1558
INDUSTRIAL AND ENGINEERING CHEMISTRY
(4) Javitz, A. E., Elec. M f g . , 45 (August and September 1950). (5) Kaufman, H. S., and Aluthana, ill. S., J . Polgmer Sci., 6, No. 2, 251 (1951). (6) LIiller, W. T., Jr., Fager, E. W., and Griswold, P. H., J . Am. Chem. Soc., 72,705 (1950). (7) Miller, W. T., “Use of Perfluoro- and Chloroperfluoroolefinsin
the Synthesis of Fluorocarbon Materials,” Columbia Gniversity, S.A.N. Laboratories, Atomic Energy Commission, MDDC-1177(1946). (8) Plax Corp., “Polymerized Chlorotrifluoroethylene,” Atomic Energy Commission, MDDC-818(hlarch 27, 1947). (9) Reysen, W. H., and Vanstrum, P. R., “Properties of Fluoro-
Vol. 45, No. 7
thene,” Carbide & Carbon Chemicals Corp., Atomic Energy Commission, AECD-2032 (Sept. 22, 1948). (10) Thomas, C. A., “Anhydrous Aluminum Chloride in Organic Chemistry,” ACS Monograph 87, p. 68, New York, Reinhold Publishing Corp. 1941. (11) Watson, H. A , , Stark, N. J., Sieffert, L. E., and Berger, L. B., U. 8.Bur. Mines, R e p t . Invest. 4756 (December 1950). R E C E I V E D for review November 20, 1952. ACCEPTEDApril 8, 1953, Presented before the Division of Polymer Chemistry, Symposium on Chlorotrifluoroethylene, joint with Division of Industrial and Engineering Chemistry, a t the 122nd Meeting of the .4UERXCAN CHEXICAL SOCIETY, Atlantic City, N. J.
Dimethvlaniline as an Aid in Acetic Acid-Water Separation LEO GARWIN‘ AND PHILIP 0. HADDAD2 Oklahoma A . & M . College, Stillwater, Okla.
S
EPARATIOS of acetic acid and water is most frequently
carried out hy distillation. Difficulty is experienced, holvever, in the n-ater-rich region because of a low relative volatility. Many attempts have been made t o effect the separation more conveniently, using other types of separation processes, and some of these are practiced commercially. Examples are (11 ) azeotropic distillation with butyl acetate (Othmer process), liquid-liquid extraction, and extractive distillation with a wood oil (Suida process). K o r k has been carried out on the addition of an inorganic salt, calcium chloride, t o reverse the relative volatility of acetic acid and water ( 3 ) . The effect of high pressure on the acetic acid-water vapor-liquid equilibrium has recently received attention ( I O ) . The study reported in this paper was undertaken to investigate the addition t o acetic acid and water of a third component, intended t o improve the normal distillation by exerting a highsolvent action on the acetic acid, thus causing it to be retained in the bottoms stream, and by azeotroping with the water, causing it to come off overhead more readilk, h water-insoluble organic compound having basic properties seemed to be a logical choice, for it would be expected to form a loose complex with the acetic acid, and it would also form a heterogeneous azeotrope (minimum boiling) with water. Most nitrogen compounds were rejected because they form maximum boiling azeotropes Tvith acetic acid (7); this had to be avoided. Aniline has been reported to be satisfactory in this regard (8). Preliminary experiments showed, however, that it could not be used because of its reaction with acetic acid to form acetanilide. Dimethylaniline has been reported (8) as not forming an azeotrope u i t h acetic acid. It would be expected not to react with acetic acid because of the replacement of the t a o active hydrogens on the nitrogen nith methyl groups, and it was therefore selected for study. This report deals with the vapor-liquid equilibrium a t 1 atmosphere of the binary systems acetic acid-water, acetic acid-dimethylaniline, and the ternary system acetic acid-Tvater-dimethylaniline. Because dimethylaniline and water are mutually immiscible, the vapor-liquid equilibrium for this binary system can be readily calculated. The materials used and the analytical procedure employed have been described ( 2 ) . When a sample for analysis consisted of two liquid phases, the sample was brought to 25.0’ C., the conjugate layers were separated and weighed, the composition of each phase ’ Present address, Kerr-McGee Oil Industries, Inc., Oklahoma City, * Present address, Dow Chemical Co., Freeport, Tex.
