Environmentally-friendly and sustainable synthesis of bimetallic NiCo-based carbon nanosheets for catalytic cleavage of lignin dimers

Article abstract of DOI:10.1016/j.inoche.2021.108816

This paper reports on a study of 2D metal-based (Ni-, NiCo-) carbon nanosheet (CNs) material that were synthesized via a template method and the synthetic materials showed an ultra-thin lamellar structure. The structures were characterized using different analytical methods including XRD, SEM, EDX, TEM, XPS, NH₃-TPD. The synthesized NiCo-based CNs are ultrathin sheet shape with good crystallinity and uniform particle distributions. In the synthetic route of NiCo-based CNs, sodium lignosulfonate was employed as carbon and sulfur source and boric acid was used as 2D template to form a perfect lamellar structure. It manifested an environmentally-friendly and sustainable concept for preparation of the 2D NiCo-CNs. Although simple CNs was a poor catalyst, after Ni and NiCo doping, it became highly active in cleavage of β-O-4 ether bond in lignin through a catalytic transfer hydrogenation process and led to very high product yields.

Full text of DOI:10.1016/j.inoche.2021.108816

Inorganic Chemistry Communications 132 (2021) 108816
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Environmentally-friendly and sustainable synthesis of bimetallic
NiCo-based carbon nanosheets for catalytic cleavage of lignin dimers
,
c
,
,
,c
c
,
,
,
,c
Changzhou Chena 1, Dichao Wua 1, Jurong Rena c, Peng Liua c, Haihong Xiaa
,
Minghao Zhoub *, Jianchun Jianga
,
a Institute of Chemical Industry of Forest Products, Chinese Academy of Forestry Key Lab. of Biomass Energy and Material, Jiangsu Province; National Engineering Lab.
for Biomass Chemical Utilization; Key and Open Lab. on Forest Chemical Engineering, SFA, Nanjing 210042, China
b School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, China
c Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Nanjing Forestry University, Nanjing 210037, China
A R T I C L E I N F O
A B S T R A C T
Keywords:
This paper reports on a study of 2D metal-based (Ni-, NiCo-) carbon nanosheet (CNs) material that were syn-
thesized via a template method and the synthetic materials showed an ultra-thin lamellar structure. The struc-
tures were characterized using different analytical methods including XRD, SEM, EDX, TEM, XPS, NH3-TPD. The
synthesized NiCo-based CNs are ultrathin sheet shape with good crystallinity and uniform particle distributions.
In the synthetic route of NiCo-based CNs, sodium lignosulfonate was employed as carbon and sulfur source and
boric acid was used as 2D template to form a perfect lamellar structure. It manifested an environmentally-
friendly and sustainable concept for preparation of the 2D NiCo-CNs. Although simple CNs was a poor cata-
lyst, after Ni and NiCo doping, it became highly active in cleavage of β-O-4 ether bond in lignin through a
catalytic transfer hydrogenation process and led to very high product yields.
NiCo
CNs
β-O-4
Lignin
Catalytic transfer hydrogenation
1. Introduction
under extra H2 [18]. Although these noble metal-based catalysts wit-
nessed considerable success, it still faced many challenges, such as high
Sustainable utilization of lignin, especially waste sodium lignosul-
fonate from pulp and paper making, has attracted lots of attention [1–5].
While the employment of lignin could not only provide renewable car-
bon resource, but also solve the problem of environmental waste utili-
zation [6–8]. However, due to the three-dimension amorphous polymer
structure of lignin, the degradation of real lignin substantially restricted
[9–10]. In the past few years, tremendous efforts to the depolymeriza-
tion of lignin have been implemented in particularly using lignin β-O-4
model compounds as a research material over heterogeneous catalysts
[11–15]. Generally, lignin β-O-4 ether bond could be cleaved via
hydrogenolysis using high H2 pressure over different noble metal-based
catalysts (e.g., Pt, Ru, Pd) [13–15]. For example, Han et al. found Ru/C
and Ru/hydroxyapatite could efficiently catalyze the cleavage of aro-
matic ether bond in various lignin-derived compounds via catalytic
transfer hydrogenation employing isopropanol as hydrogen source
[16–17]. Wei et al. reported Ru/AC exhibited a high activity for con-
verting lignin model compounds into cyclohexanol and cyclohexane
prices, environmental pollution, employment of extra H2 as hydrogen
source and so on [19]. Therefore, catalytic transfer hydrogenation for
the transformation of lignin model compounds to value-added products
over transition metal-based catalysts is a tendency of lignin conversion
in the future [20].
