Selective Hydrodeoxygenation of Lignin-Derived Phenols to Cyclohexanols or Cyclohexanes over Magnetic CoNx@NC Catalysts under Mild Conditions

Article abstract of DOI:10.1021/acscatal.6b01785

The hydrodeoxygenation (HDO) of lignin-derived phenols is important to produce the renewable biofuels. Herein, we reported a simple method to prepare magnetic nitrogen-doped carbon supported cobalt nitride catalysts (CoNx@NC) by copyrolysis of cellulose and cobalt nitrate under ammonia atmosphere. The catalysts were prepared at different temperatures and characterized by elemental analysis, atomic absorption spectroscopy (AAS), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and temperature-programmed reduction (TPR). The CoNx@NC-650 (pyrolyzed at 650°C) exhibited the best HDO activity for eugenol conversion among a series of Co-based catalysts. The yield of propylcyclohexanol from eugenol was >99.9% under 2 MPa H₂ at 200°C for 2 h. Moreover, a high yield of propylcyclohexane (99.1%) could be achieved when the solid acid HZSM-5 was added to the reaction system. Other lignin-derived phenolic compounds were also investigated and the yield of alkanes was >90%. Based on the mechanism investigation, the catalyst demonstrated a high selectivity to cleave the C_aryl-OR bond under mild conditions. (Chemical Equation Presented).

Full text of DOI:10.1021/acscatal.6b01785

Subscriber access provided by Northern Illinois University
Article
Selective hydrodeoxygenation of lignin-derived phenols to cyclohexanols
or cyclohexanes over magnetic CoNx@NC catalysts under mild conditions
Xiaohao Liu, Lujiang Xu, Guangyue Xu, Wenda Jia, Yanfu Ma, and Ying Zhang
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.6b01785 • Publication Date (Web): 03 Oct 2016
Downloaded from http://pubs.acs.org on October 6, 2016
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
ACS Catalysis is published by the American Chemical Society. 1155 Sixteenth Street
N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 34
ACS Catalysis
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Selective hydrodeoxygenation of lignin-derived
phenols to cyclohexanols or cyclohexanes over
magnetic CoNx@NC catalysts under mild
conditions
Xiaohao Liu1, Lujiang Xu1, Guangyue Xu, Wenda Jia, Yanfu Ma, Ying Zhang*
iChEM, CAS Key Laboratory of Urban Pollutant Conversion, Anhui Province Key
Laboratory for Biomass Clean Energy and Department of Chemistry, University of Science
and Technology of China, Hefei 230026, P. R. China.
* Eꢀmail: zhzhying@ustc.edu.cn
Phone number: 0086ꢀ551ꢀ63603463
1 These authors equally contributed to the work.
ABSTRACT: The hydrodeoxygenation (HDO) of ligninꢀderived phenols is important to
produce the renewable biofuels. Herein, we reported a simple method to prepare magnetic
nitrogenꢀdoped carbon supported cobalt nitrides catalysts (CoNx@NC) by coꢀpyrolysis of
cellulose and cobalt nitrate under ammonia atmosphere. The catalysts were prepared at
different temperatures and characterized by elemental analysis, AAS, BET, XRD, XPS, TEM
ACS Paragon Plus Environment

ACS Catalysis
Page 2 of 34
1
2
3
4
5
6
7
8
9
and TPR. The CoNx@NCꢀ650 (pyrolyzed at 650 °C) exhibited the best HDO activity for
eugenol conversion among a series of Coꢀbased catalysts. The yield of propylcyclohexanol
from eugenol was greater than 99.9% under 2 MPa H2, 200 °C for 2 h. Moreover, high yield
of propylcyclohexane (99.1%) could be achieved when the solid acid HZSMꢀ5 was added to
the reaction system. Other ligninꢀderived phenolic compounds were also investigated and the
yield of alkanes was greater than 90%. Based on the mechanism investigation, the catalyst
demonstrated a high selectivity to cleave Caryl–OR bond under mild conditions.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
KEYWORDS: Cobalt nitrides; nitrogenꢀdoped carbon; biomass; hydrodeoxygenation;
phenols conversion;
INTRODUCTION
Biofuels derived from lignocelluloses as substitutes for the traditional fossil fuels have
aroused wide attention around the world.1,2,3,4 Lignin as an important part of lignocelluloses
with 40% of biomass energy has a great potential for producing fuels and bulk chemicals.5,6
However, due to the high oxygen content, lignin depolymerized components (mainly
phenolic mixtures) are difficult to use directly. 7 , 8 , 9 In order to address this issue,
hydrodeoxygenation (HDO) has been proposed to transform these compounds to chemicals
and liquid fuels10. Previous research found that the catalysts used for hydrodesulfurization in
petroleum refinery industry such as sulfide NiMo and CoMo also showed good activities for
phenolic HDO.11,12,13,14 However, these catalysts are deactivated easily and may cause the
sulfur pollution of the products.15,16,17
ACS Paragon Plus Environment

Page 3 of 34
ACS Catalysis
1
2
3
4
5
6
7
8
9
In recent years, nonꢀsulfurized catalysts have been studied for phenolic HDO reaction.
These catalysts are mainly focused on the noble metals like Pd,18,19,20,21,22 Pt23,24 and
Ru,25,26,27,28,29,30 etc.. For examples, Pd/CꢀH3PO4/H2O system was first employed by Zhao et
al. to catalyze phenolic bioꢀoil to cycloalkanes under 5 MPa H2, 250 °C.19 Later Ohta et al.
using Pt/AC to catalyze phenols to cyclohexanes under 4 MPa H2, 280 °C, and found that Pt
could catalyze not only hydrogenation of phenols, but also hydrogenolysis of
cyclohexanols.23 They further developed the Pt/HZSMꢀ5 catalyst which could catalyze
various phenols to cyclohexanes even at 110 °C under ambient H2 pressure,24 which is the
mildest condition having been reported. Because Ru has high hydrogenation and hydrolysis
activity, it has also been employed for phenols HDO. Nakagawa et al. using Ru/C and bases
(MgO, NaOH) as catalysts, and found that the presence of base is advantageous to the
cleavage of Caryl–OCH3 bond.27 Recently, Ishikawa et al used Ru–MnOx/C to catalyze HDO
of guaiacol and found that the addition of MnOx slowed down the reaction rate of full
saturation of aromatic ring. Increasing the relative rate of the cleavage of methoxy group to
full saturation of aromatic ring can make HDO fulfilled under milder conditions.30
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Considering the cost of the noble metal catalysts, nonꢀnoble metal catalysts were also
31,32,33,34
applied to catalyze this type of reaction.
RANEY Ni –Nafion/SiO2 system was used
by Zhao et al. to catalyze phenols to cycloalkane with 95% conversion of dihydroeugenol and
75.7% total yields of cycloalkanes at 300 °C, 4 MPa H2.31 Ni/HZSMꢀ5 was also used by the
same research group to catalyze phenols to cycloalkanes at 250 °C and 5 MPa H2.32 Although
these nonꢀnoble catalysts have shown high hydrogenation activity, the reaction condition is
ACS Paragon Plus Environment

