BINARY VAPOR-LIQUID EQUILIBRIA OF CARBONDIOXIDE-LIGHT HYDROCARBONS AT LOWTEMPERATURE*

Kunio NAGAHAMA,Hitoshi KONISHI**, Daisuke HOSHINOand Mitsuho HIRATADepartment of Industrial Chemistry, Tokyo Metropolitan University,Tokyo

Vapor-liquid equilibrium data for binary systems containing carbon dioxide: CO2-C2H6,CO2-C3H8, C02-fl-C4Hio, CO2-/M-C4H10, CO2-C2H4, CO2-C3H6 and CO2-l-C4H8 were

determined by the vapor recirculation method in the low-temperature range (-41.6°C-0°C).The CO2-C2H4and CO2-C2H6systems formed minimum-boiling azeotropes. The modified

Redlich-Kwong equation of state was used to calculate vapor-liquid equilibria of these systems.It provided fairly good agreement with experiment.

The vapor-liquid equilibrium of carbon dioxide-

light hydrocarbons at low temperatures is of interestin the design of the proper equipment to make suchseparations. In the previous paper4) of this series,the equilibrium relationships for two binary mixturesof carbon dioxide with ethylene and ethane at 0°Chave been described. Those for the ethylene and

ethsine binaries with carbon dioxide have been shown toform, minimum-boiling azeotropes.Wehave therefore extended the work to include

mixtures of several hydrocarbons with carbon dioxide.The present paper provides the results of experimentalinvestigations of the equilibria in binary systems ofcarbon dioxide with four light paraffins, i.e. ethane,propane, ^-butane and isobutane, and with threelight olefins, i.e. ethylene, propylene and 1-butene inthe low-temperature range (-41.6°C-0°C). Suchmixtures are of general interest for two reasons.

First, the phase behavior of binary mixtures of carbondioxide and light hydrocarbons has been investigatedin somd detail since the measurement of Kuenenn)in 1897, but there have been few vapor-liquid equi-libria stiidied in the low-temperature range. Of more

interest is the fact that these binaries do differ mark-edly in phase behavior from hydrocarbon systemsbecause of the significant quadrupole moment ofcarbon dioxide as well as weak acid-base complex

formation with hydrocarbons12} and such complicatedbehavior prevents us from calculating phase equilib-rium with Un aid of the equation of state.

Comparison of the experimental data with theresults calculated by using the modified Redlich-Kwong equation9>16) of state was made, and it ap-

peared to provide a fairly good representation of theexperimental data for each binary system.

Experimental Apparatus and MethodsThe apparatus was the vapor-recycle type describedin detail by Hakuta et al.5). Small changes were madein maintaining a constant low temperature of the bathusing liquid nitrogen as the refrigerant.A schematic diagram of the apparatus is given in

Fig. 1. The gaseous materials were charged into theglass-windowed equilibrium cell. Vapor recirculationwas carried out by means of a specially designeddouble-acting magnetic piston pump. Vapor was con-tinuously removed from the top of the equilibriumcell and reintroduced at the bottom, where vaporbubbled up through the liquid to establish vapor-liquid contact. After the system was allowed to

remain at desired temperature and at constant pressurefor at least half an hour, samples of 10 m/ from vapor-phase were isolated in the sampling cell between twoneedle valves attached to the recirculating line,

1 . Eq u ilib r ium Ce ll

5 0 0

8

2 . Th erm oc ou ple (co pp er- con sta nta nt an )G I / r 3 . Va por P has e S am pl ing Ce ll

H . L iqu id Pha se Sam pl ing C ell

12

5 . Ma gne tic P ist on Pum p6 , Sam pl e G as Cy lin df r7 . B o urdo n Pre ss ure Ga gei. T em per at ure D ete cto r

9 . Liq uid N itr og en T he rmo s B ot tl e10 , C om pre ss ed Nit rog en Cy ill . C ons ta nt Tem pe rat ur e B ath12 . O n-O ff Co nt rol Va lve

g : t o Gas c hr oma tog ra phv : t o V ac uum P ump

2u

10

V

9

6n

Fig. 1 Schematic diagram of vapor-liquid equilibrium

apparatus

* Received on January 31, 1974Presented- in part at the 36th Annual Meeting of The Soc. of

Chem. Engrs., Japan, April 3, 1971** Japan Gasoline Co., Ltd., Yokohama=fi58 Mj?Mwm&&m:{R2-i-i

VOL 7 NO. 5; 1974 323

Table 1 Column condition of gas chromatograph

Sy ste m L en gth Pa cki ng F low ra te[m ] [m //m in]

