Selective oxidation of 5-hydroxymethylfurfural into 2,5-diformylfuran over VPO catalysts under atmospheric pressure

Article abstract of DOI:10.1039/c9ra02213a

Vanadium phosphate oxide (VPO) heterogeneous catalysts with different V/P molar ratios were prepared and used for selective oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to produce 2,5-diformylfuran (DFF) in the liquid phase. It was found that the VPO catalyst with V/P molar ratio 0.25 exhibited the best catalytic performance. Then the VPO catalyst was utilized to catalyze the oxidation of HMF in a batch reactor under different conditions, in terms of type of solvent (water and organic), reaction time and temperature. A high DFF yield of 83.6% with HMF conversion of 100% was obtained under atmospheric pressure.

Full text of DOI:10.1039/c9ra02213a

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Selective oxidation of 5-hydroxymethylfurfural into
2,5-diformylfuran over VPO catalysts under
Cite this: RSC Adv., 2019, 9, 14242
atmospheric pressure†
a
a
ab
Du Zhang, Xianxiang Liu, *a
a
Jinhua Lai, ‡ Kai Liu,‡ Shuolin Zhou,
a
a
Qiong Xu and Dulin Yin
Vanadium phosphate oxide (VPO) heterogeneous catalysts with different V/P molar ratios were prepared and
used for selective oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to produce 2,5-diformylfuran
Received 22nd March 2019
Accepted 2nd May 2019
(DFF) in the liquid phase. It was found that the VPO catalyst with V/P molar ratio 0.25 exhibited the best catalytic
performance. Then the VPO catalyst was utilized to catalyze the oxidation of HMF in a batch reactor under
different conditions, in terms of type of solvent (water and organic), reaction time and temperature. A high
DFF yield of 83.6% with HMF conversion of 100% was obtained under atmospheric pressure.
DOI: 10.1039/c9ra02213a
rsc.li/rsc-advances
challenging subject. To date, there are plenty of catalysts
employed in selective oxidation of HMF into DFF, such as the
Introduction
6
–8
9
In recent years, the high value-added chemicals and fuels manganese oxide-based material,
GO-related materials,
10–12
13–16
prepared from renewable natural biomass resources have supported Ru catalysts
and vanadium-based catalysts.
1–3
17–19
captured intense interest, coined “biorenery”. Among them, Zhang et al.
have been committed to research in this area
the dehydration of C6 based carbohydrates can generate an and developed a series of catalysts with excellent catalytic
important platform chemical 5-hydroxymethylfurfural (HMF), activity. Due to the high price of noble metal, developing cheap
which is considered to be one of the top value-added chemicals. transition metal-based heterogeneous catalysts for the
2
,5-Diformylfuran (DFF) is one of the main products of HMF synthesis of DFF from the selective oxidation of HMF is thus
oxidation, and has been used as a starting material for the highly desirable. Among these catalysts, vanadium-containing
synthesis of ligands, drugs, pesticide antifungal agents, uo- catalysts are noticeable. In the past decade, some methods on
4,5
rescent materials and new polymeric materials.
the aerobic oxidation of alcohols using relatively cheap V based
However, as shown in Scheme 1, the HMF structure contains catalysts were reported. Inspired by the excellent catalytic
a hydroxyl and a formyl moiety together with a furan ring, activity of VPO catalysts in the oxidation of alcohols, herein, we
opening an avenue for chemical reactions. Therefore, the prepared a series of VPO catalysts with different V/P molar ratios
oxidation of HMF makes it susceptible to undergo many side by using the liquid phase method, and used as a novel hetero-
reactions such as over oxidation of DFF into 2,5-fur- geneous catalyst for the selective oxidation of HMF into DFF.
andicarboxylic acid (FDCA), the oxidation of aldehyde to 5-
hydroxymethyl-2-furancarboxylic acid (HMFCA), decarbon-
ylation, and cross-polymerization to produce unwanted Experimental
byproducts. Therefore, it is still a challenge to selectively oxidize
HMF into DFF.
How to achieve selective oxidation of HMF to prepare DFF
under mild conditions, it has always been an important and
Materials
5-Hydroxymethylfurfural (99.5%) and 2,5-diformylfuran were
purchased from Sinopharm Chemical Reagent Co., Ltd.
a
National & Local Joint Engineering Laboratory for New Petro-chemical Materials and
Fine Utilization of Resources, Key Laboratory of the Assembly and Application of
Organic Functional Molecules of Hunan Province, College of Chemistry and
Chemical Engineering, Hunan Normal University, Changsha 410081, PR China.
