Highly selective hydrothermal production of cyclohexanol from biomass-derived cyclohexanone over Cu powder

Article abstract of DOI:10.1016/j.cattod.2015.11.016

An efficient conversion of biomass-derived cyclohexanone to cyclohexanol by in situ-formed hydrogen over Cu catalyst under hydrothermal conditions was reported at first. Among the catalysts tested, Cu exhibited high catalytic activity for the conversion of cyclohexanone, and the highest yield of 100% was obtained when Zn acted as reductant. The experiment was carried out by using gaseous hydrogen as the external hydrogen source indicated that the yield of 75.1% was lower than in situ-formed hydrogen by oxidation of Zn in water. The present study provides an efficient route by environmentally benign, commercially available Cu powder as a catalyst for cyclohexanone conversion to cyclohexanol.

Full text of DOI:10.1016/j.cattod.2015.11.016

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Highly selective hydrothermal production of cyclohexanol from
biomass-derived cyclohexanone over Cu powder
Zhiyuan Songa, Dezhang Rena,∗, Tian Wanga, Fangming Jina, Qianhui Jianga,
Zhibao Huoa,b,∗
a School of Environmental Science and Engineering, the State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University,
800 Dongchuan Road, Shanghai 200240, China
b State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, China
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient conversion of biomass-derived cyclohexanone to cyclohexanol by in situ-formed hydrogen
over Cu catalyst under hydrothermal conditions was reported at first. Among the catalysts tested, Cu
exhibited high catalytic activity for the conversion of cyclohexanone, and the highest yield of 100% was
obtained when Zn acted as reductant. The experiment was carried out by using gaseous hydrogen as
the external hydrogen source indicated that the yield of 75.1% was lower than in situ-formed hydrogen
by oxidation of Zn in water. The present study provides an efficient route by environmentally benign,
commercially available Cu powder as a catalyst for cyclohexanone conversion to cyclohexanol.
© 2015 Elsevier B.V. All rights reserved.
Received 25 September 2015
Received in revised form
17 November 2015
Accepted 24 November 2015
Available online xxx
Keywords:
Biomass derivatives
Cyclohexanone
Cyclohexanol
Cu powder
Hydrothermal reaction
1. Introduction
[4–7]. Therefore, the conversion of biomass-derived cyclohexanone
to produce cyclohexanol will be more meaningful.
Cyclohexanol has been considered as very important inter-
mediate and is widely used in the synthesis of hexane diacid
and hexanolactam. Moreover, cyclohexanol could also be used in
pharmaceuticals, plasticisers, surfactant, paint, industry solvent
and so on. Due to its importance, much attention has been paid
to developing efficient methods for the production of cyclohexanol
in recent years. Among these processes, catalytic hydrogenation
of cyclohexanone to cyclohexanol is an attractive route since the
reaction proceeds under mild conditions.
We all know that the hydrogenation of ketones to alcohols is
an important reaction in organic chemistry [1,2]. Cyclohexanone is
a significant by-product in the degradation process of lignocellu-
lose. Lignocellulose is an important biomass which makes up a high
proportion of biomass [3]. Besides, biomass and biomass-derived
compounds as a promising renewable resource instead of fossil fuel
is attracting more and more attention because they can provides
not only clean energy but also raw material for chemical industry
Currently, catalytic hydrogenation of cyclohexanone to cyclo-
hexanol attracts more and more attention due to its promising
use in the field of green chemistry [8–10]. Bhar et al. reported
the hydrogenation of ketones to the corresponding alcohols by
aluminum powder (5 eq.) in the presence of sodium hydroxide
in MeOH:H2O = 2:1, the yield of cyclohexanol was only 19% [8].