Carbon d ioxide-Eth ane 1.8 Polapac Q 40Carbon dioxide-Propane 1.0 silica gel 70Carbon dioxide-ｫｰButane 0. 5 silica gel 60Carbon dioxide-iso-Butane 1.0 silica gel 60Carbon dioxide-Ethylene 1. 8 Polapac Q 32Carbon dioxide-Propylene 0. 7 silica gel 120Carbon dioxide-1-Butene 0. 5 silica gel 100

Table 2 Purity of materialsCarbon dioxide 99. 8E t h a n e 99 . 0 % m i n .Pro pan e 9 9. 85 % min .n- Buta ne 99 . 35 % mi n.ｫ0-Butan e 99. 2Et hy len e 99 . 9 5 % m in.Pro pylen e 99. 32 % min.1-Bu tene 9 9. 4

T able 3 V apor-liquid eq uilibrium data for the system

carbon dioxide (l)-ethane (2) at -20.2-C

P [ a t m ] x i y i K x K > # 1 2

14. 1 0.0 0 .0 - 1. 0

15.9 0.05 5 0. 133 2.4 18 0.9 18 2.6 36

17. 3 0. 10 2 0 .220 2. 157 0.86 9 2.4 83

18.7 0. 16 3 0 .30 9 1. 89 6 0.82 6 2 .29 6

19.9 0.234 0 .37 3 1. 594 0 .8 19 1. 94 8

2 1. 1 0.32 5 0.44 5 1. 369 0. 82 2 1. 6 65

2 1. 6 0.3 84 0 .50 3 1. 3 10 0.80 7 1. 624

22. 3 0.50 8 0. 570 1. 122 0. 874 1. 2 84

22. 6 0.577 0.6 13 1. 0 62 0.9 15 1. 16 1

22.7 0.600 0.62 1 1. 0 35 0 .94 8 1. 09 2

22. 8 0.659 0 .66 3 1. 00 6 0.S 1 .0 18

22.7 0.74 5 0.7 14 0.9 54 1. 12 2 0.8 51

22.0 0 .863 0.80 3 0.93 1 1. 43 8 0,64 7

20 .8 0. 945 0 .898 0. 950 1 .855 0. 5 12

19. 3 1. 0 1. 0 1. 0

T able 4 V apor-liquid eq uilib rium data for the system

carbon dioxide (l)-propane (2)

