Phase Equilibria in Hydrocarbon Systems J
J
Volumetric and Phase Behavior of the Methane-Prapane System H. H. REAMER, B. Er. SAGE, AND
w. N. LACEY
California Znstitute of Techriology, Pasadena, Calif.
nTeasuretnents of the molal volume of four mixtures of methane and propanewere madeat pressures up to 10,000 pounds per square inch and a t temperatures from 40" to 460' F. The composition of the coexisting phases was determined throughout the two-phase region a t temperatures above 40" F. These results supplement earlier measurements upon this binary hydrocarbon system which were made over a smaller range of pressure and temperature. The results of the two sets of measurements are compared.
Figure 1. Compressibility Factor for Experimentally Studied Mixtures of Methane and Propane a t 220" F.
T
HIS laboratory studied the volumetric behavior of mixtures of methane and propane (12, IS) a t pressures up to 3000 pounds per square inch (all pressures reported are expressed in pounds per square inch absolute) and for temperatures from 70" to 190" F. The original determinations of the composition of the coexisting phases extended throughout the two-phase region for temperatures above 70" F. These volumetric data were obtained with isochoric equipment (11) which left a much larger uncertainty in the measurement of primary variables than did the apparatus employed in later investigations. The present investigation was undertaken to extend the earlier measurements (1.8,I S ) to pressures up to 10,000pounds per square inch for temperatures from 40" to 460" F. and to increase accuracy of data for the range of pressures and temperatures covered by the earlier work through the use of improved equipment and techniques. In connection with the graphical smoothing of the results of the present investigation, supplementary data were employed concerning the properties of the components. The influence of pressure and temperature upon the specific volume of methane has been well established (4-6) and the results have been summarized (7). These volumetric data agree well with Joule-Thomson ( 8 ) and heat capacity determinations (15). Propane has been the
534
March 1950 subject of several volumetric studies (3, 8, 14) and the later measurements agree satisfactorily with those obtained from the Joule-Thomson coefficient (10). These data serve to establish the characteristics of the individual components over the range of pressures and temperatures of interest with an accuracy at least comparable to that with which the present measurements were made. MATERIALS
a
The methane employed in this study was obtained from a field in the San Joaquin Valley of California and contained water and small amounts of carbon dioxide. The gas was received from the field in cylinders at a pressure of approximately 1800 pounds per square inch. I t was passed over granuIar calcium chloride, sodium hydroxide, activated charcoal, anhydrous calcium sulfate, and Ascarite successively at a pressure in excess of 1000 pounds per square inch before being transferred into the equipment. A partial condensation analysis of gas from this source purified in this manner indicated that the quantity of ethane and heavier hydrocarbons was less than 0.0002 mole fraction. Comburtion analyses showed that the quantity of inert gases present was less thanO.OO1mole fraction. The propane was obtained from the Phillips Petroleum Company and was reported to contain less than 0.001 mole fraction impurities. It was fractionated at a reflux ratio of nearly 40 to 1 in a packed glass column. The initial and final portions of the overhead, each amounting to approximately 10% of the charge, were discarded. Material so purified showed a change in vapor pressure a t 100' F. of less than 0.2 pound per square inch for a change in quality from approximately 0.5 to bubble point. This purified hydrocarbon was stored in small, stainless steel containers under pressure. APPARATUS AND PROCEDURE
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLEI. VOLUMETRIC PROPERTIES OF METHANE-PROPANE SYSTEM (Molal volumes expressed in cubic feet per mole) 0.2
0.3
0.4
Mole Fraction Methane 0.5 0.6 40" F,Dew Point
...
...
...
1.296 (511)"
1.269 (733)
1.274 (948)
13.06 5.26 1.917 1.250 1.251 1.208 1.218 1.213 1.201 1.192 1.182 1.173 1.167 1.154 1.141 1.129 1.118 1.099 1.082 1.066 1.055 1.046
li.77 5.63 2,963 1,809 1.266 1.236 1.216 1,200 1.185 1.174 1,162 1.153 1.142 1,125 1.111 1.096 1.084 1.063 1.045 1.028 1.015 1.014
Pressure,
Lb./Sq. Inch Absolute
...
0
200 400 600 800 1,000 1.250 1,500 1,750 2,000 2,250 2,500 2,750 3,000 3,500 4.000 4,500 5,000
8.37 2.230 1.287 1.262 1.260 1.212 1.241 1.238 1.227 1.217 1.213 1.206 1.198 1.184 1.174 1.164 1.154 1.133 1.122 1.108 1.096 1,088
6.000 7.000 8,000 9,000 10.000
0.1
0.2
0.3
21.69 (214)
18.82 (247)
15.88 (293)
1.504 (440) 0
200 400 600 800 1,000 1,250 1,500 1,750 2,000 2,250 2,500 2,750 3.000 3.500 4,000 1,500 5.000 6,000 7,000 8,000 9.mo 10.000
2i.02
1.487 (695) 24'. 86
...
1,500 (938) 25. 80
...
...
0 200 400 600 800 1,000 1.250 1,500 1,750 2,000 2,250 2,500 2,750 3,000 3,500 4,000 4,500 5,000 6,000 7,000 9,000 10,000
22:42 7.32 4.00 2.577 1.740 1.289 1.234 1.203 1.185 1.167 1.150 1.139 1.123 1.102 1.083 1.068 1.054 1.030 1.009 0.9910 0.9765 0.9635
... ...