Okla.
1%as determined by acetic acid titration and reference t o the ternary system solubility envelope (Z),and the composite composition of the mixture obtained by the lever arm principle, using a triangular plot.
EQUIPMENT AhD PROCEDURE
For all binary system runs and those ternary system runs in which both distillate and residue nere single phase, an Othmer still ( 8 ) was employed. Pressure was, maintained constant a t 760 k 1 mm. of mercury by mcans of a Greiner Cartesian manostat (4). 911 thermometers were checked in place by means of runs with distilled water and with pure dimethylaniline; temperatures were estimated to 0.1” C. Approximately 45 minutes were allowed for equilibrium. The distillate rate was 60 to 66 drops per minute. .4n extended run showed this amount of operating time under these conditions to be ample. Changes in the still pot composition from run to run were made by withdrawing part of the charge and replaring it with one of the pure components. A still described by Hands and Korman (6) vias used for those runs of the three-component system in nhich two phases appeared. The still v a s used also for a fe!\- single-phase runs. In its operation, the distillate, during equilibration, is returned directly to the still pot: there is no distillate holdup. The still is run until constant temperature is reached, and then a small amount of distillate (relative to the amount of residue) is withdrawn as a sample. It was found that 20 minutes running time was sufficient to reach a constant temperature; twice as much time was allowed for each run, however. The distillate sample volume was restricted to 1% or less of the residue volume. After the removal of the distillate sample, the still was allowed to continue to operate until a new temperature equilibrium was established. The changes in residue composition and temperature occasioned by the removal of the distillate sample were small, and
TABLE
I. COl\IPARrSOiX O F VAPOR-LIQUID EQUILIBRIUM STILLS (1 Atmosphere) -4cetic Acid-Water __ _ _
Hands and Korman still Othmer still
Water, Wt,. % Liquid Vapor 46 3 34 2 46 8 34 2
’
Acetic Acid-Dimethvlaniline _Aoet,ic Acid, Wt. % ’ Liquid Vapor 49 6 89 6 49 6 89 6 ~
INDUSTRIAL AND ENGINEERING CHEMISTRY
July 1953
FOR ACETICACIDTABLE11. VAPOR-LIQUIDEQUILIBRIUM
WATER
(1 Atmosphere) Experimental Data Temp.,
2.5 17.1 17.9 26.2 27.6 40.3 49.9 50.7 61.6 72.6 77.9 88.1 89.7 94.6
115.3 108.0 107.5 105.2 105.1 103.4 102.4 102.0 101.2 100.8 100.7 100.2 100.0 100.1 100.0
O
100.0 ~~
the Hands and Norman still on a binary system with a value for the same residue composition taken from a smooth curve representing Othmer still results on the same system. Two comparisons are made in Table I.
Smoothed D a t a
Water, Wt: % Liauid Vapor 1.5 9.9 10.4 17.1 18.6 28.0 37.0 38.0 49.9 62.8 70.4 84.1 86.2 92.8 100.0
1559
c.
Water, Wt. % Liquid Vapor 0.0 0.0 16.7 10.0 30.1 20.0 42.3 30.0 52.9 40.0 62.2 50.0 70.0 60.0 77.4 70.0 85.1 80.0 92.5 90.0 100 0 100.0
Tym
RESULTS
C.