P t a t m ] x i y i K x K 2

T em p = O- C4.7 0.0 0. 0 - 1. 0

5. 5 0.0 13 0. 127 10.0 45 0. 885 ll. 359

7 .3 0.0 34 0. 330 9. 666 0. 694 13. 926

10. 2 0.0 86 0. 523 6 .146 0. 515 ll. 945

14. 7 0. 176 0 .674 3. 829 0 .396 9. 664

18. 9 0. 291 0. 745 2. 563 0 .360 7 .129

2 4. 4 0.4 61 0. 828 1. 796 0. 319 5. 627

2 7. 4 0. 622 0. 859 1. 382 0. 371 3 .772

29. 8 0. 719 0. 893 1. 242 0. 381 3. 262

32. 0 0. 840 0. 929 1. 105 0. 445 2. 483

33. 9 0.9 53 0 .976 1. 0 25 0.4 98 2.0 59

34. 4 1. 0 1. 0 1. 0

Te mp= - 20 . 2-C2. 4 0.0 0 .0 - 1 .0

3. 3 0.0 30 0. 313 10.4 33 0. 70 8 14. 732

4 .5 0.0 55 0 .513 9. 327 0. 515 18. 10 0

6. 2 0. 125 0. 661 5.2 88 0. 387 13. 650

7. 7 0. 177 0. 723 4.0 85 0. 337 12 .136

9. 6 0. 246 0 .776 3. 154 0. 297 10. 616

ll. 1 0.32 2 0. 811 2. 519 0. 279 9 .0 35

12. 8 0.40 1 0. 845 2. 107 0. 259 8 .141

14. 6 0. 544 0. 878 1. 614 0. 268 6.0 34

16.4 0.6 94 0. 90 6 1. 30 5 0. 307 4. 24 8

18. 1 0.8 68 0.9 51 1. 09 6 0.3 71 2. 953

19.3 1. 0 1. 0 1. 0

T ab le 5 V ap or-liquid equilibrium d ata fo r the system

carbon dioxide (l)-w-butane (2) at 0-C

P [ a t m ] x i v i K x K 2

1. G 4 0.0 0.0 - 1. 0

2. 4 0 .0 30 0.5 88 19.60 0 0 .4 25 46. 150

3. 9 0.0 57 0.74 1 13 ,0 00 0. 275 4 7. 324

5 .S 0.094 0.826 8. 787 0. 192 45.74 2

:. 3 0 .144 0. 877 6.042 0. 152 39.77 6

10 .6 0.20 0 0.90 0 4. 500 0 .12 5 36.0 00

12.9 0.27 5 0.9 16 3. 3 30 0. 117 28. 7 32

15. 3 0. 334 0 .920 2.7 54 0. 120 22.9 31

17. 8 0. 398 0. 932 2.342 0. 113 20.72 6

20.0 0. 469 0. 942 2.009 0. 109 18. 39 7

22.9 0. 568 0. 95 1 1. 674 0. 113 14.76 2

25 .7 0. 68 1 0. 96 3 1. 4 14 0. 116 12. 19 0

28. 6 0 .804 0. 974 1. 2 11 0. 133 9. 126

31. 5 0. 91 1 0. 983 1. 079 0. 19 1 5. 649

34.4 1. 0 1. 0 1. 0

T a b le 6 V a p o r -liq u id eq u ilib riu m d a ta fo r th e sy s te m

ca rb o n di o xi de (l )- w o- bu t an e ( 2) a t 0 -C

P [ a t m ] x i v i K i K 2

1. 5 5 0 . 0 0 . 0 - .1. 0

2. 7 0 .0 2 2 0 .4 2 2 1 9 .1 8 2 0. 5 9 1 3 2. 4 5 6

3. 5 0 . 0 3 7 0 . 5 4 1 14 . 6 2 2 0 . 4 7 7 3 0. 6 5 4

4 . 2 0 . 0 3 8 0 . 6 2 3 1 6. 3 9 5 0 .3 9 2 4 1. 8 2 3

5. 1 0 . 0 5 3 0 . 6 9 0 1 3. 0 1 9 0 . 3 2 7 3 9. 8 13

6. 2 0 . 0 7 3 0 . 7 4 4 10 . 1 9 2 0 .2 7 6 3 6 .9 2 8

7. 4 0 . 0 9 8 0 . 7 8 3 7 .9 9 0 0 .2 4 1 3 3 .1 5 4

i. 4 0 . 1 4 9 0 . 8 0 0 5. 3 6 9 0 . 2 3 5 2 2. 8 4 7

9. 8 0 . 1 6 6 0 . 8 3 0 5. 0 0 0 0 .2 0 4 2 4 .5 1 0

l l. 7 0 . 2 2 4 0 . 8 6 3 3. 8 5 3 0 .1 7 7 2 1 ,7 6 8

1 4 .6 0 . 3 1 7 0 .8 7 7 2 .7 6 7 0 .1 8 0 1 5 .3 7 2

1 6. 5 0 . 3 7 8 0 . 8 9 9 2 .3 7 8 0 .1 6 2 14 .6 7 9

1 7 . 4 0 .4 0 3 0 .9 13 2 .2 6 6 0 .1 4 6 1 5 .5 10

1 8 . 1 0 .4 1 6 0 .9 14 2 .1 9 7 0 . 14 7 1 4 .9 4 6

2 1. 1 0 .5 1 3 0 .9 2 2 1 .7 9 7 0 . 16 0 l l .2 3 1

2 3. 5 0 . 5 9 8 0 . 9 2 5 1 .5 4 7 0 .1 8 7 8 .2 7 3

2 6. 1 0 . 6 9 7 0 . 94 7 1 .3 5 9 0 .1 7 5 7 .7 6 6

2 9 .1 0 .8 1 7 0 .9 6 3 1 .1 7 9 0 .2 0 2 5 .8 3 7

3 2. 0 0 . 9 1 7 0 .9 8 1 1 .0 7 0 0 .2 2 9 4 .6 7 2

3 4 . 4 1. 0 1 .0 1 .0

and then the liquid-phase sample was expanded intoa previously evacuated sampling vessel (volume ap-proximately 10 m/) through a capillary tube whichextended to the bottom of the equilibrium cell.Before completion of liquid sampling, the liquid-phase capillary had been purged with liquid phaseseveral times to obtain the true equilibrium composi-tion.

The gas- or liquid-phase sample was introducedinto the sample loop of a gas chromatograph and

then blended to establish a completely homogeneousmixture. A Yanagimoto GCG-3DHgas chromato-graph was used for analysis, employing hydrogen asthe carrier gas at 40°C. The recorder used with itwas a Hitachi QPD-33 (full span 1 mv). At leastthree analyses were made for each phase. Other anal-ysis conditions for each system are given in Table 1.

