Zeolite y nanoparticle assemblies with high activity in the direct hydration of terminal alkynes

Article abstract of DOI:10.1039/c6ra11489j

A strong acidic zeolite Y nanoparticle assembly (HNANO-Y) with a micro-meso-macroporous structure was synthesized and used as a highly efficient heterogeneous catalyst for the hydration of alkynes to prepare ketone compounds, as compared to acidic mesoporous zeolite ZSM-5 and Beta catalysts. This feature should be assigned to the fact that the micro-meso-macroporous structure in the HNANO-Y benefits mass transfer and the strongly acidic sites on HNANO-Y facilitate alkyne hydration activity. The catalyst can be reused six times without loss of activity.

Full text of DOI:10.1039/c6ra11489j

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Zeolite Y nanoparticle assemblies with high activity
in the direct hydration of terminal alkynes†
Cite this: RSC Adv., 2016, 6, 69822
ab
a
b
b
b
b
Shuling Xu, Zhi Yun,* Yu Feng, Ting Tang, Zhongxue Fang and Tiandi Tang*
A strong acidic zeolite Y nanoparticle assembly (HNANO-Y) with a micro–meso–macroporous structure
was synthesized and used as a highly efficient heterogeneous catalyst for the hydration of alkynes to
prepare ketone compounds, as compared to acidic mesoporous zeolite ZSM-5 and Beta catalysts. This
feature should be assigned to the fact that the micro–meso–macroporous structure in the HNANO-Y
benefits mass transfer and the strongly acidic sites on HNANO-Y facilitate alkyne hydration activity. The
catalyst can be reused six times without loss of activity.
Received 4th May 2016
Accepted 7th July 2016
DOI: 10.1039/c6ra11489j
www.rsc.org/advances
work focuses on developing high efficient heterogeneous catalysts
1
. Introduction
33–37
for organic synthesis,
in this work, we synthesized for the rst
Catalytic hydration of C–C triple bond provides a perfect and time nanoparticle assemblies of zeolite Y (NANO-Y) that presents
environmentally benign approach for the preparation of carbonyl good crystallinity and has a large external surface area by addition
1–3
compounds with 100% atomic efficiency. For instance, ketones of the silane ([(CH O) SiC H N(C H ) C H33]Cl) into the zeolite Y
3 3 3 6 2 5 2 16
are important structural motifs in modern organic synthesis that synthesis gel. Meanwhile, the microporous zeolite Y, and meso-
can be efficiently synthesized by Markovnikov hydration of porous zeolites ZSM-5 and Beta (ZSM-5-M and Beta-M) were also
alkynes over Hg(II) salts combining with acids in industrial synthesized. Aer transforming zeolites to the H-form by ion-
4–7
processes. However, these catalytic systems always suffer from exchange in NH
4 3
NO solution, the obtained samples were deno-
the high toxicity of mercury. Although many transition metal ted as HNANO-Y, HY, HZSM-5-M and HBeta-M. Compared with
8
,9
10,11
12,13
14,15
16,17
18–20
21,22
catalysts such as Ru, Rh,
Co
Pd,
Pt,
Ag,
Au,
Fe,
HY, HZSM-5-M and HBeta-M, HNANO-Y exhibits high activity in
23,24
25
and Ir have been widely attempted for this reaction alkyne hydration reactions.
process, these catalytic systems suffered from lower reactivity,
recovery and reusage of the catalysts. Despite the concentrated
solution of strong acids being extensively investigated, and 2. Experimental
exhibiting high activity for promotion of the alkyne hydration
2
.1 Material synthesis
26–28
process,
these catalytic systems always needed a large excess
Zeolite Y nanoparticle assemblies (NANO-Y) were synthesized
from an aluminosilicate gel with molar ratios of 1.0Al O /
amount of acidic reagents and are unsuitable industrial
applications.
