THE RICE INSTITUTE

The Solubility of Methane., Carbon Dioxide^

and Hydrogen Sulfide in Oxygenated Compounds

at Elevated Pressures

by

Phillip David Mantor

A THESIS

SUBMITTED TO THE FACULTY

IN PARTIAL FULFILLMENT OF THE

REQUIREMENTS FOR THE DEGREE OF

Master of Science

in

Chemical Engineering

Houston, Texas

March 1960

I 3 1272 00126 5923

Acknowledgment

I would like to acknowledge those who aided in the

completion of this investigation, and especially:

Professor Riki Kobayashi for his guidance and aid in

the experimental work.

Tennessee Gas Transmission Company for the methane

used in the research.

Jefferson Chemical Company for the Propylene Carbonate

used and for the analysis by which the gas phase was studied.

Ruska Instrument Company for the high pressure

cell.

Shell Development Company for the constant temperature

bath used in the determinations.

Brown & Root, Inc. for their financial support during

1959.

Sam Pollard for his aid in the design and construction

of the equipment.

My family, for their encouragement and financial aid

during these many years.

ii

Table of Contents

Page No.

I. Objectives of the Investigation 1

II. Summary of Work 2

III. Previous Work 4

IV. Experimental Determination 5

A. Apparatus 5

B. Materials 6

C. Experimental Procedure 7

V. Experimental Results 10

VI. Treatment of Data 14

VII. Data 18

VIII. Figures

IX. Literature Cited

X. Appendix A

XI. Appendix B

iii

List of Tables

I. Experimental liquid phase solubilities and compositions

as a function of pressure at various temperatures

II. Liquid phase graphically smoothed compositions and

thermodynamically calculated compositions as

functions of pressure at various temperatures

III. Activity coefficients for Hydrogen Sulfide in

Ethylene Glycol liquid

IV. Constants for the equation of Krischevsky

iv

List of Figures

I* Schematic Equipment Diagram

II. Propylene Carbonate-Methane System: Solubility versus

Pressure

III. Propylene Carbonate-Carbon Dioxide System:Solubility

versus Pressure

IV. Ethylene Glycol-Carbon Dioxide System:Solubility

versus Pressure

V. Ethylene Glycol-Hydrogen Sulfide System; Solubility

versus Pressure

VI. Pressure versus Mole Fraction Methane in Liquid

Propylene Carbonate

VII. Pressure versus Mole Fraction Carbon Dioxide in

Liquid Propylene Carbonate

VIII. Pressure versus Mole Fraction Carbon Dioxide in

Liquid Ethylene Glycol

IX. Pressure versus Mole Fraction Hydrogen Sulfide in *

Liquid Ethylene Glycol

X. Schematic Pressure-Composition Diagram

XI. Pressure-Temperature.Prpjection for Ethylene Glycol-

Hydrogen Sulfide System

XII. Krischevsky Relationship for Propylene Carbonate-Methane

XIII. Krischevsky Relationship for Propylene Carbonate-Carbon

Dioxide

v

List of Figures (Cont'd.)

XIV. Krischevsky Relationship for Ethylene Glycol-Carbon

Dioxide System

XV. Krischevsky Relationship for Propylene Carbonate-

Hydrogen Sulfide System

XVI. Activity Coefficients for Hydrogen Sulfide in Liquid

Ethylene Glycol

vi

OBJECTIVES OF THE INVESTIGATION

The objectives of the investigation were:

(1) to obtain experimental liquid compositions for the systems methane

propylene carbonate, carbon dioxide-propylene carbonate, carbon dioxide

ethylene glycol, and hydrogen sulfide-ethylene glycol over a range of

temperatures and pressures,

(2) to verify that the partial pressure of the respective solvents in

the equilibrium gas phase would be of the order of magnitude of the

pure solvent vapor pressures,

(3) to apply the Phase Rule to the experimental observations and to

obtain a general understanding of the phase behavior of the systems,

and

(4) to correlate the experimental data by the use of pure component

thermodynamic data.

1

SUMMARY OF WORK

This study Considered vapor-liquid equilibrium compositions in

four binary systems. Equilibrium liquid phase compositions in the system

methane-propylene carbonate were obtained at 80, 100, 160, and 220°F at

pressures up to 2000 psia. Since the methane was far above its critical

state, there was no three-phase region-under these conditions.

