The synthesis of propylene glycol and ethylene glycol from glycerol using Raney Ni as a versatile catalyst

Article abstract of DOI:10.1039/b913395j

A new energy-efficient and atom-economical catalytic route for the direct catalytic synthesis of propylene glycol and ethylene glycol from glycerol under milder reaction conditions is presented. The one-pot aqueous-phase process is based on Raney Ni as a versatile catalyst. The Royal Society of Chemistry 2009.

Full text of DOI:10.1039/b913395j

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www.rsc.org/greenchem | Green Chemistry
The synthesis of propylene glycol and ethylene glycol from glycerol using
Raney Ni as a versatile catalyst†
An-Yuan Yin,‡ Xiu-Ying Guo,‡ Wei-Lin Dai* and Kang-Nian Fan
Received 8th July 2009, Accepted 5th August 2009
First published as an Advance Article on the web 14th August 2009
DOI: 10.1039/b913395j
7
A new energy-efficient and atom-economical catalytic route
for the direct catalytic synthesis of propylene glycol and
ethylene glycol from glycerol under milder reaction condi-
tions is presented. The one-pot aqueous-phase process is
based on Raney Ni as a versatile catalyst.
with selectivity of >95%. Another way of converting glycerol
to PG is the use of ruthenium in combination with acids
or ion-exchange resins, which enables slightly milder reaction
8
conditions, but also lower conversions and selectivities. As in the
case of Rh as a catalyst, reaction conditions are relatively mild.
The use of Rh as a catalyst component in a multimetallic catalyst
9
Propylene glycol (PG) and ethylene glycol (EG), used as high
value-added speciality chemical intermediates, are widely used
for manufacturing polyester fibers, unsaturated polyester resins,
leads to conversions up to 80% with selectivities of >30% at a
temperature higher than 393 K and 8 MPa hydrogen pressure.
9
In all the cases, either selectivity was low or high pressure, high
temperature and very complex catalytic systems were required.
Although the hydrogenolysis of glycerol opened up a new
approach to synthesize PG and EG, high hydrogen pressure
(8 MPa), high temperature (473 K) and use of expensive
noble metal catalysts are still key factors to limit its further
application in industry. The reaction mechanism on metallic
metal is accepted as glycerol dehydration under the acid or
base environment firstly, then hydrogenation to PG over metal
1
antifreeze, pharmaceuticals and other important products.
At present, these two diols are mainly produced from the
hydration of corresponding epoxy alkanes, which are commonly
2
derived from a petrochemical approach. However, as crude oil
resource shrinks, synthesis of the two diols from biomass glycerol
3
attracts more and more interest. With the rapid development
of the bio-diesel industry by transesterification of seed oils
with methanol, glycerol of renewable origin, as a by-product
of bio-diesel production, seems to be an attractive option as a
10
catalyst. Aqueous phase reforming (APR) can be used to
4
new feedstock. Glycerol, as a nontoxic, edible, biodegradable
convert glycerol with water into H
near 500 K over metallic catalysts. Importantly, the selectiv-
2
3
and CO at temperatures
2
and low-cost polyfunctional molecule, has been regarded as
one of the building blocks in the biorefinery industry. Various
conversions of glycerol into value-added chemicals, including
selective oxidation, esterification, hydrogenolysis, dehydration
and reforming, have received significant attention during the
last few decades because the cost of glycerol as a by-product
is projected to decrease significantly as biodiesel production
ity towards H can be controlled by altering the nature of
2
the catalytically active metal sites (e.g., Pt) and metal-alloy
(e.g., Ni-Sn) components, and by choice of catalyst support to
obtain higher production of hydrogen at higher pressure (3–4
MPa) and slightly lower temperature (398 K), which is thermo-
11
dynamically favorable to the water-gas-shift reaction. Based
on the above reaction process, the direct catalytic conversion
of glycerol to PG and EG with water can be carried out by
combining the APR process and the hydrogenolysis of glycerol
using the hydrogen produced in situ by the APR process, which
can not only save energy but also allow easy control of the
reaction under mild conditions.
