In situ synthesis of molybdenum oxide@N-doped carbon from biomass for selective vapor phase hydrodeoxygenation of lignin-derived phenols under H2 atmosphere

Article abstract of DOI:10.1039/c6ra21989f

The vapor phase hydrodeoxygenation (HDO) of lignin-derived phenols under H₂ atmosphere has great significance for producing high-quality fuels and commodity chemicals. Herein, we reported a simple, green method to prepare molybdenum oxide@N-doped carbon (MoO_x@NC) via in situ pyrolysis of molybdenum precursor preloaded cellulose and demonstrated its catalytic performance for vapor phase HDO of lignin-derived phenols. When the pyrolysis temperature was at 600 °C, the catalyst (MoO_x@NC-600) exhibited the best catalytic performance in vapor phase HDO of guaiacol. Through systematically investigating the parameters, such as: reaction temperature, WHSV, residence time, and concentration, the optimal reaction conditions for vapor phase HDO of guaiacol were 450 °C and 1 h^-1 with atmospheric H₂. The concentration of the feed was 20% in mesitylene, and the residence time was about 3.3 s. The carbon yield of aromatic hydrocarbons was 83.3%, with 65.7% benzene, 15.5% toluene and 2.1% alkylbenzenes. In addition, other lignin-derived phenols were also investigated and desired results were achieved with the MoO_x@NC-600 catalyst. Furthermore, MoO_x@NC-600 showed good stability due to the N-doped carbon formed on the surface of the MoO_x particles. The catalysts were characterized using elemental analysis, AAS, BET, XRD, XPS, TEM, and EDS mapping. The high catalytic performance of MoO_x@NC-600 toward lignin-derived phenols HDO can be attributed to the synergistic effect of the carbon supports and Mo⁵⁺ (molybdenum oxynitrides), Mo^δ+ (Mo₂N) and Mo⁴⁺ on the surface of the MoO_x particles.

Full text of DOI:10.1039/c6ra21989f

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ARTICLE
In situ synthesis of molybdenum oxide @ N-doped
Carbon from biomass for selective vapor phase
hydrodeoxygenation of lignin-derived phenols under
atmosphere H2
Cite this: DOI: 10.1039/x0xx00000x
Lujiang Xu,§ Zheng Han,§ Ying Zhang*, Yao Fu*
The vapor phase hydrodeoxygenation (HDO) of ligninꢀderived phenols under atmosphere H2 has
a great significance to produce highꢀquality fuels and commodity chemicals. Herein, we reported
a simple, green method to prepare Molybdenum oxide @ Nꢀdoped carbon (MoOx@NC) via in
situ pyrolysis of molybdenum precursor preloaded cellulose and demonstrated its catalytic
performance on vapor phase HDO of ligninꢀderived phenols. When the pyrolysis temperature
was at 600 ºC, the catalyst (MoOx@NCꢀ600) exhibited the best catalytic performance on vapor
phase HDO of guaiacol. Through systematically investigating the parameters such as: reaction
temperature, WHSV, residence time, and concentration, the optimal reaction conditions for vapor
phase HDO of guaiacol was 450 °C, 1 hꢀ1 with atmospheric H2. The concentration of the feed
was 20% in mesitylene, and the residence time was about 3.3 s. The carbon yield of aromatic
hydrocarbons was 83.3%, with 65.7% of benzene, 15.5% of toluene and 2.1% of alkylbenzenes.
In addition, other ligninꢀderived phenols were also investigated and desired results were achieved
with MoOx@NCꢀ600 catalyst. Furthermore, MoOx@NCꢀ600 showed good stability due to the
Nꢀdoped carbon formed on the surface of the MoOx particles. The catalysts were characterized
by elemental analysis, AAS, BET, XRD, XPS, TEM, and EDS mapping. The high catalytic
performance of MoOx@NCꢀ600 toward ligninꢀderived phenols HDO can be attributed to the
synergistic effect of carbon supports and Mo5+ (molybdenum oxynitides), Moδ+ (Mo2N) and
Mo4+ on the surface of MoOx particles.
Received 00th January 2012,
Accepted 00th January 2012
DOI: 10.1039/x0xx00000x
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1. Introduction
Hydrodeoxygenation (HDO) is the most promising route to
improve the effective H/C ratio of pyrolysis bioꢀoils and
With the ultimate consumption of fossil resources and the
emission of greenhouse gases, the study on alternative energy
sources have got much attention. Lignocellulosic biomass is an
attractive renewable feedstock that can be converted to the
transportation fuels and chemicals.1 Lignin, which comprises
up to 30wt% of lignocellulosic biomass, is a natural polymer
consisted of methoxylated phenylpropane units featuring
numerous ether linkages (CꢀOꢀC), as well as hydroxyl (ꢀOH),
and methoxyl (ꢀOMe) side groups.2 Fast pyrolysis is an
effective process that can convert lignin to generate a mixture
of nonꢀcondensable liquid oil, gases, and solid.3 However,
monoꢀphenols (such as phenol, syringol, guaiacol, and
catechol), and other polysubstituted phenols in the lignin
pyrolysis bioꢀoil lead to high instability, viscosity,
corrosiveness, and polarity.4,5 Therefore, the oxygen must be
removed before the lignin pyrolysis oil can be used as a
substitute for diesel,gasoline or aromatic chemicals.
produce hydrocarbons either as final fuel components (e.g.,
gasoline and diesel) or as fuel intermediates (small olefins and
alkanes).6,7 The key challenge faced by HDO processes is
achieving a high degree of oxygen removal, while reducing
hydrogen consumption.8 Conventional hydrodesulphurization
(HDS)
/
hydrodenitrogenation (HDN) catalysts exhibit
promising activity in HDO of phenolic compounds such as
phenol, anisole, and guaiacol.9ꢀ13 However, the metalꢀsulfide
catalysts suffer from deactivation in the presence of high water
content and the continuous addition of sulfur is required in the
reactant stream to maintain the catalysts in the sulfide form. In
addition, some supported noble metals such as Ru, Rh, Pd, Pt,
and Re, as well as base metals, such as Cu, Ni, Fe and their
heterometallic alloys are also active for hydrogenation /
hydrogenolysis reactions, but the HDO process over these
catalysts required high H2 pressure, which also result in
aromatic ring saturation.14ꢀ18 High pressure process would lead
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to high operational cost.19 Therefore, it is necessary to develop phenol, and found Nꢀdoped carbon could strongly promote the
a HDO process employing low cost catalysts with high stability chemoselective reduction of phenol.48,49
and low H2 pressure.