118.1 107.9 104.7 103.2 102.1 101.3 100.9 100.7 100.2 100.1 100.0
All data are reported on a weight composition basis. The acetic acid-water vapor-liquid equilibrium results obtained with the Othmer still are shown in Table 11. They were checked with the data of several previous investigators ( I , 3, 6) and found to agree well. The data for the system acetic acid-dimethylaniline are presented in Table I11 and are plotted in Figure 1. As the curve roo,
I
I
I
I
~
TABLE 111. VAPOR-LIQUIDEQUILIBRIUM FOR ACETICACIDDIMETHYLANILINE (1 Atmosphere) Experimental Data Smoothed Data Acetic Aoid, Wt. % T ~ ~ ~ Acetic . , Acid, Wt. % Temp., Liquid Vapor O C Liquid Vapor OC 0.0 0.0 193.0 0.0 0.0 19.8 2.0 161.0 42.5 5.3 4.0 34.7 152.6 57.2 9.3 45.5 141.6 6 . 0 7 2 . 0 17.5 53.2 134.0 8.0 82.2 29.9 58.4 10.0 130.8 86.0 36.8 62.6 12.0 127.9 88.6 49.0 69.1 126.2 16.0 91.2 54.0 74.3 20.0 125.4 91.2 56.5 78.3 24.0 122.2 94.5 71.6 81.2 28.0 120.0 97.0 82.2 83.5 32.0 118.0 98.5 90.5 85.4 36.0 87.0 40.0 89.4 48.0 91.4 56.0 93.0 64.0 94.8 72.0 97.9 88.0 99.0 94.0 100.0 100.0
LINES OF CONSTANT
DIMETHYLANI
W
w
z J
&SOlY
I
pa
' 40.-
I
I
I
I
20
40 60 eo U T . 4 WATER I N L I Q U I D , DIMCTWYLANILINE-FREE BASIS
100
Figure 2. Vapor-Liquid Equilibrium for Acetic AcidWater-Dimethylaniline at 1 Atmosphere
UT.%
Figure 1. Vapor-Liquid Equilibrium for Acetic AcidDimethylaniline at 1 Atmosphere
a
a
V
average values are reported. Pressure was maintained constant a t 760 mm. It was desirable to check the two stills against one another. This was done by comparing an experimental point obtained with
WT.
f eo -
WATER
IN LIOUIO,
OIYETWILANILIWE- FREE 0bS1S
Figure 3. Dimethylaniline Concentration in Vapor Phase Ternary system at 1 atmosphere
INDUSTRIAL AND ENGINEERING CHEMISTRY
1560
TABLE117. Liquid Composition, Wt. 7% DimethvlWater aniline Acetic acid
VAPOR-LIQUID
Vol. 45, No. 7
EQUILIBRIUM FOR ACETIC A'k!ID-\~~~4TER-DIMETHYLANILIiVE
(Experimental data, 1 atmosphere) Vapor Composition, Wt. YO DimethylTemp., Kumber Of Phases ' C. Residue Distillate Acetic acid Water aniline
Stlll"
Dimethylaniline in Liquid, -4pproximately 10 U't. % 85.3 81.3 76.6 72.5 69.3 65.8 59.3 54.1 50.3 47.4 44.0 39.6 35.8 28.9 29.0 21.7 19.2 13.0 4.9
9.5 9.8 9.2 9.4 8.9 9.1 10.3 10.8 10.1 9.8 9.7 8.5 9.6 9.6 9.5 10.0 11.1 10.9 13.9