5
increases.
On the whole, the large surplus of glycerol in association with
its high functionalization makes it one of the most promising
platform chemicals of the near future. Also, converting glycerol
into value-added products provides an alternative for glycerol
disposal and for its surplus problems. Among the various
glycerol transformations, much attention has been paid to
synthesizing propanediol and EG via the hydrogenolysis of
glycerol. Catalysts containing an active copper compound such
The present study firstly reports a new route to produce PG
and EG from glycerol under 0.1 MPa nitrogen atmosphere
conditions (Scheme 1). In particular, Raney Ni is strongly active
for this glycerol catalytic conversion process and the products
are easy to separate from the reaction system without further
purification.
as Cu-chromite, Cu-ZnO, Cu-SiO
2
or Cu-Al
2
3
O are active in
glycerol hydrogenation at temperature between 423–593 K and
6
pressure between 10 and 25 MPa. Under similar reaction
conditions, a catalyst system containing Co, Cu, Mn, Mo as well
as inorganic polyacids, leads to nearly quantitative conversions
Department of Chemistry & Shanghai Key Laboratory of Molecular
Catalysis and Innovative Material, Fudan University, Shanghai, 200433,
P. R. China. E-mail: wldai@fudan.edu.cn; Fax: (+86-21) 55665572;
Tel: (+86-21) 55664678
Scheme 1 Reaction approach to propylene glycol and ethylene glycol
derived from glycerol reforming.
†
Electronic supplementary information (ESI) available: Experimental
In the present work, the chemo-selectively catalytic conversion
of glycerol to PG and EG is carried out over commercial
section, TEM and XRD data. See DOI: 10.1039/b913395j
‡
These authors contributed equally to this work.
1
514 | Green Chem., 2009, 11, 1514–1516
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a
Table 1 Effect of reaction temperature on the catalytic performance
Table 3 Results of the reactions of various compounds
a
over Raney Ni catalyst
c
Selectivity (%)
c
Selectivity (%)
b
Reactant Conversion (%) Yield (%)
PG
EG
Ethanol
b
T/K
Conversion (%)
Yield (%)
PG
EG
Ethanol
PG
EG
35
64
5.5
19
0
0
0
0
100
100
433
443
453
463
473
49.2
64.3
100
100
100
36.3
41.1
58.2
51.4
47.2
37.2
42.1
43.0
43.9
48.7
61.8
56.3
55.0
51.5
44.5
1.0
1.6
2.0
4.6
6.8
a
Reaction conditions: 453 K, 30 ml aqueous glycerol (10 wt%), catalyst
b
c
(
2
1 g), N (0.1 MPa), 1 h. Total yield of liquid products. C-based
composition of liquid products/mol%.
a
Reaction conditions: 30 ml aqueous glycerol (10 wt%), catalyst (1 g),
b
c
N
2
(0.1 MPa), 1 h. Total yield of liquid products. C-based composition
total yield of the diols increased with prolonging of the reaction
time; however, the yield of diol would decrease upon further
extending of the reaction time. Based on the distribution of the
products, extending the reaction time could lead to further C–C
cleavage, and as a result, PG would further degrade to EG.
In addition, the effect of glycerol concentration and the
amount of catalyst on the glycerol reaction over Raney Ni
catalyst was also investigated. Higher conversion was obtained
at lower glycerol concentrations. 100% glycerol conversion and
of liquid products/mol%.
Raney Ni catalysts (A.R., Sinopharm Chemical Reagent Ltd.)
in a stainless steel autoclave. Thirty millilitres of an aqueous
solution of glycerol (10 wt%) was used as the reactant. No
additives, including alkaline, were needed. All the products are
quantitatively analyzed by a gas chromatograph equipped with
an FID detector.