In this study,
a
new molybdenumꢀbased catalyst
Recently, many studies on vapor phase HDO of ligninꢀ (MoOx@NC) for selective HDO of ligninꢀderived phenols was
derived phenols via C–O bond cleavage without hydrogenating synthesized. MoOx@NC catalysts were synthesized via coꢀ
the aromatic ring under atmosphere H2 were reported.6,20 pyrolysis of biomass and (NH4)6Mo7O24•4H2O in one step. The
Olcese and coꢀworkers showed that Fe/SiO2 could be used as catalysts prepared at different pyrolysis temperature were
catalyst in vapor phase HDO of guaiacol, while the yield of obtained. Guaiacol was served as the model compound to test
aromatic hydrocarbons was only 38%.21,22 Wang’s group the catalytic activity. The factors which may affect the catalytic
synthesized carbonꢀsupported bimetallic Pd–Fe catalysts which performance of MoOx@NC catalysts in the HDO process,
have a good HDO activity of guaiacol and
mꢀCresol with good including catalysts (Cꢀ600, NCꢀ600, MoOx@C, and
aromatic hydrocarbons yield.23ꢀ25 Nie and coꢀworkers employed MoOx@NCꢀT), reaction temperature, WHSV, residence time
the bimetallic catalyst Ni–Fe/SiO2 for catalytic conversion of and the content of guaiacol in mixture, were investigated
mꢀcresol into toluene via deoxygenation reaction.26 Metal systematically. Different ligninꢀderived phenols and dimmers
phosphides, such as Ni2P, also demonstrate high HDO activity were tested to produce aromatic hydrocarbons in this study.
for conversion of ligninꢀderived phenols. Wu and coꢀworkers Furthermore, lifetime of MoOx@NC catalyst was measured. In
conducted atmospheric hydrodeoxygenation of guaiacol over addition, catalysts were characterized by elemental analysis,
nickel phosphide with different supports, finding that Ni2P/SiO2 scanning electron microscope (SEM), Brunauer–Emmett–Teller
prefers to produce aromatic hydrocarbons.27 Besides the above surface area (BET), X ray diffraction (XRD), and Xꢀray
catalysts, molybdenumꢀbased catalysts, such as Mo2C, Mo2N photoelectron spectroscopy (XPS).
and MoO3, have shown good activity and selectivity on the
2. Experimental Section
2.1 Chemicals
vapor phase HDO of ligninꢀderived phenols. Ghampson and coꢀ
workers used Mo2N and Mo2N supported on activated carbon,
Al2O3 and SBA to catalyze guaiacol HDO, observing a high
activity and a significant conversion of guaiacol to phenol.
They found that the active site for catalyzing guaiacol
conversion are the Mo2N and Mo oxynitride on the catalyst
surface. Furthermore, their experiments also showed that the
bimetallic nitride catalyst CoMoN gave higher yields of
deoxygenated products than the monometallic nitride catalyst,
but the overall activity of the monometallic nitride catalyst was
higher than that of the bimetallic nitride.28ꢀ30 Lee and coꢀ
workers conducted selective vapor phase HDO of anisole to
benzene over MoC2, and the selectivity of benzene could reach
about 90%.31,32 MoC2 was also used to catalyze HDO of ligninꢀ
Anisole (AR), benzaldehyde (AR), phenol (AR), mꢀcresol
(AR), benzene (AR), toluene (AR), xylene (AR) were
purchased from Sinopharm Chemical Reagent Co. Ltd. Eugenol
(AR), and nꢀpropylbenzene (AR) were purchased from
Shanghai aladdin Biochemical Technology Co., Ltd. Guaiacol
(AR), diphenyl ether (AR), 1,2ꢀdiphenylethane (AR), and
mesitylene (AR) were purchased from Tokyo Chemical
Industry Co. Ltd. (NH4)6Mo7O24•4H2O was purchased from
Alfa Aesar Co. Ltd. All these chemicals were used as received
without any further purification. N2 (99.999%), H2
(99.999%), Ar (99.999%), NH3 (≥99.5%), and He (99.999%)
were purchased from Nanjing Special Gases Factory.
derived phenolic compound mixtures containing
mꢀcresol,
anisole, 1,2ꢀdimethoxybenzene, and guaiacol, and showed good
catalytic activity at ambient pressure.33 However, the carbide
catalyst showed fast deactivation by oxidation with water,
which is a challenge for the catalyst system.34 In addition,
MoOx was employed to catalyze HDO of ligninꢀderived
phenols under atmosphere H2. Prasomsri and coꢀworkers found
that MoO3 is active and selective for a direct CꢀO bond
cleavage of guaiacol in a vapor phase over a packedꢀbed flow
reactor, producing phenol and hydrocarbons with selectivity of
29.3% and 53.5%, respectively.35ꢀ38
Nꢀdoped carbon (NC), as a kind of fascinating material, has
attracted worldwide attention recently.39,40 Because of the
incorporation of nitrogen atoms in the carbon architecture can
enhance chemical, electrical, and functional properties, it has
been widely applied in flexible electronics, energy
conversion/storage devices, and catalyst supports.41ꢀ46 Xu and
coꢀworkers synthesized Pd nanoparticles supported on Nꢀdoped
carbon and catalyzed bioꢀoil upgrading.47 Li and coꢀworkers
synthesized Pd/Nꢀdoped carbon for catalytic hydrogenation of
2.2 Catalyst preparation
For synthesis of MoOx@NC: The MoOx@NC catalysts were
synthesized by direct pyrolysis of (NH4)6Mo7O24•4H2O and
microcrystalline cellulose under ammonia condition, which was
conducted in a pyrolysis reactor. The tubular quartz pyrolysis
reactor was placed in an electrical furnace with a PID
temperature controller and the temperature of the experimental
system was monitored by a Kꢀtype thermocouple. Before the
pyrolysis process (Figure S1), 10.0 g of cellulose and a certain
amount of (NH4)6Mo7O24•4H2O solution were mixed in a flask
and shaken at a constant temperature for 12 hours. Thereafter,
water in the mixture was evaporated under reduced pressure.
Finally, the solid residue was dried again at 110 ºC to remove
the moisture and the Moꢀpreloaded cellulose was obtained.
Then, the Moꢀpreloaded cellulose was filled into the feed pipe.