ACS Catalysis
Page 4 of 34
1
2
3
4
5
6
still harsh. Therefore, the development of new type of nonꢀnoble catalyst is still necessary to
convert ligninꢀderived phenols under mild condition.
7
8
9
Transition metal nitrides and carbides have been proposed for hydrogenation process35.
Especially molybdenum nitride and carbide can absorb and activate hydrogen and then
transfer it to the reactant molecules.36,37 For cobalt nitride, Milad et al. reported that Co4N
had higher pyridine hydrodenitrogenation (HDN) activity than other bulk metal nitride
catalysts (group IV–VIII, Co4N > Fe3N > Mo2N > W2N > VN ≈ NbN ≈ CrN > TiN).38 In the
meantime, carbon materials, especially for nitrogenꢀdoped carbons (NC) have received
increasing attention in recent years.39, 40 , 41 ,42 The doping of nitrogen into the carbon
architecture can significantly change the physical and chemical properties of the carbon
materials like basicity43 and catalytic activity,44,45 which makes NC have good performance
in various applications, such as supercapacitors,46 oxygen reduction catalyst47 and catalyst
supports,48,49 etc. More recently, metal particles surrounded by NC as redox reaction catalysts
showed good activities. Xu et al. used 3ꢀmethylꢀ1ꢀbutylpyridine dicyanamide (ionic liquid) as
precursor, nanoꢀSiO2 as hard template agent to prepare high nitrogenꢀcontent (12 wt%) NC
material. This material showed excellent property in stabilizing Pd nanoparticles and the
prepared Pd@NC catalyst was highly efficient in HDO of vanillin.50 In addition, some
researchers prepared such kind of catalysts by oneꢀstep pyrolysis at high temperatures under
inert gas atmospheres.51,52,53,54 Jagadeesh et al. prepared Fe2O3/NGr@C catalyst by pyrolysis
of Fe(OAc)2ꢀphenanthroline complex on carbon supports at 800 °C under argon atmosphere.
The catalysts could convert various nitroarenes to anilines with high selectivity.55 Bai et al.
used cobaltꢀcontaining MOFs as precursors to prepare Co/NꢀC catalysts by pyrolysis method
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment

Page 5 of 34
ACS Catalysis
1
2
3
4
5
6
7
8
9
for selective oxidation of alcohols.56 Although these materials showed good performance in
catalysis, the precursors acting as nitrogen and/or carbon sources were expensive. Moreover,
the preparation processes of the precursors were complicated.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
To solve the aforementioned challenges, we developed a simple method to prepare
magnetic CoNx@NC catalyst by coꢀpyrolysis of wideꢀavailable cellulose and Co(NO3)2
under ammonia atmosphere. In this study, the catalysts with different preparation
temperatures were characterized and tested by the HDO of eugenol. Different acids, reaction
temperature and H2 pressure were employed to explore the influence of various parameters
and the optimal reaction conditions. The possible reaction pathway was proposed based on a
kinetic study. Besides eugenol, the HDO of other phenolic compounds were studied. The
stability of the catalyst was also investigated.
EXPERIMENTAL SECTION
Reagents
αꢀCellulose (particle size: 50 ꢁm), eugenol, phenol, guaiacol, 3ꢀmethoxy phenol,
2,6ꢀdimethoxy phenol, catechol, 4ꢀisopropylphenol, diphenyl ether, 4,4'ꢀDihydroxydiphenyl
ether, 4ꢀpropyl phenol, 4ꢀpropylcyclohexanol and 5% Pd/C were purchased from Aladdin
Chemistry Co. Ltd. 3ꢀisopropylphenol was purchased from TCI; Co(NO3)2·6H2O, acetone
and ethyl acetate were purchased from Sinopharm Chemical Reagent Co. Ltd.
Dihydroeugenol was prepared according to
a
previous reported method.7
2ꢀmethoxyꢀ4ꢀpropylcyclohexanol was synthesized as follows: eugenol (1g), Pd/C (100 mg)
and H2O (15 ml) were added to the Parr reactor and reacted at 200 °C, 5 MPa H2 for 30 h
ACS Paragon Plus Environment

ACS Catalysis
Page 6 of 34
1
2
3
4
5
6
with magnetic stirring. After reaction, the water was removed and the target product was
separated by a silica gel column chromatography.
7
8
9
Catalysts Preparation
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
All of the CoNx@NC catalysts were prepared by the in situ coꢀpyrolysis methods. The
catalysts were labeled as CoNx@NCꢀT (T is the pyrolysis temperature, 500 °C, 600 °C,
650 °C, 700 °C or 800 °C, respectively). The preparing procedure of CoNx@NCꢀ650, for
example, is described as follows: 10 g of αꢀcellulose was added into 300 g of acetone in a
roundꢀbottom flask and stirred at 45 °C. 1 g of Co(NO3)2·6H2O was dissolved in acetone (15
g) and then added to the above αꢀCellulose/acetone suspension. The mixture was stirred at
45 °C for 24 h. The solvent was then removed using rotary evaporation and dried at 105 °C
for 10 h. After drying, the powder was added into a feed pipe and purged with NH3 for 1 h.
Then the powder was added into a quartz tube heated by a furnace slowly at 300 °C in the
NH3 flow. After feeding, the temperature was held at 300 °C for 30 min and then raised to a
certain pyrolysis temperature (e.g. 650 °C) with a heating rate of 1°C/min. The temperature
was then kept at 650 °C for 2 h before cooling to room temperature in NH3 flow. The
material was then purged with N2 for 2 h.
The procedure for preparing NCꢀ650 was same as that of CoNx@NCꢀ650, but no
Co(NO3)2·6H2O was impregnated in the cellulose. The procedure for preparation of
Co@Cꢀ650 was also same as that of CoNx@NCꢀ650, but NH3 was substituted by N2.
The procedure for preparation of Co/NC is described as follows: 0.7 g of NCꢀ650 was
added into a 250 ml roundꢀbottom flask with 100 g of acetone and stirred at 45 °C. 127 mg of
Co(NO3)2·6H2O was dissolved in acetone (15 g) and then added to the above suspension. The
ACS Paragon Plus Environment