The controlled-temperature bath is as shown sche-matically in Fig. 1. The bath consists of a outerevacuated wall and an inner shell completely sur-

rounded by Parlite insulation. Below 0°C the bath3 2 4 JOURNAL^OF CHEMICAL ENGINEERING OF JAPAN

T a b le 7 V a p o r-liq u id e q u ilib riu m d a ta fo r th e sy stem

ca rb on d io xi de ( l)- et hy le ne ( 2)

P [ a t m ] x i v i K i K 2

T e m p . = - 2 0 . 2 o C2 4 . 9 0 0 . 0 0 .0 - 1. 0

2 5 . 1 5 0 . 0 7 1 0 .0 7 2 1 .0 1 4 0 .9 9 9 1. 0 1 5

2 5 . 50 0 . 12 7 0 . 1 3 6 1 .0 7 1 0 . 9 9 0 1. 0 8 2

2 5 . 6 5 0 . 17 5 0 . 18 3 1. 0 4 6 0 . 9 9 0 1. 0 5 7

2 5 . 8 5 0 . 3 14 0 .3 0 2 0 .9 6 2 1 .0 1 8 0 .9 4 5

2 5 . 8 0 0 . 3 6 2 0 . 3 4 7 0 . 9 59 1. 0 2 4 0 . 9 3 7

2 5 . 6 0 0 . 4 6 6 0 .4 3 3 0 .9 2 9 1 .0 62 0 .8 4 8

2 5. 3 5 0. 5 0 6 0. 4 6 1 0 .9 1 1 1 .0 9 1 0 . 8 3 5

2 5. 2 5 0 . 5 4 7 0. 4 9 9 0. 9 12 1 . 10 6 0 .8 2 5

2 4 . 3 0 0 .6 7 6 0 .6 0 4 0 .8 9 4 1 .2 2 2 0 .7 3 2

2 3. 4 0 0 .7 6 7 0 .6 8 5 0 .8 9 3 1 .3 5 2 0 .6 6 1

2 2 . 4 5 0 . 8 2 9 0. 7 5 9 0 . 9 1 6 1 .4 0 9 0 .6 5 0

2 1. 7 5 0 .8 8 7 0 .8 2 0 0 .9 2 5 1 .5 9 3 0 .5 8 1

2 0. 6 5 0 .9 4 0 0 .8 9 5 0 .9 5 2 1 .7 5 0 0 .5 4 4

1 9. 3 0 1 .0 1 .0 1 .0

T e m p . = - 4 1 . 6 - C1 3 .6 0 0 .0 0 .0 - 1 .0

1 3. 8 5 0 .0 7 9 0 .0 8 4 1 .0 6 3 0 .9 9 5 1 .0 6 8

1 4. 0 0 0 . 1 7 6 0 .1 7 8 1 .0 1 1 0 .9 9 8 1 .0 1 3

1 3. 9 5 0 . 2 7 5 0 .2 6 5 0 .9 6 4 1 .0 1 4 0 .9 5 1

1 3. 8 0 0 . 4 1 3 0 .3 6 5 0 .8 8 4 1 .0 8 2 0 .8 1 7

1 3. 5 0 0 .5 1 0 0 .4 3 8 0 .8 5 9 1 .1 4 7 0 .7 4 9

1 3. 1 5 0 .5 7 2 0 .5 0 2 0 .8 7 0 1 .1 7 7 0 .7 3 9

1 2. 4 5 0 .7 3 5 0 .6 1 5 0 .8 3 7 1 .4 5 3 0 .5 7 6

l l. 7 0 0 .8 3 3 0 .7 2 0 0 .8 6 4 1 .6 7 7 0 .5 1 5

10 . 8 0 0 .9 1 4 0 .8 1 9 0 .8 9 6 2 .1 0 5 0 .4 2 6

10 . 3 0 0 .9 4 8 0 .8 8 5 0 .9 3 4 2 .2 1 2 0 .4 2 2

9 . 4 0 1 .0 1 .0 1 .0

fluid, ethanol, was agitated by a stirrer driven by amotor. Liquid nitrogen was the bath refrigerant,

entering the system from a pressurized supply dewarthrough copper tubing. The nitrogen passed througha perforated tube and bubbled through the bathfluid. The temperature control system consisted ofglass tube temperature-detector, D.C. amplifier, two

manually adjusted needle valves and an on-off controlvalve driven electrically. The temperature detectorwas composedof a glass tube thermometer employingblack-colored toluene as the enclosed liquid and aphototransister level detector mounted on the ther-mometer. The difference between the level setting

of the detector and the temperature in the bath servedas an error signal which was sent to a D.C. amplifierthat provided electrical power to the control valve.

Automatic temperature control could be attainedonly by regulating refrigerant flow rate so as tobalance the addition of heat from the surroundings.The measurement at 0°C was taken with ice and waterwhich was agitated vigorously.

Temperature was determined with a caliblatedcopper-constantan thermocouple in the wall of thecell. The probable error in temperature measurement,due to gradients in the bath, was dzO.O5°C.The pressure in the system was indicated by a

Bourdon-tube gage (0-100 atm, 300mm o.d.) cali-brated against a dead-weight gage. The accuracy ofthe gage is 0.2% of the full-scale reading.

