Synthesis of renewable C-C cyclic compounds and high-density biofuels using 5-hydromethylfurfural as a reactant

Article abstract of DOI:10.1039/d0gc00195c

The major challenge in the synthesis of high-density biofuels is to identify the bio-based source for C-C cyclic compounds and C-C coupling reactions with a suitable selectivity. Herein, we selectively synthesize 1,2,4-benzenetriol (BTO) with a yield of 51.4% from cellulose-derived 5-hydromethylfurfural via a ring-rearrangement reaction. The cellulose-derived route is a more meaningful route for the C-C cyclic compounds compared to the traditional hemicellulose- and lignin-derived routes. Furthermore, BTO is very easily dimerized via a C-C oxidative coupling reaction, showing a yield of 94.4% and selectivity of nearly 100% under environmentally friendly reaction conditions. After hydrodeoxygenation, bicyclohexane is obtained with a yield of 87.4%. This work not only provides a promising route to produce C-C cyclic fine compounds based on a cellulose-derived route, but also shows a highly efficient synthesis route for high-density biofuels via the C-C oxidative coupling reaction.

Full text of DOI:10.1039/d0gc00195c

View Article Online
View Journal
Green
Chemistry
Cutting-edge research for a greener sustainable future
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: T. Cai, Q. Deng,
H. Peng, J. Zhong, R. Gao, J. Wang, Z. Zeng, J. Zou and S. Deng, Green Chem., 2020, DOI:
10.1039/D0GC00195C.
Volume 20
This is an Accepted Manuscript, which has been through the
Number
May 2018
Pages 1919-2160
9
7
Royal Society of Chemistry peer review process and has been
accepted for publication.
Green
Chemistry
Cutting-edge research for a greener sustainable future
rsc.li/greenchem
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
shall the Royal Society of Chemistry be held responsible for any errors
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
ISSN 1463-9262
PAPER
Paul T. Anastas et al.
The Green ChemisTREE: 20 years after taking root with the 12
principles
rsc.li/greenchem

Please do not adjust margins
Page 1 of 7
Green Chemistry
View Article Online
DOI: 10.1039/D0GC00195C
Green Chemistry
ARTICLE
Synthesis of renewable C-C cyclic compounds and high-density
biofuel using 5-hydromethylfurfural as a reactant
Taimei Caia, Qiang Denga,b*, Hailong Penga, Jin Zhonga, Rui Gaoa, Jun Wanga, Zheling Zenga, Ji-Jun
Received 00th January 20xx,
Accepted 00th January 20xx
Zouc*, Shuguang Denga,b
*
DOI: 10.1039/x0xx00000x
The major challenge in the synthesis of high-density biofuel is to identify biobased source of C-C cyclic compounds and C-C
coupling reactions with a suitable selectivity. Herein, we selectively synthesize 1,2,4-benzenetriol (BTO) with a yield of 51.4%
from cellulose-derived 5-hydromethylfurfural via a ring-rearrangement reaction. The cellulose-derived route is a more
meaningful route for C-C cyclic compounds compared to the traditional hemicellulose- and lignin-derived routes.
Subsequently, BTO is very easily dimerized via a C-C oxidative coupling reaction, presenting a yield of 94.4% and selectivity
of nearly 100% at environmentally friendly reaction conditions. After hydrodeoxygenation, bicyclohexane is obtained with
a yield of 87.4%. This work not only provides a promising route to produce C-C cyclic fine compounds based on a cellulose-
derived route but also shows a highly efficient synthesis route for high-density biofuel via the C-C oxidative coupling reaction.
www.rsc.org/
and subsequent hydrodeoxygenation reaction. Usually,
renewable jet fuel linear alkanes with a density lower than 0.79
g·mL-1 have been widely synthesized via aldol condensation of
Introduction
High-density jet fuel consisting of cycloalkanes has a higher
density and volumetric heat value than conventional jet fuels. It
is an indispensable propellant for volume-limited aircraft (e.g.,
missiles and rockets) because of extended flight distance and
loading capacity.1 Conventionally, the synthesis of high-density
jet fuel is mainly based on petroleum-based cyclopentadiene.1
Due to the excessive depletion of petroleum and the massive
amount of greenhouse gas emissions, substantial efforts have
been devoted to the production of high-density fuels from
renewable biomass.2 Lignocellulosic biomass represents an
attractive renewable feedstock that can be mainly converted
into three main families of compounds: (1) small oxygenates
(e.g., acetone, butanol and ethanol); (2) hemicelluloses- and
acetone with furan aldehydes (e.g., furfural, 5-
hydroxymethylfurfural) or alkylation of acetone with 2-methyl
4,5
furan.
