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Y. Zhang et al. / Applied Catalysis A: General 522 (2016) 45–53
The Cu9.9/HZSM-5 catalyst was prepared by the impregnation
method. 7.6 g of Cu(NO3)2·3H2O was dissolved in 10.4 g of water,
and then 18 g of HZSM-5 with a diameter of 2 mm and a length of
2.5 mm was introduced into the solution. The mixture was vigor-
ously stirred at room temperature for 48 h and then dried at 110 ◦C
for 6 h and calcined at 550 ◦C for 6 h to obtain the catalyst.
through the amination—dehydrogenation of corresponding alco-
hols [23,27–29] over a CoNi/␥-Al2O3 catalyst; we also succeeded
in obtaining a ZnCr/␥-Al2O3 catalyst being active in the synthesis
of phenylacetonitrile [30] and propionitrile [31] from styrene oxide
and allyl alcohol through the amination—dehydrogenation, respec-
tively. Based on the CoNi/␥-Al2O3 catalyst and the parameters
obtained in laboratory, acetonitrile can be produced on a pilot scale
from ethanol by us. Encouraged by the results we are engaged in
the synthesis of benzonitrile from the amination-dehydrogenation
of benzyl alcohol. A series of catalysts have been prepared and it
has been found that a Cu10.3/SiO2 catalyst is very efficient in the
conversion of benzyl alcohol to benzonitrile. Herein, we report the
results.
2.2. Catalyst characterization
The metal content of the catalyst samples was determined by a
Perkin Elmer Opfima 7300 V type ICP-AES instrument. Before anal-
ysis, the accurately weighed sample was carefully added in a flask,
and then aqua regia (HNO3–HCl) and HF were added successively
to dissolve the sample. The obtained solution was subjected for
analysis.
The X-ray diffraction (XRD) patterns of the samples were
recorded with a Bruker AXS GMBH D8 FOCUS X-ray diffractome-
ter using Cu K␣ radiation (40 kV, 40 mA) in the range 2 = 10–90◦.
Transmission electron microscopy (TEM) was performed using a
using a JEM 2100F instrument which was equipped with an energy
dispersive X-ray (EDX) detector at an accelerating voltage of 200 kV.
The specimens for TEM analysis were prepared by ultrasonic dis-
persion in ethanol, and then a drop of the resultant suspension was
evaporated on a lacey carbon/Mo grid.
2. Experimental
2.1. Catalyst preparation
The metal nitrates Cu(NO3)2·3H2O (99%), Fe(NO3)2·9H2O
(98.5%),
Co(NO3)2·6H2O
(99%),
Ni(NO3)2·6H2O
(98%),
Zn(NO3)2·6H2O (99%), Cr(NO3)3·9H2O (99%), Ca(NO3)2·4H2O
(99%), Na2SiO3·9H2O (Na2O 22.8-23.5%, Na2O: SiO2 = 1.03) and
other reagents used for preparation of the catalysts were obtained
from KRS Chemical Reagent Cooperation, Tianjin, China. The
mordenite, H-ZSM-5 and sodium bentonite were acquired from
Nankai University Catalyst Plant, Tianjin, China. TiO2 and ␥-Al2O3
were obtained from the Tianjin Research and Design Institute of
Chemical Industry, Tianjin, China.
The surface areas, total pore volumes and pore sizes of the
samples were measured at 77 K by nitrogen adsorption using a
Micromeritics ASAP 2020 M + C Surface Area and Porosity Analyzer.
The IR spectra of adsorbed pyridine were recorded by a Thermo
Electron Corporation Nicolet Nexus 470 spectrometer equipped
with a heatable and evacuatable IR cell with CaF2 windows con-
nected to a gas dosing-evacuation system. The powdered samples
were pressed into self-supporting wafers with a diameter of 20 mm
and weight of 15 mg. Prior to analysis, all samples were pretreated
at 400 ◦C for 1 h under high vacuum conditions (1 × 10−5 Pa), fol-
lowed by cooling to 200 ◦C. Then pyridine was adsorbed at this
temperature for 15 min. The physisorbed pyridine was removed
by evacuating at 200 ◦C for 15 min under high vacuum conditions
(1 × 10−5 Pa). Then the infrared spectra were recorded.
