An efficient noble-metal-free supported copper catalyst for selective nitrocyclohexane hydrogenation to cyclohexanone oxime

Article abstract of DOI:10.1039/c6cc10267k

It was shown for the first time that cyclohexanone oxime (CHO) can be selectively produced by heterogeneous copper-catalyzed hydrogenative transformation of nitrocyclohexane (NC). The combination of Cu⁰ and Cu⁺ and their cooperative interaction with weakly acidic SiO₂ supports elicited a significantly unique and selective catalysis in the hydrogenation of NC to CHO.

Full text of DOI:10.1039/c6cc10267k

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An efficient noble-metal-free Supported Copper Catalyst
for Selective Nitrocyclohexane Hydrogenation to
Cyclohexanone Oxime
Received 00th January 20xx,
Accepted 00th January 20xx
Qian-Qian Zhanga, Jing Donga,b, Yong-Mei Liua*, Yong Caoa，He-Yong Hea, Yang-Dong Wangb*
DOI: 10.1039/x0xx00000x
www.rsc.org/
It was shown for the first time that cyclohexanone oxime (CHO)
can be selectively produced by heterogeneous copper-catalyzed
hydrogenative transformation of nitrocyclohexane (NC). The
combination of Cu0 and Cu+ and their cooperative interaction
with weakly acidic SiO2 supports elicited significantly unique and
selective catalysis in the hydrogenation of NC to CHO.
alternatives to traditional noble metals, we found that a simple nonꢀ
nobleꢀmetalꢀbased catalyst system comprising copper dispersed in
SiO2 matrix can efficiently catalyze the controlled and selective
hydrogenation of NC. Copperꢀcontaining catalysts have been
extensively employed in past decades for the selective elimination of
NOx15, waterꢀgasꢀshift reactions16, synthesis and steam reforming of
methanol.17ꢀ18 Moreover, it is also established that copper catalysts
are very selective for the hydrogenation of dimethyl oxalate19 and
diethyl oxalate20 due to their favorableness as related to the capacity
for hydrogenation in a controlled manner. Herein, we reveal that Cu0
nanoparticles (NPs) with partially reduced Cu+ entrapped in a SiO2
matrix can efficiently catalyze the controlled and highly selective
hydrogenation of NC for the first time. To the best of our
knowledge, this novel Cuꢀmediated catalysis represents the most
convenient, efficient and costꢀeffective catalytic system for the
selective conversion of NC to CHO.
The development of an innovative methodology for the production
of bulk and commodity chemicals, in particular one that takes
account of resource utilization and waste minimization, becomes
more and more important in industrial chemistry worldwide.
Cyclohexanone oxime (CHO) is a privileged raw material for the
production of nylon 6 fibers, which is widely used in synthesis of
polymers for advanced technologies1,2. Currently, CHO is mainly
synthesized through the catalytic oxidation of the cyclohexane to
cyclohexanone (CHone) followed by reaction with hydroxylamine
sulfate3,4, the limitation of traditional CHO synthetic methodologies
such as producing ammonium sulfate and the use of hazardous
chemicals5ꢀ8
, which has stimulated considerable interest in
developing new, efficient, catalytic methods for the synthesis of
CHO. In this context, the direct hydrogenation of nitrocyclohexane
(DHNC) to give CHO is particularly attractive because NC can now
be readily prepared from the corresponding cyclohexane9,10
.
Converting NC to CHO, however, can be challenging because
DHNC can undergo several reduction pathꢀ ways, which compete
with each other (Scheme 1), and the chemoꢀselectivity of these
reactions must therefore be strictly controlled to avoid the formation
of undesirable byproducts.
Over the last decade, a number of supported noble metals, notably
palladium, have been shown to facilitate NCꢀtoꢀCHO transformation,
with a maximum yield of ca. 90% can be achieved6,11ꢀ14. From
economical and practical point of view, the development of a
reusable and less expensive baseꢀmetal catalyst is highly desirable.
In our pursuit of new costꢀeffective catalysts that can offer efficient
Scheme 1. The proposed reaction mechanism for the hydrogenation
of nitrocyclohexane.