T a b le 8 V a p o r - li q u id e q u i lib r iu m d a t a f o r t h e s y s t e m

c a r b o n d i o x i d e ( l ) - p r o p y l e n e ( 2 )

P [ a t m ] j c i v i i T i K 2 C X 1 2

T e m p . = O - C5 . 8 0 . 0 0 . 0 - 1. 0

6 . 7 0 .0 1 4 0 . 1 1 9 8 . 6 9 3 0 . 8 9 3 9 . 7 3 4

7 . 9 0 .0 5 0 0 .2 7 4 5 . 5 2 5 0 . 7 6 4 7 . 2 2 9

9 .2 0 . 0 7 9 0 .3 5 2 4 . 4 4 4 0 . 7 0 4 6 . 3 1 6

l l. 5 0 . 1 2 3 0 .4 9 3 4 . 0 1 4 0 . 5 7 8 6 . 9 4 3

1 4 .3 0 . 2 2 5 0 . 6 1 4 2 . 7 2 9 0 . 4 9 8 5 . 4 8 3

1 4 .9 0 . 2 3 1 0 .6 3 0 2 . 7 2 6 0 . 4 8 1 5 . 6 6 7

1 6 . 6 0 . 2 7 7 0 .6 6 2 2 . 3 9 0 0 . 4 6 8 5 . 1 1 2

1 8 . 1 0 . 3 2 4 0 . 7 1 5 2 . 2 0 6 0 . 4 2 2 5 . 2 3 2

2 0 .7 0 . 4 0 8 0 . 7 7 2 1 . 8 9 0 0 . 3 8 6 4 . 8 9 6

2 3 . 9 0 . 5 3 9 0 . 8 2 1 1 . 5 2 3 0 . 3 8 8 3 . 9 3 0

2 7 . 8 0 . 7 0 3 0 . 8 8 0 1 . 2 5 1 0 . 4 0 6 3 . 0 8 2

2 9 . 9 0 . 7 9 7 0 . 9 1 4 1 . 1 4 7 0 . 4 2 3 2 . 7 1 2

3 1 . 6 0 . 8 5 3 0 . 9 4 0 1 . 1 0 2 0 . 4 1 1 2 . 6 8 1

3 2 . 1 0 . 8 7 7 0 . 9 4 6 1 . 0 7 9 0 . 4 3 7 2 . 4 7 2

3 3 . 0 0 . 9 2 4 0 . 9 6 2 1 . 0 4 1 0 . 4 9 8 2 . 0 9 1

3 4 . 4 1 .0 1 .0 1 . 0

T e m p . = - 2 0 . 2 - C2 . 9 7 0 .0 0 .0 - 1. 0

4 . 5 0 .0 7 6 0 . 4 0 4 5 . 3 1 6 0 . 6 4 5 8 . 2 4 2

6 . 2 0 . 1 5 3 0 . 5 9 3 3 . 8 7 6 0 . 4 8 1 8 . 0 5 8

8 . 0 0 . 2 4 4 0 . 6 7 5 2 . 7 6 6 0 . 4 3 0 6 . 4 3 3

1 0 . 2 0 . 3 5 4 0 . 7 6 1 2 . 1 5 0 0 . 3 7 0 5 . 8 1 1

l l. 8 0 . 4 4 0 0 . 8 0 4 1. 8 2 7 . 0 . 3 5 0 5 . 2 2 0

1 3 . 7 0 . 5 4 3 0 . 8 4 6 1 . 5 5 8 0 . 3 3 7 4 . 6 2 3

1 5 . 8 0 . 7 0 4 0 . 9 0 2 1. 2 8 1 0 . 3 3 1 3 . 8 7 0

1 7 . 7 0 . 8 4 6 0 . 9 4 1 1 . 1 1 2 0 . 3 8 3 2 . 9 0 3

1 9 . 3 1 .0 1 .0 1 .0

T a b le 9 V a p o r - liq u id e q u ilib r iu m d a t a f o r t h e s y s t e m

