems 3-HEPTANOL-WATER-ACETIC ACID AND 3-HEPTANOLWATERETHYL ALCOHOL C . M. OUALLINE, JR., AND $1. V-4N WINKLE The University qf Texas, Austirc, Tex.
P
URE 3-heptanol has properties (5)t'hat niakt: it desirable as a solvent. It is readily available; it has ti rioriiial boiling poiiit of 156.2' C. and a freezing point of -70' C.; its vapor pressure a t 20' C. is 0.50 nmi. of mercury; and its spwi[ic gravity at 20/20° C. is 0.822. These properties suggest that 3-hep(anoi might be suitable as a solvent iri an aqueous system. T o investigate this possibility, liquid equilibria data were tleterininetl i n two coniinon aqueous systems.
I n the acetic acid system the ~ a t e r - r i c hporlioii of the I I ~ u L u ~ ~ I solubility curve was obtained by adding alternately 3-heptanol and acetic acid to a fixed amount of water. The 3-heptanol w m added until the mixture became turbid, indicating saturation, the acetic acid was added t o bring the niixture back into the single-phase region. The 3-hrptanol-rich portion of the rui vc
MATERIALS
The commercial grade 3-heptanol used in Lhis iiivestigatiou \vas supplied by the Carbide and Carbon Chemicals Co. 'Phis inaterial was not purified since it was desired to obtain data for the available commercial material. Thc 3-heptanol niet tlie follo\~ing specifications ( 2 ) : specific gravity 0.821 to 0.823 at 20;20° C., normal boiling range 152" t o 160" C., and the minirriuni purity 95.0 weight 3-heptanol. Thi. glavial nccltic. ariti used ha(i :L
_1
0
z
f + W 0
0-
SOLUBILITY DATA
t-
e-
TIE-LINE D A T A
W z
@-
CONJUGATE LINE
0
ESTIMATE0 PLAIT POINT
Ha: W
a 100
t-
I
w
2
0 0
- SOLUBILITY
DAlA
ONJUGATE LINE
Fi pure 2.
20
30
60 70 8 0 CENT WATER
50
40
WEIGhT
PER
90
100
ZA
Figure 1.
Water-Acetic A c i d - J - E I e p t ~ ~ ~ oS> l stem a~ 25"
30
40
c.
purity of 99.5% and the alcohol was absolute ethyl alcohol ol' reagent grade purity. The water used in the investigation was obtained from the laboratory distilled water bystem arid was boiled immediately before using in order to remove any rehitlutd carbon dioxide. PROCEDUHE
The method of Othnier, JThite, and Trueger ( 6 ) was usrd in the evaluation of the equilibrium data for both systems. A11 equilibrium data and solubility data were determined at 25" C. in a water bath maintained at this constarit ternpe~aturr.
50
60
70
80
90
100
GENT W A T E R
Wa ter-E thy1 Alcohol-3- H e p tanol S y s t e m at 25" C.
obtaiiied i n ti siinilai, iiianiiw. T o obtain the tie-hie da(a, niivtures uf the t h e e coriiponerit>swere brought to coilstant tell)perature, shaken vigorously iri a separatory fuiinel, arid tlie two liquid phases allowed to settle out. The layers were then separated arid the acid concentration of each was determilied by titriltioii with a sodium hydroxide solution. A material balance 011 acetic acid was made for a11 I ie-hie points in order to check the possibility of esterification. Yo evitlerice of reactiori was ohtairied. Points on the mutual solubility c u r v ~ of : the ethyl a11:ohoI syytein were obtained by adding portions of the third coinpo~ie~it, to LL solutio11 of ethyl alcohol in either water or :3-lieptaiiol uiitil a turbid condition was reached. The refractive irides of the resultant satJurated phase was then obtained ait 35" C . to (siisiiri? a clear solution. Tie-line data were ohtained by I)i,iriging two liquid phases into equilibrium in the same nianrit!~. t~ i r i tlie acetic arid system. The refmotive index of eacli layer was detorniiried. Sinre the refractive indices of thc niisturt,s represerltirig compositions along the saturation curve \vcr'c previously tlcterinineii, these data enabled location of the conipositioiis of thtt equilibrium phases (extremities of the tie-lines). 111all cams the point representing the over-all composition for each eyuilibriurii determination should lie on the straight line connecting the equilibrium compositions. This serves as a check on the data.
>vas
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20
W E I G H T PER ZA
STIMATED R A I T WlNT
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TABLE I. EQUILIBRIUM DATAFOR 3-HEPTANOL-WATERACETICACIDSYSTEMAT 25" C. Water, Wt. %
Aoetic Acid, Wt. %
3-Heptanol, Wt. %
0
3.5 8.6 13.9 19.3 24.4 29.6 30.7 34.3 34.7 41.4 44.0 45.8 46.5 47.4 47.5 48.5 47.5 42.7 36.7 29.3 24.5 19.6 14.9 10.3 7.1 5.4 0.0
WEIGHT PER CENT SOLUTE IN HEPTANOL-3-RICH PHASE ZCR
Figure 3.
