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
482
Vol. 41, No. 3
ACKYOWLEDGBIENT
TABLEIT'.
COl\IPARISOh- O F RESCLTSO F ISVESTIG.4TIOXs
A.
Mole Fraction n-Butane
0.1391 0.2898 0,3927 0,5449 0.6239 0.8607
0.1391 0.2898 0.3927 0.5449 0.6239 0.8607
Temp.,
F.
99.9 110.0 120.7 151.0 100.2 160.5 131 . o 172.8 120.2 160,s 200.0 121.0 160.3 230,s
Experi niental Mixtures Poettiiiann a n d Kati! Pressure Lh./Sq. In. -4bs. Dew Bubble point point 505 609 278 445
133 363 162 298 111 209 3 52 77 144 340
DIFFERENT
A11thors Pressure Lh./Sq. In. Abs. Dew Bubble point point
976 1066
473
987
576
1090
925 1139 665 1025 715 915 545 683 840 269 355 565
280 460 143 368 161 294 118 210 355 82 144 330
978 1162 723 1090 728 931 578 752
B . Critical Behavior Poettmann and Katz Temp., Pressure, ' F. l h j s o . in. abs. 119.5 1122 169.0 1181 203.0 1140 233.5 1077 254.0 940 288.8 709
916
274 363 563
Authors Temp., Pressure, O F. lb./sq. in. ahs. 119.0 1133 160.8 1186 190.8 1167 231.2 1050 248,7 965 287.2 704
tangent to the critical locus a t this maximum two-phase pressure of the system. The influence of temperature upon the compressibility of the dew point gas and bubble point liquid of the five mixtures experimentally investigated is shown in Figure 5. At temperatures below 250" F. the conipressibility factor for a mixture of carbon dioxide and n-bubane containing 0.8273 mole fraction n-butane ia great,er than the corresponding compressibility factor for pure n-butane a t the same temperatiire. The loci of the critical, cricondentherm, and the point of maximum pressure have been included.
This work was carried out as a part of the activities of Project 37 of the American Petroleum Instituk. The financial support o i this organization has made the prosecution of this work posaible. The assistance of Dorothy Chamberlin arid Paul S. Farrington in connection Tl-ith the laboratory work is acknowledged. NOMENCLATURE
f
fugacity, pounds per square inch K equilibrium constant n = mole fraction P = absolute pressure, pounds per square inch R = universal gas constant, 10.732 (lb./sq.in.) (cu.ft./lb./mole) = =
R. T = absolut,e temperature, R., 459.69 F. V = partial molal volume, cubic feet per pound mole = residual partial molal volume, R T / P cubic feet, per pound mole X = mole fraction in liquid phase Y = mole fraction in gas phase
+
O
~~
vy
SUBSCRIPT k = indicates coniponent k; LITERATURE CITED
(1) (2) (3) (4) (5) (6)
(7) (8) (9) (10)
(11) (12) ,
BeaLtie. Sirnard, and Su, J . Am. C h e m . Soc., 61, 24 (1939). Bridgeman, I b i d . , 49, 1174 (1927). Caubet, 2 . physilz. C h e m . , 40, 257 (1902). Kuenen, Phil. M a g . , 44, 174 (1897). Kuenen, Z . p h y s i k . C h e m . , 24, 667 (1897). Kuenen arid Robson, P h d . X U O 4, . , 116 (1902). Michels and Michels, Proc. R o y . SOC. (London), A153, 201 (1935). I b i d . , A160, 348 (1937). Olds, Reamer, Sage, and Lacey, IND.ENG. CHDM.,36, 282 (1944). Poettmann arid Katz. I b i d . , 37, 847 (1945). Roozeboom, "Die heterogenen Gleichgewichte," Yo]. 11-1, p . 288, Braunschweig, 1904. Sage and Lacey, Trans. Am. Inst. Ml.lining M e t . Engm., 136, 136 (IQ-IO),
RECEIVED Noveniber 17, 1947.
VOLUMETRIC BEHAVIOR OF PROPANE H. H. REAMER, B. H . SAGE, AND W.N. LACEY California Institute o f Technology, Pasadena, 4,Calif.