2.8 5.3 7.4 9.6 11.0 13.2 16.2 18.4 20.9 24.4 27.8 34.6 37.5 46.2 46.9 58.0 60.9 71.1 83.4
74.7 69.3 64.6 60.4 56.5 53.4 46.6 41.9 38.2 34.7 31.9 29.4 25.1 18.9 18.2 15.3 10.9 10.1 5.9 4.7
20.1 19.8 19.5 19.2 18.9 18.6 19.7 19.3 18.9 18.8 18.6 18.4 20.4 20.3 21.3 20.2 20.2 21.2 20.3 21.1
3.2 6.5 9.7 12.1 14.1 15.6 19.6 22.0 24.2 26.0 28.2 32.8 36.2 47.6 48.1 55.6 66 2 65.5 78.7 80.3
57.3 52.3 47.1 43.0 39.0 36.1 31.3 27.4 24.2 21.6 19.6 17.7 12.9 9.6 7.9 4.7
34.7 34.0 34.2 33.9 34.3 33.9 33.6 33.5 33.4 33.3 33.3 33.3 34.0 32.6 33.5 31.8
5,7 10.1 13.0 15.6 18.2 20.0 22.8 25.4 28.3 30.5 33.5 36.2 45.9 59.6 61.5 74.1
53.1 47.7 37.9 39.7 39.5 35.0 36.5 31.1 26.0 25.0 21.5 17.2 12.6 7.3
40.4 40.3 41.3 40.0 40.2 41.4 40.0 41.6 42.1 41.1 41.1 41.0 42.0 40.9
5.5 9.2 16.1 14.7 15.1 17.4 17.2 20.0 23.5 25.1 27.1 32.3 40.0 57.2
19.8 19.5 19.4 19.5 20.2 19.7 19.1 19.0 17.5 15.6 12.3 7 8 6.0 ,5 , 6 5.6 4.0 3.9 2 8 3.1
2 2 2 2 2 2 2 2 2 2 1 1 1 1 1
2 2 2 2 2 2 2 2 2 2 2
HN H I\i HN HN HN HN
1 1 1
0 0
1 1 1
1 1
1 1
1
1
HN
"
HS HN HN 0
0 0 0 0 0
94.2 89.0 84.4 80.0 76.1 72.4 66.1 60.6 55.9 52.6 48.5 43.3 39.6 32.0 32.0 23.1 20.5 14.7 5.7
Dimethylaniline in Liquid, Approximately 20 Wt. % 2 2 2 2 2 2 2 2 2 2 2
2 2 2 2 2 2 2 2
" HhHs HS
HN
1
2 2 2
1
1
H 1-
2
1
1 1 1 1 1 1 1
Dimethylaniline in Liquid, ilpproximately 30 Wt.
1 1 1 1 1 1
HN HN RN r3 N
"
" " " 0 HN HN 0 HN 0
93.5 86.4 80.3 74.7 69.7 65.6 58.0 51.7 47.1 42.7 39.1 36.1 31.7 23.7 23.0 19.1 13.7 14.0 7.5 6.0
70 2 2 2
2 2 2 2 2
2 2 2 2 1 1
1
1
HN Hs HN HIY H 1HN HN
"
HS HN HX
H \-
0 0 0 0
88.5 79.1 71.7 65.2 59.5 54.7 47.3 41.3 36.5 33,5 29.4 26.6 19.5 12.6 11.8 7.0
Dimethylaniline in Liquid, .4pproximately 40 Wt. % 2 2 2 2 2 2 2 2 2 2 2 2 1 1
9
2 2 2
2 2 2 2 2 2 9
2
1 1
IIx
HN H hH 1HN HN HN
" "
HN HN HN HY H S
89 0 80 0 64 5 66.2 66 1 59 7 60 9 46.5 44.8 42.4 36.4 29 2 21.8 12.5
Dimethylaniline in Liquid, Approximately 50 Wt. 7% 50.1 45.8 4.1 50.0 41.3 8.7 50.0 37.5 12.5 34.2 49.9 15.9 50.0 31.5 18.5 50.9 30.3 18.8 29.2 50.8 20.0 2 9 . 1 4 9.9 21 .o 50.7 27.9 21.4 2 6 . 4 5 0.4 23 2 24.7 50.3 25.0 22.5 5 0.2 27.3 50.1 19.9 30 0 50.2 15.9 33.9 50.0 13.7 36.3 11.1 49.8 39.1 49.6 8.2 42.2 49.4 4.7 45.9 a H N = Hands and Norman still; 0 =
4.3 8.8 12.1 14.8 17.1 17.0 18.3 19.2 19.4 20.7 22.5 24.3 25.3 29.5 31.9 35.3 44.6 58.4 Othmer wtill.
