Selective isomerization of epoxides using magnetically recyclable ZSM-5 zeolite catalyst

Article abstract of DOI:10.1039/c5ra16922d

The application of magnetically recyclable ZSM-5 zeolite (MZZ) for epoxide isomerization reaction was presented. This catalyst exhibited a high catalytic efficiency for liquid phase rearrangement of 2-methyl-2,3-epoxybutane and styrene oxide, as well as high efficiency in separation, recycling with long lifetime and no significant loss of catalytic activity. The influences of reaction conditions such as solvent, reaction time, catalyst loading and temperature on the efficiency of epoxide isomerization were also investigated. Moreover, it was noticeable that for the epoxides investigated the high catalytic activity observed over the MZZ catalyst (conversion over 98% after 2 h reaction for both of two epoxides) was accompanied by the achievement of high selectivities, typically 79% and 82% for 2-methyl-2,3-epoxybutane and styrene oxide respectively, towards desired products with commercial applications.

Full text of DOI:10.1039/c5ra16922d

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Page 1 of 18
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Selective Isomerization of Epoxides Using of
Magnetically Recyclable ZSM-5 Zeolite Catalyst
Phan Huy Hoang*,1 and Nguyen Xuan Bach2
1
School of Chemical Engineering, Hanoi University of Science & Technology, No.1 Dai Co
Viet Street, Hanoi, Vietnam.
2
Hanoi Pedagogical University 2, Nguyen Van Linh Street, Phuc Yen District, Vinh Phuc
Province, Vietnam.
Corresponding Eꢀmail: hoang.phanhuy@hust.edu.vn
Acknowledgement: This research is funded by Vietnam National Foundation for Science and
Technology Development (NAFOSTED) under grant number “104.01ꢀ2013.02"
Abstracts:
The application of magnetically recyclable ZSMꢀ5 zeolite (MZZ) for epoxide isomerization
reaction was presented. This catalyst exhibited the high catalytic efficiency for liquid phase
rearrangement of 2ꢀmethylꢀ2,3ꢀepoxybutane and styrene oxide, as well as high efficiency in
separation, recycling with long lifetime and no significant loss of catalytic activity. The
influences of reaction conditions such as solvent, reaction time, catalyst loading and
tempreature on efficiency of epoxide isomerization were also investigated. Moreover, it was
noticeable that for the epoxides investigated the high catalytic activity observed over MZZ
catalyst (conversion over 98% after 2hrs reaction for both of two epoxides) was accompanied
by the achievement of high selectivities, typically 79% and 82% for 2ꢀmethylꢀ2,3ꢀ
epoxybutane and styrene oxide respectively, towards desired products with commercial
applications.
Introduction
Epoxides are very important and versatile intermediates in organic synthesis since they can
be readily transformed into a wide range of organic compounds [1,2]. Isomerization of
epoxides over acid catalysts is an important process to yield carbonyl compounds and its
halogenated derivatives [3], which are valuable compounds or intermediates used for
production of fragrances, pharmaceuticals, insecticides, fungicides, and herbicides. Several
catalytic systems have been developed for the isomerization of epoxides to carbonyl
compounds [4ꢀ8]. Acidꢀcatalyzed epoxide rearrangement reaction usually leads to ketones
and aldehydes, whereas the baseꢀcatalyzed reaction forms allylic alcohols as main products

