LAWRENCE C. WIDDOES
AND
DONALD L. IUTZ
University of Michigan, Ann Arbor, Mich.
Vapor-liquid equilibrium measurements have been made on binary systems of carbon monoxide and propane, propylene, and decane a t temperatures from -7' to 190 'F. and a t pressures from 100 to 2700 pounds per square inch. Phase diagrams and the criticaI points were determined for the carbon monoxide-propane system as well as phase compssi tions. The equilibrium constants for carbon monoxide are the sanie for the p r o p 'iene as for the propane system, whereas the constants for carbon monoxide i n the decane system are about double the values for the propane system a t 100' F.
XLCULATIONS for separation processes require vaporliquid equilibria data, usually in the form of equilibrium constants. Carbon niono\ide may be a constituent of a hydrocarbon mixture for which phase separations are required. This paper presents experimental data on the phase compositions of binary mixtures of carbon monoxide with propane, n-decane, and propylene. Equilibrium constants are presented for carbon monoxide in these systclms. APPARATUS AND MATERIALS
The apparatus used for bringing the vapor and liquid into equilibrium mas similar to that described by Katz and Rurata (2). It consisted primarily of an equilibrium cell with a glass window and suitable tubing and valve connections. Pressure mas supplied by a hand pump using mercury as a confining liquid, and
3000
,
I
~
was measured by a calibrated Bourdon gage. The cell wa5 suriounded by an air bath which was agitated by a fan and heatcd by electric coils. Temperatures of - 7 " F. were obtained by moving the entire apparatus into a cold room maintained a t - 7 ' to -10" F. The entire mechanism waq mounted on a trunnion and rocked to ensure equihbrium, the mercury in the ccll causing severe agitation of the liquid and vapor phascs in the cell. The temperature was measured by a pair of calibrated coppciconstantan thermocouples i n series embedded in the mdls of the cell While recorded cell tcmpcratures never varied by more than =tO.5" F. from the values reported, other work done on similar equipment indicates that tcmpei ature gradients up i o 1" niay exist from top t o bottom of the cell. Volume mcasurements mere taken bv means of a calibrated scale fastened to the glass windo.lr. of the cell. The carbon monoxide uqed W~IS manufactuxd in the laboratoi v
'
,
62 10 MOLE PERCENT CARBON MONOXIDE
1 37.90MOLE PERCENT PROPANE
,
I
TEMPERATURE e F:
Figure 2.
Figure 1. Phase Diagram of Carbon MonoxidePropane iMixture
1742
Critical Locus for Carbon IIIonoxidePropane System
INDUSTRIAL AND ENGINEERING CHEMISTRY
September 1948
1743
The material charged into the equilibrium cell was compressed t o a single phase by means of the mercury hand pump and brought t o a specified constant temperature. The pressure was then gradually reduced in small increments into the two-phase region by withdrawing mercury. Before observing how much vapor and liquid phases were present at each pressure, the cell was agitated vigorously
I
io
I
I J I Illll 50 loo
I
I
-
I I I IIII 5
PRESSURE LBS. PER
O
o
sa.I N
m ABS
I
I
I I I1111
moo
At temperatures away from t h e critical, the bubble point pressure observed visually coincided with the pressure at which there was a break in the pressure volume curve. At temperatures near t h e critical, critical opalescence and fogging occurred and the pressure at which t h e meniscus appeared near t h e center of the fluid was uncertain t o a s much as *30 pounds. T h e quantity of fluid used i n the cell was too large t o permit expansion through the lower dew point. Samples of each phase were removed and analyzed at -7", loo", and 150" F. and at various pressures from 95 to 900 pounds per square inch. A surge cylinder of large volume in comparison with the cell was filled with gas and mercury a t high pressure. T o take a vapor phase sample the valve a t the top of the equilibrium cell was cracked to let vapor escape into the sample tube, and the valve a t the bottom of the cylinder %:as cracked to throttle mercury into the cell from the high pressure surge cylinder. With a little ex-
Figure 3. Equilibrium Constants for Carbon LMonoxide-Propane
by dehydrating formic acid with concentrated sulfuric acid. The carbon monoxide was manufactured under pressures as high as 1200 pounds per square inch gage by letting formic acid flow slowly into a heavy stainless steel cylinder filled with concentrated sulfuric acid, The carbon monoxide was passed through a purifying train consisting of sodium hydroxide pellets, Ascarite, and Dehydrite before being stored. Carbon monoxide manufactured in this manner was analyzed in the ?*I.W.Kellogg laboratories by the mass spectrograph as being 99.9% carbon monoxide. The propylene and propane used were furnished through the courtesy of the Phillips Petroleum Company. The propylene was 95% propylene and 5% propane, and the propane used was pure grade 99.9% propane. The n-decane was purchased from the Connecticut Hard Rubber Company, and was stated t o be 95% n-decane. EXPERIMENTAL PROCEDURES
Two types of data were obtained. Phase diagrams were determined for mixtures of a given composition at temperatures from - 7 " to 190" F. and pressures from 100 to 2700 pounds per square inch. Equilibrium vapors and liquids at specified temperatures and pressures were separated and analyzed. In making bubble and dew point readings the procedure was as follows:
MOLE
Figure 4.
