Application of vanadyl hydrogen phosphate/KIT-6 composites as a catalyst for dehydration of sucrose

Article abstract of DOI:10.1007/s13738-021-02191-2

In this research work, the synthesis of well-ordered mesoporous structure KIT-6 silica-supported vanadyl hydrogen phosphate hemihydrate (VHP/KIT-6) catalysts possessing varying surface area was carried out, followed by being utilized in the dehydration of sucrose to 5-hydroxymethylfurfural (5-HMF) as a solid acid catalyst. The fabrication of two different VHP/KIT-6 catalysts was conducted using the impregnation approach through V₂O₅ reduction in alcoholic media. Then, the catalytic behavior presented by the prepared VHP/KIT-6 samples was compared with unsupported VHP and unsupported vanadyl pyrophosphate (VPP), which was prepared through the calcination of VHP precursor at 400?°C for 24?h. The prepared catalysts were characterized by different analyses, including ICP-OES, BET, XRD, NH₃-TPD analysis, FT-IR spectroscopy, as well as SEM and TEM techniques. Furthermore, important parameters, including the catalyst type and weight, sucrose amount, time, temperature, and the type of solvent on sucrose dehydration, were also studied. It was observed that the highest catalytic activity in the dehydration reaction (5-HMF yield: 67%, sucrose conversion: > 94%) could be provided by the catalyst possessing the highest surface area. Moreover, the catalyst reusability was examined for consecutive four times, based on which no considerable change in the catalytic activity was observed.

Full text of DOI:10.1007/s13738-021-02191-2

Journal of the Iranian Chemical Society
https://doi.org/10.1007/s13738-021-02191-2
ORIGINAL PAPER
Application of vanadyl hydrogen phosphate/KIT‑6 composites
as a catalyst for dehydration of sucrose
1
1
1
1
Jaleh Najaf Sarpiri · Alireza Najaf Chermahini · Mohammad Saraji · Ali Shahvar
Received: 26 October 2020 / Accepted: 21 January 2021
©
Iranian Chemical Society 2021
Abstract
In this research work, the synthesis of well-ordered mesoporous structure KIT-6 silica-supported vanadyl hydrogen phos-
phate hemihydrate (VHP/KIT-6) catalysts possessing varying surface area was carried out, followed by being utilized in
the dehydration of sucrose to 5-hydroxymethylfurfural (5-HMF) as a solid acid catalyst. The fabrication of two diꢀerent
VHP/KIT-6 catalysts was conducted using the impregnation approach through V O reduction in alcoholic media. Then, the
2
5
catalytic behavior presented by the prepared VHP/KIT-6 samples was compared with unsupported VHP and unsupported
vanadyl pyrophosphate (VPP), which was prepared through the calcination of VHP precursor at 400 °C for 24 h. The prepared
catalysts were characterized by diꢀerent analyses, including ICP-OES, BET, XRD, NH -TPD analysis, FT-IR spectroscopy,
3
as well as SEM and TEM techniques. Furthermore, important parameters, including the catalyst type and weight, sucrose
amount, time, temperature, and the type of solvent on sucrose dehydration, were also studied. It was observed that the high-
est catalytic activity in the dehydration reaction (5-HMF yield: 67%, sucrose conversion:>94%) could be provided by the
catalyst possessing the highest surface area. Moreover, the catalyst reusability was examined for consecutive four times,
based on which no considerable change in the catalytic activity was observed.
Keywords Mesoporous KIT-6 silica · Vanadyl hydrogen phosphate hemihydrate catalyst · Sucrose dehydration ·
5
-hydroxymethylfurfural · Biomass conversion
Introduction
e.g., construction, textile, packaging, cosmetics, health, and
food as an essential building block in numerous ꢁelds such
as (1) eꢀective natural ingredient in healthy foods [8–10];
(2) precursor of furan-2,5-dicarboxylic acid and its poly-
mer polyethylene furanoate [11–13]; and (3) formaldehyde
replacement in adhesives and resins [14–16]. Dehydration of
numerous C6 carbohydrates, including monomeric and poly-
meric ones, e.g., sucrose, glucose, maltose, fructose, cellu-
lose, starch, and inulin, can be utilized as an eꢂcient method
for the synthesis of 5-HMF, among which sucrose, the most
abundant one [17], can be the more appropriate choice to
produce 5-HMF industrially. One D-glucose and one D-fruc-
tose are the components composing sucrose disaccharide.
