High pressure phase equilibria of
1-chloropropane + carbon dioxide system
Miroslaw Chorazewskia,b*, Alexandr Babiča, Ivan Wichterlea, Karel Aima
a
E. Hála Laboratory of Thermodynamics, Institute of Chemical Process Fundamentals, Academy of
Sciences of the Czech Republic,Rozvojová 2, 165 02 Prague 6-Suchdol, Czech Republic
b
Institute of Chemistry, University of Silesia, Szkolna Street 9, 40-006 Katowice, Poland
Abstract
High-pressure VLE of carbon dioxide with 1-chloropropane system was measured at temperatures
303, 313, 328 K within pressure range 1 -- 10 MPa. P-T-x-y data are experimentally measured by
means of static-analytic apparatus with visual cell and sampling of vapour and liquid phases. VLE
are modeled by three parameter cubic Patel-Teja EOS and PC-SAFT EOS, both EOS are used with
one-fluid van der Waals mixing rules. PC-SAFT parameters for pure 1-chloropropane are
computed either from saturated pressure and liquid density or interpolated from literature
parameters for 1-chloroalkanes.
Introduction
Knowledge of phase equilibrium data mixtures containing supercritical fluids like carbon dioxide is
required for practical use such as in chemical separation process, related industrial application.
Carbon dioxide is a excellent solvent for supercritical fluid extraction. Due to its nontoxicity and
low critical temperature it can be used for extracting natural and industrial substances.
Chloroalkanes are polar non-associating fluids, in which important electrostatic intermolecular
interactions occur due to non-zero permanent dipole moments and/or quadrupole moments. In
addition, the knowledge of the thermophysical properties of liquid halogenoalkanes is of high
interest on account of their wide usage in science and industrial processes. Those properties are
crucial for the designing of chemical processes as well as for the progress of thermodynamic
theories. Unfortunately, basic properties of halogenoalkanes and their mixtures are rather scarce in
the literature. To the best of our knowledge, for the mixtures studied in this paper no experimental
data corresponding to vapour-liquid equilibria are available in the accessible literature. Only few
data about the vapour-liquid equilibrium of halogenoalknes with carbon dioxide are available in
open literature [1-11]; no such data are available for 1-chloropropane. Thus, this prompted us to
generate original data using high-pressure static-analytic apparatus. The experimental equilibrium
data were correlated with three parameter cubic Patel-Teja equation of state [12] and PC-SAFT
equation of state [13], [14] which belongs to group of SAFT (statistical association fluid theory)
equations of state [16], [17] based on Wertheim association theory.
Experimental Section
Chemicals
Carbon dioxide 99.995% (Linde) was used without further purification. 1-Chloropropane (Aldrich,
>98%) was purified [21] by fractional distillation. Prior to the measurements, 1-chloropropane was
dried with molecular sieves (type 3A).
Purity of 1-chloropropane was measured by gas chromatography and purity is 99.9%. Also the
refraction index of 1-chloropropane and density was determined. Experimental and literature
density and refraction index are reported in table 1.
Table 1.: Density and refraction index of 1-chloropropane at 25 oC and 1.01325 bar:
density [g/ml]
nD
literature [TRC NIST]
0.8830
1.3851
experimental
0.88381
1.38526
Apparatus and Procedure
The phase equilibrium apparatus of this study is reported in Figure 1. Static-analytic apparatus with
high-pressure visual cell and vapour/liquid phase sampling is used for experimental determination
of vapour-liquid phase equilibria in temperature range 20 - 95 oC and pressures up to 10 MPa.
Stainless steel cell has volume 65 cm3. Cell is equipped with magnetic stirrer, two quartz windows
for observing of cell content. Cell is immersed in 60 L water bath. Pressure is determined by
pressure transducer Heise HPO 1855 with accuracy 0.05 % of full range. Pressure gauge was
calibrated against dead weight Ruska. Temperature by ΑΣΛ F250 with accuracy better than 0.02 K
on ITS-90. Resistance thermometer was calibrated against Pt-thermometer. Composition of
vapour/liquid phase is determined by gas chromatograph Hewlett-Packard 5890.
