Three site primitive models of water and methanol

1
K. Aim, A. Babic and I. Nezbeda E. Hála
Laboratory of Thermodynamics Institute of
Chemical Process Fundamentals Academy of
Sciences, 165 02 Prague, Czech Republic E-mail
kaim_at_icpf.cas.cz --------------------------------
-------------------------------------------
Motivation and Goals In order to supplement
the so far incomplete VLE data and also to extend
their coverage to higher temperatures, the
experimental VLE data for carbon dioxide
aliphatic alcohol (methanol, ethanol, 1-propanol,
an 2-propanol) binary systems have been
determined. A high pressure apparatus for the
measurement of VLE was employed at pressures up
to 100 bar and temperatures up to 95 oC, with
sampling and chemical analysis of both (liquid
and vapour) phases. The supplemented database is
used to evaluate the available EOS suitable for
this type of systems, namely the Patel-Teja EOS
1, Patel-Teja EOS with Wong-Sandler mixing
rules 2, and PC-SAFT EOS 3 (and currently is
used to test the newly developed class of
equations of state based on the primitive model
of association).
2
Experimental Apparatus
(1) Equilibrium cell with quartz windows, (2)
Magnetic stirrer motor, (3) Water bath, (4) Water
mixer, (5) Electric heating, (6) Water cooling,
(7) RUSKA high pressure pump, (8) Vacuum pump,
(9) Carbon dioxide cylinder, (10) Glass flask
with alcohol, (11) ASL precision thermometer,
(12) HEISE pressure gauge, (13) Sampling
micro-capillaries, (14) Sample homogenizer, (15)
Helium cylinder, (16) Gas chromatograph.
3
System Carbon Dioxide Methanol

4
System Carbon Dioxide Ethanol

5
System Carbon Dioxide 1-Propanol
6
System Carbon Dioxide 2-Propanol
7
Comparison of EOS for MeOH- and EtOH- Systems
Methanol CO2, t25.01 C PT-EOS
k120.0479PT-EOSWSNRTL k120.0704,
alfa120.3916, a12384.77, a2124.4642PC-SAFT
k120.0266 PC-SAFT (w/o assocn.) k120.1470
Ethanol CO2, t50.0 C PT-EOS
k120.0932PT-EOSWSNRTL k120.0628,
alfa120.25546, a12103.91, a21131.601PC-SAFT
k120.1073
8
Comparison of EOS for 1-PrOH- and 2-PrOH- Systems
1-Propanol CO2, t60.00 C PT-EOS
k120.0911PT-EOSWSNRTL k120.0787,
alfa120.2902, a12333.81, a21107.71PC-SAFT
k120.0972
2-Propanol CO2, t85.00 C PT-EOS
k120.0952PT-EOSWSNRTL k120.07179,
alfa120.2181, a12278.23, a21222.49PC-SAFT
k120.1172
9

Equilibrium Cell Volume 65 cm3, Maximum P 10
MPa, Maximum T 100 oC
10

Conclusions
Vapor-liquid equilibria (VLE) in the carbon
dioxide aliphatic alcohol (namely methanol,
ethanol, 1-propanol, an 2-propanol) binary
systems have been determined experimentally at
elevated pressures roughly along isotherms of 30,
50, 60, and 85 oC. The data supplement the so far
rather fragmentary (and limited to temperatures)
information, allowing to constitute a
representative database for the class of systems
that can be used to make dependable evaluation of
available and newly developed EOS. Of the current
EOS examined, the full PC-SAFT EOS provides the
best results, while the other EOS tend to
erroneously predict phase split at lower
temperatures.
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