It is noteworthy that, before dehydration, di- and polysac-
charides must be hydrolyzed into the related monosaccha-
rides. Besides, the ꢁrst step isomerization of fructose must
be carried out for glucose monomers. Therefore, hydrolysis,
isomerization and dehydration are the reactions, which make
up the reaction mechanism, which has proved complicated
because of degradation of 5-HMF to formic and levulinic
acid or polymeric species, known as humins.
Over the past decades, ꢁnding alternative chemicals and
energy sources has become the center of attention as a
result of depletion in fossil resources. It seems that biomass
as a source of renewable energy can be considered appeal-
ing for several reasons, the most important of which are its
abundance and inexpensiveness. Biomass is provided by
numerous sources, including wastes of wood, animal, farm,
forestry, agriculture, and industry. Biomass-derived carbohy-
drates can be converted to diꢀerent chemical platforms [1–3]
and used in the catalysis [4–6]. 5-Hydroxymethylfurfural
is considered as one of the most critical bio-based product
opportunities from carbohydrates, as one of the top ten mate-
rials with the most valuable platform chemicals [7]. 5-HMF
possesses numerous applications in diꢀerent industries,
*
Alireza Najaꢁ Chermahini
anajaꢁ@iut.ac.ir; najafy@gmail.com
1
Department of Chemistry, Isfahan University of Technology,
8
4154-83111 Isfahan, Iran
Vol.:(0
1
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Journal of the Iranian Chemical Society
Today, catalytic dehydration of sucrose to 5-HMF is the
subject of numerous investigations. For instance, Jain et al.
made use of zirconium phosphate (ZrP) as a catalyst to syn-
thesize 5-HMF from sucrose, carried out in a sealed reac-
enhancement in the insertion or diꢀusion of species into the
KIT-6 interior [52]. Herein, we decide to ꢁrstly graft VPO
materials onto high surface area mesoporous silica KIT-6
(impregnation technique) and then study the eꢀect of the
type and amount of acid sites of diꢀerent loadings of VPOs
onto KIT-6 in the conversion of sucrose to 5-HMF. Besides,
the eꢀects of various experimental parameters, including
reaction type and dosage of the catalyst, temperature, time,
type of solvent, reusability, and carbohydrates amount and
type, have been investigated in this research to achieve the
signiꢁcant catalytic behavior.
tor, which resulted in a 52% 5-HMF yield in H O–diglyme
2
[
18]. In another study, Marullo et al. utilized HY zeolite
in imidazolium-based IL mixtures to dehydrate sucrose to
5
5
-HMF, carried out at 120 °C for 3 h, which led to a 62%
-HMF yield [19]. Li et al. also reported the dehydration
of sucrose to 5-HMF by using yeast-derived carbonaceous
microspheres in the ionic liquid of 1-butyl-3-methylimida-
zolium chloride, through which a 44.8% 5-HMF yield could
be provided [20]. Numerous investigations have also been
reported in aqueous media with ZnCl [21], CrCl [22] and
Experimental
2
3
WCl [23] catalysts. Nevertheless, all the above-mentioned
3
catalytic systems suꢀer from a variety of demerits including
corrosion, the use of toxic solvents, the harmful eꢀects of
chromium ion on the environment, high costs, diꢂcult reus-
ability in the utilization of mineral acids along with costly
multi-step synthesis procedure of ionic liquids [24].
Materials
V O , PEG-6000 (Riedel–de Haen), and H PO (Merck
2
5
3
4
Co., 85%) were utilized for the fabrication of VHP. Triblock
copolymer P123 (EO PO EO , M=5800, Aldrich Co.),
2
0
70
20
Vanadium phosphate oxide (VPO) catalyst, a layered
material, in addition to oxidation [25, 26] and desulfuriza-
tion [27] catalysis, has also attracted a great amount of atten-
tion in some solid acid-catalyzed reactions, including acetic
acid esteriꢁcation [28] and dehydration of glycerol [29, 30],
fructose [31, 32], glucose [33, 34] and xylose [35]. Vanadyl
hydrogen phosphate hemihydrate VOHPO .0.5H O (VHP),
tetraethylorthosilicate (TEOS>98%, Dae-Jung, S Korea.)
and n-butanol (Merck Co.) were employed for the prepara-
tion of the mesoporous silica KIT-6. Merck Co. supplied
glucose, fructose, maltose and sucrose for the dehydration
process. All the solvents utilized for the dehydration reaction
(DMSO, THF and NMP) were also purchased from Dae-
Jung, S Korea. The reagents were utilized as received with
no puriꢁcation.