E-mail: lxx@hunnu.edu.cn; Fax: +86 731 88872531; Tel: +86 731 88872576
b
Junior Education Department, Changsha Normal University, Changsha 410100, PR
China
†
1
‡
Electronic supplementary information (ESI) available. See DOI:
0.1039/c9ra02213a
These authors contributed equally.
Scheme 1 Possible oxidation products from the oxidation of HMF.
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4 3 3 4
(Shanghai, China). NH VO and H PO were purchased from
Sinopharm Chemical Reagent Co., Ltd (Shanghai China). All the
chemicals were of analytical grade and used without further
purication. Ultrapure water was used for the catalyst prepa-
ration and catalytic reactions.
Preparation of catalyst
Vanadium phosphate oxide (VPO) was prepared according to
the following procedure. V
2
O
5
(1.4 g), derived from the pyrolysis
ꢀ
of NH VO at 180 C, and H PO (85%, 7 g) were reuxed in
4
3
3
4
ꢀ
isobutanol (25 mL) at 120 C for 12 h. The resulting solid was
isolated by vacuum ltration, washed with isobutanol, and
ꢀ
dried under vacuum at 80 C. Powder X-ray pattern of the solid
2 4 2
prasinous product corresponded to that found for VO(H PO ) .
Fig. 1 XRD patterns of VPO.
Synthesis of DFF from HMF
successfully synthesized. However, the VPO catalyst demon-
The oxidation of HMF in the air under atmospheric pressure
was performed in a 25 mL round bottom ask, which was
coupled with a reux condenser using the following general
procedure. Typically, HMF (0.1 mmol, 12.6 mg) was rstly dis-
solved into DMSO (5 mL) in the ask with a magnetic stirrer.
Then, 10 mg VPO catalysts were added into the reaction
mixture. The mixture was heated to the desired temperature
while stirring under an air atmosphere. Aer reaction, the
reaction solution was quantitatively analyzed by HPLC.
According to test results, the oxidation of HMF mainly leads to
DFF, HMFCA, 5-formyl-2-furancarboxylic (FFCA) and FDCA.
ꢀ
strated the largely enhance (002) and (121) facet signal at 22.38
ꢀ
and 24.96 .
Fig. 2 showed TEM images of VPO catalyst at different
magnications. The TEM observation in Fig. 2a veried
a nanosheet structure of VPO covered by a different phase
(
Fig. 2b). This new phase seems to be a lm forming some
aggregates or clusters (Fig. 2c and d) on the nanosheets. From
the Fig. 2, it can be clearly distinguished the aggregates with
multiple grains of different sizes. In agreement with XRD, this
dispersed phase seems to be a mixture of VPO mixed-oxide
2
0,21
species.
The thermogravimetric analysis for VPO sample carried out
in nitrogen ow. It can be seen from the Fig. 3 that the VPO
Quantication of the products
The product analysis was performed using Agilent 1100 HPLC catalyst has three weight loss stages. Firstly, around 5% of
ꢀ
system equipped with Agela Technologies Venusil XBP C18(L) mass loss at temperatures lower than 150 C, due to the loss of
(
4.6 ꢁ 250 mm) and a UV-Vis (280 nm) detector. The mobile absorbed water; second, the mass loss lower than 5% at
ꢀ
phase was constituted of acetonitrile and 0.1 wt% acetic acid temperatures range at 150–250 C, due to the loss of crystal
ꢀ
aqueous solution (v : v ¼ 15 : 85), and the samples was eluted at water; then, a at region up to 300 C; and then it starts to be
ꢂ1
ꢀ
2
2
a rate of 0.5 mL min at 30 C. The amount of each compound decomposed into VO(PO ) . Thus, this catalyst can be used
3
2
ꢀ
was quantied by external standard calibration curve method. under oxidizing conditions up to 300 C. As expected, the VPO
To calculate HMF conversion, DFF selectivity and yield are catalyst prole only presents a mass loss at low temperature
dened as follow:
HMF conversion ¼ (1 ꢂ moles of HMF/moles of HMF added) ꢁ
1
00%
DFF selectivity ¼ moles of DFF/(moles of HMF added ꢂ moles
of HMF) ꢁ 100%
DFF yield ¼ moles of DFF/moles of HMF added ꢁ 100%
Results and discussion
Catalyst characterization
The VPO catalyst was characterized using XRD, TEM, TG-DTG,
Raman and FI-IR analysis. The XRD pattern in Fig. 1 illus-
trated the VO(H
2 4 2
PO ) crystal structure with JCPDS card 40-0038
for the VPO catalyst, demonstrating that this phase has been Fig. 2 TEM images of VPO catalysts.
