Highly selective formation of cyclopentanol through liquid-phase cyclopentene hydration over MCM-22 catalysts

Article abstract of DOI:10.1246/cl.2002.224

MCM-22 catalyst exhibits an extremely high shape selectivity not observed on other zeolites of MFI, MOR and BEA structures, in that it effectively catalyzes the liquid-phase hydration of cyclopentene at a conversion up to 10% and a cyclopentanol selectivi

Full text of DOI:10.1246/cl.2002.224

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Chemistry Letters 2002
Highly Selective Formation of Cyclopentanol through Liquid-Phase Cyclopentene
Hydration over MCM-22 Catalysts
Duangamol Nuntasri, Peng Wu, and Takashi Tatsumi
Division of Materials Science and Chemical Engineering, Graduate School of Engineering, Yokohama National University,
79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501
(Received October 22, 2001; CL-011032)
MCM-22 catalyst exhibits an extremely high shape selectivity
catalysts in this field to result in a new environmentally benign
process.
not observed on other zeolites of MFI, MOR and BEA structures, in
that it effectively catalyzes the liquid-phase hydration of cyclo-
pentene at a conversion up to 10% and a cyclopentanol selectivity as
high as 99%.
ZSM-5, MOR and Beta zeolites were obtained commercially.
MCM-22 was hydrothermally synthesized using hexamethylene-
imine as a structure-directing agent according to the previous
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procedures. All the zeolites were transformed to proton-type by
ion-exchange technique using NH4NO3 solution. The liquid-phase
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The production of alcohols by the hydration of olefins in the
presence of aqueous sulfuric acid is an important and widely used
industrial process. Nevertheless, it suffers from several disadvan-
tages, such as the corrosion of the apparatus, and the production of
undesirable salts. The difficult handling problems associated with
liquid acids can be partially obviated by solidifying the liquid acid
such as phosphoric acid impregnated silica, or using organic ion-
exchange resins. However, these materials give rise to new
problems such as easy release of phosphorus and low thermal
stability of resins at elevated temperatures.
cycloalkene hydration wascarried outbatch-wise ina 50 cm teflon-
lined autoclave reactor. For a typical run, 0.3 mol of water and
0.06 mol of cycloalkene were mixed with 1 or 2 g of catalyst in the
reactor. Then the reaction was carried out by heating the mixture
under vigorous stirring at 373–413 K for 6–120 h. In some cases, the
reaction is performed under Ar atmosphere. The reaction mixture
was analyzed by a gas chromatograph (Shimadzu 14A) equipped
with a 50 m OV-1 capillary column. The products were determined
on a gas chromatograph-mass spectrometer (JEOL DATUM-JMS-
AX 500).
Searching for new-type solid acid catalysts for olefin hydration
is thus a research subject of great interests. Aluminosilicate zeolites,
with high surface acidity, uniform channels of molecular level size
and excellent thermal stability, seem to be promising hydration
Table 1 compares the liquid-phase hydration of cyclohexene
and cyclopentene catalyzed by various proton-type zeolites. The
experiments were carried out at 393 K under air. The products were
predominately cycloalcohol, dicycloalkyl ether and cycloalkene
dimer. In the case of cyclohexene hydration, ZSM-5 was obviously
a catalyst superior to other zeolite catalysts based on both the
conversion and the alcohol selectivity. MOR zeolite showed lower
conversion and alcohol selectivity than ZSM-5; it lacks shape
selectivity due to the large pores of 12-membered ring (MR). Beta
zeolite containing hydrophilic silanols at defect sites and three
dimensional 12-MR channels, were also less effective than ZSM-5.
These results are consistent with those reported previously,
verifying that high-silica ZSM-5 with high hydrophobicity serves
as a water-tolerant solid acid catalyst and deeply suppresses the
formation of bulky ether and dimer owing to the restricted transition
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catalysts. Asahi Chem. Ind. recently developed an epoch-making
process for cyclohexanol production, i.e. the liquid-phase hydration
of cyclohexene using ZSM-5 zeolite catalyst, which leads to
energy-saving and environmentally friendly new processes for
producing the raw materials of "-caprolactam for Nylon-6 and
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adipic acid for Nylon-66. This process was developed by fully
taking the advantages of the hydrophobicity of high silica ZSM-5
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zeolite and the shape selectivity of MFI structure.
The slurry process like cyclohexene hydration is still fewer
compared to other gas-solid processes using zeolite catalysts.
Making full use of various zeolite catalysts is expected to develop
new processes for the production of other alcohols such as
cyclopentanol because cyclopentanone, the oxidation product of
cyclopentanol, is an important intermediate chemical for perfumes
and pharmaceuticals. Here, we report that MCM-22 zeolite is a
suitable catalyst for the selective formation of cyclopentanol from
cyclopentene hydration, which may expand thepossibility of zeolite
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state selectivity derived from the 10-MR channels. Nevertheless,
MCM-22 showed comparable cyclohexanol selectivity to ZSM-5,
although it was somewhat less active.
In the case of cyclopentene hydration, not only MOR and BEA
but also ZSM-5 greatly showed decreased alcohol selectivity
probably because their pores are too large to induce the high shape
Table 1. Liquid-phase cycloalkene hydration catalyzed by various zeolite catalystsa
Copyright Ó 2002 The Chemical Society of Japan

