Phase Equilibria in Hydrocarbon Svstems J
METHANE-n-BUTANE-DECANE
SYSTEM AT 40" F.
H. H. REAMER, B. H. SAGE, AND W. N. LACEY California Znstitute of Technology, Pasadena 4 , Calif.
D
URING the past two decades the prediction of the phase behavior of hydrocarbon s y s t e m has received much experimental and theoretical consideration. At present there exists a sufficient background of information to permit the evaluation of the constants of an equation of state ( 1 ) which will establish the equilibrium ratios (16) of the lighter paraffin hydrocarbons in
A chosen value of this parameter corresponds to a definite composition of the coexisting liquid and gas phases at a specified pressure and temperature. The phase behavior of the related binary systems has been investigated (6, 7, 12, 14, 15) and the vapor pressures of the less volatile components are available ( 3 , 7 , 1 2 ) . When taken together with the directly measured compositions of the coexisting phases these data suffice to establish the phme behavior of the ternary system a t 40" F. I n some cases, it was necessary to extrapolate the characteristics of the binary systems to 40" F. because the earlier measurements did not extend below 70" F MATERIALS, METHODS, AND PROCEDURES
The materials and methods employed in this investigation were identical with those GAS reported in connection with earlier studies of the phase behavior of the methane-nbutane-decane system at 280" F. (9). For this reason no description of the equipment or the methods of purification of the materials is given here. The miutures of methane, n-butane, and decane were brought t o equilibrium in a steel vessel in which they were confined over Figure 1. Composition of Coexisting Phases at 40" F. mercury a t the desired Dressure and temperature. Samples of the coexisting gas ternary and quaternary systems. Ternary systems have not been and liquid phases were withdrawn and the quantities of each of the components in them were determined by means of a partial investigated extensively a t elevated pressures. Such measurements afford a useful means of determining the influence of the nature and amount of each of the components present upon the phase behavior of the system. A general study of the properties of the methane-+-butaneedecane system a t elevated pressures was undertaken. The present discussion includes a description of the phase behavior of this system a t 40' F. and a correlation of the critical pressure and temperature as a function of composition. The volumetric behavior (6-9, 11, 15)and the phase behavior ( 4 , 6, 12, 16)of the methane-n-butane-decane system have been determined in some detail. However, the study of the composition of the coexisting phases in ternary mixtures of this system was limited t o temperatures of 160" F. ( 4 ) and 280" F. (9). I n order to establish more fully the phase behavior of the system, a series of measurements of the composition of the coexisting phases was made a t 40" F. I n addition, the composition of the system at the critical state has been presented in graphical form as a function of pressure and temperature. The latter correlation was based upon the available volumetric and phase equilibrium data. The composition of the liquid phase can be defined in terms of a loo0 2000 3000 4000 5000 parameter described by the expression (9) NOLE FFidCTON
n BUTANE
PYICE
PRESSURE
Figure 2.
1671
POUNDS PER SQUARE
INCH
Equilibrium Ratio for M e t h a n e at 40" F.
INDUSTRIAL AND
1672
{NGINEERING CHEMISTRY
Vol. 44, No. 7
1.0
0.5
0.9 LJ
0.8
-f
w
z
k!
c.
(3
Q
,? F
0.05
z
3E
0.5 (1
0.01
3
0 W
2
-I 3
0.02
d 0.4
2E2
0.1
9
0.6
k
0.2
0.005
0.3 0.002
s
0.2
POUNDS PER SQUARE INCH
PRESSURE 0. I
Figure 4.
1000
2000
PRESSURE
Figure 3,
TABLE I. Pressure, Lb./Sq. Inch Abs.
4000
3000
POUNDS
5000
PER SQUARE INCH
Equilibrium Ratio for n-Butane at 40" F.
Equilibrium Ratio for Decane at 40' F.
condensation analysis ( 4 ) . A description of the equipment employed is available ( 1 3 ) . It is believed that the pressures were known within the larger oi 0.05% or 1 pound per square inch. Temperature was measured with a calibrated platinum resibtance thermometer and w a k knowi relative t o the international platinum scale within 0.02' F. EXPERIRIENTA L RESULTS
EXPERIXESTALLY DETERMINED COYPOSITIOXS O F COEXISTIXG PHASES I X lIETHANE-9Z-BUTANE-DECANE S Y S T E M A T 40 O F.