Copper micro-capillaries with internal diameter approx. 0.1 mm are used for sampling of
equilibrium phases. Micro-capillary for sampling liquid phase is connected to the bottom of
equilibrium cell, micro-capillary for sampling vapour phase is connected to the top of equilibrium
cell. Capillary diameter is chosen according to mixture viscosity, so the sample can be withdrawn
continuously. No sampling valves are used because sampling micro-capillaries are opened/closed
manually at the tip before/after sample withdrawal.
Analysis of equilibrium phases is done in Hewlett-Packard gas chromatograph with packed column
with Porapak Q and TCD detector. Estimated uncertainity of determination of liquid phase
composition is 0.001 in molar fraction. For gas phase is estimated uncertainity 0.002 in molar
fraction. Temperature of owen, detector and injector was set to 160 oC.
Evacuated equlibrium cell is filled with liquid 1-chloropropane and degassed by evacuation. After
degassing carbon dioxide is added to cell by pressure pump Ruska. Temperature of water bath is set
to desired temperature and mixture in the cell is stirred. Equilibrium is attained after few hours;
mixer is stoped and after some time the pressure and temperature is read. Liquid micro-capillary is
opened and placed into homogenizer through septum. Sample evaporates in homogenizator into
flow of hot carrier gas (helium) and flows to gas chromatograph for analysis. Several samples are
taken and analysed, then the micro-capillary is removed from homogenizator and closed. Vapour
phase is sampled and analysed by the same procedure.
Figure 1.: Static-analytic apparatus
(1) high pressure visual cell, (2) water bath, (3) resistance thermometer, (4) pressure transducer, (5)
electric heating, (6) water cooling, (7) water bath mixer with motor, (8) liquid phase sampling
microcapillary, (9) vapour phase sampling microcapillary, (10) glass flask for alcohol, (11) CO2
cylinder, (12) pressure pump Ruska, (13) vacuum pump, (14) sample homogenizer, (15) gas
chromatograph
Phase equilibria modelling
Carbon dioxide + 1-chloropropane VLE are corelated with two EOS based models.
First model is Patel-Teja EOS [12] and second model is PC-SAFT EOS [13].
Both models are used with one-fluid van der Waals mixing rules.
Patel-Teja equation of state is three-parameter cubic equation of state:
\begin{equation}
P = \frac{RT}{v-b} - \frac{a}{v(v+b) + c(v-b)} \hspace{1cm},
\end{equation}
where parameter a is function of temperature and parameters b, c are constants.
Further description of equation of state can be found in original Patel and Teja article [12].
PC-SAFT equation of state is molecular based equation of state and belongs to SAFT (statistical
association fluid theory) family. SAFT equations are presented as residual Helmholtz energy which
is sum of several terms:
\begin{equation}
A^{res} = A^{hs} + A^{chain} + A^{disp} + A^{assoc}
\end{equation}
Term Ahs refers to single building block (hard spheres). Molecules can be build by chaining Achain
of hard spheres and perturbation contribution Adisp is added to hard spheres for dispersion
interactions.
Chain molecules can also interact by associations Aassoc. Association term is applied in modelling of
molecules which interact by hydroxy bridge (alcohols, acids).
Results and discussion
Experimental data of binary system carbon dioxide + 1-chloropropane were measured at three
isotherms (30, 40, 55 oC).
One binary interaction parameter k12 was obtained for each isotherm and EOS. It is necessary to
know parameters of pure compounds for computation of mixture phase equilibria. Critical
parameters and accentric factor of pure compounds are used with cubic Patel-Teja EOS. Critical
parameters and accentric factor of 1-chloropropane and carbon dioxide are reported in table 2. and
were taken from NIST databases [18],[19] and literature [20].