A 200 ml/min of NH3 flowed through the pyrolysis system to
remove air. Until the temperature reached the preꢀset value, the
mixture was fed into the tubular quartz pyrolysis reactor
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through a piston. The volatiles produced during pyrolysis were
condensed by cold water to obtain bioꢀoil. After the fast
pyrolysis process, the solid residue was kept in the reaction
zone for another 2 hours for further carbonization. Then, the
reactor was cooled under N2 flow (200 ml/min) to room
temperature. At last the MoOx@NCꢀT (T: pyrolysis
temperature) catalyst was obtained and grinded by the glass
mortar. For synthesis of NCꢀ600: cellulose was pyrolysized in
the presence of ammonia at 600 ºC for 2 hours (NCꢀ600). For
synthesis of Cꢀ600: cellulose was pyrolysized in the presence
argon at 600 ºC for 2 hours (Cꢀ600). For synthesis of MoOx@C:
The pyrolysis process was similar to that of MoOx@NCꢀT,
except that the carrier gas was changed to argon during
pyrolysis.
Mass flow rate of phenols solution
(1) WHSV =
Mass usage of catalyst in the catalyst bed
Moles of phenols reacted
(2) Conversion (%)=
×100%
Moles of pehnols fed
Moles of carbon in aromatics
Moles of carbon in phenols fed
(3) Aromatic hydrocarbons yield(C mol%) =
×100%
Moles of carbon in phenols
(4) Phenolic products yield(C mol%) =
×100%
Moles of carbon in phenols fed
Moles of carbon in aromatic hydrocarbons
Moles of carbon in phenols fed
(5) Selectivity (%) =
×100%
2.4 Catalyst Characterization
2.3 Catalyst test
The elemental contents of the catalysts were measured by
atomic absorption spectrum (ICP/AAS, Atomscan Advantage,
Thermo Jarrell Ash Corporation, USA). The N2
adsorption/desorption isotherms of the catalysts were measured
at ꢀ196 °C using the COULTER SA 3100 analyzer to do the
Brunauer–Emmett–Teller surface area (BET) analyses.
Scanning electron micrographs of the MoOx@NC were
obtained using a scanning electron microscope (SEM, Sirion
200, FEI Electron Optics Company, USA). Transmission
electron microscopy (TEM) investigations were performed on a
JEMꢀ2100F instrument (JEOL, Japan). Powder Xꢀray
diffraction (XRD) analysis of the catalyst was carried out on a
theta rotating anode Xꢀray diffractometer (TTRꢀIII, Rigaku,
Japan) by Cu Kα radiation (30 kV/160 mA, λ = 1.54056 Å)
with a scan rate (2θ) of 0.05° s−1. Xꢀray photoelectron
spectroscopy (XPS) analysis was carried out on an
ESCALAB250 instrument (ThermoꢀVG Scientific, UK). The
intensity of the XPS peaks was recorded as counts per second
(CPS) and deconvoluted into subcomponents using a Gaussian
(80%)ꢀLorentzian (20%) curveꢀfitting program (XPSPEAK 4.1
software), with a Shirley type background.
As shown in Figure S2, a benchꢀtop continuous flow reactor
consisting of a quartz tube reactor heated by a furnace and a
condensation tube bathed in liquid nitrogen was used for these
experiments. The catalyst bed supported by quartz wool was
built up in the heating zone of the reactor. A certain
concentration of phenol solution was fed into the reactor with a
peristaltic pump under a certain flow rate and purged with H2.
Volatile products were trapped in the condensation tube cooled
with liquid N2. The gas product was collected with a gas bag.
The detailed method for analyzing the products and processing
data are provided in the supplementary information.
The conversion of phenols, the yield of aromatic
hydrocarbons, phenols, gases and the selectivity of different
aromatic hydrocarbons, were calculated from Equation (1) to
(5).
Table 1. The effect of the catalyst preparation conditions on the guaicol HDO process a.
Entry
1
Cꢀ600
36.5
32.9
ꢀ
2
NCꢀ600
53.4
47.1
ꢀ
3
4
5
6
7
Catalyst
MoOx@Cꢀ600 MoOx@NCꢀ600 MoOx@NCꢀ500 MoOx@NCꢀ550 MoOx@NCꢀ650
Conversion (%)
Overall yield
Gases
97.5
95.2
8.8
100
95.1
9.3
100
92.7
8.0
100
89.2
9.7
100
92
14.5
11.4
58.2
7.9
Coke
3.7
4.2
11.9
59.8
14.7
10.3
68.8
6.7
11.7
46.5
26.5
10.9
49.7
18.9
Aromatic hydrocarbons
Phenols
10.3
18.9
16.7
26.2
Aromatic hydrocarbons
Benzene
8.4
1.9
0
13.0
3.7
0
45.9
13.6
0.3
46.1
19.8
2.9
35.2
10.0
1.3
35.6
12.4
1.7
37.1
18.6
2.5
Tolunene
Other alkylbenzenes
Phenols
Phenol
1.5
17.4
0
0.9
24.5
0.8
0
9.2
1.5
2.7
1.3
3.3
1.7
1.4
0.3
17.9
4.1
12.1
3.6
1.8
3.4
1.1
1.6
anisole
cresol
3.7
2.0
other alkylphenols
0
0.8
1.2
a: The catalytic test conditions: solvent: mesitylene, guaiacol concentration=50%, T=400 °C, WHSVmixture=1 hꢀ1, residence time =2.2s, PH2=1 atm, each
timeꢀonꢀstream is 1h. b: The yield in this study is carbon yield.
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3. Results
catalyst prepared under ammonia atmosphere could enhance the
HDO performance.
3.1 Effect of catalyst preparation condition
Because MoOx@NC catalysts were prepared via an in situ
pyrolysis process, the pyrolysis temperature was an important
parameter to affect the catalyst performance. Entry 4 to entry 7
in Table 1 shows the guaiacol conversion and the detailed
product distribution catalyzed by MoOx@NC catalysts
prepared at different pyrolysis temperatures. Figure 1 shows the
detailed carbon yield of different aromatic hydrocarbons and
phenols. As shown in Table 1, under the selected conditions, all
the guaiacol conversion was 100%. The carbon yield of coke
didn’t change significantly, and kept about 11%. The catalyst
preparation temperature affected the carbon yield of aromatic
hydrocarbons and phenols significantly. When the MoOx@NCꢀ
500 served as catalyst, the carbon yield of aromatic
hydrocarbons and phenols was 46.5% and 26.5%, respectively.
With the catalyst preparation temperature increasing to 600 °C,
the carbon yield of aromatic hydrocarbons reached 68.8% and
the carbon yield of phenols was only 6.7%. If the catalyst
preparation temperature further increased to 650 °C, the carbon
yield of aromatic hydrocarbons decreased, while the carbon
yield of phenols increased. As shown in Figure 1, the carbon
yield of phenol and mꢀcresol decreased with the catalyst
preparation temperature increasing. When it was 600 °C, the
highest carbon yield of benzene (46.1%) and toluene (19.8%)
was obtained. Therefore, 600 °C was the suitable pyrolysis
temperature for preparing the HDO catalyst, and MoOx@NCꢀ
600 was the suitable catalyst for catalytic vapor phase HDO of
ligninꢀderived phenols.
