Vapor-liquid-liquid equilibria for the propane-furfural and propylene-furfural systems

Fluid Phase Equilibria, 81 (1992) 205-215

205

Elsevier Science Publishers B.V., Amsterdam

Vapor -liquid-liquid equilibria for the propane - furfural and propylene - furfural systems Katsuji Noda, Hitomu Watanabe and Shinji Iwamoto Department of Chemical Engineering, Shizuoka University, Hamamatsu 432 (Japan)

(Received December 27, 1991; accepted in final form April 19, 1992)

ABSTRACT Noda, IL, Watanabe, H. and Iwamoto, S., 1992. Vapor-liquid-liquid equilibria for the propane-furfural and propylene-furfural systems. Fluid Phase Equilibria, 81: 205-215. Vapor-liquid .equilibrium data are obtained for the propane-furfural and propylenefurfural systems at 293.15 and 313.15 K, using the static method. Mutual solubilities of these systems are also obtained using the analytical (weighing) method. Experimental vapor-liquid equilibrium data, including those for a three-phase system, are compared with calculated values using the UNIQUAC equation. The simultaneous correlation of vapor-liquid and liquid-liquid equilibria is fairly good. Vapor-liquid-liquid QUAC equation

equilibria; propane-furfural

system; propylene-furfural

system; UNI-

INTRODUCTION

Vapor-liquid equilibrium data are useful not only for the design of separation equipment, but also for understanding the properties of liquid mixtures. It is often difficult at present to correlate or to estimate satisfactorily vapor-liquid equilibria for partially miscible systems which have a large deviation from Raoult’s law. Therefore, it is important to obtain accurate data for vapor-liquid and liquid-liquid-vapor equilibria for complex systems. This paper presents vapor-liquid equilibrium data for the binary systems propane-furfural and propylene-furfural at 293.15 and 313.15 K. These systems have solubility limits. Therefore, it is convenient to discuss the simultaneous calculations of vapor-liquid and liquid-liquid equilibria. Data for the binary systems are correlated by the UNIQUAC equation (Abrams and Prausnitz, 1975) using the maximum-likelihood method (An-

Correspondence to: K. Noda, Department of Chemical Engineering, 5-1, Johoku 3chome, Hamamatsu 432, Japan.

Shizuoka University,

0378-3812/92/%05.00 0 1992 - Elsevier Science Publishers B.V. All rights reserved

206

K. Noda et al. ,l Fluid Phase Equilibria 81 (1992) 205-215

derson and Abrams, 1978). Agreement of experimental results is fairly good, including that for three phases.

and calculated

EXPERIMENTAL

Total pressures were measured by the static method; the experimental apparatus and procedure were similar to those used previously (Noda et al., 1982), and a schematic diagram of the apparatus is shown in Fig. 1. Pressure measurements were made with a Bourdon pressure gauge. The Bourdon pressure gauge was calibrated with a dead-weight gauge; measurements are reproducible to within + 1 kPa. The temperature of the water bath was determined by a mercury-in-glass thermometer and maintained within kO.02 K. In order to prevent the condensation of the vapor phase, the air-bath temperature was set higher than that of the water bath by a few degrees. Since the vapor-pressure measurements are mainly affected by the liquid-phase temperature, the effect of the vapor-phase temperature on the total pressure and the vapor-phase composition is negligibly small and within the experimental errors. The vapor-phase mole fractions were determined using a gas chromatograph. The column packing was Porapack Q and the column temperature was 180°C. The liquid-phase mole fractions of one liquid phase were calculated from the total (liquid + vapor) mass of each material and from material balances on the liquid and vapor phases, as previously reported by Noda et al. (1982). The degassing was such that the equilibrium cell containing furfural was evacuated intermittently for a few minutes by a

1. Equilibrium

cell

2. Sampler

3. Pressure

gauge

4. Magnetic

5. Magnetic

stirrer

6. Water

7. Air

pump

bath

bath

Fig. 1. Experimental

apparatus for vapor-liquid

equilibria.

K. Noda et al. 1 Fltdd Phme

Equilibria

81 (1992)

205415

207

rotary pump, Liquid compositions of one liquid phase were esti~ted within _tO.OOl mole fraction. In this work, mutual solubilit~es can be hard to measure using a gas chromatograph because of the large difference in volatility of the components. Therefore, a method of weighing both the total system and furfural was used to determine the composition. Samples were withdrawn in an apparatus similar to that of Ishii et al. ( 1966). The ~thdra~ samples were cooled by ice, and evaporated inte~ittently under its own vapor pressure and by a rotary pump. The time required for evaporation was previously determined using a similar amount of sample of similar composition, The amount of furfural evaporated may be cancelled by the above method. Commercially available reagent-grade furfura~ was used after further pu~~cation in a laboratory distillation column where only the middle half of the distillate was recovered. The boiling point of the recovered furfural is 371 K ( 13 kPa). Research-grade propane and propylene (Takachiho Chemicals) were used without further purification. The purities of propane and propylene are reported to be 99.9% and 99.7%, respectively. RESULTS AND DISCUSSION