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[9]. Using of homogeneous catalysis presents numerous drawbacks such as loss of the
catalyst, corrosivity, toxicity and generation of contaminated streams in most cases. Thus
many efforts have been conducted to find out heterogeneous catalysts to solve these problems.
For this reason heterogeneous catalysts such as alkaline earth metal sulfonates, mixedꢀmetal
oxides, silica–alumina gels, natural silicates, NafionꢀH and zeolites have been tested for
isomerization of epoxide [10ꢀ14]. Nevertheless, the competitive aldol condensation or
polymerization of aldehydes and rapid deactivation of catalysts by aggregation or coke
formation are still difficult problems at the industrial scale [3,9,15]. The use of conventional
catalysts often results in the formation of aldol condensation products and mixtures of
ketones and aldehydes as byꢀproducts. The numerous molecules formed by aldol
condensation are the first step in the formation of coke thus limiting the lifetime of catalysts.
The use of zeolitic catalysts for the isomerization of epoxide showed main advantage
due to their well defined pore system compared with homogeneous systems or other
heterogeneous catalysts such as metal oxides, silica–alumina gels or metal sulfates [16,17].
Indeed, zeolite materials in their proton form have been found to catalyze this type of
reactions [16,18]. Moreover, the well defined pore system of zeolites may suppress the side
reactions mentioned above [9,19]. Hence, high selectivities to aldehydes could be achieved in
the isomerization of styrene oxide and derivatives over various acid zeolites. Besides, the
practical application of catalysts in liquid phase reactions is hindered by both high costs and
difficulties in catalyst separation and recycling. Many different approaches have been
suggested to solve the difficulties in catalyst separation, such as filtration, polymeric supports
and other new separation techniques [20ꢀ22]. Each separation method has its own limitations
of cost, efficiency or generation of secondary waste. Magnetic separation has emerged as a
robust, highly efficient and rapid catalyst separation tool as it provides a convenient method
for removing and recycling magnetized species by applying an appropriate magnetic field

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[20,21,23]. This approach may prevent the agglomeration of the catalyst particles during
recovery and can increase the durability of the catalysts [24].
We were, therefore, motivated that magnetically recyclable ZSMꢀ5 zeolite that was
synthesized by deposition of ZSMꢀ5 zeolite on the surface of silicaꢀcoated magnetite particles,
could be applied for isomerization of epoxide to overcome the aboved mentioned problems.
These magnetic zeolite particles could take fully the advantages that are offered by both
magnetic separation and zeolite catalyst. Herein, we report the application of magnetically
recyclable ZSMꢀ5 zeolite for epoxide rearrangement reaction for improve the efficiency of
synthesis process in separation, recycling, lifetime and catalytic activity of catalyst.
Materials and Methods
Synthesis of core–shell magnetic ZSM-5 zeolite particles
Core/shellꢀstructured magnetic ZSMꢀ5 zeolite (MZZ) was obtained by following reported
method that was developed by our own group [20]. The uniform magnetite (Fe3O4) particles
were synthesized by a coprecipitation method by using FeCl2.4H2O and FeCl3.6H2O as
precursors. These Fe3O4 particles were then used as core for fabrication of silica coated
magnetite beads (Fe3O4/SiO2). Magnetite particles were added to a solution containing 50 mL
of ethanol, 5 mL of distilled water, and 2 g of aqueous ammonia at room temperature and the
resulting solution was vigorously stirred for 30 min. Tetraethoxysilane (TEOS, 0.4 mL) was
then rapidly added and the solution aged at room temperature for 12 h. Then the Fe3O4/SiO2
nanoparticles were magnetically separated, washed and then dried. The silica coated
magnetite particles were then introduced to ZSMꢀ5 synthetic solution for hydrothermal
synthesis at 150 oC in 20h to obtain core ꢀ shell magnetic ZSMꢀ5 zeolite (MZZ) catalyst. The
synthetic zeolite solution was obtained after aging for 12 h by stirring at room temperature,
with
a
mole ratio of the composition of TEOS/TPAOH/NaAlO2/KOH/H2O
=
8:1.05:0.1:0.85:64.500.