Figure 1. Effect of the catalyst preparation temperature on the
detailed carbon yield of different aromatic hydrocarbons and
phenols.
Herein, a simple and green method was developed to prepare
Molybdenum oxide @ Nꢀdoped carbon (MoOx@NC) via in
situ pyrolysis of molybdenum precursor preloaded cellulose.
Table 1 shows the effect of catalyst preparation condition on
the catalytic activity of MoOx@NC catalyst. Seven kinds of
catalysts were prepared under different conditions. As shown in
entry 1 and 2, we firstly tested the catalytic activity of carbon
(Cꢀ600) and Nꢀdoped carbon (NCꢀ600) on the vapor phase
HDO of guaiacol, and found that both carbon and Nꢀdoped
carbon could catalyze HDO of guaiacol to form aromatic
hydrocarbons and selectively cleaved CꢀO bond to form
phenols. When Cꢀ600 was served as catalyst, the conversion of
guaiacol was 35.6%, and the carbon yield of aromatic
hydrocarbons and phenols was 10.3% and 18.9%, respectively.
When the Nꢀdoped carbon (NCꢀ600) was served as catalyst, the
conversion of guaiacol was 53.4%, and the carbon yield of
aromatic hydrocarbons and phenols was 16.7% and 26.3%,
which was much higher than that of Cꢀ600. Therefore, Nꢀdoped
carbon (NCꢀ600) showed better catalytic performance for vapor
phase HDO of guaiacol. In addition, the molybdenum oxide
supported on Cꢀ600 (MoOx@Cꢀ600) and NCꢀ600
(MoOx@NCꢀ600) catalysts were also tested. As shown in entry
3 and entry 4, MoOx@NCꢀ600 showed better catalytic
performance than MoOx@Cꢀ600 did. When MoOx@NCꢀ600
served as the catalyst, the conversion of guaiacol was 100%,
and the carbon yield of aromatic hydrocarbons and phenols was
68.8% and 6.7%, respectively. While, when MoOx@Cꢀ600
served as catalyst, the conversion of guaiacol was 97.5%, and
the carbon yield of aromatic hydrocarbons and phenols was
59.8% and 14.7%, respectively. Compared with the catalytic
performance of the catalysts prepared under N2 atmosphere, the
catalyst prepared under ammonia atmosphere could produce
more aromatic hydrocarbons and fewer phenols. Therefore, the
3.2 Effect of reaction conditions on the vapor phase HDO of
guaiacol
3.2.1 HDO reaction temperature
Based on the above study, we found that MoOx@NCꢀ600 was
the optimal catalyst for catalytic HDO of guaiacol under
atmosphere H2. However, the carbon yield of aromatic
hydrocarbons was only about 68.8%, and there was still some
phenols producing via partial HDO process. Herein, we further
investigated the reaction conditions on the vapor phase HDO,
which could also affect the product distribution and yield.
Firstly, the effect HDO reaction temperature was investigated
in the range of 300 °C and 600 °C over MoOx@NCꢀ600
catalyst. Figure 2 shows the guaiacol conversion and the overall
yield of coke, gases, aromatic hydrocarbons and phenols (a);
the detailed carbon yield of different aromatic hydrocarbons
and phenols (b) at different HDO reaction temperatures. The
detailed product distributions at different temperatures are
given in the supplementary information Table S3. As shown in
Figure 2, the guaiacol conversion and the carbon yield of coke,
gases, aromatic hydrocarbons and phenols were sensitive to the
HDO temperature. With the temperature increasing from 300 to
600 °C, the carbon yield of gases increased from 4.2% to 16.2%.
In contrast, the carbon yield of coke decreased from 19.5 to
4.8%. It could be caused by that higher temperature promoted
phenols deep cracking to form nonꢀcondensable gas products
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Table 2. Effect of WHSV.
Entry
1
2
3
4
WHSV (hꢀ1)
Conversion (%)
Overall yield
Gases
0.5
100
82.9
13.8
8.2
1.0
1.5
2.0
100
92.3
13.4
6.9
100
91.1
12.5
7.6
96.3
94.1
10.7
8.1
Coke
Aromatic
hydrocarbons
Phenols
60.9
70.2
65.2
5.8
64.1
11.2
0
1.8
Aromatic hydrocarbons
Benzene
41.9
14.8
51.8
15.0
46.3
15.2
43.9
16.3
Tolunene
Other
alkylbenzenes
4.2
3.4
3.7
3.9
Phenols
Phenol
anisole
0
0
0.7
0.6
1.1
0.8
4.3
1.2
cresol
0
0
0.5
0
2.9
1.0
5.0
0.7
other alkylphenols
The catalytic test condition:
solvent: mesitylene, guaiacol
concentration=50%, T= 450 °C, residence time =2.2 s; PH2=1 atm, each
timeꢀonꢀstream is 1h. c: The yield in this study is carbon yield.
temperature further increased (500°C, and 600 °C), the carbon
yield of aromatic hydrocarbons decreased, while the carbon
yield of phenols increased. Higher reaction temperature may
also cause the catalyst deactivation, and lead to the partial
deoxygenation to form phenols, which could be the reason that
the carbon yield of phenols increased with the reaction
temperature further increasing. Thus, 450 °C was the optimal
reaction temperature for HDO guaiacol over MoOx@NCꢀ600
under atmosphere H2.
Figure 2. Effect of HDO temperature on HDO of guaiacol in
over MoOx@NCꢀ600; (a) overall yield; and (b) detailed carbon
yield of different aromatic hydrocarbons and phenols. (Reaction
condition: Catalyst=MoOx@NCꢀ600, solvent: mesitylene,
guaiacol concentration =50%, WHSVmixture=1 hꢀ1 residence
,
time =3.3s, PH2=1 atm.)
3.2.2 WHSV
and prevented the coke formation. When the HDO reaction was
below 400 °C, the guaiacol conversion could not reach 100%.
Meanwhile, the main detected products in the liquid were not
aromatic hydrocarbons but phenols, which were produced via
partial HDO process. Phenol was the main product in phenols.
When the HDO reaction temperature was at 350 °C, the carbon
yield of phenols reached 63.9% (Figure 2a), and the carbon
yield of phenol was 50.9% (Figure 2b). Lower reaction
temperature prevented the catalyst activity, and lead to partial
deoxygenation reaction. At 400 °C, with a full guaiacol
conversion, the product distributions also changed dramatically.