4
2
with Brønsted and Lewis acid sites, has been employed in the
catalytic dehydration of carbohydrates [33, 35, 36], which
has proved outstanding to be adopted as a catalyst for dehy-
dration of carbohydrates to 5-HMF. Kamiya et al. reported
the study of both Lewis and Brønsted acid behavior of acti-
vated VPO catalysts [37]. They found out that VPO acidic
properties were mostly dependent on its preparation strat-
egy, indicating that an organic medium could be much more
appropriate when compared to an aqueous one. In another
study, Feng et al. reported the fabrication of three types of
VPO catalysts, carried out in mixed iso-butyl and benzyl
alcohols, single benzyl alcohol and the presence or absence
of polyethylene glycol-6000 [38]. They indicated that VPO
in the presence of PEG-6000 and mixed iso-butyl and benzyl
alcohols were capable of providing higher acidic properties.
Wang et al. investigated the catalytic performance of VHP
and VPP in glycerol dehydration and reported that VHP is
more active than VPP in the reaction [36].
Characterizations
The FT-IR analysis was carried out with potassium bromide
(KBr) disks by using a Bruker Tensor 27 Fourier transform
infrared spectrometer. Energy‐dispersive X‐ray spectroscopy
was employed as an spot elemental analysis to evaluate the
composition of the optimum catalyst. ICP-OES analysis was
utilized to study the elemental analysis, done by using an
inductively coupled plasma optical emission spectroscopic
(ICP-OES, 5300DV, PerkinElmer). The crystalline structure
of the prepared catalysts was conducted by X-ray diꢀrac-
tion (XRD) analysis, an Asenware XDM-300 diꢀractom-
eter, using Ni-ꢁltered Cu Kα radiation (λ=1.54 Å), and the
results were studied concerning the ICDD database by using
XPert High score v0.3 software. Field emission scanning
electron microscopy (FESEM), FEI Quanta 450 microscope,
and transmission electron microscopy (TEM), a Philips EM
208S instrument, were both utilized to perform the mor-
phological studies on the optimum catalyst. The nitrogen
adsorption/desorption isotherms were employed at 77.0 K
on a BELSORP MINI II to determine the textural param-
eters of the prepared catalysts, which had been outgassed at
Nanoporous materials can be applied with other func-
tional groups to increase their performance by balancing
hydrophobicity, acidity and basicity [39–45]. Most nano-
particles are usually formed inside channels that the porous
supports prevent them from agglomeration [46]. The KIT-6
mesopores, with tridimensional symmetric cubic structure
Ia3d and a bicontinuous interpenetrating network [47–51],
supplied direct access to the active sites, leading to an
120 °C for 2 h before the analysis. For NH -TPD measure-
3
ments, a Nanosord NS91 (Sensiran Co., Iran) apparatus was
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Journal of the Iranian Chemical Society
utilized to perform the temperature-programmed desorption
a mixture of ethanol/HCl, followed by calcination at 550 °C
for 6 h.
with NH . To eliminate not only the adsorbed moisture but
3
also impurities, all the prepared catalysts (0.05 g) were
degassed in a ꢃow rate of 10 mL/min He, which was car-
ried out at 300 °C for 1 h before the analysis. Subsequently,
Synthesis of VPO/KIT‑6 catalysts
the prepared catalysts were saturated with 5% NH /He at
The synthesis of the VPO catalysts was also carried out
according to the literature, as reported previously [54].