To increase the fuel density, many C-C coupling
strategies have been adopted to upgrade biomass derivatives
with a C-C ring structure to high-density cyclic fuels. For
example, some branched monocycloalkanes with a density of
0.80-0.84 g ml-1 are synthesized via the aldol condensation of
cyclic ketones (e.g., cyclopentanone, cyclohexanone) and
furanic aldehydes,6 aldol condensation of furanic aldehydes and
isophorone,7 alkylation of 2-methylfuran and cyclic ketones,8
alkylation of aromatic oxygenates with furfural alcohol.9
Meanwhile, Some bicycloalkanes with a density of 0.86-0.89 g
ml-1 are synthesized via the aldol self-condensation of cyclic
ketones (e.g., cyclopentanone, cyclohexanone),10 alkylation of
phenols with benzyl ether or benzyl alcohols,11
celluloses-derived
compounds
(e.g., furfural,
5-
hydroxymethylfurfural, 2-methyl furan, furfural alcohol); and
(3) lignin-derived compounds (e.g., guaiacol, anisole, phenol,
benzyl ether, benzyl alcohols).3 To synthesize jet fuel with
carbon chains consisting of 10-17 carbons, these small-
molecule compounds are required to undergo a C-C coupling
dehydration/oligomerization/rearrangement
of
cyclopentanol,12 reductive coupling of cyclopentanone,13 and
photoinduced cycloaddition of isophorone and olefin.14 Among
these reactions, the aldol self-condensation of cyclic ketones
has attracted wide attention because of easy operation and a
a Key Laboratory of Poyang Lake Environment and Resource Utilization (Nanchang
University) of Ministry of Education, School of Resource, Environmental and
Chemical Engineering, Nanchang University, No. 999 Xuefu Avenue, Nanchang
330031, PR China
b School for Engineering of Matter, Transport and Energy, Arizona State University,
551 E. Tyler Mall, Tempe, AZ 85287, USA
higher
density
of
bicycloalkanes
than
branched
monocycloalkanes.10
Currently, the biomass-derived route of aforementioned C-
C six-membered ring aromatic oxygenates (phenol, anisole,
guaiacol) are mainly synthesized via the fast pyrolysis of lignin
with a natural aromatic structure.15 Even, cyclohexanone
c Key Laboratory for Green Chemical Technology of the Ministry of education, School
of Chemical Engineering and Technology, Tianjin University; Collaborative
Innovative Center of Chemical Science and Engineering (Tianjin), No.92 Weijin
Road, Tianjin 300072, PR China
requires
further
conversion
by
the
selective
E-mail: Shuguang.Deng@asu.edu (Shuguang Deng); jj_zou@tju.edu.cn (Ji-Jun Zou); hydrodeoxygenation of lignin-derived phenols.16 Unfortunately,
dengqiang@ncu.edu.cn (Qiang Deng).
because of the complicated structure of lignin, the product
composition of the fast pyrolysis is complex, and the yield of
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
target aromatic molecules is very low. On the other hand, some
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 2 of 7
ARTICLE
Journal Name
C-C five-membered ring compounds (e.g., cyclopentanone and directly hydrolyzed to a 1,5-dicarbonyl compound, and then
View Article Online
DOI: 10.1039/D0GC00195C
cyclopentanol) can be selectively synthesized by the converted to BTO with a C-C six-membered ring structure by the
hydrogenative ring-rearrangement of hemicelluloses-derived intramolecular aldol, and subsequent dehydration steps.
furfural (Scheme 1).17 In the hydrogenative ring-rearrangement Subsequently, some other groups mentioned BTO as a by-
reaction process, furfural can convert to 2,5-dicarbonyl product in the transformation of HMF or fructose.21 Until
compound via subsequent C=O hydrogenation, hydrolysis and recently, Deussʼs group synthesized BTO as the main product
dehydration steps. Then, 2,5-dicarbonyl compound can build a with a yield of 54% from HMF via Lewis acid catalysis under a
C-C five-membered ring structure by a intramolecular aldol step, reaction temperature of 400 °C.22 Interestingly, BTO is unstable
and cyclopentanone and cyclopentanol are synthesized after and easily generates a dimer via a C-C oxidative coupling.
the followed hydrogenation and dehydration steps. These Although the dimerization is considered as a side reaction in
synthesis routes for C-C five-membered ring compounds are their work, which inspired us to synthesize a C-C six-membered
limited because the amount of hemicellulose precursor is low.3 ring compound from 5-hydroxymethylfurfural and develop an
Similar to the formation of furfural, cellulose can be advanced synthesis route for bicycloalkanes.
transformed to 5-hydroxymethylfurfural (HMF) via hydrolysis
To the best of our knowledge, although the C-C coupling
and subsequent hydration reactions. Compared with furfural, 5- reaction of biomass derivatives has been widely reported for
hydroxymethylfurfural is a more promising platform compound the synthesis of biofuel, a green and efficient C-C oxidative
because the amount of cellulose precursor is much higher than coupling reaction has not been reported yet. Herein, we report
hemicelluloses precursor. Hence, the conversion of HMF is for the first time a novel route to synthesize high-density fuel
more meaningful. Recently, 5-hydroxymethylfurfural used as a directly using HMF as feedstock (Scheme 1). The reaction
feedstock for the synthesis of various high-valued compounds, process consists of three steps, including the ring-
including
2,5-furandicarboxylic
acid,
2,5- rearrangement of HMF to BTO, C-C oxidative coupling reaction
dihydroxymethyltetrahydrofuran, 2,5-furandimethanol, 2,5- of BTO to the dimer, and the hydrodeoxygenation of the dimer
dimethylfuran, linear alcohols, and so on.18 Similar to the to high-density bicycloalkanes.