Aromatic hydrocarbons became the main products. The carbon
yield of phenols decreased from 63.9% to 6.7%, while the
carbon yield of aromatic hydrocarbons increased from 6.1% to
68.8%. Benzene and toluene were the main products in the
aromatic hydrocarbons. The carbon yield of other
alkylbenzenes (including xylenes) was very low. When the
HDO reaction temperature increased to 450 °C, the carbon
yield of aromatic hydrocarbons reached the maximum (70.2 %)
and the carbon yield of benzene and toluene was 51.8% and
15.0%, respectively (Figure 2b). Conversely, the carbon yield
of phenols reached the minimum (only 1.8%). If the reaction
In addition to HDO reaction temperature, the effect of WHSV
was also investigated in this study. Table 2 shows the detailed
product distributions at different WHSV. The WHSV was
defined as the ratio of the mass flow rate of guaiacol/mesitylene
mixture to the mass of catalyst used in the reactor. During the
experiments, the mass flow rate of guaiacol ranged from 0.5ꢀ2 g
hꢀ1 while the mass of catalyst was kept constant at 1 g. The
HDO reaction temperature was kept at 450 °C. As shown in
Table 2, all the guaiacol conversion was 100% in the range of
0.5 to 1.5 hꢀ1. When the WHSV increased to 2 hꢀ1, the
conversion decreased to 96.3%. Meanwhile, the carbon yield of
gas and coke decreased from 13.8% to 10.7% with the WHSV
increasing from 0.5 to 2 hꢀ1. The carbon yield of coke kept
about 7.5%. The carbon yield of aromatic hydrocarbons and
phenols was affected by WHSV significantly. When the WHSV
was at 0.5 hꢀ1, no phenols were detected, and the carbon yield
of aromatic hydrocarbons was about 60.9%. With the WHSV
increased from 0.5 to 1 hꢀ1, the carbon yield of aromatic
hydrocarbons and phenols increased from 60.9% and 0% to
70.2% and 1.8%, respectively. If the WHSV further increased
to 1.5 hꢀ1 and 2 hꢀ1, the carbon yield of aromatic hydrocarbons
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Table 3. Effect of residence time.
Besides the effect of reaction temperature, WHSV, and
residence time, the effect of guaiacol concentration in
mesitylene was investigated in the range of 20% to 100%.
Table 4 shows the detailed product distributions of catalytic
HDO of guaiacol with different concentration. As shown in
Table 4, the guaiacol conversion and carbon yield of gas were
not affected by guaiacol concentration significantly. The
guaiacol conversion was kept at 100%, and the carbon yield of
gases was about 12%. However, the carbon yield of coke,
aromatic hydrocarbons and phenols was affected by the
guaiacol concentration. With the guaiacol concentration
increasing from 20% to 100%, the carbon yield of coke and
phenols increased from 2.7% and 0% to 12.4% and 33.3%,
respectively. Meanwhile, the carbon yield of aromatic
hydrocarbons decreased from 83.3% to 39.8%. The lower
guaiacol concentration, the less coke formation, and the more
aromatic hydrocarbons production. Therefore, the optimal
guaiacol concentration was 20%. Meantime, the carbon yield of
benzene and toluene was 65.6% and 15.5%.
Through systematically investigating the parameters (such as:
reaction temperature, WHSV, residence time, and concentration)
in the vapor phase HDO of guaiacol under atmosphere H2, the
optimal reaction conditions for vapor phase HDO of guaiacol
was at 450 °C, 1 hꢀ1. The concentration of feed was 20%, and
the residence time was about 3.3 s. The carbon yield of
aromatic hydrocarbons was 83.3%, and no phenols was
detected. The carbon yield of benzene, toluene and
alkylbenzenes was 65.7%, 15.5%, and 2.1%, respectively.
Entry
1
2
3
4
catalyst usage (g)
Residence time (s)
Conversion (%)
Overall yield
Gases
0.5
1.1
100
93.8
10.7
6.2
1.0
1.5
2.0
2.2
3.3
4.4
100
92.3
13.4
6.9
100
96.5
12.7
6.3
100
94.3
13.2
7.8
Coke
Aromatic
hydrocarbons
Phenols
54.8
70.2
76.8
0.7
73.3
0
22.1
1.8
Aromatic hydrocarbons
Benzene
39.3
13.8
51.8
15.0
53.9
18.1
50.3
16.6
Tolunene
Other
alkylbenzenes
1.7
3.4
4.8
6.4
Phenols
Phenol
anisole
11.2
4.6
0.7
0.6
0.5
0.2
0
0
cresol
5.3
1.0
0.5
0
0
0
0
0
other alkylphenols
The catalytic test condition:
solvent: mesitylene, guaiacol
concentration=50%, T= 450 °C, WHSVmixture =1 hꢀ1, PH2=1 atm, each
timeꢀonꢀstream is 1h. c: The yield in this study is carbon yield.
started to decrease. Meanwhile, the carbon yield of phenols
increased with the WHSV further increasing. Thus, the optimal
WHSV was 1 hꢀ1 for catalytic HDO of guaiacol over
MoOx@NCꢀ600 under atmosphere H2.
3.2.3 Residence time
3.3 Vapor phase HDO of different lignin-derived
compounds over MoOx@NC catalyst
To further optimize the reaction conditions of catalytic HDO of
guaiacol over MoOx@NCꢀ600 under atmosphere H2, the effect
of residence time was also investigated via changing the
catalyst usage from 0.5 g to 2g and fixing the reaction
temperature, H2 flow rate, and WHSV at 450 °C, 70 ml/min,
and 1 hꢀ1. Herein, the residence time was in the range of 1.1s
and 4.4s. Table 3 shows the detailed product distributions at
different residence time. The guaiacol conversion, and the
carbon yield of coke and gas were not affected by the residence
time significantly. With the residence increasing from 1.1s to
4.4s, all the guaiacol conversion was 100%, and the carbon
yield of coke and gas kept at about 7% and 13%, respectively.
However, the carbon yield of aromatic hydrocarbons and
phenols was very sensitive to the residence time. When the
residence time was at 1.1s, the carbon yield of aromatic
hydrocarbons and phenols was 54.8% and 22.1%, respectively.
Then with the residence time increasing from 1.1s to 3.3 s, the
carbon yield of aromatic hydrocarbons increased to 76.8%,
while the carbon yield of phenols decreased 0.7%. If the
residence time further increased to 4.4s, no phenols were
detected. However, the carbon yield of aromatic hydrocarbons
also decreased. Therefore, the optimal residence time was 3.3 s,
and the catalyst usage was 1.5g. Meanwhile, the carbon yield of
benzene and toluene reached 53.9% and 18.1%, respectively.
