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YANG, MAEDA, AND GOTO
phase in a continuous stirred tank reactor at a pressure
of 0.8 MPa. The influence of internal and external
mass transfer resistance for the synthesis of TAME
were investigated in a continuous-flow recycle reactor
by the work of Oost and Hoffmann [5]. In these re-
ports, isoamylene (IA), 2-methyl-1-butene (2MB1),
and 2-methyl-2-butene (2MB2) produced from steam
crackers and FCC units and methanol (MeOH) were
used as the starting materials.
In our previous works, MTBE and ETBE were syn-
thesized at atmospheric condition by a condensation
reaction between methanol or ethanol with tert-butyl
alcohol which is a coproduct of propylene oxide syn-
thesis from isobutane and propylene [6–8]. The re-
active distillation combined with pervaporation was
developed to achieve the purpose of continuous pro-
duction [9,10].
As a successive work, this study will deal with the
liquid synthesis of TAME by using methanol and tert-
amyl alcohol (TAA) which can be obtained from frac-
tionation of fusel oil (one kind of byproduct of ethanol
fermentation) or the process of the pentanes chlorin-
ation. Since the boiling point of TAA (375 K) is much
higher than 2MB1 (304 K) and 2MB2 (311 K), the
reaction between TAA and MeOH may take place at
atmospheric condition. To our knowledge, there are
no reports on this reaction system.
The subject of this work is to investigate the kinet-
ics of etherification between TAA and MeOH on a
protonated cation-exchange resin catalyst. The influ-
ence of internal and external diffusion, feed ratio and
the inhibition of water on the reaction are studied.
Apparatus
A 2.0 ϫ 10Ϫ4 m3 three necked round-bottom glass re-
actor with a jacket was used. A condenser was placed
in the central opening. A mixture of ethanol and water
in 50 vol.% was circulated within the condenser to
keep the temperature in 243 K for condensing 2MB1
and 2MB2 produced from the reaction. The other
openings were for sampling and temperature measure-
ments. A magnetic stirrer was rotated inside the re-
actor to suspend the catalyst. A water bath with a tem-
perature controller was connected to the jacket of the
reactor for obtaining the constant reaction tempera-
ture. A dry gas meter was connected through the con-
denser so as to check the presence of 2MB1 and 2MB2
in the gas phase.
Procedure
The mixture of TAA and MeOH in the batch reactor
was heated up to the desired reaction temperature by
the jacket. The reaction was started by adding the mea-
sured amount of catalyst. Samples (1.0 ϫ 10Ϫ6 m3)
were taken at an interval of one hour to measure the
concentrations of MeOH, TAA, 2MB1, 2MB2,
TAME, and H2O.
Four different temperatures (308, 313, 318, and
323 K) were adopted. Since the solution was in a boil-
ing state higher than about 325 K, the upper temper-
ature was limited to maintain the liquid phase. The
initial molar ratio (TAA/MeOH) was varied as 1, 1.5,
and 2. The initial water was chosen as 0, 0.5, and
1 mol. The catalyst weight, W was changed from 5 to
30 g. The agitation speed was in the ranges of
200–950 rpm.
To investigate the effects of these parameters on
the reaction rates, one parameter was changed while
others were kept constant. The standard condition was
323 K of reaction temperature, equimolar ratio of
TAA/MeOH, 950 rpm of agitation speed, and 10 g
weight of catalyst with 0.78 mm average diameter.
EXPERIMENTAL
Materials
The reagents of TAA (98.0% pure) and MeOH (99.8%
pure) were obtained from Wako Pure Chemical In-
dustries. Ltd.
Strong cation exchange resin in the Hϩ form, Am-
berlyst 15 from Rohm and Hass was used as the cat-
alyst in this study.
The ion exchange capacity, Q was 4.96 [mol-Hϩ/
(kg-dry resin)]. To investigate the influence of intra-
particle diffusion, the catalysts were sieved in three
kinds of meshsizes, which were in the ranges of 34–
32, 24–20, and 16–14. The corresponding particle av-
erage diameters were 0.61, 0.78, and 1.10 mm, re-
spectively.
Analysis
Analysis was carried out in the gas chromatograph
with 2.5 m column of Gaskuropack 54 60/80 mesh as
a packing material. The column temperature was set
at 473 K and carrier gas was helium at 0.12 MPa.
Good separations were achieved for all components.
RESULTS AND DISCUSSION
These catalysts were kept at 368 K in a vacuum
oven over night to get rid of any moistures before use.
Figure 1 shows the concentration profiles with time
for the synthesis of TAME from TAA and MeOH cat-