27'. 2 b 12.11
... 1,500 (1469)
24: i4 9.02 5.04 3.34 2.341 1.559 1.317 1.258 1.222 1.186 1.162 1.142 1,120 1.091 1.067 1.046 1.029 1.000 0.9762 0.9563 0.9396 0,9243
24:40 10.71 6.23 4.11 2.941 2.02 1.525 1.402 1.311 1.252 1.205 1.167 1.138 1.045 1.060 1.033 1.010 0.9744 0.9469 0.9239 0.9149 0.8872
27 .'Sa 12.81 7.70
i.465 1.442 1.414 1.389 1.366 1.353 1.338 1.325 1.313 1.303 1.283 1.266 1.250 1.236 1 I210 1.188 1.169 1.153 1.142
1.431 1.399 1.364 1,345 1.326 1.310 1.292 1,279 1.255 1.234 1.217 1.202 1.175 1.150 1.129 1.112 1.095
i.533 1.456 1.401 1.363 1.333 1.307 1.286 1.266 1.235 1.213 1.191 1.173 1.140 1.113 1,092 1.072 1.055
0.1
0.2
0.3
Mole Fraotion Methane 0.4 0.5 0.6 160' F.
29.40 12.29
30.0 13.17 7.26
i.ib
.
28.69 11.15 i.736 1.662 1.600 1.573 1,539 1.515 1,493 1.474 1.457 1.441 1.414 1.391 1.371 1.353 1.323 1.296 1.273 1.254 1 237, I
...
i.830 1.699 1.622 1.568 1.529 1.497 1.469 1.447 1.427 1.392 1.365 1.343 1.323 1.288 1.259 1.234 1.212 1.193
.
I
...
i.979 1.765 1.616 1.573 1,523 1.482 1.449 1.422 1.378 1.346 1.319 1.295 1.254 1.223 1.197 1,174 1.152
...
...
30.6 13.88 8.20 5.28 3.58 2.475 2.010 1.972 1,669 1,586 1.523 1.476 1.438 1.380 1.336 1.300 1,271 1.224 1.188 1.159 1.136 1,112
..,
... ...
i.b'i.5
1.497 1.424 1.373 1.333 1.300 1.273 1.230 1.197 1.170 1.147 1.111 1.080 1.057 1,035 1.015
...
31.1 14.45 8.89 6.08 4.44 3.13 2.416 2.042 1,843 1.710 1.610 1.538 1.480 1.398 1.339 1,294 1.257 1.202 1.158 1.126 1,100 1,076
0.8
...
Mole Fraction Methane 0.4 0.5 0.6 1000 F. Dew Point 12.88 9.77 6.54 (361) (471) (677) Bubble Point 1.572 1.757 2.124 (1156) (1311) (1352) 26.61
0.7
1,362 (1341)
Bubbie Point 1.305 (1159)
i.468 1.448 1.439 1.415 1.397 1.380 1.370 1.360 1.349 1.340 1.331 1.314 1.299 1.285 1.273 1.250 1.228 1,210 1,195 1.182
-
8,000
The equipment employed has been described in some detail (11). In principle the procedure involved the introduc-
535
...
...
:
1 946 1.704 1.550 1.453 1.388 1.340 1.301 1.241 1.198 1.162 1.134 1.086 1.050 1.024 1,002 0.979
...
31.5 14.94 9.39 6.63 4.99 3.69 2.89 2.402 2.094 1,880 1.746 1.631 1.549 1.436 1.359 1.308 1 ,256 1.186 1.133 1.096 1.068 1.041
0.7
. I .
0.8
1.945 (1431)
:
24 $5 11.71 7. 1 1
4.87 3.54 2.490 1.868 1.632 1.459 1.353 1.270 1.214 1.173 1.109 1.062 1.027 0.9974 0.9528 0.9208 0.8949 0.8735 0.8533
0.9
...
...
...
.,
...
...
,
28,'3(i 13.33 8.29 5.78 4.28 2: i 4 5 2.033 1.767 1.594 1.494 1.415 1.356 1.268 1.208 1.161 1,125 1.067 1.026 0.995 0.970 0.944
0.7
...
31.9 15.33 9.79 7.04 5.40 4.11 3.28 2.733 2.357 2.093 1.905 1.758 1.647 1.494 1.392 1.317 1.260 1.176 1.113 1.072 1.038 1,009
28:80 13.75 8.73 6.24 4.75 3.60 2.861 2.366 2.039 1.811 1.652 1.531 1.441 1.317 1.234 1.172 1.127 1.057 1.008 0.971 0.942 0.914
0.8
I . .
32.3 15.66 10.13 7.38 5.74 4.45
3.60
3.03 2.614 2.311 2.082 1.905 1.769 1.571 1.440 1.346 1.276 1.174 1,101 1.052 1.013 0.982
29:ii 14.11 9.10 6.61 5.13 3.95 3.19 2.666 2.301 2.041 1.836 1.679 1.563 1.395 1.282 1.204 1.144 1.058 0.998 0.954 0.919 0.889
0.9
...
