Synthesis and catalytic performance of ZSM-5/MCM-41 composite molecular sieve from palygorskite

Article abstract of DOI:10.1134/S003602441710017X

ZSM-5/MCM-41 composite molecular sieve has been hydrothermally synthesized through a two-step crystallization process using palygorskite (PAL) as silicon and aluminum source. The products were characterized by various means and their catalytic properties for acetalization of cyclohexanone and esterification of acetic acid and n-butanol were also investigated. In the first step ZSM-5 zeolite could be formed from the acid-treated PAL after hydrothermal treatment using tetrapropylammonium bromide as template. XRD patterns, N₂ adsorption and desorption data, and TEM images show that the composite obtained in the secondary step had a well-ordered mesoporous MCM-41 phase and a microporous ZSM-5 zeolite phase. Compared with ZSM-5, ZSM-5/MCM-41 composite possessed more total acid amount, weak acid sites and large pore structure due to the formation of MCM-41 and exhibited higher catalytic activity for the acetalization and esterification reaction.

Full text of DOI:10.1134/S003602441710017X

ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2017, Vol. 91, No. 10, pp. 1883–1889. © Pleiades Publishing, Ltd., 2017.
CHEMICAL KINETICS
AND CATALYSIS
Synthesis and Catalytic Performance of ZSM-5/MCM-41
Composite Molecular Sieve from Palygorskite1
Jinlong Jianga,b,*, Mei Wua, Yong Yanga, Chuansong Duanmub, Jing Chena, and Xu Gub
aFaculty of Chemical Engineering, Key Laboratory for Palygorskite Science and Applied Technology of Jiangsu Province,
Huaiyin Institute of Technology, Huaian 223003, P.R. China
bJiangsu Provincial Engineering Laboratory for Advanced Materials of Salt Chemical Industry,
Huaiyin Institute of Technology, Huaian 223003, P.R. China
*e-mail: jiangjinlong75@163.com
Received May 31, 2016
Abstract—ZSM-5/MCM-41 composite molecular sieve has been hydrothermally synthesized through a two-
step crystallization process using palygorskite (PAL) as silicon and aluminum source. The products were
characterized by various means and their catalytic properties for acetalization of cyclohexanone and esterifi-
cation of acetic acid and n-butanol were also investigated. In the first step ZSM-5 zeolite could be formed
from the acid-treated PAL after hydrothermal treatment using tetrapropylammonium bromide as template.
XRD patterns, N2 adsorption and desorption data, and TEM images show that the composite obtained in the
secondary step had a well-ordered mesoporous MCM-41 phase and a microporous ZSM-5 zeolite phase.
Compared with ZSM-5, ZSM-5/MCM-41 composite possessed more total acid amount, weak acid sites and
large pore structure due to the formation of MCM-41 and exhibited higher catalytic activity for the acetaliza-
tion and esterification reaction.
Keywords: palygorskite, ZSM-5, MCM-41, composite molecular sieve
DOI: 10.1134/S003602441710017X
1. INTRODUCTION
different silicon sources [2]. For example,
MFI/MCM-41 and MCM-49/ZSM-35 composite
materials were one-step synthesized in the two-tem-
plate synthesis gel system using sodium silicate [5] and
silica sol [6] as silicon sources, respectively. Through a
two-step crystallization process, namely an in situ
coating method, ZSM-5/MCM-41, ZSM-5/MCM-
48, Beta/MCM-41, and MCM-22/MCM-41 com-
posite materials were also synthesized with two tem-
plates from different silicon sources such as fume silica
[4, 7], sodium silicate [3, 8], silica sol [9], and tetra-
ethoxysilane [10]. In the ex situ coating method, the
preformed zeolite seeds [11] and zeolite crystals [12,
13] were added into the mesoporous molecular sieve
synthesis gel prepared from tetraethoxysilane, result-
ing in the formation of Beta/MCM-41 and Y/MCM-
48 composite after hydrothermal treatment. In addi-
tion, MOR/MCM-41, ZSM-5/MCM-41, and ZSM-
5/SBA-15 were also obtained through recrystallization
of zeolites [14–17], ion-exchanged TPA-mesoporous
materials [18], and SBA-15 [19] in the alkaline solu-
tion, respectively. To avoid using expensive chemicals
and environmental contamination, a clay mineral,
kaolin, was used to prepare micro/mesoporous com-
posite materials such as kaolin/NaY/MCM-41 and
Ln-ZSM-5/MCM-41 composites [20, 21].
