Solubilitv of Methane in n-Hexane

Solubilitv of Methane in n-Hexane J

E. P. SCHOCH, ARTHUR E. HOFFMAN", AND F. DREW MAYFIELD2 The University of Texas, Austin, Texas

220" F. and of the cyclohexane study (17) were obtained by using a second methane supply. The n-hexane mas the best grade listed by the Eastman Kodak Company and was not purified further. The index of refraction was found to be 1.3755 for nai as compared to the value of 1.37506 taken from the literature (4).

The solubilities of methane i n n-hexane corresponding to pressures u p to the critical and at temperatures of 100.27', 160°, and 220' F. are reported i n the form of bubble-point data. Specific volumes of the liquid phases, together with their compressibilities up to 6000 pounds per square inch, are given.

Results Table I presents the absolute densities of n-hexane a t 800 pounds per square inch. These densities were used in calculating the n-hexane injections into the equilibrium bomb. The value at 220' F. is taken from the data of Kelso (9); the absolute uncertainty of this figure is believed to be less than that of the values a t 100.27" and 160' F. determined by the authors.

N APPARATUS and experimental method for highpressure determination of P-V-T-X relations of twocomponent hydrocarbon systems were described previously, and bubble-point data were reported on the methanebenzene system (16) as well as the methane-cyclohexane system (17). Similar data are given here on the methane-nhexane system a t 100.27", 160", and 220" F. The experimental data consist of the determined solubilities of methane in n-hexane, together with the densities and compressibilities of the resultant solutions up to pressures of 6000 pounds per square inch. A number of studies have been reported previously on the methane-n-hexane system. Frolich and co-workers (6)measured the solubility of methane in n-hexane a t 77" F. and a t pressures as high as 1300 pounds per square inch with an estimated accuracy of * 5 per cent; no density determinations were made. In a study of the rates of solution of methane, Hill and Lacey (7) reported the solubility of methane in n-hexane a t 86' F. and 300 pounds per square inch. Sage, Webster, and Laccy (14) determined the solubility of methane in %-hexanea t temperaturesof loo", 16O0,and 220' F., corresponding to pressurcs as high as 2500 pounds per square inch. Only three compositions were studied a t each temperature and in each case densities of the solutions and their compressibilities up to 3000 pounds per square inch were reported. Bubble-point and dew-point densities and compositions a t temDeratures of 77". 131'. and 185" F..eorrespoiding to pressures u p to the critical pres4000 sures (2950 to 3370 pounds per square inch), cn were reported by Boomer and Johnson (9) rn a for the methane-nitrogen-n-hexane system 3200 E containing relatively small amounts of nitro0 cn gen; the methane supply employed was 94.4 per cent methane and 5.6 per cent nitrogen. 2400

A

TABLE I. ABSOLUTEDENSITIES OF HEXANE AT 800 POUNDS PER SQUAREINCH ABSOLUTE Temp.,

B.

Abs. Density Oran

Av. Abs. Density PET

cc.

0.6492, 0,0490

100.27 100.00

0.0491 0 6209 0.5876 (8)

0.6211, 0.0206

..........

220.00

The results of the bubble-point studies calculated from the experimental data are presented in Tables 11, 111, and IV. They show the bubble-point pressures, compositions, and specific volumes, together with the compressibilities of the liquid phases. For comparison, large-scale plots of bubble-point pressures as a function of composition and of bubble-point specific volumes as a function of composition were prepared from the data of Sage, Webster, and Lacey (14), of Boomer and Johnson (W), and of this paper. The deviations thus determined of the data of Sage, Webster, and Lacey and of Boomer and Johnson from those of this paper are presented in Table V. The data of Boomer and Johnson are on the methane-nitro-

a

Apparatus and Materials The apparatus and experimental method were described previously (16, f7). The methane purification method was used as previously reported (16). The 100.27' F. data of this paper and of the two previous papers (16,1 7 ) were obtained by using one methane supply. The data of this paper at 160" and 1 Present address, Humble Oil and Refining Company, Houston, Texas. 8 Present address, Phillips Petroleum Company, Bartleaf i e , Okla.

vj

m

.J

1600

J (r

m 3 EL

800

a

0 -300

-200

-100

0

100 200 TEMPERATURE,

300

400

500

600

O F

FIGURE 1. TEMPERATURE-PRESSURE PLOTOF LOCIOF CRITICAL STATESFOR TWO-COMPONENT SYSTEMS CONTAINING METHANE

ma

I N D U S T R I A L A N D ENGINEERING CHEMISTRY

May, 1941

.

