Selective hydrogenolysis of glycerol to 1,2-propanediol using heterogeneous copper nanoparticle catalyst derived from CuAl hydrotalcite

Article abstract of DOI:10.1246/cl.130198

The copper nanoparticle catalyst prepared from CuAl hydrotalcite gives an excellent yield of 1,2-propanediol in the hydrogenolysis of glycerol. The copper nanoparticle catalyst also exhibits high durability against sintering during the hydrogenolysis reaction and can be reused without appreciable loss of activity or selectivity.

Full text of DOI:10.1246/cl.130198

doi:10.1246/cl.130198
Published on the web May 25, 2013
729
Selective Hydrogenolysis of Glycerol to 1,2-Propanediol Using Heterogeneous Copper
Nanoparticle Catalyst Derived from Cu­Al Hydrotalcite
1
1
1
1
1,2
Tomoo Mizugaki, Racha Arundhathi, Takato Mitsudome, Koichiro Jitsukawa, and Kiyotomi Kaneda*
1
Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531
2
Research Center for Solar Energy Chemistry, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531
(
Received March 7, 2013; CL-130198; E-mail: kaneda@cheng.es.osaka-u.ac.jp)
The copper nanoparticle catalyst prepared from Cu­Al
hydrotalcite gives an excellent yield of 1,2-propanediol in the
hydrogenolysis of glycerol. The copper nanoparticle catalyst
also exhibits high durability against sintering during the
hydrogenolysis reaction and can be reused without appreciable
loss of activity or selectivity.
Hydrogen gas was then bubbled into the mixture under reflux
conditions for 5 h. After purging the hydrogen gas, the dark
brown solid was recovered by filtration, washed thoroughly with
distilled water, and then dried at 383 K for 12 h in air. ICP-AES
analysis revealed the Cu content to be 48.5 wt %.
The XRD pattern of the Cu­Al HT exhibited the character-
istic diffraction pattern of crystalline hydrotalcite-like com-
pounds with a series of peaks appearing at about 2ª of 11.7,
9
Glycerol is an important renewable raw material which is
mainly obtained as a coproduct of biodiesel production and oleo
23.6, 31.3, 35.6, 40.3, and 48.0°. Treatment of Cu­Al HT under
hydrogen atmosphere in refluxing water gave CuNP@AlO as a
x
1
10
industries. One of the most valuable chemicals derived from
dark brown powder. The XRD pattern of CuNP@AlOx showed
the formation of metallic Cu and Cu2O phases (Figure S1).
8
glycerol is 1,2-propanediol (1,2-PDO), which can be used as an
antifreeze, a solvent, and a preservative in food and tobacco
After the hydrogenolysis reaction, no diffraction peaks derived
from the parent layered hydrotalcite structure and crystalline
aluminum oxides species were observed, which indicated the
formation of an amorphous aluminum oxide phase. The
crystalline size of the Cu metal was estimated to be 20 nm by
1
c
products. 1,2-PDO is commercially produced via the hydration
1c
of propylene oxide from a petrochemicals route. The hydro-
genolysis of glycerol to 1,2-PDO is expected to transition the
traditional petrochemicals process to a green sustainable one.
A number of researchers have reported the hydrogenolysis of
glycerol using heterogeneous catalysts containing group 8­10
11
the Scherrer equation. To compare the catalytic performance,
various inorganic material supported CuNPs of Cu/MgAl-HT,
2
metals. Noble metals of Rh, Pd, Ru, and Pt show high activities
Cu/SiO , Cu/HAP, Cu/£-alumina, and Cu/MgO were prepared
2
9
for the hydrogenolysis of glycerol, but overhydrogenolysis and
C­C bond scission often cause low selectivity for 1,2-PDO at
high conversions of glycerol. Copper is a less expensive metal
and supported copper nanoparticle (CuNP) catalysts have shown
good selectivity for 1,2-PDO in hydrogenolysis of glycerol
by impregnation.