32.6 15.94 10.42 7.66 6.02 4.72 3.87 3.28 2.843 2.511 2.256 2.054 1.900 1.663 1 504 1.391 1.305 1.183 1.097 1.039 0.992 0.958 I
Figures in parentheses are vapor pressures in pounds per square inch absolute. (Continued on page 656)
536
Vol. 42, No. 3
INDUSTRIAL AND ENGINEERING CHEMISTRY
tion of known quantities of TABLE I. VOLUNETRIC PROPERTEES OF METHANE-PROPANE SYSTEM (Continued) methane and propane into a (Molal volumes expressed in cubic feet per mole) closed stainless steel vessel. Mole Fraction Methene The eff ective volume was varied Pressure, 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Lb./Sq. Inch by the introduction and with220' F.Absolute drawal of mercury. Equilib... ... ... ... ... ... ... 34.3 ... 34.7 0 ... 33.4 35.1 35.4 35.7 36.0 200 32.9 33.9 rium was obtained by the use 17.49 16.88 17.21 17.73 15.58 16.07 16.50 400 14.38 15.02 of a mechanical agitator located 11.43 11.15 10.82 11.66 9.44 9.98 10.44 7.88 8.76 600 8.64 8.41 7.82 8.14 6.37 6.96 7.43 5.57 800 within this chamber, and the 6.84 6.62 6.03 6.35 2.'774 4.51 5.17 5.65 3.65 1,000 5.19 5.40 4.64 4.94 3.09 3.78 4.26 2.141 2.504 1,250 temperature was controlled by 4.46 4.26 3.74 4.02 3.39 2.450 2.110 2.952 1.920 1,500 immersing the stainless steel 3.60 3.79 3.13 3.38 2.131 2.814 1.922 2.455 1.808 1,750 3.30 2,695 2.923 3.12 1.951 2.430 1.813 2.162 2,000 1.739 vessel in an agitated oil bath. 2,758 2.929 2.383 2.578 1,829 2.173 1.974 1.737 2,250 1.688 2.639 2.160 2.490 1.738 2.327 1.988 1.678 1.840 1,648 2,500 It is believed that the temper2.406 2.135 2.274 1.991 1.857 1.672 1.746 1.630 2.750 1.615 ature of measurement was 2.216 1.862 1.977 2.098 1,620 1.756 1.595 1.673 1.588 3,000 1.934 1.756 1.842 1.678 1.611 1.535 1.539 1.542 1.563 3,500 known and controlled a t a uni1.732 1.554 1.603 1.662 1.480 1.515 1.490 1.490 4,000 1.505 1.585 1,463 1.494 1.535 1.435 1.442 1.455 1.433 4,500 1.475 form value within 0.03' F. 1.468 1.433 1.402 1.400 1.408 1.388 1.423 1.390 1.450 5,000 relative to the international 1.297 1.313 1.295 1.300 1.345 1.308 1.375 1.323 1,408 6,000 1,226 1.208 1.207 1.214 1,247 1.301 1.272 1.336 1.371 7,000 platinum scale. The pressure, 1.156 1.130 1.140 1.180 1.205 1.306 1.268 1.235 1.343 8,000 1.140 1.112 1.070 1,088 1.278 1.238 1.170 1,202 1.315 9,000 measured by a balance ( I f ) 1.025 1.047 1.105 1.211 1.075 1,140 1.251 1.174 1.295 10,000 which was calibrated against 28O0 F. the vapor pressure of carbon ... ... ... ... ... .., ... ... 0 dioxide a t the ice point ( 1), was 39.1 39.3 38.6 38.9 37.6 37.9 38.2 37.2 200 36.8 18.74 19.28 19.48 19.03 17.31 17.72 18.08 18.42 16.86 400 established within 0.05% or 12.68 12.15 12.44 12.88 11.84 11.10 11.49 10.66 10.15 600 9.40 8.88 9.58 0.1 pound per square inch, 9.16 8.57 7.82 8.22 6.76 7.35 800 7.21 6.94 7.62 7.43 6.64 5.89 6.29 5.40 4.74 1,000 whichever is larger. The total 5.88 6.05 6.42 5,66 5.13 4.39 4.79 3.91 3.35 1,250 4.66 4.43 4.85 5.02 4.16 3.46 3.84 2.633 3.04 1,500 effective volume occupied by 4.13 4.29 3.95 3.74 3.49 2.553 2.861 3.20 2.304 1,760 3.60 the hydrocarbons was known 3.43 3.25 3.74 3.02 2.498 2.763 2,109 2.273 2,000 3.19 2.876 3.33 2.679 3.04 2.100 2.260 2.461 1.987 2,250 within 0.1% throughout the 2,998 2.875 2.417 2.740 2.591 2,095 2,244 1.978 1.898 2,500 2.624 2.501 2.737 2.372 2.227 1.968 2.084 1.887 1.834 2,750 range of conditions encountered 2.521 2.419 2.312 2.198 2.077 1,819 1.878 1,964 1.783 3,000 2.112 2.193 1.947 in the present measurements. 1.865 2,029 1,718 1.746 1.794 1.705 3,500 1.958 1.895 1.832 1.773 1.721 1.653 1,645 1.678 1.647 4,000 The xeight of propane intro1.781 1.731 1.687 1.648 1.617 1,594 1,587 1.584 1.598 4,500 1.609 1.644 1.582 1.558 1.539 1.630 1,529 1,558 1.541 5,000 duced into the equipment from 1.434 1.448 1.426 1.422 1.424 1.472 1.448 1.432 6,000 1.498 the weighing bomb (11 ) was 1.318 1.317 1.322 1.333 1.347 1,391 1.422 1.366 1,454 7,000 1.226 1.235 1.248 1,265 1.287 1.345 1.314 1.414 1.379 8,000 known with an uncertainty not 1 . 158 1,172 1.192 1.215 1.243 1.308 1.274 1.345 1.384 9,000 1,118 1.096 1,146 1.174 1.206 1.276 1.239 1.315 1.354 10,000 greater than 0.02%. Methane 340' F -. mas added from a calibrated ... ... ... ... ... ... ... isochoric reservoir as described 0 ... 42.5 42.6 42.0 42.3 41.7 41.2 41.5 37.5 40.8 200 earlier (11). At the end of a 21.03 21.20 21.58 23 82 20.32 19.74 20.04 19.40 17.62 400 13.89 14.06 13.69 13.20 13.46 12.92 12.62 12.28 11.01 600 particular series of measure10.34 10.50 9.91 10.14 9.66 9.09 9.39 7.72 8.74 800 8.21 8.37 8.02 7.81 7.57 ments a check was made upon 7.00 7.30 6.65 5.76 1,000 6.52 6.67 6.35 6.15 5.92 5.36 5.66 4.58 5.01 1.250 the quantity of material intro6.41 5.54 5.06 5.24 4.84 4.31 4.60 3.60 3.98 1,500 4.62 4.75 4.30 4.47 4.10 3.60 3.87 3.31 3.00 1,750 duced by removing the sample 4.03 4.16 3.74 3.90 3.56 3.11 3.35 2,637 2.873 2,000 3.58 3.70 3.31 3.46 3.15 quantitatively for weighing. 