Gas Phase Mole Fraction 11ethane %-Butane Decane
1000
0,9849 0,9736
....
2000
0.9782 0.9594 0.9283 3000 0.9699 0.9277 4000 0.9555 0.9042 5 Defined in Equation 1
0,0145
0,0006 0.0004
0.0260 ,...
.. . .
0.0207 0.0392
0.0011 0.0014 0.0009 0.0038
0.0708
0.0263 0.0631 0.0294 0,0582
0.0092
0.0151 0.0376
Liquid Phase Mole Fraction Methane n-Butane Decane
~ ~ , Parametera
0.3420
0.2092
0.4488
0.3422 0.5177 0.5437 0.5805 0.6432 0.6950
0 4729 0.1388 0.2293 0.2966 0.0923 0.1641 0 0593 0 0806
0.1849 0.3435 0,2270 0,1228 0.2645 0.1509 0.1803 0.1075
0.3179 0.5125 0,7189 0,2878 0,5025 0,7073 0,2587 0.5052 0 2475 0 4285
....
0.7604
0.8119
....
....
~
Table I records the compositions of those coexifiting phases which were de~ ~ ~ , ~ i ~ termined experimentally a t 40' l?. The compositioii parameter defined by Equation l is shown for each of the states investigated. Measurements were made a t pressures of 1000, 2000, 3000, and 4000 pounds per square inch. The results of this experimental study constitute Figure 1 and the combining lines for the experimentally studied states have been
TABLE 11. COMPOSITIONS OF COEXISTIKG PHASES IS METHAXE-~-BUTANE--DECASK SYSTEX. 4 ~40' F. Pressure, Lb.1~~.
Inch Abs. 1000
~ ~ Parameter' 0.0
0.3040 0.3189 0.3314 0.3409 0.3520 0.365 0.4880
0.2674 0.3955 0.5184 0.635
0.2
0.5080
0.6684
0.4 0.6
0.5308 0.5599 0.6024 0.6130 0.6356 0.6689 0.7280
0.2 0.4
0.6 0.8
1 .o
2000
0.0
0.8
3000
0.0
0.2 0.4 4000
0.6 0.0
0.2 0.4
*
Liquid ~ Phase Mole ~ Fraction ~ Methane %-Butane Decane
Defined in Equation 1.
0.7200 0.7518
0.7990
o.ih
0.1877 0.2641 0.3181
0.6960 0.5499 0.4012 0.2636 0.1296
..
0.5120 0.3936 0.2815 0.1760 0.0795
0 . of29
0.3870 0.2915 0.1987 0.1088
0,0496
0,1986 0.1206
0.1324 0.1632
0.0804
0,2800
~Gas Phase hiole ~ i Fraction Methane n-Butane Decane
0.9991 0.9917 0.9860 0.9815 0.9778 0.975 0.9985 0.9860
0.9708 0.9474 0.9061 0.9960 0.9795
0.ob76 0.0134 0.0180 0.0217 0.025 o.oi27 0,0279 0.0509 0.0907
0.9520 0.8922
O:bl68 0.0423 0.0939
0.9858 0,9633 0.9163
0.0226 0.0525
0.0009 0.0007 0.0006 0.0005 0.0006
..
0.0015 0.0013 0,0013 0.0017 0.0032 0.0040 0.0037 0,0087 0.0139 0.0142 0.0141 0.0312
~ i ~ ~ Equilibrium Ratios Methane n-Butane Decane-
3.287 3.110
0,0858
0,0013 0,0013
2.Y75 2,879
0.0501
0.0015 0.0021
,778 -.671 2 046 1.941 1.829 1.692 1.504 1.625 1.541 1.423 1.226 1.369 1.281 1.147
$ !
0.0451 0.0419 0.0394
0.0039
..