We began our study by synthesizing a series of Cu/SiO2 with
the same Cu loading of 15 wt. % by different preparation methods,
including ammonia evaporation hydrothermal method (AE),
conventional precipitationꢀdeposition method (DP), solꢀgel method
(SG) and traditional incipient wet impregnation method (Imp) 19, 21
.
The asꢀprepared Cu/SiO2 precursors were calcined in air at 600°C
for 4 h, followed by reduction with 5 vol. % H2/Ar at 300 oC for 2 h,
which were denoted as 15Cu/SiO2ꢀAE, 15Cu/SiO2ꢀSG, 15Cu/SiO2ꢀ
DP and 15Cu/SiO2ꢀImp, respectively. The reducedꢀCu/SiO2 hybrid
materials were then tested for the DHNC under 1 MPa H2 at 100 °C
for 3 hours. To our delight, it was found that 15Cu/SiO2ꢀAE gave the
highest catalytic activity with excellent selectivity of CHO of 92 %
[a]
Department of Chemistry, Shanghai Key Laboratory of Molecular
Catalysis and Innovative Materials, Fudan University, Shanghai
200433, P. R. China Email: ymliu@fudan.edu.cn
[b] SINOPEC Shanghai Research Institute of Petrochemical Technology,
Shanghai 201208,P.R. China Email: wangyd.sshy@sinopec.com
Electronic Supplementary Information (ESI) available:
Experimental section, TEM and XPS data. See DOI:
10.1039/b000000x/
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among all the samples tested under the identical conditions (Table 1,
entry 1ꢀ4), which could be ascribed to its highly porous surface
texture as inferred from the N2 adsorption isotherms (Figure S1),
13
15Co/SiO2
4
12
ꢀ
88
359
ꢀ
ꢀ
[a] nitrocyclohexane 0.77 mmol, catalyst 20 mg, ethylenediamine 5
highly exposed, properly assembled acid sites (Figure S2), N2O mL, time 3 h, H2 pressure 1 MPa. [b] Dispersion of copper species
and copper surface area determined by N2O titration method.
titration and BrunauerꢀEmmettꢀTeller (BET) surface areas (Table 1),
H2 temperatureꢀprogrammed reduction (TPR) (Figure S3),
respectively. Indeed, the number of accessible surface Cu atoms was
reported to account for the catalytic hydrogenation performance21.
To further understand the origin of the catalytic reactivity over
Cu/SiO2 catalysts, we then set out to optimize the Cu/SiO2ꢀAE by
altering the Cu content during the preparation procedure. Table 1
shows that the 15Cu/SiO2ꢀAE (entry 4ꢀ7) catalyst exhibited superior
catalytic reactivity in comparison with the others. To gain more
detailed insight into the reaction performed with 15Cu/SiO2ꢀAE, the
timeꢀcourse plot for the above mentioned DHNC to CHO transꢀ
formation was examined (Figure S4). The reaction proceeded
smoothly and was completed within 4 h. During the whole reaction
process, cyclohexylamine (CHA) and cyclohexanone (CHone) were
the only byꢀproducts with very low selectivity and without detecting
any other intermediates. After 4 h, the yield of CHO approached
92% at full NC conversion, with unwanted byproducts essentially
being prevented to be formed during the reaction. Furthermore, in a
series of additional studies examining the effect of pressure, it was
revealed that the reaction time was greatly shortened from 4 to 1 h as
PH2 was increased from 1 to 4 MPa (Table S1). Subsequent
experiments focused on the effect of the reaction temperatures
revealed that under otherwise identical reaction conditions the
15Cu/SiO2ꢀAE catalyst exhibited rather low activity at 60 °C (Table
S2, entry 4). Notably, at an elevated temperature of 120 °C,
prominent formation of CHO can be attained within 1.5 h (Table S2,
entry 1).
Figure 1. (A) TEM images of 15Cu/SiO2ꢀAE catalyst, (B) the
corresponding particle size distributions and the corresponding (C)
Si, (D) Cu elemental mapping of 15Cu/SiO2ꢀAE catalyst. (E)
HRTEM images of 15Cu/SiO2ꢀAE catalysts.