Based on the above study, guaiacol could be efficiently
converted to aromatic hydrocarbons via vapor phase HDO
process over MoOx@NC catalyst. In order to investigate the
applicability of the catalyst, other six kinds of ligninꢀderived
Table 4. Effect of guaiacol concentration in mesitylene.
Entry
1
2
3
4
Concentration
Conversion (%)
Gases
20%
100
11.6
2.7
50%
100
12.7
6.3
80%
100
11.0
8.9
100%
100
11.8
12.4
Coke
Aromatic
hydrocarbons
Phenols
83.3
76.8
50.0
23.2
39.8
33.3
0
0.7
Aromatic hydrocarbons
Benzene
Tolunene
65.7
15.5
2.1
53.9
18.1
4.8
37.1
9.9
28.2
8.1
Other alkylbenzenes
3.0
3.5
Phenols
Phenol
anisole
0
0
0.5
0.2
17.3
1.9
23.4
3.6
cresol
0
0
0
0
3.8
0.2
6.0
0.3
other alkylphenols
The catalytic test condition: T=450 °C, residence time =3.3 s, WHSVmixture
=1 hꢀ1, PH2=1 atm, each timeꢀonꢀstream is 1h. c: The yield in this study is
carbon yield.
3.2.4 Guaiacol concentration
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Table 5. Vapor phase HDO of different ligninꢀderived phenols over
MoOx@NCꢀ600 under atmosphere H2.a
ethylenzene was only 28.3%, which means MoOx@NCꢀ600
cannot effectively remove the alcohol hydroxyl group.
Aromatic hydrocarbons and yields b
Yield
Feed
Other
(C %)
90.6
Benzene
90.6
Toluene
N.D
3.4 Catalyst stability
alkylbenzenes
N.D
87.3
82.8
10.3
54.3
77.0
23.0
N.D
4.5
82.0
73.2
12.1
12.6
61.7
5.3
8.2
55.3
N.D
87.2
70.9
87.2
40.5
N.D
2.1
28.3
a: All the feed conversion was 100%. The catalytic test conditions:
guaiacol concentration=20%, T=450 °C, WHSV=1 hꢀ1, residence time
=3.3s, PH2=1 atm, each timeꢀonꢀstream is 1h. b: The yield in this study is
carbon yield.
compounds including phenol, anisole,
mꢀcresol, benzaldehyde,
eugenol, diphenyl ether, and phenethoxybenzene were also
catalyzed by MoOx@NC to produce aromatic hydrocarbons.
For the simple ligninꢀderived compounds (phenol, mꢀcresol,
anisole and benzaldehyde), MoOx@NCꢀ600 showed good
catalytic activity for vapor phase HDO to produce aromatic
hydrocarbons. The carbon yield of aromatic hydrocarbons was
above 80%. When benzaldehyde served as raw material, the
carbon yield of the main product, toluene, was 61.7%. It
indicated that MoOx@NCꢀ600 can catalyze HDO of aldehyde
group in addition to removal the methoxyl and phenolic
hydroxyl groups. More interestingly, 1,2ꢀdiphenylethane could
be detected in the products, and the carbon yield of 1,2ꢀ
diphenylethane was 8.2%. 1,2ꢀDiphenylethane could be
produced via a coupling reaction of benzaldehyde catalyzed by
Nꢀdoped carbon, which had some basic sites. Eugenol could
also be effectively converted to aromatic hydrocarbons by
MoOx@NCꢀ600 catalyst. Meanwhile, allyl group in eugenol
was hydrogenated to propyl group. Thus, propyl benzene was
the main HDO products from eugenol. MoOx@NCꢀ600 could
catalyze lignin dimer model compounds (diphenyl ether,
phenethoxybenzene) HDO. When diphenyl ether served as the
feed, benzene was the only aromatic hydrocarbons product, and
the carbon yield of benzene reached 87.2%. When
phenethoxybenzene served as the raw material, the carbon yield
of benzene could reach 40.5% (theoretical carbon yield
=42.8%), indicating MoOx@NCꢀ600 can effectively remove
the phenolic hydroxyl groups. However, the carbon yield of
Figure 3. The catalyst stability; (a) conversion and overall yield;
(b) detailed carbon yield of different aromatic hydrocarbons
and phenols. (Reaction condition: solvent: mesitylene, guaiacol
concentration=20%, T=450 °C, residence time =3.3s
WHSVmixture=1 hꢀ1)
The catalyst stability is very important in the vapor phase HDO
process. Prasomsri et al. reported that molybdenum oxides
showed a fast deactivation in the vapor phase HDO of cresol.32
When the HDO reaction temperature was at 400 °C, the cresol
conversion decreased from 100% to 10% after a 4 hours’
reaction. Herein, the stability of MoOx@NC was also
investigated at 450 °C using guaiacol as the feed. Figure 3
shows the guaiacol conversion and carbon yield of aromatic
hydrocarbons and phenols (a); the detailed carbon yield of
different aromatic hydrocarbons and phenols (b) at different
time on streams. The detailed product distributions are given in
Table S4 in the supplementary information. As shown in Figure
3a, in the early 7.5 hours, the guaiacol conversion kept 100%,
and the carbon yield of aromatic hydrocarbons and phenols
kept above 80% and 5%. Meanwhile, the carbon yield of
benzene, toluene was about 60% and 20% (Figure 3b),
respectively. Anisole was the main component in the phenols.
With the reaction time further extending to 20 hours, the
guaiacol conversion still kept 100%. However, the carbon yield
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of aromatic hydrocarbons kept decreasing. Meanwhile
，
the
changing trend of benzene and toluene was constant with that
of aromatic hydrocarbons. Conversely, the carbon yield of
phenols increased. When the reaction time reached 20 hours,
the carbon yield of aromatic hydrocarbons decreased to 42.7%,
meanwhile, the carbon yield of phenols increased to 25.8%. To
investigate the reason for the selectivity of aromatics drops
substantially after 7.5 hours and the change of catalyst structure,
the catalyst after the reaction was characterized by elemental
analysis, N2 adsorption/desorption and XPS. Table S5 shows
the physicochemical properties of MoOx@NCꢀ600 before and
after reaction. The elemental contents, surface elemental
contents, BET surface area and pore volume of the catalyst
changed a lot after reaction. The content of carbon on the
surface increased. The content of Mo, N, and BET surface area
and pore volume decreased a lot. It indicated that coke formed
after the reaction, and the coke may cover the active site of the
catalyst, which caused the catalytic activity of the MoOx@NCꢀ
600 decreased.
Figure 4. XRD patterns of NCꢀ600 and MoOx@NCꢀ600.