Series of catalysts with different metal contents on various sup-
ports were prepared, which was denoted as Mx/S, where M, x and
S represent the type of transition metal, the metal content in the
catalyst and the type of support, respectively. Thus, the Cu/SiO2
catalysts were denoted as Cux/SiO2, where x represents the copper
content in the catalyst.
H2SiO3 was employed as the precursor of SiO2 and prepared
as follows: 85.09 g of Na2SiO3·9H2O was dissolved in 198.55 g of
distilled water, then 30% (v/v) nitric acid was dropped slowly into
this solution under mechanical stirring at 40 ◦C until the pH reached
5. The reaction mixture was stirred for 1 h, then filtered, and the
solid was washed with distilled water thoroughly until the pH of
the filtrate reached 7. Then the solid was dried at 110 ◦C for 3 h to
obtain the H2SiO3.
Thermogravimetric-different scanning calorimetry (TG-DSC)
measurement was carried out with a DuPont TA2000 thermogravi-
metric analyser from 20 to 800 ◦C with a rate of 10 ◦C min−1 under
air atmosphere. The air flow rate was controlled at 100 ml/min.
2.3. Catalytic tests
The Cu/SiO2 catalysts were prepared by kneading a mixture of
H2SiO3 with an aqueous solution of the corresponding transition-
metal nitrates, then extruded, dried and calcined. As an example,
the Cu10.3/SiO2 catalyst was prepared as the following procedures:
7.6 g of Cu(NO3)2·3H2O was added in a beaker, and a suitable
amount of distilled water was added to dissolve the nitrate, then
23.37 g of H2SiO3 was added to the solution. The mixture was
kneaded for 3 h in a kneader and the resulting kneaded material
was processed in an extruder to obtain extrudates with a diameter
of 2 mm and a length of 2.5 mm. The catalyst precursor was dried
at 110 ◦C for 6 h and calcined at 550 ◦C for 6 h to yield the catalyst.
The catalysts with supports except for SiO2 and HZSM-5 were
prepared by the impregnation- kneading-extruding method. As an
example, the Cu10.2/␥-Al2O3 catalyst was prepared as the following
procedures: 7.6 g of Cu(NO3)2·3H2O was added in a beaker, and a
suitable amount of distilled water was added to dissolve the nitrate,
then 18 g of ␥-Al2O3 was added to the solution. The mixture was
kneaded for 3 h in a kneader and the resulting kneaded material
was processed in an extruder to obtain extrudates with a diameter
of 2 mm and a length of 2.5 mm. The catalyst precursor was dried
at 110 ◦C for 6 h and calcined at 550 ◦C for 6 h to yield the catalyst.
The catalytic experiments were performed in a continuous
fixed-bed reactor (i.d. = 15 mm; length = 700 mm) which was placed
in an electric furnace consisting of four heating zones equipped
with four temperature controllers. The thermocouple was placed
in the center of the catalyst bed to measure the temperature in the
catalyst zone. The benzyl alcohol with a rate of 0.05 ml/min was
pumped into the reactor by a syringe pump, and the flow of ammo-
nia was controlled by a PID cascade controller to keep the flow rate
as required. In the experiment, 15 ml of the catalyst sample was
charged into the middle section of the reactor to create a catalyst
zone of approximately 85 mm, and the catalyst zone was heated
to the desired temperature. Controlled flows of benzyl alcohol and
ammonia were passed separately into a vaporizer (approximately
205 ◦C) in which the two reactants were preheated, vaporized and
mixed perfectly. The products were collected in a condenser, then
the liquid products were separated in a gas-liquid separator, and
the gaseous products generated were absorbed by passing through
a flask filled with a solution of sulfuric acid to remove the low boil-
ing point compounds and unreacted ammonia. A GC–MS (HP5971
GC–MS) equipped with a 30 m SE-30 capillary column was used to
identify the collected products.