Experimental data for the system carbon dioxide-propylene car¬

bonate were determined at 80, 100, 160 and 220°F. The pressure was a

maximum for 160°F at 1000 psia. No three-phase region in this system

at 80°F to a pressure of 805 psia was evident and at the higher temp¬

eratures the carbon dioxide was super-critical.

The system carbon dioxide-ethylene glycol was studied at 78,

100, 160, and 220°F at pressures up to 1050 psia. The three-phase

condition existed for the lowest temperature at a pressure of 899 psia.

The system was examined for a three-phase region at 90°F and 1100 psia

but none was found. The composition of the gas phase of this system

was experimentally determined to check the assumption that the solvent

concentration in the gas phase could be neglected in the theoretical

treatment. The checks were made at 220°F, 100 psia; 220°F, 1000 psia;

and 80°F, 800 psia. The ethylene glycol concentration was less than

0.001 mole fraction in all cases.

The system hydrogen sulfide-ethylene glycol was studied at

84, 100, and 160°F. Pressures ranged up to 780 psia at 160°F. The

three-phase region at 84°F was at 340 psia and at 100°F it existed at

405 psia. These points were both slightly above the vapor-liquid con¬

ditions for the pure hydrogen sulfide. No composition data was taken

in the two liquid phase region.

2 -

Using the method of Krischevsky (10) the experimental data were

used to determine equations for finding the equilibrium compositions of

the liquid phase in each system as a function of properties of the pure

solute. Data calculated by this method gave close agreement with graphi¬

cally smoothed data in all the systems except hydrogen sulfide-ethylene

glycol at higher pressures.

Deviation from ideal solution behavior for the hydrogen sul¬

fide-ethylene glycol system was obtained by calculation of activity

coefficients which ranged from a lower value of 1.8 at 160°F and 780

psia to a value of .4.6 at 50 psia and 84°F.

- 3 -

PREVIOUS WORK

The binary systems treated in this work had never before been

experimentally studied. Lecat (11), (12), (13) studied azeotropes in

the systems containing ethylene glycol and paraffinic, napthenic and

aromatic hydrocarbons. The ternary system diethylene glycol-benzene-

water was studied (6) between 25 and 175°C at one atmosphere pressure.

The effect of water on benzene solubility is the main consideration of

the work. Diethylene glycol-natural gas (19) was studied up to 2000

psia at 100°F. The diethylene glycol used contained 5 weight per cent

water. The variation of the gas solubility with pressure was reported.

Triethylene glycol-water-natural gas system (16) was studied for pres¬

sures up to 2000 psia and 60-100°F. to give the solubility of a natural

gas in triethylene, glycol as a function of pressure.

No data on the solubility of gases in propylene carbonate

have been reported.

Solubility data in systems of nitrogen in water (10) at

high pressures is correlated by means of pure component thermodynamic

properties. The same method of correlating solubility is also des¬

cribed for systems of hydrocarbons and water (9) (14) at pressures

up to 10,000 psia, and in systems of hydrogen and hydrocarbons for

pressures of 8000 psia and temperatures as low as -300°F (23).

- 4 -

EXPERIMENTAL DETERMINATION

Apparatus: The apparatus used in this work was basically similar to

that described by Kobayashi (9) (20). The equipment may be broken

into three main segments; (1) equilibrium apparatus, (2) pressure

maintenance apparatus and (3) analytical apparatus (Figure 1).

The equilibrium apparatus consisted of a high pressure cell

and a constant temperature air bath. The windowed cell was designed

to hold pressures of 10,000 psia. It was mounted on bearings near

its center of gravity and was rocked in order to hasten the approach

to equilibrium of its contents. The charging line for gas was

fastened to the top of the cell through a valve to the gas phase.

The liquid phase sample was transmitted from the bottom of the cell

through capillary tubing to a needle valve and then to the analytical

train. The air bath was designed to circulate heated air in a closed

circuit around the cell. The air temperature was maintained by means

of electrical heating coils installed in the air stream. The tempera¬

ture of the cell contents was measured by means of a thermocouple

placed in the side of the cell. The EMF of the thermocouple was

measured by a Leeds and Northrup Precision Portable Potentiometer.

Cell pressure was measured on a calibrated 2000 psi Heise gauge

with 2 psi subdivisions. This gauge was used for all the systems

except hydrogen sulfide-ethylene glycol. For the latter system

a calibrated Bourdon Test Gauge was used which registered 2000 psi

with 5 psi subdivisions.