hydrogenative
ring-rearrangement
of
furfural
to
cyclopentanone, HMF has been used for the synthesis of C-C
five-membered ring compounds (e.g., 3-hydromethyl
cyclopentanone and 3-hydromethyl cyclopentanol).19 In
contrast, the use of HMF to synthesize C-C six-membered ring
compounds is rarely reported. It should be mentioned that,
besides the synthesis of high-density fuel, the C-C ring
compounds are important fine chemicals, which are widely
used for the synthesis of medicines, spices, pesticides, dyes, and
rubber.7a The synthesis of C-C six-membered compounds from
HMF means a selective route from cellulose rather than the
traditional low efficient route from lignin.
Experimental
Materials and Characterizations
Acetic acid, cyclohexane, Al2O3 and Nb2O5 were obtained
from Xi Long scientific Co., China. 5-Hydroxymethylfurfural and
5-methylfurfural were purchased from Beijing Fang Cheng
Biotechnology Co., China. 1,2,4-benzenetriol and 1,4-
benzenediol were supplied by Sigma-Aldrich. Pd/C (5 wt%),
terephthalic acid and formic acid were obtained from Aladdin
Industrial Co.. ZrO2, TiO2, benzoic acid, 1,2,4-benzenetriol and
monochloroacetic acid were purchased from Shanghai Mackin
Co., China. All chemicals were reagent grade and used without
further purification. HZSM-5 (SiO2/Al2O3 = 27) supplied by
Nankai Catalysts Co., China, was calcined in air for 12 h at 550
°C.
The specific surface area and pore size were obtained by
performing N2 adsorption-desorption at -196 °C on an ASAP
2046 surface analyzer. The acid amount was characterized by
determining the temperature-programmed desorption of
ammonia (NH3-TPD) on a Micromeritics AutoChem II 2920
instrument.
Ring-rearrangement of HMF
The ring-rearrangement of HMF was conducted in a 2 mL
stainless-steel reactor. Typically, a mixture of HMF (0.04 mmol),
water (1.0 mL) and the catalyst (8.75 mmol acid amount of
liquid acids or 0.42 mmol acid amount of solid acids) was added
into the reactor, then heated to target temperature, and
sampled periodically. If not mentioned, the reaction
temperature is 300 °C, and the duration of the reaction was 15
min. The liquid products were qualified by liquid
chromatography-mass spectrometry (LC-MS, Triple TOF
5600/Agilent QTOF 6545 mass spectrometer detector), and
Scheme 1. Synthetic routes for the production of C-C ring compounds and
bicycloalkanes.
About thirty years ago, van Bekkumʼs group optimized the
reaction conditions for the ring-rearrangement reaction of HMF
to 1,2,4-benzenetriol (BTO) and achieved a yield of up to 25% at
reaction temperatures ranging from 330-350 °C.20 Different
from the hydrogenative ring-rearrangement reaction, HMF is
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 7
Green Chemistry
Please do not adjust margins
Journal Name
ARTICLE
quantified by high performance liquid chromatography The active furan ring, carbonyl and hydroxyl groups in HMF,
View Article Online
(UltiMate 3000) equipped with an ultraviolet visible intermediates and BTO can easily to trigger
DOI: 10.1039/D0GC0s0o19m5Ce
spectrophotometer detector (detection wavelength: 293 nm) intermolecular C-C coupling reactions, and the generation of
and C18 column (Zorbax Eclipse Plus, 4.6 mm × 250 mm, 5 μm). large molecular compounds results in carbon loss. Interestingly,
The mobile phase was consisted of methanol and water some 5-methylfurfural and 1,4-benzenediol were also
(volume ratio = 1:9 ) with a flow rate of 0.8 ml·min-1. The column synthesized. Combined with previous work, H2 can be in situ
was operated at 25 °C. Meanwhile, the gaseous products were generated by the decomposition of formic acid that is the
analyzed by gas chromatography (GC, Agilent 7890B) equipped hydration product of HMF.23 The in situ generated H2 is
with a FID detector and Hayesep Q 80/100 mesh packed detected by GC (Figure S2). The production of 5-methylfurfural
column (1.8 m × 2 mm). Only hydrogen can be measured in the may be ascribed to the reduction of HMF by H2.24 Similar to
gaseous products. The concentrations of liquid products were HMF, 5-methylfurfural can be converted to 1,4-benzenediol via
determined using calibration curves obtained by an internal the ring-rearrangement reaction. To verify the reaction
standard. The rest was defined as carbon loss. The reported mechanism, 5-methylfurfural was directly used as a reactant,
data were the mean values of three trials with small error bars. and 1,4-benzenediol was obtained with an approximately 10%
Dimerization of BTO
yield of BTO after 15 min (Figure S3). Likewise, a large quantity
of humins was generated by the intermolecular C-C coupling
reaction. Finally, 99.3% conversion of HMF was achieved, and a
38.7% yield of BTO and a 0.6% yield of 1,4-benzenediol were
generated after 15 min.