As well-known, 2D CNs materials were employed in vast fields such
as biotechnology, energy storage and catalytic reactions, and it has the
advantages of both unique electronic properties in confined dimension
of nanophase sp2-hybridized carbon [21] and endowing more active
sites as well as facilitating better contact with the reaction substrates in
catalytic reaction [22]. On the basis of the traditional impregnated
synthesis of NiCo-based heterogeneous catalysts [23], NiCo-loaded
carbon nanosheets with ultrathin layers was synthesized using sodium
lignosulfonate from pulp and paper making as carbon and sulfur source
and boric acid as 2D template in one-step. The obtained 2D materials
were calcined under 700 ◦C for 2 h, which provided a sustainable, green,
energy-saving, and time-saving method. Thus, the synthesized NiCo-
* Corresponding author.
E-mail address: zhouminghao@yzu.edu.cn (M. Zhou).
1
These authors contributed equally: Changzhou Chen and Dichao Wu.
https://doi.org/10.1016/j.inoche.2021.108816
Received 20 May 2021; Received in revised form 22 July 2021; Accepted 23 July 2021
Available online 30 July 2021
1387-7003/© 2021 Elsevier B.V. All rights reserved.

C. Chen et al.
Inorganic Chemistry Communications 132 (2021) 108816
Fig. 1. (a) photograph of as-prepared NiCo-CNs; (b) SEM images of CNs; (c) SEM image of Ni-CNs; (d) SEM image of NiCo-CNs (e) EDX spectrum of NiCo-CNs. (f-j)
element mapping of NiCo-CNs.
based carbon nanosheet was then used in the catalytic cleavage of β-O-4
ether bond through a catalytic transfer hydrogenation process and
achieved a good result, indicating that catalysts with good crystallinity
and uniform particle distributions have good application prospects in
catalytic degradation of lignin model compounds and lignin. According
to this, various advantages of the as-prepared 2D NiCo-CNs could be
found as follows: (1) transition metals nickel and cobalt were cheap and
easy to get, (2) boric acid was used as 2D template, and it could be
recycled for repeated use by evaporative crystallization from the waste
liquid [24], (3) waste reaction product of wood pulp lignosulfonate was
calcined as support was in line with the concept of green chemistry.
Therefore, we wish to report a new alternative method for catalytic
transfer hydrogenation of lignin model compounds to corresponding
aromatics over an environmentally-friendly and sustainable NiCo-CNs
catalyst.
2.2. General procedures for the preparation of CNs and NiCo-CNs
CNs was prepared by an impregnation method using boric acid as
templet. 8 g boric acid was added into water at 80 ◦C, followed by
adding 1 g sodium lignosulfonate under magnetic stirring. The dark
mixture solution was remained at 80 ◦C under stirring until the water
was evaporated. Then, the evaporated solid was then calcined under
700 ◦C for 2 h, obtaining a black powdery product. In the end, the ob-
tained black powdery product was washed with water to wash off boric
acid and dried at 80 ◦C for 12 h to yield desired CNs.
Ni-CNs and NiCo-CNs were prepared in the same method. 8 g boric
acid, 1 g sodium lignosulfonate, 0.4 g nickel nitrate hexahydrate and 0.1
◦
g cobalt nitrate hexahydrate were added in the water at 80 C under
magnetic stirring, followed by evaporation, calcination and washing
with water. In the end, the desired Ni-CNs and NiCo-CNs were obtained.