5

The pressure maintenance system was composed of the gas cylinder,

the gas reservoir, and a mercury displacement pump. With this equipment

the cell was charged with gas at pressures greater than that in the gas

cylinder. This equipment was also used to maintain constant cell pres¬

sure while sampling.

The analytical apparatus consisted of four pieces. The first

was the burette used as a flash chamber for the liquid phase. The

second was an empty drying tube through which the flash gas passed and

which was used as a trap for any foreign matter. The third part was

the manometer used to measure the system pressure. The fourth part

was a flask of known volume into which the flash gas expanded. There

was a three-way stopcock at the top of this flask through which the

system was evacuated. The tubing connections were all made with india

rubber tubing which had been impregnated with paraffin (9). Since the

connections between the burette and the rest of the system were broken

and remade after each run, the purpose of the trap was to catch pieces

of paraffin which got into the tubing.

Materials: The materials used in the experiments had the following

properties:

(1) Methane: Tennessee Gas Transmission Company; line gas

from North Louise Field with ethane and water

as impurities: 99.7 mole %

(2) Carbon Dioxide: Spencer Chemicals Company; cylinder

gas; nitrogen as impurity: 99.6 mole %

(3) Hydrogen Sulfide: Mathieson Company, Inc.; purified

grade compressed gas 99.5 mole %

6

(4) Propylene Carbonate: Jefferson Chemical Company 99 wt. % min.

(5) Ethylene Glycol: J. T. Baker Chemical Co., "Baker

Analyzed" Reagent Grade, boiling range 198.8-

199.8°C; water 0.04 wt. %

The structural formula of propylene-carbonate is given below.

H ? H\ I H-C-C-CK H7 1 /C*0 M H ~ C — O'

l H

Before use all the gases were passed through steel tubes con¬

taining Drierite in order to remove the water present. The methane was

passed through an additional tube filled with Ascarite to remove the

carbon dioxide present.

Experimenta1 Procedure: To charge the system the cell was evacuated

and the vacuum was used to draw in the liquid solvent. The gas was

passed from the cylinder into the reservoir and the cell. If pres¬

sures higher than cylinder pressure were desired, the cylinder was

shut off from the system and the mercury pump was used to displace

gas from the reservoir into the cell. Better results were achieved

in displacing the reservoir gas if, instead of using the mercury

pump, the reservoir was heated.

The system was charged initially to the highest pressure

at which the liquid composition was determined. The liquid was

agitated during the initial gas charging period. By periodically

closing the cylinder valve during this time it could be determined

when the liquid was nearly saturated with gas. After a period there

was only a slight pressure drop with time when the cylinder valve

was closed. At this point the cylinder valve was closed and the

system was allowed to come to its final equilibrium pressure with

7

agitation. The temperature of the cell was measured by the potentio¬

meter and the variation in temperature was controlled by a variable

heater set in the air bath. When the cell came to constant tempera¬

ture and pressure the system was at equilibrium. Agitation was

stopped and the system was allowed to sit for fifteen minutes.

Before a sample of the liquid phase was taken the sample

tubing was flushed by passing about 5 cc. of liquid into a beaker.

Then the sample tubing was attached to the analytical train. The

analytical system was evacuated and allowed to sit for five minutes

to check for leaks. Then the valve on the sample tubing was opened

and the liquid phase was passed into the burette. During this sampling

period the cell pressure was maintained at a constant value by occas¬

ionally cracking the valve to the gas source. After about 10 cc. of

flash liquid was collected the sample valve was closed. The analy¬

tical system pressure was allowed to come to a constant value and

recorded. The volume of liquid was recorded. The analytical system

was then cleaned of liquid and made ready for another analysis. The

valve to the reservoir was closed and the gas phase was vented to some

lower pressure. The temperature was held constant and more data were

taken at decreasing values of pressure. Four of these isotherms were

obtained for each binary system.

The composition of the gas phase was found at three points in

the carbon dioxide-ethylene glycol system. The sample tubing was at¬

tached to the top of the cell and the mercury pump was attached

directly to the bottom. The cell was filled with liquid and gas as

before and brought to equilibrium. During the sampling period the

cell pressure was maintained by injecting mercuty into the bottom of

the cell and the sample line was heated to prevent liquid drop out.

