G Model
CATTOD-9681; No. of Pages6
ARTICLE IN PRESS
2
X. Zheng et al. / Catalysis Today xxx (2015) xxx–xxx
2. Experimental
2.1. Material synthesis
a
b
c
A
Cu-containing zeolite Beta nanoparticle (Cu-Beta-Nano)
was synthesized from self-assembly of aluminosilicate gel with
tetraethylammonium hydroxide (TEAOH) as template. The
a
molar ratio of compositions was 1Al2O3/2Na2O/0.36CuO/6.7SiO2/
14TEAOH/667H2O. Typically, 0.39 g NaOH and 0.65 g NaAlO2 was
dissolved in 30 mL H2O followed by addition of 26 mL TEAOH, 9.6 g
of silica gel and 1.8 g of Beta zeolite seeds. After stirring at room
temperature for 2 h, 0.38 g Cu(NO3)2·3H2O was then introduced
and the mixture was stirred for another 1 h, the obtained alu-
minosilicate gel was transferred into Teflon-coated stainless-steel
autoclave for crystallization at 140 ◦C for 6 days. The resultant prod-
uct was filtered, washed, dried at 120 ◦C overnight and calcined in
air at 550 ◦C for 5 h.
d
10
20
30
40
50
2 Theta (degree)
Fig. 1. XRD patterns of the (a) Cu-Beta-Nano, (b) Cu-Beta-B, (c) Beta-Nano and (d)
The Cu-containing bulky zeolite Beta (Cu-Beta-B) was synthe-
sized from a starting aluminosilicate gel with a molar ratio of
1Al2O3/10Na2O/0.36CuO/40SiO2/570H2O. 0.25 g NaAlO2 and 0.71 g
NaOH was dissolved in 10 mL H2O followed by addition of 2.5 g of
fumed silica and 0.4 g of Beta zeolite seeds. After stirring at room
temperature for 4 h, 0.09 g Cu(NO3)2·3H2O was then introduced
and further stirred for another 1 h, the obtained gel was transferred
into Teflon-coated stainless-steel autoclave for crystallization at
140 ◦C for 40 h. The resultant product was filtered, washed, dried at
120 ◦C overnight and calcined in air at 550 ◦C for 5 h. For compar-
ison, the zeolite Beta nanoparticles (Beta-Nano) were synthesized
by the same procedure except for the absence of metal precursor.
The Beta-Nano supported copper catalyst (Cu-Beta-Nano-IM) was
prepared by incipient wetness impregnation of the cupric nitrate
solution with Beta-Nano. The Beta-Nano supported copper cata-
lyst (Cu-Beta-Nano-IE) was also prepared by ion-exchange with
a cupric nitrate solution. After impregnation or ion-exchange, the
samples were exposed under ambient conditions for 20 h, and fur-
ther dried at 120 ◦C for 12 h and calcined in air at 550 ◦C for 5 h.
The copper contents in the calcined Cu-Beta-Nano, Cu-Beta-B, Cu-
Beta-Nano-IM and Cu-Beta-Nano-IE samples were 2.0, 1.9, 2.1 and
1.9 wt.%, respectively, which was determined by the inductively
coupled plasma optical emission spectroscopy (ICP-OES) with a
Perkin-Elmer 3300DV emission spectrometer.
the reused Cu-Beta-Nano samples.
Micromeritics ASAP2920 instrument. 200 mg of sample was placed
in a quartz tube and pretreated in a helium stream at 500 ◦C for 3 h.
After the sample was cooled to 120 ◦C, NH3–He mixed gas (10 vol%
NH3) was passed over the sample for 40 min. After removal of the
physically adsorbed NH3 by flowing helium for 3 h at 120 ◦C, the
sample was treated from 120 to 800 ◦C at a rate of 10 ◦C min−1
.
2.3. Catalytic testing
In a typical run, a mixture of diphenyl disulfide (0.2 mmol), p-
tolualdehyde (2.0 mmol), K2CO3 (0.4 mmol), tert-butyl hydroper-
oxide (TBHP) (0.6 mmol), catalyst (40 mg), H2O (2.0 mL) was stirred
at desired temperature for 2 h. After the reaction was completed,
the mixture was cooled down to room temperature and then
extracted with ethyl acetate. The organic phase was analyzed on an
Agilent 7890A GC equipped with a FID detector and mass spectrom-
eter. The product was purified by column chromatography on silica
gel (200–300 mesh) (eluent: petroleum ether and ethyl acetate).
The obtained product was identified by NMR spectra using a Bruker
500 MHz spectrometer instrument. The 1H NMR (500 MHz) and 13
C
NMR (125 MHz) were recorded with spectrometers at 20 ◦C using
CDCl3 as the solvent. Chemical shifts are given in parts per million
relative to TMS as the internal standard at room temperature. The
2.2. Characterization
X-ray diffraction (XRD) data were collected on a RIGAKU
UltimalV diffractometer using Cu K␣ radiation. Nitrogen
adsorption–desorption isotherms were measured on a Micro-
meritics ASAP 2020 M apparatus. The sample was degassed for 5 h
at 350 ◦C before the measurement. Specific surface area was calcu-
lated from the adsorption data, using the Brunauer–Emmett–Teller
(BET) equation. Scanning electron microscopy (SEM) image
was obtained on a SURPA55 apparatus. Transmission electron
microscopy (TEM) experiment was performed on a JEM-2100F
3. Results and discussion
Fig. 1 shows the XRD patterns of the Cu-Beta-Nano, Cu-Beta-
B, Beta-Nano and reused Cu-Beta-Nano samples, exhibiting typical
results show that the copper content in the Cu-Beta-Nano and Cu-
Beta-B is 2.0 and 1.9 wt.%, respectively, suggesting that the copper
Fig. 2 shows the SEM and TEM images of Cu-Beta-Nano and Cu-
In contrast, the Cu-Beta-B sample shows large particle with sizes
about 1 m (Fig. 2c). It is worth noting that the copper particles
observed in the TEM images (Fig. 2b and d), while the Cu content in
the two samples is 2.0 and 1.9 wt.% determined from ICP analysis,
which indicates that the Cu species could be highly dispersed into
the zeolite structure. Sample textual parameters are presented in
Table 1.
˚
microscope with a limited line resolution capacity of 1.4 A, under a
voltage of 200 kV. Before characterization by TEM, the sample was
dispersed in alcohol and dropped on a Cu-grid coated with carbon
membrane. X-ray photoelectron spectroscopic (XPS) experiment
was performed on an ESCALAB MK II system. UV–vis diffuse
reflectance spectra (UV–vis DRS) were recorded in Perkin-Elmer
Lambda 25 spectrometer with an integration sphere. BaSO4 was
used as a reference sample to measure the baseline spectrum.
The Cu contents and the ratio of Si/Al in the zeolite catalyst were
determined by the inductively coupled plasma optical emission
spectroscopy (ICP-OES) with a Perkin-Elmer 3300DV emission
spectrometer. The acidity of the catalysts was measured using
temperature-programmed desorption of ammonia (NH3-TPD) on a
To investigate the state of Cu species in the zeolite cata-
lysts, the UV–vis diffuse reflectance spectroscopy (UV–vis DRS)
Please cite this article in press as: X. Zheng, et al., Zeolite Beta nanoparticles assembled Cu catalysts with superior
catalytic performances in the synthesis of thioesters by cross-coupling of aldehydes and disulfides, Catal. Today (2015),