G Model
CATTOD-9761; No. of Pages8
ARTICLE IN PRESS
B.-S. Kim et al. / Catalysis Today xxx (2015) xxx–xxx
2
most CP studies of biomass components have used microporous
zeolites, e.g. HZSM-5, HY, and HBeta [17,19–24], while the appli-
cation of mesoporous materials (e.g. Al-SBA-15, Al-MCM-41, etc.)
Ultima III (a Cu K␣ X-ray at 30 kV, 40 mA) and using Rigaku
D/Max-2500 (a Cu K␣ X-ray at 40 kV, 300 mA), respectively. Sur-
face area and pore size distribution were derived from the N2
[
25–30], metal oxides (e.g. SiO , MgO, Al O , TiO , etc.) [31], and
adsorption–desorption isotherms prepared by Micromeritics Tri-
2
2
3
2
◦
metal chloride (CuCl , etc.) [32], is very limited. Mesoporous cat-
star 3000 at −196 C (liquid N ), using Brunauer–Emmett–Teller
2
2
alysts containing various metal components are expected to be
effective for the catalytic conversion of large molecules contained
in bio-oil, calling for further research efforts in this field.
Vanadium is an effective catalyst material for various reac-
tions including selective catalytic reduction, VOC oxidation,
and oxidative dehydrogenation. Therefore, it is expected that
vanadium-based catalysts have high catalytic activity for biomass
pyrolysis. However, vanadium-containing catalysts have been used
neither for ex situ CP of lignocellulosic biomass materials nor for
that of biomass components.
In this study, H-V-MCM-41 catalysts were synthesized by incor-
porating vanadium within a representative mesoporous material
MCM-41 and applied to the ex situ CP of biomass components,
for the first time, aiming at enhancing the production of valuable
chemicals.
(BET) model and Barrett–Joyner–Halenda (BJH) method, respec-
tively. Scanning electron microscopy (SEM) images were obtained
using JEOL JEM-7100F at an accelerating voltage of 15 kV. The acidi-
ties of the catalysts were examined using ammonia-temperature
programmed desorption (NH -TPD) conducted from room tem-
3
◦
◦
◦
perature to 700 C with a rising rate of 10 C/min. First, 0.1 g of
catalyst sample was heated for 30 min at 200 C in a 40-ml/min He
gas flow. The adsorption of NH3 on the catalyst surface was then
conducted by flowing 4.9 wt% NH /He gas for 1 h at room temper-
3
ature. NH3 desorbed during the temperature rising was detected
using a thermal conductivity detector. Fourier transform infrared
(FT–IR) spectroscopy was carried out through Bruker VERTEX 70 in
−
1
the range of 4000–400 cm at room temperature. FT–IR spectra
are measured by KBr wafer technique.
2.4. Ex situ CP using Py-GC/MS
2
. Experimental
Pyrolysis experiments were performed using Py-GC/MS, which
2.1. Samples
is a combination of a vertical furnace type pyrolyzer (Py-2020D,
Frontier-Lab Co.) and GC (Agilent 7890A Gas Chromatography)/MS
(Agilent 5975C inert Mass Spectral Detector). The biomass compo-
nents and catalyst were placed in a metal sample cup to be inserted
into a heated pyrolyzer. For each pyrolysis experiment, 1 mg of
biomass component was placed in the cup. In the case of CP, 1 mg of
catalyst was added over the biomass component sample layer, with
a quartz wool layer located in-between separating the biomass and
catalyst layers. In this arrangement, non-catalytic pyrolysis (non-
CP) and reforming occur sequentially; the vapor product produced
from non-CP is reformed when it passes through the catalyst layer.
Helium gas with a split ratio of 50:1 was used as the carrier gas
flowing through the reactor.
Commercial cellulose, xylan (model compound of hemicel-
lulose), kraft lignin, and levoglucosan were purchased from
Sigma–Aldrich.