Campbell et al. used Meerwein-Pondorf-Verley reduction by alu-
minum complexes in toluene at room temperature, after 2 h, the
yield of cyclohexanol reached 96% [9]. Fujihara et al. used copper
complexes as catalyst and Ph2SiH2 as hydrogen source in toluene at
room temperature, the catalytic activity was good. However, they
used complicated and toxic complexes, and the hydrogen source
was expensive [10]. Other noble metal, such as Ir, [11] Rh, [12] Ru,
[13] can also showed high catalytic activity in the conversion of
cyclohexanone and obtained good results. However, these previous
works still have some obvious defects, such as expensive prepared
noble metal catalysts, [11–13] organic solvents [8–10] [12,13] and
longer reaction times (6–12 h).[11] Therefore, one of the great
challenges is to develop a useful conversion process of cyclohex-
anone in the presence of high-efficiency commercial catalysts. As a
solvent, water has some merits that other organic solvent doesn’t
have, such as cheap, non-toxic, non-flammable, non-explosive
∗
Corresponding authors.
E-mail address: hzb410@sjtu.edu.cn (Z. Huo).
http://dx.doi.org/10.1016/j.cattod.2015.11.016
0920-5861/© 2015 Elsevier B.V. All rights reserved.
Please cite this article in press as: Z. Song, et al., Highly selective hydrothermal production of cyclohexanol from biomass-derived
cyclohexanone over Cu powder, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.11.016

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Z. Song et al. / Catalysis Today xxx (2015) xxx–xxx
and environmental friendly [14]. If water could be widely used
as a solvent for organic reaction, it would bring about enormous
achievement in environmental, economic and safety aspects [15].
In previous works, we and other groups had developed many
methods to convert biomass and biomass-derived compounds
to value-added chemicals in high-temperature water [16–18].
For example, we developed an efficient process for the selective
conversion of glucose to lactic acid under alkaline hydrothermal
conditions with the highest yield of 25% [19]. Recently, we reported
a method for the formation of ethylene glycol from glycolide over
CuO in water, and high yield of 94% was achieved [16]. Also we also
developed catalytic conversion of ethyl lactate to 1,2-propanediol
in the presence of CuO with the yield of 93% [20].
system, 5975 C inert MSD with Triple-Axis Detector) equipped
with an HP Innowax polyethylene glycol capillary column (30
m × 250 ␮m × 0.5 ␮m). The solid samples were analysed with X-
ray diffraction (Shimadzu, Lab-XRD-6100). The total organic carbon
concentration was confirmed by a TOC Analyzer (Shimadzu TOC-V).
The yield of cyclohexanol was calculated on the basis of the
following equation:
The mole of cyclohexanol obtained
The yield(%) =
The mole of cyclohexanone
3. Results and discussion
Based on the studies above, we herein present a highly
efficient hydrothermal conversion of biomass-derived cyclohex-
anone to cyclohexanol with high yield and high selectivity using
in situ-formed hydrogen in water in the presence of Cu catalyst.
A mechanism of cyclohexanone conversion was also proposed
(Eq. 1).
3.1. Catalyst screening
Initially, a series of experiments were carried out to investi-
gate the feasibility of converting cyclohexanone to cyclohexanol
in the presence of 5 mmol metal or metal oxides and 25 mmol
Zn with 25% water filling (7.5 mL H2O) at 250 ◦C for 150 min. The
results are summarized in Table 1. The conversion of cyclohex-
anone was higher and cyclohexanol yield of 92.2% was achieved
in the presence of both Cu and Zn (entry 1). It is obvious that
the unique peak of desired cyclohexanol and 100.1 of its mass-to-
charge ratio (m/z) can be observed by GC-MS spectrum as shown
in Fig. 1(a). From Fig. 1(b), the peak of cyclohexanone is getting
smaller and smaller until disappearing completely while the peak of
cyclohexanol becomes bigger gradually as the time increased from
0 to 150 min, indicating that cyclohexanone was converted com-
pletely. Various Cu complexes, such as CuO, Cu2O, Cu2(OH)PO4 and
CuFe2O4, were investigated and gave desired products in moder-
ate to high yields, but the yields were not superior to that obtained
with Cu catalyst (entries 2–5). Co, Sn, Ni and NiO were also effective
for the conversion of cyclohexanone to afford good yields (entries
6–9). However, other metals or metal oxides, such as Fe, Fe2O3,
2. Experimental
2.1. Experimental materials
Cyclohexanone (≥ 99.5%) as the initial reactants was purchased
from J&K Scientific Ltd. Cyclohexanol (≥ 98.5%) was used for quan-
titative analysis. Zn (200 mesh, Sinopharm Chemical Reagent Co.,
Ltd) was used as the reductant. Fe, Fe2O3, Fe3O4, Cu, CuO, Cu2O, Ni,
NiO, Co, SiO2, ZrO2, Al2O3, TiO2, Pd/C, active carbon (AR, 200mesh,
Sinopharm Chemical Reagent Co., Ltd) and Mn (AR, 200 mesh,
Aladdin) and Sn (AR, 200 mesh, Sigma–Aldrich) were also used in
the experiments. And two catalysts, Cu(OH)PO4 and CuFe2O4,were
prepared by ourselves according to the recent publication [21].
