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Liquid-liquid phase equilibria in the 3-methyl-2-butanone-water system at high pressure
Fluid
Phase Equilibria,
Elsevier Scientific
6 (1981) 191-201 Publishing Company, Amsterdam
191 -- Printed
in The Netherlands
LIQUID-LIQUID PHASE EQUILIBRIA IN THE 3-METHYL-2BUTANONE-WATER SYSTEM AT HIGH PRESSURE
0. BOZDAG
and J.A. LAMB
Department of Chemical (Gt. Britain)
(Received
September
Engineering,
University
29th, 1980;accepted
of Surrey,
Guildford,
in revised form December
Surrey
29th, 1980)
ABSTRACT Bozdag, 0. and Lamb, J.A., 1981. Liquid-liquid phase equilibria in the 3-methyl-2butanone-water system at high pressure. Fluid Phase Equilibria, 6: 191-201. Mutual solubilities of 3-methyl-2-butanone and water determined analytically for temperatures from -8 to 18O’C at low pressure and from -8 to 90°C at pressures up to 350 MPa are reported together with ternary miscibility data at O’C and 40°C and ambient pressure for the system 3-methyl-2-butanone-water-propanone. The results obtained do not support earlier reports that 3-methyl-2-butanonelwater mixtures show two upper critical solubility pressures and one lower critical solubility pressure in an open miscibility loop but, rather, suggest solubility behaviour no different in kind from that of closely similar systems.
INTRODUCTION
Steiner and Schadow (1969) reported a study of the liquid phase miscibility behaviour of the binary system 3-methyl-2-butanone-water at 30, 45 and 60°C and pressures up to about 110 MPa. The method used relied on observing the change of turbidity of synthetic mixtures of the components with change in pressure. These mixtures were held in a small cell of 0.67 cm3 volume equipped with two sapphire windows and a stirrer, The appearance or disappearance of turbidity with isothermal pressure variation was used to infer the boundaries of the consolute envelopes. Qualitatively, the results of Steiner and Schadow are represented by Fig. :I in which the region of immiscibility is indicated by cross-hatching. A T%x diagram in the plane P = P’, then, corresponding to section ABCD of the T-Pdiagram, has the form indicated by Fig. 2. Figure 1 shows two upper critical solution pressures and one lower critical solution pressure in an open miscibility loop. The T-3c diagram at P = P’ shows the corresponding features of one upper critical solution temperature, 2’“) and two lower critical solution temperatures, TL1 and TL2. Extrapolation of the P(x) curves for the three temperatures given by Steiner and Schadow suggests that, at ambient pressures, the critical temper0378-3812/81/0000-0000/$02.50
@ 1981 Elsevier Scientific
Publishing
Company
D ‘..,
‘..,
‘,., ._ ‘...
‘._ ‘_ ‘.
C
0
COMPOSITION
-
Fig. 1. Apparent region of immiscibility Steiner and Schadow (1969) (schematic
of 3-methyl-2-butanone-water only).
according
to
atures may lie around -10 to +ZO”C. Such a system would show interesting properties over the temperature range between TL2 and T” . The inverse of this type of behaviour has been described by Skinner (1955) who examined the system 2,2’-thio-dipropionitrile-toluene at atmospheric pressure. This sytem appears to have two upper critical solution temperatures and one lower critical solution temperature. Francis and King (1958) initially described such behaviour as improbable but later Francis (1963) described it as theoretically impossible and suggested that experimental error is the cause of the appearance of the multiple extrema in the solubility envelope. Winnick and Powers (1963,1966) in their measurements of the miscibility of carbon disulphide and acetone at -2” C as a function of pressure, present results which may possibly show two lower critical solution pressures and one upper critical solution pressure, the inverse of the reported behaviour of 3-methyl-2-butanone-water mixtures, though, once again, the effect could be accounted for by experimental error. Winnick and Powers make no comment on this aspect of their findings.
193
TL1
T" TL:
t TEMP. COMPOSITION Fig. 2. Miscibility matic only).
-
loop at the constant
pressure,
P’, of the plane ABCD of Fig. 1 (sche-
It is worth emphasising that in each of these studies an optical method was used to detect the onset of miscibility. Steiner and Schadow, perhaps dissatisfied with the optical method, also applied a method of detecting phase separation in the 2-butanone-water system at elevated pressures which relied on measuring the isothermal change of dielectric constant of samples of synthetic mixtures with change in pressure. Unfortunately, their equipment could not be used for the range of dielectric constants shown by 3-methyl-2-butanone/water mixtures. However, the discrepancies between the results of optical and dielectric constant tests on the 2-butanone/water mixtures are sufficient to cast doubts upon the reliability of the rather scanty evidence for the multiple extrema indicated in Figs. 1 and 2. The work described here was intended primarily to add substance to the work of Steiner and Schadow on the system 3-methyl-2-butanone-water and relies upon analysis of conjugate phases in equilibrium rather than a synthetic method. While this method is not well-suited to finding upper and lower critical solution conditions, it does offer a different approach to the problem. EXPERIMENTAL
EQUIPMENT
AND METHOD
The test materials used were distilled and contained negligible impurities detectable by gas chromatography. For sample analyses, Porapak Q of SO/l00 mesh was used with helium carrier gas which gave good separation of water, methanol, propanone and
194
J
jl
F
HH'iEDC
B
G
Fig, 3. Schematic arrangement of equipment. A, cylinder; B, piston; C, ceramic ball; D, pressure vessel; E, pivot; F, thermostat tank; G., connection to pump and pressure gauge; H, H’, capillary tubes; J, J’ valves.