8

The gas sample was passed from the top of the cell into a series of two

absorption chambers. These were filled with distilled water to absorb

the ethylene glycol present. The gas from the second chamber went to a

wet test meter. The amount of gas .sampled was recorded. The amount of

ethylene glycol in the gas was determined by analysis for glycol of the

liquid in the two absorbers. This analysis, was done by a titrimetric

method developed by Jefferson Chemical Company (Appendix X).

Each determination took approximately forty five minutes. The

analysis showed the amount of ethylene glycol in the gas phase was below

0.001 mole fraction.

9

EXPERIMENTAL RESULTS

The Phase Rule as expressed by Gibbs (1) was very helpful in

describing the condition of equilibrium for this experiment. When ap¬

plied to a two component, two phase mixture the Phase Rule states that

two intensive variables must be set for equilibrium. In this work the

intensive variables chosen were temperature and pressure; that is,

when the temperature and pressure of the system were set, the composi¬

tions of the co-existing phases were invariant. If three phases appeared

in a binary system there was only one variable which had to be fixed.

This meant that for a binary, three-phase region, setting any one vari¬

able set all the other variables, i.e., choosing the pressure deter¬

mined the co-existing phase compositions and the temperature.

In this work the equilibrium compositions of a liquid phase

in co-existence with a vapor phase were determined at various pressures

along an isotherm. This procedure was repeated for several isotherms

to completely define the two phase region over a range of experimental

conditions.

The system hydrogen sulfide-ethylene glycol is described first.

Figure 10 shows a schematic diagram of the behavior of this system at

some constant temperature. In this experiment the vapor region (V) is

pure hydrogen sulfide so the dashed line lies on the 1.0 mole fraction

hydrogen sulfide* axis. The saturated liquid boundary between the L^ and

Lj^-V regions is defined by the experimental liquid phase compositions.

The experimental data originally taken is shown as solubility of hydro¬

gen sulfide in the liquid phase as a function of pressure (Figure 5).

This is replotted with pressure as a function of composition to correspond

- 10

to Figure 10. The experimental data are listed in Table 1. These com¬

positions are shown in Figure 9. The hydrogen sulfide is seen to be very

soluble in the ethylene glycol. At 160°F the hydrogen sulfide concen¬

tration is 0.55 mole fraction at 780 psia. The L2“V region was not

determined in this experiment. The point is the vapor pressure of the

pure hydrogen sulfide at the temperature of the experiment. P£ is the

three-phase pressure. Note that the three-phase compositions and P2 are

unique for this temperature. The L1-L2 region would be defined by

measuring compositions of the coexisting liquid phases at increasing

pressures.

As the system temperature is increased above the critical

temperature of hydrogen sulfide,the L2“V region would pull away from

the 1.0 mole fraction axis until it had completely disappeared. At

this point the system is a two-phase mixture of ethylene glycol in

equilibrium with hydrogen sulfide fluid at all pressures.

Figure 11 is a pressure-temperature diagram for the hydrogen

sulfide-ethylene glycol system. The lines LJ.-V and L2~V are the vapor

pressure curves for pure ethylene glycol and hydrogen sulfide. The

L]_-L2“V or three-phase locus is drawn and the three-phase critical is

shown near the pure hydrogen sulfide critical. Lines of constant

liquid composition are drawn to show the experimental results. The

ethylene glycol critical is not shown since it falls at a much higher

temperature. The loop describing the locus of binary criticals would

rise to extreme pressures because of the large difference in the pure

component critical temperatures.

Within the experimental limits, the phase behavior of the system

propylene carbonate-methane is much simpler. The methane solubility is

11

shown in Figure 2 and the pressure composition curves are in Figure 6.

The experimental data are reported in Table (1). It is seen that the

methane composition is fairly low, being only 4.4 mol % at 220+F and

1900 psia. The system shows one behavior not seen in the other three

binaries: The solubility of methane increases with increasing tempera¬

ture. The system is always above the methane critical, hence there is no

three-phase region or I*2~V envelope within the experimental limits. The

schematic representation of pressure versus composition would be a closed

loop starting at the ethylene glycol vapor pressure and 0% methane and

going to some higher pressure where the binary critical exists.