Experimental vapor-liquid equilibrium data are presented in Tables 1 and 2 and are shown in Figs. 2 and 3. For a two-phase system at constant temperature and pressure P, the equilib~um equation for each component i is

where & is the vapor-phase fugacity coeffcient, yi is the piqued-phase activity coefficient and fl’ is the fugacity at a reference state. &, is the partial molar liquid volume. At low or moderate densities, a suitable equation of state is the virial equation truncated after the second term. The fugacity coefficient & is

The viral coefficients are calculated by the Hayden-OConnell equation (1975). When the pressure is low and mixture conditions are far from critical, coupled with the assumption that Yit = 2tn and that yiL is not compressible, the liquid fugacity is given by fi = Y~x,CPX exp i(P - P:‘)URTI where P; is the pure-component nent saturated liquid volume.

(3) vapor pressure, and vg is the pure-compo-

208

K. Noda et al. 1 Fluid Phme Equilibria 81 (1992) 205-215

TABLE 1 Vapor-liquid

equilibrium

data for the propane (1) -furfural

(2) system

Xl

&Pa)

(mole fraction)

Yl (mole fraction)

293.15

0.094 0.284 0.306 0.347 0.432 0.497 0.550 0.611 0.675 0.712 0.831 0.831

0.012 0.038 0.042 0.045 0.058 0.069 0.080 0.091 0.101 0.110 0.136 = 0.987 a

0.997 0.998 0.998 0.999 0.999 0.999 0.999 0.999 0.999 0.999 0.999 0.999

313.15

0.146 0.323 0.345 0.393 0.543 0.562 0.652 0.773 0.834 0.855 1.107 1.240 1.339 1.339

0.017 0.032 0.035 0.040 0.058 0.059 0.070 0.088 0.094 0.098 0.135 0.154 0.172 = 0.986 a

0.994 0.995 0.995 0.996 0.997 0.997 0.997 0.998 0.998 0.999 0.999 0.999 0.999 0.999

a Vapor-liquid-liquid

equilibrium.

To correlate vapor-liquid equilibrium data, it is necessary to evaluati the liquid activity coefficient. From the many expressions which have been reported, the UNIQUAC equation was chosen (Prausnitz et al., 1986). The activity coefficient is expressed in the form In yi = ln( G+/Xi) + (Z/2)qi ln(Oj/@,i) + Zi- (@i/Xi) C

Xi4

i

(4) Ii = (Z/2)(ri - qi) - (Ti - 1) Zji

=

exp

(-ajilT)

(5) (6)

K. Noah et al. 1 Fluid Phase Equilibria

209

81 (1992) 205-215

TABLE 2 Vapor-liquid

equilibrium data for the propylene (I)-furfural 3 (mole fraction)

Yl

0.190 0.214 0.281 0.348 0.515 0.575 0.641 0.680 0.778 0.893 0.916 0.967 0.967 0.973 1.004

0.020 0.041 0.045 0.063 0.078 0.123 0.146 0.168 0.185 0.228 0.301 0.327 0.392 a 0.925 a 0.941 0.985

0.998 0.999 0.999 0.999 0.999 0.999 0.999 0.999 0.999 0.999 0.999 0.999 0.999 0.999 0.999 0.999

0,119 0.231 0,257 0.338 0.425 0.689 0.866 1.027 1.213 1.254 1.396 1.441 1.532 1.532 1.551 1.611

0.018 0.035 0.038 0.052 0.067 0.117 0.158 0.194 0.253 0.272 0.343 0.375 0.479 = 0.869 a 0.930 0.98 I

0.995 0.996 0.996 0.997 0.997 0.997 0.998 0.998 0.998 0.998 0.999 0.999 0.999 0.999 0.999 0.999

&Pa)

0.100

293.15

313.15

(2) system

(mole) fraction)

where the pure-component parameters are obtained from Prausnitz et al. (1980) and the binary parameter Uii is adjustable. The computer programs used in this work are similar to those described by Prausnitz et al. (1980). For binary vapor-liq~d equilibria, the parameters sought are those that minimize the objective function s

=

2 i=

CpP -pY)2 + (E - Cl2 + 1[ 4, 4,

CxYi

-XTi)2

d,,

1

(7)

210

K. Moda et al. /Fluid Phase EquiGbria 81 (1992) X35-215

1.6

l

40.0 “C _--__+_____.q

1.4 /

~

I

I

0 l Experimental -

Calculated

Propane

mole

Fig. 2. Vapor-liquid

fraction

C-3

equilibria for the propane-furfural

system.