2. Experimental details
2.3. General procedure for the reactions
2.1. Materials
The reaction was carried in a 25 mL high pressure reactor (Instru-
ment model: YZPR-25) which was purchased from Beijing Yanzheng
Biotechnology Co., Ltd. In a typical run, 100 mg of lignin β-O-4 substrate
(2-phenoxy-1-phenylethan-1-ol was selected as model compounds) and
20 mg of NiCo-CNs catalyst in 10 mL of iPrOH were charged into a 25 mL
stainless Parr autoclave. The reaction was then heated at 240 ◦C for 4 h
with stirring at 800 rpm under 2 MPa N2. When the reaction terminated,
NiCo-CNs could be removed by a centrifugal process and reused in the
next run. The obtained colorless mixture was followed analyzed by GC/
MS using n-dodecane as the internal standard. The reaction conversion
rate and yield of the aromatic monomer were calculated according to the
following Eqs. (1)–(3):
Ni(NO3)2⋅6H2O and Co(NO3)2⋅6H2O were obtained from Aladdin
Industrial Inc. Shanghai, China. Sodium lignosulfonate and boric acid
was provided from Sigma-Aldrich. Phenyl benzyl ether (>99%),
diphenyl ether (>99%), phenethoxybenzene, 2-phenoxy-1-phenyle-
than-1-one, 2-phenoxy-1-phenylethan-1-ol, 2-(2-methoxyphenoxy)-1-
phenylethan-1-ol and 2-(2-methoxyphenoxy)-1-(4-methoxyphenyl)pro-
pane-1,3-diol was provided from Leyan.com. N2 was supplied by local
gas factory. Deionized water and isopropanol were employed for all
experiments.
mole of reacted substrate
total mole of substrate feed
Conversion =
*100%
(1)
2

C. Chen et al.
Inorganic Chemistry Communications 132 (2021) 108816
Fig. 2. XPS spectra of as-prepared NiCo-CNs: (a) survey; (b) C 1s; (c) S 2p; (d) Ni 2p; (e) Co 2p; (f) TEM image of NiCo-CNs.
mole of ethylbenzene
total mole of substrate feed
Yield of ethylbenzene =
Yield of phenol =
*100%
(2)
(3)
mole of phenol
total mole of substrate feed
*100%
After the reaction, the used catalyst after each run was washed with
iPrOH for three times and dried overnight in the oven at 90 ◦C. Repeated
experiment was carried out under the optimal reaction condition.
2.4. Characterization
Powder X-ray diffraction (XRD) patterns of the catalysts were per-
formed on a Bruker D8 Advance X-ray powder diffractometer using Ni
filtered Cu K
α
radiation (λ = 1.5406 Å) with a scan speed of 2◦ minꢀ 1
and a scan range of 10–80◦ at 30 kV and 15 mA. Scanning electron
microscopy (SEM) was studied by using a TESCAN-VEGA3 instrument.
Transmission electron microscopy (TEM) images were collected using a
TEM Tecnai G2 20. The acidity of catalysts was detected by NH3-TPD on
a Micromeritics AutoChem 2920 instrument. The X-Ray photoelectron
spectroscopy (XPS) was examined on an ESCALAB-250 (Thermo-VG
Fig. 3. NH3-TPD of the Ni-CNs and NiCo-CNs samples.
Scientific, USA) spectrometer with Al Kα (1486.6 eV) irradiation source.
planes of Ni3S2 [25]. No diffraction peaks of Co and/or CoS was
observed. It was probably owing to good crystallinity or low content of
Co introduced in NiCo-CNs (Fig. S1).