T ~ L 11. E SPECIFICVOLUMEE OF MIXTURESOF METHANIO AND WHEXANEAT 100.27" F. (RUN1) Abs. Abs. Abs. Pressure Sp. Vol., Pressure Sp. Vol., Pressure Sp. Vol., Lb./Sq. Ih. Cu. Ft./Lb. Lb./Sq. Ih. Cu. Ft./Lb. Lb./Sq. I & Cu. Ft./Lb.

689

* VOLUMIOS OR MIXTURESOF METHANE AND TABLE 111. SPECIFIC +HEXANE AT 160.00"F. (RUN1) Abs. Abs. Abs. Pressure Sp Vol. Pressure Sp Vol., Pressure Sp Vol Lb./Sq. Ih. Cu. F t . / i b . Lb./Sq. Ih. Cu.'Ft./Lb. Lb./Sq. Ih. Cu.'Ft./ib,

78.22 Mole %, 40.06 Mass % Methane

74.01 Mole $6, 34.65 Mass yo Methane

69.97 Mole %, 30.25 Mass % Methane 6000 0.03338 5500 0.03380 5000 0.03425 4500 0.03477 4000 0,03539 3500 0.03617 3300 0.03654 3100 0.03694 3000 0.03715 2900 0.03737 2800 0.03761 27440 0.08775 2705 0.03825 2680 0.03860 2628 0.03929 2577 0.03999

76 53 Mole yo 37 78 Mass % Methane 6000 0.03870 5500 0.03859 6000 0.04080 4600 0.04186 4000 0.04343 3500 0.04557 3300 0.04668 3200 0.04729 3100 0.04800 3000 0.04878 2940 0.04930 29140 0.04934 2886 0.05009 2868 0.05045 2831 0.05117 2777 0.05225

73.51 Mole yo,34.06 Mass yo Methane



57 58 Mole 20.17 Gass % d t h a n e

52,:s Mole % 16.88 Mass % Methane

63.73 Mole yo,24.65 Mass yo Methane

57 16 Mole yo 19.90 Mass % Methane

61 67 Mole % 16.60 Mass % Methane

-

-_.

2400 2300 22730 2245 2227 2190 2172

0.03215

2560 24270 2396 2354 2297 2242

0.03226 0.03230 0.03265 0.03289 0.03335 0.03359


37.43 Mole %, 10.02 Mass yo Methane


18.29 Mole g 4.00 Mass % MetLane

30.30 Mole %, 7.49 Mass yo Methane 6000 0.02550 5500 0.02563 6000 0.02577 4500 0.02591 4000 0.02006 3500 0.02621 3000 0.02G38 2500 0.02655 2000 0.02675 1500 0.02700 1400 0.02705 1300 0 02711 1200 0 02716 1088" 0.02722 1078 0.02738 1065 0.02756 1052 0.02773 1030 0.02809

5 Denotes bubblepoint state. All values below bubblepoint state are in the two-phase region.

gen-whexane system corresponding to relatively low nitrogen contents. Since these data were reported for 77", 131°, and 185O F., interpolation was necessary. Table V reveals that the bubble-point pressures of Boomer and Johnson are consistently higher than the bubble-point pressures of this paper. These higher pressures are to be expected because of the presence of appreciable quantities of nitrogen in the gas phase. The good agreement between the specific volume data of the two papers i e the lower bubble point pressure range is not surprising since the nitrogen con-

0.03463 0.03477 0.03520 0.03577 0.03654 0.03730


37 19 Mole 7 ' 9 93 Mass % M s h a h e

22 03 Mole % 5.00 Mass % Methane

15.68Mole %, 3.35 Mass % Methane

30 37 Mole Yo 7 51 Mass % Methahe 6000 0.02641 5500 0.02658 5000 0.02676 4500 0.02686 4000 0.02717 3500 0.02740 3000 0.02766 2500 0.02792 2000 0.02823 1600 0.02850 1500 0.02857 1400 0.02864 1300 0.02872 12050 0.02880 1189 0.02812 1174 0.02942 1159 0.02971 1146 0.03000

a Denotes .-. . . bubble.- .... point state. All values below bubblenoint state are in the cwo-phase region

tent of the liquid phases is relatively low in this range; in the higher bubble-point pressure range, however, the nitrogen contents of the liquid phases become appreciable and the specific volumes correspondingly larger. The agreement of the data of this paper with those of Sage, Webster, and Lacey is fairly good, with the exception of the bubble-point pressures corresponding to the 56.07 mole per cent methane mixtures reported by Sage, Webster, and Lacey at all three temperatures. The data of Tables 11,111, and IV indicate that the critical