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
1 1
HN HN HN HN HN
H h" "
HN HN HN HN
" HN
" HN
" HN
91.8 82.6 74.9 68.3 62.9 61.8 59.3 58.1 56.5 53.1 49.7 46.2 39.8 31.9 27.4 22.1 16.2 9.2
INDUSTRIAL AND ENGINEERING CHEMISTRY
July 1953
1561
TABLE IV. VAPOR-LIQUID EQUILIBRIUM FOR ACETICACID-WATER-DIMETHYLANILINE (Contd.) Liquid Composition, Wt. % DimethylAcetic acid Water aniline
(Experimental data, 1 atmosphere) Vapor Composition, Wt. % DimethylT ~ ~ ~ Number . , of Phases Acetic acid Water aniline " C. Residue Distillate
* 2.9 5.5 7.8 9.8 11.4 13.0 15.3 16.2 17.4 18.7 20.6 22.5 23.0 24.2 25.1 26.4 27.5
.
27.7 25.2 23.0 21.1 19.5 18.0 19.6 18.0 16.1 14.2 12.2 9.1 7.9 6.6 5.2 3.7 2.1
69.4 69.3 69.2 69.1 69.1 69.0 65.1 65.8 66.5 67.1 67.2 68.4 69.1 69.2 69.7 69.9 70.4
90 1 9.2 0.68 89 8 8.9 1.31 89 7 8.4 1.94 89 4 8.0 2.58 89 6 7.1 3.32 88 8 7.2 4.02 88 4 6.77 4.8 88 6 5.50 5.9 89 2 4.83 6.0 4 10 89 6 6.3 89 7 3 50 6.8 89 8 2 76 7.4 90 1 2 03 7.9 90 3 1 53 8.2 89 2 1 72 9.1 90 2 1 25 8.5 89 4 1 35 9.2 90 2 0 82 9.0 89 6 0 95 9.4 89 7 0 70 9.6 89 7 0 64 9.7 0 40 89 8 9.8 0 H N = Hands and Norman still.
4.1 7.7 10.1 12.5 14.1 16.0 16.6 18.0 19.5 21.7 23.1 27.1 28.5 32.0 35.9 44.6 58.0
Dimethylaniline in Liquid, Approximately 70 Wt. % 2 74.7 21.2 98.3 2 98.7 72.8 19.5 2 70.2 19.7 99.1 2 99.5 68.5 19.0 2 99.6 65.6 20.1 2 99.7 63.9 20.1 61.0 19.6 2 99.7 99.9 2 61.9 20.1 2 61.0 19.5 99.9 2 59.6 18.7 100.0 57.2 19.7 100.5 2 101.0 2 54.6 18.3 2 53.3 18.2 101.4 101.9 2 51.0 17.0 47.7 16.4 1 102.8 105.0 40.2 15.2 1 111.1 27.4 14.6 1
2.0 3.8 5.9 7.7 9 1 10.8 12.0 13.5 14.2 15.1 16.0 20.7 23.9 27.9 30.3 32.2 34.0 40.8 42.8 50.5 51.0 58.3
Dimethylaniline 74.8 73.7 72.6 72.8 69.9 67.3 68.0 66.0 65.6 64.1 62.5 59.3 54.7 52.0 49.6 46.3 47.3 36.4 35.6 24.0 21.5 14.2
in Liquid, Approximately 90 Wt. % 2 23.2 98.1 2 22.5 98.1 2 21.5 98.2 2 19.5 98.5 2 21.0 98.8 2 21.9 99.2 2 20.0 99.3 2 20.5 99.3 2 20.2 99.3 2 20.8 99.5 2 20.5 99.8 2 20.0 100.8 2 102.1 21.4 2 20.1 104.4 2 20.1 102.6 2 21.6 106.4 2 18.7 105.1 1 22.8 111.7 2 21.6 112.6 1 25.5 Tl9.0 1 27.5 121.6 1 27.5 127.0