2.766 2,963 2,402 2.573 2,250 3.24 3.34 2.984 3.12 2.836 2.515 2.678 2.237 2.363 2,500 This procedure was usually ac2.958 2 842 3.05 2.722 2.596 2 I329 2.462 2.119 2.212 2,750 2,723 2.625 2.812 2.518 2,405 2.188 2,293 2.098 2.031 3,000 complished in two steps, the 2.370 2.293 2.444 2.213 2.129 1.983 2.049 1.933 1.900 3,500 2.118 2.177 1.997 2.058 1,938 1.847 1.886 first withdrawal being made 1,820 1.809 4,000 1.933 1.972 1.885 1.846 1.805 1,772 1.750 1.740 1,740 4,500 with the entire mixtuIe in a 1.790 1.726 1.755 1.821 1,682 1.700 1.675 1.685 1.676 5,000 1.571 1.587 1 560 1.556 1,552 1.555 1.563 1.580 1.602 6,000 single phase, thus permitting a 1.433 1.435 1.435 1.440 1,452 1.465 1,484 1.540 1.510 7,000 1,330 1.320 1 343 1.360 1.378 1.400 1.426 1.458 1,490 second series of volumetric 8,000 1.255 1.240 1.275 1,295 1,322 1.350 1.380 1.413 1.450 9,000 measurements upon material 1.215 1.194 1.173 1.240 1.270 1.305 1.340 1.417 1.378 10,000 of the same composition but (Concluded on page 697 with approximately 25y0of the original quantity of the methane-propane mixture in the EXPERIMEKTAL RESULTS working chamber. The initial weight of the material introduced The detail with which the experimental data were obtained is agreed with the total material withdrawn in the two steps within indicated in Figure 1, which presents the compressibility factor of 0.03% in the case of each of the four mixtures investigated. four mixtures of methane and propane a t 220" F. Because this The bubble-point pressures for each of the mixtures involved temperature lies above the critical temperature of propane, no were determined from the discontinuity in the isothermal volumetwo-phase behavior appears. The density of the experimental pressure derivative for constant composition. Such discontinuipoints shown in Figure 1 is typical of measurements made a t ties were also utilized to establish the dew-point states. In addiseven other temperatures. These experimental data were tion, direct determinations of the composition of the dew-point smoothed by residual graphical operations, making use of techgas were made with equipment already described (11). The niques already described (8, 9). The results of these smoothing sample of dew-point gas was withdrawn under isothermal, isooperations are presented in Table I, in which the values of the baric conditions and the composition was established by the molal volume are shown for four even-valued compositions. The measurement of its specific volume a t substantially atmospheric corresponding values for pure methane and propane are not pressure and a temperature of 100" F. The uncertainty in the given because these data are already available (7, 10). composition thus determined is estimated to be 0.002 mole Utilizing the values of the bubble-point pressure for each fraction. T
.
.
I
7
. . I
March 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
of the mixtures studied and the directly measured compositions of the dew-point gas, the properties of the coexisting phases were established. The compositions of the dew-point gas and bubble-point liquid as functions of pressure for a series of temperatures were established from the data by the use of graphical methods and recorded in Table I1 for a series of even-valued pressures and temperatures. Table I1 also includes corresponding values of the molal volume of the bubble-point liquid and dew-point gas and equilibrium constants for methane and propane. I t is believed that the compos'tions of the bubble-point liquid and dew-point gas do not involve uncertainties greater than 0.002 mole fraction. A pressure-composition curve for each temperature investigated is shown in Figure 2. Figure 3 presents the product of the pressure and the equilibrium constant as a function of pressure for both methane and propane. This diagram possesses the general characteristics of such diagrams for other binary hydrocarbon svstems. Table 1II"records the properties
TABLE I. VOLUMETRIC PROPERTIES OF METHANE-PROPANE SYSTEM (Concluded) (Molal volumes expressed in cubic feet per mole) Pressure Lb./Sq. Inbh Absolute
0.1
0
h
200 . ~ 400 600 800 1,000 1,250 1,500 1,750 2,000 2,250 2,500 2,750 3,000 3,500 4,000 4,500 5,000 6,000 7,000 8,000 9,000 10.000
--...