Table 1
Catalyst screening on the yield of cyclohexanol.a
2.2. Experimental procedure
All the experiments were performed in a Teflon-lined steel
batch reactor whose internal volume is 30 mL. Cyclohexanone
(0.193 mmol, 20 ␮L) was used for all experiments in this study.
The procedure for the synthesis of cyclohexanol was as follows.
First of all, desired cyclohexanone, deionized water, reactant and
catalyst were loaded into reactor. Then, after filling in with nitro-
gen to remove air, the reactor was putted into a drying oven. After
a certain period of time, we took out the reactor from drying oven
immediately. Due to the oven setting, it would take 20 minutes to be
preheated to the desired temperature, so we prolonged 20 minutes
to reaction times. The reactor was cooled by an air fan. Finally, liquid
sample was collected and filtered by 0.45 ␮m Syringe Filter. Solid
sample was collected and washed by deionized water for several
times and dried in drying oven at 60 ◦C for 24 h. The samples would
be analysed later. The schematic diagram of reactor and drying oven
was shown in Fig. SI-1.
.
Entry
Reductant
Catalyst
Cyclohexanol (%)
1
2
3
4
5
6
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
–
Cu
Cu2O
CuO
Cu2(OH)PO4
CuFe2O4
Co
Sn
Ni
NiO
Fe
Fe2O3
Fe3O4
SiO2
ZrO2
Al2O3
TiO2
Pd/C
Mn
active carbon
–
92.2
71.2
70.5
47.4
57.6
86.7
64.0
70.8
75.4
18.2
15.4
5.3
7
8b
9
10
11
12
13
14
15
16
17
18
19
20
21
22
8.7
14.4
17.8
11.1
5.0
16.2
9.7
11.5
0
0
2.3. Product analysis
After the reaction, liquid samples were confirmed with GC-
MS (Agilent 7890A GC system, 5975 C inert MSD with Triple-Axis
Detector) equipped with an HP Innowax polyethylene glycol
capillary column (30 m × 250 ␮m × 0.5 ␮m). The qualification of
cyclohexanol was confirmed with GC-FID (Agilent 7890A GC
Cu
–
–
a
Reaction conditions: [cyclohexanone (0.193 mmol, 20 ␮L), 25 mmol Zn, 5 mmol
catalyst, 25% water filling (7.5 mL H2O), 250 ◦C, 150 min].
b
Byproduct phenol of 17.0% was obtained with the conversion of 87.8%.
Please cite this article in press as: Z. Song, et al., Highly selective hydrothermal production of cyclohexanol from biomass-derived
cyclohexanone over Cu powder, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.11.016

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Fig. 1. (a) GC-MS spectrum of the liquid samples. (b) GC-FID of liquid samples at different reaction time.
Pd/C, Mn, active carbon and so on, proved to be completely ineffec-
tive and lower yields were obtained (entries 10–19). The reaction
of cyclohexanone afforded only 11.5% yield or no desired cyclohex-
anol was observed at all in the absence of either Cu or Zn or both,
indicating that the importance of combination of Cu and Zn (entries
20–22).