TIE-LINE: DATAAT 25O C. Acetic Acid in Water Layer, Acetic Aoid in 3-Heptanol Layer, Wt. % Wt. %
Distribution Diagram
The equilibrium data for the 3-heptanol-water-acetic acid system are presented in Table I and shown graphically in Figure 1. The equilibrium d a t a for the 3-heptanol-water-ethyl alcohol system are given in Table I1 and presented graphically in Figure 2. Figure 3 illustrates the distribution of solute between the 3heptanol-rich and water-rich phases for the two systems. The selectivity of 3-heptanol for ethyl alcohol and acetic acid in aqueous solution is shown in Figure 4. Selectivity is a coefficient of solvent performance defined as the ratio of solute concentration in t h e extract layer t o solute concentration in t h e rafEnate layer times the ratio of diluent in the r a f i a t e layer t o the diluent in the extract layer. This is eupressed by
TABLE11.
EQUILIBRIUM
DATAFOR 3-HEPT.iNOL-wATER-
ETHYL ALCOHOL SYSTEMAT 25' C.
Water, Wt. %
Ethyl Alcohol, Wt. %
3-Heptanol, wt. %
@ =SA XCAXAB 22 20
18
ro I -
T I ~ - L I N DBA T A AT 25' c. Ethyl Alcohol in Water Ethyl Alcohol in 3-HepLayer, Wt. % tanol Layer, Wt. % 6.0 11.0 16.2 20.3 24.5 29.1 33.7 37.0
16
0
z
2
14
a W
=LL
91
12
0 >. 10
t
it3 W -I
%
6
4
2 ' 0
5
IO
15
20
25
30
35
40
45
50
where 6 = selectivity of solvent for solute; XCB = weight concentration of solute in extract layer; XAA = weight concentration of diluent in raffinate layer; ZCA = weight concentration of solute in raffinate layer; and X A B = weight concentration of diluent in extract layer. In order to provide a means for smoothing and interpolation of tie-line data, the data were analyzed by the methods of Othmer and Tobias (6),Bachman ( I ) , and Hand ( 4 ) . The method of Othmer and Tobias and the method of Hand gave smooth curves which are substantially linear over the complete range. The plot resulting from use of the Bachman method showed greater
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curvature than those plots resulting from the other methods. The ethyl alcohol curve was linear except in the region of low ethyl alcohol concentration.
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Vol. 44, No. 1’
The composition of the plait point for the acetic acid system was estimated by extension of the conjugate line t o be 29.4% water, 46.6% acetic acid, and 24.0% 3-heptanol. The composition of the plait point for the ethyl alcohol system was estimated by extension of the Othmer-Tobias type of plot of the data and found to be 41.6% vater, 39.5yo rthyl alcohol, and 18.9% 3heptanol. It is concluded that 3-heptanol could be used as a solvent for the extraction of ethyl alcohol or acetic acid from aqueous solution if a suitable means can be found to recover the solvent. This may present difficulty in the case of acetic acid since esterification may take place a t elevated temperatures.
- Wt. 7a 3-Heptanol in 3-Heptanol-Rich Phase Wt. Yo 3-Heptanol i n 3-Heptanol-Rich Phase (1
Figure 5.
- XBB)/XBB
Othnier-Tobias Plot
The method of Othmer and Tobias consists of plotting (1 (1 - ZBB)/ZBB on a logarithmic plot, where N A A is the weight fraction water in the water-rich phase and X B B is the weight fraction 3-heptanol in the 3-heptanol-rich phase. This plot is shown in Figure 5. The plot derived from use of the Bachman method, Figure 6, was obtained by plotting the weight per cent 3-heptanol in the 3-heptanol-rich phme vs. t h e ratio of the weight per cent 3heptanol in t h e 3-heptanol-rich phase t o the weight per cent water in the water-rich phase. x A A ) / x ~ us.
Wt. 3’ % Solute in Water-Rich Phase Wt. % Water i n Water-Rich Phase XCA/%AA
Figure 7.
Hand Plot
ACKNOWLEDGMENT
The authors would like to acknowledge the cooperation of the Carbide and Carbon Chemicals Co. in furnishing the 3-heptanol used in this work. NOMENCLATURE
concentration, weight per cent p solvent selectivity A diluent B solvent C solute CB = solute in the solvent-rich phase
z
= = = = =
LITERATURE CITED
XBB/XAB
Figure 6.
Bachman Plot
Figure 7 shows the data plotted according t o the method proposed by Hand. This is a logarithmic plot of X ~ B / Z B B versus Z C A I X A A where XCB is the weight fraction solute in the 3-heptanolrich phase and X C A is the weight fraction solute in the water-rich phase.
(1) Baohman, I., IWD.ENG.C H E W ,~ A L ED., . 12, 38 (1940). (2) Carbide and Carbon Chemicals Co., New York, “Heptanol-3,” Specification 1-759-1. (3) Carbide and Carbon Chemicals Co., Kew York, “ T h e Physical Properties of Synthetic Organic Chemioals,” p. 2 , 1952. (4) H a n d , D. B., J . Phys. Chem., 34, 1961 (1930). (5) Othmer. D. F , and Tobias, P. E., IND.ENG.CHEM.,34, 690 (1942). (6) Othmer, D. F., White, R. E., and Trueger, E., Ibid., 33, 1240 (1941).
RECEIVED for review November 19, 1951 ACCEPTEDMarch 14. 1952. Abstracted from a thesis in partial fiilfillment of t h e degree of l I a s t r r of Science i n Chemical Engineering