.
44.1 21.09 13.43 9.63 7.37 5.61 4.49 3.74 3.24 2.895 2.645 2.465 2.332 2.134 2.000 1,899 1.824 1,713 1,633 1.572 1.525 1.488
0.2
Mole Fraction Methane 0.4 0.5 0.6 400' F.
0.3
... 44.4
21.38 13.73 9.94 7.69 5.93 4.79 4.02 3.47 3.08 2.793 2.582 2.422 2.187 2,028 1.911 1.822 1.696 1.607 1.341 1.489 1 450
44:7 21.66 14.01 10.22 7.97 6.20 5.06 4.27 3.69 3.27 2.951 2.709 2 523 2.251 2.067 1.933 1.829 1.684 1.587 1.513 1.457 1.112
... 45.0
21.93 14.27 10.47 8.22 6.44 5.35 4.48 3.89 3.44 3.10 2.839 2.630 2.324 2.115 1.963 1.846 1.682 1,572 1.491 1.427 1.378
7
o
...
...
200 47.7 48.0 400 23.06 23.29 600 14.87 15.11 800 10.80 11.05 1,000 8.39 8.65 1,250 6.50 6.75 1,500 5.26 5.51 4.42 1,750 4.65 2,000 3.83 4.03 3.40 2,250 3.57 2,500 3.08 3.22 2.840 2,750 2.958 3,000 2.653 2.750 2.388 3,500 2.448 2.205 4,000 2.242 2.075 4,500 2.095 1.975 5,000 1.981 6,000 1.835 1.822 7,000 1.734 1.715 8,000 1,658 1.630 9,000 1.600 1,566 10,000 1.555 1.518 a Figures In parentheses are vapor
...
...
... 45.2
22.16 14.50 10.70 8.44 6.65 5.48 4.66 4.06 3.60 3.24 2.962 2.733 2.398 2.168 1,998 1.867 1.684 1.561 1.471 1.400 1.346 460' F.
...
...
45.4 22.38 14.72 10.90 8.63 6.83 5.65 4.82 4.21 3.74 3.36 3.07 2.833 2.472 2.223 2.036 1 892 1.691 1,553 1.453 1.376 1.317
...
0.7
0.8
0.9 7
... 45.6
22.58 14.92 11.09 8.80 7.00 5.80 4.96 4.33 3.85 3.48 3.17 2.927 2.544 2.278 2.077 1.922 1.699 1.548 1.438 1.355 1,291
...
48.2 48.4 48.6 48.8 49.0 23.54 23.97 23.77 24.32 24.15 15.35 15.78 15.96 15.58 16.11 11.29 11.51 11.70 11.87 12.02 8.88 9.08 9.27 9.43 9.57 6.97 7.17 7.35 7.50 7.63 5.72 5.92 6.08 6.22 6.34 4.85 5.18 5.03 5.43 5.32 4.21 4.52 4.64 4.38 4.75 3.74 4.02 4.13 3.89 4.23 3.37 3.63 3.51 3.73 3.82 3.08 3.20 3.30 3.40 3.48 2.857 2.962 3.22 3.06 3.14 2.521 2.673 2.740 2.600 2 I802 2.290 2.345 2.497 2.400 2.453 2.125 2.198 2.161 2.267 2.231 1,998 2.042 2.019 2.093 2.069 1.817 1.825 1.830 1.818 1.839 1.694 1.675 1.668 1.683 1.665 1.612 1.566 1.550 1.587 1.535 1.537 1.487 1.465 1.510 1.445 1.482 1.417 1.447 1.369 1.395 pressures in pounds per square inch absolute.
...
45.8 22.77 15.08 11.25 8.96 7.14 5.94 5 08 4.45 3.96 3.58 3.26 . 3.01 2.617 2.334 2.119 1.953 1.711 1.547 1.429 1.339 1.269
...
49.2 24.47 16.25 12.15 9.70 7.74 6.45 5.53 4.85 4.32 3.90 3.56 3.28 2.859 2.543 2.304 2,119 1.849 1.662 1,528 1.430 1.348
537
...
46.0 22.91 15.22 11.39 9.10 7.27 6.06 5.19 4.55 4.06 3.67 3.35 3.09 2.683 2.387 2.159 1.985 1.725 1.550 1.422 1.327 1.251
...