PERCENT CARBON MONOXIDE,
Phase Compositions for Carbon Monoxide-Propane System
I N D U S T R I A L A N D EN G I N E E R I N G CHEMISTRY
i 744 ??/iBLF
1.
PHASE
DIAGRAM DATAFOR '29RROS PROPANE MIXTI-RES
Composition, Mole % 20 4 Carbonmonoxide 79 n Propane
26.59 73 11
Critical Carbon nionxoide Propane
42 13 57 S i
Carbon nionxoide Propane
Critical
67.56 52.44
62 10 I
37.90
Critical Carbon monoxide Propane
Crit,ical Carbon monoxide Propane
Critical 0 Lpper dew point. b Lower dew point.
Teinueiatiua, 0
I?.
52 8 130 9 143 3 lb3 0 180 8 182 8 188.0 50.5 127.9 153 0 168.6 176.8 180.8 179.0 73.8 103.0 120.6 147.5 149.6 153 7 145 76.9 101.2 111.8 120.4 124.6 130.7 130.0
-6 . 8
18.0 39.5 54.8 73.0 79.0 76.0
?vlOKOXIDE-
Pressure, Lb./Square Inch Absolute Bubble Dew point point (extrapolated) 920 (1%) 103; (350) 1040 (410) 1120 (520) 960 (690) I000 (710) YO0 1190 (150) 1205 (400) 1210 (500) 1165 (610) 1090 (700) 990"-7506 1030
_-
(280)
1885 1765 178.5
(400)
(610)
1430-780 1420-810 1410-900 1470 2100 1960
(340) (450) (500) (570) (610) 1850-670
1880 1740 1690 16.35
(100)
2670 2600
(200)
2000
(280) (360) (480) 216s-520
236,j 2205
2180
perience the pressure in the cell could be held t o * 5 pounds by this procedure. After t'he vapor phase was removed, a liquid phase sample was taken by the same method, except t h a t the pressure in t'he cell was maintained 200 t o 300 pounds per square inch above the bubble point pressure. The light hydrocarbon gas mixtures were analyBed in a modified Orsat apparatus. Propylene was absorbed in sulfuric acid ( 3 ) and carbon monoxide in a cuprous sulfate solut,ion ( 6 ) . Proparic' was determined by difference. The procedures were provcd by analyzing synthetic mixtures. Complete absorption of the pure carbon monoxide \$-as obtained in the cuprous sulfate solution. Decane was caught in a trap submerged in ice a n d weighed, and the volunie of carbon monoxide evolved from the decane wah measured by change of pressure in a 382.3-m1. receiver. The oar'bon monoxide was passed through act,ivatcd silica gel as i t left t,he trap. Duplicate analyses using Orsat type apparatus checked to within 0.3 nil. For the propane and propylene systems, the compositions reported are t h e average of four analyses made on each sample. For t8hedecane system, the vapor phase composit,ions wcrc obtained by adsorption of t h e decane on silica gel. Such small quantit,ies of decane were involved t h a t the results arc of questionable value. CARBOK MONOXIDE-PROPANE SYSTEM
The phase compositions of the carbon monoxide-propane system are indicated from - 7 " I?. up t o t'he critical locus by t h r combination of phase diagrams and individual phase compositions. Table I 1ist)sthe bubble points and dew points for five compoaitions. Figure I is a phasc diagram for the 62.101, carbon monoxide mixbure, including the volume pcrccntage vapor and liquid lines which were of assist'ance in determining t h e critical point for all mixtures. Figure 2, the critical locus for the binary system includes the bubble and dew point curves from the data of Table I. Equilibrium phase compositions are presented in Table 11. T h e carbon monoxide and propane equilibrium constants (mole % in vapor/mole % in liquid) are plotted on Figure 3 as a function of pressure, and the phase compositions are given on Figure 4.