As illustrated in Fig. 2, the composition of the solid samples after
the reaction was determined by XRD patterns to investigate the role
of metals. Zn was found to be oxidized to ZnO while Cu or Co, Sn,
Ni, Fe kept unchanged and still existed in the solid samples. This
suggested that in this process Zn acted as a reductant while Cu or
Co, Sn, Ni, Fe acted as catalysts. Mn was oxidized to Mn3O4 after
reaction and the XRD patterns was shown in Fig. SI-3.
Next, the reactions were conducted to investigate the effect of
the amount of Cu catalyst on the yield of cyclohexanol. In Fig. 4, the
result indicated the yield of cyclohexanol increased significantly
with the amount of Cu increased from 0 to 8 mmol, and the maxi-
mum value of 96.4% was obtained at 7.5 mmol. When the amount
of Cu powder was more than 7.5 mmol, the yield of cyclohexanol
decreased gradually as the amount of Cu increased. From the result
we can reasonably infer that excess Cu can cause the reversible
conversion of formed cyclohexanol to cyclohexanone leading to the
decreasing yield. Thus, 7.5 mmol Cu catalyst was the most suitable
for the conversion of cyclohexanone.
100
80
60
40
20
0
Zn
Mg
Al
Ni
Fe
None
Reductant
Fig. 3. Effect of reductants [cyclohexanone (0.193 mmol, 20 ␮L), 25 mmol reductant,
7.5 mmol Cu, 25% water filling (7.5 mL H2O), 250 ◦C, 150 min].
in Fig. SI-2, we can see that there has a big change in shape of Cu
powder after the reaction, it becomes rough and irregular.
We then examined the reaction to confirm whether or not
Cu catalyst can cause the reversible conversion of the formed
cyclohexanol. The formed cyclohexanol as starting material was
reacted for 150 min in the presence of 7.5 mmol Cu and 20 mmol
ZnO obtained after the reaction at 250 ◦C, and the 18.6% yield of
cyclohexanone was obtained and the 39.7% yield of cyclohexanol
was recovered. This result clearly indicated that this reaction was
reversible over Cu catalyst (Eq. 2). As illustrated in Fig. SI-4, gaseous
phase CO and H2 were observed by GC-MS and TCD
The Cu catalyst was collected to observe the change before and
after the reaction. After the reaction, Zn was removed by using HCl.
The Cu powder was filtered, collected and washed by deionized
water, then dried using an oven at 60 ◦C for 24 h. As was shown
Cu
ο Ni Δ Sn
♦ ΖnO
Fe
∇ Co
♦
♦
♦
♦
♦
♦
♦
♦
♦
Fe
Sn
Ni
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
Δ
Δ
Δ
Δ
Δ
ΔΔ
♦
♦
♦
♦
♦
°
♦
♦
♦
♦
♦
♦
°
°
3.2. Optimization of active metals
♦
♦
Co
Cu
∇
∇
∇
♦
After that, we further studied the effect of various active metals
as reductants on the yield of cyclohexanol when other reaction con-
ditions unchanged [cyclohexanone (0.193 mmol, 20 ␮L), 25 mmol
reductant, 7.5 mmol Cu, 25% water filling (7.5 mL H2O), 250 ◦C,
150 min]. The details are showed in Table SI-1 and Fig. 3. When
active Mg, Al, Ni, Fe were chosen to be reductants, it can be seen
clearly that the efficiency of transformation was as follows, Zn > Mg
♦
♦
♦
♦
♦
10
20
30
40
50
60
70
80
Degree (2θ)
Fig. 2. XRD patterns of the solid samples.
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Temperature (oC)
The amount of Zn (mmol)
0
5
10
15
20
25
30
35
40
80
100
120
140
160
180
200
220
240
260
110
100
90
100%
100
80
60
40
20
0
100%
100%
80
70
60
50
40
0
2
4
6
8
10
12
14
The amount of Cu (mmol)
30
80
100
120
140
160
180
200
220
240
260
Fig. 4. (a) Effect of Cu amount [cyclohexanone(0.193 mmol, 20 ␮L), 25 mmol Zn, 25%
water filling (7.5 mL H2O), 250 ◦C, 150 min]; (b) Effect of Zn amount [cyclohexanone
(0.193 mmol, 20 ␮L), 7.5 mmol Cu, 25% water filling (7.5 mL H2O), 250 ◦C, 150 min].