The dimerization of BTO was performed in a three-necked
round-bottomed flask. A mixture of BTO (1 mmol) and water (60
mL) was heated to 100 °C under an air atmosphere. After a
certain reaction time, the product was qualified by LC-MS, and
quantified by high-performance liquid chromatography. The
structure of the product was also determined by 13C NMR
spectra collected on a Varian Inova 500 MHz NMR.
Hydrodeoxygenation of dimer
The hydrodeoxygenation of dimer was carried out in a 100
ml batch autoclave (Anhui Kemi Machinery Technology Co.,
LTD) equipped with mechanical stirring. A mixture of dimer (1.2
mmol), HZSM-5 (1.00 g), Pd/C (0.08 g), water (15 mL) and
cyclohexane (15 mL) were added to the autoclave and heated
to 240 °C under 8.0 MPa H2 pressure. After a certain reaction
time, the reaction mixture was quenched in a cold-water bath.
The products in cyclohexane solution were qualified by gas
chromatography-mass spectrometry (GC-MS, Agilent 6890 N
GC/5973 MS detector) and quantified by gas chromatography
(Thermo TRACE-1300) equipped with a FID detector and TG-
WAXMS capillary column (30 m × 0.32 mm, 0.25μm). The
products in aqueous solution were extracted with ethyl acetate,
then qualified by LC-MS and quantified by high-performance
liquid chromatography.
(C)100
100
(B)
HMF
5-Methylfurfural
1,4-Benzenediol
BTO
80
80
60
40
20
0
HMF
BTO
5-Methylfurfural
1,4-Benzenediol
60
40
20
0
d
i
d
d
i
r
c
a
Z
d
d
i
O 2
i
T
b
O 5
5
-
M
i
O 2
c
z
r
i
i
e
O 3
c
a
n
e
c
c
a
c
i
h
l
a
o
c
a
c
i
c
2
c
2
i
c
N
A
c
S
t
i
t
e
c
o
l
Z
H
a
m
a
o
r
A
t
h
p
e
F
r
B
o
e
l
h
T
0
5
10
15
20
25
o
n
o
M
Reaction time (min)
100
100
(D)
(E)
HMF
HMF
5-Methylfurfural
1,4-Benzenediol
BTO
5-Methylfurfural
1,4-Benzenediol
BTO
80
60
40
20
0
80
60
40
20
0
Results and Discussion
Ring-rearrangement of HMF
As shown in Figure 1A, the ring-rearrangement of HMF to
BTO involves a hydrolysis ring-opening reaction to a 6-hydroxy-
5
0
.
5
.
2
.
5
7
.
3
4
0
8
2
0
0
0
2
5
0
6
2
7
.
5
7
6
3
3
3
1
2
8
Acid amount (mmol)
Temperature (C)
hexane-1,2,5-trione intermediate with
a
1,5-dicarbonyl
structure, intramolecular aldol condensation reactions to 2,3-
dihydroxy-cyclohexane-1,4-dione, and a dehydration reaction
to BTO. Figure 1B shows the catalytic kinetics under acetic acid
catalysis. A trace amount of 6-hydroxy-hexane-1,2,5-trione is
detected in LC-MS (Figure S1), confirming the reaction
mechanism. Additionally, the result also indicates that the
intramolecular aldol and dehydration reactions occurred
quickly, and that the ring-opening reaction is a rate-limiting
step. HMF was gradually transformed with the extension of
reaction time. However, the yield of BTO first increased and
then decreased, and a large quantity of humins was generated.
Figure 1. (A) Proposed reaction pathway for BTO preparation, (B) time-dependent
product distribution using acetic acid as a catalyst, (C) catalytic performance of
several acid catalysts, (D) effect of reaction temperature, (E) effect of amount of
acetic acid. Reaction conditions: (B) HMF (0.04 mmol), acetic acid (8.75 mmol),
water (1 mL), 300 °C; (C) HMF (0.04 mmol), liquid acids (8.75 mmol acid amount)
or solid acids (0.42 mmol acid amount), 300 °C, reaction time 15 min; (D) HMF (0.04
mmol), water (1 mL), reaction time 15 min; (E) HMF (0.04 mmol), acetic acid (43.75
mmol), water (1 mL), 300 °C, reaction time 15 min.