3.5 Catalyst characterization
According to the above study, we found that MoOx@NCꢀ
600 was the optimal catalyst for catalytic vapor phase HDO of
ligninꢀderived phenols under atmosphere H2. Table 6 shows the
physicochemical properties of MoOx@NCꢀ600 catalyst,
including BET surface area, elemental contents, and catalyst
surface elemental contents. The BET surface area of
MoOx@NCꢀ600 was 81.0 m2/g (The adsorption / desorption of
MoOx@NCꢀ600 was shown in Figure S3 in the supplementary
information). The content of C, H, N, and O was 47.2%, 1.7%,
4.5% and 20.5%, respectively. The metal loading of
MoOx@NCꢀ600 was about 26.1%. For comparison, the
catalyst surface contents were also measured by XPS. The
content of C, N, O, Mo was 85.7%, 6.1%, 6.5%, and 1.7%,
respectively. The content of carbon and nitrogen on the catalyst
surface was much more than that of the bulk catalyst. In
contrast, the content of Mo and oxygen on surface was lower
than that of the bulk catalyst. It indicated that Nꢀdoped carbon
might form on the surface of MoOx particles, which could be
beneficial for the catalyst stability.
XRD was used to monitor the crystallite phase composition
of MoO2, NCꢀ600, and MoOx/NCꢀ600. As shown in Figure 4,
amorphous carbon in the NCꢀ600. The characteristic diffraction
peaks of MoO2 patterns were at 2θ of 26.1°, 36.9°, 41.6°, 53.3°,
60.4°, 66.7°, and 78.8°. The diffraction peaks at 2θ of 26.1°,
36.9°, 41.6°, 53.3°, 60.4°, 66.7°, and 78.8° were also existed in
the XRD patterns of MoOx@NCꢀ600, indicating that the MoOx
in the MoOx@NCꢀ600 was MoO2.
Figure 5. XPS curves of MoOx@NCꢀ600; (a) Survey XPS
curves of O 1s, N 1s, C 1s and Mo 3d of the catalyst. (b) Xꢀray
photoelectron Mo 3d spectra of Mo 3d of MoOx@NCꢀ600
catalyst. (c) Xꢀray photoelectron N 1s spectra of MoOx@NCꢀ
600 catalyst. (d) Xꢀray photoelectron
MoOx@NCꢀ600.
O 1s spectra of
In order to further evaluate the electronic state of
molybdenum, nitrogen and oxygen presenting in the catalyst,
the binding energies of the relative substances were determined
by XPS. Although the diffraction peaks shown in XRD patterns
Table 6. Physicochemical properties of MoOx@NCꢀ600.
BET
Elemental contents
surface
area m2/g
C
H
N
Mo
O
(wt %)
Catalyst elemental
contents a
47.2
85.7
1.7
ꢀ
4.5
6.1
26.1
1.7
20.5
6.5
81.0
Catalyst surface
elemental contents b
a: The content of C, H, and N was determined by elemental analyzer.The
content of molybdenum in MoOx@NCꢀ600 was measured by atomic
absorption spectrum (Escalab 250Xi, Thermo Fisher). b: The elemental
content of the catalyst surface was determined by XPS.
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can only attribute to MoO2, from Mo 3d in Figure 5b, the Mo nitrogen atoms incorporated into graphitic sheets (pyridinicꢀN);
3d doublet contained mixed chemical states with contributions the peak at 400.7 eV can be mainly assigned to pyrrolic/
from Mo δ+, Mo4+, Mo5+, and Mo6+. In details, the 3d5/2 energy pyridoneꢀN.53ꢀ55 From O 1s in Figure 5d, three peaks at 530.5
at 229.0 eV, corresponding to Mo with an oxidation state eV, 532.0 eV and 533.2 eV could be attributed to the MoꢀO,
between +4 and +2, is assigned to Mo2N species.28ꢀ30 Mo2N is OHꢀ and H2O, respectively.56,57
an effective catalyst for catalytic HDO of ligninꢀderived
Figure 6 shows the SEM, TEM, and EDS mapping of
phenols.28,30 The 3d5/2 energy at 229.7 eV, corresponding to MoOx@NCꢀ600. Figure 6a showed porous morphology on
Mo4+, can be assigned to MoO2.35,36 The 3d5/2 energy at 230.8 rough carbon sheet, which is similar to the typical pyrolytic
eV peak could be assigned to molybdenum oxynitrides.30, 50ꢀ52 biochar reported by Liu and coꢀworkers.57,58 TEM images and
The molybdenum oxynitrides is similar to MoOxCyHz, which the corresponding elemental mapping analysis of MoOx@NCꢀ
is associated with the active sites and the HDO activities.35,36 600 (Figure 6bꢀf) could further reveal the morphology of the
The percentage of Mo6+, Mo5+, Mo4+ and Mo δ+ was 42.9 : 12.5 : MoOx@NCꢀ600 catalyst. Figure 6b showed that the MoOx
34.9: 9.7. In addition, no signal corresponding to Mo metal (i.e., particle was irregular, and the particle size of MoOx reached
Mo0 state) was detected. From N1s in Figure 5c, the catalyst about 200 nm. The EDS mapping (Figure 6dꢀf) shows the
displayed 4 binding energies peaks at 395.0 eV, 396.6 eV, MoOx had been successfully embedded on the Nꢀdoped carbon.
398.5 eV and 400.9 eV. The peak at 395.0 eV could be In addition, it also indicated that Nꢀdoped carbon was deposed
attributed to the molybdenum oxynitrides; the peak at 396.6 on the surface of MoOx particle, which would be beneficial for
could be attributed to the MoꢀN in the Mo2N; the peak at 398.5 the catalyst stability.
eV could be attributed to pyridinicꢀlike (398.5 ± 0.2 eV)
c
a
b
100 nm
d
e
f
Figure 6. The SEM, TEM and EDS mapping of MoOx@NCꢀ600; a) SEM analysis; b) TEM analysis; c) Elemental mapping of Mo;
d) elemental mapping of C; e) elemental of O; f) elemental of N.
also characterized by elemental analysis (Table S1) XRD
4. Discussion
(Figure 7), and XPS (Figure 8). As shown in Table S1, with the
pyrolysis temperature increasing, the content of molybdenum
increased, while the content of carbon and nitrogen decreased.