The liquid phase compositions of the carbon dioxide-propylene

carbonate system are shown in Figures 3 and 7. The experimental data

are listed in Table (1). The carbon dioxide is seen to be much more

soluble in propylene carbonate than is methane. At 80°F and 800 psia

the carbon dioxide composition of the liquid is 42.5 mol %. The carbon

dioxide is super-critical at all experimental temperatures studied ex¬

cept 80°F. The schematic representation of the pressure-composition

diagram would be expected to resemble Figure 10 at 80°F. At the

higher temperatures it would resemble the behavior described for

methane-propylene carbonate.

The system carbon dioxide-ethylene glycol has phase behavior

identical to the carbon dioxide-propylene carbonate system. The solu¬

bility and composition versus pressure are shown in Figures 4 and 8.

The experimental data are given in Table (1). Carbon dioxide is seen

t6 be less soluble and the maximum experimental concentration was the

three-phase point at 78°F and 900 psia of 17 mole % carbon dioxide.

For the 78°F isotherm the phase behavior will resemble Figure 10. At

12 -

higher temperatures the simpler phase behavior described for methane-

propylene carbonate should obtain. The three-phase critical is reached

when the pure carbon dioxide critical is reached. This was found by

raising the binary temperature to 90°F and pressurizing the system.

The system remained two-phase up to 1100 psia.

The composition of the gas phase was measured and found to

contain less than 0.001 mole fraction ethylene glycol at higher pres¬

sures. At the lower pressures the solutions follow Henry's Law and the

gas should approximate ideal gas behavior. Using these two rules the

equilibrium compositions of the two phases could be found along the

lower part of the saturated vapor curve.

- 13 -

TREATMENT OF DATA

The experimental data of this work were used to derive con¬

stants for equations which correlated the equilibrium compositions of

the liquid phase with thermodynamic data of the pure solute.

The fugacity of the solute was assumed to follow the equation:

f L " x pOO

(1)

Equation (1) was integrated at constant temperature to give:

log (f$ / x> R log K; + v (p - pk) / 2.303 RT (2)

where: £.9 is the fugacity of the pure component in the vapor

x is the mole fraction in the liquid K is the Henry's Law constant v is the partial molal volume in the liquid P is the system pressure Pk is the pure solvent vapor pressure R is the gas constant T is the absolute temperature of the system fT is the fugacity of the solute in the liquid f^° is the fugacity of the solute at infinite dilution

The above equations were used to refer only to the solute so no sub¬

scripts were given. It was assumed in integrating equation (1) that

the liquid phase follows Henry's Law at low pressures and that v was con¬

stant over the range of integration. It is seen that a plot of log (f°/x)

versus (P-Pk) / 2.302RT should be linear. The slope is v and the intercept

at P=Pk is K. Since Pk in the system studied was so low compared to

/ P, Pk was eliminated.

^ The fugacities for hydrogen sulfide were obtained from the

thermodynamic data of Sage (Appendix B). The carbon dioxide data came

from the literature (2) as did the methane data (21).

Experimental data were used to calculate log (f°/x). These

values were plotted versus P/2.303RT at constant temperature for the

- 14 -

four syst as; Figures 12, 13, 14, 15. The best straight lines were

drawn through the experimental points and 'log K and ^ were obtained

(Table 4). Using values of log K and v in equation (2), values for

x were calculated. These values were compared with graphically

smoothed data in Table (2).

The system Inethane-propylene carbonate is well represented by

one straight line at all temperatures. This indicates v is nearly in¬

dependent of temperature, pressure, and composition. Log K is indepen¬

dent of temperature.

The experimental log (f°/x) for the systems carbon dioxide-

propylene carbonate and carbon dioxide-ethylene glycol were plotted.

The slope of the log (f°/x) plots were all negative.

The hydrogen sulfide system showed strong deviation from the

straight line plot. Straight lines could be drawn which represented

the data at low concentrations but at the higher limits this failed.

This effect is discussed by Leland (14) and happens near phase

changes. In this case the hydrogen sulfide concentration became

quite large (50%) and this would mean the system was leaving the

dilute region for which the original equation was derived.

The hydrogen sulfide-ethylene glycol system data were also

studied to determine deviation from ideal solution behavior. For an

ideal solution the fugacity may be written for one component:

fL = fv = 'V

x (3)

where 1 and v refer to vapor and liquid and is the activity co¬

efficient.

Using the pure component properties of hydrogen sulfide and

graphically smoothed experimental data, the values of '"Y were calculated.

