Tandem Hydrogenolysis–Hydrogenation of Lignin-Derived Oxygenates over Integrated Dual Catalysts with Optimized Interoperations

Article abstract of DOI:10.1002/cssc.201902029

The efficient hydrodeoxygenation (HDO) of lignin-derived oxygenates is essential but challenging owing to the inherent complexity of feedstock and the lack of effective catalytic approaches. A catalytic strategy has been developed that separates C?O hydrogenolysis and aromatic hydrogenation on different active catalysts with interoperation that can achieve high oxygen removal in lignin-derived oxygenates. The flexible use of tungsten carbide for C?O bond cleavage and a nickel catalyst with controlled particle size for arene hydrogenation enables the tunable production of cyclohexane and cyclohexanol with almost full conversion of guaiacol. Such integration of dual catalysts in close proximity enables superior HDO of bio-oils into liquid alkanes with high mass and carbon yields of 27.9 and 45.0 wt %, respectively. This finding provides a new effective strategy for practical applications.

Full text of DOI:10.1002/cssc.201902029

Accepted Article
Title: Tandem hydrogenolysis–hydrogenation of lignin-derived
oxygenates over integrated dual catalysts with optimized
interoperations
Authors: Youzhu Yuan, Huihuang Fang, Weikun Chen, Shuang Li,
Xuehui Li, Xinping Duan, and Linmin Ye
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: ChemSusChem 10.1002/cssc.201902029
Link to VoR: http://dx.doi.org/10.1002/cssc.201902029
A Journal of
www.chemsuschem.org

10.1002/cssc.201902029
ChemSusChem
RESEARCH ARTICLE
Tandem hydrogenolysis–hydrogenation of lignin-derived
oxygenates over integrated dual catalysts with optimized
interoperations
Huihuang Fang,[a] Weikun Chen,[a] Shuang Li,[b] Xuehui Li,[c] Xinping Duan,[a] Linmin Ye,[a] and Youzhu
Yuan*[a]
Abstract: The efficient hydrodeoxygenation (HDO) of lignin-derived
oxygenates is essential but challenging due to the inherent
complexity of feedstock and the lack of effective catalytic
approaches. In this study, we present a catalytic strategy that
separates C–O hydrogenolysis and aromatic hydrogenation on
different active catalysts with interoperation that can achieve high
oxygen removal in lignin-derived oxygenates. The flexible use of
tungsten carbide for a C–O bond cleavage and Ni catalyst with
controlled particle size for arene hydrogenation enables the tunable
production of cyclohexane and cyclohexanol with almost guaiacol
conversions. Such integration of dual catalysts with closed proximity
performs the superior HDO activity of actual bio-oils into liquid
alkanes with a high mass and carbon yield of 27.9 and 45.0 wt%,
respectively. This finding provides a new effective strategy for
practical applications.
hydrodeoxygenation (HDO) process is viable for extensive
oxygen removal in the final upgrading of bio-oils and is a key
research subject that has attracted tremendous interests in
recent years.[1c,5b,6] However, the inherent complexity and high
oxygen content of bio-oil components pose a challenging task
for current hydroprocessing catalysts, which enable the lignin-to-
chemical cycle to achieve high-yield performance and cost-
effectiveness.
As popular hydrogenation catalysts, supported metallic
catalysts are commonly used catalytic materials in typical HDO
processes.[3a,5b,7] Numerous studies have shown that supported
noble metal catalysts (e.g., Pt, Pd, Ru, and Rh) possess
promising HDO activity primarily in lignin-derived platform
chemicals, such as anisole and guaiacol, with considerable
catalyst lifetimes.[3a,8] The high cost of noble metals with
moderate performance motivates the development of
inexpensive metals, such as Ni, Cu, and Fe, in HDO reactions.[9]
Such metals have been proven to activate H2. However, a
typical HDO reaction has been realized in a case with a two-step
process involving the hydrogenation of unsaturated C=C and
Introduction
The catalytic transformation of lignocellulose into sustainable
fuels and chemicals is an important process that exhibits
potential in fossil energy substitution.[1] Longstanding interest in
lignin utilization has been translated into limited commercial
availability due to the lack of innovative catalysts and high-yield
practical strategies.[2] At present, several approaches have been
developed for lignin conversion, including hydrolysis, enzymatic
treatment, catalytic depolymerization, and thermochemical
conversion.[3] Among these approaches, rapid pyrolysis is the
leading and most cost-effective process for the direct production
of ungradable bio-oils from lignocellulose.[4] Nevertheless, such
bio-oils are far from commercial use in chemical production and
transportation fuels because the rapid pyrolysis results in the
formation of complex mixtures of oxygenated compounds,
including carbonyls, acids, furans, and complex (alkyl)guaiacols,
containing high oxygen content with high viscosity, low energy
C=O bonds and deoxygenation by using
a C–O bond
cleavage.[10] Metal sites alone are incompetent for efficient
hydrogenation and deoxygenation and constantly lead to poor
HDO performance.
