Combination of Pd/C and Amberlyst-15 in a single reactor for the acid/hydrogenating catalytic conversion of carbohydrates to 5-hydroxy-2,5- hexanedione

Article abstract of DOI:10.1039/c4gc01158a

Here we show that combination of Pd/C and Amberlyst-15 in a single reactor allowed fructose and inulin to be converted to 5-hydroxy-2-5-hexanedione, a valuable chemical platform, in a one-pot process. the Partner Organisations 2014.

Full text of DOI:10.1039/c4gc01158a

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Combination of Pd/C and Amberlyst-15 in a single
reactor for the acid/hydrogenating catalytic
conversion of carbohydrates to 5-hydroxy-2,5-
hexanedione
Cite this: Green Chem., 2014, 16,
4110
Received 20th June 2014,
Accepted 24th July 2014
Fei liu,a Maïté Audemar,a Karine De Oliveira Vigier,a Jean-Marc Clacens,b
DOI: 10.1039/c4gc01158a
www.rsc.org/greenchem
Floryan De Campob and François Jérôme*a
Here we show that combination of Pd/C and Amberlyst-15 Pt/C solid catalyst in an aqueous solution of oxalic acid (pH =
in a single reactor allowed fructose and inulin to be converted to 2).6 Later on, van Bekkum also pointed out the formation of
5-hydroxy-2-5-hexanedione, a valuable chemical platform, in a HHD when performing the catalytic hydrogenation of HMF in
one-pot process.
an aqueous solution of HCl.7 Although these studies have
opened an access to a novel functionality from HMF, these are
the only two reports in the literature dealing with this reaction.
Even more surprising, to the best of our knowledge, is that no
one attempted the direct conversion of carbohydrate to HHD
although novel and valuable polyols, amino-alcohols or func-
tionalized tetrahydrofurane derivatives could be easily
obtained from this diketone derivative, and all these chemicals
have potential application in the field of surfactants, polymers
and solvents. The reason for this lack of documentation on
HHD (and more generally on diketone derivatives) stems from
the huge difficulty to control the selectivity of this reaction
from HMF or carbohydrates. The production of HHD from
carbohydrates requires the presence of acid and hydrogenating
sites on the same catalyst or reactor. A close control of the rate
of each elementary step is necessary otherwise many side-pro-
ducts can be formed.
The accepted mechanism for this reaction is rather complex
and involves (1) an acid-catalyzed dehydration of hexoses to
HMF followed by (2) hydrogenation of HMF to 2,5-dihydroxy-
methylfurane (DHMF), (3) acid-catalyzed ring-opening of
DHMF to unsaturated diketone derivatives (highly unstable
compound) and finally (4) hydrogenation of the CvC bond
yielding HHD (Scheme 1).6,7
Here, we wish to show that combination of Pd/C and
Amberlyst-15 (acid catalyst) in the same reactor allowed HHD
to be produced in good yields not only from HMF but also
directly from fructose and inulin. In particular, we show that
high selectivity of this reaction is associated with a compro-
mise between the pressure of hydrogen and the amount of
Pd/C and Amberlyst-15.
Production of chemical platforms from biomass has become a
top priority in academia and industry not only to create diver-
sity but also to access chemicals with similar or improved
properties as compared to fossil-derived chemicals.1 In this
context, diketone derivatives appear as an interesting class of
chemical platforms from which valuable derivatives such as
polyols, amines, tetrahydrofuran, lactones, among others
could be produced.
Diketone derivatives can be produced from biomass for
instance by the catalytic oxidation of glycerol2 (and more gene-
rally renewable polyols) or the catalytic conversion of hexoses
to levulinic acid.3 Although of great interest, these routes have
shortcomings hampering their industrial development. For
instance, oxidation of polyols suffers from a lack of selectivity
while the production of levulinic acid requires formic acid,
formed as a co-product, to be chemically valorized.
During the last decade, numerous studies have focused on
the catalytic hydrogenation/hydrogenolysis of furanic deriva-
tives to dimethylfurane or tetrahydrofurane derivatives.4 To
date, only a little attention has been paid to the catalytic con-
version of 5-hydroxymethylfurfural (HMF), a chemical derived
from hexoses, to hexanedione derivatives. Among them, for-
mation of 2,5-hexanedione (HDX) from HMF was reported as a
feasible way but one should note that yields of HDX often
remained low (<10%).5 Interestingly, in 1991, V. Schiavo et al.
reported for the first time that HMF can be converted to
5-hydroxy-2,5-hexanedione (HHD) by hydrogenation over a
aInstitut de Chimie des Milieux et Matériaux de Poitiers, ENSIP, Université de
Poitiers, 1 rue Marcel Doré, 86022 Poitiers, France.