- 15

The results are listed in Table (3) and plotted versus pressure in

Figure^ 16. , ■

The .is highest for low temperatures and varies considerably

in the 84°F isotherm. As the temperature increases the curves flatten

and the 160°F isotherm is nearly constant until it approaches a phase

change above 700 psia.

Ewell (4) described a method for predicting qualitative devi¬

ation from ideal solution behavior. The method described takes into

account the ability of the components to form or break hydrogen bonds.

The hydrogen sulfide and ethylene glycol system was studied using the , • ■ i

classification Ewell proposed. The predicted deviations were positive,

(^f}1.0) and were seen to agree with the values calculated for the sys¬

tem. Ewell also predicts that this type of system might have only

limited miscibility in the liquid phase and this condition-is found to

obtain in the experimental region.

The partial molal volume (v) is defined as y =

where: V is the system volume

ni is the moles of component one.

Another definition of v is:

▼ s v° + RT(3 I n^C?P)T (17)(18) where v° is the molal

volume of the pure component. From this equation it is seen that v

can be negative only when ( 3lnj^dlP)>ji is negative-. For the system

hydrogen sulfide-ethylene glycol Oln^$P)T shows this negative be¬

havior. The behavior of v in the systems carbon dioxide-ethylene * V

glycol and carbon dioxide-propylene carbonate is negative also, and

al$ so it would be expected that they also have ( ‘£yp)«j which is nega¬

tive.

av 8n l7n2,T,P

16 -

Hydrogen bonding would seem to give a physical explanation

of the negative v. For the case of hydrogen sulfide-ethylene glycol

the cause may be that the hydrogen sulfide and ethylene glycol con¬

tain donor atoms (S,0) and active hydrogens. These molecules evi¬

dently attract each other and produce bonding between a donor of

one compound and an active hydrogen of the other compound.

The system carbon dioxide-ethylene glycol is also composed of

a compound containing donor atoms (0) and the glycol. Again the bond¬

ing would be between the oxygen donors of carbon dioxide and the active

hydrogens on the glycol.

The case of propylene carbonate-carbon dioxide is different

in character. The active hydrogens necessary for bonding must exist

on the carbon atoms of the propylene carbonate. While the carbon

atom is not classed as a donor, the presence of the carbonate group

may cause the hydrogens on carbons adjacent to the carbonate group to

— 0\ become active. In this case the Q/^~ 0 acts as a carbonate

radical attached to an organic compound.

17 -

DATA

Table I

Experimental Data

Methane-Propylene Carbonate

Temperature Pressure Solubility Mole Fraction psia vol. gas (25 , 760)

per vol. liquid

80°F 1767 19.70 .0351 1486 17.36 .0310 1029 13.00 .0234 532 7.40 .0135 261 3.83 .0070

100°F 1701 19.91 .0354 1355 16.44 .0294 1281 15.51 .0278 1041 13.19 .0238 642 8.69 .0158

160°F 1999 23.45 .0415 1387 17.80 .0318 1005 13.23 .0238 587 8.28 .0151

220°F 1912 24.70 .0436 1392 18.88 .0337 988 13.50 .0243

Carbon Dioxide-Propylene Carbonate

80°F 805 495.9 .425 799 387.7 .414 787 376.5 .407 641 268.5 .329 469 159.3 .225 285 85.8 .135

100 °F 877 278.8 .337 793 235.7 .301 642 171.1 .238 489 121.3 .181 335 76.1 .122

160 °F 1001 153.9 .219 885 133.6 .196 717 98.0 il52 573 77.9 .124 435 58.4 .096

18

Table X (cont.)

220°F 895 82.93 .131 685 63.15 .103 311 28.06 .049

Carbon Dioxide-Ethy1ene Glycol

78°F 899 56.99 .113 700 45.80 .093 509 33:04 .069 219 14.84 .032

100°F 895 44:29 .091 635 33.00 .068 356 18.60 .040

160°F 1009 32.09 .067 641 20.38 .043

220°F . 1057 26.39 .055 605 15.15 .033 271 6.73 .015

hydrogen Sulfide-Ethylene Glycol

84°F 340 314.9 .419 310 255.9 .370 270 188.6 .302 275 200.6 >315 235 155.5 .263 165 99.0 .186

100°F 405 365.9 .456 370 263.7 .377 295 145.9 .251 220 104.4 .193

160°F 780 528.2 .548 595 229.1 .344 215 63.6 .127

19 -

Table II

Experimental Data (graphically smooth)