Then, we compared some common homogeneous acids
(such as terephthalic acid, benzoic acid, formic acid,
monochloroacetic acid and acetic acid) with the same acid
amount (Figure 1C). All of these homogeneous acids showed a
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 4 of 7
ARTICLE
Journal Name
near 100% catalytic activity, indicating that HMF is easily selectivity of the dimer was 100% and no other bypVrioewduArctitcslewOnelirnee
DOI: 10.1039/D0GC00195C
transformed. Meanwhile, a small amount of 5-methylfurfural created.
and 1,4-benzenediol was generated. The yield of BTO is
During the oxidative coupling reaction, O2 is a reactant for
dependent on the acid strength: acetic acid (38.7%, PKa = 4.74) the oxidation of BTO to obtain a radical intermediate (Figure
> benzoic acid (31.2%, PKa = 4.21) > terephthalic acid (23.9%, 2A). Due to the stabilization of two phenolic groups in the
PKa = 3.54) > monochloroacetic acid (7.6%, PKa = 2.86). Weak ortho/para or ortho/ortho positions, the generation of 5-radical
acidity is beneficial to the synthesis of BTO because the carbon and 3-radical intermediates is preferential. These radicals can
loss is more easily occurred by strong acidity. Exceptionally, be transformed between one another. Subsequently, due to the
formic acid (PKa = 3.77) has a weaker acidity than terephthalic C5 position having a lower steric hindrance, a dimer was formed
acid (PKa = 3.54), but the yield of BTO was lower (20.9% vs via the combination of the C5 position.26 When the reaction was
23.9%).
A considerable amount of 1,4-benzenediol was conducted under a N2 atmosphere, the reaction became
synthesized with a yield of 4.4% due to the reduction of HMF to inactive. The control experiment shows the importance of O2.
5-methylfurfural via the in situ generated H2.25 Meanwhile, Usually, traditional C-C coupling reactions (such as, alkylation,
various solid acids (such as ZrO2, TiO2, Nb2O5, Al2O3 and HZSM- aldol condensation) need acid/base catalysts, which increases
5) were further used in this reaction. The textural properties of the cost. Meanwhile, the yield of bicycloalkane precursors is
solid acids were assessed from N2 adsorption-desorption always unsatisfactory because of the generation of
(Figure S4, Table S1). ZrO2, TiO2 and Nb2O5 only show specific tricycloalkane precursors via excessive coupling reactions. It
surface areas of approximately 4 m2·g-1, whereas Al2O3 and should be mentioned that tricycloalkane is not suitable for
HZSM-5 possess specific surface areas of 150.9, and 305.6 m2·g-1, liquid fuel because of the high freezing point. On the contrary,
respectively. The NH3-TPD shows the acid concentration of TiO2 the oxidative coupling reaction provides a non-catalytic
(0.0038 mmol·g-1), ZrO2 (0.0021 mmol·g-1), Nb2O5 (0.0034 reaction system with high yield and easy separation for
mmol·g-1), Al2O3 (0.0902 mmol·g-1), and HZSM-5 (0.4211 bicycloalkane precursors.
mmol·g-1) (Figure S5, Table S1). Meanwhile, the acidity of the
catalyst was illuminated by the desorbed temperature of NH3.
Obviously, the order of acidity of these metal oxides is HZSM-5
(213, 439 °C) > Al2O3 (140 °C) > Nb2O5 (137 °C) > TiO2 (135 °C) >
ZrO2 (130 °C). To better study the effect of acidity and specific
100
surface area, the same acid amount with different catalyst mass
was used in the reaction. ZrO2, TiO2, Nb2O5 and Al2O3 show high
catalytic activity. HZSM-5 possesses a low catalytic activity with
48.2% of conversion because of their microporous structure
(0.55 nm). The yield of BTO is also decreased with the acidity:
ZrO2 (24.2%) > TiO2 (22.0%) > Nb2O5 (18.9%) > Al2O3 (15.9%) >
HZSM-5 (8.6%). The result further proves that the acidity of the
catalyst has a significant effect on the reaction.
(B)
80
60
40
20
0
Conversion of BTO under air
Selectivity of dimer under air
Conversion of BTO under N2
Selectivity of dimer under N2
Subsequently, the reaction conditions (catalyst amount,
reaction temperature) are optimized. As shown in Figure 1D, as
the acid amount of acetic acid increases from 8.75 mmol to
0
24 72
Reaction time 4(8h)
Figure 2. (A) Proposed reaction pathway for dimer preparation, (B) catalytic
kinetics curve in the oxidative coupling reaction under different gas atmosphere.
43.75 mmol, the yield of BTO and 1,4-benzenediol is increased Reaction conditions: BTO (1 mmol), water (60 mL), 100 °C.
from 38.7% and 0.6% to 51.4% and 3.6%, respectively. When
the reaction temperature decreases to 260 °C, 94.2% of HMF is
Hydrodeoxygenation of dimer
The hydrodeoxygenation of the dimer was conducted over
converted. However, when the reaction temperature increases
to 320 °C, the BTO yield is decreased to 36.2% and 1,4-
benzenediol yield is increased to 18.3%, because hydrogen is
largely generated via the decomposition of in situ generated
formic acid.23 (Figure 1E) Under the optimal conditions, 100% of
HMF is converted with a 51.4% BTO yield via acetic acid catalysis
at 300 °C for 15 min.
Pd/C and HZSM-5 catalysts in a mixture solvent of water and
cyclohexane. The Pd/C and HZSM-5 provide the noble metal and
acid sites for hydrogenation and dehydration reactions,
respectively. The reactant dimer and product bicyclohexane
dissolve preferentially in water and cyclohexane, respectively.