The hydrogenolysis of glycerol to 1,2-PDO was examined
using various Cu catalysts in 1,4-dioxane (Table 1).1 Typical
procedures are as follows: Into a stainless steel autoclave was set
2
μ
a Teflon flask (50 mL), glycerol (0.35 mmol), CuNP@AlOx
3
under gas-phase and liquid-phase conditions. However, CuNP
(25 mg), 1,4-dioxane (5 mL), and a magnetic stirring bar. After
purging the reactor with pressurized hydrogen gas at 0.5 MPa
three times, the reactor was pressurized with 1 MPa of H2 and
then heated in an oil bath at 453 K with vigorous stirring. After
the reaction, the autoclave was cooled with ice water, and the
hydrogen pressure was carefully released. The reaction mixture
was analyzed by GC-FID and GC-MS to determine the
conversion and yield of the products.
catalysts suffer from serious drawbacks such as deactivation by
exposure to air and/or sintering at high reaction temperatures,
which makes it difficult to reuse them. Furthermore, various by-
products are formed at high conversions of glycerol. Therefore,
development of highly selective and robust CuNP catalysts is
strongly desired for 1,2-PDO synthesis.
Hydrotalcite (HT) is a class of layered double hydroxides
having cation and anion exchangeability and tunable surface
Interestingly, among the heterogeneous Cu catalysts,
CuNP@AlOx gave over 99% yield of 1,2-PDO without any
by-products (Entry 3). The CuNPs supported on MgAl-HT also
afforded a good yield of 1,2-PDO with acetone and 2-PrOH
as by-products (Entry 5). In the case of £-Al2O3, SiO2, and
hydroxyapatite (HAP) as supports, the hydrogenolysis did not
proceed efficiently and the Cu species seemed to be deactivated
4
basicity. Using the cation exchangeability of HT, various
transition-metal ions can be incorporated by the isomorphic
2+
3+
substitution of Mg or Al sites in the brucite layer, which
affords a uniformly dispersed active metal species within the HT
5
,6
matrix.
Herein, we developed heterogeneous Cu nanoparticles
embedded within aluminum oxide (CuNP@AlOx) prepared
from copper­aluminum hydrotalcite (Cu­Al HT). CuNP@AlOx
gave almost a quantitative yield of 1,2-PDO from glycerol and
showed high reusability while maintaining activity and selec-
tivity. To our knowledge, CuNP@AlOx is one of the most
1
3
by agglomeration (Entries 7­9). The use of Cu/MgO did not
give 1,2-PDO at all and formation of acetone was observed
(Entry 10).
After the hydrogenolysis reaction, the CuNP@AlOx catalyst
was easily separated from the reaction mixtures by simple
3
14
effective catalysts for hydrogenolysis of glycerol to 1,2-PDO.
filtration in air. The recovered catalyst was washed with 1,4-
Cu­Al HT was prepared by coprecipitation using Cu(NO3)2¢
dioxane, dried in vacuo at room temperature, and then subjected
to reuse without any further treatment. The CuNP@AlOx
catalyst maintained its activity and selectivity at least five
times; 98% yield of 1,2-PDO was obtained even in the fifth
3
H2O and Al(NO3)3¢9H2O according to a modified procedure
7
of reported methods. The preparation of CuNP@AlO was as
x
follows: Five g of Cu­Al HT was dispersed in 50 mL of water.
Chem. Lett. 2013, 42, 729­731
© 2013 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/

7
30
(H2 flow at 1.5 MPa, 478 K, conv. 100%, select. 94%),3h Ni/
alumina­Cu/chromite (H2 1 MPa, 553 K, conv. 30%, select.
Table 1. Hydrogenolysis of glycerol to 1,2-PDO using various
a
Cu catalysts
OH
O
3i
OH
94%), Cu/alumina (H2 flow at 0.1 MPa, gradient temperatures
Cu catalyst
HO
+
HO
3j
HO
OH
from 473 to 393 K, conv. 100%, select. 96%), and Cu/chromite
4
53 K, H2 1 MPa
1
,2-PDO
acetol
3k
(
H2 30 MPa, 473 K, conv. 65.3%, select. 89.6%).
Yield/%b
1,2-PDO acetol
Conv.
Others
/%
No X-ray diffraction peaks derived from the parent layered
Entry Catalyst
b
b
/
%
hydrotalcite structure and crystalline aluminum oxides species
were observed after the hydrogenolysis reaction, which indi-
cated the formation of an amorphous aluminum oxide phase.