Zeolites are crystalline materials with uniform and
ordered micropores and have been applied in petro-
chemical industry for their strong acidity and high
hydrothermal stability. This microporous structure
exhibited a high surface area and shape selectivity, but
also limited the catalytic properties because of a low
diffusion rate of reactants, especially in the reactions
involving large molecules [1]. As compared to zeolites,
composite molecular sieves with micro/mesoporous
structure showed higher catalytic performance due to
the synergistic effects of zeolitic and mesoporous
phases in the reactions [2]. The micro/mesoporous
composite materials have larger pore size, strong acid-
ity of zeolites and integration of microporous and
mesoporous structures, which avoided the restrictions
of zeolites and enhanced the access for large molecules
to the effective active sites, resulting in higher catalytic
activity than that of mechanical mixture and individ-
ual molecular sieves [3, 4].
Several synthesis strategies were developed to pre-
pare those composite materials such as co-synthesis,
in situ and ex situ coating, and recrystallization of
ordered mesoporous materials and zeolites by using
1
The article is published in the original.
1883

1884
JINLONG JIANG et al.
Palygorskite (PAL) is also a clay mineral and has
2.2. Characterization
been used as catalyst carrier, adsorbent, desiccant and
polymer filler. In the last few years, there have a few
reports that PAL was in situ converted to MCM-41
[22], zeolite A [23], and ZSM-5 [24, 25] after
mechanical grinding and acid treatment or acid leach-
ing, followed by hydrothermal treatment. The latter
showed high catalytic cracking performance for Cana-
dian light gas oil [24].
XRD patterns of the samples were collected on a
D8 Discover X-ray powder diffractometer (Bruker)
using CuKα radiation (40 kV, 40 mA). Scanning elec-
tron microscopy (SEM) images and element analysis
of the samples were obtained by using the Hitachi S-
3000N microscope with integrated energy dispersive
X-ray analytical system (EDX, Horiba EX-250).
Transmission electron microscopy (TEM) micro-
In this study, ZSM-5/MCM-41 composite molec- graphs were determined on a JEM 2010 with an accel-
ular sieve was prepared from cheap PAL as silicon and erating voltage of 200 kV. The N2 adsorption-desorp-
alumina source through a two-step crystallization pro-
cess. The products prepared in different crystallization
stage were characterized by using various means and
tested in the acetalization of cyclohexanone and ester-
ification of acetic acid and n-butanol.
tion isotherms and textural properties of the samples
were recorded with a Micromeritics TriStar II 3020 at
77 K. The samples were outgassed at 300°C for 3 h in
N2 atmosphere before the measurements. The total
surface area (SBET) was calculated by the standard
BET method. The total pore volume (Vtot) was calcu-
lated from the desorption branch of the isotherm at
P/P0 = 0.99, assuming complete pore saturation. The
micropore volume (Vmicro) and micropore surface area
(Smicro) were evaluated by the t-plot method. Meso-
pore volume (Vmeso) was calculated by subtracting
micropore volume from total volume. FT-IR spectra
of the samples were collected on a Nicolet 5700 spec-
trometer with a resolution of 4 cm–1. Temperature pro-
grammed desorption of ammonia (NH3-TPD) was
performed on a Quantachrome Chembet Pulsar
TPR/TPD instrument equipped with a thermal con-
ductivity detection (TCD). The samples (0.1 g) were
pretreated at 500°C for 2 h and then cooled down to
100°C under flowing He. A mixture of 8% NH3 in He
was then introduced to be adsorbed onto the samples
for 30 min. To remove the physical adsorbed NH3, the
He stream was passed the samples at the same tem-
perature until no more NH3 was observed in the exit
flow. The samples were then heated at 600°C at a heat-
ing rate of 10°C/min to release NH3 and the amount
of desorbed ammonia was determined by TCD.