The mixed solvent of water and cyclohexane was used as the
reaction medium to facilitate the approach of the reactant and
hinder the coverage of product to the catalyst surface.27 As
shown by the reaction kinetics (Figure 3A, B), the dimer is
converted to 2-cyclohexylcyclohexenylene via a series of
hydrogenation and dehydration reactions at the beginning, and
then 2-cyclohexylcyclohexanol is formed by C=C hydrogenation.
Finally, bicyclohexane is obtained by C=C hydrogenation of the
dehydrated 1-cyclohexyl-cyclohexene. These intermediates and
products were confirmed by GC-MS (Figure S8). At last, a dimer
Dimerization of BTO
The dimerization of BTO was conducted via a C-C oxidative
coupling in an environmentally friendly aqueous solvent under
an air atmosphere. During the reaction, a dimer is generated
and precipitated, which is very easily separated by filtering
(Figure 2A) The dimer formation was verified by the NMR and
LC-MS (Figures S6, S7). The reaction kinetics are presented in
Figure 2B. After 72 h, the conversion of BTO was 94.4%, the
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 7
Green Chemistry
Please do not adjust margins
Journal Name
ARTICLE
1
2
(a) L. Wang, J.-J. Zou, X. Zhang and L. Wang, Fuel, 2012, 91,
164-169; (b) Q. Deng, X. Zhang, L. WaDnOgI:a1n0d.10J.3-V9Ji./eDwZ0oAGurtCi,c0lCe0hO1en9lm5inCe.
Eng. Sci., 2015, 135, 540-546; (c) H. A. Meylemans, R. L.
Quintana, B. R. Goldsmith and B. G. Harvey, ChemSusChem,
2011, 4, 465-469; (d) H. A. Meylemans, L. C. Baldwin and B. G.
Harvey, Energy Fuels, 2013, 27, 883-888.
(a) B. Zhang, J. Li, L. Guo, Z. Chen and C. Li, Appl. Catal. B
Environ., 2018, 237, 660-664; (b) Y. Zhang, V. Degirmenci, C. Li
and E. J. M. Hensen, ChemSusChem, 2011, 4, 59-64; (c) C.
Sener, A. H. Motagamwala, D. M. Alonso and J. A. Dumesic,
ChemSusChem, 2018, 11, 2321-2331; (d) R. Galaverna, M. C.
Breitkreitz and J. C. Pastre, ACS Sustain. Chem. Eng., 2018, 6,
4220-4230.
(a) T. Prasomsri, T. Nimmanwudipong and Y. Román-Leshkov,
Energy Environ. Sci., 2013, 6, 1732-1738; (b) P. Anbarasan, Z.
C. Baer, S. Sreekumar, E. Gross, J. B. Binder, H. W. Blanch, D.
S. Clark and F. D. Toste, Nature, 2012, 491, 235-239; (c) B. G.
Harvey and R. L. Quintana, Energy Environ. Sci., 2010, 3, 352-
357; (d) J. Q. Bond, D. M. Alonso, D. Wang, R. M. West and J.
A. Dumesic, Science, 2010, 327, 1110-1114; (e) P.
Sudarsanam, R. Zhong, S. Van den Bosch, S. M. Coman, V. I.
Parvulescu and B. F. Sels, Chem. Soc. Rev., 2018, 47, 8349-
8402.
(a) G. W. Huber, J. N. Chheda, C. J. Barrett and J. A. Dumesic,
Science, 2005, 308, 1446-1450; (b) S. Rojas-Buzo, P. García-
García and A. Corma, Green Chem., 2018, 20, 3081-3091.
(a) A. Corma, O. Torre, M. Renz and N. Villandier, 2011, 50,
2375-2378; (b) L. J. Konwar, A. Samikannu, P. Mäki-Arvela and
J.-P. Mikkola, Catal. Sci. Technol., 2018, 8, 2449-2459; (c) G. Li,
N. Li, S. Li, A. Wang, Y. Cong, X. Wang and T. Zhang, Chem.
Commun., 2013, 49, 5727-5729.
conversion of 96.7%, bicyclohexane selectivity of 90.4%, and a
bicyclohexane yield of 87.4% were obtained after 10 h. The
bicyclohexane, with a high density of 0.886 g·mL-1, is desirable
and has potential applications for direct use or by mixing with
other fuels.10b
3
100
(B)
80
60
Dimer
2-cyclohexylcyclohexenylene
2-cyclohexylcyclohexanol
1-cyclohexyl-cyclohexene
bicyclohexane
40
20
0
4
5
0
2
4
6
8
10
Reaction time (h)
Figure 3. (A) Proposed reaction pathway for bicyclohexane preparation, (B)
catalytic kinetics curve in the hydrodeoxygenation reaction. Reaction conditions:
dimer (1.2 mmol), HZSM-5 (1.00 g), Pd/C (0.080 g), water (15 mL), cyclohexane (15
mL), 240 °C, 8.0 MPa of H2 pressure.