Chemistry Letters 2002
225
selectivity for cyclopentanol with relatively smaller molecular size.
However, MCM-22 maintained the alcohol selectivity higher than
90%, indicating that it is a promising catalyst for producing
cyclopentanol selectively.
When the reaction was conducted under Ar atmosphere, the
outstanding cyclopentanol selectivity given by MCM-22 was
further enhanced to high as 98% as a result of restricting
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dramatically the formation of 1,2 -bicyclopentene (Table 2, entries
0
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and 2). Conceivably, 1,2 -bicyclopentene was formed from the
reaction of cyclopentene with the intermediate yielded from the
cyclopentene peroxide formed by the allylic oxidation. The reaction
at 393 K for 6 h gave nearly 90% of the conversion for 18 h,
indicating that initially the reaction rate was fast, and then slowed
down probably because of the deactivation or approaching the
thermodynamic equilibrium of the reaction between cyclopentene
and cyclopentanol. To clarify this issue, the reverse reaction,
dehydration of cyclopentanol, was performed over ZSM-5 under
the same conditions as Entry 2 in Table 2. Cyclopentanol was
readily converted at 95% conversion into cyclopentene and
dicyclopentyl ether with selectivity of 94% and 6%, respectively.
The equilibrium is thus considered to take the lead in the hydration.
Cyclopentene hydration is an exothermic reaction, which was
confirmed by the decrease in the conversion with rising the reaction
temperature to 413 K (Table 2, entry 4). High conversion was thus
expected by conducting the reaction at low temperature which
would be favorable for the equilibrium shift to cyclopentanol.
However, the conversion increased with the time very slowly at
Figure 1. Cyclopentene hydration over MCM-22 and ZSM-
. Catalyst 1-2 g; water: cyclopentene (molar ratio) ¼ 5{30;
temperature, 393 K.
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channels. Neither the alkene conversion nor the alcohol selectivity
were affected by the selective poisoning of acid sites in open spaces
with bulky basic agent of 2,4-dimethylquiniline. This indicates the
hydration occurred essentially within the 10-MR channels the
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aperture of which has a free diameter of 4:0 Â 5:9 Aꢀ . The elliptic
channels, smaller than the 10-MR channels of MFI structure
(5:4 Â 5:6 Aꢀ ), are presumed to be suitable for the shape selective
formation of cyclopentanol.
In conclusion, MCM-22 has been found to be an active and
highly selective catalyst for cyclopentene hydration. The alkene
conversion and alcohol selectivity can be improved to as high as
10% and 99%, respectively, by carrying out the reaction under Ar
atmosphere and increasing the mole ratio of water to alkene.
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73 K (Table 2, entries 5–7), and reached only 4.1% even after the
reaction for 120 h. The hydration occurred more slowly at reaction
temperatures lower than 373 K (not shown). The acid sites of
zeolites seem to hardly act as catalytic centers for the liquid-phase
olefin hydration at too low temperatures. Above results suggest that
an optimum temperature, i.e. 393 K is necessary for the hydration of
cyclopentene by taking thebalancebetween thereaction rate andthe
equilibrium problem.
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(
Table 2. Effect of reaction conditions on the cyclopentene hydration over MCM-22 catalysta