3. Results and discussion
XPS survey spectra in Fig. 2a proved the presence of C, O, S, Ni and
Co in NiCo-CNs material. In C 1s spectra (Fig. 2b), three distinct peaks at
The 2D lamellar NiCo-CNs was synthesized by an impregnation
method using sodium lignosulfonate as carbon and sulfur source, boric
acid as templet. The samples were then calcined and dried. The photo-
graph of the as-prepared NiCo-CNs was recorded, and the uniform black
powder could be clearly seen in Fig. 1a. SEM images in Fig. 1b-d indi-
cated a perfect ultra-thin lamellar structure of CNs, Ni-CNs and NiCo-
CNs. It also revealed that the introduction of different metals would
not destroy the excellent lamellar structure. As shown in the insert di-
agram of Fig. 1e, the Ni:Co weight ratio was around 4:1, which was close
to the theoretical calculation in the preparation of NiCo-CNs. Addi-
tionally, the element mapping result in Fig. 1f-j suggested that Ni, Co, S
were all presented in the surface of CNs with distinct morphology of
nanoparticles. The XRD patterns of Ni-CNs showed diffraction peaks
with 2θ values of 31.104◦, 38.271◦, 44.330◦, 49.733◦and 55.161◦,
which were indexed to the (110), (021), (202), (113) and (122)
– –
284.20 eV, 285.50 eV and 287.20 eV were corresponding to C C, C S,
–
and C O [26]. For S2p spectra (Fig. 2c), the peak at 162.20 eV and
–
164.25 eV were corresponded to Ni-S in NiCo-CNs [12]. The main peaks
of the XPS spectrum of Ni2p (Fig. 2d) around 855.05 eV and 857.40 eV
were indexed to Ni2p3/2, whereas the peaks at 873.50 eV and 874.90 eV
were indexed to Ni2p1/2, which all corresponded to Ni3S2 [27]. In Co2p
spectra (Fig. 2e). The content of the Co 2p spectrum was complicated
due to the presence of various species at surface level. The Co 2p2/3
spectrum has binding energies at 780.10 and 784.50 eV that could be
attributed to CoS. The peaks between 797.20 and 803.05 eV belonged to
Co 2p1/2 signals of their Co 2p3/2 counterparts and the satellite signal
[28]. It was consistent with the results in XRD patterns (Fig. S1). TEM
image in Fig. 2f could clearly discover the presence of nano Ni3S2 and
3

C. Chen et al.
Inorganic Chemistry Communications 132 (2021) 108816
Table 1
Evaluation of the NiCo-CNs in cleavage of phenoxy-1-phenylethan-1-ol over different catalysts.a
OH
O
O
OH
Catalyst
iPrOH, 2 MPa N2
1
2
3
4
Entry
Cat.
Conv. (%)b
Yield(%)b
2
3
4
1
2
3
4
5
6
–
0
0
0
0
CNs
0
0
0
0
Ni powder
5
3
2
2
Ni powder and CNs
Ni-CNs
6
3
2
3
70
99
16
5
44
90
42
89
NiCo-CNs
a
Reaction conditions: substrate (100 mg), Cat. (20 mg), iPrOH (10 mL), 2.0 MPa N2, 240 ◦C, 4 h;
b
Conversion and yields were determined by GC/MS with n-dodecane as the internal standard.
CoS metal particles over the lamellar nanosheets, suggesting a uniform
acid distributions in Ni-CNs and bimetallic NiCo-CNs catalysts. Inter-
estingly, the improvement in both total acidity and Bronsted acid site in
NiCo-CNs was observed during the pyridine-IR analysis, which was in
accordance with the NH3-TPD analysis results.
particle distribution.
In addition, the acidity of Ni-CNs and NiCo-CNs was investigated
using NH3-TPD, as shown in Fig. 3. It was found that Ni-CNs showed a
broad NH3 desorption peak at 300–400 ◦C and NiCo-CNs showed a
broad NH3 desorption peak at 350–450 ◦C. It indicated the presence of
medium strong acid site in Ni-CNs and NiCo-CNs catalysts. It could also
be found that NH3 desorption peak in NiCo-CNs shifted to high tem-
perature compared with Ni-CNs. This phenomenon indicated an acidity
enhancement after the introduction of element Co in Ni-CNs catalyst.
Thus, it resulted in a better catalytic activity in the cleavage of lignin
β-O-4 ether bond over NiCo-CNs.