Temperature Pressure - Mole Fraction psia Graphic Thermodynamic

Methane-Propylene Carbonate

80°F 1767 .0351 .0357 1600 .0329 .0332 1200 ,0264 .0269 800 .0190 .0194 400 .0102 .0105

100°F 1700 .0354 .0358 1600 .0338 .0343 1200 .0268 .0275 800 .0190 . .0197 400 .0102 .0106

160°F 2000 .0415 .0437 1600 .0358 .0367 1200 .0280 .0284

800 .0195 .0203 400 .0104 .0107

220°F 1800 .0417 .0423 1600 .0379 .0385 1200 .0292 .0300 800 .0199 .0208 400 .0105 .0108

Carbon Dioxide-Propylene Carbonate

80°F 800 .415 .412 600 .300 .307 400 .194 .199 200 .095 .093

100°F 850 .325 .325 800 .303 .301 600 .222 .224 400 ■ .141 .145 200 .073 .069

160°F 1000 .219 .220 800 .173 .179 600 .130 .138 400 .088 .092 200 .046 .045

220°F 895 .132 .130 800 .119 .117 600 .093 .090 400 .065 .061 200 .033 .031

20

Table IX (cont'd.)

Carbon Dioxide-Ethylene Glycol

78°F 900 .1125 m m

800 .1033 .101 600 .0812 .081 400 .0560 .057 200 .0290 .029

100°F 895 .091 .091 800 ;083 .082 600 .065 .065 400 .044 .045 200 .023 .023

160°F 1000 .0665 .0663 800 .0535 .0529 600 .0405 .0405 400 .0272 .0262 200 .0140 .0134

220°F 1000 .0532 .0525 800 .0426 .0420 600 .0320 .0324 400 .0215 .0219 200 .0110 .0111

Hydrogen Sulfide-Ethylene Glycol

84°F 340 .340 .419 310 .324 .370 270 .292 .302 275 .298 .315 235 .256 .263 165 .187 .186

100°F 405 .309 .456 370 .296 .377 295 .250 .251 220 .190 .193

160°F 780 .426 .548 595 .346 .344 215 .128 .127

21

Table III

Activity Coefficients for Hydrogen Sulfide in Ethylene Glycol

Temperature Pressure Activity Coefficient

84°F 340 2.40 300 2.72 250 3.82 200 4.01 150 4.29 100 4.41 50 4.63

100°F 404 2.18 350 2.61 300 2.88 200 3.26 100 3.51

160°F 780 1.84 700 2.16 600 2.35 500 2.45 400 2.53 300 2.62 200 2.71 100 2.79

22

Table IV

Constants for use in the equation of Krischevsky:

Temperature

(7) Log (K)

Methane-Propylene Carbonate

80, 100, 160, 220°F 4.548

v

(ft3/lb. mole)

.479

Carbon Dioxide-Propylene Carbonate

80) 100 160 220

3.351 3.471 3.626 3.799

-3.50 -2.80 -1.05 -0.483

Carbon Dioxide-Ethylene Glycol

78 100 .160 220

3.820 -1.21 3.928 -0.97 4.175 -1.50 4.251 -0.720

Hydrogen.Sulfide-Ethylene Glycol

84 100 160

2.954 3.042 3.217

-3.04 -1.67 -1.70

23 -

FIGURES

FIG

UR

E I. S

CH

EM

AT

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LITERATURE CITED

1. Case: Elements of the Phase Rule, the Edward's Book Shop, Ann Arbor,, Michigan, (1939).

2. Deming; Phys. Rev., 56, 108-12, (1939).

3. Dodge; Chemical Engineering Thermodynamics; McGraw Hill Book Co., Inc., New York, (1944).

4. Ewell, Harrison, and Berg; Ind. Eng. Chem., 36, 871, (1944).

5. Hala, Pick, Fried, Vilih;. Vapor Liquid Equilibrium; Pergamon Press, New York, (1958).

6. Johnson and Francis; Ind. Eng. Chem., 46, 8, 1662, (1954).

7. Katz and Donnelly; Ind. Eng. Chem., 46, 511-17 (1954).

8. Katz and Rzasa; Bibliography for Physical Behavior of Hydro¬ carbons Under Pressure and Related Phenomena; T. W. Edwards, Inc., Ann Arbor, Michigan, (1946),

