NiFe/γ-Al2O3: A universal catalyst for the hydrodeoxygenation of bio-oil and its model compounds

Article abstract of DOI:10.1016/j.catcom.2013.06.037

NiFe bimetallic catalyst shows an excellent activity and selectivity for the hydrodeoxygenation (HDO) of three typical model compounds of bio-oil. The conversion of furfuryl alcohol, benzene alcohol and ethyl oenanthate is 100, 95.48 and 97.89% at 400 C and the yield to 2-methylfuran, toluene and heptane is 98.85, 93.49 and 96.11% at 0.1 ml/min flow speed and atmospheric pressure. It indicates that the major reaction pathway is the cleavage of C-O rather than C-C. After the catalytic HDO of bio-oil over NiFe/Al₂O₃ catalyst, the heating value changes from 37.8 to 43.9 MJ/kg, the pH changes from 6.65 to 7.50.

Full text of DOI:10.1016/j.catcom.2013.06.037

Catalysis Communications 41 (2013) 34–37
Contents lists available at SciVerse ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
NiFe/γ-Al O : A universal catalyst for the hydrodeoxygenation of
2
3
bio-oil and its model compounds
a
a
a
a
b
a
Shuai Leng , Xinde Wang , Xiaobo He , Lin Liu , Yue'e Liu , Xing Zhong ,
a
a,
Guilin Zhuang , Jian-guo Wang ⁎
College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032, P.R. China
a
b
Key Laboratory of Oil and Gas Fine Chemicals of Ministry of Education, Xinjiang University, Urumuqi 830046, P.R. China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 14 May 2013
Received in revised form 23 June 2013
Accepted 24 June 2013
Available online 8 July 2013
NiFe bimetallic catalyst shows an excellent activity and selectivity for the hydrodeoxygenation (HDO) of
three typical model compounds of bio-oil. The conversion of furfuryl alcohol, benzene alcohol and ethyl
oenanthate is 100, 95.48 and 97.89% at 400 °C and the yield to 2-methylfuran, toluene and heptane is
98.85, 93.49 and 96.11% at 0.1 ml/min flow speed and atmospheric pressure. It indicates that the major
2 3
reaction pathway is the cleavage of C–O rather than C–C. After the catalytic HDO of bio-oil over NiFe/Al O
catalyst, the heating value changes from 37.8 to 43.9 MJ/kg, the pH changes from 6.65 to 7.50.
Keywords:
©
2013 Elsevier B.V. All rights reserved.
Hydrodeoxygenation
NiFe bimetallic catalyst
Upgrading of bio-oil
1
. Introduction
of anisole and the hydrotreatment products were cyclohexane and ben-
zene via demethoxy reaction [15]. The study by Resasco et al. showed
the primary products of furfural hydrogenation were furfuryl alcohol
Due to the consumption of fossil sources and increasing of energy
requirements, the search for the alternative energy has caused
economic, political and academic concerns [1]. Different from other
alternative energy (solar, wind and nuclear energy), biomass, which
includes lignocellulose and algae, is the only resource for the produc-
tion of fuels, chemicals and hydrocarbons. Bio-oil, obtained from