0,0029
0 . ii9i
0,1486 0.1927 0.2851 0 . iio5
0.3195 0.5754 0,4&56 0.6630
0.0032 0.0047 0,0095 0.0403 0.0103 0.0127 0.0287 0.1280 0.0507 0.0710 0.2587
~
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
July 1952
1673
curves of Figure 1 was 0.0009 mole fraction The effect of pressure upon the equilibDecane riuxn ratios of methane, n-butane, and ExperiSmoothed mental decane at 40" F. with C as a parameter is shown in Figures 2, 3, and 4, respec0.459 o.183 0.449 o.185 tively. These data indicate the same type of behavior found for this system 0.344 0.344 0.227 0.227 at other temperatures (4, 9). 0.123 0.123 In Figures 3 and 4 t h e behavior of 0.267 0.265 0.151 0.151 n-butane and of decane in the n-butane0.180 0.180 decane system was not included. Like0.108 0.108 wise, details of the behavior of the ternary system a t pressures below 500 0.001b 0.001 pounds per square inch were not sho~vn. 0.001 0.001 0.001 0.001 Smoothed values of the compositions of 0.010 0.010 the coexisting phases and of the as0.004 0.004 sociated equilibrium ratios at 40 O F. are 0.009 0.009 0.015 0.015 depicted in Table 11. Table I11 presents 0.036 0.038 a comparison of a few of the directly measured values of t h e composition of the coexisting phases with those tletermined from the equilibrium ratios recorded in Table 11. This comparison indicates an average deviation for t h e experimental and smoothed data at 27 dew point and 27 bubble point state? of 0.0012 mole fraction.
SMOOTHED AND EXPERIMENTAL COMPOSITIONS I N METHANE-n-BUTANE-DECANE SYSTEM AT 40' F.
TABLE111. COMPARISON Pressure, Lb./Sq. Inch Aba.
1000 2000 3000 4000
OF
Methane ExperiSmoothed mental
Composition Parametera
o.348 0.328b
0.318 0.719 0.288 0.502 0.707 0.259 0.505 0.248 0.428
0.518 0.544 0.580 0.642 0.695 0.760 0.811
0.318 0.288 0.502 0 707 3000 0.259 0.005 4000 0.248 0.428 a Defined in Equation 1.
0.988) 0.977 0.959 0.928 0.970 0.928 0.955 0.904
1000 2000
%-Butane ExperiSmoothed mental
LIQUIDPHASE o.342 0.342 o.469 0.213 0.518 0.544 0.580 0.643 0.695 0.760 0.812
o.473 0.209
0.139 0.229 0.297 0.091 0,154 0.059 0.081
0.189 0.229 0.297 0.092 0.154 0.059 0.081
GASPRASE 0.985 0.011) 0.978 0.021 0.959 0.039 0.928 0.071 0.970 0.026 0.928 0.063 0.956 0.030 0.904 0.060
0.014 0.021 0.039 0.071 0.026 0.063 0.029 0.058
b Composition expreased as mole fraotion.
depicted. Information about the behavior of the methane-nbutane system (1%) and of the methane-decane system (6, 16) shown in Figure 1 was obtained by extrapolation t o 40' F. of the experimental studies for these systems made at higher temperatures. The standard deviation of t h e experimentally measured compositions of the coexisting phases from the smooth
PHASE BEHAVIOR
Ternary systems have been considered in detail by Roozeboom
(IO)and Kuenen (2) and have been reviewed more recently ( 1 4 ) with hydrocarbon mixtures as examples. However, the available experimental information concerning the phase behavior of ternary hydrocarbon systems a t elevated pressures is sufficientlllimited to justify a brief presentation of the effect of temperature and pressure upon the characferistics of the system. Figure 5 ie a temperature-composition diagram for the methane-n-butanedecane system at 3000 pounds per square inch. The composition of the system is portrayed on the triangles, A , B, C and D,E,F . The warped surfaces, S, T , and 77, correspond t o values of 0.2, 0.4, and 0.6, respzctively, for the parameter C . These surfaces
E
I d
E$
?
C DECANE
Figure 5. Temperature-Composition Diagram for Methane-n-Butane-Decane System at 3000 Pounds per Square Inch Absolute
WBUTANt
DECANE
Figure 6.