Prior to optimization of catalytic conditions from carbo-
hydrates, experiments were first conducted with HMF. In this
context, we concentrated our efforts on the hydrogenation of
HMF to dihydroxymethylfurane (DHMF) which is the first key
E-mail: francois.jerome@univ-poitiers.fr
bEco-Efficient Products and Processes Laboratory, UMI 3464 CNRS/Solvay, 3966
Jin Du Road, Shanghai 201108, China. E-mail: floryan.decampo@solvay.com
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presence of 10 wt% of water, DHMF was produced nearly as an
exclusive product up to 60% conversion (Table 1, entry 3). No
appreciable effect of water (10 wt%) was however noted on the
reaction rate. The formation of undesirable side products (not
identified) was observed only when the water content reached
20 wt% (Table 1, entry 4). Hence, 10 wt% was considered as a
limit for the water-tolerance of the hydrogenation step. The
pressure of hydrogen obviously plays an important role in the
reaction rate. An increase of the H2 pressure from 50 to 80 and
100 bar improved the reaction rate and the yield of DHMF was
increased from 57% to 66% and 82%, respectively (Table 1,
entries 3, 5, 6). This result may be ascribed to the better
solubility of H2 in the THF–H2O phase when the pressure was
increased.9
Next, Amberlyst-15 (–SO3H = 4.70 mmol g−1) was co-added
to the Pd/C to promote the direct conversion of HMF to HHD
through in situ hydrogenation/hydrolysis of HMF. Amberlyst-15
is a widely used solid acid catalyst in industry and was pre-
ferred here for this reason. Note that water was not added into
Scheme 1 Conversion of fructose to HHD in a dual acid/hydrogenation
catalytic pathway.
intermediate in the production of HHD.6,8 Pd over charcoal the reaction vessel since wet Amberlyst-15 was used. The water
(Pd/C) was selected in our investigations because it is a water- content of the reaction media (THF, HMF, Pd/C and A15) was
tolerant solid catalyst widely used at an industrial level. Toler- determined by Karl Fischer analysis and reached 3.8 wt%
ance to water is a crucial aspect considering that molecules of which is in the range of the water-tolerance defined above for
water will be involved to perform the subsequent hydrolysis the hydrogenation step of HMF to DHMF. Results are summar-
(acid-catalyzed ring opening) of DHMF. Results are presented ized in Table 2. Heating HMF at 80 °C in THF containing
in Table 1.
6.5 wt% of Pd/C and 11 wt% of Amberlyst-15 led to the pro-
Under mild conditions (80 °C) and in neat tetrahydrofurane duction of HHD in 65% yield (Table 2, entry 2). Note that
(THF), HMF was converted to DHMF in 71% yield after 48 h of without Pd/C, no formation of HHD was evidenced further
reaction in the presence of 5 wt% of Pd/C and under 50 bar of supporting the necessity to combine both solid catalysts in the
H2 (Table 1, entry 1). The only detected secondary product was reactor (Table 2, entry 1). Under these conditions, a pressure
2,5-dihydroxymethyltetrahydrofurane (DHMTHF) resulting of hydrogen of 50 bar was found to be optimum. An increase
from the total hydrogenation of HMF. When the temperature or a decrease of the pressure of hydrogen had indeed a dra-
was raised to 120 °C, a mixture of DHMTHF (34%) and DHMF matic effect on the yield of HHD. For instance at 30 bar of
(48%) was obtained suggesting that temperatures higher hydrogen, HHD was produced with only 20% yield (Table 2,
than 80 °C are not favorable for the selectivity of the reaction entry 3) while the carbon mass balance was decreased to only
(Table 1, entry 2). Considering that water will be further 44% due to dominant acid-catalyzed reactions (mainly stem-
involved in the reaction mechanism (hydrolysis of DHMF), ming from the acid-catalyzed polymerization/condensation of
water was progressively added to the reaction medium to the intermediate unsaturated diketone derivative). Similarly,
check its influence on the hydrogenation step of HMF. In the at 80 bar of hydrogen, catalytic reduction of HMF to DHMF
Table 1 Catalytic conversion of HMF to DHMF in the presence of a Pd/C solid catalyst
Entry PH (bar) Solv.