shows, the separation of these two components is very readily accomplished. There is no azeotrope formation. The experimental ternary system data are summarized in Table IV. The table includes information on the still employed and the number of phases appearing in both residue and distillate. The data were plotted and smoothed graphically. The smoothed results are summarized in Tables V, VI, and VII. Figur'e 2 shows a series of vapor composition versus liquid com-
Stilla
Water (DimethylanilineFree Basis), W t . % Liquid Vapor
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 1
90.2 81.8 74.6 68.4 63.1 58.2 56.3 52.5 48.2 43.3 37.8 28.7 25.4 21.5 17.3 12.5 7.0
94.9 90.5 87.5 84.5 82.0 80.0 79.4 77.4 75.8 73.5 71.4 66.9 65.1 61.5 56.8 47.1 32.1
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 1 1
93.2 87.0 81.2 75.7 68.1 64.1 58.5 48.3 44.6 39.4 34.0 27.2 20.4 15.7 15.9 12.8 12.8 8.4 9.2 6.8 6.2 3.9
97.5 95.1 92.5 90.5 88.5 86.3 85.0 83.0 82.3 81.0 78.5 74.1 69.6 65.1 62.0 59.0 58.3 47.1 45.5 32 2 29 6 19.6
position curves. The parameter is weight per cent dimethylaniline in the liquid phase. The same parameter is used in Figure 3, in which the dimethylaniline content of the vapor phase is plotted against liquid composition. I n Figures 2 and 3 there has been drawn a dashed line which separates the single- and double-phase liquid regions. The location of this line is approximate. All liquid compositions below the line are single phase at the distillation temperature. Those above are double phase. Such a line for a constant temperature of 25' C. can be drawn from available ternary system data a t this
TABLEV. VAPOR-LIQUIDEQUILIBRIUM FOR ACETIC ACIDWATER-DIMETHYLANILINE (Smoothed data, 1 atmosphere) Water in Vapor, Wt. %" Dimethylaniline in Liquid, Wt. % Water in Liquid, Wt. 70" 0 10 20 30 40 50 70 9 . 8 1 1 . 0 1 2 . 2 13.6 1 6 . 0 1 8 . 6 7.4 4.0 1 7 . 6 1 9 . 3 2 1 . 8 2 9 . 6 3 3.8 2 4 . 6 1 3 . 6 8.0 1 9 . 6 2 4 . 0 2 7 . 4 3 0 . 4 3 4 . 8 40.2 45.4 12.0 2 5 . 0 3 0 . 0 34.2 38 0 43.2 48.4 5 4 . 3 16.0 3 0 . 1 35.4 40.8 4 5 . 8 50.2 54.7 6 0 . 1 20.0 35 1 4 0 . 7 4 7 . 6 5 9 . 2 5 5 . 7 5 9 . 3 64.1 24.0 40 0 4 6 . 