Table 1. Physicochemical properties and Catalytic Performance.[a]
To further confirm the effectiveness of the present system, a 50
mmol scale hydrogenation of NC was carried out. The DHNC
proceeds efficiently, and the corresponding CHO could be obtained
in 91% yields (supporting information). After completion of the first
hydrogenation, the 15Cu/SiO2ꢀAE catalyst was readily separated
from the reaction mixture through simple filtration. For each
successive use, the filtered catalyst was subjected to calcination in
air at 600 oC for 4 h, and then reduced with 5% H2/Ar at 300 oC for 2
h. After this treatment, the activity of the recovered catalyst can also
be reused at least three times without an appreciable loss of activity
on this scale. Moreover, catalyst leaching was not observed, as
indicated by the absence of copper ion in the product solution after
each catalyst reuse (the Cu content of the catalysts and solutions
were determined by inductively coupled plasma atomic emission
spectroscopy (ICPꢀAES) analysis).
Ent Catalyst
ry
Conv
.
(%)
Sel. (%)
3
SBET
(m2
gꢀ1)
SCu
SCu
(m2
gcatal
(m2
ꢀ
ꢀ
gCu
)
2
4
1
[b]
1
[b]
)
1
15Cu/SiO2ꢀDP
50
7
70
67
64
92
76
77
65
49
53
77
59
25
18
1
12
32
35
5
162
176
186
352
428
265
164
50
22
8
148
55
2
15Cu/SiO2ꢀImp
15Cu/SiO2ꢀSG
15Cu/SiO2ꢀAE
10Cu/SiO2ꢀAE
30Cu/SiO2ꢀAE
50Cu/SiO2ꢀAE
15Cu/ZrO2
3
8
1
9
59
4
74
32
66
41
19
55
29
19
8
3
39
22
39
16
11
24
15
ꢀ
261
220
130
33
Imaging the nanocomposites of 15 Cu/SiO2ꢀAE after reduction
5
6
18
15
23
23
47
18
21
75
o
in H2/Ar flow at 300 C using TEM (Figure 1A) reveals the high
6
8
dispersity of partially reduced CuOx particles with uniform morphoꢀ
logy embedded in SiO2 matrix. The CuOx particles have an average
size of ~3 nm and a narrow size distribution (Figure 1B) and the
element mapping (Figure 1C, 1D) results confirmed the homoꢀ
geneous elemental dispersion. It is interesting to find two sets of
lattice fringes in the 15 Cu/SiO2ꢀAE from HRTEM image (Figure
2E), the lattice spacing of ∼0.208 and ∼0.24 nm presented in the
picture corresponds to the Cu (111) (JCPDS 04ꢀ0836) and Cu2O
(111) (JCPDS 05ꢀ0667) plane, respectively22. The XRD patterns of
the Cu/SiO2ꢀAE samples after calcination are shown in Figure S5
(A). In agreement with the TEM results, no diffraction peaks of any
7
12
28
ꢀ
8
73
9
15Cu/Al2O3
300
90
160
100
ꢀ
10
11
12
15Cu/CeO2
5
15Ni/SiO2
20
ꢀ
382
373
15Fe/SiO2
ꢀ
ꢀ
2 |ChemComm., 2016, 00, 1-3
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crystalline phase of copper species were observed when the Cu ZrO2 and CeO2 were selected as amphoteric and weakly basic oxide
loading was lower than 15%，revealing that an excellent component supports. Cu/CeO2, Cu/Al2O3, and Cu/ZrO2 catalysts possess lower
dispersion can be readily achieved via the present simple oneꢀpot activities than the Cu/SiO2 catalyst, which could be ascribed to the
method. The results of reduced samples in Figure S5 B show there lower CuOx dispersions, limited exposure of surface Cu atoms as
are no obvious diffraction peaks at 2θ=43.3o corresponding to seen from Table 1. The fact that these catalysts can only afford very
Cu(111) for the lower loaded Cu/SiO2 (< 15%), which also suggests limited selectivity toward CHO formation further confirms that an
the presence of a well dispersed metal phase. The Cu LMM XAES optimal balance of the different catalytically active sites is essential
(Figure S6 and S7) results revealed that the Cu species on the to maximize the efficacy of the CHO production and minimize the
reduced Cu/SiO2 catalysts are Cu0 and Cu+, these findings infer that undesired CHone generation. A clear advantage of the Cu/SiO2
the metallic copper and Cu2O coexisted in the working catalyst, catalyst over other abundant metals was also noticed when the reactiꢀ
which confirmed the HRTEM results23.