Parameters of carbon dioxide for PC-SAFT EOS are taken from article [gross] and are used without
change. Parameters of 1-chloropropane for PC-SAFT EOS are not available in literature, therefore
two methods were used for their calculating. First set of 1-chloropropane parameters are obtained
by linear interpolation of 1-chloroethane and 1-chlorobutane parameters from literature [gross].
Second set of parameters are computed by corelation of saturated pressures within temperature
range 260 - 500 K, experimental values are represented by empirical equation derived from Antoine
equation [20].
Binary interaction parameters are reported in table 4. Binary interaction parameters k12 were
computed by minimizing objective function (1) which is sum of square roots of pressure
residualsand vapour phase composition residuals. Objective function was minimized by means of
Nelder-Mead simplex method [15].
\begin{equation}
OF
=
\frac{1}{N}
\sum_i^N
P^{\mathrm{exp}}_i)^2}{P^{\mathrm{exp}}_i}
y^{\mathrm{exp}}_i)^2
\end{equation}
+
\frac{(P^{\mathrm{comp}}_i
(y^{\mathrm{comp}}_i
-
PC-SAFT EOS parameters are reported in table 3. Standard deviation of saturated pressure
computed from corelated parameters is 0.004437 MPa. Standard deviation of saturated pressure
computed from interpolated parameters is 0.045504 MPa. Coordinates of 1-chloropropane critical
point computed from interpolated set of parameters are following: Pc = 5.1285 MPa, Tc = 512.8496
K, Zc = 0.3105161.
Coordinates of 1-chloropropane critical point computed from corelated set of parameters are Pc =
5.0222 MPa, Tc = 510.3940 K, Zc = 0.3102203, these values can be compared with experimental
data from table 2. Comparison of experimental and computed P-T curves for 1-chloropropane are
reported in picture 2. Both sets parameters are very similar, but corelated set better describes
saturated pressure of pure compound, therefore corelated set is used for further computations of
VLE.
Binary interaction parameter k12 is used only in mixing rule for parameter $a$ of Patel-Teja EOS.
Binary interaction parameter k12 is used only in mixing rule for dispersion term of PC-SAFT EOS,
other terms are without interaction parameter.
From table 4. of computed k12 can be seen that they differ slightly from zero, interaction parameters
are lesser than zero for Patel-Teja EOS and higher than zero for PC-SAFT EOS. Comparison of
phase diagrams at 40 oC computed with tabelated k12 and k12 = 0 is presented in picture 5.
Standard deviations of computed pressure and vapour phase composition are computed from
residuals of each experimental point and are tabelated together with experimental data and residuals
in table 5. Standard deviations of pressure computed by PC-SAFT EOS have lesser values than
standard deviations computed by Patel-Teja EOS. Standard deviations of vapor phase composition
computed by PC-SAFT EOS don't differ substantially from standard deviations computed by PatelTeja EOS.