1c
CuNP@AlOx
CuNP@AlOx 100
CuNP@AlOx
5th reuse
40
18
98
99
98
21
2
trace
2
0
0
0
0
2
The diffraction pattern of CuNP@AlO after the fifth reuse did
d
x
3
100
100
not change at all from the fresh one, confirming that the sizes of
e
4
0
the Cu and Cu2O nanoparticles in CuNP@AlOx were main-
6
3
(2-PrOH)
(acetone)
f
15
5
Cu/MgAl-HT 100
86
65
70
trace
trace
0
tained during the hydrogenolysis reaction (Figure S1). This
result agrees with the high reusability of the CuNP@AlOx
2+
5
(2-PrOH)
catalyst. Atomically located Cu species within the brucite
6e,f reuse
80
4 (acetone)
5
layer of Cu­Al HT enabled the formation of highly dispersed Cu
0
(2-PrOH)
nanoparticles of Cu and Cu O embedded within the amorphous
2
6
aluminum oxide matrices. High reusability of the CuNP@AlOx
4
3
(acetone)
(1-PrOH)
f
catalyst was attributed to the embedded structure of the
Cu nanoparticles as shown in TEM and FE-SEM images
7
Cu/£-Al O
100
2
3
1
5
f,g
f,g
f
(
Figure S2).
Taking into consideration the product distribution in the
8
9
0
Cu/SiO2
Cu/HAP
Cu/MgO
14
22
18
4
trace
0
0
0
0
8 (2-PrOH)
15 (acetone)
10 (acetone)
hydrogenolysis, the present hydrogenolysis reaction might
1
proceed via a dehydration­hydrogenation pathway through
a
Reaction conditions: glycerol (0.35 mmol), catalyst (25 mg,
2b,3i,3j
acetol as an intermediate.
As shown in Table 1 (Entries
b
Cu: 0.19 mmol), 1,4-dioxane (3 mL), 5 h. Determined by
GCMS using an internal standard. 2 h. 6 h. Details of reuse
1
­3), yields of 1,2-PDO increased and acetol yields decreased
c
d
e
with increasing reaction time. Furthermore, treatment of acetol
in place of glycerol under the present hydrogenolysis conditions
efficiently afforded 1,2-PDO in 98% yield in 5 h. The high
8
f
experiments are described in ESI. Catalyst (Cu: 0.05 mmol).
g
Sintering of Cu NP was observed after the reaction.
selectivity for 1,2-PDO using the CuNP@AlO catalyst might be
x
OH
CuNP@AlO (Cu 20 mol%)
OH
x
due to the high activity for reduction of acetol to 1,2-PDO and
the mild reaction conditions which suppresses the side reactions
HO
OH
HO
.2 g (isolate yield 87%)
1
,4-dioxane 60 mL, 453 K,
7
16,17
1
0 g (110 mmol)
H2 1 MPa, 36 h
such as further dehydration of 1,2-PDO.
In conclusion, Cu nanoparticles embedded in an amorphous
aluminum oxide matrix could be prepared from the crystalline
Cu­Al hydrotalcite as a precursor. The resulting Cu nanoparticle
catalyst afforded quantitative yields of 1,2-PDO even in the fifth
reuse experiment without any pretreatment. The high durability
of the Cu nanoparticle catalyst was attributed to the embedded
structure of the Cu nanoparticles within the amorphous
aluminum oxide matrices.
Scheme 1.
reuse experiment (Entry 4). On the other hand, Cu/MgAl-HT,
which gave good yields of 1,2-PDO in the first run, showed
low yields of 1,2-PDO in the reuse experiment (Entry 6).
Notably, the CuNP@AlO catalyst was applicable under scale-
x
up conditions. Ten g of glycerol, 60 mL of 1,4-dioxane, and
CuNP@AlOx (Cu: 20 mol %) were charged into an autoclave
and pressurized with 1 MPa of H (Scheme 1). After vigorous
This study was partially supported by NEDO and JSPS
KAKENHI (Nos. 22360339, 23360357, and 24246129). The
authors would like to thank Dr. Tetsuo Honma, Dr. Hironori
Ofuchi, and Ms. Sayaka Hirayama (JASRI) for Cu K-edge
XAFS measurements. The authors also thank Mr. Masao
Kawashima (Graduate School of Engineering Science, Osaka
University) for FE-SEM analysis. The TEM experiments were
carried out at a facility of the Research Center for Ultrahigh
Voltage Electron Microscopy, Osaka University. T.M. acknowl-
edges Shorai-Foundation for Science and Technology for the
financial support.