It is interesting to find that a high pressure of hydrogen was not
favorable to this reaction. Under 3 MPa H , only 50% conversion
of glycerol was observed. On the contrary, air is not good for this
reaction, since fresh Raney Ni is very active and it is not safe to
carry out this reaction under air atmosphere. Inert atmosphere
at ambient pressure was found to show unique advantages in this
5
1
8.5% yield of total liquid products could be obtained when a
0% aqueous solution of glycerol was used (see Table S1, ESI).†
2
Taking into consideration actual application, all the experiments
were carried out using 10% glycerol concentration. The glycerol
conversion was markedly enhanced by increasing the amount
of the catalyst; however, the total yield of the liquid products
decreased, which indicated that further C–C cleavage happened
process. Thus, we choose 0.1 MPa N as the optimal atmosphere.
2
(
see Table S2, ESI).† It is necessary to optimize the amount of
Table 1 shows the effect of reaction temperature on the catalytic
performance of glycerol conversion over Raney Ni catalyst. As
can be seen, 100% glycerol conversion and 57.0% yield of total
diols could be obtained at 453 K. Compared with the theoretical
yield of the diols (75%), this result is rather high over the Raney
Ni catalyst. Although 100% glycerol conversion could still be
retained with further increasing of the reaction temperature, the
total yield of diols decreased. This may be a result of the further
hydrogenolysis of the diols and the methanation under higher
reaction temperature. Based on the distribution of the products
upon the variation of reaction temperatures, higher temperature
is helpful to the cleavage of the C–O bond while inhibiting the
cleavage of the C–C bond, and further degradation of the diols
could happen at higher reaction temperatures.
catalyst to obtain the highest yield of diols. Besides, the catalyst
showed good stability because it could be easily recovered after
reaction and reused three times without any significant loss of
its activity.
To further elucidate the reaction processes, PG and EG were
also used as the reactants (see Table 3). Indeed, further C–C
cleavage and C–O cleavage could happen under the reaction
conditions. Combining the gas-phase product (only CH
CO were detected by GC), the possible reaction process could
be proposed as the following (Scheme 2): firstly, aqueous glycerol
reforming reaction happened to form CO and active H atoms
4
and
2
2
that were produced in situ on the Raney Ni catalyst, and the
active H atoms were expected to show high hydrogenolysis
activity; secondly, hydrogenolysis of glycerol to PG and EG with
active H atoms over Raney Ni happened. During the reaction
To obtain an insight into the origin of the reaction processes,
we examined the course of the conversion of glycerol aqueous
solution over time. The time course of the products distribution
is given in Table 2. As can be seen, the glycerol conversion and the
Table 2 Effect of reaction time on the catalytic performance over
a
Raney Ni catalyst
c
Selectivity (%)
b
Time/h
Conversion (%)
Yield (%)
PG
EG
Ethanol
0.5
1.0
1.5
2.0
74.2
100
100
42.0
58.2
47.4
41.1
26.2
43.0
42.2
29.2
71.4
55.0
54.9
68.1
2.4
2.0
2.9
2.7
100
a
Reaction conditions: 30 ml aqueous glycerol (10 wt.%), catalyst (1 g),
2
(0.1 MPa), 453 K. Total yield of liquid products. C-based
b
c
N
composition of liquid products/mol%.
Scheme 2 Proposed reaction pathway under the reaction conditions.
Green Chem., 2009, 11, 1514–1516 | 1515
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course, further degradation of diols and methanation were the
main side reactions.
Science & Technology Committee (08DZ2270500, 06JC14004)
is kindly acknowledged.
In conclusion, a new and efficient catalytic route for the
production of PG and EG by catalytic combination of glycerol
aqueous reforming and hydrogenation of glycerol has been
developed using the commercial Raney Ni as catalyst. The new
route provides a feasible approach for the direct use of a by-
product of bio-diesel, facilitating an energy-efficient and atom-
economic process. This process can be commercialized easily
according to the following considerations. Firstly, the reaction
conditions are much milder than those previously reported, since
no hydrogen was needed and the reaction can be conducted
under ambient pressure and the diluted aqueous glycerol can
be directly used as the substrate without any concentration.
Secondly, the catalyst is the commonly used commercial Raney
Ni which is remarkably cheaper than the noble metal catalysts.