4. Catalytic cleavage of lignin β-O-4 ether bond
Blank experiment with no catalyst or CNs as catalyst failed to
transformed 2-phenoxy-1-phenylethan-1-ol to ethylbenzene and phenol
(Table 1 entries 1–2). When Ni powder was employed in the reaction,
nearly 95% substrate was recovered in the catalytic system (Table 1
entry 3). Mechanical mixture of nickel powder and CNs also could not be
converted 2-phenoxy-1-phenylethan-1-ol into ethylbenzene and phenol
(Table 1 entry 4). Ni-CNs showed better catalytic performances in the
cleavage β-O-4 ether bond (Table 1 entries 5), producing 3 and 4 in
moderate yield (44% and 42% yield of ethylbenzene and phenol,
respectively). It could come to a conclusion that Ni3S2 on the surface of
CNs played a catalytic role in the cleavage of β-O-4 ether bond compared
The acidity information in Table S3 confirmed the synergy between
Ni and Co. The total acidity for Ni-CNs increased gradually with the
addition of Co in catalysts, while the acidity for NiCo-CNs improved to
3.6221 mmol/g NH3, in comparison with Ni-CNs catalyst (0.4604
mmol/g NH3). Apart from the improvement in total acidity, pyridine-IR
analysis was also conducted to understand the Bronsted acid and Lewis
Fig. 4. Cleavage of 2-phenoxy-1-phenylethan-1-ol over NiCo-CNs (a) effect of reaction time, (b) effect of reaction temperature, (c) effect of N2 pressure, (d) and effect
of solvents.
4

C. Chen et al.
Inorganic Chemistry Communications 132 (2021) 108816
OH
O
HO
Optimal Condition
Ar
Ar
Ar'
Ar'
1a
1a
1b
1c
1d
OH
O
OH
OMe
OMe
O
O
O
O
1b
1c
1d
HO
HO
HO
HO
90%
1e
89%
85%
83%
92%
91%
72%
69%
1g
1f
1f
OH
OMe
O
O
O
MeO
1e
HO
1g
OMe
HO
HO
HO
MeO
32%
88%
trace
85%
52%
55%
Fig. 5. Cleavage of various lignin derived dimers over optimal NiCo-CNs catalyst.
with the results in entry 4. Interestingly, introducing Co into Ni-CNs
dramatically improved the catalyst activity and the NiCo-CNs-
catalyzed reaction of 1 led to 3 and 4 in almost quantitative yield
(Table 1 entry 6). It was probably owing to more active sites in lamellar
structure facilitated better contact with the reaction substrates and the
enhancement acidity of NiCo-CNs after the introduction of Co. The result
in Table 2 entry 6 could be repeated three times and it could be seen in
Table S2. The cleavage of β-O-4 ether bond was a catalytic transfer
hydrogenation process, in which isopropanol served as a good H-donner
and provided a large amount of active hydrogen to promote the cleavage
N2 pressure reach 4 h, 240 ◦C and 2 MPa, the conversion and yield
reached the highest value (99% conversion of 2-phenoxy-1-phenyle-
than-1-ol, 90% and 89% yield of ethylbenzene and phenol respec-
tively). It was interesting to find that the yield of phenethoxybenzene
decreased with the increase of the reaction time, reaction temperature
and N2 pressure. It indicated that phenethoxybenzene was a key inter-
mediate state in the transformation of 2-phenoxy-1-phenylethan-1-ol.
From the result detected in the GC/MS, we could also find the exis-
tence of phenethoxybenzene (Fig S3). When three types of hydrogen
donor solvent were employed as solvent in the catalytic process, mod-
erate to high yield of ethylbenzene and phenol was obtained in Fig. 4c.
Cyclohexane, compared with methanol, ethanol and isopropanol, was
carried out as solvent in the cleavage of 2-phenoxy-1-phenylethan-1-ol.
It failed to convert 2-phenoxy-1-phenylethan-1-ol to aromatic mono-
mers, which confirmed that methanol, ethanol and isopropanol served
as hydrogen donor solvent in the catalytic reaction. This is consistent
with our previous research [30].
