(395r) Azeotropic Adsorption Equilibrium of Mixed Organic Solvent On FAU Type High Silica Zeolite - Interpretation by Molecular Simulation and Do's Method

Azeotropic Adsorption Equilibrium of Mixed
Organic Solvent on FAU Type High Silica Zeolite - Interpretation by Molecular Simulation and Do's method -

Kazuyuki Chihara*, Tatsuharu Taira, Natsuki
Yamada, Yusuke Suzuki, Duong D. Do

Department
of Applied Chemistry, Meiji University, Kawasaki, Kanagawa 214-8571, Japan

Fax:
+81 - 44 - 934 - 7197 E-mail:chihara@isc.meiji.ac.jp

ABSTRACT

In recent years, instead of the
chlorofluorocarbon specified as the ozone-depleting substance, a chlorinated
organic compound, hydrocarbon, alcohol, etc. are used as an alternative washing
solvent, and they are used as a mixed solvent in many cases. Therefore,
adsorption operation of binary systems is needed. Furthermore, since azeotropic
adsorption may happen, in the case of the design of a solvent recovery system
and operation, those adsorption equilibria are required as basic data. IAS
theory can't treat the azeotropic adsorption. We applied the method of treating
the azeotropic adsorption, that is, to treat the adsorbed phase as a
combination of two independent adsorbed phases, and the IAS theory is applied
for each adsorbed phase(Do, 2000).

In this study, the
adsorption equilibrium of the FAU type high silica zeolite was obtained by
analyzing the adsorption phenomenon, using a Gravimetric adsorption experiment
device and a molecular simulation. The adsorbate used
was ethanol and trichloroethylene, which are the system of azeotropic
mixture. The experiments were carried out using a
batch system with circulation flow of the adsorbate mixture around the
adsorbent to prevent the concentration distribution in gas phase, changing the
total concentration and composition of ethanol and trichloroethylene, by
stepwise dosing of mixed solvent vapor. For this system, one azeotropic point appeared. Simulation
module in Materials Studio (Accelrys Inc.) was used throughout MC simulations.
It calculated by the Sorption module, and the adsorption isotherm was obtained.

Two kinds of
adsorption site or adsorption phase were observed in the cell (25.08 x 25.08 "²) by the
Sorption simulation of binary adsorption equilibria
for the system of EtOH-TCE(Fig.1). One phase containes EtOH and TCE (phase 1), and the other phase
containes only EtOH (phase 2). The coordinates of two sites were determined.
The ratio of EtOH amount adsorbed on both sites were counted from the simulated
adsorbed cell. The ratio was found to be constant through the simulation. Using
this constant ratio, the simulated or experimentally obtained amount adsorbed
were divided for phase 1 and 2. Then adsorption isotherms were determined for
both phases. Phase 1 was expressed as extended Langmuir. Phase 2 was expressed
as Langmuir. Total adsorption isotherm was observed as total of both phase
shown as X-Y diagram as follows.

Binary adsorption equilibria
for the system of EtOH-TCE of total concentration of 10000ppm are shown in
Fig.2 and Fig.3 in form of X-Y diagram (X is the mole fractions of gas phase
concentration of EtOH. Y is the amount adsorbed of TCE / total amount
adsorbed). Fig.2 shows the experimental result. Fig.3 shows the
simulation result.

Fig.1 Appearance
of ethanol and trichloroethylene that adsorbs zeolite

Fig.2 The
experimental result              Fig.3The
simulation result

Total
concentration of
10000ppm           Total
concentration of 10000ppm

Reference
list

Duong D Do,Adsorption
Analysis:Equilibria and Kinetics.Imperial College Press,London(2000)