It is interesting to find that the Raney Ni can be easily
recovered from the reaction mixture by filtration or magnetic
separation since Raney Ni is paramagnetic, and the catalyst can
be conveniently reused without any further treatment. Thirdly,
the two diol products can be easily separated from the reaction
system because glycerol is totally converted and the catalyst can
be easily removed. Finally, the gaseous products are very useful
Notes and references
1
2
3
G. H. Xu, Y. C. Li and H. J. Wang, Ind. Eng. Chem. Res., 1995, 34,
2371.
T. Haas, B. Jaeger, R. Weber and S. F. Mitchell, Appl. Catal., A, 2005,
2
80, 83.
(a) R. D. Cortright, R. R. Davda and J. A. Dumesic, Nature, 2002,
418, 964; (b) G. W. Huber, J. W. Shabaker and J. A. Dumesic, Science,
2003, 300, 2075; (c) G. A. Deluga, J. R. Salge, L. D. Schmidt and
X. E. Verykios, Science, 2004, 303, 993; (d) M. Asadullah, S. Ito, K.
Kunimori, M. Yamada and K. Tomishige, J. Catal., 2002, 208, 255.
G. W. Huber, J. N. Chheda, C. J. Barrett and J. A. Dumesic, Science,
2005, 308, 1446; G. W. Huber, J. N. Chheda, C. J. Barrett and J. A.
Dumesic, Pure Appl. Chem., 1997, 69, 1853.
4
5
(a) J. N. Chheda, G. W. Huber and J. A. Dumesic, Angew. Chem.,
Int. Ed., 2007, 46, 7164; (b) M. Pagliaro, R. Ciriminna, H. Kimura,
M. Rossi and C. D. Pina, Angew. Chem., Int. Ed., 2007, 46, 4434;
(c) A. Behr, J. Eilting, K. Irawadi, J. Leschinski and F. Lindner,
Green Chem., 2008, 10, 13.
6
7
(a) C. Montassier, D. Giraud, J. Barbier and J. P. Boitiaux, Bull. Soc.
Chim. Fr., 1989, 2, 148; (b) C. Montassier, D. Giraud and J. Barbier,
Stud. Surf. Sci. Catal., 1988, 41, 165; (c) C. Montassier, J. M. Dumas,
P. Granger and J. Barbier, Appl. Catal., A, 1995, 121, 231; (d) C.
Montassier, J. C. Menezo, J. Moukolo, J. Naja, L. C. Hoang and J.
Barbier, J. Mol. Catal., 1991, 70, 65.
S. Ludwig and E. Manfred, US Pat., 5 616 817, 1997.
since they are mixture of CH
which is very convenient for its further use as fuel or a hydrogen
resource.
4
and CO
2
, no CO was detected,
8 (a) Y. Kusunoki, T Miyazawa, K. Kunimori and K. Tomishige, Catal.
Commun., 2005, 6, 645; (b) D. G. Lahr and B. H. Shanks, J. Catal.,
2
005, 232, 386.
9
J. Chaminand, L. Djakovitch, P. Gallezot, P. Marion, C. Pinel and
C. Rosier, Green Chem., 2004, 6, 359.
1
1
0 (a) S. K. Tyrlik, D. Szerszen, M. Olejnik and W. Danikiewicz, J. Mol.
Catal. A: Chem., 1996, 106, 223; (b) T. Miyazawa, Y. Kusunoki, K.
Kunimori and K. Tomishige, J. Catal., 2006, 240, 213.
Acknowledgements
Financially supported by the Major State Basic Resource Devel-
opment Program (Grant No. 2003CB615807), NSFC (Project
1 (a) T. Hirai, N. Ikenaga, T. Miyake and T. Suzuki, Energy Fuels,
2
005, 19, 1761; (b) J. W. Shabaker, G. W. Huber, R. R. Davda, R. D.
2
0573024), and the Natural Science Foundation of Shanghai
Cortright and J. A. Dumesic, Catal. Lett., 2003, 88, 1.
1
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