Bifunctional metal-acid catalysts have emerged and display
remarkably enhanced HDO activities.[3c,11–14] Given that metal
sites facilitate the activation of hydrogen, the acidic sites on the
supports are crucial for deoxygenation. Zhao et al.[12] made
impressive progress on designing metal–acid bifunctional sites,
such as Ni/SiO2 and Ni/HZSM-5, for the efficient conversion of
phenolic bio-oil into alkanes. Xia et al.[3c] used a Pt/NbOPO4
catalyst for the production of alkanes from raw lignocellulose
whose high activity originated from the synergistic effect
between Pt, acidic sites, and NbOx species. Similarly, Pd/m-
MoO3–P2O5/SiO2 was devoted to the HDO of water-insoluble
bio-oils[11d]. Recently, Ju et al.[6b] used Pt–alumina/zeolite with
optimized acid/metal interaction, which can catalyze the HDO of
bio-oxygenates into hydrocarbons. In addition, Al2O3, TiO2, ZrO2,
and zeolites have also been utilized in preparing bifunctional
catalysts.[13] Nevertheless, the balance between metal–acid sites
is unfeasible to regulate, and the excess incorporation of strong
acid sites constantly causes cracking, transalkylation,
polymerization, coke formation, and other undesirable side
reactions.[14]
density,
and
chemical
instability.[5]
The
catalytic
[a]
H. Fang, W. Chen, Dr. X. Duan, Dr. L. Ye, Prof. Dr. Y. Yuan*
State Key Laboratory of Physical Chemistry of Solid Surfaces,
National Engineering Laboratory for Green Chemical Productions of
Alcohols-Ethers-Esters and iChEM, College of Chemistry and
Chemical Engineering, Xiamen University, Xiamen 361005, China
E-mail: yzyuan@xmu.edu.cn
[b]
[c]
Prof. Dr. S. Li
School of Chemical Engineering, Northwest University, Xi’an,
Shaanxi, 710069, China
Prof. Dr. X. Li
Here, we present an integrated strategy that separates the C–
O bond cleavage and aromatic hydrogenation on different active
catalysts through a complementary interoperation of dual
School of Chemistry and Chemical Engineering, Pulp & Paper
Engineering State Key Laboratory of China, South China University
of Technology, Guangzhou 510640, China
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/cssc.201902029
ChemSusChem
RESEARCH ARTICLE
Cyclohexane
Benzene
Phenol
Cyclohexenol
Cyclohexanol
Cresols
Cyclohexanone
Anisole Others
100
80
60
40
20
0
Ni/CNT
1.25C@CS
1.25C@CS + Ni/CNT
W
W
523
Reaction temperature / K
538
548
508
573
Scheme 1. Highly efficient HDO of lignin-derived oxygenates via the
integration of active catalysts for C–O bond cleavage and aromatic
hydrogenation.
Figure 1. Catalytic performance of guaiacol HDO on several catalysts at
different temperatures. Reaction conditions: P = 3.0 MPa, H2/GUA molar ratio
= 50, liquid guaiacol flow = 0.61 g h−1; catalyst weight, 200 mg for WxC@CS
and 50 mg for Ni/CNT with 5.6 nm of Ni particle size, T = 508–573 K.
catalysts for the efficient HDO of lignin-derived oxygenates and
pyrolysis bio-oils (Scheme 1). The cleavage of inert Caryl–OR
bonds to phenolics is mainly achieved on tungsten carbides
(WxC@CS, CS: carbon sphere), whereas aromatic rings are
saturated by Ni catalysts, followed by a further aliphatic C–O
bond cleavage of the resultant (alkyl)cyclohexanols on tungsten
carbides or nickel catalysts. As a result, almost 100% of
conversions of lignin-derived oxygenates with high efficiency can
be achieved. High (alkyl)cyclohexanol or (alkyl)cyclohexane
yields are obtained with different integrated manners of dual
catalysts. The flexible use of integrated dual catalysts can
catalyze the HDO of raw lignin bio-oils with almost-oxygen
removal, reaching a total mass yield of up to 27.9% and carbon
yield of up to 45.0%.
unimpressive with poor selectivity, thereby indicating
a
competing aromatic reduction and C–O bond hydrogenolysis.
Increasing the reaction temperature improved the product yield
slightly. However, the presence of ring-saturated products, such
as cyclohexanol, was still observed at low temperatures, thereby
indicating that the Ni catalyst is a good candidate active for
arene reduction.
The integration of these two components is expected to
exhibit satisfied performance. The morphology of integrated dual
catalysts shown in Fig. S2a demonstrated that Ni/CNTs were
compacted on the outer surface of WxC@CS. WxC particles
were well dispersed in the carbon spheres, whereas Ni particles
were deposited on the CNTs from the EDX mapping and
element analysis (Figs. S2e–S2f). The integration of dual
catalysts showed no changes in active compositions, as
observed in the XRD patterns (Fig. S3). Guaiacol HDO
performance was remarkably enhanced by the combination of
these two catalysts with increasing temperature and achieved
almost oxygen removal with a cyclohexane up to 92.3% at 573 K
as shown in Fig. 1. In fact, considerable efforts have been made
to enhance the HDO performance by using Ni-based catalysts
with optimized supports in previous reports.[16] For example,
Bykova et al.[16a,b] used SiO2–ZrO2 stabilized Ni and Ni–Cu
catalysts (Ni: 37–58 wt.%) for HDO of guaiacol under 593 K with
17 MPa H2, obtaining 63.9% yield of cyclohexane. Similar
catalyst were reported by Zhang[16c,d] with a guaiacol conversion
rate of 6.8 10–6 mol g–1 s–1 at 613 K. Zhao at al.[12a] employed 20
wt.% Ni/ZSM-5 for HDO of guaiacol at 523 K and 4 MPa H2,
achieving 100% conversion with 74% selectivity of cycloalkanes.
Ni/SiO2–Al2O3 displayed a 45.0% yield of cyclohexane at 623
K.[16e] Thereby the integrated dual catalysts in our case showed
superior performance compared with these results, which
reveals the distinct advantage of separating C–O bond
hydrogenolysis and arene reduction over two active catalysts.