Reaction time (min)
Fig. 6. (a) Effect of time [cyclohexanone (0.193 mmol 20 ␮L), 20 mmol Zn, 7.5 mmol
Cu, 25% water filling (7.5 mL), 250 ◦C]; (b) Effect of temperature [cyclohexanone
(0.193 mmol 20 ␮L), 20 mmol Zn, 7.5 mmol Cu, 25% water filling (7.5 mL H2O),
150 min].
>Al> Ni > Fe, and the yields were 96.4%, 50.9%, 50.8%, 13.8% and
8.4%, respectively. Obviously, Zn was the most suitable reductant
to be used in the process. Then, the amount of Zn was optimized
as shown in Fig. 4, the yield of product significant increased with
increasing amount of Zn. When the amount of Zn was 20 mmol,
cyclohexanone was completely converted and the highest yield
reached 100%. The decreasing yield might be due to the reversible
conversion of obtained cyclohexanol by more hydrogen by the oxi-
dation of excess Zn in water or by the effect of Cu catalyst and ZnO
as mentioned above.
continuously increasing from 15% to 25%. The optimum water
filling was 25% (about 3.87 MPa) to obtain the maximum value of
100%, and then decreased after 25%. This can be speculated that the
incremental water pressure is better for promoting the reversible
conversion of obtained cyclohexanol when water filling increases,
which leads to low yield.
As a general rule, temperature plays an important role in chemi-
cal reaction. In the process the increase of the reaction temperature
from 100 ◦C to 250 ◦C gave higher conversion of cyclohexanone.
Fig. 6 showed that the yield of cyclohexanol increased drastically
from 100 ◦C to 195 ◦C. After 195 ◦C, the yield increased gradually. At
250 ◦C, cyclohexanone was completely converted and a maximum
value of 100% was reached, it clearly indicated that higher reaction
temperature are more favourable to the production of cyclohexanol
from cyclohexanone. However, it is worth noting that because the
maximum safety temperature of the Teflon material of reactor was
250 ◦C, higher than 250 ◦C was not optimized.
3.3. Effects of the various parameters
Water filling is also a very influential factor for the conversion
of cyclohexanone. As shown in Fig. 5, water filling from 15% to 45%
has a significant effect for the production of cyclohexanol from
cyclohexanone. Considering the security reasons of the Teflon
material, water filling must be less than 45% because excessive
pressure would cause potential accident during the reaction. Fig. 5
showed that the yield increased significantly with water filling
Having optimized 250 ◦C as the best reaction temperature for
the production of cyclohexanol, further experiments were carried
out to investigate the effect of reaction time from 100 to 250 min
on the yield of cyclohexanol. In Fig. 6, it can be seen that the yield of
cyclohexanol improved drastically as the reaction time increased
from 100 min to 150 min and the yield of 100% was obtained
at 150 min. When the time had increased more than 150 min, a
decrease in the conversion of cyclohexanone as well as a decreasing
yield of cyclohexanol was observed. Evidential experiment had
found that obtained cyclohexanol as starting material could be con-
verted reversibly in the presence of Cu and ZnO obtained by the
oxidation of Zn at 250 ◦C for 150 min as mentioned above. The result
indicated that the longer reaction time was unfavourable for the
production of cyclohexanol.
100
100%
95
90
85
80
75
70
65
Finally, we carried out the experiments to investigate carbon
balance by TOC and TCD, and found that 100% cyclohexanone was
converted into cyclohexanol under the optimal reaction conditions.
Only gaseous H2 was detected according to the result of TCD.
15
20
25
30
35
40
45
3.4. Cyclohexanone hydrogenation by added hydrogen
The water filling (%)
To investigate the conversion of cyclohexanone using added
gaseous hydrogen as a hydrogen source in the presence of 7.5 mmol
Fig. 5. Effect of water filling [cyclohexanone (0.193 mmol, 20 ␮L), 20 mmol Zn,
7.5 mmol Cu, 250 ◦C, 150 min].