2
.2. Synthesis of H-V-MCM-41
Highly ordered mesoporous silica MCM-41 was synthesized
by the following procedure. Cetyltrimethylammonium bro-
mide (CTAB, 24.29 g, 99+%, ACROS) were dissolved in distilled
water (280 g). Then, sodium silicate solution (100 g, 20 wt% SiO2,
Na/Si = 0.5) were added to the CTAB solution at room temperature
drop by drop. The mixture was vigorously stirred for 1 h at room
◦
temperature and aged in an oven at 100 C for 24 h. Then, the
◦
Each pyrolysis experiment was conducted for 3 min at 500 C.
mixture was cooled down at room temperature and pH was
adjusted to 10 by using 50 wt% aqueous acetic acid solution.
The pyrolysis product was analyzed by the GC/MS equipped with
an ultra alloy-5 column (30 m × 0.25 mm × 0.5 mm). MicroJet cryo-
trap was used to analyze volatile components with high resolution.
The pyrolysis product gas was condensed using liquid nitrogen for
◦
The mixture was reheated at 100 C for 48 h. The cooling – pH
adjustment – aging process was repeated two more times. The
reaction mixture was filtered, washed with distilled water, and
3
min and introduced into the column by thermal desorption. The
◦
dried at 80 C for 24 h. Dried powder was washed with HCl (36 wt%,
◦
GC/MS interface temperature was set at 300 C and the GC oven
temperature was programmed to increase from 40 C to 320 C with
a rate of 5 C/min. Including the constant-temperature periods of
◦
SAMCHUN)-dissolved ethanol solution, and dried in the 80 C
oven for 24 h. Finally, the product was calcined at 550 C for 3 h
◦
◦
◦
◦
in air. In order to introduce catalytic activities on mesoporous
silica (MCM-41), vanadium was incorporated into MCM-41 with
various ratios. Before adding sodium silicate solution, vanadyl
sulfate hydrate, VOSO ·xH O (97 wt%, Sigma–Aldrich), was added
4
min and 10 min, respectively, before and after the temperature
rising, the total analysis time was 70 min. The mass spectra picks
were interpreted using the NIST05 library.
In order to examine the effects of catalyst dose, additional exper-
iments were carried out changing the quantity of catalyst used for
each experiment, with the other conditions remaining unchanged.
4
2
to the solution. The rest of synthetic procedure was the same. The
target doping ratios of vanadium were 5, 10, and 30 wt%; therefore,
corresponding added masses of VOSO ·xH O were 1.8479, 3.6958,
4
2
and 11.0875 g, respectively.
3. Results and discussion
Ion exchanges of V-MCM-41 with different vanadium contents
were carried out with aqueous solution of 2 M NH Cl (98.5%, SAM-
CHUN). Calcined mesoporous silica (3 g) was added to aqueous
4
3.1. Characterization of catalysts
solution of 2 M NH Cl (0.5 L), and the mixture was vigorously stirred
4
◦
Fig. 1 shows low angle and high angle XRD patterns of synthe-
at 80 C for 24 h. Resulting powders were filtered, washed with
◦
◦
sized H-V-MCM-41 catalysts. 5 and 10 wt% H-V-MCM-41 have 2-D
distilled water, and dried for 24 h in the 80 C oven. After dry-
◦
hexagonal pore structure diffraction patterns (2ꢀ = 0.4–10 ) and
ing samples, they were calcined for 3 h at 500 C. Finally obtained
diffraction line of amorphous silica. The XRD pattern of 30 wt%
H-V-MCM-41 indicates that 2-D hexagonal pore structure was
catalyst was named H-V-MCM-41.
2.3. Characterization of catalysts
almost collapsed due to crystallization of V O5 leaving a disordered
2
Wide-angle X-ray diffraction (XRD) patterns and small-angle
2
X-ray scattering (SAXS) patterns were obtained using Rigaku
detached from silica frameworks during heat treatment. Therefore,
Please cite this article in press as: B.-S. Kim, et al., Ex situ catalytic upgrading of lignocellulosic biomass components over vanadium