–
of C O bond [29]. Of note is the mass balance of these reactions. The
hydrogenolysis product was obtained as phenethoxybenzene, ethyl-
benzene and phenol. And nearly no starting materials could be recov-
ered by GC/MS when the product yield is very high in Fig. S5. The
representative chromatogram could be seen in Fig. S3.
In order to determine the optimized reaction condition for the
cleavage of β-O-4 ether bond, the effect of reaction condition such as
reaction time, reaction temperature, N2 pressure, solvent on the cata-
lytic cleavage of 2-phenoxy-1-phenylethan-1-ol were studied. As shown
in Fig. 4a-4c, as the reaction time, reaction temperature and N2 pressure
increased, the conversion of 2-phenoxy-1-phenylethan-1-ol and the
yield of aromatic monomers continue to increase. Although isopropanol
could replace extra hydrogen source to provide hydrogen, it could only
provide a small amount of hydrogen compared with extra H2. So, we
added 2 MPa N2 in the catalytic system for total conversion of 2-phe-
noxy-1-phenylethan-1-ol. It was probably owing to that the existence
of high N2 pressure could lower too high catalyst surface coverage of H2
or ease the dispersion of the gas phase in the liquid, which resulted in a
good conversion and yields of target products. Similar reaction condi-
tion (reaction condition: NiCu/C, 270 ◦C, 4 h, 1 MPa N2 pressure) was
reported by Cheng et al [30]. When the reaction time, temperature and
Inspired by the excellent performance of NiCo-CNs catalyst for the
–
efficient cleavage of the β-O-4 bond. Then the cleavage of C O bond
was further studied in more detail by varying substituent groups on the
benzene ring in Fig. 5. Generally, it could be verified that the NiCo-CNs
catalyst was highly efficient for the transfer hydrogenolytic cleavage of
ether bond in a variety of lignin derived model compounds. Substrate
with no substituent group on α-C could be cracked to obtain 85% and
83% yield of ethylbenzene and phenol in Entry 1b, respectively. When
α
-C was substituted with carbonyl, better yield of ethylbenzene and
phenol was achieved in Entry 1c. It was probably owing to lower bond
dissociation energy of β-O-4 ketone (227.8 kJ/mol) than β-O-4 alcohol
–
(274.0 kJ/mol), which led to C O bond in β-O-4 ketone is easier to
break [31]. Thus, substitutions at the
α-C atom have a great effect on
bond dissociation energy of Cβ-OPh bond and the activation of the β-O-4
5

C. Chen et al.
Inorganic Chemistry Communications 132 (2021) 108816
Fig. 6. Possible pathway for the conversion of 2-phenoxy-1-phenylethan-1-ol over NiCo-CNs.
lignin linkage. In addition, methoxy substituted β-O-4 dimer model
compounds was carried out in the catalytic process and moderate con-
version and yield of corresponding aromatic monomers were obtained.
For example, 2-(2-methoxyphenoxy)-1-phenylethan-1-ol could generate
72% yield of ethylbenzene and 69% guaiacol (Entry 1d). it was not easy
to find that substituent groups on benzene ring led to a negative effect on
the cleavage of lignin derived β-O-4 dimer model compounds. It was
consistent with our previous research. We all know that β-O-4 dimer
model compounds with γ-OH lignin typical realistic segment [32].
Therefore, 2-(2-methoxyphenoxy)-1-(4-methoxyphenyl)propane-1,3-
diol was charged in the optimal catalytic system. However, it failed to
obtain 1-ethyl-4-methoxybenzene (Entry 1d). Additionally, two kinds of
1-ol over NiCo-CNs catalyst.
The detailed pathway was discussed, and it could be seen in Fig. S4.
The isopropanol was adsorbed and dissociated on NiCo sites to form H+.
firstly, the metal NiCo and the formed H+ enhanced the hydro-
deoxygenation of C
α
-OH to produce phenethoxybenzene. The H+ sub-
sequently reacted with oxygen atom in phenethoxybenzene to produce
+
–
phenol via the cleavage of C O ether bond. Finally, C6H5-CH2-CH2
abstracted Hꢀ from the C
α
-Hꢀ of isopropanol to produce ethylbenzene.