2. EXPERIMENTAL
2.1. Synthesis of ZSM-5/MCM-41
PAL was pretreated according to the published pro-
cedure [23] in an HCl solution (3 mol/L) at 80°C for
48 h. In a typical synthesis, 3 g of acid-treated PAL was
added into 20 mL of NaOH solution (1 mol/L) and
magnetically stirred for 30 min. A solution containing
20 mL of H2O and 0.4 g of tetrapropylammonium bro-
mide (TPABr) was then slowly dropped into the PAL
solution, which was further stirred at room tempera-
ture for 24 h. The resultant mixture was heated to
180°C in a stainless steel autoclave with Teflon liner
and kept for 48 h. Then, 0.4 g of NaOH was added into
the colloidal mixture under magnetic stirring after the
autoclave was cooled down to room temperature. After
1-h stirring, 20 mL of cetyltrimethylammonium bro-
mide (CTAB) solution (10%) was added into the mix-
ture and the pH value was adjusted to 10–11 with a
diluted HCl solution (1 mol/L). The chemical com-
position of the acid-treated PAL was as follows: 0.04%
Na2O, 2.17% Al2O3, 80.66% SiO2, 0.55% K2O,
0.01% CaO, 0.01% MnO2, 0.8% TiO2, 0.21% Fe2O3,
and 0.18% MgO [23]. Thus, the molar composition of
the synthesis gel was 3 TPABr : 80.6 SiO2 : 1.36
Al2O3 : 11 CTAB : 30 Na2O : 6666 H2O. Subsequently,
the mixture was again heated at 100°C for 96 h after
1-h aging. Finally, the solid product was filtered,
washed with deionized water, and dried at 100°C for
24 h. The organic templates were removed by calcina-
tion at 550°C for 3 h. For comparison, ZSM-5 zeolite
could be obtained from the mixture prepared by
hydrothermal treatment at 180°C for 48 h.
2.3. Catalytic Evaluation
2.3.1. Acetalization of cyclohexanone. The acetal-
ization reaction of cyclohexanone with methyl alcohol
was carried out in a round-bottom flask equipped with
a condenser and magnetic stirring. The catalytic reac-
tion was performed according to the procedure and
condition in the literature [26]. The catalyst (H+ form,
50 mg) was added into a solution containing of 10 mL
methyl alcohol and 98 mg of cyclohexanone. After the
reaction mixture was stirred at 50°C for 4 h, the reac-
tion liquid was separated by centrifugation and ana-
lyzed by an Agilent 6820 gas chromatograph with a
DB-1 column. The butyl acetate was used as an inter-
nal standard.
The products were ion-exchanged with 0.2 mol/L
NH4NO3 solution at 80°C for 2 h. Then the ion-
exchanged products were filtered and dried. The above
procedure was repeated two times and H-form cata-
2.3.2. Esterification of acetic acid and n-butanol.
A typical esterification of acetic acid and n-butanol
was carried out as follows: 100 mg of catalyst, 4.77 mL
+
lysts were then obtained by calcining NH4 -form
molecular sieve at 550°C for 3 h.
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SYNTHESIS AND CATALYTIC PERFORMANCE OF ZSM-5/MCM-41
1885
ZCM-5
Quartz
c
b
a
5
10
15
20
25
30
35
40
1
2
3
4
5
6
7
8
9
10
2θ, deg
2θ, deg
Fig. 1. Wide-angle XRD patterns of the acid-treated PAL
(a), the product obtained in the first step (b), and the final
product (c).
Fig. 2. Small-angle XRD pattern of the final product.
The small-angle XRD pattern of the final product
is displayed in Fig. 2. Three distinct diffraction peaks
(100), (110), and (200) appeared in the XRD curve,
which demonstrates the presence of the hexagonally
ordered MCM-41 mesoporous structure [22]. From
the small-angle and wide-angle XRD analysis of the
final product, ZSM-5/MCM-41 composite molecu-
lar sieve with micro/mesoporous structure was suc-
cessfully synthesized from the acid-treated PAL
through a two-step crystallization process.
of acetic acid (83.3 mmol), 8.4 mL of n-butanol
(91.7 mmol) were added to a three flask equipped with
a reflux condenser and a mechanical agitator. The
reaction mixture was stirred at 120°C for 120 min. The
catalyst was separated from the resulting mixture by
centrifugation. The product was analyzed by an Agi-
lent 6820 gas chromatograph with a HP-INNO WAX
column. The cyclohexanone was used as an internal
standard.