3-methyl-Zbutanone. Test materials were also analysed with Porapak T to obtain some assurance that no co-incident peaks were being missed, A good quality computing integrator with a dynamic range of lo6 to 1 capable of detecting fused and riding peaks was used. No test material was found to be worse than 99.3% pure. The equipment used for high pressure studies, shown in Fig. 3, consisted of a stainless steel cylinder, A, and piston, B, which contained about 80 cm3 of the liquid mixture to be investigated and a non-porous ceramic ball, C, which served as a stirrer. The piston was sealed by two 0 rings, that in contact with the mixture being of PTFE and the other of Neoprene. The piston-cylinder arrangement was placed in a pressure vessel, D, mounted in a rocking cradle and immersed in a thermostat tank, F. The hydraulic fluid used was distilled water containing sufficient methanol to depress the
195
freezing point below the lowest temperature used. Pressure was generated by a hand pump and measured with a calibrated Bourdon tube gauge. The test mixture could thus be pressurised, maintained at a constant temperature and stirred by causing the ceramic ball to roll from end to end of the cylinder. After adequate mixing to achieve equilibrium, the mixture was stood with the pressure vessel axis vertical to allow segregation of the two phases. Samples of the two layers were then withdrawn through a pair of 0.1 mm i.d. capillary tubes, H, H’, one of which communicated between the end of the cylinder and a three-way, high pressure valve, J, on the outside of the pressure vessel and the other between the piston and a similar external valve, J’. Samples could be taken roughly isobarically by injecting hydraulic fluid into the system as the samples were withdrawn. The sampling valves were flushed out with propanone, a mutual solvent, and the resulting homogeneous samples were analysed by gas chromatography. No trace of methanol, which would indicate an inleak of hydraulic fluid, was found. Ancillary to this main investigation of the phase behaviour of the system 3-methyl-2-butanone-water with increase of pressure, the liquid-liquid phase equilibrium behaviour of the ternary system 3-methyl-2-butanonewater-propanone was examined at 0 and 40” C at atmospheric pressure. Tie-line data were obtained by equilibrating mixtures and then withdrawing samples of the conjugate liquids into glass syringes partly filled with methanol, a solvent which ensures homogeneity. These samples were analysed by gas chromatography. Critical solution compositions were also found optically by the step-wise addition of measured quantities of propanone to vigorously stirred mixtures of known amounts of the other two components. The intensity of light transmitted by the mixutre from a stabilised-voltage tungsten lamp was measured with a photo-cell. The discontinuity found in the relationship between solvent added and photocell output was taken to correspond to the critical concentration of solvent. A similar technique was used to determine three critical solution temperatures of binary mixtures of 3-methyl-2-butanone and water using an optical cell capable of withstanding the vapour pressure of the mixtures. This cell was stirred by an internal impeller driven magnetically by a motor outside the cell. The discontinuity found in the relationship between photo-cell output and temperature was used as an index of the critical solution temperature. Temperatures were measured with calibrated mercury-in-glass thermometers estimated to be accurate to & 0.05”C. The pressure gauges used were described by the manufacturer as being accurate to + 1.2 MPa when hysteresis is allowed for. Mass fractions are estimated to be accurate to + 0.8%. RESULTS AND DISCUSSION