P
ROPAKE is one of the important compoiientn of natural gas and is useful as a startirig material for the preparation of a number of organic cornpouiids of industrial interebt. For thiv reason it is desirable to linoiv Tvith some accuracy the influence of temperat,ure and pressure upon the molal volume of this hydrocarbon. The volumetric behavior of propane has been studied by a number of investigators. Dana and co-Ivorkers ( 5 ) xnea,sured it,s vapor pressure and the volume of bubble point liquid and dew point gas a t temperatures from approximately -50" t o 130" F. Later studies in the authom' laboratory (11) gave valueh of the vapor pressure up to the critical state and the volume of the liquid and gas a t temperarures below 250" F. from approximately
50 to 3000 pounds per square inch absolute. Beattie, I'offenberger, and Hadlock (2) studied carefully the behavior of propane at reduced states near unity, and from these measurenierits obtained values of the pressure, temperature, and volume corrcsponding to the critical state. These values of the critical pressui'e and temperature have been used in the present work because they are more accurate t,han the earlier measurements ( 1 1 ) . Bcattic and eo-workers ( 1 ) also studied the influence of pressure and temperature upon the volume of propane a t temperatures up t o 525" F. and for volumes from 1.59 to 16.01 cubic f w t pcr pound mole. The prcsent work was uiidortnken in order t,o obtain more
March 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
adequate vapor pressure data and to extend the upper limit of the pressure range. The directly measured volumetric information is supplemented by values for the Joule-Thomson coefficient below the vapor pressure for temperatures between 70" and 220" F. (9). These latter data are particularly useful in establishing the change in molal volume with temperature a t states corresponding to the lower pressures for nhich direct volumetric measurement is uncertain because of adsorption. EQUIPMENT AND METHOD
The equipment utilized in this study has been described in some detail (10). In principle it consists of a stainless steel chamber within which a known quantity of hydrocarbon was confined. The effective volume was varied by the introduction or withdrawal of mercury and the resulting equilibrium pressure was measured. The quantity of mercury added to the equilibrium chamber was established from the change in elevation of a mercury-air interface within a n interconnecting vessel. The weight of sample introduced w-a~determined by weighingbomb techniques ( I O ) and after completing a set of isotherms the propane was withdraan. A comparison of the weight of material added and later withdrawn showed agreement within 0.03% in all cases. The weight of sample and the accuracy of the volumetric measurements were such that the measured specific volume at a given state probably did not involve uncertainties larger than 0.27& The pressure was measured by a balance based upon a piston-cylinder combination ( I O ) . This equipment was calibrated against the vapor pressure of carbon dioxide a t the ire point (5). The weights used in the balance were consistent with one another within 0.002%. It is believed that the pressure a t equilibrium was measured within the larger of either 0.1 pound per square inch or 0.05%.
T h e influence of pressure -and temperature upon the molal volume of propane was determined at nine temperatures between 100 O and 860' F. and for pressures from 10,000 pounds per square inch absolute to vapor pressure, or above the critical temperature to pressures as low as 650 poundsper square inch. The volumetric measurements were smoothed with respect to pressure and temperature, and the results are tabulated. They are compared with those of earlier investigators.