Vanadium pentoxide (0.5 g) was ꢁrst dissolved in a mixture
of benzyl alcohol and 2-butanol (in a ratio of 1:1) as the
reducing agent, followed by being reꢃuxed at 140 °C for
5 h under stirring in order to reduce vanadium ions. Sub-
sequently, PEG-6000 (0.15 g) and KIT-6 (0.25 and 0.50 g)
were added to the prepared mixture. One hour later, the
dropwise addition of H PO (85%, 0.45 mL) was carried
3
1
10 °C for 0.5 h. Afterward, to eliminate physisorbed ammo-
nia, the catalysts were purged in a He stream at 110 °C for
0 min, followed by being heated from room temperature
3
to 800 °C at a heating rate of 10 °C/min. The conversion of
carbohydrates was evaluated via a high-performance liquid
chromatography (HPLC) instrument, which was equipped
with a refractive index detector (RID 6A, Shimadzu Cor-
poration), and a Hector-M NH column (150 mm×3.9 mm
2
3
4
i.d., 3 µm; RStech Co., Dae-Jong, Korea) attached to a C18
guard column. The 5-HMF yield was also analyzed by using
an L-3000 RIGOL instrument (Beijing, China) which was
equipped with a UV–Vis detector and a PerfectSil Target
ODS-3 column (150 mm×4.6 mm i.d., 5 µm, MZ-Analysen-
technik GmbH, Germany) connected to a C18 guard column
out to attain a P/V atomic ratio of 1.2, followed by being
reꢃuxed for 6 h. The prepared mixture was ꢁltrated, washed
and dried at 120 °C overnight until a gray-blue precipitate
(VHP/KIT-6) was obtained. The VHP/KIT-6 s contain-
ing 0.25 and 0.50 g KIT-6 were labeled as VK2 and VK1,
respectively, according to the V O /KIT-6 weight ratio. In
2
5
(
10 mm×4 mm i.d., 5 µm). A solution containing water and
comparison, the VHP phase without KIT-6 support was also
synthesized and calcined so that the VPP phase could be
prepared. Here, VHP and VPP materials are labeled as VH
and VP, respectively.
methanol (90:10 v/v) was utilized as the mobile phase at a
ꢃow rate of 1 mL/min, and the detection was performed at
2
84 nm.
Catalysts synthesis
Catalytic activity studies
Synthesis of silica KIT‑6
All the catalytic experiments were performed in a reꢃux
system, sand-bath and under stirring. The above system was
loaded with sucrose (150–300 mg), catalyst (5–20 mg) and
solvent (4 mL) at speciꢁed temperatures and times. At the
end of the reaction, the mixture was centrifuged so that the
catalyst could be isolated, followed by being diluted and
analyzed by using an HPLC instrument. The reaction path-
way for the dehydration of sucrose is depicted in Scheme 1.
Additionally, the carbohydrate conversion and 5-HMF yield
were calculated as follows:
The mesoporous silica KIT-6 was prepared according to the
method reported by Kleitz et al. [53]. Brieꢃy, 4 g of poly
(
(
ethylene glycol)-block-poly (propylene glycol)-block-poly
ethylene glycol) (P123) was ꢁrst dissolved in an aqueous
solution containing 144 mL of deionized water and 9.9 g of
3
5 wt % HCl, followed by the addition of 4 g of n-butanol
at 35 °C. After the 1 h stirring, TEOS (6.8 g) was added at
once and stirred at 35 °C for 24 h. Subsequently, the mixture
was transferred to a glass bottle with a polypropylene lid
Conversion of carbohydrate% = (Initial carbohydrate − Unreacted carbohydrate)∕Initial carbohydrate × 100
and heated at 100 °C for 24 h (hydrothermal treatment). The
mixture was dried and ꢁltrated at 100 °C overnight. Finally,
the surfactant was eliminated by using a brief washing with
Levulinic acid
Formic acid
O
O
HO
HO
O
OH
HO
+
OH
Dehydration
O
H
OH
O
O
O
HO
HO
OH
HO
H
O
OH
Sucrose
5-HMF
Insoluble humins + soluble polymers
Scheme 1 Schematic illustration of the transform of sucrose into 5-HMF and side-products
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Journal of the Iranian Chemical Society
Table 1 Elemental analysis and textural parameters provided by the
OH
O-Si-O
OH
mesoporous KIT-6 and catalysts
KIT-6
VK1
Code SBET a (m2g−1
)
VPb (cm g−1)* dpb (nm)* %V c %P c
3
KIT-6 549
0.46
0.20
0.18
0.17
0.19
6.30
6.24
6.24
24.48
10.58
–
–
VK1
VK2
VH
162
100
29
11.8 14.0
17.8 21.1
22.9 27.5
VK2
VH
VP
32
–
–
a
From BET,
From BJH,
From ICP-OES
b
c
P–OH
OH
PO
OPO
3
V=O
1000
HMF Yield % = Produced HMF∕Initial carbohydrate × 100
4000
3000
2000
-
1
Wavenumber (cm )
Fig. 1 FT-IR spectra of the VHP/KIT-6 catalysts, unsupported VHP,
and pure KIT-6
Results and discussion
Elemental analysis by ICP‑OES
increased (VH>VK2>VK1). In addition, the FT-IR spec-
trum of initial material V O (Fig. S1) demonstrated high
2
5
Evaluation of the actual contents of vanadium and phospho-
rous in the prepared catalysts was carried out by using the
ICP-OES technique, as shown in Table 1. It was indicated
that the phosphorous- to- vanadium ratio in the prepared
catalysts was 1.2, in agreement with the theoretical values
of a bulk P/V ratio.