1 5 3 . 3 5 7 . 5 60.2 62.6 67.0 28.0 44.4 51.2 5 8 . 6 6 1 . 6 6 3 . 3 6 5 . 0 69.2 32.0 4 8 . 8 55.9 63.1 64.9 6 6 . 0 6 7 . 1 71.2 36.0 52.9 6 0 . 3 6 6 . 4 6 7 . 5 6 8 . 5 6 9 . 1 72.9 40.0 5 6 . 7 6 4 . 2 6 9 . 0 69.9 7 0 . 7 70.9 7 4 . 5 44.0 60 4 6 7 . 5 7 1 . 3 71 1 71.7 71.7 76.1 48.0 6 3 . 9 7 0 . 6 7 3 . 3 74 1 7 4 . 2 74.2 7 7 . 6 52.0 6 7 . 0 7 3 . 4 75.3 7 5 . 9 75.9 75.9 79.1 56.0 70.0 7 6 . 2 7 7 . 4 7 7 . 7 77.7 77.7 8 0 . 8 60.0 72.9 7 8 . 8 7 9 . 5 7 9 . 7 7 9 . 7 79.7 8 2 . 6 64.0 7 5 . 9 8 1 . 3 8 1 . 7 8 1 . 8 8 1 . 8 8 1 . 8 84.3 68.0 79.1 83.7 8 3 . 9 8 3 . 9 83.9 83.9 86.2 72.0 8 2 . 0 8 6 . 2 8 6 . 3 8 6 . 3 86.3 86.3 88.0 76.0 85.1 88.4 88.4 88.4 88.4 88.4 90.0 80.0 88.1 90.7 9 0 . 7 9 0 . 7 90.7 90.7 9 1 . 9 84.0 9 1 . 0 9 3 . 0 9 3 . 0 93.0 93.0 9 3 . 0 9 3 . 8 88.0 9 4 . 2 95.3 9 5 . 3 95.3 95.3 9 5 . 3 s 5 . 9 92.0 9 7 . 1 97.4 9 7 . 4 97.4 97.4 97.4 9 7 . 9 96.0 a Dimethylaniline-free basis.
TABLE VI.
___
90 20.6 40.6 56.4 65.2 70.3 73.5 75 9 77.9 79.5 80.4 81.9 82 9 83.8 84.6 85.3 86.4 87.6 89.0 90.4 91.9 93.4 95.0 96.7 98 4
Water in Liquid, Wt. % a
. o
BOILING POINTS OF ACETICACID-WATERDIMETHYLANILINE (Smoothed data, 1 atmosphere) Temperature, C. Dimethylaniline in Liquid, Wt. % 0 10 20 30 40 50 70
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 Dimethylaniline-free basis.
90
INDUSTRIAL AND E N G I N E E R I N G C H E M I S T R Y
1562
TABLE VII. DIMETHYLANILISE VAPOR COXCEXTRATIONS FOR ACETIC~CID-\~r~4TER-DI>lETHYLANILIh’E
Water in Liquid, Wt. %“
Q
(Smoothed data, 1 atmosphere) Dimethylaniline in Vapor, Wt. c/o Dimethylaniline in Liquid, Wt. % 10 20 30 50 70 3.5 5.5 10.3 22.0 4.2 6.8 15.0 9.6 5.4 8.3 14.9 10.1 9.8 6.7 12.7 16.0 8.4 11.5 17.1 14 8 18.0 10.3 13.3 16.6 12.3 15.3 17.9 18.8 17.2 14.7 18.7 19.5 17.2 19.2 18.8 19.9 19.1 19.5 19.5 19.9 19.5 19 5 19.5 20.0 19.6 19.6 20.0 19.6 19.6 19.6 20.0 19.6 19.7 19.7 20.0 19.7 19.7 19.7 19.7 20.1 19.8 20.2 19.8 19.8 19.8 19.8 20.3 19.8 19.9 19.9 20.4 19.9 20.0 20.0 20.6 20 0
BO 42.5 27.5 22.8 20.7 20.0 19.9 19.9 19.8 19.9 19.9 20.1 20.2 20.5 20.8 21.1 21.5 21.9 22.3 22.8
Dimethylaniline-free basis.