The binary system 3-methyl-2-butanone-water Table 1 summarises the results of the tie-line determinations made here for the binary system at various temperatures and pressures together with
196 TABLE 1 Conjugate compositions for 3-methyl-2-butanone( 1)-water as functions of temperatures and pressure Temp. (“C)
-8
Pressure (MPa)
0.1
0 10 10 * 20 20+ 25 25 + 30 30 t 30 * 40 50 50 * 60 70 80 85 90 110 120 130 140 150 160 170 180 -8
69.0
0 10 20 30 45 60 75 90 -8 0 10
137.9
Mass fraction 1 Lower layer
Upper layer
0.139 0.104 0.085 0.065 0.073 0.065 0.066 0.061 0.061 0.057 0.050 0.057 0.051 0.049 0.048 0.047 0.049 0.050 0.052 0.055 0.060 0.065 0.067 0.084 0.101 0.136 0.163
0.958
0.972 0.970 -
0.971 0.976
0.965 0.974 0.962 0.972 0.959 0.959 0.954 0.973
Pressure (MPa)
Mass fraction 1 Lower layer
Upper layer
0.112 0.089 0.070 0.058 0.050 0.060
0.953 0.952
0.328 0.237 0.185 0.123 0.094 0.084 0.069 0.059 0.062
0.899 0.935 0.936 0.942
0.941 0.927 0.923 0.912 0.920
275.8
0.415 0.316 0.215 0.137 0.112 0.094 0.077 0.065 0.066
0.843 0.888 0.918 0.934 0.926 0.920 0.910 0.909 0.895
0 10 20 45 60
310.3
0.342 0.244 0.159 0.092 0.081
0.868 0.891 0.927 0.908 0.902
0 10 20 30 45 60 75 90
344.7
0.384 0.274 0.171 0.127 0.096 0.083 0.075 0.072
0.832 0.886 0.921 0.915 0.903 0.897 0.886 0.859
20 30 45 60 75 90
137.9
-8
206.8
0 10 20 30 45 60 75 90
0.935 0.938 0.929
0.931
0.930 0.926 0.927 0.900 0.889
0.873 0.844 0.822 0.789 0.747 0.703
0.193 0.143 0.120 0.101 0.080 0.065 0.055 0.049 0.050
0.953 0.961 0.962 0.960 0.957 0.943 0.948 0.934 0.935
0.264 0.190 0.152
0.927 0.950 0.954
* Gross et al. (1939). + Ginnings et al. (1940).
Temp. (“C)
-8 0 10 20 30 45 60 75 90
197
200
t TEMP ‘C
0 ---___-M
MASS FRACTION KETONE -t
I
ATIE LINES: NORMAL PRESSURE oTIE LINES: P = 207 MN/m2 oTIE LINES: P = 345 MN/m* *CRITICAL SOLUTION TEMPERATURE:NORMAL PRESSURE Fig. 4. Miscibility
isotherms
for the system
3-methyl-2-butanone-water.
three tie-lines measured.by Ginnings et al. (1940) and three solubilities of the ketone in water given by Gross et al. (1939). These results show a fair agreement. A solid phase separates out just below -8” C. Limitations of the equipment used precluded working at pressures above 350 MPa or temperatures in excess of 90°C at elevated pressures. Within these constraints, the behaviour of the system appears to be similar to that of its homologue 2-butanone-water in that it shows a miscibility loop which is almost closed at normal pressures but in which the lower critical solution temperature is masked by freezing. As with 2-butanone-water (Timmermans, 1960; Hunt and Lamb, 1979), the miscibility gap becomes narrower as the pressure is
198
200 f PRESS. (MN/m2)
-
'
Fig. 5. Miscibility
isobars
MASS FRACTION KETONE
for the system
1
--t
3-methyl-Z-butanone-water.
increased. This is illustrated in Figs. 4 and 5 where several isobars are omitted for clarity. Good agreement was found at atmospheric pressure between the three critical solution temperatures found optically (cf. Table 2) and the results obtained by the analytical method. At all temperatures between -8 and +9O”C, increase of pressure caused increase in mutual solubility, but this was considerably less than that found by Steiner and Schadow. Although pressures were raised to levels three times higher than those used hitherto for this system, there was no sign of complete miscibility occurring, nor were any apparently anomalous samples taken which might correspond to a segment of miscibility loop lying between two upper critical solution pressures.