Page 7 of 34
ACS Catalysis
1
2
3
4
5
6
7
8
9
mixture was stirring at 45 °C for 24 h. The solvent was then removed using rotary
evaporation and dried at 105 °C for 10 h. After drying, the powder was reduced by H2 in a
quartz tube furnace at 650 °C for 2 h with a heating rate of 1 °C/min. After cooling to the
room temperature, the catalyst was purged with N2 for 2 h.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
All of the catalysts were stored in a glove box before used for reaction.
Catalyst Characterization
The nitrogen adsorption/desorption isotherms were measured by Micromeritics TriStar II
(TriStar II 3020 V1.03). The surface area was determined through the Barrett–Emmet–Taller
(BET) method. The average pore volume and pore size were measured by
Barret–Joyner–Halenda method.
Xꢀray power diffraction (XRD) patterns were conducted on an X’pert (PANalytical)
diffractometer, using CuKα radiation at 40 kV and 40 mA, 2θ ranges were 20°ꢀ80°. The
crystal size was calculated by Scherrer equation through the Co(111) diffraction peak:
K
λ
, where K is a constant and equal to 0.89, λ is the Xꢀray wavelength and equal to
< L >
=
β
cosθ
0.154056 nm, β is the full width at half maximum (rad) and θ is the diffraction angle (rad).
The transmission electron microscopy (TEM) images were taken by a JEOL JEMꢀ2010
LaB6 transmission electron microscope. The Xꢀray photoelectron spectroscopy (XPS) spectra
were taken by an Xꢀray photoelectron spectrometer (ESCALAB250). The elemental analysis
was measured by an Elementar vario EL cube. The combustion tube temperature was
950 °C and the reducing tube temperature was 550 °C. The atomic absorption spectroscopy
(AAS) was performed on a PerkinꢀElmer Corporation Analyst 800 instrument. The sample
handling process is as follows: 10 mg of catalyst was added into a 10 ml roundꢀbottom flask
ACS Paragon Plus Environment

ACS Catalysis
Page 8 of 34
1
2
3
4
5
6
with 4 ml of aqua regia and stirred at 80 °C for 24 h. After that, the mixture was diluted to 25
ml in a volumetric flask.
7
8
9
The temperatureꢀprogrammed reduction (TPR) was carried out in a homeꢀbuilt reactor
system coupled to a gas chromatograph. Before TPR tests, the samples were pretreated in Ar
flow at 500 °C for 1 h. The TPR was carried out in a 5% H2/Ar mixture gas flow from 40 °C
with a heating rate of 10 °C/min. The liquid nitrogen/ethanol cooling bath was used to
remove the moisture from the effluent stream before the stream entered a thermal
conductivity detector (TCD).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
The reaction rate computation formula is as follows:
mole of propylcyclohexane
Reaction rate =
mole of Co metal∗t h
( )
Catalyst Test
All of the phenolic HDO reactions were performed in a 25 ml Parr reactor. In a typical
experiment, 164 mg of eugenol, certain amount of catalyst and solvent (10 ml of nꢀdodecane)
were added into the reactor. After purging with hydrogen for 5 times, the reactor was
pressured with 2 MPa H2 at ambient temperature. The reactions were conducted at certain
temperature for certain time with magnetic stirring. After the reaction, the products were
separated from the catalyst by an external magnet (shown in Figure S7), and then diluted with
ethyl acetate and identified by a gas chromatograph–mass spectrometer combination (GCꢀMS,
Agilent 5975C) and quantified by a gas chromatograph (Kexiao 1690) with HPꢀINNOWAX
capillary column (30 m×0.250 mm×0.25 ꢁm). The GC detecting conditions were as follows:
ACS Paragon Plus Environment

Page 9 of 34
ACS Catalysis
1
2
3
4
5
6
7
8
9
nitrogen as carrier gas; injection port temperature: 280 °C; detector (FID) temperature:
280 °C; column temperature: 40 °C, heating up to 250 °C with a heating rate of 10 °C/min.
Bicyclohexane was used as internal standard to quantify the products.
Catalyst Recycle
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
After reaction, the catalyst was separated from solution with an external magnet and
washed three times with dodecane. After that, the catalyst was used for the next run directly.
RESULTS AND DISCUSSION
Characterization of the Catalysts
In order to explore the characteristics of the catalysts, a series of tests were carried out. As
shown in Table 1, the surface area of the catalyst was increased with the pyrolysis
temperature except at 700 °C. The reason for the decrease of the surface area of
CoNx@NCꢀ700 might be due to the morphology transformation of the carbon support from
600 °C to 800°C, which could be observed by TEM and XRD results. The N contents
decreased from 14.89% to 6.12% when the temperature increased from 500 °C to 800°C. The
Co contents of the catalysts were about 5ꢀ10 wt%. Compare with NCꢀ650, the
CoNx@NCꢀ650 had higher surface area, pore volume and size, indicating that the presence
of cobalt could promote the carbon material to form pores and significantly change the
carbon structure.
ACS Paragon Plus Environment