Having identified the scope of the integrated dual catalysts for
efficient HDO reactions, we also tested the HDO performance of
various aromatics, such as veratrole and dimethoxyphenol, as
shown in Table S1. Such compounds are typical in upgradable
Results and Discussion
The use of one bifunctional catalyst in the highly efficient
multistep tandem reaction is challenging. For lignocellulose HDO,
the critical difficulty originates from the competing ring saturation
and C–O bond hydrogenolysis. We selected tungsten carbide as
an active catalyst for C–O bond hydrogenolysis. Our previous
works have found that optimized WxC@CS with a preferable
surface C/W atomic ratio of approximately 7–8 showed the best
hydrogenolysis of guaiacol and other aromatic ethers to
phenolics.[15] However, hydrogenation of phenolics, followed by
further C–O bond cleavage, could not be achieved even when
the reaction temperature was increased (Fig. 1, second column),
thus leading to incomplete oxygen removal, which is always
required for the utilization of ungradable bio-oils and complicated
lignin-derived oxygenates. Our analysis clarified that further
aromatic reduction is thermodynamically feasible for HDO
reactions because a complete C–O bond cleavage is driven at
low temperatures (Fig. S1). Nickel is a typical non-noble metal
with excellent capability for H2 activation and constantly used in
hydrogenation reactions.[9a–9c] Fig. 1 (first column) shows that the
mono-Ni catalyst on carbon nanotubes (Ni/CNTs) is active for
guaiacol HDO. However, the catalytic performance was
This article is protected by copyright. All rights reserved.

10.1002/cssc.201902029
ChemSusChem
RESEARCH ARTICLE
lignin-derived oxygenates with high oxygen content. The
cleavage of aryl C–O bond in the first step can be achieved by
WxC@CS (Table S2). In combination with the hydrogenation
function in the Ni catalyst, almost-full conversion of substrates
with nearly 100% deoxygenation could be obtained to produce
oxygen-free hydrocarbons (mainly cyclohexane). Note, the
optimized reaction temperatures were remarkably lower than the
cases that used WxC@CS alone. The overall yields ranged from
87.9% to 100.0% with a decreased temperature of 25–50 K.
Clearly, the optimized reaction temperatures essentially
maintained a highly efficient transformation with increased
energy savings over the integrated dual catalyst.
cleavage and hydrogenation were mainly achieved with
WxC@CS and Ni/CNT, respectively. The two processes on the
integrated dual catalysts drove each other to perform their adept
functions as much as possible. Analysis of the Arrhenius plots
derived the apparent activation energy (Ea) shown in Fig. 2b to
correlate the activities. The integration of dual catalysts
displayed a considerably lower Ea at 56.7 kJ mol−1 compared
with the single WxC@CS and Ni catalyst. Chemisorption results
(Table S4) showed enhanced H2 absorption with similar CO
absorption over dual catalysts, thereby indicating that the Ni
incorporation promoted hydrogen activation and aryl C–O bond
cleavage over tungsten carbides. These results are
corresponding to the interoperation of the dual catalysts.
To understand the roles of the two catalysts further, the
product synthesis rate was investigated as a function of dual
catalyst mass ratio (Fig. 2a). The use of Ni/CNT alone obtained
a lower synthesis rate of eventual cyclohexane compared with
that of intermediate phenol. This result confirmed incomplete
deoxygenation and arene hydrogenation. The increase in the
Ni/CNT/WxC@CS mass ratio linearly increased the rates of
phenol and cyclohexane formation in the initial stage.
Interestingly, the slope of the increasing rate for cyclohexane
was higher than that of phenol, thereby indicating the greater
enhancement of further phenol transformation when the Ni
catalyst was incorporated. For mass ratios greater than 0.125,
the rates slowed down and generally reached the same constant
(16.8 10–6 mol s–1 gcat–1) due to full intermediate phenolic
conversion. Thus, the match activity for integrated dual catalysts
is essential to achieve the best performance. To observe the
roles of the two catalysts directly, we evaluated the conversions
of intermediate phenol and cyclohexanol. Ni/CNT showed high
activity of phenol hydrogenation, but cyclohexanol remained
(Table S3). Deoxygenation of cyclohexanol was constantly
achieved by using acid-catalyzed dehydration to form
cycloalkane, followed by metal-catalyzed hydrogenation to
cycloalkane.[12] By contrast, hydrogenolysis of cyclohexanol was
easily achieved by WxC@CS even though no activity was
observed in phenol conversion. In our study, efficient C–O bond
The integration manner of different active catalysts was crucial
in product selectivity (Fig. 3). The use of
configuration with WxC@CS downstream from Ni/CNT provided
wide product distribution (Fig. 3c). The formation of
a dual-bed
a
cyclohexane was due to the further C–O bond cleavage of
cyclohexanol by downstream WxC@CS based on the catalytic
function of Ni/CNT. The increasing phenol selectivity suggested
that certain remaining guaiacol were then transformed with
tungsten carbides. The catalytic behavior changed when the
streams of the two catalysts were reversed, as shown in Fig. 3d.
High selectivity to cyclohexanol could be obtained with almost
guaiacol conversion. No cyclohexenols were observed in this
case, thereby suggesting that the responsibility of C–O bond
hydrogenolysis over WxC@CS contributed to the enhanced
capability for arene reduction over Ni/CNT. Furthermore, the
integration of dual catalysts with closed proximity remarkably
improved the formation of cyclohexane and achieved high
oxygen removal (Figs. 3e and 3f).