However, when the pyrolysis temperature was 600 °C, the
content of nitrogen strated to increase, which could be due to
the molybdenum nitride formation in the pyrolysis process
In the above study, we found that the pyrolysis temperature was
important to the catalytic activity of MoOx@NC catalysts. To
further illustrate the effect of pyrolysis temperature on the
catalytic activity of MoOx@NC catalysts, these catalysts were
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(Shown in Figure S1). XRD patterns (Figure 7) showed that
molybdenum existed mainly as MoO2 when the pyrolysis
temperature ≤ 600 °C. When the pyrolysis temperature
increased to 650 °C, the diffraction peaks at 2θ of 41.6°, 53.3°,
60.4°, 66.7°, and 78.8° disappeared. While, new diffraction
peak at 2θ of 43.3°, 53.5°, 62.8°, and 75.5° appeared. The new
diffraction peak could be attributed to Mo2N.
Furthermore, XPS curves (Figure 8) also showed that Mo 3d
doublet contained mixed chemical states attributed to Moδ+,
Mo4+, Mo5+, and Mo6+. According to the previous studies, Mo5+
(corresponding to molybdenum oxynitrides), and Moδ+
(corresponding to Mo2N) are active for catalytic HDO of
ligninꢀderived phenols, while Mo6+ is not.28ꢀ30 In present system,
with the pyrolysis temperature increasing, the percentage of
Mo6+ kept about 44%, while the percentage of Mo5+
Mo4+
Figure 8. XPS curves of Mo in different MoOx@NCꢀT
catalysts. a): MoOx@NCꢀ500; b) MoOx@NCꢀ550; c):
MoOx@NCꢀ600; d) MoOx@NCꢀ650.
(corresponding
to
molybdenum
oxynitrides),
(corresponding to MoO2), and Moδ+ (corresponding to Mo2N)
changed significantly. When the pyrolysis temperature was at
500 °C, the Mo 3d attributed to Mo4+, Mo5+, and Mo6+. The
signal (Moδ+) corresponding to Mo2N was not detected. The
percentage of Mo6+, Mo5+, and Mo4+ was 43.4, 37.3 and 19.3,
respectively. When the pyrolysis temperature increased to
550 °C, Moδ+ assigned to Mo2N was detected and the
percentage of Moδ+ was 5%. Then, the percentage of Moδ+
increased with the temperature further increasing. When the
pyrolysis temperature was at 650 °C, the percentage of Moδ+
was 26.5%. By contrast, the percentage of Mo5+ decreased with
the pyrolysis temperature increasing. When the pyrolysis
temperature was at 650 °C, the percentage of Mo5+ was 12.3 %.
For the Mo4+, when the pyrolysis temperature was ≤ 600 °C, the
percentage of Mo4+ increased from 19.3% to 34.9%. If the
pyrolysis temperature further increased to 650 °C, the
percentage of Mo4+ decreased to 15.3%. When the pyrolysis
temperature was at 600 °C, the percentage of Mo4+ was highest,
and the catalyst also showed the best catalytic performance. In
addition, the variation tendency of Mo4+ was consistent with the
variation tendency of the catalyst catalytic performance.
Therefore, besides the Mo5+ and Moδ+, the Mo4+ should also be
the active site in the MoOx@NC catalyst for catalytic HDO.
5. Conclusion
In this study, a simple, and green method was developed to
prepare Molybdenum oxide @ Nꢀdoped carbon (MoOx@NC)
via in situ pyrolysis of molybdenum preloaded cellulose.
MoOx@NC demonstrated excellent catalytic performance and
stability on vapor phase HDO of ligninꢀderived phenols.
Through the study of catalyst preparation condition, we found
that Nꢀdoped carbon could catalyze HDO of guaiacol to form
aromatic hydrocarbons and selectively cleaved CꢀO bond to
form phenols. When the pyrolysis temperature was at 600 ºC,
the catalysts (MoOx@NCꢀ600) exhibited the best catalytic
performance on vapor phase HDO of guaiacol. Through
systematically investigating the parameters (such as: reaction
temperature, WHSV, residence time, and concentration) in the
vapor phase HDO of guaiacol under atmosphere H2, the optimal
reaction conditions for vapor phase HDO of guaiacol was at
450 °C, 1 hꢀ1. The concentration of guaiacol in mesitylene was
20%, and the residence time was about 3.3 s. The carbon yield
of aromatic hydrocarbons was 83.3%, and no phenols was
detected. The carbon yield of benzene, toluene and
alkylbenzenes was 65.7%, 15.5%, and 2.1%, respectively.
Other ligninꢀderived phenols were also investigated and
achieved good results by using MoOx@NCꢀ600. Furthermore,
the catalysts were also characterized by elemental analysis,
AAS, BET, XRD, XPS, TEM, and EDS mapping. Mo4+ could
be the main active site of the MoOx@NC catalysts, and the Nꢀ
doped carbon formed on the surface of MoOx particles could
also be beneficial for the catalyst stability. Therefore, the high
catalytic performance of MoOx@NCꢀ600 toward ligninꢀ
derived phenols HDO can be attributed to the synergistic effect
of carbon supports and Mo5+ (molybdenum oxynitides), Moᵟ+
(Mo2N) and Mo4+ on the surface of MoOx particles.
Acknowledgements
Figure 7. XRD patterns of MoOx@NCꢀT catalysts.
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DOI: 10.1039/C6RA21989F
The authors are grateful to the National Natural Science 15. M. V. Bykova, D. Y. Ermakov, V. V. Kaichev, O. A. ulavchenko, A.
Foundation of China (21572213), the National Basic Research A. Saraev, M. Y. Lebedev and V. A. Yafkovlev, Appl. Catal., B-
Program of China (2012CB216306, 2013CB228103), Anhui Environ., 2012, 113–114, 296–307
Provincial Natural Science Foundation (1408085MKL04), the 16. Y. B. Huang, L. Yan, M. Y. Chen, Q. X. Guo, Y. Fu, Green Chem.,
Program for Changjiang Scholars, Innovative Research Team in 2015, 17 ,3010ꢀ3017.
University of the Ministry of Education of China and 17. M. Y. Chen, Y. B. Huang, H. Pang, X. X. Liu, Y. Fu, Green Chem.,
Fundamental Research Funds for the Central Universities for 2015,17, 1710ꢀ1717.
the financial.
18. M. Asadieraghi, W. M. A. W. Daud, H. F. Abbas, RSC Adv., 2015, 5,
22234ꢀ22255.
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230026,
China.
Fax:
(+86)
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zhzhying@ustc.edu.cn (Ying Zhang); fuyao@ustc.edu.cn (Yao Fu).
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DOI: 10.1039/C6RA21989F
Graphic abstract
In situ synthesis of molybdenum oxide @ Nꢀdoped
Carbon from biomass for selective vapor phase
hydrodeoxygenation of ligninꢀderived phenols under
atmosphere H2
Lujiang Xu, Zheng Han, Ying Zhang, Yao Fu
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 13