2
3
4
.4Na
of N,N-diethyl-N-cetyl-N-(3-trimethoxysilylpropyl) ammonium
chloride ([(CH O) SiC N(C 33]Cl). In a typical run,
8.7 mL of waterglass, 3.0 mL of H O, and 2.81 mL of zeolite Y
seed solution (1.409 g NaAlO , 12.7 mL H O, 5.12 g NaOH and
6.8 mL waterglass were mixed and aged for 24–36 h) were
2 2 2
O/9.8SiO /0.8TMOAC/153H O, where TMOAC is a silane
To solve these problems, in recent years, recyclable and
recoverable heterogeneous catalysts, such as polystyrene sup-
ported sulfonic acid, Au modied mesoporous silica, silver
exchanged silicotungstic acid (AgSTA) and Sn–W mixed oxide
3
3
3
H
6
2 5 2 16
H ) C H
1
2
29–31
2
2
have been used for this process.
Although these catalysts
1
showed high efficiency, mineral acid was required as a co-catalyst.
More recently, conventional micropore zeolites such as Beta,
ZSM-5 and MOR as acidic catalysts were applied for these alkyne
mixed. Aer further stirring for 180 min, 5.75 mL of an Al (SO )
aqueous solution (45.6 wt%), and 5.95 mL aqueous solution of
NaAlO (18.2 wt%) and NaOH (9.2 wt%) were added. Aer stir-
2
ring at room temperature for 120 min, the obtained alumino-
silicate gel was transferred into a Teon-coated stainless-steel
autoclave for static crystallization at 90 C for 2 days. Aer l-
trating and washing, the sample was dried at 120 C overnight
and calcined in air at 560 C for 4 h. The microporous zeolite Y
2
4 3
32
hydration reactions. However, the main drawback is that the
relatively small pores in the zeolite crystals strongly limited
molecular diffusion and bulk molecule conversion. As continuous
ꢀ
ꢀ
a
College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing,
ꢀ
Jiangsu 210009, P. R. China. E-mail: yunzhi@njtech.edu.cn
was also synthesized by similar procedures in the absence of the
TMOAC. The mesoporous zeolite ZSM-5 and Beta (ZSM-5-M and
Beta-M) were synthesized according to previous work proce-
b
School of Petrochemical Engineering, Changzhou University, Changzhou, Jiangsu
2
†
1
13164, P. R. China. E-mail: tangtiandi@wzu.edu.cn
Electronic supplementary information (ESI) available. See DOI:
0.1039/c6ra11489j
38,39
dures.
The mesoporous-free Beta and ZSM-5 were prepared
69822 | RSC Adv., 2016, 6, 69822–69827
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37,38
according to the procedure reported in our precious work.
HNANO-Y catalyst, 50 mmol 1-ethynyl-4-methoxybenzene and
The H-form of the zeolite samples were obtained by ion- 150 mL water were placed into an autoclave. The reaction
ꢀ
ꢀ
exchanging twice with NH NO solution (1 M) at 80 C for 4 h, temperature was 80 C, reaction time was 12 h, and stirring rate
4
3
ꢀ
followed by calcination at 550 C for 4 h, and were denoted as was 500 rpm. For the catalyst recycling experiment, once the
HNANO-Y, HY, HZSM-5-M, HBeta-M, HBeta and HZSM-5.
reaction was nished, the solid catalyst was separated by
centrifugation, and washed with 5 mL of acetone. The washing/
centrifugation sequence was repeated three additional times.
Finally, the obtained catalyst was dried under vacuum and
reused for the next run.
2.2 Catalyst characterization
X-ray powder diffraction (XRD) analysis was conducted on
a Rigaku Smart Lab diffractometer, using Cu Ka radiation.
Nitrogen adsorption–desorption isotherms were obtained using
a Micromeritics ASAP2020M apparatus at the temperature of 3. Results and discussion
ꢀ
liquid nitrogen (ꢁ196 C). Specic surface areas were calculated
3.1 Catalyst characterization
from the adsorption data, using the Brunauer–Emmett–Teller
Fig. 1a shows the XRD pattern and nitrogen sorption isotherm
of the calcined NANO-Y sample. The XRD pattern shows that
well-resolved peaks in the range of 5–50 , with a zeolite FAU
structure, can be clearly observed in NANO-Y and Y samples,
indicating the high degree of crystallinity of the two samples.