c a r b o n d i o x i d e ( l ) - l - b u t e n e ( 2 ) a t 0 - C

P [ a t m ] x i y i K i K 2

1. 2 5 0 . 0 0 . 0 - 1 .0

3 . 1 0 . 0 5 9 0 . 6 1 6 1 0 .4 4 1 0 .4 0 8 2 5 . 5 8 4

5 . 6 0 . 1 2 3 0 . 7 8 4 6 . 3 7 4 0 . 2 4 6 2 5 . 8 7 9

!. 1 0 . 1 9 9 0 . 8 4 0 4 . 2 2 1 0 . 1 9 9 2 1. 1 2 6

1 0 . 8 0 .2 7 6 0 . 8 8 1 3 . 1 9 2 0 . 1 6 4 ' 1 9 .4 1 6

1 3 . 7 0 . 3 6 2 0 . 9 0 9 2 . 5 1 1 0 . 1 4 3 1 7 . 6 0 9

1 6 . 5 0 .4 5 4 0 .9 1 9 2 .0 2 4 0 . 1 4 8 1 3 . 6 3 9

1 9 . 3 0 . 5 4 4 0 . 9 3 2 1 .7 1 3 0 . 1 4 9 l l .4 8 9

2 2 . 1 0 .6 1 7 0 . 9 4 7 1 . 5 3 5 0 . 1 3 8 l l .0 9 1

2 5 . 4 0 .7 4 3 0 .9 6 0 1 .2 9 2 0 . 1 5 6 8 .3 0 3

2 8 . 7 0 . 8 3 6 0 .9 7 1 1 . 1 6 1 0 . 1 7 7 6 .6 2 3

3 1 . 5 0 .9 2 1 0 .9 8 5 1 .0 6 9 0 . 1 9 0 5 .6 2 9

3 4 .4 1 . 0 1 . 0 1 . 0 0

Materi alsThe pure components used in this study were

furnished by Takachiho Chemical Industry Co.Before the materials were used, the analyses werechecked by gas chromatography and found to be

within the specifications from the supplier in Table 2.

Results

Experimental vapor-liquid equilibrium data forthe systems carbon dioxide-ethane, carbon dioxide-propane, carbon dioxide-w-butane, carbon dioxide-isobutane, carbon dioxide-ethylene, carbon dioxide-

propylerie and carbon dioxide-1-butene are presentedin Tables 3 to 9, respectively and graphical illustra-

tions for some representative systems are shown in

VOL 7 NO. 5 1974 325

35

30

25

20

o This Wor k蝪 Akers et al!(0.0-G

A This Wor k0 Akers et alV w ox )

R-K FQ l

蝪

n

n

p o .o-c(a tm ) 0

15

10

5

00

-20.2-C

蝣蝣0 .2 . Q A 0 .6 0 . 8 1 .

X n Y i

Fig. 2 Pressure-composition diagram for thesystem carbon dioxide (l)-propane (2)

3 5

3 0

2 5

2 0

p( A T M )

1 5

1 0

5

0

0

o T h i s W o r k

0

R - K E q .

ｰ c0 .

e 0 . 2 0 . 4 0 . 6

* 1 ' Y l

Fig. 3 Pressure-composition diagram for thesystem carbon dioxide (l)-w-butane at 0°C

Figs. 2 to 5. Through these figures solid lines showthe calculated values by using the modified Redlich-Kwongequation of state, which will be mentionedbelow. The data available from the literature inthe temperature range of this investigation are alsoplotted for each system.The carbon dioxide-ethane system and the carbondioxide-ethylene system in Fig. 4 show marked posi-tive deviation from Raoult's law and indicate a

maximumin the equilibrium pressure for each iso-

3 0

2 5

2 G

p( A T M )

1 5

1 0

5

0

A T h i s W o r k

0

6 , 7 )O H a s e l d e n e t a l .

o T h i s W o r k

R - K E q .

- 2 0 . 2 - C ･ k

- l l . 6 - C

0 . 2 0 . 4 0 . 6 0 . 8 1 .

X i . Y i

Fig. 4 Pressure-composition diagram for thesystem earbon dioxide (l)-ethylene (2)

3 5

3 0

2 5

2 0

p( A T M ]

1 5

1 0

5

00

o T h i s W o r k

0

1 5 )0 Y o R I Z A N E E T A L ,

E H a s e l d e n e t a l . '

蝪

A T h i s W o r k

R - K E q .

/ ¥D

蝪

o . o - c

- 2 0 . 2 - C

4

D

0 . 2 0 . 4 0 . 6

X i . Y i

Fig. 5 Pressure-composition diagram for thesystem carbon dioxide (l)-propylene (2)

therm. In other words, a low-boiling azeotrope isformed throughout the temperature region investi-gated.This is in agreement with the results of Hakutam dl?\ Haselden et al^7) and Clark and Din3) forcarbon dioxide-ethylene and with those of Hakutaet al.4) and Buckingham2) for the carbon dioxide-ethane system. The azeotropic composition and

pressure determined by plotting the equilibrium ratioagainst liquid composition and against equilibrium

pressure, respectively, are summarized with the litera-ture values in Table 10.

Except for the binary systems described above, notendency toward azeotropic behavior was found inthis investigation. In several systems of carbon

m

JOURNAL OF CHEMICAL ENGINEERING OF JAPAN

dioxide with light hydrocarbons (Figs. 2, 3 and 5),there is apparently a reverse curvature in the vaporlines of each isotherm in the region of rich carbondioxide content. Akers et alP reported the carbondioxide-propane system over the temperature rangeof -40°F to 32°F (Fig. 2). The pressure-compositiondata of this investigation at -20.2°C and those ofAkers et alP at -20°C agree comparatively well,but the 0°C isotherms show significant deviations,especially on the liquid lines. For the carbon di-oxide-propylene system, the present data are com-pared with literature values in Fig. 5. Haseldenet al.QJ) measured the dew and bubble point curvesfor this binary over the temperature range of -30°Cto 85°C. Both their interpolated data and the resultsof Yorizane et al.15) are in close agreement with thepressure-composition curves obtained in this investi-gation.No vapor-liquid equilibrium data for the carbondioxide-C4-hydrocarbon systems in the low-tempera-

ture region have been reported. A graphical illustra-tion of pressure-mole fraction behavior is given in Fig.