on was performed using Ni/SiO2, Fe/SiO2 or Co/SiO2 under otherꢀ
wise identical conditions (Table 1, entries 11ꢀ13). It is important to
remark that the performances of Cu/SiO2 were comparable to or
even higher than those of the typical noble metal catalysts or Cu
salts6,11ꢀ14. These results indicate that the cooperation of SiO2 support
and copper play a key role in enabling high performance via
maintaining high copper dispersion and weak surface acidity.
During the hydrogenation of NC reaction, it is generally believꢀ
ed that CHA and CHone require several reaction steps to be prodꢀ
uced from NC and they were expected to appear as the secondary
products4,11,14. In fact, one could consider that while CHA could be
produced by consecutive hydrogenation reactions (see Scheme 1a)
25,26, CHone could be produced by hydrolysis of CHO27ꢀ30 with the
water formed during the first hydrogenation step. Generally, it is
well known that this reaction may be catalyzed either by Brönsted or
Lewis acid sites27ꢀ29. In order to check if the formation of CHone is
directly formed by hydrolysis of CHO over 15Cu/SiO2ꢀAE, CHO
was reacted under conditions either in the presence of stoichiometric
amounts of water and/or in absence of H2. The results in Table S3
show that when this reaction was carried out with the 15Cu/SiO2ꢀAE
catalyst, only 0.5 % conversion of the CHO is observed after 3 h,
indicating that this compound is stable against hydrolysis especially
in absence of H2, inferring that the very weak acid character of
15Cu/SiO2ꢀAE is essential for this beneficial effect.12
Figure 2. (A) Yield of CHO as a function of Cu loading. (B)
Correlation of the MASCu of NC with Cu0/(Cu0 + Cu +).
We therefore checked the effect of the water on hydrogenation
To gain further insight into the effect of the chemical state of
Cu on the selective hydrogenation of NC to CHO, we examined the of NC under otherwise identical hydrogenative conditions. Results in
effect of Cu loading on the CHO yield and the mass specific activity
of Cu (MASCu, the NC consumption rate by mol hꢀ1 gCuꢀ1) of NC as a
function of Cu0/(Cu0 + Cu+) (Figure 2) or copper metal surface area
(Figure S8). It was revealed that MASCu of NC did not exhibit
monotonous variation with increasing the copper metal surface area
but was concerned with the surface Cu0/Cu0+Cu+ ratio, and the
MASCu of NC increased steadily at low Cu0/(Cu0 + Cu+), reaching a
property of Cu0/(Cu0 + Cu+) at 15Cu/SiO2ꢀAE, then decreasing upon
further increases in Cu loading (Figure 2B). Therefore, the optimal
MASCu of NC on the 15Cu/SiO2ꢀAE catalyst could be related to its
higher surface Cu0 site density (Table 1) as well as the cooperative
effect of Cu0 and Cu+ species. The critical role of Cu0/ (Cu0 + Cu+)
was further confirmed by comparing the catalytic performance of
15Cu/SiO2ꢀAE, 15Cu/SiO2ꢀImp and 15Cu/SiO2ꢀSG with their
structural parameters, wherein it was found that 15Cu/SiO2ꢀAE
possessing suitable Cu0/(Cu0 + Cu+) ratio showed the highest CHO
yield. Taken together, these results demonstrate that, as a result of an
optimal cooperative interaction between Cu0 and Cu+ species, the
15Cu/SiO2ꢀAE sample afforded the highest catalytic activity and
selectivity for hydrogenation of NC to CHO. It is very likely that
Cu0 species dissociate H2, and Cu+ sites function as electrophilic
sites to polarize the nitro groups, similar with the dimethyl oxalate
hydrogenation 23,24. The balanced Cu0 and Cu+ sites can improve the
activity and selectivity.
