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Fluid Phase Equilibria 264 (2008) 259263
Measurement and correlation of vaporliquid equilibriafor the system carbon dioxidediisopropyl ether
Caifeng Zhu, Xianghong Wu, Danxing Zheng , Wei He, Shuhong Jing
College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China
Received 30 May 2007; received in revised form 14 November 2007; accepted 15 November 2007
Available online 22 November 2007
Abstract
A view cell with on-line sampling of the vapor and the liquid phase has been built for measuring vaporliquid equilibria data under highpressure. The samples are analyzed by gas chromatography. VLE data for the system carbon dioxidediisopropyl ether has been measured at
265.15333.15 K and 0.52.5 MPa. The isothermal data were correlated using the PengRobinson equation. The correlated results agree well with
the experimental results. The experiments confirm that diisopropyl ether is an excellent absorbent of carbon dioxide.
2007 Elsevier B.V. All rights reserved.
Keywords: Vaporliquid equilibria; Carbon dioxide absorbent; Diisopropyl ether; Thermodynamic correlation
1. Introduction
The emission of carbon dioxide (CO2) has been identified as
the main contributor to global warming and climate change. The
challenge for modern industry is to find cost-effective solutionsthat will reduce the release of CO2 into the atmosphere. Reduc-
tion of CO2 emissions can be achieved by a variety of means
[1]. A physical absorption process is one of the most important
possibilities. The advantage of this method is that it requires
relatively little energy. Diisopropyl ether, an excellent solvent,
is expected to absorb CO2 [2,3]. So the vaporliquid equi-
librium (VLE) data of the system carbon dioxidediisopropyl
ether is very important for understanding this absorption
process.
Earlier studies on the solubility and the VLE of the car-
bon dioxidediisopropyl ether system are only made Zhang et
al. [2] at experimental temperatures of 299.15 K, 308.65 K and
318.15 K, and pressure ranging from 0.82 MPa to 8.32 MPa. Thedetermination of the solubility of carbon dioxide in diisopropyl
ether is the first step in the design of a diisopropyl ether-based
carbon dioxide absorption process and was considered as the
main objective of this paper. The VLE behavior of the carbon
dioxidediisopropyl ether binary system was studied by a set
Corresponding author.
E-mail address: [email protected](D. Zheng).
of VLE device [4,5] which was established on a serial VLE
experimental methods [611] for references.
2. Experimental
2.1. Chemicals
Carbon dioxide with purity greater than 99.9 mass% was pur-
chased from Zhaoge Gas Co. Diisopropyl ether was purchased
from Tianjin Jinke Fine Chemical Co.; the purity was greater
than 99 mass%. These chemicals were used without further
purification.
2.2. Apparatus
The phase equilibrium apparatus used in this study is shown
in Fig. 1. It is a static type apparatus and its design was similar
to that used by Baba et al. [12]. There are three main sections:
one for the high-pressure equilibrium cell, another for the input
of the sample and the last one for on-line gas chromatography
(GC) analysis of the composition of the equilibrium phases.
The stainless steel equilibrium cell has an internal volume of
120 mL. The maximum operation pressure is 6 MPa. In the side
of the equilibrium cell is a glass window for visual observation
of the phase behavior.
The equilibrium cell is shown in Fig. 2. It was fixed inside a
thermostat bath filled with water. An electric heater, connected
0378-3812/$ see front matter 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.fluid.2007.11.010
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260 C. Zhu et al. / Fluid Phase Equilibria 264 (2008) 259263
Fig. 1. Schematic diagram of the experiment apparatus: (1) gas cylinder; (2) gas storage tank; (3) liquid injector; (4) stirrer; (5) constant temperature water bath; (6)
equilibrium cell; (7) magnetic mixer; (8) cooling unit; (9) temperature controller; (10) cushion tank; (11) gas chromatography; (12) vacuum pump; (13) computer.
to a PID thermal regulator (Model WD-D90) that was supplied
by Wideplus Precision Instruments Co., was immersed in
water. The temperature stability of the bath was
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262 C. Zhu et al. / Fluid Phase Equilibria 264 (2008) 259263
Fig. 4. VLE for the system carbon dioxide + diisopropyl ether: mole function
CO2 in the vapor phase at five temperatures: () 265.15 K; () 273.15 K; ()
293.15 K; () 313.15 K; () 333.15 K. -: PR correlation.
study agrees well with the calculated data and the reliability ofthe apparatus is confirmed.
The results in Fig. 3 demonstrate that the liquid mole fraction
of carbon dioxide in diisopropyl ether increases with increasing
pressure but decreases with increasingtemperature. In the exper-
imental temperature range, the liquid mole fraction of carbon
dioxide changes strongly, especially at low temperatures. For
example, the liquid mole fraction of carbon dioxide is 0.7589 at
a temperature of 265.15 K and pressure of 2.478 MPa. This con-
firms that diisopropyl ether is an excellent absorbent for carbon
dioxide.
In the PR equation, the interaction parameter kij can be
obtained from experimental data. This parameter could be used
to predict theequilibriumdata of thecarbon dioxidediisopropylether system. The calculated results from the experimental data
show in Table 3.
The deviations of the calculated results by PR equation from
the experimental data were shown in Fig. 5. It can be seen that
Fig. 5. VLE for the system carbon dioxide + diisopropyl ether: vapor phase
composition deviations of the experimental data from the calculated results at
five temperatures: () 265.15K; () 273.15K; () 293.15K; () 313.15 K;
() 333.15 K.
Table 3
Parameters of the PR equation for the carbon dioxidediisopropyl ether system
T(K) kij
265.15 0.06197
273.15 0.04081
293.15 0.08942
313.15 0.03274
333.15 0.02353
the calculation data agree well with the experimental results. So
the PR equation is able describe the VLE data of the system
carbon dioxide + diisopropyl.
4. Conclusion
The VLE data are presented for the system carbon diox-
ide + diisopropyl ether at temperatures of 265.15 K, 273.15 K,
293.15 K, 313.15 K and 333.15 K and pressures of 0.5 MPa,1.0 MPa, 1.5 MPa, 2.0 MPa and 2.5 MPa.
The VLE data were correlated with the PR equation of state.
The measured data in the study agrees well with the calcu-
lated data and the reliability of the apparatus in the study was
confirmed.
It was proven that diisopropyl ether is an excellent absorbent
of carbon dioxide. Therefore, diisopropyl ether, which has con-
siderable potential as a new carbon dioxide absorbent, is worthy
of further research.
List of symbols
a energy parameter of the PR equation (Pa m6 kmol2)b co-volume parameter of the PR equation (m3 kmol1)
k binary interaction parameter of the PR equation
p pressure (MPa)
R gas constant (8314.5 m3 Pa kmol1 K1)
T temperature (K)
V molar volume (m3 kmol1)
x liquid phase molar fraction
y vapor phase molar fraction
Greece letters
parameter of the PR equation
difference operator acentric factor
Subscripts
c critical property
i, j component i or j
m molar property
r reduced property
Superscripts
cal calculated property
exp experimental property
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C. Zhu et al. / Fluid Phase Equilibria 264 (2008) 259263 263
Acknowledgements
The support provided by the National Key Project (Nos.:
90210032, 50576001) for the completion of the present work
is gratefully acknowledged.
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