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than are noble metals; further, their properties are well
suited for applications in reforming, hydrogenation, and
hydrotreating reactions [13–16]. Nouwen et al. [12]
claimed that the activity of supported nickel catalysts was
very high in the amination of acetone to produce MIPA.
However, the amination reaction of acetone was carried out
at very high pressure (35–200 bar). In addition, Vedage
et al. [17] demonstrated the reductive amination of 2-pro-
panol over zeolite supported potassium–cobalt catalysts at
high pressures (*17 bar) in an autoclave. However, in
batch-type reductive amination, industrial separation and
recycling of catalyst and by-product are difficult. The
reductive amination of alcohols has been widely investi-
gated. However, most of the studies focused on methanol,
ethanol, and cyclohexanol [18–20]. There are few reports
regarding the influence of reaction parameters on the
reductive amination of 2-propanol. Here, we describe the
catalytic properties of Ni/c-Al2O3 catalysts for the reduc-
tive amination of 2-propanol in the presence of ammonia
and hydrogen at atmospheric pressure. The effects of the
reaction temperature, the partial pressures of ammonia and
hydrogen, and space velocity were examined. 2-Propanol
conversions and selectivities for MIPA, acetone, diisopro-
pylamine (DIPA), and diisopropyl ether (DIPE) when using
Ni/c-Al2O3 catalysts with different nickel loadings were
compared. The calcined and reduced catalysts were
extensively characterized by X-ray diffraction (XRD),
transmission electron microscopy (TEM), H2-temperature-
programmed reduction (H2-TPR), N2-sorption, and H2-
chemisorption.
distribution was calculated from the desorption branch
using the Barrett–Joyner–Halenda (BJH) formula. The
XRD patterns were obtained on a Rigaku diffractometer
using Cu Ka radiation operating at 40 kV and 50 mA with
a scanning rate of 2° min-1 from 30 to 80°. The particle
size of metallic Ni was determined from the broadening of
the diffraction peak of the Ni (111) plane using Scherrer’s
equation. The Ni/c-Al2O3 catalysts were also characterized
by TEM (TECNAI G2 instrument). The binding energies
of nickel and nitrogen were determined by X-ray photo-
electron spectroscopy (XPS) with a VG ESCALAB 210
spectrometer employing Mg Ka X-ray source (1253.6 eV).
All the binding energies are referenced to the C 1s from
adventitious carbon.
Micromeritics AutoChem 2920 instrument was used to
perform H2-TPR experiments in order to determine the
reducibility of nickel oxides on NiO/c–Al2O3 catalysts.
Prior to the TPR studies, each catalyst was pretreated under
flowing helium (50 cm3 min-1) at 400 °C for 1 h. After
pretreatment, the sample was cooled to ambient tempera-
ture. Then, the reducing gas containing 5 % H2 in argon as
the diluent gas was passed over the samples at a flow rate
of 50 cm3 min-1 with heating at the rate of 10 °C min-1
up to 900 °C; the temperature was then kept constant for
0.5 h. The effluent gas was analyzed by a Balzers QMS200
quadrupole mass spectrometer (QMS). To identify the
species adsorbed over the 17 wt% Ni/c-Al2O3 catalyst and
to investigate the deactivation phenomenon during the
amination reaction, H2-TPR experiments were also carried
out under flowing 5 % H2/Ar (50 cm3 min-1) from 50 to
400 °C with 10 °C min-1 heating. The evolution of NH3
(m/e = 17) and H2 (m/e = 2) were recorded during H2-
TPR. Prior to the H2-TPR experiment, the sample was
reduced under flowing H2 (50 cm3 min-1) at 600 °C for
3 h; the reduced Ni/c-Al2O3 catalysts were successively
pretreated under flowing 20 % NH3/N2 (50 cm3 min-1) or
4 % NH3/16 % H2/N2 (50 cm3 min-1) at 170 °C for 12 h
and then cooled to 50 °C.
2 Experimental
2.1 Catalyst Preparation
Ni/c-Al2O3 catalysts with different nickel loadings from 4
to 27 wt% were prepared by incipient wetness impregna-
tion method with Ni(NO3)2ꢀ6H2O (Sigma-Aldrich) solution
on a commercial c-Al2O3 (Procatalyse, 194 m2 g-1). The
impregnated catalyst samples were dried at 100 °C for 24 h
and subsequently calcined at 500 °C for 2 h in a muffle
furnace under flowing air (200 cm3 min-1). The final cat-
alysts are denoted as Ni(x)/Al2O3, where x (x = 4, 11, 17,
23 and 27) represents the weight percent of Ni metal.
The metal dispersion and surface area were measured by
H2 chemisorption at 100 °C using
a Micrometrics
ASAP2020C instrument equipped with a high vacuum pump
providing a vacuum of 10-6 Torr. Prior to the adsorption
experiments, the sample (0.3 g) was reduced at 600 °C for
3 h under flowing H2 (50 cm3 min-1). H2-chemisorption
uptakes were separately determined as the difference
between two successive measured isotherms. The metal
dispersion and nickel metal surface area were calculated by
assuming that H/Ni stoichiometry was one. The reduction
degree was determined by the O2 titration method and the
particle size of the nickel metal was then corrected by con-
sidering the reduction degree. The reduction degree was
determined by the following equation: [the amount of O2
consumption]/[the theoretical amount of H2 consumption
2.2 Catalyst Characterization
The surface area, pore volume, and pore size distribution
were determined by N2 physisorption at -196 °C using a
Micromeritics ASAP 2020 apparatus. The samples were
degassed at 250 °C for 6 h. The surface area was calculated
in the relative pressure range of 0.05–0.2. The pore size
123