483
484
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
The temperature of the equilibiiuiii v 1 mas controlled by inirnerrion in an agitated oil bath and provi,sion as made to minimize thermal gradients in the tubing which connected this vessel with equipment outside the bath. T h e temperature of the oil bath !$as measured with a -ti ain-fi ee platinum resibtance thermometer which was compared at periodic intervals with the indications of a standardized instt ument. In addition, the resistance of the service thermometer at the ice point \$as checked a t frequent intervals. -4ttainment of thermal and phase equilibrium waq accomplished rapidly b r mechanical agitation M ithin the u orliing vessel. This was provided by means of a spiral agitator (10) rotated aiound the majoi axis of the %esse1by a c e t of externally mounted electromagnet\. ;2lter intioducing a lrnown 7%eight of propanc, the piebbure m ithin the apparatus n as raised to slightlv above 10,000 pounds per syueie inch absolute and t h c system s a 3 brought t o equilibrium. The total volume occupied by the hydrocarbon, th(1 piessure, and the temperatuic T T C I ~then nieaiuied The total volunie TI a- increased, equilibrium !vas re-estahlished, and the measurements were repeated This procrtlurc ags continued throughout the single-phase region. After incawling t h e vapoi piessure at several total volume5 of the h v t r n i , the tempeiatuic was raiwd to the nest higher piedcterniinrd value and the scquerice mas repeated. Upon completion of studieb a t 460" F. a set of check measurements nas made a t t h e initial tcmperai ure .tudird These initial and final mrasiircnientc agreed n ithin 0 17. Residual techniques were rmplm etl \there advantageon4 in crnoothing the experimental (lata. 'VI4TLKIAL AhD EXI'LKIMEh'I'AL RE5tIL'rS
'l'iic propane used in thew iiive+tigationrw a i obtained I i om thfa Phillips Petroleum Companv. The material as supplird contained le- than 0 1% of impiiritir3 It was subjected to a fraciioiiation a t a reflux iatio or appioximatc>lv 10 to 1 111 a column packed with glass rings. The initial and final tcnthg of thr overhead Rere discardzd in thr couise of the fractionatioii. The purified material shovc-ed lets tliati 0 2 pound per qquai P inrli vuiiation in vapor pressure at 100" F. when changed from bubble point to a .late in which more than half of the proparie w a i in the The purified hydrocarbon wa3 itored in m a l l atairiless steel ront:iincri from i\liich i t T Y R . ~trariiferrcti directly into thr equilibrium vrssel. The experimental reaults after inieipolatiori t o ~ 7 7 ~ 1values 1 of pre-suie are recorded in Tahle 1 For each of thr rqxrimeiitallv Ftudied temperatureq. 4 molecular weight equal to 44.095 wa-r used in the calculation^. Foi coiivenic~ricetlie data are givcn in teiinc both of the compressibilitv factor, %, and the molal volumt', T'. ,4t temperatuies of 250" F. and higlicr for pressurz; heloa 2000 pound3 pel square inch the dxta werc smoothed and inferpolatcd by the use of thc rcsidual molal .r-olume, E. AAt loir ~r temperatures the molal volurne~ in tlie 4a5c~ou~ region nere e,tablishrd bv methods that have b w n de*ctihrd ( 8 ) and M hich involved the ube of t h r Joule-Thoriison coefficitmt (9) and the heat eapacitv at atniosph~~rir p w s w ~ c( 7 ) In this c a v the changcx iii the comprcsqibility fsctor nith tempeiature w , ~ calculated by integration ot the follon ing equation, using the directly mearurcd volumetric d a h a t 250°F. a s a ha&:
Sc'm the critical state the I ,urcnieiiis of Btwtio aiitl co-worlrcrs ( 1 , 2) were utilized. P iollon-ing values for tlw critical constants of propane wcryn talccn for this n-orlr : presure, 617.4 pounds per squ inch; ternperature, 206.3" I?.; arid volume, 3.202 cubic fcit pr:~inole T h s critical pIpssurr%and tcmpc,rature were talcen d i l e c t l ~from Beattie's nicaiiurernentij ( 2 ) wtiercas thc critical volume was obtained by extrapolation of t h c average demit?; of the corsisting gar m d liquid phases to 1210 criticnl temperature. This v d u c is upgroximatcly 2.7%) greater than that obtained e, b u t a g r e ~ within ~ 0.55% uith the value of 3.220 cuh r mole rccerit.ly established tn: hI\-crs (4 1 frcim Beai ticx's A t l c t R i l c d roniparison of
TABLE
11.
PROPERTIES
Vol. 41, No. 3
O F P R O F A N E DEW P O I N T
RUBBLEPoIur LIQUID DCW Point __ Molal V . it./ . cu. mole, Z, (satd.