Table 2.: Critical parameters and accentric factor of pure compounds
Tc [K]
Pc [MPa]
Zc
omega
CO2
304.190
7.382
0.26823
0.228
1-chloropropane
503.200
4.578
0.27816
0.235
Table 3.: Parameters of pure compound for PC-SAFT EOS:
component
m
sigma [A]
epsilon/k [K]
carbon dioxide
2.0729
2.7852
169.2100
1-chloropropane:
interpolated set
2.5602
3.5534
251.4530
1-chloropropane:
corelated set
2.5633
3.5783
251.6507
Table 4.: Binary interaction parameters for Patel-Teja and PC-SAFT EOS:
t [oC]
k12 Patel-Teja EOS
k12 PC-SAFT EOS
30.0
-0.038459
0.022598
40.0
-0.039347
0.023987
55.0
-0.080368
0.003992
Table 5.: Experimental and computed data of VLE 1-chloropropane + carbon dioxide
tabulka t =30 oC
experimental data
Patel-Teja EOS
PC-SAFT EOS
x1
y1
P [MPa]
Pcomp-Pexp
[MPa]
delta y1
delta
[MPa]
0.123100
0.918400
0.521385
0.039070
-0.016060
0.033208
-0.018991
0.168800
0.941500
0.814664
-0.052307
-0.013305
-0.053290
-0.016260
0.218100
0.963100
1.002040
-0.012229
-0.018381
-0.014704
-0.019757
0.307900
0.972000
1.515270
-0.082361
-0.010093
-0.072687
-0.010954
0.424300
0.988700
2.059060
0.013149
-0.014841
0.019567
-0.014339
0.497200
0.989500
2.517310
-0.000169
-0.010838
0.012961
-0.010183
0.519500
0.989500
2.674130
-0.013061
-0.009616
0.003748
-0.008966
0.565900
0.990300
2.914460
0.058910
-0.008150
0.060784
-0.007141
0.602400
0.986100
3.197560
0.034462
-0.002383
0.040950
-0.001433
0.644400
0.988700
3.448070
0.096789
-0.003366
0.083178
-0.002193
0.690100
0.990300
3.867620
0.037410
-0.003386
0.034249
-0.002403
0.713200
0.994600
4.107940
-0.012578
-0.006945
-0.003621
-0.006116
0.765300
0.992000
4.545820
0.000274
-0.002782
-0.006207
-0.001929
0.818400
0.996200
5.036660
0.000761
-0.005488
-0.021710
-0.004667
0.844000
0.996200
5.266800
0.019502
-0.004781
-0.020162
-0.003929
0.887900
0.994600
5.663950
0.068698
-0.001934
-0.011978
-0.000988
0.913500
0.992800
5.936860
0.069379
0.000659
-0.022282
0.001600
0.957200
0.994600
6.386970
0.124096
0.000563
-0.014849
0.001640
0.974600
0.993600
6.647660
0.093413
0.002588
-0.031746
0.003607
0.982800
0.995400
6.804480
0.058872
0.001463
-0.045357
0.002392
0.994600
0.999500
7.065170
0.010510
-0.001066
-0.062226
-0.000469
standard deviation:
0.055523
0.008517
0.039156
0.008977
tabulka t =40 oC
experimental data
Patel-Teja EOS
PC-SAFT EOS
Delta
[MPa]
x1
y1
P [MPa]
Delta
[MPa]
P$ Delta y1
0.243900
0.948300
1.365440
-0.029670
-0.009448
P delta y1
P$ Delta y1
-0.027551
-0.010492
experimental data
Patel-Teja EOS
PC-SAFT EOS
0.302800
0.958800
1.752510
-0.067260
-0.007645
-0.056454
-0.008286
0.380100
0.970100
2.163320
0.014669
-0.008285
0.020242
-0.007623
0.503400
0.978700
3.089450
-0.030600
-0.006344
-0.008036
-0.005429
0.613500
0.984800
3.804220
0.162071
-0.006441
0.129759
-0.004407
0.651700
0.986800
4.260160
0.052563
-0.006806
0.047304
-0.005214
0.666500
0.993000
4.424010
0.027745
-0.012419
0.028296
-0.010921
0.684800
0.988700
4.611610
0.015921
-0.007428
0.017415
-0.005965
0.704700
0.988700
4.811080
0.012579
-0.006714
0.011402
-0.005251
0.748000
0.992200
5.150660
0.118399
-0.008785
0.063613
-0.006879
0.752400
0.991200
5.245650
0.070141
-0.007649
0.033392
-0.005928
0.774200
0.987900
5.549600
0.001841
-0.003695
-0.013079
-0.002229
0.812400
0.991100
5.912930
0.068297
-0.005833
0.009107
-0.004071
0.839300
0.987900
6.112400
0.184702
-0.001943
0.054889
0.000311
0.862700