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Epoxide rearrangement reaction
To examine the catalytic efficiency as well as the separation and recycle of the magnetic
zeolite particles, the catalytic rearrangements of epoxide were performed. All reactions were
carried out under a nitrogen atmosphere in a 100 ml two necked round bottomed flask
equipped with a water condenser and a magnetic stirrer. The solvent and the catalyst were
initially placed in the flask. In a typical experiment, epoxide (1 g) was directly added to a
mixture of magnetic zeolite catalyst and solvent (10 ml) and the mixture was stirred for the
appropriate reaction time. The employed catalyst loading was 5% w/w over reactant (1 g of
epoxide and 50 mg of catalyst). When the reaction was complete, the catalyst was separated
by external magnetic field and washed several times, then the solvent was removed to get the
products [4].
Characterization
Xꢀray diffraction (XRD) was performed on a Rigaku D/max lllC (3 kW) with a θ/θ
goniometer equipped using a CuꢀKα radiation generator. Transmission electron microscopy
(TEM) was performed using a JEM 2100F, JEOL, Japan, operating at 200 kV. Scanning
electron microscopy (SEM) was performed using a JSMꢀ7000F, JEOL, Japan. Brunauer–
Emmett–Teller (BET) analysis was used to determine the surface areas of the samples. The
Si/Al ratio of the samples was determined by induced coupled plasmaꢀatomic emission
spectroscopy (ICPꢀAES) with a Varian VISTAꢀAX equipment. Temperature programmed
desorption of ammonia (NH3ꢀTPD) was performed on a conventional apparatus equipped
with a thermal conductivity detector to detemine the acidic properties of the catalysts. The
sample was pretreated at 500 °C for 2 h with a N2 flow and then cooled down to ambient
temperature. NH3 was supplied to the system followed by flushing with N2 at 150 °C for 1 h.
The TPD profile was obtained by heating the sample from 150 to 500 °C at a rate of

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15 °C/min. The NH3 desorbing between 150 and 500 °C was trapped in boric acid and then
titrated with a standard H2SO4 solution [3,15]. According to the individual peak area,
theamount of NH3 can be calculated and then converted into the acid concentrations with the
assumption of one NH3 molecule per acid site.
The structures of products obtained from the rearrangement reactions were confirmed
1
1
by their Hꢀ NMR spectra. The yield of the aldehyde product was also determined by Hꢀ
NMR with trimethylphenylsilane (PhSiMe3) as internal standard, which was added after the
1
synthetic workꢀup just prior to the NMR analysis. The H NMR spectra were performed in
CDCl3 on a Bruker DMX600 spectrometer with a 7788 Hz spectral width, a relaxation delay
of 1.0 s, and a pulse width of 30o. The catalyst reaction products were also analyzed with a
VARIAN 3800 gas chromatograph equipped with a capillary column (HPꢀFFAP) with
dimensions 60m×0.32mm, using a flame ionization detector (FID). Identification of the
different reaction products was performed by mass spectrometry (VARIAN SATURN 2000)
using standard compounds.
Results and Discussion
Synthesis of core–shell magnetic ZSM-5 zeolite (MZZ) particles
Core/shellꢀstructured magnetically recyclable ZSMꢀ5 zeolite (MZZ) was obtained by
following reported method that was developed by our own group [20]. The MZZ particles
were characterized by Xꢀray diffraction (XRD), transmission electron microscopy (TEM) and
scanning electron microscopy (SEM) and shown in Figure 1. Figure 1A showed XRD
patterns of the asꢀsynthesized MZZ particles. Two sets of diffraction peaks appeared in their
XRD patterns, one set of peaks was consistent with the magnetite Fe3O4 crystals (JCPDS card
No. 19ꢀ0629), while the other set of peaks matched well with ZSMꢀ5 zeolite (JCPDS card No.
44ꢀ0002) [20]. This result indicated that core–shell magnetic ZSMꢀ5 zeolite (MZZ) particles
have been successfully prepared. The TEM images (Fig. 1B,C) showed that the asꢀobtained

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magnetic zeolite particles were homogeneous in size and morphology with an average
diameter of about 300 nm, and each particle just contains one single Fe3O4 core.
Figure 1. XRD patterns (A) of asꢀprepared magnetic ZSMꢀ5 zeolite (MZZ) particles (The red marks
(▲) are assigned to standard patterns of magnetite and the black marks (●) are assigned to standard
patterns of ZSMꢀ5 zeolite), TEM images (A,B) and SEM images (C,D) of magnetic ZSMꢀ5 zeolite
(MZZ) particles.
The chemical composition and some textural properties of the catalysts are shown in
Table 1. The BET surface area and external surface area of magnetic ZSMꢀ5 zeolite were
calculated to be 428.2 and 86.8 m2/g, respectively. These results suggest that these MZZ
particles had high surface area, and was higher than conventional ZSMꢀ5 zeolite. It could be