Motivated by the integration manners, we attempted to yield
alternative chemicals directly in one reaction by tuning the active
catalysts, which presumably provided the potential for the direct
production of attractive chemicals from raw lignin-derived
oxygenates. Previous reports have demonstrated that Ni is
Cyclohexane
Benzene
Phenol
Cycolhexenols
Cyclohexanol
Anisole
Cyclohexanone
Others
a
b
3
2
100
80
60
40
20
0
18
15
12
9
Ni/CNT
83.4 kJ/mol
1
Phenol
Cyclohexane
WxC@CS+Ni/CNT
0
56.7 kJ/mol
-1
-2
-3
6
Ni/CNT
WxC@CS
145.5 kJ/mol
3
0
0.0 0.1 0.2 0.3 0.4 0.5 0.
Ni/CNT / WxC@CS mass ratio
6
1.68 1.75 1.82 1.89 1.96 2.03
1000/T / K
WxC@CS
Ni/CNT
Figure 2. (a) Synthesis rate of the product in the guaiacol HDO of integrated
dual catalysts with closed proximity as a function of the Ni/CNT/WxC@CS
mass ratio. Reaction conditions: P = 3.0 MPa, H2/GUA molar ratio = 50, liquid
guaiacol flow = 1.22 g h−1, catalyst weight: 200 mg for WxC@CS and 0–100
mg for Ni/CNT with 5.6 nm of Ni particle size, T = 573 K. Note: The synthesis
rate of phenol was calculated on the basis of the total products from phenol as
an intermediate. (b) Arrhenius plots of the reaction rate {Ln (r)} versus 1/T for
guaiacol conversion over Ni/CNT (blue line), WxC@CS (black line), and
integrated dual catalysts (red lines).
F
E
B
D
A
C
Figure 3. Effect of integration manner of different catalysts on the
performance. (a)–(f) Using 200 mg for WxC@CS and/or 50 mg for Ni/CNT; Ni
particle size: (a)–(e) 20.5 nm and (f) 5.6 nm. Reaction conditions: P = 3.0 MPa,
H2/GUA molar ratio = 50, liquid guaiacol flow = 0.61 g h−1, T = 573 K.
This article is protected by copyright. All rights reserved.

10.1002/cssc.201902029
ChemSusChem
RESEARCH ARTICLE
readily used for size control and displays structure sensitivity to
HDO reaction.[9] Large particles were active for hydrogenation of
the aromatic ring, whereas decreasing the particle size was
preferable for deoxygenation. The Ni/CNT catalysts with
cyclohexane selectivity was achieved when the Ni/CNT catalyst
had a particle size of 5.6 nm. By further increasing the Ni particle
size, conversions reduced slightly and cyclohexane selectivity
remained high. Notably, the rapid conversion of intermediates on
different particle size distributions were successfully synthesized, each catalyst remarkably enhanced HDO activity due to the
as shown in Fig. S4a, and the particle sizes were determined
using the TEM images and XRD patterns based on the Scherrer
equation (Fig. S4b). These samples represented very different
average particle sizes ranging from 5.0 nm to 20.0 nm. Further
H2-TPR profiles (Fig. S5) revealed the reduction information of
as-calcined Ni/CNT samples, implying that all Ni oxide species
could be reduced based on our pretreatment procedure.[17] Fig.
S6 shows the HDO performance of guaiacol over Ni/CNT
catalysts. The conversion clearly decreased with the increase in
particle size. The decreased cyclohexane selectivity suggested
the suppression of deoxygenation capability, and only trace
cyclohexane was formed in the case of large particles (20.5 nm).
When WxC@CS was packed in the upper layer of Ni/CNT (Fig.
4a), guaiacol conversion clearly increased, and cyclohexanol
selectivity was considerably enhanced with increasing Ni particle
size. This finding was due to the role-sharing of the C–O bond
cleavage on tungsten carbides that enabled Ni to perform
optimized hydrogenation. The combination of upstream tungsten
carbide and downstream Ni/CNT with large particles was
preferable for the efficient production of cyclohexanol, which was
also an important intermediate for the chemical production of
cyclohexanone and adipic acid. The interoperation of dual
catalysts was pronounced when they were mixed with closed
proximity (Fig. 4b). Complete guaiacol conversion with 92.4%
thermodynamic driving force, which was confirmed when an
aged WxC@CS with poor performance was used as one catalyst
(Table S5). As shown in Scheme S1 for the possible reaction
sequence, the enhanced performance was caused by the
separated catalytic processes. Firstly, WxC@CS was mainly
responsible for Ph–OCH3 bond hydrogenolysis, followed by the
hydrogenation of phenol to cyclohexanol over the Ni catalyst.
Then the cleavage of the aliphatic C–O bond with hydrocarbon
formation was readily achieved by WxC@CS or Ni particles.
Given that the short catalyst lifetime is a common issue in HDO
reactions, we also investigated the catalyst stability in guaiacol
HDO under similar reaction conditions. Fig. 4c presents that the
integrated dual catalysts (200 mg WxC@CS and 50 mg
Ni/CNT(5.6 nm)) were stable in the HDO of guaiacol, and the
deoxygenation efficiency remained unchanged after 150 h of
reaction with the main product being cyclohexane. The structure
of the used integrated dual catalysts composed of 200 mg
WxC@CS and 50 mg Ni/CNT(5.6 nm) with a closed proximity
was characterized by SEM, STEM, XRD and Ni particle
estimation. The results are summarized in Fig. S7. As shown in
Figs. S7a, a similar morphology of the integrated dual catalysts
was observed by SEM. Further, insignificant changes of
diffraction lines due to Ni species are shown for the used Ni/CNT
(Fig. S7b), indicating the agglomeration of Ni nanoparticles
might be limited after 150 h reaction. Nonetheless, STEM image
in Fig. S7c revealed that a slight agglomeration of some Ni
particles occurred after the reaction for 150 h. The estimation of
Ni particle size distribution in Fig. S7d indicated that the average
Ni particle size was slightly increased from 5.6 nm to 7.5 nm
after run for 150 h. However, the integrated dual catalysts could
keep at a high performance in terms of guaiacol conversion and
cyclohexane selectivity even if the Ni particle size was larger
than 10 nm as shown in Fig. 4b. The result is presumably due to
the remarkable interoperation of dual catalysts. The result is
presumably due to the remarkable interoperation of dual
catalysts. This finding shows a great potential of the integrated
dual catalysts for practical applications.
a
b
Cyclohexane
Benzene
Cyclohexanol
Cyclohexanone
Phenol
Others
Cyclohexane
Conv.