ACS Catalysis
Page 10 of 34
1
2
3
4
5
6
7
Table 1. Characteristics of CoNx@NCx Catalysts
8
9
Particle
Crystal
size(nm)c
Content (wt%)
size(nm)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Pore
size
(nm）
22.8
6.1
SBET
Pore
Sample
Ca
Na
Ha
O
Cob
TEM
XRD
(m2/g) volume(cm3/g)
CoNx@NCꢀ500
CoNx@NCꢀ600
CoNx@NCꢀ650
CoNx@NCꢀ700
CoNx@NCꢀ800
NCꢀ650
74
0.05
0.04
0.12
0.18
0.18
0.02
63.21
64.26
67.29
65.36
70.81
75.11
14.89 3.06 12.47 6.37
11.94 2.81 15.62 5.37
6.4
11.3
13.1
14.1
46.4
--
ꢀꢀ
5.4
6.9
10.1
9.4
--
272
417
290
425
301
8.5
11.32
9.22
6.12
2.6
12.26 6.53
13.0
41.5
5.1
2.42 18.83 9.17
1.74 12.72 8.61
11.99 2.48 10.42
--
[a] Measured by elemental analysis.[ b] Measured by AAS. [c]The crystal size was calculated
by Scherrer equation through the Co(111) diffraction peak.
The morphologies and metal dispersions of the catalysts were characterized by TEM. As
shown in Figure 1, the Co particles were well dispersed on the Nꢀdoped carbon when the
pyrolysis temperature was below 700 °C. The size of Co particle prepared at 500 °C was
around 6.4 nm (Table 1). At 600 °C, the size of the particles increased to 11.3 nm. Further
raising the temperature to 700 °C, the particle size increased slightly. However, a serious
aggregation happened when the temperature rose to 800 °C. The average particle size was
46.4 nm and the morphology of the support transformed to nanotubes. Therefore, the
pyrolysis temperature had a significant influence on the morphology and particle size of the
catalysts.
ACS Paragon Plus Environment

Page 11 of 34
ACS Catalysis
1
2
3
4
5
6
7
8
9
a)
d)
b)
c)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
f)
e)
Figure 1. TEM images of (a) CoNx@NCꢀ500, (b) CoNx@NCꢀ600,(c) CoNx@NCꢀ650, (d)
CoNx@NCꢀ700, (e) CoNx@NCꢀ800, (f) CoNx@NCꢀ650 after 4 runs
In order to investigate the crystal structure of the catalysts, XRD analysis was carried out.
Figure 2 shows the XRD patterns of the CoNx@NC catalysts. For NCꢀ650, only a broad peak
at 24° was detected, which was the diffraction peak of amorphous carbon. For CoNx@NC
catalysts, when the pyrolysis temperature was 500 °C, no diffraction peak of cobalt was
found from the XRD patterns, indicating that the cobalt species were amorphous at this
pyrolysis temperature. For CoNx@NCꢀ650, the diffraction peaks at 43.9°, 51.0° and 75.3°
which are closed to the (111), (200) and (220) planes of both Co0 (JCPDS 15ꢀ0806) and
Co4N (JCPDS 41ꢀ0943) (Figure S2). It is difficult to identify the Co0 and Co4N superficially
from XRD patterns because of their similar lattice structure and parameters (Table
S1). 57 , 58 , 59 , 60 To verify the component of the catalyst, partial XRD analyses of
CoNx@NCꢀ650, Co/NC (reduced by H2) and Co@Cꢀ650 from 41° to 54° were carried out
(Figure 3). According to the Co/NC and Co@C patterns, the diffraction peak at 44.5° could
ACS Paragon Plus Environment

ACS Catalysis
Page 12 of 34
1
2
3
4
5
6
7
8
9
be the (111) plane of Co0. From the standard PDF cards of Co4N and Co0, the diffraction
peak (111) of Co4N was about 0.5° lower than the Co0. Compare with Co/NC and Co@C,
the diffraction peak (111) of CoNx@NCꢀ650 shift to lower angle from 44.5° to 43.9°, which
was very close to the diffraction peak (111) of Co4N. Considering that the CoꢀN ratio and
structure may change with the reaction and preparation condition, and the peak also shifts
accordingly, the CoꢀN component in the catalysts was defined as CoNx. Stronger and sharper
diffraction peaks were observed in CoNx@NCꢀ700 (Figure 2), implying a higher ordering
and crystallinity of the cobalt species. The peak at 26° of CoNx@NCꢀ800 indexed to the (200)
plane of graphiteꢀtype carbon, indicating the graphitization of nitrogenꢀdoped carbon formed.
When the XRD pattern of CoNx@NCꢀ800 was enlarged (Figure S1), it could find that the
peaks were the overlap of Co0 and CoNx. Comparing with CoNx@NCꢀ600 and 650, the
diffraction peaks of Co species of CoNx@NCꢀ700 and 800 shifted to higher angle. Previous
research found that the Co4N could decompose to Co0 stepwise at elevated temperatures:
Co4N→Co3N + Co, Co3N→Co2N + Co, Co2N→CoN + Co.61 Maybe more Co0 was formed
from CoNx with the pyrolysis temperature increasing. Additionally, no peak of cobalt oxide
species was found.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment

Page 13 of 34
ACS Catalysis
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 2. XRD patterns of the CoNx@NC catalysts with different pyrolysis temperatures.
Figure 3. Partial XRD patterns of the CoNx@NCꢀ650, Co@Cꢀ650 and Co/NC. The peak
intensity of Co/NC has been reduced by 5 times.
In order to confirm the valence states of Co and N, XPS was used to analyze the catalysts.
Deconvolution of the N1s and Co2p regions by peak fitting for CoNx@NC catalysts is shown
in Figure 4. All of the binding energies were corrected by C1s and the binding energy of CꢀC
was 284.6 eV (Figure S3). Three distinct peaks were observed in the N1s spectra of
ACS Paragon Plus Environment

ACS Catalysis
Page 14 of 34
1
2
3
4
5
6
7
8
9
CoNx@NC. The peaks at binding energies of 398.6 eV, 400.5 eV and 402.3 eV can be
attributed to pyridineꢀtype, pyrroleꢀtype and quaternaryꢀtype nitrogen, respectively.62, 63 The
percentage of pyridineꢀtype nitrogen decreased with the increase of pyrolysis temperature
(Table 2). The contents of pyrrolꢀtype nitrogen increased first and then decreased, while the
quaternaryꢀtype nitrogen increased along with temperature. The trend of nitrogen content was
consistent with previous reports.42 The NC materials with different type nitrogen could
function as ‘heterogeneous Nꢀtype ligands’ to stabilize metal and improve the catalytic
activity.62 Some studies indicated that pyridineꢀtype nitrogen play an important role for ORR
activity and the quaternaryꢀtype nitrogen was the most active specie for catalyzing
hydrocarbon activation.51, 64
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Co2p3/2 spectra of the catalysts, the binding energies in 778.7 eV, 780.6 eV, 782.6 eV,
and 786.2 eV can be attributed to Co0, CoꢀO, CoꢀN and the satellite peak of CoꢀO,
respectively 54, 65. The existence of CoꢀO was because the cobalt ions could combine with O
in cellulose and O could partially retain during the pyrolysis process, which could be proven
by the XPS of C1s (Figure S3) that much CꢀO and C=O were presented in the CoNx@NC
catalysts. In addition, the surface of Co could be partially oxidized when the catalysts
exposed to air. These cobalt oxides were amorphous and revealed no diffraction peaks in
XRD patterns, as discussed above. Under low pyrolysis temperature, much O was retained to
form CoOx (Co2+, Co3+). For CoNx@NCꢀ500 catalyst, the content of CoꢀO was 62.5%.
Further increasing temperature, the content of CoꢀO decreased and reached 28.5% at 800 °C.
This trend could also be verified by the intensity decrease of the typical satellite peak of
CoꢀO. The percentage of CoꢀN increased first and then decreased with temperature
ACS Paragon Plus Environment