02
0.4
0.6
0.8
Critical Pressures for Methane-n-Butane-Decane System
1674
INDUSTRIAL AND ENGINEERING CHEMISTRY
VOl. 44, No. 7
ACKNOW LEDGM EN”
METHANE
This paper is a contribution from American Petroleum Institute Research Project 37. 1-irginia Berry and David Downing assisted materially with the experimental program. Olga Strandvold contributed to the preparation of the nunuscript. NO?vIENCLATURE
C
composition parameter, defined by Equation 1 S mole fraction of a component in coexisting liquid phase I’ = mole fraction of a component in coexisting gas phase ’I = pressure, pounds per square inch absolute K = equilibrium ratio ( Y / X ) = =
Subscripts 1 signifies methane 4 signifies n-butane 10 signifies decane LITERATURE CITED
n- ~ T A N E
DECANE
0.2
Figure 7 .
0.6
0.4
0.8
(1) Benedict, M., Webb, G. B., and Rubin, C . , .1. Chew.. P h y s . , 10,747 (1942). ( 2 ) Kuenen, J. P., “Theorie der Verdampfung und
Verflussigung von Gemischen und der Fraktionierten Destillation,” Barth, Leipzig, 1906. (3) Olds, R. H., Reamer, H. H., Sage, B. H., and Lacey, W. K., IXD.ENG. CHEM., 36, 282
Critical Temperatures for 4lethane-n-Butanc-l)ec;mne System
(1944).
&ow the variations in the composition of the coexisting liyuici and gas phases as the temperature is increased’ The curves G Q M , HPL, and I R K depict the bubble point and dew point curves a t 40 O, 160 O , and 280 O F. The locus of critical states is the curve, QPRJ. The decrease in the range of compositions where two phases are encountered with an increase or decrense in temperature from about 160” F. is evident. Similar diagrams show that a t higher pressures the range of compositions for which two phases exist is still smaller. The compositions corresponding t o the critical state are shuwii by a series of isobaric lines in Figure 6 . Lines of constant value of the parameter c have been i n c h l e d for reference. The (lata available indicat,e that the maximuni two-phase pressure for t l i e ternary system occurs in the methane-decane binary system. The information submitted in this figure was not based upon direct observation of the critical state but upon correlation of all available quantit,ative volumetric and phase behavior data of this system ( 4 , 9). Figure 7 is a diagram with critical temperature aa the parameter and was obtained in a similar manner. The informat,ion shown in Figures 6 and 7 is recorded in Tables 11’ anti V.
TABLE11’.
CRITICAL PRESSURES A X D hxETHANE-n-BUTANE-DlGCASE
Composition Parametera 0.2
0.4
Pressure, Lb./Sq. Inch -4bs. 1000
0.8
F.
1500 2000 3000 4000
563 545 507 421 317
1000 1500
549 511
3000 4000
273
1000 1500 2000
2000
0.6
Estimated Temp.,
0.041
0 151
474 387
0.320 0,249 0.192 0.130 0.081
0.479 0.372
498 461 419
0.160 0.351 0.501 0.674
0,504 0.390 0,300 0.196
0.141
0.688 0.527 0.099
322
1000 1500
418
2000
371 322
(1949). J , , sage, E , H., and Lacey, lv, s,, Ihid., 39, 206 (1947). (6) Reamer. H. H., Olds. R. H., Sage. B. H., and Lacey, IT. N . ,
Ibid.,34, 1526
0.342 0.509
is)
(1946).
Ihid., 39, 77 (1947), (9) Ihid.. 43, 1436 (i95i!.
FOR ~IETHANe-n-Bv.r‘ir,~:TABLE 17, CRITICALCo&I.rPoslT~rora DECAKE SYSTEX
Estimated conlposition Parameter“
0.2
F.
0.4
0.286
0.872 0.868 0.845 0.826 0.795 0.751 0.684 0.551 (0.320)
0.083 0.100 0,124 0.180 (0.272)
40 100 160 220 280 340 400 460
3590 3760 3790 3660 3340 2840 2230 1500 710
0.848 0.827 0.804 0.774 0.728 0.661 0.543 0.313 (0 016)
0.003 0.106 0.119 0.137 0.164 0 204 0.27R 0.413 (0.592)
0.108 0,133 0 182 0.274 (0.392)
40
2740 2935 2950 2780 2380
0.826 0.779 I . 733 0,674 0,587 0.440 0.221
0,140 0.178 0.215 0.261 0.331 0.449 0.622
0.036 0.043 0 052 0 065 0.082 0 111 0 1.57
620
0.8
0.336 0.259
0.199 0.130 0.171
0.131 0.392
100 160 220 280 340 400
4900 4930 4840 4615 4280 38nn 3240 2580 1880
1825 1210
Defined in Equation 1. in parentheses are estimated.
b Values
~~
0.023
4373 4540 4530 4296 3950 3480 2860 2175 1410
40
100 160 280 340 400 460 520
0.190 0.117
JIole Fractionb Methane n-Butane Decanr~-
1030
40 100 160 220 280 340
220
0.6
Pressure. Inch Lh.’Srl. Ahs.