The GC–MS results in Fig S3 also confirmed the pathway in Fig S4.
5. Conclusion
–
C
O bond dimers of lignin (4-O-5 and α-O-4) were investigated in the
In conclusion, we discovered that the CNs exhibited excellent cata-
lytic activities in cleavage of lignin β-O-4 ether bond after NiCo doping,
because of the ultrathin lamellar structure that led to endowing more
active sites to facilitate better contact with the reaction substrates. The
catalyst could also be easily removed and recycled in the next run with
only slight decrease. In comparison with the previously reported NiCo-
based catalyst, the lamellar NiCo-CNs was fabricated from cheap and
abundant waste residue of pulp sodium lignosulfonate in one step
through very simple immersing processes. It provided an
environmentally-friendly method for lignin dimers hydrotreatment and
further hydrotreatment of realistic lignin would be carried out in our
next work.
optimal reaction condition. Moderate yield of benzene and phenol was
achieved in Entry 1f compared with relative high yield of toluene and
phenol in Entry 1 g. This is mainly due to high bond dissociation energy
of 4-O-5 ether bond (314.0 kJ/mol) than α-O-4 (245.0 kJ/mol) [33–34].
Generally. all these examples above demonstrated that NiCo-CNs cata-
lyst showed good to excellent catalytic cleavage of different substrates
containing lignin ether bonds to generate corresponding aromatic
monomers, which could provide a novel route for the generation of ar-
omatic hydrocarbons and aromatic alcohols by catalytic hydrotreatment
of lignin dimeric model compounds. Finally, the recycled sustainable
NiCo-CNs catalysts could also be carried out in the next five runs with
only slight decrease in the conversion (Fig. S2). It was probably owing to
the metal leaching from the surface of the catalyst (Table S1).
CRediT authorship contribution statement
Three different types of intermediate state were proposed, including
2-phenoxy-1-phenylethan-1-one, phenethoxybenzene and (2-phenox-
Changzhou Chen: Conceptualization, Writing – original draft.
Dichao Wu: Methodology. Jurong Ren: Software. Peng Liu: Valida-
tion, Formal analysis, Investigation. Haihong Xia: Resources, Data
curation. Minghao Zhou: Visualization, Supervision, Project adminis-
tration. Jianchun Jiang: Funding acquisition.
–
yvinyl)benzene. It could be clearly seen in Fig. 6 that the order of C
O
bond dissociated energy is as follows: (2-phenoxyvinyl)benzene >
phenethoxybenzene > 2-phenoxy-1-phenylethan-1-one, which indi-
cated that 2-phenoxy-1-phenylethan-1-ol need to overcome the energy
of 62.3 kJ/mol to convert into (2-phenoxyvinyl)benzene [31]. It was
quite difficult to achieve this goal in our catalytic system. So, (2-phe-
noxyvinyl)benzene was not a key intermediate and no (2-phenoxyvinyl)
benzene was detected in time conversion curve. It was surprising to find
Declaration of Competing Interest
–
that the C O bond dissociated energy of 2-phenoxy-1-phenylethan-1-
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
one was lower than 2-phenoxy-1-phenylethan-1-ol. However, no
oxidant was added in the reaction and we did not observe 2-phenoxy-1-
phenylethan-1-one in the GC/MS. So, route 1 is not a possible reaction
pathway for the conversion of 2-phenoxy-1-phenylethan-1-ol. From the
GC/MS result in the Fig. S3 the possible intermediate was phenethox-
ybenzene, and ethylbenzene and phenol were generated after the
Acknowledgements
This work was supported by the Research Funds of Jiangsu Key
Laboratory for Biomass Energy and Material (Grant. No. JSBEM-S-
201803), the National Natural Science Foundation of China (Grant.
No. 32071718)
–
cleavage of C O bond over NiCo-CNs. In addition, the reaction
circumstance is not for the dehydrogen or oxygenation. In general, route
2 was the main pathway in the conversion of 2-phenoxy-1-phenylethan-
6

C. Chen et al.
Inorganic Chemistry Communications 132 (2021) 108816
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