intensities vibrations bonds of V= O and VOV. Also, the
FT-IR spectrum of calcined VPO (VP) is exhibited in Fig.
S1.
XRD patterns
The low-angle XRD patterns of KIT-6 and VHP/KIT-6 cata-
lysts are shown in Fig. 2a. It is evident that, for the pristine
KIT-6, the sharp peak at 2θ=1.07° and the two broad peaks
at 2θ=1.73° and 1.94° can be assigned to the (211), (420)
and (431) planes, respectively, demonstrating the character-
istic of considerably ordered three-dimensional cubic space
group Ia3d symmetry present in the mesoporous structure of
silica KIT-6 [58]. For the VHP/KIT-6 catalysts, the intensi-
ties of the peaks decrease when the loading amounts of VHP
on KIT-6 increase, arising from the partial ꢁlling of KIT-6
pores via VHP species, whereas the cubic Ia3d symmetry
of the silica can be simultaneously preserved. In the cases
of V O , VH and VP (Fig. S2), there are no peaks related
FT‑IR Spectroscopy
FT-IR spectroscopy was employed to study the functional
groups of the prepared catalysts, as exhibited in Fig. 1. As
can be seen in the pure KIT-6 spectrum, the peaks observed
−
1
at 1078, 800 and 460 cm can be related to the asymmet-
ric and symmetric stretching and bending bands of O-Si–O,
respectively [55]. In addition to the peaks observed at 600
−
1
and 1300 cm in the VH and VHP/KIT6s spectrums,
which are assigned to V–O and P-O stretching bands, the
−
1
peaks below 1600 cm can also be related to O-V–O and
O–P–O bending modes. The FT-IR spectra detect 1200,
2
5
−
1
−1
1
9
104 and 1054 cm (ν , PO3), 1132 cm (δ , P–OH),
to mesoporosity.
as
ip
−
1
−1
−1
80 cm (ν, V = O), 931 cm (ν, P–OH), 684 cm (ω,
The wide-angle XRD patterns of VPP, VHP, VHP/KIT-6
catalysts are presented in Fig. 2b. Both the planes and peaks
of all the patterns except VP are shown in Table 2, well-
matched with the crystalline phase of VOHPO 0.5H O
−
1
coordinated H O), 642 cm (δ , P–OH), 548, 534, 480
2
oop
−
1
and 417 cm (δ, OPO) bands which corresponds to the
VHP phase [56]. The band, which has appeared at about
4
2
−
1
3
400 cm , can be related to the interlayer free structural
[ICDD Card No 01–084-0761]. For the VP phase, it is clear
that the reꢃections correspond to the monoclinic (VO) P O
7
water and the water molecules which coordinate to vana-
dium in the structure. Moreover, the bending modes of water
2
2
phase (ICDD Card No 00–041-0380). Moreover, the broad
peak present at about 23º can be related to the amorphous
structure of silica. In the case of lower intensities for VP
(inset graph in Fig. 2b) vs VH, it is due to thinner crystallites
−
1
molecules can also be observed at about 1630 cm [57].