2
stirring at 453 K for 36 h, glycerol was completely converted
to give 1,2-PDO (98% GC yield), and the distillation of the
reaction mixture gave 7.2 g of pure 1,2-PDO (87% isolated
yield).
This CuNP@AlOx catalyst system is one of the most
effective catalyst systems in terms of yield of 1,2-PDO and
catalyst durability, compared with the previously reported ones
that require high temperature, high pressure of H2, and/or
precise temperature control or suffer from leaching of Cu
species, e.g., Cu/boehmite (H 4 MPa, 473 K, conv. 99.5%,
2
3
a
select. 85%), Cu­MgO (H2 4 MPa, 473 K, conv. 49.3%, select.
2.3%), Cu/SiO2 (H2 9 MPa, 453 K, conv. 22.1%, select.
8.7%), Cu0.4/Zn5.6¹xMg Al O (H2 2 MPa, 473 K, conv.
5.5%, select. 98.6%), Pd-deposited CuCr2O4 (H2 4 MPa,
3
b
9
9
8
4
3
References and Notes
3
c
1
Reviews and a book on glycerol transformation: a) A.
Corma, S. Iborra, A. Velty, Chem. Rev. 2007, 107, 2411. b)
M. Pagliaro, R. Ciriminna, H. Kimura, M. Rossi, C. D. Pina,
Angew. Chem., Int. Ed. 2007, 46, 4434. c) A. Behr, J. Eilting,
K. Irawadi, J. Leschinski, F. Lindner, Green Chem. 2008, 10,
x
2
8.6
3d
3e
73 K, conv. 93.9%, select. 99%), Cu0.4/Mg5.6Al2O8.6 (H2
MPa, 493 K, conv. 99%, select. 97%),3 Pd0.04Cu0.4/Mg5.56
f
-
3g
Al2O8.56 (H2 2 MPa, 473 K, conv. 95%, select. 91%), Raney Cu
Chem. Lett. 2013, 42, 729­731
© 2013 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/

7
31
1
3. d) M. Pagliaro, M. Rossi, The Future of Glycerol, 2nd
J. Catal. 2004, 221, 43.
ed., Royal Society of Chemistry, Great Britain, 2010.
doi:10.1039/9781849731089.
7
a) S. Ichikawa, S. Miyazoe, O. Matsuoka, Chem. Lett. 2011,
40, 512. b) A. Alejandre, F. Medina, X. Rodriguez, P.
Salagre, J. E. Sueiras, J. Catal. 1999, 188, 311. Details for
2
a) A. M. Ruppert, K. Weinberg, R. Palkovits, Angew. Chem.,
Int. Ed. 2012, 51, 2564. b) M. Balaraju, V. Rekha, P. S. S.
Prasad, B. L. A. P. Devi, R. B. N. Prasad, N. Lingaiah, Appl.
Catal., A 2009, 354, 82. c) T. Miyazawa, S. Koso, K.
Kunimori, K. Tomishige, Appl. Catal., A 2007, 329, 30. d) T.
Miyazawa, S. Koso, K. Kunimori, K. Tomishige, Appl.
Catal., A 2007, 318, 244. e) I. Furikado, T. Miyazawa, S.
Koso, A. Shimao, K. Kunimori, K. Tomishige, Green Chem.
8
the catalyst preparation was described in ESI.
8
9
Supporting Information is available electronically on the
CSJ-Journal Web site, http://www.csj.jp/journals/chem-lett/
index.html.
N. Voyer, A. Soisnard, S. J. Palmer, W. N. Martens, R. L.
Frost, J. Therm. Anal. Calorim. 2009, 96, 481. Cu­Al HT
(PDF 44­99). Malachite [Cu2(OH)2CO3] phase was negli-
gible.
2007, 9, 582. f) E. P. Maris, R. J. Davis, J. Catal. 2007, 249,
328. g) A. Perosa, P. Tundo, Ind. Eng. Chem. Res. 2005, 44,
8535. h) G. Luo, S. Yan, M. Qiao, J. Zhuang, K. Fan, Appl.
10 Details on the preparation of the catalysts are shown in
8
Supporting Information.