Phenol
Benzene
Others
Conv.
100
100
80
60
40
20
0
80
60
40
20
0
A
B
C
D
A
B
C
D
c
100
Guaiacol conversion
Cyclohexane selectivity
80
60
40
20
0
On the basis of the above discussion, HDO of actual bio-oil
was performed to determine the efficiency of integrated dual
catalysts. The bio-oil from rapid pyrolysis was a brownish black
liquid with 51.3 and 41.3 wt% carbon and oxygen content,
respectively (Table S6). The compounds in the bio-oil were
further identified via gas chromatography–mass spectrometry
(GC–MS), as shown in Fig. S8a. Results showed that the bio-oil
contained over 35 lignin-derived oxygenates, including acids,
alcohols, furans, and mainly complex guaiacols (Fig. S8b). Table
S7 lists the major groups of compounds involving simple
oxygenates (e.g., acids, esters, alcohols, and ketones
aldehydes), furans, and phenolics (e.g., phenols, guaiacols,
syringols) at 35.4, 11.0, and 51.6 wt%, respectively. These
0
20
40
60
80
100
120
140
Time on stream / h
Figure 4. Catalytic performance for guaiacol HDO over (a) dual-bed
configuration with Ni/CNT packed below WxC@CS and (b) integration of dual
catalysts with closed proximity. The average Ni particle size in Ni/CNT
catalyst: A. 5.6 nm, B. 10.2 nm, C. 13.5 nm, D. 20.5 nm. (c) Stability of
integrated dual catalysts in the guaiacol HDO reaction. Reaction conditions: P
= 3.0 MPa, H2/GUA molar ratio = 50, liquid guaiacol flow = 0.61 g h−1, catalyst
weight = 200 mg for WxC@CS and 50 mg for Ni/CNT, and T = 573 K.
This article is protected by copyright. All rights reserved.

10.1002/cssc.201902029
ChemSusChem
RESEARCH ARTICLE
compounds were consistent with those reported in rapid
pyrolysis.[18]
0
0
Table 1 compares the HDO performance of the actual bio-oil
over different catalysts, and the results reveal that the major
products were alkanes, cycloalkanes, alkylbenzenes, and
alkylphenolics. The mono-Ni/CNT catalyst obtained a very low
mass yield of total liquid alkanes (4.8 wt%) with certain
alkylphenolics as products (Entry 1). By contrast, WxC@CS
showed nearly no activity for liquid (cyclo)alkane formation but
obtained a 5.2 wt% mass yield of alkylphenolics (Entry 2). These
compounds were mainly (alkyl)phenols as identified by GC–MS
(Fig. S9). Results were consistent with the HDO products of
lignin platform compounds over WxC@CS. With the integration
of a small amount of Ni/CNT and WxC@CS under closed
proximity (Entry 3), the mass yield of total liquid alkanes
increased considerably and reached 13.6 wt%. Alkylphenolics
were still observed in this case, and the mass yield increased to
7.0 wt%, although the Ni/CNT/WxC@CS mass ratio was the
same as those in HDO of simple lignin-derived compounds, as
mentioned above. This finding was likely due to the insufficient
hydrogenation function over the Ni/CNT catalyst in the HDO of
the actual bio-oil. When more active Ni/CNT for hydrogenation
was provided by further increasing the mass ratio (Entry 4), the
total conversion of the actual bio-oil was obtained with a
production of 27.9 wt% total liquid alkanes (Fig. S10). This result
was significantly higher than that of Entry 3. The obtained
alkanes included 0.2 wt% pentane, 0.9 wt% hexane, 9.9 wt%
alkylcycloepentanes, and 16.5 wt% alkylcyclohexanes. The
production of linear alkanes and alkylcyclopentanes suggested
that HDO of furans and linear oxygenates from (hemi)cellulose
was achieved. This finding was consistent with earlier reports.
Overall, a 45 wt% of total carbon yield was obtained. Recently,
Pt–Al2O3/HZSM-5 given a 77.27% conversion with 53.63%
hydrocarbon selectivity in HDO of eugenol and exhibited activity
in real bio-oil.[6b] A two-stage catalytic reactor was performed
using Ru/C-Pt/ZrP for HDO of bio-oil, producing totally 30%
carbon yield.[19] A significant contribution was achieved by Xia et
15
30
45
60
75
90
105
120
135
15
30
45
60
75
90
105
120
135
Ph-OMe
R-C=C-R
Aromatic groups
8
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
-1
H (ppm)
H (ppm)
Figure 5. 2D NMR spectra of the actual bio-oil (a) and obtained liquid products
(b). The insets show the images of mixtures before and after HDO reaction.
al.[3c] that raw wood sawdust could be converted into liquid
alkanes with 28.1% mass yield by using Pt/NbOPO4 catalyst.