,

690

INDUSTRIAL AND ENGINEERING CHEMISTRY

Vol. 33, No. 3

TABLEIV. SPECIFICVOLUMESOF %-HEXANE .\'P Abs. Pressure Sp. Vol. Pressure Sp. Vol. Lb./Sq. Ih. Cu. F t , / i b . Lb./Sq. Ih. Cu. Ft./Lb. 75.49 Mole %, 36.44 68.05 Mole yo,28.39 Mass To Methane M a s s % Methane 6000 0.04188 6000 0.03679 5500 0.04300 5500 0.03759 5000 0.04437 5000 0.03850 4500 0.04611 4500 0.03960 4000 0.04836 4000 0.04098 3500 0.05142 3500 0.04285 3100 0.05493 3000 0,04550 3000 0.05603 2900 0.04621 2900 0.05721 2800 0.04699 2800 0.05849 2730 0.04761 2753a 0,05912 26S2a 0.04804 2725 0.08976 2647 0.04877 2704 0.08021 2610 0.04948 2666 0.06113 2573 0.05020 2647 0.06158 2538 0.05092

Abs.

44.07 Mole yo, 12.79 M a s s % Methane 6000 0.02972 5500 0.03004 5000 0.03039 4500 0.03079 4000 0.03124 3500 0.03174 3000 0.03235 2500 0.03308 2300 0.03344 2200 0.03364 2100 0.03384 2000 0.03404 1900" 0.08425 1877 0.03463 1857 0 03495 1827 0.03544 1806 0.03577


WEIGHT PERCENT METHANE

FIGURE 2. BUBBLE-POINT PRESSURE-COMPOSITION DIAGRAM AT 100.27" F., SHOWING EFFECT OF STRUCTURE OF SOLVENT ON

SOLUBILITY OF METHANE

state for the methane-n-hexane system corresponding to a maximum critical pressure exists a t a temperature somewhere between 100" and 220" F. just as in the case of the methanecyclohexane system (17). This is clearly shown in Figure 1. Critical states of the methane-ethane (6, I l ) , methanepropane (IS), methane-n-butane ( l a ) , methane-n-pentane (I??), and methane-cyclohexane (17) systems are plotted in Figure 1 together with critical states of the methane-nhexane system. In some cases these critical states were determined graphically by bubble-point pressure-composition isotherms. This is possible because the maximum pressure on such an isothermal plot corresponds to the critical state for that temperature. The vapor pressures and critical states of the pure compounds plotted in Figure 1 were taken from the literature ( I , 3,8, 16). The effect of structure of the solvent on the solubility of methane is shown clearly in Figure 2 where the solubilities at 100.27" F. of methane in n-hexane, in cyclohexane (l7), and in benzene (16) corresponding to different total pressures are plotted. It is important to note the relative solubilities of methane in these typically paraffinic, naphthenic, and aromatic hydrocarbons, the methane being most soluble in the paraffinic hydrocarbon and least soluble in the aromatic hydrocarbon. Figure 3 shows the effect of composition on the bubblepoint molal volume of the methane-n-hexane system a t three temperatures. The almost straight-line function in the lower methane concentration range should be noted. At each temperature the bubble-point molal volume passes through a minimum before each corresponding critical state is reached. The molal volumes of pure n-hexane under its own vapor pressure a t each temperature plotted in Figure 3 were taken from the literature (IO). A comparison of the bubble-point specific volumes as a function of composition a t 100.27" F. is given in Figure 4 for

FIGURE 3. EFFECT OF COMPOSITION ON BUBBLE-POINT MOLAL VOLUME FOR METHANE+-HEXANE SYSTEM

INDUSTRIAL AND ENGINEERING CHEMISTRY

May, 1941

MIXTURESOF METHANEA N D

a

TABLE v. DEVIATIONS O F RESULTS OF OTHER INVESTIGATIONS OF METHANE--~-HEXANE SYSTEM FROM DATAOF THIS P.4PER

220" F. (RUN1)

Abs. Abs. Pressure Sp. Vol. Pressure Sp. Vol., Lb./Sq. Ih. Cu.F t . / i b . Lb./Sq. in. Cu. Ft./Lb. 59.64 Mole %, 21.57 51 30 Mole % 16.40 Mass % Methane Mass % Methane

28 7 5 Mole ?' 6 99 M a s s % Meehahe 6000 0.02760 5500 0.02783 5000 0.02806 4500 0.02832 4000 0.02861 3500 0.02892 3000 0.02927 2500 0.02967 2000 0.03013 1600 0.03057 1500 0,03069 1400 0.03081 1300 0.03094 1195a 0.03109 1187 0.03130 1174 0.03157 1160 0.03193 1150 0.03220

691

16.48 Mole yo.3.64 Mass yo Methane eooo 0.02636 5500 0.02654 5000 0.02671 4500 0.02692 4000 0.02714 3500 0.02738 3000 0.02764 2500 0.02793 2000 0.02825 1500 0.02861 1000 0.02904 900 0.02913 800 0.02923 730 0.02931 673' 0.02937 870 0,02950 664 0.02964 660 0.02977 658 0.02991

Temp.,

' F.

