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T. Yamagishi et al. / Journal of Molecular Catalysis A: Chemical 244 (2006) 201–212
In this article, we investigated the performance of vanadia
Temperature-programmed reduction (TPR) was carried out
in a fix bed reactor equipped with a TCD detector using 5%
H2 diluted with Ar (30 ml/min). The amount of catalyst was
0.05 g, and the temperature was increased from room tempera-
ture to 1123 K at the heating rate of 10 K/min. Temperature-
programmed desorption (TPD) of CO adsorbed on the cata-
lyst was carried out in a closed circulation system equipped
with a quadrupole mass spectrometer (Balzers QMS 200F).
The amount of the catalyst was 0.10 g and the temperature
was increased from room temperature to 773 K at the rate of
10 K/min. The catalyst was exposed to CO (7 kPa) at room tem-
perature after reduction in H2 (7 kPa) and evacuation at 573 K
before TPD measurements.
Temperature-programmed surface reaction (TPSR) of
adsorbed CO with H2 was carried out in the fixed bed flow reac-
tor under atmospheric pressure. The effluent gas was analyzed
by FID-gas chromatograph (Shimadzu GC-14B) equipped with
a methanator using a Gaschropak 54 column every 30 s. The
catalyst weight was 0.1 g, and the temperature was increased
from room temperature to 600 K at the heating rate of 10 K/min
under the flow of 10% H2 (total flow rate: 10 ml/min, balanced
with He). The catalyst was exposed to CO (5 kPa, total flow
rate 10 ml/min, balanced with He) at room temperature after H2
reduction and purge with He at 573 K before TPSR measure-
ments.
promoted Rh/SiO2 (V–Rh/SiO2) catalysts prepared via RhVO4
mixed oxide in hydroformylation of olefins (ethylene and propy-
lene) and CO hydrogenation under atmospheric pressure. In
addition, from the catalyst characterization data, the mechanism
of the promotion by vanadium oxide is discussed.
2. Experimental
2.1. Catalyst preparation
AllcatalystswerepreparedbyimpregnatingSiO2 support(Q-
100 or G-6; Fuji Silysia Chemical Ltd.) with aqueous solution
of metal salts. Before the impregnation, SiO2 was calcined in air
at 1173 K for 1 h to avoid the structural change during the cata-
lyst preparation. The BET surface areas of the SiO2 (Q-100 and
G-6) after the calcination were 38 and 535 m2/g, respectively.
Rh/SiO2 (Q-100 and G-6) catalysts were prepared by the incipi-
ent wetness method using RhCl3·3H2O (N.E. Chemcat Corpora-
tion, >98%). Unless otherwise stated, the SiO2 (Q-100) support
was used. The method of preparing modified Rh catalysts (M-
Rh/SiO2, M = V, Fe, Zn, Mo, Co, Zr and Nb) was as follows: after
the impregnation of SiO2 with RhCl3·3H2O aqueous solution
and drying at 383 K for 12 h, the modification with additive com-
ponent was carried out by the subsequent impregnation using the
aqueous solution of NH4VO3 (WAKO Pure Chemical Indus-
tries Ltd., >99.5%), Fe(NO3)3·9H2O (WAKO Pure Chemical
Industries Ltd., >99%), Zn(NO3)2·6H2O (WAKO Pure Chemi-
cal Industries Ltd., >99%), (NH4)6Mo7O24·4H2O (WAKO Pure
Chemical Industries Ltd., >99%), Co(NO3)2·6H2O (WAKO
Pure Chemical Industries Ltd., >98%), ZrO(NO3)2·2H2O
(SOEKAWA CHEMICALS, >99%) and (NH4)3[NbO(C2O4)3]
(CBMM International LDTA, AD-382). After the catalysts were
dried at 383 K for 12 h again, they were calcined in air at
573–973 K for 3 h. The loading amount of Rh was 4 wt%, and
the amount of additive was adjusted to molar ratio of M/Rh = 1.
V2O5/SiO2 was prepared by impregnating SiO2 (Q-100) with
the aqueous solution of NH4VO3. After the sample was dried at
383 K for 12 h, it was calcined at 773 K for 3 h. Loading amount
of vanadium was adjusted to that of V–Rh/SiO2.
Fourier transform infrared spectra (FTIR) of CO adsorption
was recorded at room temperature by an FTIR spectrometer
(Nicolet, Magna-IR 550 spectrometer) in the transmission mode
using a quartz glass IR cell with CaF2 windows connected to the
vacuum-closed circulating system. The catalyst was well mixed
with the same weight of SiO2 (fine powder, AEROSIL SiO2 380,
BET 380 m2/g), and it was pressed into a disk of 20 mm Ø and a
weightofabout0.03 g. ThecatalystwasexposedtoCO(7 kPa)at
room temperature after the reduction with 7 kPa H2 and evacua-
tion at 573 K. After CO adsorption, the gas was evacuated. FTIR
spectra of adsorbed CO were obtained under vacuum. H2–D2
exchange reaction under presence of CO was carried out in the
closed circulation system equipped with the quadrupole mass
spectrometer. The catalyst amount was 0.5 g, and the catalyst
sample was reduced in 33.3 kPa of H2 at 573 K for Rh-based cat-
alyst and at 1023 K for V2O5/SiO2, and subsequently evacuated
at the same temperature. After the temperature reached the reac-
tion temperature, reactant gases (PH = PD = PCO = 20 kPa,
2.2. Catalyst characterization
2
2
X-ray diffraction (XRD) measurements were carried out with
an X-ray diffractometer (Philips X’Pert MRD) equipped with a
graphite monochromator for Cu K␣ (40 kV, 20 mA) radiation.
The mean particle size was calculated from the XRD line broad-
ening measurement using Scherrer equation [31,33]. Transmis-
sion electron microscope (TEM, JEOL JEM-2010) observation
was carried out for V–Rh/SiO2 catalysts after reduction, CO
hydrogenation and ethylene hydroformylation. The amounts of
H2 andCOchemisorptionweremeasuredinaconventionalvolu-
metric adsorption apparatus; detailed procedures were described
elsewhere [34,35]. The amounts of the total H2 chemisorption
(H/Rh) and the irreversible CO chemisorption (CO/Rh) were
measured at room temperature after H2 reduction and evacua-
tion at 573 K.
PAr = 6 kPa as internal standard gas) were introduced and they
were continuously circulated during the reaction. The reaction
was carried out in the range of room temperature to 353 K, and
the gas phase was analyzed by the quadrupole mass spectrometer
every 4.5 min.
2.3. Hydroformylation of ethylene and propylene
Ethylene hydroformylation was carried out in the fixed bed
flow reactor system under atmospheric pressure. The catalyst
was pretreated under hydrogen flow (30 ml/min) at 573 K for
1 h. After the reactor was cooled down to room temperature,
the reactant gases for hydroformylation of ethylene (PC H
=
2
4
PCO = PH = 33.8 kPa) were fed to the catalyst bed, and then
2