Page 15 of 34
ACS Catalysis
1
2
3
4
5
6
7
8
9
increasing. The CoNx@NCꢀ650 had a maximum value of CoꢀN as 32.9%. The percentage of
Co0 increased from 9.3% to 47.1% when the pyrolysis temperature increased from 500 °C to
800 °C (Table 2). It indicated that with pyrolysis temperature increasing, CoOx formed firstly
followed by CoNx with the substitution of N for O under ammonia atmosphere, and then the
CoNx would decompose to Co0 at higher pyrolysis temperature, which agreed well with the
XRD characterization.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 4. XPS spectra of the (a) N1s and (b) Co2p 3/2 of CoNx@NC catalysts
Table 2. Ratio analysis of the peaks in XPS spectra in CoNx@NC
Content %
Sample
Npyridin
59.7
59.1
56.1
51.4
31.0
Npyrrol
27.6
30.5
33.1
31.4
28.5
Nquaternary
12.6
CoꢀN
28.2
31.6
32.9
27.0
24.4
Co0
9.3
CoꢀO
62.5
47.8
43.8
43.0
28.5
CoNx@NCꢀ500
CoNx@NCꢀ600
CoNx@NCꢀ650
CoNx@NCꢀ700
CoNx@NCꢀ800
10.4
20.6
23.3
29.0
47.1
10.8
17.3
40.5
Catalytic Activity
ACS Paragon Plus Environment

ACS Catalysis
Page 16 of 34
1
2
3
4
5
6
7
8
9
The catalytic activities of the catalysts were tested by HDO of eugenol at 200 °C and 2
MPa. As shown in Table 3, catalysts with different pyrolysis temperature demonstrated
significant difference in activity. As the pyrolysis temperature increased, the catalytic activity
increased first and then decreased. For CoNx@NCꢀ500, in 1.5 h, the eugenol conversion was
5.2% and the products were dihydroeugenol and trace propylcyclohexanol (entry1). The
catalytic activity of CoNx@NCꢀ600 increased remarkably. The conversion of eugenol was
100% and the yield of propylcyclohexanol was 45.5%. Besides propylcyclohexanol and
dihydroeugenol, 15.6% yield of propylphenol that could be the intermediate was detected.
The CoNx@NCꢀ650 showed the highest catalytic activity with 100% conversion and 86.6%
yield of propylcyclohexanol (entry 3). The propylcyclohexanol yield reached 99.9% after 2 h
(entry 6). As the pyrolysis temperature further increasing, the catalytic activity decreased.
The propylcyclohexanol yield was 38.9% for CoNx@NCꢀ700 and only 3.7% for
CoNx@NCꢀ800 in 1.5 h. Among CoNx@NC catalysts, CoNx@NCꢀ500 had the most CoꢀO
content, CoNx@NCꢀ800 had the most Co0 content and CoNx@NCꢀ650 had the most CoꢀN
content. Because CoNx@NCꢀ650 showed the best performance, the cobalt nitrides in the
catalyst should play an important role in the catalytic process.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
In order to further explore the hypothesis, NCꢀ650, Co@Cꢀ650 and Co/NC were
synthesized and tested for catalyzing HDO of eugenol (Table 3, entry 6ꢀ9). The NCꢀ650
almost had no activity for eugenol conversion (2.9%). For Co@Cꢀ650, the conversion of
eugenol was 24.7% and no propylcyclohexanol was produced. From XRD pattern and XPS
of Co@Cꢀ650 (Figure S5 and Figure S6), Co0 was the main component of the catalyst, which
could come from the cobalt precursor reduced by the nonꢀcondensable reductive species (e.g.,
ACS Paragon Plus Environment

Page 17 of 34
ACS Catalysis
1
2
3
4
5
6
7
8
9
H2, CO, CxHy) produced during the fast pyrolysis of cellulose in the absence of oxygen.66,67,68
It indicated that the Co0 in our catalytic system was not the key factor for catalyzing eugenol
to propylcyclohexanol. To further investigate if the NC support can promote Co0 to catalyze
eugenol to produce propylcyclohexanol, the Co/NC was also synthesized for the test.
Although the conversion of eugenol increased to 100%, the yield of propylcyclohexanol was
only 0.6%. Therefore, the catalytic activity of CoNx@NCꢀ650 from eugenol to
propylcyclohexanol can mainly be ascribed to the CoNx.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
So far, equivalent of propylcyclohexanol has been achieved from eugenol under the
catalysis of CoNx@NCꢀ650. Propylcyclohexanol can be further converted to
propylcyclohexane, a C9 naphthene, via dehydration and hydrogenation. Because the
CoNx@NCꢀ650 catalyst is alkaline, acid can be added to the reaction system to help achieve
propylcyclohexane from eugenol. As shown in Table 4, when SiO2 and γꢀAl2O3 were added,
the products had no significant change (entries 2, 3). However, when HZSMꢀ5 was added to
the system, the main product was propylcyclohexane (96%) with small amount of
propylcyclohexene (3.2%) (entry 4). The propylcyclohexane yield reached 99.1% after the
reaction time prolonged to 2 h (entry 6). When homogeneous acid H3PO4 was added, no
propylcyclohexane was detected and the propylcyclohexanol yield was only 7.7%. The
catalyst was possibly destroyed by H3PO4 in the reaction system. Compared with entry 1 and
entry 4 (Table 4), the yield of propylcyclohexane (96%) was greater than propylcyclohexanol
(86.6%), indicating that the addition of HZSMꢀ5 could not only catalyze dehydration of
alcohol, but also promote the reaction rate. The catalysts with different pyrolysis temperature
ACS Paragon Plus Environment