0 Denotes bubblepoint state. All values below bubblepoint state are in the two-phase region.

100

Workers Sage. Webster, and L a w (14)

100

Boomer and Johnson nitrogen present

160

Sage Webster, and d o e y (1.1)

160

Boomer and Johnson nitrogen present

220

Sage Webster, and L&ey (14)

(a),

Mole % Methane 19.21 43.04 56.07 15.00 25.00 2.5 no ._...

45.00 53.00 65.00 71.50 19.21 43.04 56.07 15.00 25.00 35.00 45.00 53.00 66.00 71.50 19.21 43.04 66.07

Yo Deviation BubbleBubblepoint point pressure SD. vol. - - 0 2 i o 2 +0.7 +O 5 4-9 6 -1 4 +3.8 -0.9 t6.6 -0 8 1, _ x 4 -n4 +9.4 -0.1 +10.5 +0.3 +2.3 ... +4.2 10.8 +1.6 -0.7 +1.1 +6.4 -0.5 4-7.2 -0.3 +6.3 +0.2 f8.2 10.2 +7.1 f0.8 +6.7 4-1.5 f3.3 4-6.4 4-1.0 +0.8 +0.2 -0.1 +5.4 -1.9

...

... ...

the methane-n-hexane system, the methane-cyclohexane system (I?'), and the methane-benzene system (16). The specific volumes of the pure hydrocarbons under their own vapor pressures were taken from the literature (10). The inflection points in the bubble-point molal volume isotherms are not fii n d in the bubble-point specific volume isotherms,

Acknowledgment The authors are indebted to the Humble Oil and Refining Company for a fellowship grant to A. E. Hoffmann.

Literature Cited A.,Simard, G. L., and Gouq-Jen Su., J. Am. Chem. SOC.,61, 24, 26 (1939). (2) Boomer, E. H., and Johnson, C. A., Can. J . Research, B16, 328 (1938). (3) Deschner, W. W.,and Brown, G. G., IND. EXQ.CHEM.,32, 836 (1940). (1) Beattie, J.

(4) Egloff, Gustav, "Physical Constants of Hydrocarbons", Vol. 1, p. 36, New York, Reinhold Publishing Corp., 1939.

(5) Frolich, P. K., Tauch, E. J., Hogan, J. J., and Peer, A. A., IND.ENQ.CHEM.,23,548 (1931). (6) Guter, M.,Newitt, D. M., and Ruhemann, M., Proc. Roy. SOC. (London), A176, 140 (1940).

(7) Hill, E. S., and Lacey, W. N., IND. ENQ.CHEM.,

,

26, 1324 (1934). (8) International Critical Tables, Vol. 111, New York, McGraw-Hill Book Co..1928. (9) Kelao, E. A.,with Felsing, W . A., J. Am. Chem. SOC.,62, 3132 (1940). (10) Landolt and BBrnstein, Physikalisch-ohem-

ische Tabellen, 5th ed., Vol. 1, Berlin, Julius Springer, 1923. (11) Ruhemann, M.,Proc. Roy. SOC. (London), A171, 121 (1939). (12) Sage, B. H., Hicks, B. L., and Lacey, W, N., IND. ENO.CHEM.,32, 1085 (1940). (13) Sage, B. H., Laoey, W. N., and Schaafsma, J. G., Ibid., 26, 214 (1934). Webster, D. C . , and Lacey, W. (14) Sage, B. H., N.,Ibid., 28,1045 (1936). (15) Ibid., 29, 1188 (1937). (16) Schooh,E. P., Hoffmann,A. E., Kasperik,A.S.,

Lightfoot, J. H., and Mayfield, F. D., Ibid.,

WEIGHT

PER CENT METHANE

FIGURE 4. EFFECTOF COMPOSITION ON BUBBLE-POINT SPECIFIC VOLUME FOR TWO-COMPONENT SYSTEMS AT 100.27" F.

32,788 (1940). (17) Schooh, E.P., Hoffmann, A. E., and -Mayfield, F. D.. Ibid.. 32. 1351 (1940). (18) Taylor, H. S.. Waid, G . W., Sage, B. H., and Lacey, W. N., Oil Gas. J.,38, No. 13, 46 (1939).

Solubilitv of Methane in n-Hexane

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