The Si/Al ratio of the molecular sieve is an import-
ant parameter related with the catalytic properties of
the molecular sieve catalyst. Our latest studies
revealed that Al atoms in PAL could enter into the
internal framework of the synthesized zeolite and the
Si/Al molar ratio of ZSM-5 zeolite crystal was 92 [25].
Figure 3 shows the EDX analysis of two samples. It
can be seen that aluminum and silicon elements could
be observed in the EDX spectrometry of two samples.
The corresponding Si/Al ratio of ZSM-5 and ZSM-
5/MCM-41 composite was 11.65 and 7.57, respec-
tively. Due to the leaching of silicon element in the
alkali solution, the Si/Al ratios of both products were
higher than that of the acid-treated PAL (32.76) [23]
and the Si/Al ratio of the product decreased with the
increase of the alkali treatment cycle. The results indi-
cate that ZSM-5/MCM-41 composite possessed
higher aluminum content and may be beneficial to
improve the catalytic properties of catalyst [26].
3. RESULTS AND DISCUSSION
3.1. Characterization of ZSM-5/MCM-41
3.1.1. XRD and EDX analysis. Figure 1 shows the
wide-angle XRD patterns of the acid-treated PAL and
the products synthesized in different crystallization
stage. The characteristic peaks of PAL at 2θ range of
8°–10° disappeared after treatment in hot HCl solu-
tion [27]. PAL was converted into amorphous silica
and the acid-treated PAL could be used as silicon
source for the synthesis of molecular sieves [23]. The
diffraction peaks located at 2θ = 7.9°, 8.7°, 23.1°,
23.9°, and 24.4°, ascribed to the characteristic diffrac-
tion peaks of MFI-type zeolite structure [28],
appeared in the XRD curves of two products. Those
results indicate that MFI-type zeolites (ZSM-5 zeo-
lites) were obtained from the acid-treated PAL by
using TPABr as template after hydrothermal treatment
3.1.2. SEM and TEM analysis. Figure 4 shows the
at 180°C for 48 h [25]. The diffraction peaks of ZSM-5 SEM images of the products synthesized in different
zeolites remained in the final product and its intensity crystallization stage. The acid-treated PAL remained
became weaker after recrystallization of the mixture the fiber morphology derived from PAL after acid
obtained in the first crystallization stage by adding treatment (the results not shown here) [23, 25]. The
CTAB as template. The results demonstrate that par- acid-treated PAL was continually dissolved in the
tial ZSM-5 zeolite crystals might be destroyed in the alkali solution and provided the silicon nutrition for
alkali solution at the secondary crystallization stage the growth of zeolite during the hydrothermal treat-
and used as silicon source of molecular sieve [15, 16]. ment process. Therefore, ZSM-5 zeolite obtained
It is noted that the diffraction peaks of quartz from raw from fibrous acid-treated PAL in the first crystalliza-
material still existed in the final product because of the tion stage exhibited round shape or coffin shape and
stability of quartz for acid and alkali solution.
the particle size of crystals was about 4–6 μm. After
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JINLONG JIANG et al.
Si
Au
4 μm
4 μm
O
(а)
(b)
(d)
Al
Na
b
K
K Ca
a
Mg
0
2
4
6
8
10
Energy, keV
100 nm
50 nm
(c)
Fig. 3. Energy dispersive X-ray spectrometry of ZSM-5 (a)
and ZSM-5/MCM-41 composite (b).
Fig. 4. SEM (a, b) and TEM (c, d) images of ZSM-5 (a)
and ZSM-5/MCM-41 composite (b–d).
the secondary crystallization, the grain size of solid
particles increased and irregular nano-sized particles
appeared in the surface of ZSM-5 zeolite crystals.