Temp. (°C) Time (h) Conv. (%) DHMF yield (%) DHMTHF yield (%) Carbon mass balancea (%)
2
1
2
3
4
5
6
50
50
50
50
80
THF
THF
THF–H2O (9/1)
THF–H2O (8/2)
THF–H2O (9/1)
THF–H2O (9/1)
80
120
80
80
80
48
20
20
20
20
20
98
100
60
50
75
71
48
57
20
66
82
15
34
2
0
4
86
82
99
70
95
93
100
80
97
8
a The carbon mass balance was measured based on detected/identified products. Others were mostly unidentified polymeric black materials.
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Table 2 Catalytic conversion of HMF to HHD in the presence of Pd/C and Amberlyst-15 solid catalysts
Pd/Ca Amberlyst-15a
Entry (wt%) (wt%)
Time Conv. HHD
DHMF yield DHMTHF yield DMF yield HDX yield Carbon mass
PH (bar) (h)
(%)
yield (%) (%)
(%)
(%)
(%)
balanceb (%)
2
1
2
3
4
5
6
7
8
9
10
0
11
11
11
11
11
11
11
5.5
20
20
50
50
30
80
50
50
30
50
50
50
15
15
15
15
15
15
15
15
10
15
6
100
100
95
—
65
20
43
58
7
30
18
67
77
—
0
0
25
0
0
0
32
0
—
2
0
15
0
10
10
6
—
7
10
0
0
15
9
0
1
0
—
10
14
3
6
6
21
0
7
—
84
44
86
64
38
70
91
75
83
6.5
6.5
6.5
4.0
13.0
13.0
6.5
6.5
5.5
90
100
100
65
100
100
0
0
0
6
a Based on the amount of HMF. b The carbon mass balance was measured based on detected/identified products. Others were mostly
unidentified polymeric black materials.
(25% yield) and DHMTHF (15% yield) was favored and
HMF is commonly produced through an acid-catalyzed
the yield of HHD was decreased to 43% (Table 2, entry 4). triple dehydration of hexoses.10 Extraction of HMF from an
Hence a pressure of hydrogen of 50 bar was selected in our aqueous catalytic phase is not so trivial because (1) HMF is
experiments.
rather unstable and (2) the partition coefficient of HMF
For the same reason, a change of the Pd/C loading between aqueous and organic phases is not very high, thus
obviously dramatically impacted the selectivity to HHD. A requiring multistep extraction. Considering that HMF is only a
decrease of the Pd/C loading from 6.5 wt% to 4 wt% favored reaction intermediate, we then attempted the direct conversion
the acid-catalyzed reactions and lowered both the yield of of fructose to HHD in a single reactor to circumvent the costly
HHD to 58% and the carbon mass balance from 84% to 64% intermediate extraction/purification of HMF. Although of great
(Table 2, entry 5). Reversely, an increase of the Pd/C loading interest from an economical point of view, this reaction is
from 6.5 wt% to 13 wt% favored hydrogenation reactions and, however scientifically relevant and requires the close control of
in this case, a messy mixture of compounds was produced four different steps in a single reactor.
(Table 2, entry 6). Among them, HHD (7% yield), DHMTHF
Inspired by our above described results, a solution of 5 wt%
(10% yield), dimethylfurane (15% yield) and HXD (6% yield) of fructose was heated at 80 °C in THF in the presence of Pd/C
were detected. Note that at such high loading of Pd/C, the (6.5 wt%) and Amberlyst-15 (11 wt%). The pressure of hydro-
yield of HHD can be improved to 30% only by reducing the gen was decreased to 10 bar since at 50 bar reduction of fruc-
pressure of hydrogen from 50 bar to 30 bar (Table 2, entry 7). A tose to hexitol and C–C bond cracking products were observed.
similar trend was of course also observed with the loading of Unfortunately, under these conditions, HHD was produced in
Amberlyst-15. A decrease of the Amberlyst-15 loading from a trace amount. In addition, formation of HMF was not
11 wt% to 5 wt% led to dominant hydrogenation reaction and observed suggesting that fructose was not dehydrated under
thus lowered the yield of HHD to 18% (Table 2, entry 8). Inter- these particular reaction conditions. Hence, the amount of
estingly, an increase of the Amberlyst-15 loading from 11 wt% Amberlyst-15 was increased to 35 wt%. Under these con-
to 20 wt% had however a positive effect on the reaction rate ditions, fructose was converted but the reaction did not
while the yield of HHD (67%) was not affected (Table 2, entry achieve a high HHD selectivity and a complex mixture of com-
9). At such loading of Amberlyst-15, a slight decrease of the pounds was obtained. It should be noted that dehydration of
Pd/C loading from 6.5 wt% to 5.5 wt% allowed HHD to be pro- fructose and an increase of the amount of Amberlyst-15 from
duced with an even higher yield of 77% (Table 2, entry 10). 11 wt% to 35 wt% contribute to increase the water content of
Note that a further decrease of the Pd/C loading to 4 wt% the media and thus may also affect here the selectivity of the
dropped the yield of HHD to 60%.