49.2 24.59 16.37 12.27 9.81 7.85 6.55 5.63 4.94 4.40 3.98 3.64 3.36 2.913 2.588 2.340 2.146 1.860 1.662 1 520 1.415 1.330 I
TABLE 11. PROPERTIES OF THE COEXISTING PHASES IN METHANE-PROPANE SYSTEM Pressure, Lb./Sq. Inoh Absolute
,Mole Fraction Methane Dew Bubble point point
Equilibrium Constants MethProane pane
Molal Volume, Cu. Ft./Mole Bubble point
Dew point
pressnre, Lb./Sq. Inch Absolute
Mole Fraction Dew point
A t 40' F. 79a 100 150 200 250 300
350
400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 1474b
0.0000 0.2034 0.4432 0.5627 0.6382 0.6875 0.7235 0.7505 0.7677 0.7819 0.7966 0.8042 9.8099 0.8135 0.8159 0.8180 0.8188 0,8199 0.8205 0.8208 0.8211 0.8214 0.8217 0.8220 0.8222 0.8222 0.8217 0.8173 0.7924 0.7459
0.0000 0,0099 0.0324 0.0549 0.0779 0,1008 0,1242 0.1471 0.1695 0.1923 0.2171 0.2378 0.2607 0.2834 0.3060 0.3289 0.3517 0.3769 0.3986 0.4226 0.4473 0.4719 0.4968 0.5225 0.5492 0.5773 0.6080 0.6434 0.6891 0.7459
0.0000
0.0000 0.0106 0.0321 0.0535 0.0749
20.55 13.68 10.25 8.19 6.82 5.84 5.10 4.53 4.07 3.67 3.38 3.11 2.870 2.666 2.487 2.328 2.175 2.058 1.942 1.836 1.741 1.723 1.573 1.497 1.424 1.351 1.270 1.150 1.000
1.0000 0.8046 0.5754 0.4627 0.3924 0.3475 0.3157 0.2925 0.2797 0.2700 0.2598 0,2569 0.2571 0.2602 0.2653 0.2712 0.2795 0,2890 0.2985 0.3104 0.3237 0.3382 0.3543 0.3728 0,3944 0.4208 0.4548 0.5123 0.6677 1.0000
63.0 49.7 32.8 24.37 19.31 16.08 13.42 11.54 10.10 8.93 7.93 7.15 6.55 5.93 5.45 5.02 4.62 4.28 3.96 3.67 3.41 3.14 2.921 0.2750 2.691 2.436 2.310 2,189 1.864 1.634
2.546 2.226 1.841 1.609 1.491 1.403 1.364 1.334 1.305 1.287 1.282 1.265 1.266 1.260 1.258 1.260 1.259 1.266 1.267 1.274 1.277 1.285 1.294 1.306 1.321 1.343 1.374 1.415 1.489 1.634
1,0000 0.8578 0,6787 0.5732 0.5039
38.5 31.9 23.76 18.87 15.58
1.819 1.724 1.592 1.512 1.468
At 70' F. 125" 150 200 250 300
0.1513 0.3435 0.4575 0.5338
14.27 10.70 8.55 7.13
Equilibrium Constants MethProane pane
- Methane
350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100 1160 1200 1250 1300 1350 1400 1434b
0.5853 0.6231 0.6501 0.6721 0.6908 0.7038 0.7141 0.7228 0.7300 0.7357 0.7403 0.7442 0.7471 0.7497 0.7520 0.7539 0.7553 0.7567 0.7570 0.7561 0.7503 0.7309 0.6772
189a 200 250 300 350 400 450 500 550 600 650 700
0.0000 0,0521 0.2184 0.3255 0.3949 0.4472 0,4884 0.5209 0.5481 0.5714 0.5911 0.6073
Bubble point
At 70' F. (Continued) 0.0959 6.10 0.4587 0.1168 5 . 3 4 0.4267 0.1372 4.74 0.4055 0.1580 4.25 0.3895 0.1782 3.88 0.3762 0.1987 3.54 0.3696 0.2196 3.25 0.3664 0.2407 3.00 0.3519 0.2616 2.791 0.3656 0,2828 2.601 0.3694 0.3042 2.434 0.3732 0.3261 2.282 0.3796 0.3481 2.146 0.3879 0.3707 2,022 0.3977 0.3938 1.910 0.4091 0.4179 1.804 0.4228 0.4425 1.707 0.4389 0.4679 1.617 0.4572 0.4954 1.528 0.4816 0.5244 1.442 0.5128 0.5670 1.338 0.5684 0,6046 1.209 0.6813 0.6772 1.000 1.0000 At
Molal Volume Cu. Ft./Mole' Dew Bubble point point 13.25
1.437
11.48 10.11 9,02 8.10 7.35 6.72 6.18 5.70 5.29 4.92 4.59 4.30 4.04 3.80 3.59 3.38 3.10 2.897 2.740 2.510 2.227 2.299
1.396 1.414 1.387 1.370 1.364 1.364 1.364 1.362 1.361 1.358 1.361 1.364 1.367 1,380 1.395 1.414 1.438 1.469 1,506 1.573 1.667 2.299
looo F. 10.63 8.50 7.08 6.06 5.29 4.70 4.22 3.83 3.61 3.25 3.01
24.54 23.19 18.60 15.52 13.29 11.59 10.25 9.16 8.26 7.50 6.86 6.30 (Concluded on
1.494 1.502 1.478 1.466 1.447 1.442 1.438 1.437 1.438 1.441 1.442 1.448 page 698)
INDUSTRIAL AND ENGINEERING CHEMISTRY
538
Vol. 42, No. 3
TABLE 11. PROPERTIES OF T H E COEXISTING PHASES IS ?V~ETHANE-~ROPANE S Y s T m r (Concluded) Pressure,
Lb./Sq.