The nitrogen adsorption–desorption isotherms of the NANO-Y
exhibit a hysteresis loop at a relative pressure of 0.5–0.95,
which is typically assigned to the presence of the mesoporous
(
BET) equation. The pore size distributions were calculated
using the Barrett–Joyner–Halenda (BJH) model. Scanning elec-
tron microscopy (SEM) images were obtained on a NanoSEM200
apparatus. Transmission electron microscopy (TEM) images of
the sample were obtained on a JEM-2100 microscope with
a limited line resolution capacity of 1.4 A, under a voltage of
2
temperature-programmed desorption of ammonia (NH -TPD)
on a Micromeritics ASAP 2920 instrument. About 200 mg of
sample was placed in a quartz tubular reactor and pretreated in
a helium stream, heated to 450 C with a rate of 1 C min , and
kept at 450 C for 2 h. Aer the sample was cooled to 120 C,
NH –He mixed gas (10 vol% NH ) was passed over the sample
ꢀ
˚
00 kV. The acidity of the samples was measured using
3
(Fig. 1b). Correspondingly, the mesopore-size diameter is
mainly centered at 29.0 nm (inset, Fig. 1b). The sample texture
parameters are shown in Table 1. HNANO-Y exhibits high BET
and external surface areas and mesoporous volume (811 and
ꢀ
ꢀ
ꢁ1
ꢀ
ꢀ
2
ꢁ1
3
ꢁ1
1
58 m g , and 0.22 cm g ), which could benet the mass
3
3
transfer and provide abundant accessible acidic active sites.
for 30 min. Aer removal of physically adsorbed NH
helium for 2 h at 120 C, the sample was heated from 120 to
5
3
by owing
ꢀ
ꢀ
ꢀ
ꢁ1
00 C with a rate of 10 C min . The desorbed NH was
3
collected in dilute hydrochloric acid and titrated with a dilute
sodium hydroxide solution to determine the acidic site density
of the sample.
2.3 Reaction and analysis
All reagents, unless otherwise noted, were obtained from
commercial sources (purity > 99%) and used without further
purication. The typical experimental procedure for the alkyne
hydration reaction was as follows: 30 mg catalyst, 0.5 mmol
alkynes, 1.5 mL water were added into a 10 mL glass vessel. The
reaction proceeded at the setting temperature for the desired
time. Aer the reaction was nished, the catalyst was separated
by centrifugation and ltration to obtain the liquid phase. The
liquid products were analyzed by an Agilent 7890B gas chro-
matograph equipped with a ame ionization detector. The pure
product was obtained by ash column chromatography on
ꢀ
silica gel using petroleum ether (60–90 C) and ethyl acetate as
eluents. Compounds described in the literature were charac-
1
13
terized by comparing their H and C NMR spectra to the re-
1
13
ported data. H and C NMR spectra were recorded with
a Bruker Avance 400 spectrometer at 400 and 100 MHz,
respectively. Chemical shis (d) and coupling constants (J) are
given in ppm and Hz, respectively. The chemical shis are
recorded relative to the residual solvent as an internal standard
1
13
(
[D1] chloroform: d ¼ 7.26 ppm for H and 77.0 ppm for C).
Fig. 1 (a) XRD patterns of the Y and NANO-Y samples, and (b) N
2
The scale-up experiment was carried out in an autoclave
adsorption isotherms of the NANO-Y (inset, mesoporous size distri-
(
Parr 5500, 300 mL). The reaction mixture was as follows: 3 g bution of the NANO-Y sample).
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Table 1 Textual parameters of the various zeolite catalysts
a
2
ꢁ1
b
3
ꢁ1
c
2
ꢁ1
d
2
ꢁ1
e
3
ꢁ1
Samples
S
BET (m g
)
V
mic (cm g
)
S
ext (m g
)
S
mic (m g
)
V
mes (cm g
)
HNANO-Y
HY
HZSM-5-M
HBeta-M
HBeta
811
821
434
619
600
376
0.26
0.32
0.08
0.18
0.16
0.13
158
59
167
180
55
653
762
267
439
535
353
0.22
0.06
0.47
0.29
0.04
0.02
HZSM-5
23
a
b
c
d
e
BET surface area. Microporous volume. External surface area, including mesoporous surface area. Microporous surface area. Mesoporous
volume.