From the XRD analysis, the nano-sized particles were
MCM-41 molecular sieve phase.
isotherm of ZSM-5/MCM-41 composite was typical
of type IV, which was characteristic of MCM-41 mes-
oporous materials with one-dimensional cylindrical
channels [21], and that indicated the existence of mes-
opores. A sharp inflection at P/P0 = 0.3–0.4 was
clearly observed in the ZSM-5/MCM-41 composite
isotherm, which suggested uniformity of the mesopore
channels. Furthermore, a hysteresis loop could be
observed from the ZSM-5/MCM-41 composite iso-
therm at relative pressure above 0.9, which might be
related to condensation in textural porosity [22]. The
nitrogen adsorption of ZSM-5/MCM-41 composite
was also significantly higher than that of ZSM-5.
Table 1 shows the texture properties of ZSM-5 and
ZSM-5/MCM-41 composite. Compared with the as-
synthesized ZSM-5, ZSM-5/MCM-41 composite
possessed higher specific surface area, total and mes-
opore volume, however, micropore surface area and
volume of ZSM-5/MCM-41 composite decreased
because of the partial destroy of ZSM-5 crystals in the
alkali synthesis solution. The results indicate that the
formation of MCM-41 in the composite could effec-
tively increase specific surface area, total and meso-
pore volume, which may improve the adsorption and
catalytic properties of the composite.
Figure 4 also displays the TEM images of ZSM-
5/MCM-41 composite. After two-step crystallization
process, the TEM image of the final product reveals
that coffin shaped crystals were existed in the product,
which is similar to the shape of ZSM-5 synthesized
from the cupola slag appeared in the composite [29].
Combined with the XRD analysis result, the coffin
shaped crystals can be identified as ZSM-5 zeolites. In
addition, mesoporous framework of regular order hex-
agonal arrays, which confirmed the mesoporous
MCM-41 structure [21], could be observed and firmly
attached to the coffin-shaped ZSM-5 zeolite crystal.
The results further confirm the formation of
micro/mesoporous structure in the composite and
indicate that mesoporous phase was in situ coated on
the surface of ZSM-5 zeolite crystals in the process of
hydrothermal treatment.
3.1.3. N2 adsorption and desorption. Figure 5 shows
the N2 adsorption-desorption isotherms of the as-syn-
thesized ZSM-5 and ZSM-5/MCM-41 composite.
The as-synthesized ZSM-5 exhibited a representative
type I isotherm according to the IUPAC classifica-
tion, which was characteristic of microporous materi-
als [16]. In contrast, the N2 adsorption-desorption
3.1.4. FT-IR spectra analysis. The IR spectra of the
acid-treated PAL, ZSM-5, and ZSM-5/MCM-41
composite are shown in Fig. 6. Two bands at 796 and
1090 cm–1, ascribed to the symmetrical and asymmet-
rical stretching vibration of Si–O–Si [23], respec-
tively, appeared in all IR spectra of samples. The
strong band at 454 cm–1 of ZSM-5 and ZSM-
5/MCM-41 composite was due to the tetrahedral Si–
O bending mode [21]. However, the band at 454 cm–1
of the acid-treated PAL was shifted to higher wave
numbers. These features were characteristics of any
silica-containing materials. Compared to the acid-
treated PAL, there were two new bands at 546 and
Table 1. Texture properties of ZSM-5 and ZSM-5/MCM-41
composite
SBET Smicro Vtot
(m2/g) (m2/g) (cm3/g) (cm3/g) (cm3/g)
Vmicro Vmeso
Sample
ZSM-5
ZSM-5/MCM-41 323
266
124 0.149 0.057 0.092
116 0.272 0.052 0.220
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SYNTHESIS AND CATALYTIC PERFORMANCE OF ZSM-5/MCM-41
1887
200
180
160
140
120
100
80
c
ZSM-5
ZSM-5/MCM-41
b
b
a
a
60
0
500
1000
1500
2000
2500
3000
0.2
0.4
0.6
0.8
1.0
Wavenumber, cm−1
P/P0
Fig. 6. FT-IR spectra of the acid-treated PAL (a), ZSM-5
(b), and ZSM-5/MCM-41 composite (c).
Fig. 5. N adsorption-desorption isotherms of ZSM-5 (a)
2
and ZSM-5/MCM-41 composite (b).