I

1.6

40.0 Yz _----_-_

@-.J

I

/

~

! :

1.4

4?

1.2

I

?

0

P ”

1.0

0 @. Experimental

0

0.2

0.4

Propylene

Fig. 3. Vapor-liquid

0.6

0.6

mole fraction

1.0

C- 3

equilibria for the propylene-furfural

system.

211

K. No& et al. 1 Fhtid Phase Equilibria 81 (1992) 205-215

where o* is the estimated variance of each of the measured variables and crp = 1 kPa, Q~ = 0.02 K and cr, = 0.001. The objective function defined by Prausnitz et al. (1980) includes a vapor composition term. However, the boiling point of one component (furfural) in the binary mixtures is much higher than the other (propane or propylene), so the vapor composition of the low boiling point component is almost unity. Therefore, the term for vapor composition is omitted in eqn. (7). Pure-component vapor pressures are calculated by using the Frost-Kalkwarf equation whose parameters are available or can be determined from the literature (Reid et al., 1987). Figures 2 and 3 also show the comparisons of calculated results with experimental data for the propane-furfural and propylene-furfural systems at 293.15 and 313.15 K. Table 3 lists the parameters and the root-meansquare deviations in total pressure, temperature, liquid and vapor compositions. The maximum deviation is 15 kPa ( 1.0%) for total pressure, at the liquid-liquid region. Table 4 shows liquid-liquid-vapor equilibrium data for the propylenefurfural system from 293.15 to 313.15 K. An upper’critical solution temperature (UT) does not appear in this range. Figure 4 shows measured and calculated liquid-liquid equilibria and calculated bubble-point pressures. Above 313.15 K or below 293.15 K, the solubility curve is a calculated one using liquid-liquid parameters which are TABLE 3 UNIQUAC parameters and root-mean-square propylene-furfural systems

deviations

for the propane-f&Ural

RMS a Temp. (K)

azl W

Propane (I)-furfural

293.15 313.15

313.15

0.0014 0.0011

system from all datum points 0.01 0.0011 286.9

0.01

306.1

0.0018

system from mutual solubility data 329.6 311.7 309.1 296.9

5 CT,,, -

r=l

0.00 0.00

451.2 415.9

52.8

Propylene (I)-furfural 293.15 37.8 303.15 44.5 313.15 44.2 323.15 49.6

&a)

(‘K,

system from all datum points

61.3 86.8

Propylene (I)-furfural 293.15 61.5

Yl

XI

azl WI

0.5

Te,,):/M

1

.

1.1 1.4

0.0014 0.0008

2.2 4.1

0.0006 0.0009

-

-

and

K. Noda et al. /Fluid Phase Equilibria 81 (1992) 205-215

212

TABLE 4 Liquid-liquid-vapor

equilibrium

Temp.

Pressure

WZ

( MJW

Propane (I)-furfural

data x;

X;

0.136 0.172

0.987 0.986

0.392 0.434 0.479 0.540

0.925 0.895 0.869 0.820

system

293.15 313.15

0.831 1.339

Propylene (I)-furfural

293.15 303.15 313.15 323.15

system

0.967 1.225 1.532 1.878

2.5

______________

l-l 1.5 0

_____________

% $

1.0

-------_---__-

f n

____________________--

0.5

0

0

0.2 Propylene

0.4

0.6

mole fraction

0.6

1.0

t- I

Fig. 4. Total pressures and liquid-liquid

equilibria for the propylene-furfural

system.

extrapolated smoothly from the experimental temperature range. As the UNIQUAC parameters of this system are not straight lines, their estimated values are subject to some error when extrapolated. However, the composition of the liquid-liquid equilibrium at the CST seems to be reasonable. The estimated CST is 60.4 “C and the estimated composition of propylene at the CST is x1 = 0.678. Figure 5 shows an empirical Ishida (1960) plot for liquid-liquid equilibrium data. The composition at CST from this plot is estimated to be x1 = 0.67. This value is comparable to that of the UNIQUAC equation described above.

213

K. Noda et al. /Fluid Phase Equilibria 81 (1992) 205-215

Fig. 5. (1 - x’)/x’ vs. (1 - x”)/x” plot for liquid-liquid

equilibria.

Table 3 shows the UNIQUAC parameters and root-mean-square deviations of temperature, pressure and liquid and vapor compositions. The parameters from mutual solubility data (LLE) are obtained by solving the two simultaneous equations of activity (y’x’ = y”x”). Therefore, these LLE parameters do not use the maximum-likelihood method. Table 5 shows calculated and experimental values (total pressure, liquid and vapor compositions) at the liquid-liquid-vapor equilibrium point. From Tables 3 and 5, it can be seen that the representation of all data points is not always satisfactory for the propylene-furfural system, especially with respect to the compositions and the parameters. The greater consistency of TABLE 5 Calculated (l)-furfural

and experimental values at liquid-liquid-vapor (2) and propylene (l)-furfural (2) systems

equilibria

for the propane

Temp. W

Propane (I)-furfural

293.15

0.136

313.15

0.172

system

0.134 0.173 -

0.987 0.986

Propylene (I)-furfural 293.15 0.392

system 0.366 -

0.925

303.15 313.15

0.434 0.479

0.445

0.895 0.869

323.15

0.540

-

0.820

0.983 0.980 -

0.831

0.907 0.880 -

0.967

a From LLE (mutual solubility data) parameters.