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explained that the asꢀobtained MZZ particles after coating of zeolite layer on Fe3O4/SiO2 core
had the rough surfaces (see Figure 1D,E), presumably due to the random growth of the ZSMꢀ
5 zeolite particles [20]. These rough surfaces could provide high surface area and large
external surface areas for the adsorption of guest species. Moreover, core–shell structure with
void space generated from shrinkage of silica coated magnetite core also could be attributed
to contribute to the high surface area of MZZ particles.
Table 1. Chemical composition and textural properties of MZZ catalyst
Si/Al,
Acidity
Pore diameter, SBET
,
SEXT
m2/g
,
V pore ,
cm3/g
Catalyst
Å
m2/g
(mol/mol)
(mmol/g)
Magnetic ZSMꢀ5
zeolite
86
5.5
428.2
86.8
0.219
0.48
As also seen in Table 1, MZZ samples possessed Si/Al molar ratios slightly higher
than that corresponding to the synthesis gels (Si/Al = 86). The acidity of MZZ sample has
been investigated by NH3ꢀTPD measurement. The total amount of ammonia desorbed
(mmol/g) may be related to the number of acid sites. It’s seen that the acidity of MZZ was
relatively high with acid concentration of 0.48 mmol/g, and comparable to the results
reported in the literature [3,15, 26]. It is well known that zeolites have been widely used in
ion exchange, adsorbents, separation and catalysis for organic synthesis. The magnetic
separation has emerged as a robust, highly efficient separation tool with many advantages. It
provides a convenient method for removing and recycling by applying an appropriate
magnetic field [20,24]. Thus in this current work, we applied asꢀsynthesized MZZ catalyst for
liquid phase epoxide isomerization reaction to exploit the advantages of these particles for the
organic synthesis.
Catalytic and recycle efficiency of core-shell magnetic ZSM-5 zeolite
Isomerization of epoxides over acid catalysts is an important process to yield carbonyl
compounds and its halogenated derivatives [3], which are valuable compounds or

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intermediates used for the preparation of perfumes, synthetic food flavourings and
pharmaceuticals. However, the competitive aldol condensation or polymerization of
aldehydes and rapid deactivation of catalysts by coke formation are still difficult problems at
the industrial scale [3]. Thus coreꢀshell magnetic ZSMꢀ5 zeolite catalyst was applied for
epoxide isomerization reaction in order to assess the advantages offered by both magnetic
separation and zeolite catalyst. Two epoxides having different molecular geometry have been
selected as model compounds: 2ꢀmethylꢀ2,3ꢀepoxybutane and styrene oxide (Scheme 1).
Scheme 1. Catalytic rearrangement of 2ꢀmethylꢀ2,3ꢀepoxybutane (1) and styrene oxide (2)
It is known that the solvent plays an important and sometimes decisive role in the
catalytic behavior of a catalyst [25]. In most of organic reactions, solvents must be added to
dilute reactants in order to control the side reactions and prevent the catalyst deactivation.
Therefore, first attempt we studied the effect of the solvent on epoxide isomerization by
doing several isomerization reactions of 2ꢀmethylꢀ2,3ꢀepoxybutane and styrene oxide with
several solvents and under identical conditions. Table 2 showed the conversion results
obtained using 0.05 g of MZZ, after variuous reaction time at 40 C. From the Table 2, it is
◦
evident the importance of the correct selection of solvents. The results indicated that the
conversions of 2ꢀmethylꢀ2,3ꢀepoxybutane and styrene oxide in presence of magnetic ZSMꢀ5
zeolite catalyst (MZZ) were different with different solvents used. The conversions were low