3.2. Catalytic Properties
1226 cm–1 in the IR spectra of ZSM-5 and ZSM-
5/MCM-41 composite, which were due to the double-
rings tetrahedral vibration and antisymmetric stretch-
ing vibration of Si and AlO4 tetrahedra in ZSM-5 zeo-
lite framework [30], respectively.
Acetalization reaction of cyclohexanone with
methanol was carried out to verify the catalytic activity
of as-synthesized ZSM-5 and ZSM-5/MCM-41
composite. The results are listed in Table 3. The con-
version yield of cyclohexanone on ZSM-5/MCM-41
composite reached to 87.07%, significantly higher
than that of ZSM-5 (76.29%), close to that of meso-
porous ZSM-5 (87.3%) and higher than commercial
ZSM-5 (85.0%) at the same reaction conditions [26].
The latter mesoporous ZSM-5 and commercial ZSM-
5 were prepared by using expensive tetraethoxysilane
(TEOS) as silicon source and possessed smaller crys-
tallite size (200–300 nm) [26]. The introduction of
mesopores in the catalyst could effectively increase the
conversion of cyclohexanone for favorable access of
the reactants to the active sites [26, 32]. Na et al. [33]
measured the pyridine and 2,4,6-trimethyl pyridine
adsorbed IR spectra of ZSM-5 and ZSM-5/MCM-41
composite and their results indicated that ZSM-
5/MCM-41 composite exhibited higher accessibility
of acid sites compared to ZSM-5. Therefore, com-
pared to ZSM-5, the high acid site accessibility and
diffusivity of ZSM-5/MCM-41 composite resulted in
higher catalytic performance for the acetalization
reaction of cyclohexanone. In addition, the conver-
sion yield of ZSM-5/MCM-41 composite was also
higher than that of Al-MCM-41 (76.2%) for its strong
3.1.5. NH3-TPD analysis. Acid distributions of
HZSM-5 and HZSM-5/MCM-41 composite were
investigated by NH3-TPD method. As shown in Fig. 7,
two peaks appeared in the NH3 desorption curves of
all samples. Low temperature (100–350°C) desorp-
tion peak displayed weak adsorption acid sites, and the
peak at high temperature (400–550°C) was ascribed to
the interaction of NH3 with strong acid sites [26]. It
can be seen that the profile of HZSM-5/MCM-41
composite in high temperature range was similar to
that of HZSM-5 and the strong acid sites were similar
to that of HZSM-5. However, the amount of NH3
desorbed from HZSM-5/MCM-41 composite in low
temperature range was significantly higher than that of
HZSM-5, revealing the higher concentration of weak
acid sites in HZSM-5/MCM-41 composite and the
presence of Al atoms in the MCM-41 mesoporous
phase. The results also illustrate that Al species dis-
solved during alkali treatment of ZSM-5 [31] and PAL
could incorporate into the framework of MCM-41
during recrystallization process. The corresponding
acidic properties were shown in Table 2. It can be seen
that the strong acid sites of HZSM-/MCM-41 com-
posite (0.117 mmol/g) was slightly higher than that of
HZSM-5 (0.101 mmol/g). However, its total acid
amount and weak acid sites were remarkably higher
than that of HZSM-5, which was caused by the intro-
duction of MCM-41 molecular sieve and higher alu-
minum content of the composite. Compared with as-
synthesized ZSM-5 zeolites, ZSM-5/MCM-41 com-
posite may possess higher catalytic activity for the
acid-catalytic reaction because of its stronger acid
activity.
Table 2. Acidity properties of HZSM-5 and HZSM-
5/MCM-41 composite
Acidity (mmol/g)
Sample
total acid weak acid strong acid
amount
sites
sites
HZSM-5
HZSM-5/MCM-41
0.747
1.508
0.646
1.392
0.101
0.117
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JINLONG JIANG et al.
90
85
80
75
70
65
60
55
50
45
b
a
100
200
300
400
500
600
T, °C
Fig. 7. NH -TPD of HZSM-5 (a) and HZSM-5/MCM-41 composite (b).