Please cite this article in press as: Z. Song, et al., Highly selective hydrothermal production of cyclohexanol from biomass-derived
cyclohexanone over Cu powder, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.11.016

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Appendix A. Supplementary data
OH
O
H2 + ZnO
O
H
H
Cat. Cu
Supplementary material related to this article can be found,
in the online version, at http://dx.doi.org/10.1016/j.cattod.2015.11.
016.
Cu/ZnO
Zn + H2O
In situ H2 generated
References
Scheme 1. Proposed mechanism for the formation of cyclohexanol.
[1] N. Gorgas, B. Stöger, L.F. Veiros, E. Pittenauer, G. Allmaier, K. Kirchner, Efficient
hydrogenation of ketones and aldehydes catalyzed by well-defined iron (II)
PNP pincer complexes: evidence for an insertion mechanism,
Organometallics 33 (2014) 6905–6914.
[2] T. Mahdi, D.W. Stephan, Enabling catalytic ketone hydrogenation by
frustrated lewis pairs, J. Am. Chem. Soc. 136 (2014) 15809–15812.
[3] Y.X. An, N. Li, M.H. Zong, W.Y. Lou, Easily measured pH as an indicator of the
effectiveness of the aqueous cholinium ionic liquid-based pretreatment of
lignocellulose, RSC Adv. 4 (2014) 55635–55639.
Cu powder with 3 MPa H2 at 250 ◦C for 150 min, the reac-
tion also proceeded well (Procedure in details, see Supporting
Information). As expected, the yield of 75.1% was obtained
although it is much lower than that of in situ-formed hydrogen
(Eq. 3).
[4] S. Raju, M.-E. Moret, J.M.K. Gebbink, Rhenium-catalyzed dehydration and
deoxydehydration of alcohols and polyos: opportunities for the formation of
olefins from biomass, ACS Catal. 5 (2015) 281–300.
[5] Y.-T. Cheng, G.W. Huber, Chemistry of furan conversion into aromatics and
olefins over HZSM-5: a model biomass conversion reaction, ACS Catal. 1
(2001) 611–628.
[6] N.R. Singh, W.N. Delgass, F.H. Ribeiro, R. Agrawal, Estimation of liquid fuel
yields from biomass, Environ. Sci. Technol. 44 (2010) 5298–5305.
[7] R.J.M. Westerhof, D.W.F. Brilman, M. Garcia-Perez, Z.H. Wang, S.R.G.
Oudenhoven, W.P.M. van Swaaij, S.R.A. Kersten, Fractional condensation of
biomass pyrolysis vapors, Energy Fuels 25 (2011) 1817–1829.
[8] Sanjay Bhar, Sharmistha Guha, The remarkable role of water during the
chemoselective reduction of ketones mediated by metallic aluminium,
Tetrahedron 45 (2004) 3775–3777.
[9] E. Joseph Campbell, Hongying Zhou, SonBinh T. Nguyen, Catalytic
Meerwein-Pondorf-Verley reduction by simple aluminum complexes, Org.
Lett. 3 (2001) 2391–2393.
[10] T. Fujihara, K. Semba, J. Terao, Y. Tsuj, Copper-catalyzed hydrosilylation with a
bowl-shaped phosphane ligand: preferential reduction of a bulky ketone in
the presence of an aldehyde, Angew. Chem. Int. 49 (2010)
1472–1476.
[11] Yawen Wei, Dong Xue, Qian Lei, Chao Wang, Jianliang Xiao, Cyclometalated
iridium complexes for transfer hydrogenation of carbonyl groups in water,
Green Chem. 15 (2013) 629–634.
[12] O. Niyomura, T. Iwasawa, N. Sawada, M. Tokunaga, Y. Obora, Y. Tsuji, A
bowl-shaped phosphine as a ligand in rhodium-catalyzed hydrosilylation:
rate enhancement by a mono(phosphine) rhodium species, Organometallic
24 (2005), 3486-3475.