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in methanol even after 4 hrs, presumably due to the weakening of the acidity of the zeolite
catalytic sites by hydrogen bonding to methanol, hindering the participation of the proton in
the solvolysis of the oxirane ring [4,25]. Moreover, the low selectivity towards aldehyde
obtained might be related with the basic character of the methanol which could accelerate the
formation of alcohol byproduct [9,25,26]. The conversion yield was high after just 1 hr in
solvents of acetone and dichloromethane. It’s observed that the higher solvent polarity the
lower conversion of epoxide. This behavior may be explained by the decrease in the substrate
concentration within the pores of the catalyst as the polar nature of the solvent increases [25].
Indeed, the higher the solvent polarity, the lower the concentration of the substrate in the
vicinity of the active sites and the lower the epoxide conversion would be, as indicated by the
experimental results. However, a low polar solvent such as toluene showed slow reaction
with the lower epoxide conversion than acetone. This catalytic performance over magnetic
ZSMꢀ5 zeolite could be more related with intraparticle diffusion problems, arising from the
limited pore size of the zeolitic material, than with the polarity effects [25].
The results also showed that the conversion obtained in the rearrangement of 2ꢀ
methylꢀ2,3ꢀepoxybutane over MZZ catalyst was sligh higher than that obtained using styrene
oxide. It is well established that in addition to the different reactivity of the epoxide, the
catalytic performance over MZZ catalyst is also related to the overall accessibility of the
substrate to the active sites, which is influenced by the possible presence of both steric and
intracrystalline diffusion problems. 2ꢀmethylꢀ2,3ꢀepoxybutante molecule has a lower
dimensions than that of styrene oxide as well as much lower than the diameter of the ZSMꢀ5
zeolite micropores [26]. Hence, this molecule could enter more easily the zeolite micropores
and thus gave higher reactivity than molecule of styrene oxide. As a result of aboved findings,
acetone was used as the solvent for next studies.

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Table 2. Effect of solvent on isomerization of epoxide using magnetic ZSMꢀ5 zeolite catalyst a
2-methyl-2,3-epoxybutane isomerization Styrene oxide isomerization
Solvent
Reaction time,
Conversionb,
Selectivityc,
Conversion,
%
Selectivity,
%
h
1
2
4
1
2
4
1
2
4
1
2
4
%
%
34.7
40.4 (15.2)d
40.9 (15.0)
40.0 (15.8)
75.2 (14.0)
74.8 (14.6)
75.7 (14.1)
77.8 (12.7)
79.0 (12.0)
78.2 (12.1)
58.1 (23.5)
57.3 (23.9)
58.0 (24.3)
31.4
65.7
66.1
65.5
80.0
79.1
79.5
82.8
82.1
82.7
88.7
88.0
88.2
Methanol
50.2
46.8
60.3
54.5
84.5
80.1
Dichloromethane
Acetone
95.8
91.7
97.1
96.0
86.3
84.6
96.9
93.5
~100
48.7
99.1
40.2
Toluene
60.9
53.9
72.4
63.8
a
Reactant (1 g) and MZZ catalyst (0.05 g) in 10 ml solvent at desired temperature under N2
atmosphere.
b,c Calculated from GC and 1H NMR.
( )d Selelctivity of 1b
As also seen in Table 2, the conversion yields of epoxide using magnetic ZSMꢀ5
zeolite catalyst (MZZ) increased with the increase of reation time. In particular, the
conversion of 2ꢀmethylꢀ2,3ꢀepoxybutane was 86.3% for reaction time of 1hr and nearly
complete (~100%) for reaction time of 4 hrs in acetone solvent, with the selectivity of 1a
product (2,2ꢀdimethylpropanal) was about 78.2% together with 12.1% second product 1b
,
methylisopropylketone). While the conversion of styrene oxide was 84.6% for 1 hr reaction
time and 99.1% for 4 hr reaction time in acetone solvent, with the selectivity of 2a product
(phenylacetaldehyde) was over 82%. These obtained conversions were high and comparable
to the results reported in the literatures [3,4,26]. It is wellꢀknown that the acid catalytic
epoxide isomerization includes of the initial attack step of the electrophilic reagent to the