Most alkanes were produced from (hemi)cellulose and the mass
yield of (alkyl)cyclohexanes converted from lignin was only 5.1%.
Further, Pd/m-MoO3–P2O5/SiO2 was used in HDO of water-
insoluble bio-oil, obtaining total liquid alkanes with 29.6% and
46.3% of mass and carbon yields, respectively.[11d] Therefore,
our result is comparable to the investigations on catalytic
performance over noble metal catalysts.
To demonstrate the clear advantage of the interoperation of
integrated dual catalysts, we measured the 2D HSQC NMR
spectra of the actual bio-oil and the obtained products (Fig. 5).
The actual bio-oil displayed a wide distribution of compounds
with typical aryl C–O bonds, C=C bonds, and aromatic functional
groups (Fig. 5a). However, the obtained products showed
centralized signals, which were assigned to the saturated C–H
bond, thus revealing the almost-conversion of bio-oils into
alkanes (Fig. 5b). The brownish black bio-oil became a
transparent liquid after reaction, providing an additional evidence
of the HDO efficiency (inset in Fig. 5). Specifically, oxygen
content was reduced from 41.3 wt% of the bio-oil to 3.7 wt% of
the obtained liquid (Table S6), indicating an almost-oxygen
Table 1. HDO of actual bio-oil over mono Ni/CNT, WxC@CS, and integrated
dual catalysts with closed proximity.
Guaiacol
Anisole
0.7
Veratrole
Dimethoxyphenol
0.6
Bio-oil
Phenetole
Phenol
Product
Mass yielda / carbon yieldb (wt% / wt%)
0.5
0.4
0.3
0.2
0.1
0.0
Entry 1
Entry 2
Entry 3
Entry 4
Pentane
Hexane
0.1 / 0.2
0.3 / 0.5
1.2 / 1.8
2.3 / 3.5
0.2 / 0.3
0.7 / 1.0
4.8 / 7.0
–
–
–
–
0.1 / 0.2
0.4 / 0.8
5.9 / 9.5
7.2 / 10.8
0.1 / 0.2
7.0 / 10.6
13.6 / 21.5
0.2 / 0.3
0.9 / 1.4
9.9 / 15.9
16.5 / 26.7
0.4 / 0.7
–
Ni/CNT
Alkylcyclopentanes
Alkylcyclohexanes
Alkylbenzenes
Alkylphenolics
Total liquid alkanes
0.1 / 0.2
5.2 / 7.7
–
WxC@CS
Ni/CNT + WxC@CS
27.9 / 45.0
1.0
1.2
1.4
Molar H/C
1.6
1.8
2.0
a Based on the mass of the actual bio-oil and b based on the mass of carbon in
the actual bio-oil. Entry 1: 100 mg Ni/CNT, Entry 2: 200 mg WxC@CS, Entry 3:
integrated dual catalysts (200 mg for WxC@CS and 50 mg for Ni/CNT), Entry
4: integrated dual catalysts (200 mg for WxC@CS and 100 mg for Ni/CNT).
Reaction conditions: P (H2) = 3.0 MPa, T = 598 K, H2 flow = 125 mL/min, and
liquid velocity = 0.008 mL/min.
Figure 6. van Krevelen plot for the elemental compositions of raw reactants
and the obtained products after HDO upgrading with various catalysts. The
orange, blue and green points represent the compositions of products
obtained via different catalysts.
This article is protected by copyright. All rights reserved.

10.1002/cssc.201902029
ChemSusChem
RESEARCH ARTICLE
removal. The H/C atomic ratio was approximately 1.97 which is
closed to the atomic ratio of CnH2n, indicating the major products
of cycloalkanes. It is worth noting that the compositions of liquid
alkanes were similar to those of the conventional fuel oil shown
in Table S6.[4,20] The van Krevelen plot was used to summarize
the HDO efficiency of lignin-derived oxygenates and bio-oil in
these catalysts (Fig. 6). A deep removal of oxygen content was
achieved by using the integrated dual catalysts, whereas the use
of mono Ni/CNT and WxC@CS showed incomplete
deoxygenation and hydrogenation. Therefore, the integrated
Keywords: Lignin-derived oxygenates • Hydrodeoxygenation •
Dual catalysts • Tungsten carbides • Nickel catalysts
[1]
a) G. W. Huber, S. Iborra, A. Corma, Chem. Rev. 2006, 106, 4044; b) C.
O. Tuck, E. Perez, I. T. Horvath, R. A. Sheldon, M. Poloakoff, Science
2012, 337, 695; c) C. Z. Li, X. C. Zhao, A. Q. Wang, G. W. Huber, T.
Zhang, Chem. Rev. 2015, 115, 11559.
[2]
[3]
a) M. Zaheer, R. Kempe, ACS Catal. 2015, 5 1675; b) M. V. Galkin, J.
S. M. Samec, ChemSusChem 2016, 9, 1544.
a) H. M. Wang, J. Male, Y. Wang, ACS Catal. 2013, 3, 1047; b) B. E.
Dale, R. G. Ong, Biotechnol. Prog. 2012, 28, 893; c) Q. N. Xia, Z. J.
Chen, Y. Shao, X. Q. Gong, H. F. Wang, X. H. Liu, S. F. Parker, X. Han,
S. H. Yang, Y. Q. Wang, Nat. Commun. 2016, 7, 11162; d) Z. W. Cao,
J. Engelhardt, M. Dierks, M. T. Clough, G. H. Wang, E. Heracleous, A.
Lappas, R. Rinaldi, F. Schuth, Angew. Chem. Int. Ed. 2017, 56, 2334.