ACS Catalysis
Page 18 of 34
1
2
3
4
5
6
were also tested to produce propylcyclohexane and the trend of catalytic activity was same as
that to produce propylcycohexanol.
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Table 3. HDO of eugenol over CoNx@NC catalysts
Yield %
Entry
Catalyst
Time (h)
Conversion(%)
1
2
0
3
1
2
3
4
5
6
7
8
9
CoNx@NCꢀ500
CoNx@NCꢀ600
CoNx@NCꢀ650
CoNx@NCꢀ700
CoNx@NCꢀ800
CoNx@NCꢀ650
NCꢀ650
1.5
1.5
1.5
1.5
1.5
2
5.2
100
100
100
100
100
2.9
0.5
45.5
86.6
38.9
3.7
99.9
0
4.6
38.8
4.7
9.3
90.2
0
15.6
8.6
48.7
4.7
0
2
0
2.9
21.7
99.1
Co@Cꢀ650
2
24.7
100
0
0
Co/NC
2
0.6
0.2
164 mg (1mmol) of eugenol, 10 ml of nꢀdodecane, the dosage of catalysts contained 5 mg of
cobalt. For CoNx@NCꢀ650, the content of cobalt was 6.53 wt% and the dosage of the
catalyst was 76 mg.
ACS Paragon Plus Environment

Page 19 of 34
ACS Catalysis
Table 4. HDO of eugenol over CoNx@NC with acid
Conversion
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Yield(%)
3
(%)
100
100
100
100
100
100
58.6
100
100
100
Entry
Catalyst
Additives
ꢀꢀ
1
0
2
0
4
8.6
7.1
6.4
0
5
4.7
5.6
6.8
0
1
2
CoNx@NCꢀ650
CoNx@NCꢀ650
CoNx@NCꢀ650
CoNx@NCꢀ650
CoNx@NCꢀ650
CoNx@NCꢀ650
CoNx@NCꢀ500
CoNx@NCꢀ600
CoNx@NCꢀ700
CoNx@NCꢀ800
86.6
85.8
85.7
0
SiO2
0
0
3
Al2O3
0
0
4
HZSMꢀ5
H3PO4
96
0
3.2
0
5
6a
7.7
8.7
0
83.6
0
HZSMꢀ5
HZSMꢀ5
HZSMꢀ5
HZSMꢀ5
HZSMꢀ5
99.1
0
0.6
0
0
7
0.5
1.3
0
56.2
0
8
87.1
24.6
3.4
11.3
24.9
3.5
0.5
9
3.7
11.5
10.6
30.1
80
10
2.5
164 mg (1mmol) of eugenol, 50 mg of additives (SiO2, Al2O3 or HZSMꢀ5) or with 0.2 wt%
H3PO4, 10 ml of nꢀdodecane, the dosage of catalysts contained 5 mg of cobalt. [a] reaction
time 2 h.
Temperature is an important parameter for a reaction. Figure 5 shows the results of
HDO of eugenol at different reaction temperature over CoNx@NCꢀ650 catalyst. When the
reaction temperature was 170 °C, the product was dihydroeugenol. When the temperature
reached 180 °C, propylcyclohexane started to generate and accompanied by a series of
intermediate products. The yield of propylcyclohexane increased and reached 31.8% at
190 °C. A sharp increase happened when the temperature was 200 °C and the
propylcyclohexane yield increased to 99.1%. The reaction rates at different reaction
ACS Paragon Plus Environment

ACS Catalysis
Page 20 of 34
1
2
3
4
5
6
7
8
9
temperatures were calculated. At 170 °C, only allyl group was hydrogenated. With the
temperature increasing from 190 °C to 200 °C, the reaction rate accelerated greatly from 1.87
hꢀ1 to 5.84 hꢀ1, indicating that the conversion of eugenol to propylcyclohexane is
temperatureꢀsensitive reaction (Table S2).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
The effect of hydrogen pressure on eugenol HDO was also studied (Figure 6). When the
hydrogen pressure was 0.5 MPa, the main product of the reaction was dihydroeugenol and
trace intermediates. The yield of propylcyclohexane increased from 34.6% to 93.6% when
the pressure increased from 1 MPa to 1.5 MPa. The yield was greater than 99% when the
pressure increased to 2 MPa. Interestingly, when the pressure was 1 MPa, nearly 30% of
cycloꢀolefin generated, indicating that in this reaction system, the hydrogenation of
cycloꢀolefin was slow under low hydrogen pressure.
Figure 5. Effect of reaction temperature. Reaction conditions: 164 mg (1mmol) of eugenol,
50 mg of HZSMꢀ5, 10 mL of nꢀdodecane, 76 mg of CoNx@NCꢀ650, 2 MPa H2, 2 h.
ACS Paragon Plus Environment

Page 21 of 34
ACS Catalysis
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 6. Effect of reaction pressure. Reaction conditions: 164 mg (1mmol) of eugenol, 50
mg of HZSMꢀ5, 10 mL of nꢀdodecane, 76 mg of CoNx@NCꢀ650, 200 °C, 2 h.
Mechanism
In order to explore the mechanism of CoNx@NCꢀ650 catalyzed HDO of eugenol, we
tracked and analyzed the distribution of products at different reaction time (Figure 7). At
200 °C and 2 MPa H2, eugenol was completely converted into dihydrogeneugenol by
hydrogenation of allyl group in the initial 10 min. Trace intermediates were detected as
4ꢀpropylphenol, 4ꢀpropylcyclohexanol and 4ꢀpropylcyclohexene. With the extension of
reaction time, the content of dihydroeugenol decreased rapidly and disappeared in 60 min.
Meanwhile, the 4ꢀpropylphenol was also disappeared. Other intermediates increased first and
then decreased gradually. The 4ꢀpropylcyclohexanol disappeared in 90 min. However, the
4ꢀpropylcyclohexene decreased very slowly and disappeared until 150 min.
The
hydrogenation of 4ꢀpropylcyclohexene was slow and became the rate control step. Based on
the above results, we proposed a possible reaction pathway (Figure 8). Eugenol was
hydrogenated to dihydroeugenol with a very fast reaction rate. Then the Caryl–OCH3 of
ACS Paragon Plus Environment