TABLE
2
Critical solution temperatures of 3-methyl-2-butanone-water method with solutions under their own vapour pressures Mass fraction
0.7011 0.7812 0.8661
ketone
Critical temperature PC) 178.0 157.8 133.2
determined
by optical
199
The ternary sys tern 3-me thy i-2-bu tanone-water-propanone Although extrapolation of Steiner and Schadow’s results for solutions containing 40 wt.% of ketone suggests that a homogeneous system might be achieved at around ambient pressure and temperature, two phases persisted when a 40% mixture was stirred at normal pressure and cooled to its freezing point around -8” C. It was with the hope that the unusual upper critical solution temperature T” of Fig. 2 was masked by the system freezing that the three component system 3-methyl-2-butanone-water-propanone was examined. It was hoped that the presence of the third component as solvent would bring about behaviour analogous to that resulting from increase of pressure. Tie-lines were determined at 0 and 40°C and are reported in Table 3. The results TABLE
3
Conjugate
solutions
in the system
3-methyl-2-butanone-water-propanone
at normal
pressure Temperature (“C)
40
0
Lower
Upper layer
layer
Mass fraction C5 ketone
Mass fraction water
Mass fraction Cb ketone
Mass fraction water
0.715 0.707 0.700 0.652 0.637 0.615 0.580 0.574 0.532 0.514 0.513 0.466 0.465 0.347
0.068 0.072 0.071 0.084 0.086 0.093 0.102 0.108 0.119 0.140 0.135 0.161 0.152 0.262
0.084
0.761 0.768 0.769 0.723 0.710
0.872 0.850 0.799 0.770 0.742 0.693 0.685 0.633 0.615 0.551 0.538 0.454
0.032 0.045 0.044 0.066 0.053 0.058 0.059 0.075 0.087 0.123 0.113 0.157
0.085 0.088 0.094 0.098 0.104 0.107 0.115 0.115 0.117 0.129 0.162 0.185
0.676 0.664 0.639 0.636 0.620 0.596 0.540 0.479
0.122 0.119 0.121 0.125 0.122 0.128 0.137 0.135 0.147 0.167 -
0.785 0.779 0.725 0.720 0.694 0.651 0.640 0.617 0.587 0.532 -
0.220
0.425
200
/
\
KETONE A = 3-METHYl-Z-B~~~A~n~~ 0 ANALYTICAL, 40°C 0 SYNTHETIC (OPTICAL),40°C KETONE A = 4-METHYL-E-PENTANONn SYsJTHETIC (OPTICAL),25'C
WATER
KETONE A
Fig. 6. Liquid-liquid equilibria at 40°C and natural pressure in the system 3-methyl-2butanone-water-propanone. The miscibility loop of 4-methyl-2-pentanone-waterpropanone at 25’C (Othmer et al., 1941) also shown.
TABLE 4 Critical compositions of solutions of 3-methyl-2-butanonepressures and 40°C determined by optical method
-waterpropanone
at normal
Mass fraction Cs ketone
Mass fraction water
Mass fraction C5 ketone
Mass fraction water
Mass fraction C5 ketone
Mass fraction water
0.306 0,287 0.263 0.243 0.249 0.216
0.310 0.337 0.364 0.392 0.383 0.430
0.202 0,192 0.185 0.148 0.147 0.130
0.450 0.466 IO.507 0.549 0.554 0.588
0.122 0,099 0.652 0.437 0.337 0.274
0.607 0.655 0.098 0.176 0.273 0.366
201
obtained at 40” C are graphed in Fig. 6. Optical determination of upper critical solution concentrations of propanone at 40” C are reported in Table 4. These points are shown on Fig. 6 and agree well with the analytical results. The consolute envelope at 25°C for the homologous system 4-methyl-2-pentanone-water-propanone reported by Othmer et al. (1941) is shown in Fig, 6 and this conforms with the general shape of the consolute curve reported here. CONCLUSION
The present authors have found no evidence that the system 3-methyl-2butanone-water shows solubility behaviour which is significantly different in kind from that of closely similar systems. They are thus unable to confirm the findings of Steiner and Shadow. There appears to be no difficulty in getting agreement between optical and analytical techniques for deducing phase envelopes in this system at low pressures, though this does not preclude the possibility of problems at elevated pressures. ACKNOWLEDGEMENT
One of us (0. Bozdag) wishes to record his gratitude to the Turkish Ministry of Education for the financial support received while carrying out this work. REFERENCES
Francis, A.W., 1963. Liquid-liquid Equilibriums. Interscience, New York. Francis, A.W. and King, W.H., 1958. Solvent refining. Adv. Pet. Eng. Refin., 1: 428-484. Ginnings, P.M., Plonk, D. and Carter, E., 1940. Aqueous solubilities of some aliphatic ketones. J. Am. Chem. Sot., 62: 19.23-1924. Gross, P.M., Rintelen, J.C. and Saylor, J.H., 1939. Energy and volume relations in the solubilities of some ketones in water. J. Phys. Chem., 43: 196-205. Hunt, A;F. and Lamb, J.A., 1979. Liquid-liquid phase equilibrium in the 2-butanonewater system at high pressure. Fluid Phase Equilibria, 3: 177-184. Othmer, A.F., White, R.F. and Trueger, E., 1941. Liquid-liquid extraction data. Ind. Eng, Chem., 33: 1240-1248. Skinner, D.A., 1955. Selective solvents for aromatic hydrocarbons. Ind. Eng. Chem., 47: 222-229. Steiner, R. and Schadow, E., 1969. Visuelle und dekametrische Bestimmung von Phaaengleichgewichten nichtmischbarer Fliissigkeitein unter Hochdruck. Z. Phys. Chem. N.F., 63: 297-311. Timmermans, J., 1960. The Physico-Chemical Constants of Binary Systems in Concentrated Solutions, Vol. 4. Interscience, New York. Winnick, J., 1963. Liquid phase behaviour of binary solutions at elevated pressures. Ph.D. Dissertation, University of Oklahoma. Winnick, J. and Powers, J.D., 1966. Liquid-liquid phase behavior of binary solutions of elevated pressures. AIChE J., 12: 466-472.