Catal., A 2004, 275, 95. i) C. Montassier, J. C. Ménézo,
L. C. Hoang, C. Renaud, J. Barbier, J. Mol. Catal. 1991, 70,
11 H. P. Klug, L. E. Alexander, X-Ray Diffraction Procedures:
For Polycrystalline and Amorphous Materials, 2nd ed., John
Wiley & Sons, New York, 1974.
9
9.
3
Recent reports on hydrogenolysis of glycerol to 1,2-PDO by
Cu catalysts: a) Z. Wu, Y. Mao, M. Song, X. Yin, M. Zhang,
Catal. Commun. 2013, 32, 52. b) M. Balaraju, K.
Jagadeeswaraiah, P. S. S. Prasad, N. Lingaiah, Catal. Sci.
Technol. 2012, 2, 1967. c) Z. Huang, F. Cui, J. Xue, J. Zuo,
J. Chen, C. Xia, Catal. Today 2012, 183, 42. d) S. Xia, R.
Nie, X. Lu, L. Wang, P. Chen, Z. Hou, J. Catal. 2012, 296, 1.
e) N. D. Kim, J. R. Park, D. S. Park, B. K. Kwak, J. Yi,
Green Chem. 2012, 14, 2638. f) Z. Yuan, L. Wang, J. Wang,
S. Xia, P. Chen, Z. Hou, X. Zheng, Appl. Catal., B 2011,
12 In the case of water as a solvent, the catalyst turned reddish
brown indicating the formation of bulk Cu metal.
13 After the hydrogenolysis reactions using Cu/SiO and Cu/
2
HAP, the color of the catalysts became reddish brown, which
clearly shows the sintering to bulk Cu metal. See ref 3b.
14 The ICP-AES analysis of the filtrate did not show any
leaching of Cu species (below the detection limit, 1 ppb).
15 XRD (Figure S1), TEM and FE-SEM (Figure S2), and Cu
K-edge XANES (Figure S3) analyses of the CuNP@AlOx
catalyst after the fifth reuse experiment revealed the high
stability of the Cu nanoparticles embedded within the
aluminum oxide matrix. The Cu K-edge XANES pattern
1
01, 431. g) S. Xia, Z. Yuan, L. Wang, P. Chen, Z. Hou,
Appl. Catal., A 2011, 403, 173. h) S. R. Schmidt, S. K.
Tanielyan, N. Marin, G. Alvez, R. L. Augustine, Top. Catal.
fitting analysis of the used CuNP@AlO catalyst revealed
x
2
010, 53, 1214. i) A. Marinoiu, G. Ionita, C.-L. Gáspár, C.
that the ratio of Cu(0), Cu2O, and CuO fractions were
80:12:8, which were maintained after the fifth reuse experi-
ment.
Cobzaru, D. Marinescu, C. Teodorescu, S. Oprea, React.
Kinet., Mech. Catal. 2010, 99, 111. j) M. Akiyama, S. Sato,
R. Takahashi, K. Inui, M. Yokota, Appl. Catal., A 2009, 371,
8
16 Preferential adsorption of glycerol over 1,2-PDO on the
aluminum oxide surface was reported. J. R. Copeland, X.-R.
Shi, D. S. Sholl, C. Sievers, Langmuir 2013, 29, 581.
17 The conversion and the selectivity of 1,2-PDO are known
to be very sensitive over the process parameters of the
hydrogenolysis of glycerol and the acid­base properties of
the catalysts (ref 3). R. B. Mane, S. E. Kondawar, P. S.
Niphadkar, P. N. Joshi, K. R. Patil, C. V. Rode, Catal. Today
2012, 198, 321.
6
0. k) M. Balaraju, V. Rekha, P. S. S. Prasad, R. B. N.
Prasad, N. Lingaiah, Catal. Lett. 2008, 126, 119.
F. Cavani, F. Trifirò, A. Vaccari, Catal. Today 1991, 11, 173.
a) T. Matsushita, K. Ebitani, K. Kaneda, Chem. Commun.
4
5
1
999, 265. b) K. Kaneda, T. Yamashita, T. Matsushita, K.
Ebitani, J. Org. Chem. 1998, 63, 1750. c) K. Kaneda, S.
Ueno, T. Imanaka, J. Mol. Catal. A: Chem. 1995, 102, 135.
K. Takehira, T. Shishido, P. Wang, T. Kosaka, K. Takaki,
6
Chem. Lett. 2013, 42, 729­731
© 2013 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/