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oxirane ring, followed by the ring opening, resulting intermediate carbocations that
subsequently could be transformed into aldehyde and/or ketone products [26]. The branch (2ꢀ
methylꢀ2,3ꢀepoxybutane) and cyclic epoxide (styrene oxide) are both reactive epoxides that
favours the initiation step of the isomerization reaction, and thus results the high conversion
of reaction. Furthermore, coreꢀshell magnetic ZSMꢀ5 zeolite had a high surface area and high
external surface area due to rough surface and coreꢀshell structure. This high surface area
could enhance accessibility of the epoxide molecules to the active sites of catalyst. And for
the sterically hindered epoxides, the catalytic rearrangement could occur on the external
surface of the zeolite [20,26]. Hence the high conversion of reactants could be achieved over
coreꢀshell magnetic ZSMꢀ5 zeolite.
Several reactions were conducted using various amount of MZZ catalyst to
investigate the influence of zeolite catalyst loading on isomerization of epoxides (Figure 2). It
was found that increasing the catalyst loading from 0% to 5% w/w over reactant would
increase the conversion of reactants (2ꢀmethylꢀ2,3ꢀepoxybutane and styrene oxide). It is clear
from the results that reaction carried out in absence of catalyst yielded a low conversion.
These results showed that the contribution of the nonꢀcatalyzed reactions is negligible under
the conditions used in these reactions (Fig. 2), similar to the previous reports [3,4,26].
Moreover in the absence of catalyst, the selectivity of 1a and 1b product was 48.8% and 42.3%
respectively, while the selectivity of 2a product was 79.1%. These results were lower than
that obtained from reaction in the presence of catalyst. This indicated that the zeolite catalyst
would favour the formation of aldehyde products [4,9,19]. The highest conversions of
reaction were obtained at catalyst loading of 5%, for which the conversion was ~100% and
99.1% after 4hrs for 2ꢀmethylꢀ2,3ꢀepoxybutane and styrene oxide, respectively. At the
amount of catalyst lower than 5% could still give good conversion of 2ꢀmethylꢀ2,3ꢀ
epoxybutane and styrene oxide, but the reactions were slower and longer reaction times were

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required in order for them to go to completion. However, when increased the amount of
catalyst from 5% to 7% w/w over reactant brought a decrease in the conversion of 2ꢀmethylꢀ
2,3ꢀepoxybutane as well as styrene oxide. The reduction in conversion may be due to
increased formation of a polymeric material when increased catalyst loading [4]. A series of
experiments was therefore conducted using a zeolite catalyst loading of 5% w/w over reactant
(0.05 g for 1 g reactant) for further studies.
Figure 2. Effect of MZZ catalyst loading on isomerization of epoxide (Reaction conditions: reactant
(1 g) in 10 ml acetone, at 40oC under N2 atmosphere after 2hrs reaction).
Another study was carried out at different temperatures, the results were shown in
Table 3. The obtained results denoted that the temperature influenced significantly on the
epoxide isomerizations. It could be seen that conversion of 2ꢀmethylꢀ2,3ꢀepoxybutane and
styrene oxide increased with the increase of temperature from 30 to 50oC. However, when
temperature further increased to 60oC brought a decrease in the conversion of 2ꢀmethylꢀ2,3ꢀ
epoxybutane as well as styrene oxide. This behavior could be explained that the temperature
of reaction was higher than boiling point of solvent thus the evaporation of solvent could be
occured during raction resulting in the loss of solvent and decreasing the conversion. Hence

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the suitable temperature for epoxide isomerization was chosen as 50oC, and this temperature
was used for next experiments.
Table 3. Effect of temperature on isomerization of epoxide using magnetic ZSMꢀ5 zeolite catalyst a
Conversionb, %
2-methyl-2,3-epoxybutane
Temperature, oC
Styrene oxide
83.8
81.4
30
96.9
99.4
98.1
93.5
98.6
97.3
40
50
60
a
Reactant (1 g) and MZZ catalyst (0.05 g) in 10 ml acetone under N2 atmosphere after
2hrs reaction.
b Calculated from GC and 1H NMR.
In heterogeneous catalysis, the stability of the catalyst is an important issue from the
viewpoint of a green sustainable protocol. Therefore, the recycle efficiency and stability of
coreꢀshell magnetic ZSMꢀ5 zeolite was tested by recycling and reusing the catalyst seven
times (Figure 3). In typical, samples of magnetic ZSMꢀ5 zeolite particles were recovered
from the reactions by using external magnetic field, then were regenerated by calcination at
550oC and reused in isomerization reactions identical to those from which the samples were
recovered. The obtained results were recorded in Table 4. It was seen that the magnetic ZSMꢀ
5 zeolite catalyst could be recycled and reused efficiently for several times with only modest
reduction in the conversion of 2ꢀmethylꢀ2,3ꢀepoxybutane as well as styrene oxide. It
indicated that the magnetic zeolite had long durability and was more resilient to catalytic
deactivation. It could be assumed that the easy removing and recycling of magnetic ZSMꢀ5
zeolite (MZZ) by applying an appropriate external magnetic field would prevent the
agglomeration of the catalyst particles hence may increase the durability of the zeolite
catalysts with no significant loss of catalytic activity [20,24]. Moreover, the high surface area
as well as high external surface area of coreꢀshell magnetic ZSMꢀ5 zeolite could enhance