biomass by fast pyrolysis or high-pressure liquidation under inert
gas atmosphere, has an irresistible trend applied for transportation
fuel economically and technologically. The bio-oil components are
complex, containing mainly oxygenated compounds as furans, ke-
tones, carboxylic acids, ethers, esters and alcohols [2,3]. Due to the
high content of oxygen, bio-oil has a low heating value and high
viscosity, limiting the application to transportation fuels [4].
and furan over monometal Ni/SiO
NiFe/SiO [18]. Wang et al. used non-sulfided Ni/HZSM-5 to catalyze
phenol and got a high conversion (91.8%) [19]. The study by Tomishige
et al. showed that Ni–Pd/SiO (Ni/Pd = 7) performed a good yield to 2,
2
catalyst while 2-methylfuran over
2
2
5-bis (hydroxymethyl) tetrahydrofuran (96%) for the hydrogenation of
5-hydroxylmethyl furfural, which was super to Raney Ni and Pd/C [20].
Due to the complex of bio-oil, the catalysts used in HDO must be
universal for all of model compounds. To the best of our knowledge,
very few studies have been conducted on bimetallic catalysts used
in different model compounds under the same reaction conditions.
In this work, the catalytic activity of NiFe bimetallic catalyst was
evaluated by the HDO of furfuryl alcohol, benzyl alcohol (model
compounds of lignocellulose) and ethyl oenanthate (model of algae
and proper carbon chain length for jet fuel). Our study shows that
NiFe performs excellent catalytic activities on dehydration rather
than decarbonation or decarboxylation. Finally, higher heating value
and pH fuel are obtained by catalytic HDO of bio-oil, which confirm
the universality of NiFe catalyst.
The catalytic hydrodeoxygenation (HDO) is one of the efficient ways
to remove oxygen in upgrading bio-oil to fuel. The noble metal catalysts,
such as supported Pt, Pd, Rh, Ru [5–10], have high activities. The
,
sulfided NiMo and CoMo as the industrial hydrodesulfurization cata-
lysts, have been investigated in HDO reactions. However, they may
cause the contamination of bio-oil. Therefore, reduced supported tran-
sition metals catalysts, such as Ni, Mo, Co, Fe, Cu [11–14], have attracted
much attention due to their good catalytic performances. Recent studies
have shown that the bimetallic catalysts always have superior catalytic
properties than single metallic catalysts [15–17]. The study by Heeres et
2. Experimental
2.1. Catalyst synthesis and characterizations
2 3
al. found that 16 wt%–2 wt% NiCu/δ-Al O had the best activity for HDO
The NiFe/Al
co-impregnation, using an aqueous solution (20 ml de-iron water)
containing both metal precursors, Ni(NO · 6H O (AR, Aladdin) and
2 3
O catalyst was prepared by incipient wetness
⁎
Corresponding author. Tel./fax: +86 571 88871037.
E-mail address: jgw@zjut.edu.cn (J. Wang).
)
3 2
2
1566-7367/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.catcom.2013.06.037