0.889 0.879 0.869 0.856 0.835 0.802 0.757 0.668 (n.510) (0 258)
400 460 520 680
(1
Defined in Equation 1.
(1942).
ji) Reamer, H. H., Sage, 33. H., and L a w , W. N., IbzX., 38, 9RA
Mole Fraction Methane n-Butane Deca.n-e 0.262 0.148 0.590 0.428 0.115 0.457 0.559 0 090 0.351 o 711 0.080 0 229 0.808
Reamer, H. 11., Fiskin, J. M..and Sage, E. H., Ibid., 41, 2871
Korpi, K, is) Reamer, I-1, H,,
COMPOSITIOXS FOR SYSTEM
0.201 0.379 0.522 0.680 0.802
3000
(4)
0.027 0.029
0 031 0,034 0.041 0.051 0.068 (0.100) (0.149)
0.053 0.058 0.062
0.071
0.088 0.094
0.102 0.113 0.131 0 167 0.192 0.264
(0.390) (0.593) 0.075 0 OR1 0.0s13 0.103 0.122
n 149
0.192 0.20!1 (0.4081
n 059 0.067 0.077 0.089
INDUSTRIAL AND ENGINEERING CHEMISTRY
1952
Roozeboom, H. W. B., “Die Heterogenen Gleichgewichte VOII Standpunkte der Phasenlehre,” Vol. 3, Vieweg und Sohn, Braunschweig, 1913. Sage, B. H., Budenholzer, R. A,, and Lacey, W. N., IND. ENG. CHEM.,32, 1262 (1940). Sage, B. H., Hicks, B. L., and Lacey, W. N., Ibid., 32, 1085 (1940). Sage, B. H., and Lacey, W. N., Trans. Am. Inst. Mining Met. Engrs., 174, 102 (1948).
1675
114) Sage, B. H., and Lacey, W. N., “Volumetric and Phase Behavior of Hydrocarbons,” Stanford University Press, 1940. (15) Sage, B. H., Lavender, H. M., and Lacey, W. N., IND. ENG. CHEM.,32, 743 (1940). (16) Winn, F. W., “Simplified Nomographic Presentation of Hydrocarbon Vapor-Liquid Equilibria,” Houston meeting of -4.I.Ch.E. (1950). Rx.cErvEr, for review December
11, 1951.
ACCEPTEDFebruary 19, 1959.
Vapor Pressure-Composition Measurements on Aqueous Hydrazine Solutions JEROME 6. BURTLE College of S t . Thomas, S t . Paul, M i n n .
T
HE investigation herein reported was carried out several yewh ago when it became necessary to acquire distillation data on aqueous hydrazine solutions. Search of the literature showed that vapor pressure data in the water-hydrazine system were singularly sparse (%-7), especially in the subatmospheric range. To supply these missing values, the following results are reported. APPARATUS AND PROCEDURE
The apparatus employed consisted of a cyclic still provided with a total condenser and so arranged that an equilibrium sample of both liquid and vapor could be taken. This type of equipment haa been described by Sameshima ( 1 1 ) and by Smyth and Engel ( 1 3 ) . I n the equipment used in this work pressures were observed on a conventional mercury-in-glass U-tube, closed-end manometer, and were read by means of a cathetometer. Boiling temperatures were read on a thermometer suspended in the boiling liquid, Ail thermometers used were graduated in 0.1” C. intervals and were carefully calibrated against a Bureau of Standards thermometer and against pure compounds. The setup used in this investigation differed from that of Smyth and Engel in one important respect-the omission of the thermal stirrer. Since it has becn reported that hot metals catalyze the decomposlition of hydrazine (1) it was deemed advisable to eliminate the hot wire thermal stirring device of the Smyth and Engel apparatus. Instead, a glass wool ebullator was placed inside the boiling pot and, using a 5 ” t o 10” C. temperature differential between boiling pot and heating bath, smooth boiling without bumping was obtained.