Inch Absolut,e
750 800 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1353b
Mole Fraction Methane Dew Bubble point point
Equili hri u in Constants hIethane
Propane
At 100' F. (Cortiiniierl) 2 802 2 614 2,459 2,293 2.154 2.028 1,913 1.806 1.705 1. 604 1.500
1.359 1,088 1.000
Molal Volumc, Cu. Ft./Molo Dew Bublde point iioint
5.81 5.38 4.96 4.66 4.36 4.08 3.82 3.57 3.32 3.13 2.922 2.643 2.193 2.083
1.431 1.457
1,463 1,482
1.4f14
1.611 1,528 1,552 1.576 1. 606 1.680 1,730 1.968 2.083
At 130" F. 2744 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100 1150 1200 1218b
...
16.26 14.79 12.63 11.02 9.71
6.72 5.75 5.03 4:46 4.01 3.66 3.35 3.07 2.842 2.634 2.459 2.298 2.150 2.018 1,892 1.710 1.680 1.498 1.2.51 1 ,000
8.76
7.93 7.23 6.64 6.12 5.66 5.26 4.88 4.54 4.23 3.94 3.65 3.40 3.07 2.647 2.307
1.604 1 . 603 1.591 1.606
1 ,610 1,614 1,622 1 624 1.62(i 1.627
1.633 1 . 645 1, 6 3 1.670 1 . OS!) 1.712 1.743
700
750 800 850 900 950 1000 10206
10.70 10.24 9.02 8.80 7.23 6.56 5,98 5.47 5.00 4.59 4.19 3.82 3.44
, . .
4.61 4.00
3.59 3.23 2.912 2,707 2.188 2,293 2.110 1.939 1.757 1.349 1.271
E:;6
1,000
400
h
0.0000 0.0000 0.0280 0.0107 0.0798 0.0333 0.1208 0.05.55 700 0.1489 0.0786 725 0.1570 0.0926 750 0.1601 0.1120 767 b 0.1400 0.1400 Vapor pressure of propane Critical state.
2.'617 2.396 2.177 1.894 1.695 1.429 1.000
1.0000 0,9279 0,9519 0.9309 0.9237 0,9290 0,9458 1,0000
6.89 6.41 5.60 4.91 4.29 4.02 3.03 3.24
1.841 1.941 2,307
1 . 761
1 . 7G6 1.7b7 1 , 80fi
1.823 1.841
1,847
1 ,864 1.877 I 898 1 . 0:30 1 979 2 , OO? 2,933 2 . 5.i.j
2.06: 2 , 153 2.324
I W
PER SQUARE
INCH
1w.9
a t the unique states, including the state of maximum tcmpernture, the state of maximum pressure, and the critical state for this system at a number of even-valued compositions. These values, which result from interpolation of the experimental data, may involve uncertainties in temperature of as much as 2" F and in pressure of 25 pounds per square inch. A comparison of the present study with earlier measurements of the composition of coexisting phases has been madc in Tnhle IV a t five temperatures for several pressures. In each instance
TABLE Iv.
COllPARISOS O F I'ALUES O F COMPOSITION O F COEXISTIKG PHASES WITH TtESLILTS O F EARLIER IVORK Pressure, Lb./Sq. Inch Absolute
2,467
2.629 2.722 2.901 3.24
TABLE 111. PROPERTIES .4T UNIQUE STATES IX CRITICAL REGIONOF NETHANE-PROPANE SYSTEM Siaximum Temperature Maximum Pressure Critical State State State Composition, Pressure, Pressure, Pressure, Mole l$./sq. Tempera- lb./sq. Tempera- lb./sq. TemperaFraction inch ture, inch ture, inch ture, Methane E. abs. abs F. abs. B. 0.1 716 194.7 699 196.2 736 189.8 0.2 847 182.0 790 184.0 887 169.5 0.3 990 164.5 886 168.9 1036 148.5 0.4 1127 145.0 968 153.8 1192 123.7 1256 123.0 1043 136.1 1310 :l!),.j 0.5 0.6 1366 96.5 1120 115.5 1389 70.0 0.7 1451 60.5 1179 88.7 1468 45.3 0.8 .. .. .. .. 1200 54.6 .. ... 0.9 .. .. ...
..
mUNDI
Figure 3. Gas-Liquid Equilibrium Constants for Methane and Propeiie in Methane-Propane System
.it 1903 F. 525'1 550 GOO 650
e30 PiiESYlRE
1.784
A t 16OoP. 384a 400 150 500 550 600 650
V
200 400 GOO
800 1000 1200 200 400 600 800 1000 1200 400 600 800 1000 1200
Coinposition, 1Iole Fraction Methane Liquid Gas Present Earlier Present Ear1it.r (9)
At 70° F. 0.344 0.319 0.623 0,589 !).io4 0.675 0.136 0,715 0.760 0.730 0.7'57 0,728 At 1000 F. 0.043 0.439
0.032
0.417 0.671
0.632 0.064 0.878
0.565
0.619 0.641
0.635
At 130° I?. 0.241 0.250 0.411 0.414 0.494 0.496 0.546 0.525 0.513 0,492
A t 1600 F. 0.028 0.023
(9)
0,032 0,117 0.199 0.283 0.371 0,468
0.178
0.005 0.084 0.163 0.242 0.327 0,423
0.003 0.080 0.160 0.239 0.321 0.412
0.048 0.123
0.041 0.11R 0.195 0.280 0.412
0.201 0.288
0.410
0.026 0.099
0.261
0.348 0.417
0.249 0.353 0.361
0.006 0.081
0.162 0.280
0,006 0.082 0.166 0.297
At 190° F. 0.082
0,033
0.033
400 GOO 800 1000
0.239 0.341 0.356
600
0.080
March 1950
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
the composition of the dew-poilit gas and bubble-point liquid from each of the two sources is given. The standard deviation between the two sets of data is 0.020 mole fraction for the gas phase and is 0.013 mole fraction for the liquid phase. ACKNOWLEDGMENT
This paper is contribution from American Petroleum lnstitute Research Project 37,located a t the California Institute of Technology. Gordon Goff assisted with the experimental study and George Guill and Betty H. Kendall carried out the computations. LITERATURE CITED h
(1) Bridgernan, J . A m . Chem. Soc., 49, 1174 (1927). (2) Biidenholaer,Sage, and Larey, IND.END.~ I I E M . ,31, 369 (1939).