1 Figure 5.
Equilibrium Constants f o r Carbon Monoxide-Propane
Vol. 40, No. 9
Figure 6.
1 I Illlll 80
I
I1111111 5
I
0 0 ~ PRESSURE-LBS PER SO. IN ABS DO
I
I I 11IU so03
Equilibrium Constants for Carbon Moiloxide and PropSIiene at 100" F.
September 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
1745
Decane
Figures 2 , 3, and 4 must be consistent with each other. The equilibrium constants of Figure 3 must converge t o unity at the mitical pressures indicated by Figure 2 for a given temperature. The phase diagrams give the bubble and dew points for the specific compositions employed. The phase compositions must give the equilibrium constants when t h e vapor composition is divided by the equilibrium liquid composition. T h e phase compositions, equilibrium constants, and phase boundaries have been established as mutually consistent. Figure 5 presents the equilibrium constants as a function of temperature, with lines of constant pressure based on Figure 3.
MOLECULAR W T
Figure 8. Equilibrium Constants for Carbon Monoxide i n Paraffin Systems a t 100" F.
CARBON MONOXIDE-PROPY LENE
To determine whether changing the hydrocarbon from a paraffin to a n olefin would affect the equilibrium for carbon monoxide, a few measurements were made employing propylene. Because pure propylene wa6 not immediately available, bubble and dew TABLE 11.
T'APOR AND
LIQUID PHASE
COMPOSITIONS
Liquid Vapor Pressure, Composition, % Lb./Sq. In. Temperature, C o m P o S l t i O n , % Abs. F. CO CsHo CsHs CO CsHo CsHs c Propylene-Carbon Monoxide System 246 100 0.57 95.7 8.7 87.5 3.8 3.74 351 ' 100 2 . 3 8 94.2 3 . 4 1 30.13 67.18 409 100 2.65 94.4 3.05 3 6 . 3 61.8 1.9 595 100 6.92 89.95 3.26 51.95 46.2 1.85 Propane-Carbon Monoxide System408 100 4.24 95.76 44.89 . . . 55.11 513 100 6.36 93.64 ... 565 100 8.49 91.61 912 100 14.35 85.65 95 -7 ... ... ... 272 -7 7.67 . . . 92:33 ... 406 -7 12.15 ... 87.85 ... 678 -7 ... 78.63 21.37 ... 376 150 0.51 . . . 99.5 450 150 597 150 5.35 94:i5 82 1 150 9.59 90.41 Decane-Carbon Monoxide System
...
...
...
...
---
CmHa
C10H22
R u n I 184 Run I1 184 R u n I 371 R u n I 744 Run I1 744 R u n I 213 Run I1 213 R u n I 389 Run I1 389 R u n I 764 Run I1 764
100
100 100 100 100 150 150 150 150 150 150
2.47 2.22 4.26 8.55 8.63 2.85 2.62 4.62 4.72 9.28 9.05
97.53 97.78 95.74 91.45 91.37 97.15 97.38 95.38 95.28 90.72 90.95
. . . . . . ... . .
. . . . . . . . . 97.3 . . .
. . . .
. . . . . . . . . 2.7 . . .
. . . .
. . . . . . ... . .
.. . .. . 95.3 4.7 ... . . . . . . . . . ,_. _ _ . . _ . . ,. .. .. & : i 3 i : 7 7 : :: .. ,. , , , ,,
,
,
,,
,
MOLECULAR WT.