ACS Catalysis
Page 22 of 34
1
2
3
4
5
6
7
8
9
dihydroeugenol was cleaved by the cobalt catalyst. The aromatic ring of 4ꢀpropylphenol was
then hydrogenated to 4ꢀpropylcyclohexanol and dehydrated to propylcyclohexene under the
catalysis of cobalt catalyst and solid acid HZSMꢀ5. Finally, the propylcyclohexene was
hydrogenated to the propylcyclohexane. This pathway suggests that the mechanism of
catalyzing methoxyphenols to the corresponding cycloalcohols by CoNx@NC is different
from other catalysts like Pd, Ru and Ni. Previous reports show that hydrogenation of the
aromatic ring is prior to the hydrolysis of Caryl–OCH3 for Pd19, Ru25or occurs in parallel for
Ni69. Pd/C, Ru/C and Ni/C were tested under the same reaction system and the results were
consistent with the previous researches (Table S3). Generally, compared with phenolic
monomers, the corresponding fully hydrogenated products are more stable due to the steric
hindrance and electronic effect that restrain the cleavage of Calkyl–OR.27,69 In this reaction,
2ꢀmethoxyꢀ4ꢀpropylcyclohexanol was not detected, indicating that the CoNx@NCꢀ650
catalyst could selectively cleave Caryl–OCH3 bond to 4ꢀpropylphenol without producing
2ꢀmethoxyꢀ4ꢀpropylcyclohexanol. This may be the reason why the catalyst could catalyze
HDO of eugenol with high yield of propylcyclohexanol under milder conditions.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
In order to further verify the reaction mechanism, the 2ꢀmethoxyꢀ4ꢀpropylcyclohexanol
was synthesized and used as the reactant under the same reaction conditions (Table S4). Only
12.1%
conversion
of
2ꢀmethoxyꢀ4ꢀpropylcyclohexanol
was
obtained.
2ꢀMethoxyꢀ4ꢀpropylcyclohexanol should have been detected if it was produced in eugenol
conversion. It further proved that the catalyst could selectively cleave Caryl–OCH3 bond
before hydrogenating the aromatic ring. 47% yield of methanol was detected when the
eugenol was totally converted with 88.8% total yields of propylcyclohexanol and
ACS Paragon Plus Environment

Page 23 of 34
ACS Catalysis
1
2
3
4
5
6
7
8
9
4ꢀpropylphenol (83.2% and 5.6%, respectively). The gas products were analyzed, only
hydrogen and methane were detected after the reaction (98.5% and 1.5% of volume fraction,
respectively). The yield of methane was 40.3%. Based on previous research,27 methane could
be produced from methanol under the reaction condition. All of these verified that the
CoNx@NCꢀ650 catalyst had good property to cleave Caryl–OCH3 bond.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 7. Product distributions as functions of time for CoNx@NCꢀ650 catalyst. Reaction
conditions: 164 mg (1mmol) of eugenol, 50 mg of HZSMꢀ5, 76 mg of CoNx@NCꢀ650, 10
ml of nꢀdodecane, 2 MPa H2, 200 °C.
Figure 8. Proposed reaction pathway.
ACS Paragon Plus Environment

ACS Catalysis
Page 24 of 34
1
2
3
4
5
6
7
8
HDO of other phenolic compounds
In order to investigate the applicability of the catalyst
compounds were evaluated under 2 MPa H2, 200 °C for 2 h (Table 5). For the phenolic
compounds like phenol, guaiacol, 3ꢀmethoxyphenol, 3ꢀisopropylphenol and
，
other ligninꢀderived phenolic
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
4ꢀisopropylphenol, the catalyst showed a high catalytic activity and the yield of naphthene
were greater than 95%. Compared with guaiacol and 3ꢀmethoxyphenol, the HDO of catechol
and resorcinol was more difficult and the yield of cyclohexane was 5.2% and 45%,
respectively (entry 8 and 10), probably because the substrates were difficult to dissolve in
dodecane. After prolonging the reaction time to 8 h, the cyclohexane yield was greater than
98% (entry 9 and 11). For 2,6ꢀdimethoxyphenol, the conversion was 43.4% and the
cyclohexane yield was 9.1%. In addition to cyclohexane, 9.7% yield of guaiacol was detected.
It further verified the mechanism that proposed above. 99.9% yield of cyclohexane was
achieved when the reaction time was 12 h. Diphenyl ether has also been used to evaluate the
catalyst activity and achieved a good result. When hydroxyl was existed in paraꢀposition, the
yield of cyclohexane decreased to 65% (entry 13). However, equivalent of cyclohexane was
produced when the reaction time was 8 h (entry 14). All of the above results suggest that the
CoNx@NCꢀ650 catalyst has a high HDO activity for various phenolic compounds under mild
conditions.
ACS Paragon Plus Environment

Page 25 of 34
ACS Catalysis
1
2
3
4
5
6
7
Table 5. HDO of other phenolic compounds
8
9
Conversion
(%)
Entry
Substrates
Products
Yield(%)
91
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
2
3
100
100
100
99.6
95
9.1
4
43.4
9.7
5a
6
100
100
99.9
98.2
99.9
7
100
5.2
8
100
100
100
62.4
99.9
45
9bd
10
43.2
98.6
92
11bd
12c
100
100
100
100
13c
65
14bc
99.9
ACS Paragon Plus Environment

ACS Catalysis
Page 26 of 34
1
2
3
4
5
6
7
8
9
Reaction conditions: 1mmol of Substance, 50 mg of HZSMꢀ5, 10 mL of nꢀdodecane, 76 mg
of CoNx@NCꢀ650, 2 MPa H2, 200 °C for 2 h. [a] Reaction time was 12 h. [b] Reaction time
was 8 h. [c] The dosage of the substance was 0.5 mmol and the yield was calculated by 1mol
substance generate 2 mol cyclohexane. [d] The dosage of HZSMꢀ5 was 100mg.
Recyclability of the Catalyst
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
The stability of CoNx@NCꢀ650 catalyst was investigated by catalyzing eugenol to
propylcyclohexanol. The results of the recycle experiments are shown in Figure 9. After four
runs, the yield of propylcyclohexanol had a certain decrease. In order to analyze the reasons
for deactivation of the catalyst, some characterizations were carried out. From the TEM
image (Figure 1f), no apparent aggregation of cobalt (13.5 nm) was found after recycles.
However, from the XRD patterns (Figure S8), the peaks of the catalyst shifted and the peak
intensities decreased after the recycles, indicating that the cobalt nitrides had a certain loss.
The elemental analysis showed that the N content decreased from 11.32% to 10.5% and AAS
analysis indicated that the Co content decreased from 6.53% to 5.88% after four runs.
Moreover, the catalyst would have a loss during the separation processes. All of these would
lead to a decrease in the product yield. We will continue to study this kind of catalysts to
improve the stability in the future work.
ACS Paragon Plus Environment