S. Czernik, A. V. Bridgwater, Energy Fuels 2004, 18, 590.
dual catalysts achieved
a
remarkable interoperation of
hydrogenation and C–O bond hydrogenolysis and possessed
excellent catalytic performance for the simultaneous HDO of
lignin-derived oxygenates and actual bio-oil into liquid alkanes.
[4]
[5]
a) D. Mohan, C. U. Pittman, P. H. Steele, Energy Fuels 2006, 20, 848;
b) M. Saidi, F. Samimi, D. Karimipourfard, T. Nimmanwudipong, B. C.
Gates, M. R. Rahimpour, Energy Environ. Sci. 2014, 7, 103.
Conclusions
[6]
a) J. Zakzeski, P. C. A. Bruijinincx, A. L. Jongerius, B. M. Weckhuysen,
Chem. Rev. 2010, 110, 3552; b) C. Ju, M. R. Li, Y. M. Fang, T. W. Tan,
Green Chem. 2018, 20, 4492; c) G. H. Wang, Z. W. Cao, D. Gu, N.
Pfander, A. C. Swertz, B. Spliethoff, H. J. Bongard, C. Weidenthaler, W.
Schmidt, R. Rinaldi, F. Schuth, Angew. Chem. Int. Ed. 2016, 55, 8850;
d) L. Offner-Marko, A. Bordet, G. Moos, S. Tricard, S. Rengshausen, B.
Chaudret, K. L. Luska, W. Leitner, Angew. Chem. Int. Ed. 2018, 57,
12721.
A catalytic strategy for the efficient HDO of lignin-derived
oxygenates is successfully developed by separating the
functions of C–O bond cleavage and aromatic hydrogenation on
different active catalysts via interoperation. Tungsten carbide
can effectively perform C–O bond hydrogenolysis, and Ni is
mainly responsible for arene hydrogenation, followed by further
C–O bond cleavage. Thus, almost 100% conversion of various
oxygenates is obtained with decreasing reaction temperatures.
Product distribution can be tuned by using the integration
manners and active catalysts. High cyclohexane selectivity can
be achieved by using the integrated dual catalysts with closed
proximity (87.9%–100.0%). The control of the Ni particle size
with downstream Ni/CNT plays a crucial role in the suppression
of partial C–O bond cleavage that obtains high cyclohexanol
selectivity. As for the actual pyrolysis bio-oil feedstock, the
integrated dual catalysts show a state-of the-art catalytic
performance for the production of liquid alkanes with a total
carbon yield of 45.0% and mass yield of 27.9%.
[7]
[8]
D. A. Ruddy, J. A. Schaidle, J. R. Ferrell III, J. Wang, L. Moens, J. E.
Hensley, Green Chem. 2014, 16, 454.
a) J. Wildschut, F. H. Mahfud, R. H. Venderbosch, H. J. Heeres, Ind.
Eng. Chem. Res. 2009, 48, 10324; b) T. Nimmanwudipong, C. Aydin, J.
Lu, R. C. Runnebaum, K. C. Brodwater, N. D. Browning, D. E. Block, B.
C. Gates, Catal. Lett. 2012, 142, 1190; c) Y. C. Lin, C. L. Li, H. P. Wan,
H. T. Lee, C. F. Liu, Energy Fuels 2011, 25, 890.
[9]
a) J. He, C. Zhao and J. A. Lercher, J. Am. Chem. Soc., 2012, 134,
20768; b) H. H. Fang, J. W. Zheng, X. L. Luo, J. M. Du, A. Roldan, S.
Leoni and Y. Z. Yuan, Appl. Catal., A: Gen. 2017, 529, 20; c) A. R.
Ardiyanti, S. A. Khromova, R. H. Venderbosch, V. A. Yakovlev, H. J.
Heeres, Appl. Catal. B Environ. 2012, 117-118, 105; d) R. N. Olcese, M.
Bettahar, D. Petitjean, B. Malaman, F. Giovanella, A. Dufour, Appl.
Catal.
B Environ. 2012, 115-116, 63; e) P. M. Mortensen, J. D.
Grunwaldt, P. A. Jensen, A. D. Jensen, Catal. Today 2016, 259, 277.
[10] a) W. Schutyser, S. V. d. Bosch, J. Dijkmans, S. Turner, M. Meledina,
G. V. Tendeloo, D. P. Debecker, B. F. Sels, ChemSusChem 2015, 8,
1805; b) N. Yang, C. Zhao, P. J. Dyson, C. Wang, L. T. Liu, Y. Kou,
ChemSusChem 2008, 1, 626.
Experimental Section
Tungsten carbide (WxC@CS) was prepared via careful carburization of
hybrid organic–inorganic precursors in the presence of tungsten. The
Ni/CNT catalysts were synthesized by controlling the heating ramp during
the preparation. The integrated dual catalysts with closed proximity were
prepared by physical grinding for 15 min. Conversions of lignin-derived
oxygenates were performed using a fixed-bed reactor under different
reaction conditions.
[11] a) Y. Yang, A. Gilbert, C. Xu, Appl. Catal. A: Gen. 2009, 360, 242; b) C.
Zhao, Y. Kou, A. A. Lemonidou, X. B. Li, J. A. Lercher, Angew. Chem.
Int. Ed. 2009, 48, 3987; c) K. L. Luska, P. Migowski, S. El Sayed, W.
Leiner, Angew. Chem. Int. Ed. 2015, 54, 15750; d) H. H. Duan, J. C.
Dong, X. R. Gu, Y. K. Peng, W. X. Chen, T. Issariyakul, W. K. Myers, M.