temperature (g), and interpolation can be emploged for intermediate temperatures. DISCUSSION
Figure 2 shows that the addition of dimethylaniline produces the expected effect-aiding the separation of acetic acid and water by increasing the water-acetic acid relative volatility. There is a marked effect on the volatility a t the lowest dimethylaniline concentration studied (10 weight yo in the liquid phase). This improvement occurs also at the water-rich end, where it is most needed. Further increase in dimethylaniline content t o about 50
Vol. 45, No. 7
weight % in the liquid continues to produce a steady improvement in the acid-rich end, but practically no additional change in the water-rich region. It is only a t concentrations of 70 to 90 weight % dimethylaniline that further significant effect is obtained in the water-rich region. It would appear from the data obtained that dimethylaniline in relatively smallquantities could be used as an aid in the separation of acetic acid and water by distillation. Further work on a continuously operated distillation column, using dimethylaniline as a combined extractive-azeotropic agent, would be desirable in order to check on factors of importance in a commercial installation (capacity, efficiency, corrosion, etc.). The results of such studies would provide a basis for a thorough economic evaluation of the separation process. LITERATURE CITED
(1) Cornell, L. W., and JIontonna, R. E., IND. ENG.CHEM.,25,1331 (1933). (2) Garwin, L., and Haddad, P. O., Anal. Chem., 25, 435 (1953). (3) Garwin, L., and Hutchison, K. E., IND.ESG. CHEX, 42, 727 (1950). (4) Gilmont, R., A n d . Chem., 23, 157 (1951). (5) Gilmont, R . , and Othmer, D. F., IND.ESG. CHEM.,36, 1061 (1944). (6) Hands, C. H. G., and Xorman, W-.S.,Trans. I n s t . Chem. Engrs. (London),23, 76 (1945). (7) Horsley, L. H., Anal. Chem., 19, 508 (1947). (8) LBcat, M., “L’AaBotropisme,”Brussels, Lamartin, 1918. (9) Othmer, D. F., Anal. Chem., 20, 763 (1948). (10) Othmer, D. F., Silvis, S. J., and Spiel, A., ISD.ERG.CHEM., 44, 1864 (1952). (11) Shreve, R. N., “Chemical Process Industries,” pp. 682-8. S e w York, hlcGraw-Hill Book Co., 1945. RECEIVEDfor review September 29, 1952. ACCEPTED March 10, 1953. Presented before the Division of Industrial and Engineering Chemistry at the 123rd Meeting of the AMERICAN CHEMICAL SOCIETY, Los Angeles. Calif.
Equilibrium in the Steam Reforming of Natural Gas H. A. DIRKSEN -4ND C. H. RIESZl Institute of Gas Technology, Chicago, ZZl. I T H the advent of natural gas to new and expanded markets, catalytic steam reforming of natural gas has assumed an exceptionally important role in gas manufacture. As part of a broad research program, an exploratory evaluation of carriers and promoters for nickel catalysts was made. in which some 180 tests were completed ( 3 , 4). These results could be compared accurately and on a consistent basis in several ways. A value for the conversion in a particular test could be obtained in simple fashion by the following method.
tion of 100% as the maximum conversion also provides a slight inaccuracy a t high conversion levels. To eliminate these various sources of errors, a method described by Sebastian and Riesz (6) was modified for use in this application. This method is based on the direct comparison of the volumes of the gas produced in the test and of the gas formed a t equilibrium under the test conditions:
yoconversion
where expansion is defined as the increase in gaseous volume, excluding steam, per volume of natural gas entering the system, or
(by gas analysis) = 1‘ o u t ~
Vi,
(yoCH,
in outlet gas)
(yoequivalent CH, in feed gas)
100 (1)
This calculation introduced the possibility of multiplying any errors in analyzing the gas by any inconsistencies or errors in measurement of gaseous volumes (VI, and Vout). The assump1 Present address, Armour Research Foundation of Illinois Institute of Technology, Chicago, 111.
% equilibrium conversion
Expansion =
expansion,,t,,i expansion esuii. 100
= _____
A volume volume,,t~.
(2)
(3)
The equilibrium method is inherently exact and involves one less experimental determination, because it is not necessary to obtain the gas analysis. Since Sabatier and Senderens ( 5 ) first studied the methanesteam reaction, many others, including Neumann and Jacob ( 1 ) and Pease and Chesebro, ( 2 )have evaluated the equilibrium reactions. In the case of the natural gas-steam reaction, a more com-