539
(3) Dana, Jenkins, Burdick, H I I ~T i t n n l , Refrigerating E~zcI., 12, 387 (1926). Burks, J. Am. Chem. See., 49, 1403 (1927), (4) Keyes ( 5 ) ~~~l~~~and Gad&, I b & f , 53, 394 (1931). (6) Michels and Nederbragt, Physica, 3, 569 (1936). (7) Olds, Reamer, Sage, and Lacey, IND. ENQ.CHEM., 35, 922 (1943). (8) Reamer, Sage, and Larcy, Ibid., 41, 482 (1949). (9) Sage, Budenholzer, and Lacey, Ibid., 32, 1262 (1940). (10) Sage, Kennedy, and Lacey Ibid 28 601 (1936). 136 (11) sage and Lacey, Trans. fi,ining ,,,,et. 136 (1940). (12) Sage, Lacey, and Schaafsnna, IND. ENG.CHEM.,26, 214 (1934) (13) Sage, Lacey, and Sohaafsma, OiE Gas J.,32, No. 27, 12 (19331. (14) Sage, Schaafsma, and Lacey, IND.ENG.CHEM., 26, 1218 (1934) (15) Vold, J. A m . Chem. Soc., 57, 1192 (1935). RICCEIVICD Julv 28. 1949. This is the 52nd aaaer of a series A bibliograptiy . . of the first 50 articles appears in IND. ENQ. CHEM.,41, 474 (1949); T h e 6 1 s t i s i n 1 ~ENG. ~ . Casx.,41, 2871 (1949).
km. ynst.’
Chromatographic Investigations of Smokeless Powder DERIVATIVES OF CENTRALITE FORMED IN DOUBLE-BASE POWDERS DURING ACCELERATED AGING W. A. SCIIROEDER, M.KENT WILSON’, CHARLOTTE GR KEN, PHILIP E. WILCOX2, RENE S. MILLS, AND KENNETH N. TRUEBLOOD* California Institute of Technology, Pasadena 4, Calif.
Chromatographic-spectrophotometric methods have been used to study the derivatives that are formed from centralite (1,3-diethyl-1,3-diphenylurea)during the accelerated aging of double-base smokeless powder. Approximately 40 derivatives were isolated and about one half of these were identified. Quantitative determinations showed that the two types of powders which were studied differed in the nature of the main derivative produced: In the powder that initially contained only 1% of centralite, 4-nitrocentralite was the main derivative,
whereas in that which contained 9% of centralite, N nitroso-N-ethylaniline predominated. These compounds and other important derivatives were determined quantitatively in samples of aged powder; more than 30 isolated derivatives were present only in minor quantity. A scheme has been proposed to explain the formation of the identified derivatives from each other. Quantitative determinations showed that more than half of the original content of centralite reacted in an unknown manner, probably with nitrocellulose and/or nitroglycerin.
T
nitro derivatives of centralite. Masaki (16) and Moisak (17) have obtained analogous results. LBcorchB and Jovinet (13-16) first attempted to determine and explain the reactions which centralite undergoes in stabilizing a powder. They believed that centralite is only an inert constituent of the powder until decomposition of the major constituents, the nitroglycerin and nitrocellulose, has produced traces of acid; then, in proportion to need, the centralite is hydrolyzed to N-ethylaniline which reacts with nitrous acid to form N-nitroso-N-ethylaniline while any nitric acid yields, a t least in part, mononitrocentralite. LBcorchB and Jovinet were able to isolate N-nitroso-A*-ethylaniline from heated powder in appreciable amount, but their detection of a “nitrocentralite” is less convincing. Although they believed that N-nitroso-4-nitro-AT-ethylaniline was also a likely derivative, they admittedly had no evidence of its presence.
HE centralites, or 1,3-dialkyl-1,3-diphenylurcas,were initially used in the manufacture of smokeless powder as gelatinizers for nitrocellulose and as deterrents for progressive burning powders. [In accordance with the convention of ChemicaE Abstracts, the term “centralite” is used to refer to 1,3diethyl-l,3-diphenylurea. Davis (IO) discusses other usages. 1 In 1926 Apard ( 1 ) suggested that the benzene nuclei in the molecule should permit it to react with the decomposition products of a powder and hence to act as a stabilizer. His experiments showed that nitrogen dioxide reacts vigorously with centralite to produce a mixture of compounds and that nitric acid alone or in mixture with sulfuric acid yields well-defined dinitro and tetraPresent address, Harvard University, Cambridge, Mass. Medical School, Boston, Mass. 8 Present address, University of Cltlifornis at Los Angeles, Lo8 Angel&, Calif. I
:Present address, Howard