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accessibility of the epoxide molecules to the active sites and enhance the diffusion and
transfer of products out of catalyst pore. This could reduce the formation of coke in catalyst
pore and/or surface that may limit the lifetime of catalyst and thus increase the durability of
catalyst.
Figure 3. Separation and reuse of magnetic ZSMꢀ5 zeolite for isomerization of epoxide
Table 4. Separation and reꢀuse of coreꢀshell magnetic ZSMꢀ5 zeolite (MZZ) catalyst
in the isomerization of epoxide according to Scheme 1a
Conversion (%)b
Recycles number
(run)
2ꢀmethylꢀ2,3ꢀepoxybutane
Styrene oxide
98.6
1
2
3
4
5
6
7
99.4
96.8
93.6
92.0
91.2
89.5
88.1
94.3
93.1
92.8
91.0
88.7
86.2
a
Reactants (1 g) and MZZ catalyst (0.05 g) in acetone (10 ml) at
50oC temperature under N2 for 2hrs.
b Calculated from 1H NMR.
Furthermore, it is to be noted here that, homogeneity of core–shell catalyst particles
were maintain in the samples and etching of the sacrificial SiO2 layer for resulting the voids
did not continue even after several times of catalyst recycling. The shell layer of MZZ
particles after several reaction cycles did not change, and small zeolite particles could not be

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detected in the reaction solution. The isomerization of 2ꢀmethylꢀ2,3ꢀepoxybutane and styrene
oxide over pristine zeolite ZSMꢀ5, which was obtained from similar molar ratio composition
of zeolite synthetic gel with MZZ particles were investigated. Under similar reaction
condition, isomerization over pristine zeolite ZSMꢀ5 resulted in conversion of 95.6% and
93.8% for 2ꢀmethylꢀ2,3ꢀepoxybutane and styrene oxide, respectively. These conversion
values were slightly lower than conversion values obtained from MZZ catalyst (99.4% and
98.6% for 2ꢀmethylꢀ2,3ꢀepoxybutane and styrene oxide, respectively). This behavior could be
attributed to the slightly higher surface area as well as higher external surface area of MZZ
particles than pristine ZSMꢀ5. This result indicated that magnetite core was well insulated
from the shell layer of zeolite and did not affect the catalytic reaction. These observations
strongly suggest that the reaction proceeds heterogeneously over the catalyst.
Conclusion
The catalytic activities and recycle efficiency of coreꢀshell magnetic ZSMꢀ5 zeolite (MZZ)
was investigated. The catalytic performance of MZZ in epoxide isomerization showed that
this catalyst presented a high catalytic efficiency with both high epoxide conversions and
high selectivity towards the desired products. Being magnetically separable, these MZZ
catalyst particles were conveniently separated, easily regenerated by heating and reused up to
seven times with no significant loss of catalytic activity. This coreꢀshell magnetically
recyclable catalyst is a promising candidate for other important organic conversions and
industrial catalytic applications.
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Highlight of the work
The magnetically recyclable ZSM-5 zeolite (MZZ) with high catalytic activity, high
efficiency in separation, recycling and long lifetime for epoxide isomerization reaction was
presented.
Graphic