3.5. Plausible mechanism
Based on the experimental results above, a plausible reaction
mechanism for the conversion of cyclohexanone to cyclohexanol
over Cu powder was proposed in Scheme 1. First, hydrogen in situ-
formed by the oxidation of Zn in water was adsorbed on the surface
of Cu powder. At the same time, cyclohexanone was also absorbed
on the surface of Cu/ZnO with carbonylic C and O atoms. After that,
the high chemical activity hydrogen atom attacked cyclohexanone
molecules, hydrogen atom was added to carbonylic C atom. Then,
another hydrogen atom from the surface of Cu/ZnO was attached
to O atom, which leaded to the formation of hydroxyl. Finally, the
desired cyclohexanol was obtained.
[13] D. Spasyuk, S. Smith, D.G. Gusev, Replacing phosphorous with sulfur for the
efficient hydrogenation of esters, Angew. Chem. Int. 52 (2013)
2538–2542.
[14] W.J.W. Watson, How do the fine chemical, pharmaceutical, and related
industries approach green chemistry and sustainability? Green Chem. 14
(2012) 251–259.
[15] Y. Wei, D. Xue, Q. Lei, C. Wang, J.L. Xiao, Cyclometalated iridium complexes for
transfer hydrogenation of carbonyl groups in water, Green Chem. 15 (2013)
629–634.
[16] L.L. Xu, Z.B. Huo, J. Fu, F.M. Jin, Highly efficient conversion of biomass-derived
glycolide to ethylene glycol over CuO in water, Chem. Commun. 50 (2014)
6009–6012.
[17] Z.B. Huo, J.K. Liu, G.D. Yao, X. Zeng, J. Luo, F.M. Jin, Efficient hydrothermal
conversion of cellulose into methane over porous Ni catalyst, Appl. Catal. A
490 (2015) 36–41.
[18] N. Sudasinghe, J.R. Cort, R. Hallen, M. Olarte, A. Schmidt, T. Schaub,
Hydrothermal liquefaction oil and hydrotreated product from pine feedstock
characterized by heteronuclear two-dimensional NMR spectroscopy and
FT-ICR mass spectrometry, Fuel 137 (2014) 60–69.
4. Conclusions
In summary, we explored a highly efficient synthesis of cyclo-
hexanol from biomass-derived cyclohexanone over Cu powder. As a
result, with optimized conditions in hand, cyclohexanone was com-
pletely converted and obtained a maximum value of 100% in the
presence of 20 mmol Zn and 7.5 mmol Cu powder with 25% water
filling at 250 ◦C for 150 min, which was higher than that of 75.1%
yield using pure H2. From both academic and industrial viewpoints,
the present study is very meaningful to provide an efficient process
for the selective conversion of biomass-derived cyclohexanone to
cyclohexanol with high yield.
Acknowledgments
[19] Z.B. Huo, Y. Fang, D.Z. Ren, S. Zhang, G.D. Yao, X. Zeng, F.M. Jin, Selective
conversion of glucose into lactic acid with transition metal ions in diluted
aqueous NaOH solution, ACS Sustainable Chem. Eng. 2 (2014)
2765–2771.
[20] J.F. Xiao, Z.B. Huo, D.Z. Ren, S. Zhang, J. Luo, G.D. Yao, F.M. Jin, A novel
approach for 1 2-propylene glycol production from biomass-derived lactic
acid, Process Biochem. 50 (2015) 793–798.
[21] S.M. Baghbanian, M. Farhang, CuFe2O4 nanoparticles: a magnetically
recoverable and reusable catalyst for the synthesis of quinolone and
quinazoline derivatives in aqueous media, RSC Adv. 4 (2014) 11624–11633.
Supported by the State Key Program of National Natural Sci-
ence Foundation of China (Grant No. 21436007). Key Basic Research
Projects of Science and Technology Commission of Shanghai
(14JC1403100). The Program for Professor of Special Appoint-
ment (Eastern Scholar) at Shanghai Institutions of Higher Learning
(ZXDF160002). The Project-sponsored by SRF for ROCS, SEM
(BG1600002).
Supported by State Key Laboratory of Fine Chemicals (KF1411).
Please cite this article in press as: Z. Song, et al., Highly selective hydrothermal production of cyclohexanol from biomass-derived
cyclohexanone over Cu powder, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.11.016