Phase Equilibria,
Elsevier Scientific
6 (1981) 191-201 Publishing Company, Amsterdam
191 -- Printed
in The Netherlands
LIQUID-LIQUID PHASE EQUILIBRIA IN THE 3-METHYL-2BUTANONE-WATER SYSTEM AT HIGH PRESSURE
0. BOZDAG
and J.A. LAMB
Department of Chemical (Gt. Britain)
(Received
September
Engineering,
University
29th, 1980;accepted
of Surrey,
Guildford,
in revised form December
Surrey
29th, 1980)
ABSTRACT Bozdag, 0. and Lamb, J.A., 1981. Liquid-liquid phase equilibria in the 3-methyl-2butanone-water system at high pressure. Fluid Phase Equilibria, 6: 191-201. Mutual solubilities of 3-methyl-2-butanone and water determined analytically for temperatures from -8 to 18O’C at low pressure and from -8 to 90°C at pressures up to 350 MPa are reported together with ternary miscibility data at O’C and 40°C and ambient pressure for the system 3-methyl-2-butanone-water-propanone. The results obtained do not support earlier reports that 3-methyl-2-butanonelwater mixtures show two upper critical solubility pressures and one lower critical solubility pressure in an open miscibility loop but, rather, suggest solubility behaviour no different in kind from that of closely similar systems.
INTRODUCTION
Steiner and Schadow (1969) reported a study of the liquid phase miscibility behaviour of the binary system 3-methyl-2-butanone-water at 30, 45 and 60°C and pressures up to about 110 MPa. The method used relied on observing the change of turbidity of synthetic mixtures of the components with change in pressure. These mixtures were held in a small cell of 0.67 cm3 volume equipped with two sapphire windows and a stirrer, The appearance or disappearance of turbidity with isothermal pressure variation was used to infer the boundaries of the consolute envelopes. Qualitatively, the results of Steiner and Schadow are represented by Fig. :I in which the region of immiscibility is indicated by cross-hatching. A T%x diagram in the plane P = P’, then, corresponding to section ABCD of the T-Pdiagram, has the form indicated by Fig. 2. Figure 1 shows two upper critical solution pressures and one lower critical solution pressure in an open miscibility loop. The T-3c diagram at P = P’ shows the corresponding features of one upper critical solution temperature, 2’“) and two lower critical solution temperatures, TL1 and TL2. Extrapolation of the P(x) curves for the three temperatures given by Steiner and Schadow suggests that, at ambient pressures, the critical temper0378-3812/81/0000-0000/$02.50
@ 1981 Elsevier Scientific
Publishing
Company
D ‘..,
‘..,
‘,., ._ ‘...
‘._ ‘_ ‘.
C
0
COMPOSITION
-
Fig. 1. Apparent region of immiscibility Steiner and Schadow (1969) (schematic
of 3-methyl-2-butanone-water only).
according
to
atures may lie around -10 to +ZO”C. Such a system would show interesting properties over the temperature range between TL2 and T” . The inverse of this type of behaviour has been described by Skinner (1955) who examined the system 2,2’-thio-dipropionitrile-toluene at atmospheric pressure. This sytem appears to have two upper critical solution temperatures and one lower critical solution temperature. Francis and King (1958) initially described such behaviour as improbable but later Francis (1963) described it as theoretically impossible and suggested that experimental error is the cause of the appearance of the multiple extrema in the solubility envelope. Winnick and Powers (1963,1966) in their measurements of the miscibility of carbon disulphide and acetone at -2” C as a function of pressure, present results which may possibly show two lower critical solution pressures and one upper critical solution pressure, the inverse of the reported behaviour of 3-methyl-2-butanone-water mixtures, though, once again, the effect could be accounted for by experimental error. Winnick and Powers make no comment on this aspect of their findings.
193
TL1
T" TL:
t TEMP. COMPOSITION Fig. 2. Miscibility matic only).
-
loop at the constant
pressure,
P’, of the plane ABCD of Fig. 1 (sche-
It is worth emphasising that in each of these studies an optical method was used to detect the onset of miscibility. Steiner and Schadow, perhaps dissatisfied with the optical method, also applied a method of detecting phase separation in the 2-butanone-water system at elevated pressures which relied on measuring the isothermal change of dielectric constant of samples of synthetic mixtures with change in pressure. Unfortunately, their equipment could not be used for the range of dielectric constants shown by 3-methyl-2-butanone/water mixtures. However, the discrepancies between the results of optical and dielectric constant tests on the 2-butanone/water mixtures are sufficient to cast doubts upon the reliability of the rather scanty evidence for the multiple extrema indicated in Figs. 1 and 2. The work described here was intended primarily to add substance to the work of Steiner and Schadow on the system 3-methyl-2-butanone-water and relies upon analysis of conjugate phases in equilibrium rather than a synthetic method. While this method is not well-suited to finding upper and lower critical solution conditions, it does offer a different approach to the problem. EXPERIMENTAL
EQUIPMENT
AND METHOD
The test materials used were distilled and contained negligible impurities detectable by gas chromatography. For sample analyses, Porapak Q of SO/l00 mesh was used with helium carrier gas which gave good separation of water, methanol, propanone and
194
J
jl
F
HH'iEDC
B
G
Fig, 3. Schematic arrangement of equipment. A, cylinder; B, piston; C, ceramic ball; D, pressure vessel; E, pivot; F, thermostat tank; G., connection to pump and pressure gauge; H, H’, capillary tubes; J, J’ valves.