Figure 9. Equilibrium Constants for Carbon Monoxide in Paraffin Systems a t 150' F.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1746
points were not observed and only phase compositions included in Table I1 were talrcnat 100 F. Figure 6 shows that the cquilibrium constants for carbon monoxide in prop1 lene are the same as the eonstants for the propane system, within the experimental error. From the relative volatility of propylene and propane, the K's for the propylene system should have been slightly lower t h a n for t h e propane system, as the convergence pressure would be slightly loFer. CARBON BIOSOXIDE-DECAKE
To determine t h e effect of molecular weight of the hydrocarbon, equilibrium phase data mere determined for the carbon monoxiden-decane system a t 100 ' and 150' F. T h e data are included in Table 11 and the equilibrium constants of carbon monoxide are compared p i t h the constants for the propane system in Figure 7. T h e decane percentage in the vapor iyas assumed to be t h a t from the partial pressure of decane rather than from the analyses. Inasmuch as there was a definite effect of the molecular weight of t h e paraffin constituent, a n analogy was assumed with the binary hydrocarbon systems containing methane (I, 4). Higher
Vol. 40. No. 9
convergence prcssurcs for thc cquilibriurn c,onstants will occur x i t h incrcasing molecular weight of the hydrocarbon constituent. Figures 8 and 9 present estimated equilibrium constants for carbon monoxide a t 100" and 150" F., respectively, as a function of molecular \wight, based on propane and decane data. The shape of the curves was taken as symmetrical with t h c methaneparaffin syst,eme. ACKNOWLEDGMENT
The 11. W. Kellogy Company provided the fellowship t.hat made this work possible. The Phillips Petroleum Company furnished the pure propane. LITERATURE CITED
(1) Hanson,l i z a z a , and Brown, IND.ENG.CHFY.,37. 1216 (1946). (2) Katz and Kurata, I b i d . , 32, 817-27 (1940). (3) hlatuzak, S . I?., IND. ENC.CHEM., ANAL.Eo., 9,354 (1937). (4) Sage, B. H., and Lacey, W. N., Am. Petroleum Inst., "Driliiiig and Production Practice," p. 308, 1941. ( 5 ) U. S. Steel Corp., "Methods of the Chemists, United States StoelCorporation," Pittsburgh, P a . , Carnegiesteel Corp., 1918. RECEIVED July 7, 1947.
of Certain Ant
0
lVATbLTRAEANP)ACCELERATEIPAGIIVG H-Y
E. ALBERT
The Firestone Tire & Rubber Company, " f k r o n ,Oh'io
S
INCE the early work on GR-S in this country, it has been
recognized t h a t the requirements for a n antioxidant in copolymers of this type are different from those for an antioxidant in natural rubber. Because of this, a considerable amount of evaluation work has been carried out with GR-S t o determine the best antioxidant and the concentration necessary for satisfactory stabilization of both raw polymers and vulcanizates. The results of oxygen absorption studies in this connection have been reported ( l a ) . The results of natural and accelerated aging tests are presented in this paper and their correlation with the oxygen absorption results is discussed.
COMPLETE R E S I N I F I C A T I O N
MODERATE R E S I N 1 F l C A T I O N SLlGMT R E S I N I F I C A T I O N
5 YEbRS NbTURAL
VERY H I G H CURE
4 DAYS 90OC.
HIGH OJRE
*
AGING
PREPARATIOZT O F POLYAIER SAVIPLES
d ZIPoF.1
LOW CURE S L I G H T CURE
VERI
n i w ~ CURE SOFTEN ED
NO
DETERIORATIOII
0.5%
1.0%
1.5%
For the evaluation of the rcsistance to aging of GIZ-S polymer samples containing various antioxidants, a n accelerated aging test of 4 days a t 90" C. in a forced circulation air oven was employed. The samples Twre examined at the end of each day during this test. Natural aging behavior was observed by examining samples after aging 1, 2, and 5 years a t room temperature in the absence of light. During deterioration, a GR-S polymei. sample passes thmugh various stages of stiffening or cure and (,hen starts to resinify (1). I n some cases, there is a n initial softening before this stiffening takes place. These stages of deterioration can be determined readily by visual and by ha,nd examinat,ion. I n the earlier stages of stiffening or cure, where PIIooney plast,icityvalues can be determined, the hand tests correlate well with these values.
OVEN AGING
MOONEY P L A S T I C I T Y
WL/4
M E D l U H CURE
EVALUATION O F ANTIOXTUASTS IN POLYMER AGING
2.0%
3.0%
P H E N Y L . BETA.NPPtiTHYLAU1HE mNCENTRATlON
Figure 1. Effect of Phenyl-&Naphthylamine Coucentration on Natural and Oven Aging of GR-S Polymer
The polymer samples used in this investigation irere prepared from uninhibited GR-S latcx takcn from a plant autoclave just before addition of the stopping agent. The commercial grade of the desired antioxidant was added in the form of a dispersion and then coagulation was effected b y a 2% aluminum sulfate solution. The coagulum wa,s washed t.horoughly on a laboratory mill and then dried 20 hours a t 75" C. When subjected to this drying treatment, samples containing no antioxidant (blanks) reached a degree of deterioration corresponding t o moderate resinification because the aluminum sulfate employed for coagulation m-as a commercial grade containing an appreciable quantity