reaction as suggested in Table 1. Interestingly, addition of
Altogether, these results suggested that a high selectivity of 0.3 wt% of dimethylsulfoxide to the THF led to the complete
HHD in this reaction may require a close control of the conversion of fructose and the formation of HHD in 23% yield
amount of acid and reductive catalytic sites. Pd/C and Amber- together with HDX (6.5% yield) and HMF (45% yield) (Table 3,
lyst-15 loadings of 5.5 wt% and 20 wt%, respectively, were entry 1). An increase of the pressure of hydrogen from 10 to 20
found to be optimum at 80 °C while the pressure of hydrogen bar allowed HHD to be produced in 35% yield (after 15 h of
should be preferentially maintained at 50 bar.
reaction) while the yield of HMF was concomitantly decreased
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Table 3 Direct conversion of carbohydrates to HHD in the dual acid/hydrogenating catalytic system
Pd/Ca
(wt%)
PH
(bar)
Time
(h)
Conv.
(%)
HHD yield
(%)
HMF yield
(%)
LA yield
(%)
HDX yield
(%)
Carbon mass
balanceb (%)
2
Entry
Carbohydrate
1
2
3
4
5
Fructose
Fructose
Fructose
Fructose
Inulin
6.5
6.5
6.5
13
10
20
20
10
35
15
15
20
15
36
95
95
95
95
95
23
35
55
50
27
45
12
0
15
5
5
9
11
2
6.5
7.5
12
11
17
79.5
63.5
82
78
53
13
4
a Based on the amount of carbohydrate. b The carbon mass balance was measured based on detected/identified products. Others were mostly
unidentified polymeric black materials.
to 12% (Table 3, entry 2). At a prolonged reaction time (20 h), natural biopolymer of fructose, was also converted to HHD
no HMF was detected anymore in the reaction media and demonstrating the usefulness of this process. In this dual
HHD was obtained in a maximum yield of 55% (Table 3, entry acid/hydrogenating catalytic pathway, the control of the reac-
3). It should be noted that similar yield of HHD can be tion selectivity is obviously the main key. In particular, the rate
obtained at only 10 bar of hydrogen but, in this case, it was of acid and hydrogenation catalytic steps was controlled by
necessary to use 13 wt% of Pd/C, otherwise acid-catalyzed reac- adjusting the amount of each catalyst and the pressure of
tion could be dominant (Table 3, entry 4).
hydrogen. From an ecological point of view, this work also
At the moment we have no rational explanation for the role gathers few advantages such as (1) 100% carbon atom
of DMSO. It should be however noted that when DMSO economy, (2) the release of only two molecules of water and (3)
was used in a larger amount or as a solvent, HHD was not one-pot process. Although no leaching of catalytic sites was
produced anymore. One may suspect that DMSO helps in evidenced in the reaction media, it should be noted that an
the dissolution of fructose in THF or modifies the surface of important drop in the catalyst activity and selectivity was
palladium by adsorption.
observed during the second run mostly due to the difficulty
Then, inulin, a natural biopolymer of fructose, was tested. to separate insoluble black polymers (side products) from
Results are presented in Table 3. We and others have pre- the suspension of Pd/C-Amberlyst-15 solid catalysts. The
viously showed that inulin can be converted to HMF under deposition of palladium species over an acid solid support,
acidic conditions.11 To our delight, using the conditions the design of a continuous flow process and transposition to
described in Table 3, entry 1, inulin was converted to HHD in other valuable biopolymers are now the topics of current
27% yield (entry 5) showing that this system is capable of cata- investigation.
lyzing in a single reactor (1) the hydrolysis of inulin to fructose
followed by (2) the dehydration of fructose to HMF, (3) the
hydrogenation of HMF to DHMF, (4) the rehydration of DHMF
Experimental section
Chemicals
and (5) hydrogenation to HHD. Considering that HHD was
produced in a one-pot process in 27% yield from inulin, the
average yield of each elementary step is 77%, further demon-
All chemicals were purchased from Sigma-Aldrich. Dry Amber-
strating the selectivity of this catalytic reaction. The low carbon
lyst-15 was kindly provided by Rohm & Hass. The sulfonic
mass balance observed in the case of inulin (53%) was mostly
loading of dry Amberlyst-15 is 4.70 mmol g−1. Pd/C was pur-
due to the side formation of unidentified soluble and insolu-
chased from Sigma-Aldrich. It contains 5 wt% of Pd. The Pd/C
ble black materials.
has a surface area of 832 m2 g−1, an average pore size of 19.5 Å
and the particle sizes are within the range of 1–60 nm.