TABLEI. EQUILIBRIUM PERIOD Temp.
C.’
50.1 50.1
Pressure, Mm. Hg 38.5 38.6
Boiling Time, Min. 60 30
was then continued for 30 minutes to allow the system to come to equilibrium. The equilibrium boiling period of 30 minutes was chosen when it was noted that duplicate samples showed no significant change in concentration on longer boiling. Results of a pair of typical experiments investigating the equilibrium period are shown in Table I. At the end of this period the liquid condensed in the vapor sample cup (approximately 5 grams) had the composition of the vapor in equilibrium with the liquid in the boiling pot. The pressures a8 indicated on the manometer and the boiling temperature were accurately recorded, all heaters ~~
TABLE11. VAPORPRESSURE-COMPOSITION DATAFOR HYDRAZINE SOLUTIONS AT CONSTANT PRESSURE Composition at Equilibrium
Preasure, Mm. Hg 124.8
281.8
411.2
Conen., G. NSHd100 G. Liquid Vapor 65.5 64.9 65.1 64.5
Stock solutions of concentrated hydrazine were appropriately diluted with distilled water and resulting samples (approximately 120 grams each) were placed in the vapor pressure equipment and a thermometer and the ebullator were introduced. The air in the apparatus was then replaced with nitrogen, the desired working pressure (as measured on the manometer) was attained by means of a vacuum pump and maintained constant by a manostat. When the conditions of pressure had become constant the heating of the sample in the boiling pot was started and continued until the pot contents had begun to boil. The mixture was allowed to distill until the vapor sample cup was filled. Heating
560.4
100.6
Boiling Temp., ’ C. 56.17 58.9 63.8 69.7 74.0 74.2 73.9 71.7 69.1 66.8 74.38 77.6 83.8 88.4 93.0 93.3 93.2 91.9 89.6 86.5 83.66 86.9 92.4 93 5 98.4 102.8 103.4 103.6 102.2 99 4 96.8 91.73 95.5 100.3 106.4 110.9 111.3 110.2 107.9 105.2 97.75 101.5 106.8 112.6 117.2 117.6 116 9 114.2 111.7
Vapor, Mole % Hz0 NzH4 100.00 ... 99.21 0.79 96.60 3.40 84.43 15.57 54.98 45.02 51.74 48.26 42.67 57.33 25.03 74.97 6.90 93.10 0.35 99.65 100.00 ... 99.21 0.79 94.00 5.94 86.79 13.21 60.54 39.46 54.05 45.95 42.67 57.33 22.74 77.26 10.69 89.31 0.54 99.46 100 IO0 99.15 0.85 95.41 4.59 94.61 5.39 85.21 14.79 62.16 37.84 50.88 49.12 55.92 44.08 24.75 75.25 90.30 9.70 1.40 98.60 100.00 98.98 1.02 95.22 4.78 83.86 16.14 42.11 57.89 45.23 54.77 78.12 21.88 90.63 9.37 1.40 98.60 100.00 99.60 .40 94.37 5.63 84.15 15.85 56.92 43.08 44,77 55.23 25.58 74.42 9.55 90.45 98.76 1.24 .
I
.
...
...
LI:q_uid, Mole % HzO NIHI 100.00 90.40 79.91 67.97 51.42 50.13 48.22 32.23 15.28 1.05 100.00 90.91 77.78 68.66 54.05 50.34 44.42 31.85 18.17 1.24 100.00 90.65 79.91 78.16 68.33 54.78 48,48 44.99 32.37 16.20 1.94 100.00 90.06 80.30 68.33 51.53 45.22 31.18 16.97 2.63 100.00 91.16 79.46 68.16 51.42 45.11 32.64 16.04 2.13
...
9.60 20 09 32.03 48.58 49.87 54.78 67.77 84.72 98.95
...
9.09 22.22 31.34 45.95 49.66 55.58 68.15 81.83 98.76
...
9.35 20.09 21.84 31.67 45.22 51.51 55.01 67.63 83.80 98.06
...
9.94 19.70 31.67 48.47 54.78 68.82 83.03 97.37
...
8.84 20.54 31.84 48.58 54.89 67.36 83.96 97.87