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Fig. 3 TG-DTG curves of VPO.
2 5
Fig. 5 Raman spectra of VPO and different V O .
due to absorbed water and then it does not present a weight
loss when the temperature increased.
2 5
V O . In agreement with FT-IR, it is characteristic of V–OH.
The FT-IR spectra of different V
catalyst with different V/P molar ratios were analyzed (Fig. 4).
The FT-IR spectra of different V illustrated the typical V
crystal structure for both the commercial bulk V O and the
2 5
O and a series of the VPO
There is no V
2
O
5
Raman bands in Raman spectrum of VPO,
ꢂ1
and Raman bands near 1034 cm redshis upon hydration
2
O
5
2 5
O
2
4,25
and it is characteristic of the V]O bond stretching mode,
conrming the presence of dispersed vanadium oxide species
VO ) and well dispersed. The intense Raman band at
940 cm has been assigned to VO(H
and FT-IR result. Thus, the VO(H PO
2
5
V O derived from the pyrolysis of NH VO . However, the V]O
2
5
4
3
(
X
of the V O , derived from the pyrolysis of NH VO , demon-
2
5
4
3
ꢂ1
ꢂ1
26
PO
)
,
same as XRD
2
2
4
2
strated the smaller wave number (below 1000 cm ). And the
ꢂ1
2
4
)
is certainly achieved.
adsorption peaks appearing at around 3200 cm
and
ꢂ1
1
400 cm correspond to the N–H. For four curve of VPO, with
the increase of V
absorption intensity of V]O (below 1000 cm ) increases
2
O
5
content in VPO, the characteristic
Effect of V/P molar ratios on the selective oxidation of HMF
ꢂ1
The catalytic activity of the as-prepared VPO catalysts with
continuously, and the vibration absorption intensity of two
ꢂ1
different V/P molar ratios was evaluated by the oxidation of
PO groups (1000–1300 cm ) decreases, which differ by the
3
2
3
ꢂ1
HMF in DMSO under atmospheric air pressure at 120 C. Fig. 6
ꢀ
type of symmetry. The broad peaks around 3600 cm and
640 cm are attributed to the stretching and bending modes
ꢂ1
depicted the results of HMF conversion and products selectivity
using various VPO catalysts. HMF conversion and selectivity of
DFF were all changed greatly with the increase of vanadium
content in the VPO catalysts. When V/P molar ratio of the VPO
catalyst was 4, the HMF was fully transformed, but the selec-
tivity and yield of the DFF were relatively low. This implies an
increase in the V/P ratio can maintain the oxidation properties
of VPO catalyst and increases in turn the formation of side
1
of the O–H of surface hydroxyl groups and physically adsorbed
ꢂ1
water. The peak at 3420 cm arises from the O–H stretching
vibration of V–O–H.
The Raman spectra of different V
illustrated the V O crystal structure. However, the V O
2 5
2 5
O samples in Fig. 5
2
5
derived from the pyrolysis of NH VO gave a new intense
4
3
ꢂ1
Raman band at 964 cm compared with the commercial bulk
27,28
products, the lower DFF selectivity accordingly.
In addition,
Fig. 6 The results of HMF oxidation over the VPO catalysts with
different V/P molar ratios under atmospheric pressure. Reaction
ꢀ
Fig. 4 FT-IR spectra of different V
with different V/P molar ratios.
2
O
5
and a series of the VPO catalysts conditions: 0.1 mmol HMF, 10 mg catalyst, 5 mL DMSO, 120 C, 10 h, in
the air.