0.992200
6.383110
0.197938
-0.005680
0.047285
-0.003299
0.883400
0.989500
6.639580
0.200072
-0.002513
0.035917
-0.000015
0.914900
0.993000
7.107390
0.140533
-0.005369
-0.003184
-0.002815
0.929500
0.991100
7.342480
0.101786
-0.003215
-0.020597
-0.000603
0.937300
0.991100
7.461210
0.090208
-0.003101
-0.025129
-0.000382
0.945100
0.987900
7.601320
0.059059
0.000188
-0.034017 0.002921
0.955500
0.986800
7.693930
0.114853
0.001332
-0.017318 0.004816
0.104340
0.006456
standard deviation:
0.043209
0.005566
Tabulka t=55 oC
experimental data
Patel-Teja EOS
PC-SAFT EOS
Delta
[MPa]
x1
y1
P [MPa]
Delta
[MPa]
P$ Delta y1
P$ Delta y1
0.1203
0.8677
0.821719
-0.076011
-0.046104
-0.072875
-0.053015
0.1962
0.9174
1.238300
-0.056063
-0.030951
-0.052237
-0.033663
0.3087
0.9495
1.927260
-0.012359
-0.020693
-0.005443
-0.020318
0.3749
0.9613
2.423960
-0.020131
-0.018646
-0.005566
-0.017626
0.4518
0.9762
2.989320
0.047833
-0.022317
0.056449
-0.020158
0.5205
0.9788
3.611900
0.061170
-0.017639
0.069574
-0.015114
0.6123
0.9810
4.481690
0.165288
-0.012772
0.137450
-0.009386
experimental data
Patel-Teja EOS
PC-SAFT EOS
0.6874
0.9885
5.225580
0.343361
-0.016166
0.228004
-0.011710
0.7297
0.9877
5.733720
0.410737
-0.013635
0.242061
-0.008752
0.7841
0.9851
6.422690
0.524943
-0.009477
0.255937
-0.003765
0.8289
0.9844
6.976600
0.683915
-0.008231
0.276279
-0.001216
0.8685
0.9892
7.541960
0.779032
-0.013474
0.251424
-0.004924
0.9197
0.9869
8.242370
0.928505
-0.015042
0.189546
-0.001875
0.9546
0.9836
8.819180
0.204687
-0.014339
0.029823
-0.005021
0.429588
0.020788
0.166361
0.020129
standard deviation:
Figure 2.: P-T diagram for pure 1-chloropropane:
Figure 3.:
Experimen
tal data of
CO2+chlo
ropropane
at
all
isotherms
Figure
4.:
CO2+chloropropan
e at 30 oC
Figure 5.: CO2+chloropropane at 40 oC
Figure 6.: CO2+chloropropane at 55 oC
Conclusion
New experimental data of vapour-liquid equilibrium for carbon dioxide + 1-chloropropane at high
pressures were measured. No data for this systems are published at high pressures. P-x-y data were
obtained at three isotherms (30 oC, 40 oC, 55 oC) within pressure range 1-10 MPa. Experimental
data were correlated with two models: Patel-Teja equation of state and PC-SAFT equation of state
with one-fluid van der Waals mixing rules. Carbon dioxide + 1-chloropropane system is treated as
mixture of non-associating compounds. Parameters for PC-SAFT EOS of pure 1-chloropropane
were calculated by correlation of saturated pressure. Binary interaction parameter k12 for both
models are published for each isotherm. Deviations of calculated data from experimental data for
every experimental point and standard deviations for whole sets are published in table 5.
Acknowledgements
This work was supported by the Grant Agency of the Academy of Sciences of the Czech Republic
(Grant. No. A4072301) and by EU FP5 Project No. NAS2 72074-BEMUSAC (Behaviour of
Multiphase System Under Super-Ambient Conditions).
Literature cited
[1] Blanco S. T., Embid, J.M. Otin S.: Excess enthalpies of dibromoalkane + tetrachloromethane
mixtures. Measurement and analysis in terms of group contributions (DISQUAC). Fluid Phase
Equil. 1993, 91, 281-290.
[2] Kehiaian H. V., Marongiu B. A: Comparative Study of Thermodynamic Properties and
Molecular Interactions in Mono- and Polychloroalkane + n-Alkane or +Cyclohexane Mixtures.