3-methyl-Zbutanone. Test materials were also analysed with Porapak T to obtain some assurance that no co-incident peaks were being missed, A good quality computing integrator with a dynamic range of lo6 to 1 capable of detecting fused and riding peaks was used. No test material was found to be worse than 99.3% pure. The equipment used for high pressure studies, shown in Fig. 3, consisted of a stainless steel cylinder, A, and piston, B, which contained about 80 cm3 of the liquid mixture to be investigated and a non-porous ceramic ball, C, which served as a stirrer. The piston was sealed by two 0 rings, that in contact with the mixture being of PTFE and the other of Neoprene. The piston-cylinder arrangement was placed in a pressure vessel, D, mounted in a rocking cradle and immersed in a thermostat tank, F. The hydraulic fluid used was distilled water containing sufficient methanol to depress the
195
freezing point below the lowest temperature used. Pressure was generated by a hand pump and measured with a calibrated Bourdon tube gauge. The test mixture could thus be pressurised, maintained at a constant temperature and stirred by causing the ceramic ball to roll from end to end of the cylinder. After adequate mixing to achieve equilibrium, the mixture was stood with the pressure vessel axis vertical to allow segregation of the two phases. Samples of the two layers were then withdrawn through a pair of 0.1 mm i.d. capillary tubes, H, H’, one of which communicated between the end of the cylinder and a three-way, high pressure valve, J, on the outside of the pressure vessel and the other between the piston and a similar external valve, J’. Samples could be taken roughly isobarically by injecting hydraulic fluid into the system as the samples were withdrawn. The sampling valves were flushed out with propanone, a mutual solvent, and the resulting homogeneous samples were analysed by gas chromatography. No trace of methanol, which would indicate an inleak of hydraulic fluid, was found. Ancillary to this main investigation of the phase behaviour of the system 3-methyl-2-butanone-water with increase of pressure, the liquid-liquid phase equilibrium behaviour of the ternary system 3-methyl-2-butanonewater-propanone was examined at 0 and 40” C at atmospheric pressure. Tie-line data were obtained by equilibrating mixtures and then withdrawing samples of the conjugate liquids into glass syringes partly filled with methanol, a solvent which ensures homogeneity. These samples were analysed by gas chromatography. Critical solution compositions were also found optically by the step-wise addition of measured quantities of propanone to vigorously stirred mixtures of known amounts of the other two components. The intensity of light transmitted by the mixutre from a stabilised-voltage tungsten lamp was measured with a photo-cell. The discontinuity found in the relationship between solvent added and photocell output was taken to correspond to the critical concentration of solvent. A similar technique was used to determine three critical solution temperatures of binary mixtures of 3-methyl-2-butanone and water using an optical cell capable of withstanding the vapour pressure of the mixtures. This cell was stirred by an internal impeller driven magnetically by a motor outside the cell. The discontinuity found in the relationship between photo-cell output and temperature was used as an index of the critical solution temperature. Temperatures were measured with calibrated mercury-in-glass thermometers estimated to be accurate to & 0.05”C. The pressure gauges used were described by the manufacturer as being accurate to + 1.2 MPa when hysteresis is allowed for. Mass fractions are estimated to be accurate to + 0.8%. RESULTS AND DISCUSSION