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V
2
O
5
was also active for HMF oxidation with conversion of
89.5% under the same reaction conditions, yet with the lower
selectivity toward DFF of 69.7%, since further oxidation to form
FFCA (10.2%) and FDCA (9.9%) easily occurred. While the VPO
catalyst with V/P molar ratio 0.25, HMF was almost quantita-
tively converted, and the selectivity of DFF reached the
maximum 75.0%. This enlightens that the VPO catalyst exhibits
excellent catalytic activity at room pressure, compared to 5%
29
conversion in the previous work. Therefore, all subsequent
experiments used of the VPO catalyst with V/P molar ratio 0.25.
Effect of solvents on the selective oxidation of HMF
The selective oxidation of HMF was further carried out in
a variety of solvents. As shown in Table 1, the solvent showed
a remarkable effect on the oxidation of HMF. DMSO with high VPO, 10 mL DMSO, 120 C, in the air.
polarity and high boiling point was found to be the best solvent.
Fig. 7 Time courses of HMF oxidation over the VPO catalysts under
atmospheric pressure. Reaction conditions: 0.15 mmol HMF, 10 mg
ꢀ
HMF completely converted and the selectivity of DFF reached
83.6% when using DMSO as the solvent (Table 1 Entry 5).
Moderate HMF conversions around 30–40% were obtained in
MIBK and DMF, as much more DFF was further oxidized into
FDCA. The selectivity of DFF in DMF was the lowest of all testing
organic solvent. Reaction carried in toluene and water produced
30
low HMF conversion (Table 1 Entry 1 and Entry 2). Yang et al.
also reported that polar solvent like DMSO shows better HMF
conversion and DFF selectivity as compared to non-polar
solvent such as toluene. Hence, further study was done by
taking DMSO as solvent for the selective oxidation of HMF into
DFF.
Effect of time on the selective oxidation of HMF
Fig. 7 showed time course for each product in the VPO-catalyzed
oxidation of HMF to DFF. As shown in Fig. 7, the oxidation of
HMF was very fast, and then slowed down. The fast reaction rate
in the initial stage should be due to the high concentration of
Fig. 8 The results of HMF oxidation over the VPO catalysts at different
reaction temperatures under atmospheric pressure. Reaction condi-
tions: 0.1 mmol HMF, 10 mg VPO, 5 mL DMSO, 10 h, in the air.
31
HMF at an early reaction stage. HMF was fully converted aer
0 h, and DFF was obtained in a highest yield of 83.2%. FDCA
1
was obtained in a highest yield of 12.0% at 2 h, and the yield of Effect of reaction temperature on the selective oxidation of
FFCA increased slowly and reached 5.4%. HMFCA was not HMF
detected during this reaction. It is therefore expected that HMF
is oxidized into DFF, and that FDCA formed though FFCA
derived from DFF.
The effect of the reaction temperature was also studied and the
results are shown in Fig. 8. HMF conversion and DFF yield
increased with the increase of reaction temperature between
ꢀ
ꢀ
9
0 C and 110 C. HMF conversion was obtained in 25.4% when
the reaction was carried out at the reaction temperature of
a
Table 1 Effect of solvents on the selective oxidation of HMF into DFF
ꢀ
ꢀ
9
0 C. Furthering increasing the reaction temperature to 110 C,
HMF conversion increased to 98.3% aer 10 h. These results
DFF yield indicated that high reaction temperature promoted the selec-
Selectivity (%)
HMF conversion
(%)
Entry Solvent
FDCA FFCA DFF (%)
tive oxidation of HMF into DFF. Quantitative HMF conversion
ꢀ
was reached when the reaction was carried out at 120 C and
1
2
3
4
5
H
2
O
22.0
15.0
43.1
30.5
100
—
—
28.9
27.4
9.2
—
—
25.8
—
6.1
—
—
ꢀ
1
30 C. As far as the products yield, the yield of DFF was also
Toluene
MIBK
DMF
100 15.0
45.2 19.5
37.1 11.3
83.6 83.6
greatly affected by the reaction temperature. The yield of DFF
gradually increased with the increase of the reaction tempera-
ꢀ
DMSO
ture. The highest yield of DFF was obtained in 83.6% at 120 C
ꢀ
and it slightly decreased to 71.7% at 130 C.
a
ꢀ
Reaction condition: 0.1 mmol HMF, 10 mg VPO, 5 mL solvent, 120 C,
0 h, in the air.
1
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1
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