J. Li, N. Yi, A. F. R. Kilpatrick, Y. Wang, X. S. Zheng, S. F. Ji, Q. Wang,
J. T. Feng, D. L. Chen, Y. D. Li, J. C. Buffer, H. C. Liu, S. C. E. Tsang,
D. O’Hare, Nat. Commun. 2017, 8, 591.
[12] a) C. Zhao, J. A. Lercher, Angew. Chem. Int. Ed. 2012, 51, 5935; b) C.
Zhao, J. He, A. A. Lemonidou, X. Li, J. A. Lercher, J. Catal. 2011, 280,
8; c) C. Zhao, J. A. Lercher, ChemCatChem 2012, 4, 64.
Acknowledgements
[13] a) N. B. Van, D. Laurenti, P. Delichere, C. Geantet, Appl. Catal. B:
Environ. 2011, 101, 246; b) X. Zhu, L. L. Lobban, R. G. Mallinson, D. E.
Resasco, J. Catal. 2011, 281, 21; c) D. Y. Hong, S. J. Miller, P. K.
Agrawal, C. W. Jones, Chem. Commun. 2010, 46, 1038; d) Q. N. Xia,
Q. Cuan, X. H. Liu, X. Q. Gong, G. Z. Lu, Y. Q. Wang, Angew. Chem.
Int. Ed. 2014, 53, 9755.
This work was supported by the National Key Research and
Development Program of China (2017YFA0206801), the
National Natural Science Foundation of China (21972113 and
21473145), and the Program for Innovative Research Team in
Chinese Universities (IRT_14R31).
[14] a) G. J. Wu, N. Zhang, W. L. Dai, N. J. Guan, L. D. Li, ChemSusChem
2018, 11, 2179; b) H. L. Wang, H. M. Wang, E. Kuhn, M. P. Tucker, B.
This article is protected by copyright. All rights reserved.

10.1002/cssc.201902029
ChemSusChem
RESEARCH ARTICLE
Yang, ChemSusChem 2018, 11, 285; c) H. L. Wang, H. Ruan, M. Q.
Feng, Y. L. Qin, H. Job, L. L. Luo, C. M. Wang, M. H. Engelhard, E.
Kuhn, X. W. Chen, M. P. Tucker, B. Yang, ChemSusChem 2017, 10,
1846.
[15] a) H. H. Fang, J. M. Du, C. C. Tian, J. W. Zheng, X. P. Duan, L. M. Ye,
Y. Z. Yuan, Chem. Commun. 2017, 53, 10295; b) H. H. Fang, A.
Roldan, C. C. Tian, Y. P. Zheng, X. P. Duan, K. Chen, L. M. Ye, S.
Leoni, Y. Z. Yuan, J. Catal. 2019, 369, 283.
[16] a) M. V. Bykova, D. Y. Ermakov, V. V. Kaichev, O. A. Bulavchenko, A.
A. Saraev, M. Y. Lebedev, V. A. Yakovlev, Appl. Catal. B: Environ.
2012, 113-114, 296; b) M. V. Bykova, D. Y. Ermakov, S. A. Khromova,
A. A. Saraev, M. Y. Lebedev, V. A. Yakovlev, Catal. Today 2014, 220-
222, 21; c) X. H. Zhang, T. J. Wang, L. L. Ma, Q. Zhang, X. M. Huang,
Y. X. Yu, Appl. Energ. 2013, 112, 533; d) X. H. Zhang, T. J. Wang, L. L.
Ma, Q. Zhang, Y. X. Yu, Q. Y. Liu, Catal. Commun. 2013, 33, 15; e) H.
Jahromi, F. A. Agblevor, Appl. Catal., A: Gen. 2018, 558, 109.
[17] a) A. B. Dongil, I. T. Ghampson, R. Garcıa, J. L. G. Fierro and N.
Escalona, RSC Adv. 2016, 6, 2611; b) H. X. Yang, S. Q. Song, R. C.
Rao, X. Z. Wang, Q. Yu, A. M. Zhang, J. Mol. Catal. A Chem. 2010 1–2,
33; c) C. W. Hu, J. Yao, H. Q. Yang, Y. Chen, A. M. Tian, J. Catal. 1997,
166, 1.
[18] D. C. Elliott, T. R. Hart, G. G. Neuenschwander, L. J. Rotness, A. H.
Zacher, Environ. Prog. Sustain. Energy 2009, 28, 441.
[19] K. Routray, K. J. Barnett, G. W. Huber, Energy Technol. 2017, 5, 80.
[20] E. Furimsky, Appl. Catal. A: Gen. 2000, 199, 147.
This article is protected by copyright. All rights reserved.

10.1002/cssc.201902029
ChemSusChem
RESEARCH ARTICLE
Entry for the Table of Contents (Please choose one layout)
Layout 1:
RESEARCH ARTICLE
Hydrodeoxygenation of lignin-derived
oxygenates and the actual bio-oil can
be effectively achieved via a tandem
hydrogenolysis–hydrogenation
Huihuang Fang, Weikun Chen, Shuang
Li, Xuehui Li, Xinping Duan, Linmin Ye,
and Youzhu Yuan*
Page No. – Page No.
strategy, whereas tungsten carbide is
readily for C–O bond hydrogenolysis,
and Ni is mainly responsible for arene
hydrogenation. Product distribution
can be tuned by the flexible use of
integration manners and the active
catalysts. A total mass and carbon
yield to 27.9% and 45.0% is achieved
by conversion of the actual bio-oil.
Tandem hydrogenolysis–
hydrogenation of lignin-derived
oxygenates over integrated dual
catalysts with optimized
interoperations
((Insert TOC Graphic here))
This article is protected by copyright. All rights reserved.