The binary system 3-methyl-2-butanone-water Table 1 summarises the results of the tie-line determinations made here for the binary system at various temperatures and pressures together with
196 TABLE 1 Conjugate compositions for 3-methyl-2-butanone( 1)-water as functions of temperatures and pressure Temp. (“C)
-8
Pressure (MPa)
0.1
0 10 10 * 20 20+ 25 25 + 30 30 t 30 * 40 50 50 * 60 70 80 85 90 110 120 130 140 150 160 170 180 -8
69.0
0 10 20 30 45 60 75 90 -8 0 10
137.9
Mass fraction 1 Lower layer
Upper layer
0.139 0.104 0.085 0.065 0.073 0.065 0.066 0.061 0.061 0.057 0.050 0.057 0.051 0.049 0.048 0.047 0.049 0.050 0.052 0.055 0.060 0.065 0.067 0.084 0.101 0.136 0.163
0.958
0.972 0.970 -
0.971 0.976
0.965 0.974 0.962 0.972 0.959 0.959 0.954 0.973
Pressure (MPa)
Mass fraction 1 Lower layer
Upper layer
0.112 0.089 0.070 0.058 0.050 0.060
0.953 0.952
0.328 0.237 0.185 0.123 0.094 0.084 0.069 0.059 0.062
0.899 0.935 0.936 0.942
0.941 0.927 0.923 0.912 0.920
275.8
0.415 0.316 0.215 0.137 0.112 0.094 0.077 0.065 0.066
0.843 0.888 0.918 0.934 0.926 0.920 0.910 0.909 0.895
0 10 20 45 60
310.3
0.342 0.244 0.159 0.092 0.081
0.868 0.891 0.927 0.908 0.902
0 10 20 30 45 60 75 90
344.7
0.384 0.274 0.171 0.127 0.096 0.083 0.075 0.072
0.832 0.886 0.921 0.915 0.903 0.897 0.886 0.859
20 30 45 60 75 90
137.9
-8
206.8
0 10 20 30 45 60 75 90
0.935 0.938 0.929
0.931
0.930 0.926 0.927 0.900 0.889
0.873 0.844 0.822 0.789 0.747 0.703
0.193 0.143 0.120 0.101 0.080 0.065 0.055 0.049 0.050
0.953 0.961 0.962 0.960 0.957 0.943 0.948 0.934 0.935
0.264 0.190 0.152
0.927 0.950 0.954
* Gross et al. (1939). + Ginnings et al. (1940).
Temp. (“C)
-8 0 10 20 30 45 60 75 90
197
200
t TEMP ‘C
0 ---___-M
MASS FRACTION KETONE -t
I
ATIE LINES: NORMAL PRESSURE oTIE LINES: P = 207 MN/m2 oTIE LINES: P = 345 MN/m* *CRITICAL SOLUTION TEMPERATURE:NORMAL PRESSURE Fig. 4. Miscibility
isotherms
for the system
3-methyl-2-butanone-water.
three tie-lines measured.by Ginnings et al. (1940) and three solubilities of the ketone in water given by Gross et al. (1939). These results show a fair agreement. A solid phase separates out just below -8” C. Limitations of the equipment used precluded working at pressures above 350 MPa or temperatures in excess of 90°C at elevated pressures. Within these constraints, the behaviour of the system appears to be similar to that of its homologue 2-butanone-water in that it shows a miscibility loop which is almost closed at normal pressures but in which the lower critical solution temperature is masked by freezing. As with 2-butanone-water (Timmermans, 1960; Hunt and Lamb, 1979), the miscibility gap becomes narrower as the pressure is
198
200 f PRESS. (MN/m2)
-
'
Fig. 5. Miscibility
isobars
MASS FRACTION KETONE
for the system
1
--t
3-methyl-Z-butanone-water.
increased. This is illustrated in Figs. 4 and 5 where several isobars are omitted for clarity. Good agreement was found at atmospheric pressure between the three critical solution temperatures found optically (cf. Table 2) and the results obtained by the analytical method. At all temperatures between -8 and +9O”C, increase of pressure caused increase in mutual solubility, but this was considerably less than that found by Steiner and Schadow. Although pressures were raised to levels three times higher than those used hitherto for this system, there was no sign of complete miscibility occurring, nor were any apparently anomalous samples taken which might correspond to a segment of miscibility loop lying between two upper critical solution pressures.