Page 27 of 34
ACS Catalysis
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 9. Recycle of the catalyst. Reaction conditions: 164 mg (1mmol) of eugenol, 10 mL of
nꢀdodecane, 76 mg of CoNx@NCꢀ650, 2 MPa H2, 200 °C, 2 h.
CONCLUSIONS
A simple method with cellulose as the carbon source, cobalt nitrate as the metal source and
ammonia as nitrogen source has been proposed for preparation of CoNx@NC catalysts.
Under the high temperature and ammonia atmosphere, the cobalt ions formed cobalt nitrides
that play an important role in the catalytic HDO reactions. The Nꢀdoped carbon support can
help to promote the reaction. Using eugenol as a model compound, the CoNx@NCꢀ650
exhibited an excellent HDO activity. The conversion of eugenol was 100% and the yield of
propylcyclohexanol was greater than 99.9% under 2 MPa H2, 200 °C for 2 h. Moreover, high
yield of propylcyclohexane (99.1%) could be achieved when solid acid HZSMꢀ5 was added
to the reaction system. The reaction pathway is different from other catalysts like Pd, Ru and
Ni. It can selectively cleave Caryl–OCH3 bond to 4ꢀpropylphenol before the hydrogenation of
the aromatic ring, which could be the main reason that the catalyst can catalyze HDO of
ACS Paragon Plus Environment

ACS Catalysis
Page 28 of 34
1
2
3
4
5
6
eugenol under mild conditions. Moreover, this catalyst showed a high HDO activity for
various phenolic compounds.
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ASSOCIATED CONTENT
Supporting Information
The enlarged XRD pattern of the CoNx@NCꢀ800 catalyst, standard PDF card and TCPDS
dates of Co0 and Co4N, XRD, XPS of Co@Cꢀ650 and Co/NC, TPR, catalyst recycle and
XRD analysis, XPS and XRD of CoNx@NCꢀ650 before and after reaction, GCꢀMS of
substrates are provided in supporting information. This material is available free of charge via
the Internet at http://pubs.acs.org.
Acknowledgements
The authors are also grateful to NSFC (21572213, 21325208), the National Basic Research
Program of China (2012CB215306), Anhui Provincial Natural Science Foundation
(1408085MKL04), Program for Changjiang Scholars and Innovative Research Team in
University of the Ministry of Education of China and the Fundamental Research Funds for
the Central Universities (wk 2060190040) for the financial support.
AUTHOR INFORMATION
Corresponding Author
Eꢀmail addresses: zhzhying@ ustc.edu.cn
REFERENCES
(1) Stöcker, M. Angew. Chem. Int. Ed. 2008, 47, 9200ꢀ9211.
ACS Paragon Plus Environment

Page 29 of 34
ACS Catalysis
1
2
3
4
5
(2) Kunkes, E. L.; Simonetti, D. A.; West, R. M.; SerranoꢀRuiz, J. C.; Gärtner, C. A.;
6
7
8
9
Dumesic, J. A. Science 2008
(3) Huber, G. W.; Iborra, S.; Corma, A. Chem. Rev. 2006
(4) Mohan, D.; Pittman, C. U.; Steele, P. H. Energy Fuels 2006
(5) Singh, S. K.; Ekhe, J. D. RSC Adv 2014, 4, 27971ꢀ27978.
(6) Xu, L.; Yao, Q.; Deng, J.; Han, Z.; Zhang, Y.; Fu, Y.; Guo, Q. ACS Sustainable. Chem.
Eng. 2015 , 2890ꢀ2899.
, 322, 417ꢀ421.
,
106, 4044ꢀ4098.
20, 848ꢀ889..
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
,
.
,
3
(7) Yan, N.; Zhao, C.; Dyson, P. J.; Wang, C.; Liu, L. T.; Kou, Y. ChemSusChem 2008, 1,
626ꢀ629
(8) Zhao, Y.; Xu, Q., Pan, T.; Zuo, Y., Fu, Y.; Guo, Q. X. Appl. Catal., A 2013, 467,
504ꢀ508.
(9) Resasco, D. E. J. Phys. Chem. Lett. 2011
(10) Furimsky E. Appl. Catal., A 2000 199, 147ꢀ190.
(11) De la Puente, G.; Gil, A., Pis, J. J.; Grange, P. Langmuir
, 2, 2294ꢀ2295.
,
,
1999, 15, 5800ꢀ5806.
(12) Jongerius, A. L.; Jastrzebski, R.; Bruijnincx, P. C.; Weckhuysen, B. M. J. Catal. 2012
,
285, 315ꢀ323.
(13) Lin, Y. C.; Li, C. L.; Wan, H. P.; Lee, H. T.; Liu, C. F. Energy Fuels 2011
(14) Elliott, D. C. Energy Fuels 2007 21, 1792ꢀ1815
(15) Laurent, E.; Delmon, B. J.Catal.1994 146, 281ꢀ291.
(16) Centeno, A.; Laurent, E.; Delmon, B. J. Catal. 1995
(17) Viljava, T. R.; Komulainen, R. S.; Krause, A. O. I. Catal. Today 2000
, 25, 890ꢀ896
,
,
,
154, 288ꢀ298
,
60, 83ꢀ92
(18) Xu, G.; Guo, J.; Zhang, Y.; Fu, Y.; Chen, J.; Ma, L.; Guo, Q. ChemCatChem 2015, 7,
2485ꢀ2492.
(19) Zhao, C.; Kou, Y.; Lemonidou, A. A.; Li, X.; Lercher, J. A. Angew. Chem. 2009, 121,
4047ꢀ4050
ACS Paragon Plus Environment