Conclusions
Analytical methods
In conclusion, we report in this communication that combi- Gas chromatography analyses were performed on a Bruker
nation of two widely used solid catalysts such as Pd/C and GC-456 equipped with a column injector (250 °C), an FID
Amberlyst-15 in a single reactor allowed fructose to be con- detector (325 °C) and an HP-5 ms column (30 m × 0.25 mm ×
verted to HHD in 55% yield opening a direct route to a 0.25 μm). NMR spectra were recorded on BRUKER ADVANCE
1
chemical platform exhibiting great potential in the field of DPX 400 spectrometers at 400.13 MHz for H and 100.6 MHz
surfactants, monomers and solvents. In addition, inulin, a for 13C. Data for HHD, DMF, HDX, HMF, LA, DHMF and
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DHMTHF are already described in the existing literature and
were used to ascertain the formation of targeted products.
Acknowledgements
The authors are grateful to the CNRS, the French Ministry of
Research and SOLVAY for the financial support. FL also thanks
SOLVAY for the funding of her postdoctoral position.
Selected data for HHD
1H NMR (400 MHz, CDCl3, ppm): 2.16 (s, 3H, –CH3), 2.59 (t, J =
6.4 Hz, 2H, –CH2), 2.80 (t, J = 6.4 Hz, 2H, –CH2), 3.12 (bs, 1H,
–OH), 4.29 (s, 2H, –CH2); 13C NMR (100 MHz, CDCl3, ppm):
29.7 (–CH3), 31.7 (–CH2), 36.8 (–CH2), 68.2 (–CH2OH); LC/MS
(ESI), m/z = 132.1 uma.
Notes and references
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Procedure for the hydrogenation of HMF to DHMF and
DHMTHF
To a mixture of THF (5 mL, may contain a maximum of 0.5 mL
of water) and HMF (150 mg, 1.19 mmol) was added Pd/C
(8 mg, 0.0038 mmol, i.e. 5 wt% relative to HMF). The solution
was then placed inside the autoclave and flushed with H2.
Next, the reactor was heated at 80 °C under a pressure of H2
(50–100 bar, see Table 1) for 20 hours. After this period, the
reactor was cooled down to room temperature, vented and
opened. A syringe filter was used to remove the catalyst from
the reaction mixture, and the recovered solution was then ana-
lyzed by GC.
3 For a recent review see: J. Zhang, S. B. Wu, B. Li and
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Procedure for the hydrogenation of HMF to HHD
To a mixture of THF (5.6 mL), A15 (30 mg) and HMF (150 mg,
1.19 mmol) was added Pd/C (9.7 mg). The solution was placed
inside an autoclave and was flushed with H2. Next, the reactor
was heated at 80 °C under a pressure of H2 (preferentially 50
bar) for 10 hours. See Table 2 for the optimal experimental
parameters. After this period, the reactor was cooled down to
room temperature, vented and opened. A syringe filter was
used to remove the catalyst from the reaction mixture, and the
recovered solution was then analyzed by GC.
6 V. Schiavo, G. Descotes and J. Mentech, Bull. Soc. Chim. Fr.,
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Procedure for the hydrogenation of fructose to HHD
To a mixture of THF (5.6 mL), DMSO (0.01 mL), A15 (87 mg),
and fructose (250 mg, 1.39 mmol) was added Pd/C (16.3 mg).
The solution was then placed in an autoclave and flushed with
H2. Next, the reactor was heated to 80 °C under a pressure of
H2 of 20 bar. The reaction was stirred under these conditions
for 20 hours. After this period, the reactor was cooled down,
vented and opened. A syringe filter was used to remove the
catalyst from the reaction mixture, and the recovered solution
was then analyzed by GC.
9 E. Brunner, Chem. Eng. Data, 1985, 30(3), 269–273.
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Procedure for the hydrogenation of inulin to HHD
The procedure was similar to the one used for fructose except
that the amount of Pd/C and the pressure of hydrogen were
fixed at 32.6 mg and 35 bar, respectively. The reaction time
was also increased to 36 h in the case of inulin.
4114 | Green Chem., 2014, 16, 4110–4114
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