Increasing loading amount, the peaks intensities of phos-
phate (P-OH,OPO and PO ) and vanadyl (V = O) groups
3
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Journal of the Iranian Chemical Society
shown in Table 1 and Fig. 3. As can be seen in Fig. 3, it is
evident that the graphs of the supported VHP catalysts and
mesoporous KIT-6 conꢁrm the type IV isotherms exhibit-
ing a sharp capillary condensation step at a rather pressure
range of 0.6–0.8 P/P0 as well as a typical H1 hysteresis loop
of mesoporous structures possessing a considerably uniform
pore size distribution. Also, it was indicated that no changes
were observed in the type of the hysteresis loops after sur-
face modiꢁcation of mesoporous silica KIT-6, demonstrat-
ing that the mesoporous structure of supported VHP could
be maintained. Conversely, as can be observed in Table 1,
the pore volume and surface area of the prepared catalysts
decreased gradually, depicting that VHP species could be
introduced to the interior pores of mesoporous silica KIT-
(
211)
(
a)
(
420)
(
431)
KIT-6
VK1
VK2
2
4
2
6
8
10
Theta (degree)
6
. Furthermore, as exhibited in the pore size distribution
proꢁles, negligible changes were observed in the average
pore diameter when compared to the pure KIT-6 mesoporous
silica.
VP
(
b)
The hysteresis loops present in the isotherms at 0.7<P/
P <1.00 are generally related to the slit-shaped pores, usu-
0
20
40
60
80
VP
ally observed on the aggregates, including plate-like par-
ticles [60]. By drawing a comparison between the unsup-
ported and supported VPO catalysts, it was found that an
enhancement in the speciꢁc surface area, a reduction in the
diameter of the average pores and an unchanged total pore
volume could be observed.
VH
VK2
VK1
SEM and TEM analysis
1
0
20
30
40
Theta (degree)
50
60
70
The characterization of the morphology, along with the
elemental analysis of the VK1 catalyst, was carried out by
using FESEM−EDX and TEM analyses. By investigating
the FESEM images of VK1 (Figs. 4a, b), it can be indicated
that the VK1 sample presents the rosette type morphology
with irregular plate-like petals. The investigation of the ele-
mental distribution of vanadium (V), phosphorous (P) and
oxygen (O) over mesoporous silica was also conducted by
using EDX analysis (Fig. 5).
2
Fig. 2 a Low-angle XRD patterns of VHP/KIT-6 catalysts and pure
KIT-6 and b wide-angle XRD patterns of VPO-based catalysts
of VP after activation [59]. The V O pattern (Fig. S3) cor-
2
5
responds to the pattern of orthorhombic vanadium oxide
(
ICDD Card No 01–072-0598).
According to TEM images of VK1 exhibited in Fig. 4c,
the VK1 sample possesses rhomboid-shaped and layered
platelets, which have been stacked together on top of each
other. The plate-like layers in this morphology are regarded
as the typical characteristic of VPO materials [61]. In addi-
tion, some TEM images is presented in Fig. S4.
N adsorption–desorption analysis
2
Nitrogen adsorption–desorption analysis was employed to
study both the textural characterization and porosity meas-
urements of the prepared catalysts and pristine KIT-6, as
Table 2 The position of peaks
No
θ (degree)
Planes (h k l) 0 0 1 1 0 1 0 2 1 1 2 1 2 0 1 1 3 0 0 3 1 0 4 0 2 4 1 4 0 0 5 1 0
1
2
3
4
5
6
7
8
9
10
11
and planes of VHP phase
2
15.57 19.57 24.4 27.13 28.81 30.49 32.17 37.42 47.92 49.17 63.25
d-spacing
5.69
4.51
3.67 3.29
3.10
2.93
2.79
2.40
1.90
1.85
1.46
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Journal of the Iranian Chemical Society
4
00
00
0
0
0
0
.3
.2
.1
BJH Profiles
2
KIT-6
KIT-6
VK1
.0 VK2
0
2
4
6
8
10
0
r (nm)
p
1
50
100
50
VK1
VK2
1
50
100
50
VP
VH
0
0.0
0.2
0.4
0.6
0.8
1.0 0.0
0.2
0.4
0.6
0.8
1.0
P/P0
P/P0
Fig. 3 The nitrogen adsorption–desorption isotherms of supported and unsupported VPO and pure KIT-6 and BJH proꢁles of VHP/KIT-6 cata-
lysts and pure KIT-6
NH TPD
Catalytic performance
3
‑
NH -TPD analysis made it possible to evaluate the acidic
The eꢂciency of the prepared catalysts was evaluated by
the dehydration reaction of sucrose, as the most abundant
disaccharide, to 5-HMF. The eꢀect of various parameters on
the reaction was studied. Scheme 2 schematically depicts the
plausible mechanism for the reaction, which is comprised
of hydrolyzation, isomerization and dehydration. First,
sucrose is hydrolyzed rapidly to fructose and glucose, and
subsequently, the formed fructose is converted to 5-HMF.