Fluid Phase Equil. 1988, 40, 23-78.
[3] Kehiaian H. V., Marongiu B.: Thermodynamics of 1-chloroalkanes or α,ω -dichloroalkanes +
tetrachloromethane mixtures. Fluid Phase Equil. 1988, 42, 141-163.
[4] Artal M., Muñoz E. J., Otín S., Velasco I., Kehiaian H. V.: Excess enthalpies of binary mixtures
containing α,ω-dibromoalkanes. Measurement and analysis in terms of group contributions
(disquac). Fluid Phase Equil. 1991, 70, 267-274.
[5] Blanco S. T., Muñoz E. J., Otin S.: Excess enthalpies of dibromoalkane + tetrachloromethane
mixtures. Measurement and analysis in terms of group contributions (DISQUAC). Fluid Phase
Equil. 1993, 91, 281-290.
[6] Artal M., Muñoz E. J., Otín S., Velasco I.: Excess enthalpies of (a bromochloroalkane + nalkane or cyclohexane) at the temperature 298.15 K. J. Chem. Thermodyn. 1995, 27, 191–196.
[7] Blanco S., Artal M., Fernandez J., Muñoz E. J., Otin S.: Excess enthalpies of dibromoalkane +
benzene binary mixtures at 298.15 K. J. Chem. Eng. Data, 1993, 38(4), 587-588.
[8] Gonzalez V., Tufeu R., Subra P.: High-Pressure Vapor-Liquid Equilibrium for the Binary
Systems Carbon Dioxide + Dimethyl Sulfoxide and Carbon Dioxide + Dichloromethane, J. Chem.
Eng. Data 2002, 47, 492-495.
[9] Reaves J. T., Griffith A. T., Roberts C. B.: Critical Properties of Dilute Carbon Dioxide +
Entrainer and Ethane + Entrainer Mixtures. J. Chem. Eng. Data 1998, 43, 683-686.
[10] Vonderheiden F. H., Eldridgt J. W.: The System Carbon Dioxide-Methylene Chloride
Solubility, Vapor Pressure, liquid Density, and Activity Coefficients. J. Chem. Eng. Data 1963, 8,
20-21.
[11] Sengupta S, Gupta S., Dooley K. M., Knopf F. C.: Measurement and Modeling of Extraction
of Chlorinated Hydrocarbons from Water with Supercritical Carbon Dioxide. The Journal of
Supercritical Fluids, 1994, 7, 201-209.
[12] N. C. Patel, A. S. Teja: A new cubic equation of state for fluids and fluid mixtures, Chem. Eng.
Sci. 37 (1982) 463-473
[13] Gross J., Sadowski G.: Perturbed-chain SAFT: An EOS based on a perturbation theory for
chain molecules. Ind. Eng. Chem. Res. 40 (2001) 1244--1260
[14] Gross J., Sadowski G.: Petrurbed-chain SAFT: an equation of state based on a perturbation
theory for chain molecules. Ind. Eng. Chem. Res. 40 (2001) 1244--1260
[15] Nelder J. A., Mead R.: A Simplex Method for Function Minimization. Comput. J. 7 (1965)
308--313
[16] Chapman W. G., Gubbins K. E., Jackson G., Radosz M.: New reference equation of state for
associating liquids. Ind. Eng. Chem. Res. 29 (1990) 1709--1721
[17] Chapman, W. G., Gubbins, K. E., Jackson, G., Radosz, M. SAFT: equation of state solution
model for associating fluids. Fluid Phase Equil.1989, 52, 31–38.
[18] TRC NIST tables
[19] http://webbook.nist.gov
[20] Yaws C. L.: Chemical properties handbook, McGraw-Hill Handbooks 1999, ISBN 0-07073401-1
[21] Perrin D. D., Armarego W. L. F.: Purification of laboratory chemicals, 3rd edition, Pergamon
Press 1988, ISBN 0-08-034714-2