6
(a) O. Kikhtyanin, D. Kadlec, R. Velvarská and D. Kubička,
ChemCatChem, 2018, 10, 1464-1475; (b) Q. Deng, J. Xu, P.
Han, L. Pan, L. Wang, X. Zhang and J.-J. Zou, Fuel Process.
Technol., 2016, 148, 361-366.
7
8
J. Xie, L. Zhang, X. Zhang, P. Han, J. Xie, L. Pan, D.-R. Zou, S.-H.
Liu and J.-J. Zou, Sustainable Energy Fuels, 2018, 2, 1863-1869.
(a) G. Li, N. Li, X. Wang, X. Sheng, S. Li, A. Wang, Y. Cong, X.
Wang and T. Zhang, Energy Fuels, 2014, 28, 5112-5118; (b) Q.
Deng, P. Han, J. Xu, J.-J. Zou, L. Wang and X. Zhang, Chem. Eng.
Sci., 2015, 138, 239-243; (c) X. Zhang, Q. Deng, P. Han, J. Xu, L.
Pan, L. Wang and J.-J. Zou, AIChE J., 2017, 63, 680-688; (d) Y.
Zhong, Q. Deng, P. Zhang, J. Wang, R. Wang, Z. Zeng and S.
Deng, Fuel, 2019, 240, 270-277; H. Li, Q. Deng, H. Chen, X. Cao,
J. Zheng, Y. Zhong, P. Zhang, J. Wang, Z. Zeng, S. Deng, Appl.
Catal. A: Gen., 2019, 580, 178-185.
Conclusions
In summary, this work provides a synthesis route for a C-C
six-membered ring BTO from cellulose-derived HMF. The
cellulose-derived synthesis route for C-C ring compounds is
more efficient than the lignin- and hemicelluloses-derived
routes. Moreover, a green and efficient route for high-density
fuel is reported for the first time via a C-C oxidative coupling
reaction combined with subsequent hydrodeoxygenation
reaction. As a result, final bicyclohexane is obtained with an
overall yield of 42.4 %. Thus, this work offers a promising route
for producing C-C ring fine compounds and high-density fuel
using HMF as a reactant.
9
P. Han, G. Nie, J. Xie, X.-T.-F. E, L. Pan, X. Zhang and J.-J. Zou,
Fuel Process. Technol., 2017, 163, 45-50.
10 (a) J. Yang, N. Li, G. Li, W. Wang, A. Wang, X. Wang, Y. Cong
and T. Zhang, Chem. Commun., 2014, 50, 2572-2574; (b) Q.
Deng, G. Nie, L. Pan, J.-J. Zou, X. Zhang and L. Wang, Green
Chem., 2015, 17, 4473-4481; (c) W. Wang, N. Li, G. Li, S. Li, W.
Wang, A. Wang, Y. Cong, X. Wang and T. Zhang, ACS
Sustainable Chem. Eng., 2017, 5, 1812-1817.
11 (a) G. Nie, X. Zhang, P. Han, J. Xie, L. Pan, L. Wang and J.-J. Zou,
Chem. Eng. Sci., 2017, 158, 64-69; (b) G. Nie, X. Zhang, L. Pan,
P. Han, J. Xie, Z. Li, J. Xie and J.-J. Zou, Chem. Eng. Sci., 2017,
173, 91-97; (c) Y. Zhong, P. Zhang, X. Zhu, H. Li, Q. Deng, J.
Wang, Z. Zeng, J.-J. Zou and S. Deng, ACS Sustainable Chem.
Eng., 2019, 7, 14973-14981.
12 F. Chen, N. Li, X. Yang, L. Li, G. Li, S. Li, W. Wang, Y. Hu, A.
Wang, Y. Cong, X. Wang and T. Zhang, ACS Sustainable Chem.
Eng., 2016, 411, 6160-6166
13 J. Xie, X. Zhang, L. Pan, G. Nie, X.-T.-F. E, Q. Liu, P. Wang, Y. Li
and J.-J. Zou, Chem. Commun., 2017, 53, 10303-10305.
14 J. Xie, L. Pan, G. Nie, J. Xie, Y. Liu, C. Ma, X. Zhang and J.-J. Zou,
Green Chem., 2019, 21, 5886-5895.
Conflicts of interest
The authors declare no conflict of interests.
Acknowledgements
The authors appreciate the supports from the National Natural
Science Foundation of China (21878138, 21666021, 21706112),
Postdoctoral Science Foundation of China (2017KY21,
2018T110660) and the new faculty start-up funds from both
Nanchang University and Arizona State University.
Notes and references
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 6 of 7
ARTICLE
Journal Name
15 (a) R. Chaudhary and P. L. Dhepe, Green Chem., 2017, 19, 778-
788; (b) G.-H. Wang, Z. Cao, D. Gu, N. Pfänder, A.-C. Swertz, B.
Spliethoff, H.-J. Bongard, C. Weidenthaler, W. Schmidt, R.