GAS
AND
Bubble Point -~ Molal V ,
_ _ I _
Prewiiw, Lh./Sq. In. Bbs. 200
Temper-
ature, O F. 104.6
250
8OU 350 400 460 500 550 600
124.4
138.0 151.6 163 F)
I
17.5.2 1tI5.2 194.8 203.4
sad
23.048 18.09ti 14 ,578
11.866 10.129
8.567 7.232 6.017 4 . ti87 3,202O
617.4a 206.3" Critical constants. critical state.
(satd. gar)
0 . 7 618 0.7217 O.fi81R 0.6330 0 ,R O i ? 0.56.58 0.6223 0.4711 0.3953 0.2786
CII.
ft./
m olii , (satd. liri.iid) 1.5111 I . 5808
I.6395 1,7063 1.7863 1 ,8807
1.9949 2,1457 2.4173 3,202'L
z,
(satd. liquid) 0.0499 0.0630 0.07fi7 0.0910 0 IO68 0,1243 0 1441 0 ,lfi80
0,2038 0,2788
L1
the present meaqurementq d h the datu of Beattie ( Y ) R t pie.s i m i and temperatures removed ti om the critical state shows unusually good agreement. The average dwiation of the two scts of data for approx;mately 50 states is 0 22%. The maximum deviation encountered was lesi: than 0 4% Tlie valurs of ~
tho vapor pressure of propant. recorded in Table I are based on pres-nt meawrements and agree well Rith the work of Benttie ( 1 ) . For convenience Table TI presents values of the tmo-phase tenipei ature corresponding t o a set of syctcinatically chosen pressures. The assoriatcd values of the molal voluinc and the compressibilitv €actor-, of dew point ?is and bubble point liquid also are recorded in this table. The volumes of the dew point gas were obtained by two methods. One depended upon thc Clapeyron equation ( 4 ) using the recorded vapor preasure and buhblc. point volume data of Table I and measured v a l u e of the latent heat of vaporization (8). In the second method volumcs for the dew point gas were computed from Joule-Thom5011 mensureincnts and the directly mcmiired volurnotric datw a t 250" F T'n1ut.s obtaincd bv t h c two methods agreed ivithin 0 39;. ACKNOWLEDGMENT
Thi- paper i, a contribdtion from Zmerican Pctroleuni Iriatii utc Rcscarch Project 37, located at thr- Cnlifornia Institute of Techuology, J. W. Glariville and G. P. Guill awistcd materiallv with the expwiniental mrasurcment. and the associated calculations LITERATVRE CITED (1) Beilttie, Ka.v, a n d Kaininsky. J. A m . Chim. Soc., 59, 1589 (1937) (2) Beattie, Poffenberger. arid Hadlock. J . Chem. Phus., 3, 96 (1935). (3) Bvidgeman. , J . Am. Chem. Soc., 49, 1174 (1927). (4) Clapeyron, J. &colep o l i l i ~ c h . 14 , ( 2 3 ) , 153 (1831). (5) Dana, Jenkins, Burdick, arid Timm, R e f T i g . Eizg.. 12, 387 (1926). ~ (6) M ~ w h J, . Research YatZ. BW. Standards, 29. 168 (1942). (7) Rossiiii, special publications of Natl. Bur. S t a n d a d s , A m .
Petlroleurn Ttist. Proieot 44 HEX., 31, 7 6 3 (1939). (8) Sage, Kvans, and Lacel.. IND. (9) S ; i g ~Kennedy, , and Lace,., I b i d . . 28, 601 (1936). ( I O ) Sage and Lncey, Trans. -4m. fnst. Jdinirry/ M e t . E n ~ r s . ,136,136 (1940). (11) Sage, Schanfsma, arid I.nrey, 1x1).F:sc. CHEAT., 26, 121.8 (19341,
. In the article on "liquid-Vapor Equilibriuin nary Systenis" 1 1 ~Kxc. ~ . c H J , x . ,40, 1463 (1.948)l m u l e in Idxlirig the two lorve1* curves of Figure 7, The curve with Ihn rimximuin slightly over 200 is for t h e ethanen-butitnc s y s t ~ mand the curve wi th the maximum slightly aliove 100 is for the rz-butane--?~-hcrl)ta~i~ syitcrn. B. K A Y
w.