3
acid activity inherited from ZSM-5 zeolite [32]. On In the esterification reaction, the acidity and pore
other hand, the selectivity of 1,1-dimethoxycyclohex- structure properties of catalysts play a decisive role in
ane on ZSM-5/MCM-41 composite was 96.83% and the reaction conversion [36]. The esterification of ace-
similar to that of ZSM-5 (96.38%), also higher than tic acid with n-butanol was primarily catalyzed by the
that of mesoporous ZSM-5 and commercial ZSM-5 weak and medium strength acidic sites when two cata-
(ca. 92%) [26]. Similar selectivity of two products was lysts possessed the similar nature [34, 35, 37]. Fur-
attributed to the similar environment in zeolites for all thermore, the high surface area and large pore volume
aluminum atoms were 4-coordinate state in the ZSM- of the catalyst was beneficial to increasing its catalytic
5 zeolite framework [26]. Thus, alkali treatment of performance [37]. Thus, the high catalytic perfor-
ZSM-5 and then recrystallization process had no mance of HZSM-5/MCM-41 composite was derived
influence of the incorporation state of aluminum spe- from its high acid activity, the abundant weak acid sites
cies in the zeolite framework. The same results were and easy accessibility to acid sites compared to
also found by Na and co-worker [33]. Those results HZSM-5 and Al-MCM-41. The result suggests that
illustrate that micro/mesoporous composite structure ZSM-5/MCM-41 composite may have potential
could effectively increase the catalytic activity of the application in the esterification reaction.
composite because of the synergistic effects of zeolitic
and mesoporous phases in the composite.
Table 3 also exhibits the conversion yield of acetic
acid on different catalysts. The esterification reaction
4. CONCLUSIONS
In summary, ZSM-5/MCM-41 composite molec-
possessed good ester selectivity for the two catalysts. ular sieve was successfully synthesized from low-cost
However, the conversion yield of acetic acid catalyzed PAL through a two-step crystallization process. In the
by HZSM-5/MCM-41 composite was 75.52% and first crystallization stage, ZSM-5 crystals were
significantly higher than that of HZSM-5 (59.10%). obtained from the acid-treated PAL by using TPABr as
The result is higher than the conversion of Al-MCM- the template. Subsequently, the composite containing
41 with Si/Al molar ratio of 25 (60%) and HZSM-5 mesoporous MCM-41 and microporous ZSM-5 zeo-
with Si/Al molar ratio of 15 (42.7%) [34, 35], indicat- lite could be synthesized under hydrothermal condi-
ing that the HZSM-5/MCM-41 composite possessed tion after addition of NaOH and CTAB template. Due
good catalytic property for the esterification reaction. to the presence of MCM-41, the composite could
Table 3. Catalytic properties of HZSM-5 and HZSM-5/MCM-41 composite
Acetalization reaction
Esterification reaction
ester selectivity
Sample
cyclohexanone 1,1-dimethoxycyclohexane acetic acid conversion
conversion (%)
selectivity (%)
(%)
(%)
HZSM-5
HZSM-5/MCM-41
76.29
87.07
96.38
96.83
59.10
75.52
100
100
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 91
No. 10
2017

SYNTHESIS AND CATALYTIC PERFORMANCE OF ZSM-5/MCM-41
1889
14. L. Wang, T. Dou, Y. P. Li, X. F. Li, and Z. C. Yan,
improve the diffusion rate of reactants and possessed
higher total acid amount and more weak acid sites
compared to ZSM-5. As a result, the ZSM-5/MCM-
41 composite exhibited higher catalytic activity for
acetalization of cyclohexanone and esterification of
acetic acid and n-butanol. The ZSM-5/MCM-41
composite molecular sieve synthesized from PAL with
high acidity may be a potential catalyst for the esterifi-
cation, alkylation, and condensation reaction, etc.
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ACKNOWLEDGMENTS
This work was supported by the National Natural
Science Foundation of China (51574130), State Key
Laboratory of Materials-Oriented Chemical Engi-
neering (no. KL14-14), Key Laboratory for Palygor-
skite Science and Applied Technology of Jiangsu
Province (HPK201303), Qing Lan Project of Jiangsu
Province and Jiangsu Provincial Engineering Labora-
tory for Advanced Materials of Salt Chemical Industry
(SF201303).
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