The SEM images show the zeolite Y nanoparticle assemblies
with a particle size of 0.5–1.5 mm (Fig. 2a). The high resolution
image shows that the particle is composed of nanoparticle
aggregates with a main size of 60–100 nm (Fig. 2b). In this
manner, the interstice mesopores and macropores could be
formed in aggregates. The TEM image shows the Y nano-
particles with a highly crystalline micropore structure (Fig. 2c).
The SEM, TEM, and nitrogen sorption results indicate that the
NANO-Y exhibits a micro–meso–macroporous structure, which
could benet mass transfer and improve its catalytic perfor-
ꢀ
mance. The NH
3
-TPD curves show that the weak (120–300 C)
ꢀ
and strong (300–450 C) acidic sites existed on the HNANO-Y,
HY, HZSM-5-M and HBeta-M samples (Fig. 3). However, not
only the weak acidic sites, but also the strong acidic sites on the
HNANO-Y and HY samples are much larger than those on the
HZSM-5-M and HBeta-M samples. The acid–base titration
results also show that the total acidity of the HNANO-Y is 830
ꢁ1
ꢁ1
mmol g , similar to HY (798 mmol g ), and much higher than
ꢁ
1
ꢁ1
that of HBeta-M (256 mmol g ) and HZSM-5-M (350 mmol g
samples (Table S1†).
)
3
.2 Catalyst performance
The hydration of alkynes to synthesize ketone compounds was
rstly studied by choosing 1-ethynyl-4-methoxybenzene as

a model substrate to investigate the activity of the series of
catalysts (Table 2). To our delight, the highly desired product
yield (99%) is obtained over the HNANO-Y catalyst (entry 2). The
micropore HY catalyst gives substrate conversion of 71% (entry
3), much lower than that of HNANO-Y. It should be noted that
the product is indeed formed over the HZSM-5-M and HBeta-M
catalysts with good substrate conversions (entries 4 and 5).
However, mesopore-free HZSM-5 and HBeta give low substrate
conversions of 53 and 61%, respectively (entries 6 and 7). In
addition, when the reaction was scaled-up to 100 times using
the HNANO-Y catalyst, the obtained product yield is 96% (entry
8, Table 2). The water amount in the reaction mixture on the
reaction activity was also surveyed, and the results are shown in
the Table S2.† The conversion of 1-ethynyl-4-methoxybenzene is
decreased when the mole ratio of water with reaction substrate
is lower than 4. The substrate conversion on reaction time over
HNANO-Y, HZSM-5-M and HBeta-M catalysts is shown in Fig. 4.
Fig. 2 SEM images of the NANO-Y in the low (a) and high resolution
Obviously, the substrate conversion over HNANO-Y is higher (b), and (c) TEM image of the NANO-Y sample.
than that over HBeta-M and HZSM-5-M at the same reaction
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Fig. 3 NH -TPD curves of HY, HNANO-Y, HZSM-5-M and HBeta-M
samples.
Fig. 4 Dependence of the 1-ethynyl-4-methoxybenzene conversion
on reaction time over HNANO-Y, HBeta-M and HZSM-5-M catalysts
(
0.5 mmol 1-ethynyl-4-methoxybenzene, 1.5 mL water, 30 mg
ꢀ
HNANO-Y, the reaction temperature is 80 C).
Table 2 Hydration of 1-ethynyl-4-methoxybenzene over series of
a
catalysts
This result demonstrates that the two hydrogen atoms of
product 2a at the methyl position stem from water.
(1)
Entry
Catalyst
Conversion (%)
Selectivity (%)
1
2
3
4
5
6
7
8
None
HNANO-Y
HY
HZSM-5-M
HBeta-M
HZSM-5
HBeta
—
99
71
81
88
53
61
96
—
100
100
100
100
100
100
100
The reusability of the HNANO-Y catalyst also served in
the synthesis of 4-methoxyacetophenone from 1-ethynyl-4-
methoxybenzene and the results are presented in Table 4. The
catalyst recycling experimental results show that the catalyst is
still efficient at promoting this process even aer six runs
without signicant loss in catalytic activity.
b
HNANO-Y
a
Reaction conditions: 1-ethynyl-4-methoxybenzene (0.5 mmol), water
ꢀ
b
(1.5 mL), catalyst (30 mg), 80 C for 12 h. The reaction scaled-up 100
times of entry 2 in an autoclave.
