High-Pressure Vapor-Liquid and Vapor-Liquid-Liquid Equilibria in the Carbon Dioxide + 1-Nonanol System
Catinca Secuianu, Viorel Feroiu, Dan Geană
Dept. of Applied Physical Chemistry and Electrochemistry
Introduction
Thermodynamic knowledge of the high-pressure phase behavior of carbon dioxide + alcohol mixtures is essential for the design and
implementation of many chemical and biotechnological processes. In this work the fluid phase behavior of the binary system carbon dioxide
+ 1-nonanol has been measured. The experimental data were modelled with the SRK-EOS coupled with the Huron-Vidal infinite dilution
(HVID) mixing rules and with the MHV2-UNIFAC ‘87.
Experimental work
Phase behavior measurements were made in a high-pressure visual cell with variable volume based on the static-analytical method. A detailed
description of the apparatus and experimental procedure was presented in an earlier paper [1].
Vapor-liquid and vapor-liquid-liquid equilibria data for the carbon dioxide + 1-nonanol system at 303.15, 308.15, 313.15, 333.15 and 353.15
K up to 103.3 bar were determined. The three-phase equilibrium data and the upper critical endpoint were measured.
Modelling
The Soave-Redlich-Kwong (SRK) equation of state coupled with the Huron-Vidal infinite dilution (HVID) mixing rules [2] was used to
predict the complex phase behavior (Critical curve, LLV line, isothermal VLE, and VLLE). The SRK-MHV2-UNIFAC ’87 model was
applied to predict the VLE at constant temperatures.
Results
The experimental fluid phase behavior of the carbon dioxide + 1Some experimental results are presented in the table and the figures
nonanol shows that the system presents a type III phase diagram.
below. The calculated curves are also included.
VLE data at temperatures between 303.15 and 313.15 K were
Table 1. Experimental and calculated temperatures-compositions
correlated with SRK/HVID and a linear dependence of the HVID
of the three-phase curve
parameters with the inverse temperature was obtained. The values
T /K
T /K
P /bar
X
X
X
X
X
of HVID parameters from the linear correlation were used to
285.65
286.85
47.0
0.5944
0.9874
0.6784
0.9455
0.99998
predict VLE, VLLE, critical curve, and LLV line. The topology
290.95
292.25
53.5
0.6073
0.9884
0.6702
0.9533
0.99996
292.55
293.85
55.6
0.6111
0.9887
0.6675
0.9557
0.99994
of phase behavior is reliable predicted. Constant values of the
297.25
298.55
62.0
0.6241
0.9898
0.6589
0.9637
0.99988
parameters with the temperature were also tested. The predictions
300.15
301.25
66.0
0.6343
0.9906
0.6536
0.9687
0.99980
of VLE with SRK-MHV2-UNIFAC show a significant
303.15
304.35
70.8
0.6447
0.9916
0.6470
0.9749
0.99962
307.85
307.75
76.5
0.6545
0.9931
0.6395
0.9823
0.99911
disagreement with the experimental data.
exp
calc
exp
L1 (exp)
L2(exp)
L1 (calc)
L2(calc)
V(calc)
120
250
T = 303.15 K
T = 308.15 K
T = 313.15 K
T = 333.15 K
T = 353.15 K
T = 303.15 K
100
T = 308.15 K
T = 313.15 K
T = 333.15 K
T = 353.15 K
SRK/HVID
T = 308.15 K
T = 313.15 K
200
T = 333.15 K
80
T = 353.15 K
100
80
P/bar
60
P/bar
P/bar
150
100
40
40
20
50
20
60
0
0
0
0
0
0.2
0.4
0.6
0.8
1
0
0.2
Mole fraction of CO2
0.4
0.6
0.8
Experimental results and correlations
with SRK/HVID EOS
Pc CO2
Pc 1-Nonanol
UCEP, this work
LLV Curve, this work
SLLV, Lam et al. (1990)
Critical curve, Scheidgen (1997)
Ps CO2
Ps 1-Nonanol
SRK/HVID (u12, u21 = ct)
SRK/HVID (u12, u21 = var)
0.8
1
350
80
VLE, this work
Experimental LLV line
Experimental LL
Pfohl et al. (1999)
Poehler et al. (1996)
SRK/HVID (u12, u21= var)
SRK/HVID LLV line
SRK/HVID (u12, u21 = ct)
SRK/HVID LLV line
300
UCEP
Experimental LLV
SRK/HVID LLV
250
70
200
P/bar
P/bar
60
P/bar
0.6
Experimental results and predictions
with SRK/MHV2-UNIFAC EOS
90
1200
800
0.4
Mole fraction of CO2
Mole fraction of CO2
Pressure-composition data for carbon
dioxide (1) + 1-nonanol (2)
1000
0.2
1
600
150
50
400
100
40
50
200
30
0
0
200
300
400
500
600
700
20
260
0
270
280
T/K
P-T fluid phase diagram of carbon
dioxide (1) + 1-nonanol (2)
290
300
310
320
0.2
0.4
0.6
0.8
1
Mole fraction of CO2
T/K
P-T projection of the three
Pressure-composition data for carbon
dioxide + 1-nonanol at 303.15 K
phase curve
Conclusions
A visual high-pressure variable volume static-analytic apparatus was used to obtain VLE and VLLE data. As also confirmed by the
measurements of Scheidgen, the phase behavior of the mixture of carbon dioxide + 1-nonanol can be attributed to type III. The SRK/HVID
model is successful in modeling qualitatively the complicated topology of the phase behavior of the system under study. The presented
system in this work is a part of an extended study about binary mixtures containing carbon dioxide + alcohols [1, 4-5].
References
[1] Secuianu, C., Feroiu, V., Geană, D., J. Chem. Eng. Data 48 (2003) 1384
[2] Feroiu, V., Geană, D., Fluid Phase Equilib., 120 (1996) 1
[3] Scheidgen, A., Ph. D. Thesis, Ruhr University, Bochum (1997)
[4] Secuianu, C., Feroiu,V., Geană, D., J. Chem. Eng. Data 49 (2004) 1635
[5] Secuianu, C., Ph. D. Thesis, Politehnica University, Bucharest (2004)