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W. Li et al. / Catalysis Today 251 (2015) 53–59
catalysts. For example, Jiang et al. reported that the introduction of
(30 m × 0.32 mm × 0.33 m), as well as another GC equipped with
a thermal conductivity detector, Gaskuropack 54 column (length,
3 m), and active carbon column (length, 2 m). The calibrated area
was normalized to calculate the conversion and product selectivi-
ties.
Lactic acid was hydrogenolyzed in a 50 mL steel autoclave with a
magnetic stirrer. Subsequently, 10 mL 5% lactic acid aqueous solu-
tion and 0.10 g as-reduced catalyst were placed in the autoclave.
The reactor was then purged thrice with 1.0 MPa H2 (99.995%)
and then pressurized to 3.0 MPa; the temperature was increased
to 473 K. After the reaction, the solution was separated from the
catalysts by decantation and analyzed by a HPLC (Shimadzu LC-20)
equipped with a refractive index and UV–Vis detectors. The conver-
sion and selectivity were calculated by normalizing the calibrated
area.
C
O and C C cleavages [19]. Miyake et al. revealed that the addition
of appropriate amounts of Sn to Ru-based catalysts promoted cat-
alytic activity and selectivity during the hydrogenation of fatty acid
catalysts demonstrated good yields in the hydrogenolysis of satu-
rated carboxylic acids to their corresponding alcohols; however,
[21].
SBA-15-supported Ru–Fe catalysts exhibited significant
improvements in the catalytic performance for the hydrogenolysis
of AcOH to EtOH compared with the monometallic counterparts
and those that use SiO2 as the carrier [17]. The Ru–Fe catalysts
could also actively convert carboxylic acids (e.g., propionic acid,
butyric acid, levulinic acid, and lactic acid) to their corresponding
2.3. Catalyst characterizations
alcoholic chemicals. Characterization results indicated that
a
small portion of Fe species was alloyed with Ru, whereas FeO1+x
(0 < x < 0.5) was dispersed on the catalyst surfaces. As a matter
of fact, iron-containing zeolites and mesoporous materials with
high specific area, uniform pore size distribution, and large pore
size can potentially support Ru catalysts. Therefore, in this study,
FeSBA-15-supported Ru catalysts were prepared; the structural
and catalytic properties of these catalysts were analyzed in
connection to the hydrogenolysis of carboxylic acids.
Ru and Fe contents on the catalysts were determined by a S8-
TIGER X-ray fluorescence spectrometer (XRF). The samples were
prepared by mixing 0.20 g catalyst and 0.80 g boric acid and com-
pressing into tablets (diameter, 36 mm; thickness, 2 mm).
Fe leaching was determined by inductively coupled plasma
atomic emission spectrometry (ICP-AES) on a Thermo Elemen-
tal IRIS Intrepid II XSP. The liquid was evaporated to remove the
organic compounds, and was then treated by aqua regia at 353 K
for 30 min. The resultant solution was heated up to 363 K to evapo-
rate the solvent. The residue was diluted with 5% HCl and filtrated
to a 25 mL volumetric flask before measurement.
2. Experimental
2.1. Catalyst preparation
UV–Vis light diffuse reflectance spectroscopy (UV–Vis DRS) was
performed on a Cary 5000 UV–Vis–NIR spectrophotometer (wave-
length, 200–800 nm).
AcOH, propionic acid, butyric acid, levulinic acid, lactic acid,
1,4-dioxane, EtOH, RuCl3·nH2O, and Fe(NO3)3·H2O were pur-
chased from China Pharmaceutical Group Shanghai Chemical
Reagent Co., Ltd. (Shanghai, China). Amphiphilic triblock copolymer
from Sigma–Aldrich. Hydrogen and nitrogen were purchased from
Linde Industrial Gases. All the reagents were used as received with-
out further purification.
Ordered hexagonal mesoporous FeSBA-15 and SBA-15 were
synthesized as previously described [22,23]. FeSBA-15 sup-
port was successfully synthesized with different Fe contents.
FeSBA-15-supported Ru catalysts were impregnately prepared by
incorporating a specific amount of RuCl3·nH2O and 1.0 g FeSBA-
15 with different Fe contents in acetone solution. After stirring
for about 6 h, the mixture was evaporated, dried and calcined at
573 K for 4 h; this mixture was labeled as x% Ru/y% FeSBA-15. For
comparative purposes, a Ru–Fe/SBA-15 catalyst was synthesized
by co-impregnation and labeled as x% Ru–y% Fe/SBA-15-IM, where
x and y represent the weight percentages.
N2 adsorption–desorption isotherms were obtained on
a
Micromeritics TriStar II 3020 porosimetry analyzer at 77.3 K. The
specific surface area or the average pore diameter and pore size dis-
tribution were calculated based on the Brunauer–Emmett–Teller or
Barrett–Joyner–Halenda method.
H2-temperature-programmed reduction (H2-TPR) profiles were
measured in a Micromeritics AutoChem II 2920 Chemisorption
Analyzer. H2 consumption was detected by recording mass spec-
trometer signals (m/e = 2).
X-ray diffraction (XRD) patterns were obtained on a Philips PAN-
alytical X’pert PRO diffractometer and Cu K␣ radiation (operating
voltage, 40 kV; current, 30 mA).
Transmission electron microscopy (TEM) images were gener-
ated using a Tecnai F30 electron microscope at an acceleration
voltage of 300 V. The powder for TEM analysis was dispersed in
EtOH and deposited into copper grids.
Metal dispersion was calculated according to CO chemisorption,
which was performed using a Micromeritics ASAP 2020M+C. The
sample was purged with high-purity H2 (purity, 99.999%) at 623 K
for 30 min and then evacuated for 30 min. CO was introduced after
vacuum cooling to 308 K. The first isotherm (total CO uptake) was
measured. The amount of chemisorbed CO was taken as the differ-
ence between the total and reversibly adsorbed CO.
X-ray photoelectron spectroscopy (XPS) was carried out on a
PHI QUANTUM 2000 Scanning ESCA Microprobe instrument with
an Al K␣ radiation source (hꢀ = 1486.6 eV). The binding energy was
calibrated from that of C 1s (284.6 eV).
2.2. Catalytic test
The hydrogenolysis of AcOH, propionic acid, butyric acid, and
levulinic acid (10 wt% levulinic acid/1,4-dioxane solution) was per-
formed in a fixed-bed reactor equipped with a computer-controlled
auto-sampling system. A 0.20 g catalyst was placed into a glass tube
and pretreated in 5% H2–95% N2 flow at 623 K for 4 h. The tempera-
ture of pure H2 was reduced to the required reaction temperature.
This gas was then fed into the reactor, and the pressure of the reac-
tion system was controlled. The carboxylic acids were pumped
into the reactor via a Series III digital high-performance liquid
chromatography (HPLC) pump (Scientific Systems, Inc.). The oxy-
genates and gas-phase products (e.g., CH4, CO2, CO, and C2H6) were
respectively detected using a gas chromatograph (GC) equipped
with a flame ionization detector and KB-Wax capillary column
3.1. Physical properties
Fig. 1 shows the low-angle XRD pattern of mesoporous FeSBA-
15 with various Fe contents. The diffraction peaks at 0.88◦, 1.44◦,