TABLE
2
Critical solution temperatures of 3-methyl-2-butanone-water method with solutions under their own vapour pressures Mass fraction
0.7011 0.7812 0.8661
ketone
Critical temperature PC) 178.0 157.8 133.2
determined
by optical
199
The ternary sys tern 3-me thy i-2-bu tanone-water-propanone Although extrapolation of Steiner and Schadow’s results for solutions containing 40 wt.% of ketone suggests that a homogeneous system might be achieved at around ambient pressure and temperature, two phases persisted when a 40% mixture was stirred at normal pressure and cooled to its freezing point around -8” C. It was with the hope that the unusual upper critical solution temperature T” of Fig. 2 was masked by the system freezing that the three component system 3-methyl-2-butanone-water-propanone was examined. It was hoped that the presence of the third component as solvent would bring about behaviour analogous to that resulting from increase of pressure. Tie-lines were determined at 0 and 40°C and are reported in Table 3. The results TABLE
3
Conjugate
solutions
in the system
3-methyl-2-butanone-water-propanone
at normal
pressure Temperature (“C)
40
0
Lower
Upper layer
layer
Mass fraction C5 ketone
Mass fraction water
Mass fraction Cb ketone
Mass fraction water
0.715 0.707 0.700 0.652 0.637 0.615 0.580 0.574 0.532 0.514 0.513 0.466 0.465 0.347
0.068 0.072 0.071 0.084 0.086 0.093 0.102 0.108 0.119 0.140 0.135 0.161 0.152 0.262
0.084
0.761 0.768 0.769 0.723 0.710
0.872 0.850 0.799 0.770 0.742 0.693 0.685 0.633 0.615 0.551 0.538 0.454
0.032 0.045 0.044 0.066 0.053 0.058 0.059 0.075 0.087 0.123 0.113 0.157
0.085 0.088 0.094 0.098 0.104 0.107 0.115 0.115 0.117 0.129 0.162 0.185
0.676 0.664 0.639 0.636 0.620 0.596 0.540 0.479
0.122 0.119 0.121 0.125 0.122 0.128 0.137 0.135 0.147 0.167 -
0.785 0.779 0.725 0.720 0.694 0.651 0.640 0.617 0.587 0.532 -
0.220
0.425
200
/
\
KETONE A = 3-METHYl-Z-B~~~A~n~~ 0 ANALYTICAL, 40°C 0 SYNTHETIC (OPTICAL),40°C KETONE A = 4-METHYL-E-PENTANONn SYsJTHETIC (OPTICAL),25'C
WATER
KETONE A
Fig. 6. Liquid-liquid equilibria at 40°C and natural pressure in the system 3-methyl-2butanone-water-propanone. The miscibility loop of 4-methyl-2-pentanone-waterpropanone at 25’C (Othmer et al., 1941) also shown.
TABLE 4 Critical compositions of solutions of 3-methyl-2-butanonepressures and 40°C determined by optical method
-waterpropanone
at normal
Mass fraction Cs ketone
Mass fraction water
Mass fraction C5 ketone
Mass fraction water
Mass fraction C5 ketone
Mass fraction water
0.306 0,287 0.263 0.243 0.249 0.216
0.310 0.337 0.364 0.392 0.383 0.430
0.202 0,192 0.185 0.148 0.147 0.130
0.450 0.466 IO.507 0.549 0.554 0.588
0.122 0,099 0.652 0.437 0.337 0.274
0.607 0.655 0.098 0.176 0.273 0.366
201
obtained at 40” C are graphed in Fig. 6. Optical determination of upper critical solution concentrations of propanone at 40” C are reported in Table 4. These points are shown on Fig. 6 and agree well with the analytical results. The consolute envelope at 25°C for the homologous system 4-methyl-2-pentanone-water-propanone reported by Othmer et al. (1941) is shown in Fig, 6 and this conforms with the general shape of the consolute curve reported here. CONCLUSION
The present authors have found no evidence that the system 3-methyl-2butanone-water shows solubility behaviour which is significantly different in kind from that of closely similar systems. They are thus unable to confirm the findings of Steiner and Shadow. There appears to be no difficulty in getting agreement between optical and analytical techniques for deducing phase envelopes in this system at low pressures, though this does not preclude the possibility of problems at elevated pressures. ACKNOWLEDGEMENT
One of us (0. Bozdag) wishes to record his gratitude to the Turkish Ministry of Education for the financial support received while carrying out this work. REFERENCES
Francis, A.W., 1963. Liquid-liquid Equilibriums. Interscience, New York. Francis, A.W. and King, W.H., 1958. Solvent refining. Adv. Pet. Eng. Refin., 1: 428-484. Ginnings, P.M., Plonk, D. and Carter, E., 1940. Aqueous solubilities of some aliphatic ketones. J. Am. Chem. Sot., 62: 19.23-1924. Gross, P.M., Rintelen, J.C. and Saylor, J.H., 1939. Energy and volume relations in the solubilities of some ketones in water. J. Phys. Chem., 43: 196-205. Hunt, A;F. and Lamb, J.A., 1979. Liquid-liquid phase equilibrium in the 2-butanonewater system at high pressure. Fluid Phase Equilibria, 3: 177-184. Othmer, A.F., White, R.F. and Trueger, E., 1941. Liquid-liquid extraction data. Ind. Eng, Chem., 33: 1240-1248. Skinner, D.A., 1955. Selective solvents for aromatic hydrocarbons. Ind. Eng. Chem., 47: 222-229. Steiner, R. and Schadow, E., 1969. Visuelle und dekametrische Bestimmung von Phaaengleichgewichten nichtmischbarer Fliissigkeitein unter Hochdruck. Z. Phys. Chem. N.F., 63: 297-311. Timmermans, J., 1960. The Physico-Chemical Constants of Binary Systems in Concentrated Solutions, Vol. 4. Interscience, New York. Winnick, J., 1963. Liquid phase behaviour of binary solutions at elevated pressures. Ph.D. Dissertation, University of Oklahoma. Winnick, J. and Powers, J.D., 1966. Liquid-liquid phase behavior of binary solutions of elevated pressures. AIChE J., 12: 466-472.