S. Leng et al. / Catalysis Communications 41 (2013) 34–37
35
Fe(NO )
3 3
2
· 9H O (AR, Aladdin). Then, the aqueous solution was added
2 3
to the γ-Al O support (20–40 mesh, Wuke Biochemical Co. Ltd).The
loading of Ni was kept constant at 15.0 wt. %, while the Fe loading
was 5.0 wt. %. After impregnation, the catalyst was first dried overnight
at 80 °C and then calcined for 4 h at 600 °C in the muffle furnace.
Several physical techniques were employed to characterize the
structure of the NiFe/Al
XRD) for the sample was collected on an X'Pert PRO X-ray Diffract
meter (PANalytical), using Cu Ka radiation generated at 40 kV and
0 mA. The scans covered the range from 10 to 80°. Morphology
2 3
O catalysts. X-ray powder diffraction pattern
(
4
and size of the Ni–Fe clusters were characterized by transmission
electron microscopy (TEM, Tecnai G2 F30).
2
.2. Catalytic activity measurements
The vapor-phase conversions of furfuryl alcohol, benzyl alcohol,
ethyl oenanthate and bio-oil over the Ni–Fe catalyst were evaluated
in a tubular quartz reactor, which was heated by electricity. In each
run, a catalyst sample (size range: 40–60 mesh, 5 ml) was placed
at the center of the reactor tube (diameter = 7 mm, length =
4
00 mm) between two layers of quartz wool and pre-reduced in H
2
flow (40 ml/min, 99.999%,Shanghai) for 3 h at 400 °C. After reduc-
tion, a 0.03 ml/min flow of liquid (benzyl alcohol was pure, furfuryl
alcohol was diluted 10 times by benzene, ethyl oenanthate was diluted
Fig. 1. TEM images of fresh (a, b) and used (c, d) catalyst.
1
0 times by n-decane) was preheated at 230 °C and purged onto the
catalyst bed. The liquid feed was fed continuously from a peristaltic
pump (Baoding Lead Fluid Tech. Co. Ltd.) and vaporized into a H
while for used catalyst, the peaks of Ni and NiFe alloy were detected,
which was agree with TEM.
2
stream of 40 ml/min. The reaction products were analyzed by GC
out-line (Zhejiang Fuli Analytical Instrument Co. Ltd., 9790), using a
PEG-20 M capillary column and a FID detector. The product conversion
for each product was calculated as follows:
2 3
3.2. HDO of model systems over NiFe/γ-Al O catalyst
In this study, three different model systems were chosen to evalu-
ate the HDO over NiFe/γ-Al catalyst. These supports (γ-Al , ac-
tive carbon) alone do not catalyze three substrates. The conversions
over NiFe catalyst were higher than monometal ones probably due
to the synergistic effect of bimetallic active phases [21]. Through the
optimization of Ni/Fe ratio and loadings of metals supported on
O
2 3
2 3
O
mol of the inget feed− mol of the outget feed
Conversion ¼
ꢀ 100%
mol of the inget feed
3
. Results
2 3
γ-Al O , we found Ni/Fe = 3 and the loading of 15% Ni – 5% Fe
were the optimum values. The effect of temperature on conversions
and yields of these systems were shown in Fig. 3. At 300 °C, the con-
version of both furfuryl alcohol and benzyl alcohol was more than
3
.1. Catalyst characterizations
The physical properties of Al
2
O
3
and oxidized and reduced NiFe/
8
5%, while only about 15% for ethyl oenanthate. Therefore, the influ-
Al
support and NiFe/Al
sorption method (ASAP 2020, America) is 245, 184 and186 m /g. H
consumption, determined from H -TPR (HIDEN QIC-20), was only
.4 mmol gCat . Based on TEM observation, the average particle size
O
2 3
were shown in Table 1. The specific surface area of the γ-Al
2 3
O
ence of temperature on the conversion and yield of ethyl oenanthate
is much bigger than furfuryl alcohol and benzyl alcohol. The conver-
sion of furfuryl alcohol was all above 90% when the temperature is
2 3
O
determined by Barrett–Joyner–Halenda ad-
2
2
2
−
1
1
for NiFe particles was 4.8 nm (Fig. 1). It is seen that the uniform NiFe
particles were well dispersed on the support. The zoom-in image was
depicted in Fig. 1 (b). The energy spectrum analysis of one randomly
chosen particle (red circle) showed that it was composed with 16 wt%
Ni and 2 wt% Fe, which is nicely agreement with the experimental load-
ing ratio. But a little aggregation of metals was observed for the used
catalyst from TEM observations (Fig. 1 c, d). Due to high dispersion,
there were no peaks of Ni and NiFe for fresh catalyst [21] (Fig. 2),
Table 1
Physical properties of support and catalysts.
Support and
catalyst
Metal
H
2
consumption
Diameter
(nm)
BET
(m /g)
2
loadings
from H
2
-TPR
(
mmol gCat−1)
(mmol gCat−1)
Ni
Fe
Support
Oxidized 15Ni–5Fe
Reduced 15Ni–5Fe
—
—
—
—
245
184
186
2
2.10
0.625
0.656
1.40
—
—
Fig. 2. XRD characterizations of support, fresh catalyst and used catalyst.
4.8