9. Kobayashi; Ph. D. Thesis, University of Michigan, (1951).

10. Krischevsky and Kasarnovasky; J. Am. Chem. Soc.-, 57, 2168, (1935).

11. Lecat; Amn. Soc. Sci. Bruxelles, 48; B, I, 13 (1928).

12. Lecat; Rec. Trav. Chim., 46, 240 (1926).

13. Lecat; Tables Azeotro'piques, Brussels, l'Auteur, July (1949).

14. Leland, McKetta, and Kobe; Ind. Eng. Chem., 1265, 47, 6 (1955)

15. Perry, Chemical Engineers Handbook; Third Edition, Mc(Jraw Hill Book Co., Inc., New York, (1950).

16. Porter and Reid; A. I. M. E. Trans. 189, 235, (1950).

17. J. S. Rowlinson; Liquids and Liquid Mixtures; Academic Press, Inc., New York, N. Y., (1959).

18. Rowlinson, J. s.; Quart. Revs.; 8/ 168-41, (1954).

19. Russeil, Reid, and Huntington; A.I.Ch.E. Trans., 41, 313-325, June (1945).

20. Sage and Lacey; Apparatus for Study of P-V-T Relations of Liquids and Gases; Trans. A.I.M.E. 136, 136, (1940).

21. Sage and Lacey; Some Properties of Hydrocarbons; American Petroleum Institute, New York, (1955).

22. Sage and Lacey; Thermodynamic Properties of Hydrocarbons; American Petroleum Institute, New York, (1950).

23. Williams, Ph. D. Thesis, University of Michigan, (1954).

APPENDIX A

Special Method of Test for Ethylene Glycol and Propylene Glycol

This method is intended for use in,determining ethylene

glycol or propylene glycol in water solutions which might contain

diethylene glycol, triethylene glycol, ethylene carbonate and pro¬

pylene carbonate. The method will handle from 20 to 130 mg. of

ethylene glycol or from 25 to 150 mg. of propylene glycol with an

accuracy of about 0.5 per cent. Ethylene oxide, considerable ace¬

taldehyde and oxidizing agents interfere.

Outline of Methods:

The method depends upon the oxidation of 1, 2-glycols

with periodic acid. The excess periodic acid is reduced with

sodium arsenite and the unreacted sodium arsenite is titrated with

standard iodine solution. Approximately thirty minutes are required

to complete a determination.

Apparatus:

a. Erlemeyer flasks, 500-ml.

b. Pipets, 25-ml., 50-ml., automatic.

c. Graduated cylinders, 50-ml. and 10-ml.

d. Buret, 50-ml.

Reagents:

a. Periodic acid solution.

b. podium bicarbonate solution, aqueous, saturated

c. Sodium arsenite solution.

d. Potassium iodide solution, approximately 10 per cent.

e. Starch solution; fresh, 1% soluble starch in water.

f. Iodine, 0.1 N standard solution.

Procedure:

Introduce a sample containing 20 to 130 mg. of ethylene gly¬

col or 25 to 150 mg. propylene glycol into a ,500-ml. Erlenmeyer flask.

Dilute with distilled water to approximately 50 ml. To a similar flask

to be used for a blank run add a volume of distilled water approximately

equal to the volume of sample dilution.

To each flask add from the automatic pipet, 25 ml. of periodic

acid solution. Swirl to mix and let stand for fifteen minutes. From a

graduated cylinder add 40 ml. of sodium bicarbonate solution. Add from

an automatic pipet 5 ml. of sodium arsenite solution. Add approximately

two ml. of ten per cent potassium iodide solution to the first appear¬

ance of a permanent blue.

Calculations:

Let A equal ml. of iodine solution used for sample

B equal ml. of iodine solution used for blank N equal normality of iodine solution

Per cent ethylene glycol = 3.1035(N)(A-B)/ grams sample.

Per cent propylene glycol a 3.805(N)(A-B)/ grams sample.

APPENDIX B

Fugacity of Hydrogen Sulfide

Pressure 40°F 100°F

Fugacity 160°F 220°F

PSIA PSIA

100 90 92 96 98 200 151 180 186 190 300 152 258 270 278 400 154 316 347 360 500 156 322 417 438 600 158 328 480 510 700 160 332 538 576 800 162 336 578 639

Temperature Vapor Pressure Fugacity °F psia psia

40 171 151 100 404 320 160 779 576 220 ---