Table S4 show that the introduction of water would lead to
formation of appreciable amounts of CHone, with the selectivity of
CHone increased up to 35 % on increasing the amount of water to 20
equivꢀ alent. All these results proved that the formation of CHone
during the hydrogenation of NC must occur through a catalytic route
other than the direct hydrolysis of CHO by water. At this point, it
should be mentioned that CHO can also be reduced with H2 in the
presence of certain metalꢀbased catalysts, forming either CHA or
CHone.31ꢀ33 So it is reasonable that CHone may be initially reduced
to an unstable intermediate (presumably cyclohexylimine), which
could be further hydrogenated to give the amine, or hydrolyzed
giving the cyclic ketone as reaction product.12 Taken together, it
appears that the formation of CHA, and CHone over 15Cu/SiO2ꢀAE
may proceed mainly via reaction pathway as given in Scheme 1b.
In summary, we have demonstrated that a highly active and
robust catalyst based on a simple nonꢀnoble Cu/SiO2ꢀbased catalyst
can be used to convert NC into CHO under mild hydrogenative conꢀ
ditions in excellent yields. It was observed that the optimal combiꢀ
nation of partially reduced CuOx NPs and weakly acidic SiO2 suppꢀ
orts are essential for attaining excellent selectivity for CHO in the
hydrogenation of nitrocyclohexane. The present finding forms the
basis for costꢀcompetitive producing CHO from NC and the develoꢀ
pment of new sustainable, economically affordable process for the
Besides SiO2, ZrO2, Al2O3 and CeO2 were also used as supportꢀ
ing substrates for the DHNC reaction. As shown in Table 1 entry 8ꢀ
10, Al2O3 was chosen as a representative acidic oxide support, and
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production of bulk and commodity chemicals that are typically
mediated by catalysts containing precious metals.
20 (a) J. Ding, J. Zhang, C. Zhang, K. F. Liu, H. C. Xiao,
F. H. Kong and J. G. Chen, Appl. Catal. A, 2015, 508,
68; (b) B. W. Wang, X. Zhang, Q. Xu and G. H. Xu,
Chin. J. Catal., 2008, 29, 275.
This work was supported by National Natural Science Foundꢀ
ation of China (21273044, 21473035, and 91545108), SINOPEC
(X514005), and the Open project of State Key Laboratory of
Chemical Engineering (SKLꢀChEꢀ15C02).
21 (a) L. F. Chen, P. J. Guo, M. H. Qiao, S. R. Yan, H. X.
Li, W. Shen, H. L. Xu and K. N. Fan, J. Catal., 2008,
257, 172; (b). J. Yuan, S.S. Li, L. Yu, Y.M. Liu, Y.
Cao, H.Y. He, K.N. Fan, Energy Environ. Sci., 2013, 6,
3308.
22 Y.F. Zhu, X. Kong, D.B. Cao, J.L. Cui, Y.L. Zhu, Y.W.
Li, ACS Catal. 2014, 4, 3675.
Notes and references
23 J. L. Gong, H. R. Yue, Y. J. Zhao, S. Zhao, L. Zhao, J.
Lv, S. P. Wang, X. B. Ma, J. Am. Chem. Soc., 2012,
134, 13922.
24 Y.F. Zhu, X. Kong, X.Q. Li, G.Q. Ding, Y. L. Zhu,
Y.W. Li, ACS Catal. 2014, 4, 3612.
25 A. Bose and C. R. Saha, J. Mol. Catal., 1989, 49, 271.
26 S. M. Islam and C. R. Saha, J. Mol. Catal. A, 2004, 212,
131.
27 C. Ngamcharussrivichai, P. Wu and T. Tatsumi, J.
Catal., 2004, 227, 448.
28 M. A. Camblor, A. Corma, H. García, V. Semmerꢀ
Herlédan and S. Valencia, J. Catal., 1998, 177, 267.
29 N. C. Marziano, L. Ronchin, C. Tortato, A. Vavasori
and C. Badettia, J. Mol.Catal. A, 2007, 277, 221.
30 K. You, L. Mao, D. Yin, P. Liu and H. Luo, Catal.
Commun., 2008, 9, 1521.