36
S. Leng et al. / Catalysis Communications 41 (2013) 34–37
Fig. 3. Conversions and target product yields over NiFe catalyst at different tempera-
ture, atmosphere.
higher than 350 °C. However, the conversion of ethyl oenanthate
changes from 70.2% at 350 °C to 97.9% at 400 °C. From GC analysis
of tail gas, the main products of three different model compounds
are toluene, 2-methylfuran, and heptane. The yield of 2-methylfuran
increased from 53% to 88%, for toluene from 64 to 78% at the temper-
ature range from 300 to 400 °C, while for heptane was even larger,
from 0 to 49%. The conversions of ethyl oenanthate, benzene alcohol
and furfural alcohol over fresh NiFe catalyst are higher than the
sulphided CoMo [22], Ru-based [23] and Cu-based [24] catalysts,
respectively. In order to obtain good catalytic performance for each
compound in bio-oil, 400 °C was set as the proper reaction tempera-
ture for catalytic HDO of bio-oil.
The conversions and yields over NiFe bimetallic catalyst under
different flow speeds at 400 °C were shown in Fig. 4. At a low flow
speed (b0.10 ml/min), all the conversions were high (above 90%)
and stable. But when the flow speed was up to 0.15 ml/min, the
conversion of benzene alcohol still kept at a high value (N90.4%),
while conversions of the other two declined dramatically, at the
edge of inactivation (the deactivation rate exceeding 30%). The
influence of flow speeds on the yields showed the same rule with
the conversions. The bigger of flow speed, the lower conversions
and yields. Therefore, 0.1 ml/min was set as the proper flow speeds
for catalytic HDO of bio-oil.
Scheme 1. Proposed pathways of three substrates.
activated than C–C one under the investigated reaction conditions.
Of course, dependent on the specific oxygen-containing group, the
activation temperatures were different. The C–O in the carboxyl
group was activated more difficult than C–OH group, which can ex-
plain the effect of temperature on the conversion and yields of ethyl
oenanthate is much bigger than furfuryl alcohol and benzyl alcohol.
Therefore, NiFe bimetallic catalyst shows excellent catalytic proper-
ties for removing oxygen in three typical model compounds of
bio-oil. A more general model was shown that –OY group was
displaced by H atom actually.
3
.3. HDO of bio-oil over NiFe catalyst
The NiFe catalysts have been further used in catalytic HDO bio-oil
obtained from straw. The atomic H/C ratio is up to 2.15, but the
oxygen content is 47.59 wt % determined by element analysis. The
heating value of this bio-oil is 37.8 MJ/kg determined on a XRY-1A ox-
ygen bomb calorimeter, which is lower to fossil fuel (46.04 MJ/kg)
and mainly used in kitchens as liquefied gas. The pH of bio-oil was
about 6.65(± 0.05). After HDO of bio-oil on over NiFe bimetallic catalyst
at 400 °C and atmospheric pressure, the pH was 7.5 and the heating
value was 43.9 MJ/kg close to the value of fossil diesel (46.04 MJ/kg).
From the product analysis of the catalytic HDO of three different
model compounds of bio-oil, it was found that the main products
were deoxidized ones, resulted by C–O cleavage rather than C–C
cleavage (see Scheme 1). Independent on the groups (furan ring,
benzene ring and straight-chain paraffin), the C–O bond was easier
4
. Conclusions
NiFe bimetallic catalyst has an excellent catalytic HDO property of
three typical model compounds of bio-oil. The excellent catalytic
properties of NiFe bimetallic catalysts were attributed to the forma-
tion NiFe alloy confirmed from XRD and TEM characterizations.
From the product analysis, we proposed that the major reaction path-
way is the cleavage of C–O cleavage rather than C–C under the inves-
tigated reaction conditions. After the catalytic HDO of bio-oil over
NiFe bimetallic catalyst, the heating value changes from 37.8 to
4
3.9 MJ/kg, the pH changes from 6.65 to 7.50.
Acknowledgements
This work was supported by National Basic Research Program of
China (973 Program) (2013CB733501), the National Natural Science
Foundation of China (Nos. 21176221, 21136001 and 21101137), Zhejiang
Provincial Natural Science Foundation of China (No. R4110345), the New
Fig. 4. Conversions and target product yields over NiFe catalyst under different flows at
400 °C, atmosphere.

S. Leng et al. / Catalysis Communications 41 (2013) 34–37
37
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