1.339

1.225 1.532 1.878

0.821 0.825 1.339 1.348

0.0003 0.0003 a 0.0008 0.0008 a

0.948 0.960 1.208 1.504 1.503 1.831

0.0003 0.0002 0.0004 0.0006 0.0006 0.0009

a a = = a

214

K. Noda et al. 1 Fluid Phase Equilibria 81 (1992) 205-215

vapor-liquid and liquid-liquid equilibria for the propylene-furfural system is further discussion. However, these discrepancies scarcely appear in Fig. 3, because the calculated total pressures are well represented. Although the correlation could still be improved, it may be concluded that the propanefurfural and propylene-furfural systems are fairly well correlated by the UNIQUAC equation. CONCLUSIONS

( 1) Vapor-liquid- liquid equilibrium data for the propane - furfural and propylene-furfural systems at 293.15 and 313.15 K are obtained using the static method. (2) Mutual solubilities of these systems are also obtained using the analytical (weighing) method. (3) Experimental vapor-liquid equilibrium data, including that for three phases, are compared with values calculated using the UNIQUAC equation. The simultaneous correlation of vapor-liquid and liquid-liquid equilibria is fairly good. The more precise representation of vapor-liquid and liquidliquid equilibria for the propylene-furfural system is further discussion. REFERENCES Abrams, D.S. and Prausnitz, J.M., 1975. Statistical thermodynamics of liquid mixtures: a new expression for the excess Gibbs energy of partly or completely miscible systems. AIChE J., 21: 116-128. Anderson, T.F. and Abrams, D.S., 1978. Evaluation of parameters for nonlinear thermodynamic models. AIChE J., 24: 20-29. Hayden, J.G. and O’Connell, J.P., 1975. A generalized method for predicting second virial coefficients. Ind. Eng. Chem., Process Des. Dev., 14: 209-216. Ishida, K., 1960. Application of the theory of regular solutions to binary phase equilibria. I. Method of application to binary liquid equilibria. Bull. Chem. Sot. Jpn., 33: 998-l@l. Ishii, K., Hayami, S., Shirai, T. and Ishida, K., 1966. Liquid equilibrium data for the system propane, propylene, and ammonia solvents. J. Chem. Eng. Data, 11: 288-293. Noda, K., Sakai, M. and Ishida, K., 1982. Isothermal vapor-liquid equilibrium data for the propane-propylene-tetralin system. J. Chem. Eng. Data, 27: 32-34. Prausnitz, J.M., Anderson, T.F., Green, E.A., Eckert, C.A., Hsieh, R. and O’Connell, J.P., 1980. Computer calculations for Multicomponent Vapor-Liquid and Liquid-Liquid Equilibria. Prentice-Hall, Englewood Cliffs, NJ, 229 pp. Prausnitz, L.M., Lichetenthaler, R.N. and de Azevedo, E.G., 1986. Molecular Thermodynamics of Fluid Phase Equilibria, 2nd edn. Prentice-Hall, Englewood Cliffs, NJ, 238 pp. Reid, C.R., Prausnitz, J.M. and Poling, B.E., 1987. The Properties of Gases and Liquids. McGraw-Hill, New York, NY, 656 pp.

APPENDIX:

LIST OF SYMBOLS

binary interaction parameter (K-l) second virial coefficient (m3 mol-‘)

K. Noda et al. 1 Chid Phase Equilibria 81 (199.2) 205-21s

third adjustable parameter in eqn. (4) (C = 1) fugacity (Pa) defined by eqn, (5) pressure (Pa) pure-component area parameter (q = q’ in this work) p~re~~rnpone~~ volmc parameter gas constant (3 mol-’ K-r) objective function defined by eqn, (7) absolute temperature (K) liquid molar volume (m3/mol) partial molar volume of liquid (m~~rnu~) liquid-ph~e mole fraction vapor-phase mole fraction coordination number compressibility factor

Y

0, 6’ d ‘t :

activity coefficient area fraction (0 = 6’ in this work) standard deviation binary interaction parameter fugacity ~e~cient segment fraction

Subscripts i,j

L P T

X Y

component liquid phase pressure temperature liquid composition vapor composition

~~~~~~~~~ 0 ;L s

I SF t

true experimental reference state saturated nxxtud s~~ubiIity

215