31 E. Breitner, E. Roginski and P. N. Rylander, J. Chem.
Soc., 1959, 2918.
32 D. P. Curran, J. F. Brill and D. M. Rakiewicz, J. Org.
Chem., 1984, 49, 1654.
1
2
H. Ichihashi and H. Sato, Appl. Catal. A, 2001, 221,
359.
G. Dahlhoff, J. P. M. Niederer and W.F. Hoelderich,
Catal. Rev. Sci. Eng., 2001, 43, 381.
“KirkꢀOthmer Encyclopedia of Chemical Technology”,
Wiley, New York, 1982, 18, 432.
J. Le Bars, J. Dakka and R.A. Sheldon, Appl. Catal. A-
Gen., 1996, 136, 69.
J. A. Robertson, J. Org. Chem., 1948, 13, 395.
DuPont, GB Patent 857, 902, 1961.
3
4
5
6
7
8
9
J. F. Knifton, J. Catal. 1974, 33, 289.
T. Tatsumi and N. Jappar, J. Catal., 1996, 161, 570.
S. Sakaguchi, Y. Nishiwaki, T. Kitamura and Y. Ishii,
Angew. Chem. Int. Ed., 2001, 40, 222.
10 K. Yamaguchi, S. Shinachi and N. Mizuno, Chem.
Commun., 2004, 424.
11 A. Corma and P. Serna, science, 2006, 313, 332.
12 P. Serna, M. LopezꢀHaro, J. J. Calvino and A. Corma, J.
Catal., 2009, 263, 328.
13 a) K. ꢀi. Shimizu, T. Yamamoto, Y. Tai and A.
Satsuma, J. Mol. Catal. A, 2011, 345, 54; b) X. D.
Wang, N. Perret and M. A. Keane, Appl. Catal. A, 2013,
467, 575.
33 K. A. Manbeck, N. E. Musselwhite, L. M. Carl, C. A.
Kauffman, O. D. Lyons, J. K. Navin and A. L. Marsh,
Appl. Catal. A, 2010, 384, 58.
14 (a) H. G. Liao, Y. J. Xiao, H. K. Zhang, P. L. Liu, K. Y.
You, C. Wei and H. A. Luo, Catal. Commun., 2012, 19,
80; (b) P. L. Liu, H. K. Zhang, S. H. Liu, Z. J. Yao, F.
Hao, H. G. Liao, K. Y. You and H. A. Luo,
ChemCatChem, 2013, 5, 2932; (c) Y. H Yan, S. H Liu,
F. Hao, P. L. Liu and H. A. Luo, Catal. Commun.
2014, 50, 9.
,
15 (a) H. A. Habib, R. Basner, R. Brandenburg, U.
Armbruster, and A. Martin, ACS Catal., 2014, 4, 2479.
(b) J. C. Wang, Z. L. Peng, H. Qiao, H. F. Yu, Y. F. Hu,
L. P. Chang, and W. R. Bao, Ind. Eng. Chem. Res.
2016, 55, 1174.
,
16 I. Atake, K. Nishida, D. Li, T. Shishido, Y. Oumi, T.
Sano and K. Takehira, J. Mol. Catal. A: Chem., 2007,
275, 130.
17 (a) G. H. Graaf, E. J. Stamhuis and A. A. C. M.
Beenackers, Chem. Eng. Sci., 1988, 43, 3185. (b) C.
Baltes, S. Vukojević and F. Schüth, J. Catal., 2008,
258, 334.
18 (a) J.ꢀP. Shen and C. Song, Catal. Today, 2002, 77, 89.
(b) J. Agrell, H. Birgersson, M. Boutonnet, I. Meliánꢀ
Cabrera, R. M. Navarro and J. L. G. Fierro, J. Catal.
2003, 219, 389.
,
19 (a)H. Kouichi, U. Taizou and N. Yasuo, US4614728,
1986; (b) J.L. Gong, H.R.Yue, Y.J. Zhao, S. Zhao, L.
Zhao, J. Lv, S.P. Wang, X.B. Ma, J. Am. Chem. Soc.
2012, 134, 13922.
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