3 for the system carbon dioxide-«-butane. Simillarpressure-composition behavior was obtained for car-bon dioxide-isobutane and carbon dioxide-1-butenesystems.

In Fig. 6, the equilibrium ratio for carbon dioxideis plotted on logarithmic paper at constant tem-perature (0°C) against pressure. The straight lineshows the calculated values by utilizing Raoult's law.The modified Redlich-Kwong equation of state wasused to calculate vapor-liquid equilibria of binarysystems which were determined in this investigation.The calculation presented hereinafter follows a methodsimilar to that employed by Peter and Wenzel13).The Redlich-Kwong equation modified by Joffe et al.9\is given as follows:

P=RT/ (v~b)-a/{T(iMv+b)} (1)where

. au=Qail?TlflPci (2)

bt=ObiRTei/Pei (3)

and

fl= S E XiXfiu (4)3

b= ZbiXi (5)i

tfii=flii =(l -6) Va^ojj (6)

Here the dimensionless parameters for a pure sub-stance Qai and Qhi are given not from critical databut from pure-component volumetric data for thesaturated liquid9\ 6 is a interaction parameter whichis determined by adjusting it to only one experimentalpoint on the pressure-liquid composition curve of the

T a b le 1 0 -1 A ze o tro p ic d a ta fo r th e s y stem c a rb o ndi oxi de (l )- eth ane ( 2)

T e m p . [ - C ] P r e s . [ a t m ] x u a z R e fe ren ce

0 . 0 3 9 .3 0 . 6 7 3 H ak uta et al .i ]- 2 0. 2 2 2 . 8 0 . 6 6 6 T h i s w o r k

T ab le 1 0 -2 A z e o tro p ic d a ta fo r th e sy s te m ca r b o nd io x id e (l )-e th y le n e (2 )

T e m p . [ - C ] P r e s . [ a t m ] x u a z R e fe re n c e

0 . 0 4 3. 4 0 . 4 14 Ha ku ta et a l.i ]0 . 0 4 3 .1 8 0. 3 5 9 Ha s el de n e t aL Q ]

- 10 . 0 3 3. 0 0 0 . 3 14 i b i d .- 2 0 . 0 2 6 . 0 6 0. 2 8 0 i b i d .- 2 0 .2 2 5 . 8 5 0 .2 6 5 T h i s w o r k- 3 0 .0 1 9 . 80 0 . 2 4 6 Ha s e l de n e t a l ^

- 3 5. 0 1 7 . 1 8 0 . 2 2 8 i b i d .- 4 1 .6 1 4 . 0 0 . 2 0 5 T h i s w o r k

5 0A C O 2 - C 3H 8

0

3 0

1 0

:<i

5 .0

3 .0

1 .0

1

O C O 2 - N- C 4 H l O

c o 2 - c 3h 6

C O 2 - 1 - C 4 H 8

- R a o u lt 's L a w

o

o

o

D A

ｰ A A

o

蝣3 . 0 5 . 0 3 0 5 0

P (a t m )

Fig. 6 Equilibrium ratio of carbon dioxide-pressure

diagram for the system carbon dioxide (l)-hydrocarbon(2) at O°C

binary mixture. Applying Eq. (1) to liquid phase aswell as vapor phase coupled with a set of param-eters for a given temperature, we calculated vaporcomposition and pressure for each experimental liquidcomposition and temperature.The solid lines in Figs. 2 to 5 show the calculatedresults by using the modified Redlich-Kwong equationmentioned above. The point marked with a solid

circle in the plot was taken for the determination ofthe interaction parameter 6. The calculated resultsare compared in Table ll with the experimental valuesin this investigation. The binary interaction coef-ficient 6 for each system is also given in this Table.According to the results of Fig. 6 described in theprevious section and Table ll, it is seen that themagnitude of 6 is, on the whole, corresponding to theextent of the deviation from Raoult's law.Previously, Joffe and Zudkevitch8), and Kaminishiet al.10) have noted that vapor-liquid equilibriumrelationships for systems containing carbon dioxideand light hydrocarbons could not be well calculatedby using an equation of state. However, it has

been pointed out10)14) that a marked improvement inthese calculations was obtained by applying a modified