3.3 Discussion on the high activity
The high activity and broad scope of reactants over the HNANO-
Y catalyst should be attributed to the abundant acidic sites with
time. Under all conversions, the product selectivity is close to strong acidity on the HNANO-Y, and especially the micro–meso–
00% on the HNANO-Y, HBeta-M and HZSM-5-M catalysts.
macroporous structure in the HNANO-Y. The HY and HANO-Y
Table 3 shows the hydration activity of the HNANO-Y catalyst present similar acidity (Fig. 3) and BET surface area (Table 1),
1
for a series of alkynes. The reaction exhibits good tolerance but the conversion of the 1-ethynyl-4-methoxybenzene over
toward various aromatic alkynes with electron-donating and HNANO-Y (99%) is much higher than that over HY (71%) in the
electron-withdrawing groups, such as methoxy, alkyl, halogen, hydration reaction (Table 2). This is due to the presence of
nitro and phenyl at the ortho, meta or para positions, giving the meso–macroporous structure in the HNANO-Y, which could
corresponding products in moderate to excellent yields (2a–2o, favor mass transfer and improve its catalytic performance. It is
6
2
2
6–100%). Meanwhile, the alkynes bearing 2-thienyl and mentioned that the mesopore size of HBeta-M and HZSM-5-M
-pyridyl groups are compatible for this transformation (2p and are mainly centered at 10.5 and 21.8 nm (Fig. S1†), and the
q). Furthermore, the sterically hindered naphthyl-substituted mesoporous size of NANO-Y is centered at 29 nm (Fig. 1b inset).
2
ꢁ1
3
alkynes also yielded the target product 2r in 88% yield.
In addition, compared with HNANO-Y (158 m g , 0.22 cm
ꢁ1
Following this, to get further insights, an isotope labeling
g
), the HZSM-5-M and HBeta-M show large mesoporous
2
ꢁ1
experiment was also conducted. The reaction proceeded using surface areas (167 and 180 m
g
, respectively) and meso-
3
ꢁ1
deuterium oxide instead of water under the standard condi- porous volume (0.47 and 0.29 cm g , respectively, Table 1),
0
tions, giving deuterated product [D]-2a in 98% yield (eqn (1)). but the 1-ethynyl-4-methoxybenzene conversion over HNANO-Y
(99%) is higher than over HZSM-5-M (81%) and HBeta-M (88%)
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a
a
Table 3 Hydration of series alkynes over HNANO-Y catalyst
Table 4 Recyclability experiments of the HNANO-Y system
Entry
Recycle
Conversion (%)
1
2
3
4
5
6
Run 1
Run 2
Run 3
Run 4
Run 5
Run 6
99
99
98
98
97
97
a
Reaction conditions: 1-ethynyl-4-methoxybenzene (0.5 mmol), water
ꢀ
(1.5 mL), HNANO-Y (30 mg) at 80 C for 12 h.
4. Conclusions
In summary, a micro–meso–macroporous zeolite Y nano-
particle assembly (HNANO-Y) was synthesized and applied to
hydration of alkynes for the synthesis of ketone compounds.
Compared with mesoporous zeolite ZSM-5 and Beta (HZSM-5-M
and HBeta-M) catalysts, HNANO-Y shows high activity and good
compatibility with a broad range of functional groups. This
feature could be attributed to the abundant acidic sites on the
HNANO-Y that can highly effectively catalyze the alkyne hydra-
tion reaction. In addition, the meso–macroporous in the
HNANO-Y could facilitate the mass transfer and further
improve its catalytic performance. The catalyst could be recy-
cled up to six consecutive cycles without loss in activity.
Acknowledgements
This study was supported by the National Natural Science
Foundation of China (21506017 and 21476030) and the Natural
Science Foundation of Jiangsu Province of China (BK20150258).
a
Reaction conditions: alkynes (0.5 mmol), water (1.5 mL), catalyst (30
ꢀ
b
mg), 80 C for 15 h. The data outside of bracket is the product yield
obtained from GC analysis, the data inside of bracket is the isolated
yield.
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