Rinaldi, and F. Schüth, Angew. Chem. Int. Ed., 2016, 55, 8850-
8855; (c) A. K. Deepa and P. L. Dhepe, ACS Catal., 2015, 5, 365-
379.
View Article Online
DOI: 10.1039/D0GC00195C
16 (a) Q. Meng, M. Hou, H. Liu, J. Song and B. Han, Nature
Commun., 2017, 8, 14190; (b) H. Liu, T. Jiang, B. Han, S. Liang
and Y. Zhou, Science, 2009, 326, 1250-1252.
17 (a) G.-S. Zhang, M.-M. Zhu, Q. Zhang, Y.-M. Liu, H.-Y. He and
Y. Cao, Green Chem., 2016, 18, 2155-2164; (b) R. Fang, H. Liu,
R. Luque and Y. Li, Green Chem., 2015, 17, 4183-4188; (c) N.
Pino, G. Hincapié and D. López, Energy Fuels, 2018, 32, 561-
573; (c) X. Li, Q. Deng, S. Zhou, J. Zou, J.Wang, R. Wang, Z. Zeng
and S. Deng, J. Catal., 2019, 378, 201-208.
18 (a) E. Hayashi, Y. Yamaguchi, K. Kamata, N. Tsunoda, Y.
Kumagai, F. Oba and M. Hara, J. Am. Chem. Soc., 2019, 141,
890-900; (b) J. Tan, J. Cui, Y. Zhu, X. Cui, Y. Shi, W. Yan and Y.
Zhao, ACS Sustainable Chem. Eng., 2019, 7, 10670-10678; (c)
A. J. Kumalaputri, G. Bottari, P. M. Erne, H. J. Heeres and K.
Barta, ChemSusChem, 2014, 7, 2266; (d) J. Artz, S. Mallmann,
and R. Palkovits, ChemsusChem, 2015, 8, 672-679; (e) B. Xiao,
M. Zheng, X. Li, J. Pang, R. Sun, H. Wang, X. Pang, A. Wang, X.
Wang and T. Zhang, Green Chem., 2016, 18, 2175-2184.
19 (a) S. Zhang, H. Ma, Y. Sun, Y. Luo, X. Liu, M. Zhang, J. Gao and
J. Xu, Green Chem., 2019, 21, 1702-1709; (b) R. Ramos, A.
Grigoropoulos, N. Perret, M. Zanella, A. P. Katsoulidis, T. D.
Manning, J. B. Claridge and M. J. Rosseinsky, Green Chem.,
2017, 19, 1701-1713; (c) J. Ohyama, R. Kanao, A. Esakia and A.
Satsuma, Chem. Commun., 2014, 50, 5633-5636; (d) J.
Ohyama, R. Kanao, Y. Ohira and A. Satsuma, Green Chem.,
2016, 18, 676-680.
20 (a) G. C. A. Luijkx, F. van Rantwijk and H. van Bekkum, Recl.
Trav. Pay-Bas, 1991, 110, 343-344; (b) G. C. A. Luijkx, F. van
Rantwijk and H. van Bekkum, Carbohydr. Res., 1993, 242, 131-
139.
21 (a) G. C. A. Luijkx, W. der Horst, S. O. A. Koskinen, F. Rantwijk
and H. van Bekkum, J. Anal. Appl. Pyrol., 1994, 28, 245-254;
(b) Z. Srokol, A. G. Bouche, A. van Estrik, R. C. J. Strik, T.
Maschmeyer, J. A. Peters, Carbohydr. Res., 2004, 339, 1717-
1726; (c) T. M. Aida, Y. Sato, M. Watanabe, K. Tajima, T
Nonaka, H. H. Hattori and K. Arai, J. Supercrit. Fluids, 2007, 40,
381-388; (d) A. Chuntanapum, T. L. K. Yong, S. Miyake and Y.
Matsumura, Ind. Eng. Chem. Res., 2008, 47, 2956-2962.
22 A. J. Kumalaputri, C. Randolph, E. Otten, H. J. Heeres and P. J.
Deuss, ACS Sustainable Chem. Eng., 2018, 6, 3419-3425.
23 A. Chuntanapum and Y. Matsumura, Ind. Eng. Chem. Res.,
2009, 48, 9837-9846.
24 G. Chen, J. Tao, C. Liu, B. Yan, W. Li and X. Li, Renew.
Sustainable Energy Rev., 2017, 79, 1091-1098.
25 A. B. Ross, P. Biller, M. L. Kubacki, H. Li, A. Lea-Langton and J.
M. Jones, Fuel, 2010, 89, 2234-2243.
26 C. Randolph, C. W. Lahive, S. Sami, R. W. A. Havenith, H. J.
Heeres and P. J. Deuss, Org. Process Res. Dev., 2018, 22, 1663-
1671.
27 M. I. Alam, T. S. Khan, M. A. Haider, ACS Sustainable Chem.
Eng., 2019, 7, 2894-2898.
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 7
Green Chemistry
View Article Online
DOI: 10.1039/D0GC00195C
Table of Contents Entry
1