VOL.7 NO.5 1974 327

T able l l Interaction para m eter 6 an d avera ge d eviation

for y and P in the system carbon dioxide (l)-hydrocarbon (2)

C o m p o nen t (2) t 6 A P A yx N o . of[-C ] [atm ] d ata

p oin ts

E th an e - 20 .2 0 .1271 0. 245 0.00 83 13

P rop ane 0 .0 0 .1532 0 .4 10 0 .0 10 2 10

- 20. 2 0. 12 21 0. 17 2 0.00 89 10

^-B u tane 0 .0 0 .10 83 0.2 76 0.0 10 8 13

/̂ -B u tan e. 0 .0 0 .10 19 0 .3 16 0. 0 135 18

E th ylene - 20 .2 0 .06 39 0 .16 1 0 .0080 13

-4 1. 6 0. 06 83 0. 17 1 0. 0135 10

P rop ylen e 0 .0 0 .10 30 0 .23 1 0 .0 10 1 15

- 20.2 0. 07 11 0. 176 0.0 134

1-B u tene 0 .0 0 .0 579 0 .180 0. 0098 ll

N4/"= S l/cai - /exp|ｻ/iV; 7V=No. of data points

1

Benedict-Webb-Rubin equation of state with the cor-rection factor m corresponding to the interactionparameter 6 in this investigation. Throughout thecarbon dioxide-light hydrocarbon binaries given in

Table ll, the overall average deviation of vapor com-position is ±0.0097 mole fraction and that of pressure

is ±0.212 atm. In particular, the magnitude ofdeviation in the calculated vapor composition is as

small as the results obtained by means of empiricalrelationships for the activity coefficients.

As discussed above, the modified Redlich-Kwongequation provided a fairly excellent representation

of the equilibrium data for the binary mixtures ofcarbon dioxide-light hydrocarbons at low temperature,and it permitted mixture behavior to be estimated

solely from pure-component information and onlyone experimental datum of the mixture.

Acknowl edgmen tThe authors wish to thank Mr. Minoru Kato for technical

assistance, and Mr. Jun Togo for computational assistance.Nomencl ature

a = constant in the Redlich-Kwong equation[/2 - atm. °K°-5/g-mol2]

b = constant in the Redlich-Kwong equation[//g-mol]

K = vapor-liquid equilibrium ratio [-]

n = number of components [-]P = pressure [atm]R = gas constant, 0.082057 [/ à" atm/g-molà"°K]

t = temperature [°C]T = absolute temperature [°K]

v = molar volume [//g-mol]x = mole fraction in liquid phase [-]y - mole fraction in vapor phase [-]

a = relative volatility defined as aij=Ki/Kj [-]6 = binary interaction parameter in Eq. (6) [-]Q = dimensionless constant in Eqs. (2) and (3) [-]

<Subscripts>az = azeotropic point

c = critical state/,y,1or2 = componenti,j, 1 or2

ij = binary pair of components i and jLiterature Cited1) Akers, W. W., R. E. Kelly and T. G. Lipscomb: Ind. Eng.

Chem., 46, 2535 (1954)2) Buckingham, A. D. Q.: Rev. Chem. Soc, 13, 183 (1959)

3) Clark, A.M. and F. Din: Trans. Faraday Soc, 46, 901(1950)

4) Hakuta, T., K. Nagahama and S. Suda: Kagaku Kogaku,33(9), 904 (1969)

5) Hakuta, T., K. Nagahama and M. Hirata: Bull JapanPetrol Inst., ll, 10 (1969)

6) Haselden, G. G., D. M. Newitt and S. M. Shah: Proc. Roy.Soc, ser. A209, 1 (1951)

7) Haselden, G.G., F.A. Holland, M.B. King and R.F.

Strickland-Constable: Proc. Roy. Soc, ser. A240, 1 (1957)8) Joffe, J. and D. Zudkevitch: Ind. Eng. Chem., Fundamentals,

5, 455 (1966)

9) Joffe, J., G. M. Schroeder and D. Zudkevitch: AIChEJ.,16, 496 (1970)

10) Kaminishi, G., Y. Arai, S. Saito and S. Maeda: /. Chem.Eng. Japan, 1, 109 (1968)

ll) Kuenen, J. P.: Z. phys. Chemie, 24, 667 (1897)

12) Myers, A. L. and J. M. Prausnitz: Ind. Eng. Chem., Funda-mentals, 4(2), 209 (1965)

13) Peter, S. and H. Wenzel: Chem. Ing. Techn., 43(10), 623(1971)

14) Sarashina, E., Y. Arai and S. Saito: /. Chem. Eng. Japan,4, 377 (1971)

15) Yorizane, M., S. Yoshimura and H. Masuoka: KagakuKogaku, 31, 759 (1967)

16) Zudkevitch, D. and J. Joffe: AIChE J., 16, 112 (1970)