High-Pressure Vapor-Liquid and Vapor-Liquid-Liquid Equilibria in the Carbon Dioxide 1-Nonanol System

1
High-Pressure Vapor-Liquid and Vapor-Liquid-Liquid
Equilibria in the Carbon Dioxide 1-Nonanol
System
Catinca Secuianu, Viorel Feroiu, Dan Geana
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 1-nonanol shows that the system
presents a type III phase diagram. VLE data at
temperatures between 303.15 and 313.15 K were
correlated with SRK/HVID and a linear dependence
of the HVID parameters with the inverse
temperature was obtained. The values of HVID
parameters from the linear correlation were used
to predict VLE, VLLE, critical curve, and LLV
line. The topology of phase behavior is reliable
predicted. Constant values of the parameters with
the temperature were also tested. The predictions
of VLE with SRK-MHV2-UNIFAC show a significant
disagreement with the experimental data.
Some experimental results are presented in the
table and the figures below. The calculated
curves are also included.
Table 1. Experimental and calculated
temperatures-compositions of the
three-phase curve
Experimental results and predictions with
SRK/MHV2-UNIFAC EOS
Pressure-composition data for carbon dioxide (1)
1-nonanol (2)
Experimental results and correlations with
SRK/HVID EOS
Pressure-composition data for carbon dioxide
1-nonanol at 303.15 K
P-T fluid phase diagram of carbon dioxide (1)
1-nonanol (2)
P-T projection of the three 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.