The conversion of glucose, nevertheless, is carried out at a
lower rate because of the isomerization to fructose before
dehydration [62]. Lewis acids are capable of catalyzing the
glucose isomerization to fructose through facilitating the
hydride shift, as isomerization catalysts [63]. Therefore,
vanadium, functioning as a Lewis acid, and the two adja-
cent hydroxyl groups of glucose form a ꢁve-member che-
late ring. Another possible pathway is a direct conversion
of glucose into 5-HMF via 3-deoxy-D-glucosane [62], but
3
properties of the synthesized VPO-based catalysts. The
NH -TPD proꢁles depicted a main peak at about 400 °C
3
attributed to the moderate acid sites (Fig. 6). The total acid-
ity order of the VPO-based catalysts and pure support is
VH>VK2>VK1>VP>KIT-6, as the summed peak areas
of NH -TPD proꢁles has been presented. As expected, a
3
very weak peak of NH desorption was exhibited by the
3
silica mesoporous KIT-6 because of its appreciably weak
acidity. For the supported VHP catalysts, it was indicated
that the acidic properties increased through increasing the
VHP loading amount. Furthermore, the uncalcined VPO was
found to possess higher total acidity in comparison with the
calcined VPO.
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Journal of the Iranian Chemical Society
Fig. 4 (a, and b) SEM images
and (c and d) bright-ꢁeld TEM
of VK1 catalyst in diꢀerent
magniꢁcations
Fig. 5 EDX spectrum and elemental distribution maps for the VK1 sample
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Journal of the Iranian Chemical Society
0
0
0
0
.3
.2
.1
.0
0
0
0
0
0
.0025
.0020
.0015
.0010
.0005
The efect oꢀ the sucrose to catalyst weight ratio
KIT-6
VK1
VK2
VH
KIT-6
(S/C)
The eꢀect of S/C on sucrose dehydration was also studied
in this study, as shown in Fig. 7b. According to the obtained
results, it was found that 5- HMF yield decreased under
higher acidity, arising from the production of unwanted
products, including levulinic acid, formic acid and humins.
Hence, S/C of 20 (10 mg VK1 for 200 mg sucrose) was
selected as the optimum catalyst weight and acidity amount.
It was observed that the sucrose conversion could be almost
accomplished (>90%) at diꢀerent sucrose to catalyst weight
ratios.
VP
1
00
200
300
400
500
1
00
200
300
400
500
600
The efect oꢀ temperature
Temprature (°C)
The eꢀect of temperature (130 °C to 190 °C) on the 5-HMF
yield and sucrose conversion was investigated, as can be
seen in Fig. 7c. It can be observed that an increase in tem-
perature has led to a signiꢁcant eꢀect on the reaction. By
increasing temperature to 170 °C, the 5-HMF yield was
rapidly enhanced. Nonetheless, at higher temperatures, the
5-HMF yield decreased because of the humins formation,
which was conꢁrmed by the darker color of the mixture.
However, the conversion of sucrose changed insigniꢁcantly
with the increasing temperature.
Fig. 6 NH -TPD proꢁles of VPO-base catalysts and pure KIT-6
3
glucose isomerization is more probable in the presence of
Lewis acid [64].
Then, the fructose dehydration route is followed by
water elimination, which takes place at the C-2 position of
D-fructofuranose, to prepare a tertiary carbocation. Finally,
it is followed by the next two β-dehydration steps, leading
to the formation of 5-HMF [1].
The efect oꢀ the catalyst type
The efect oꢀ reaction time
The eꢀect of the amount of VHP loaded on KIT-6 and also
unsupported VHP and VPP in the sucrose dehydration to
The performance of the VK1 catalyst in the sucrose dehy-
dration was studied in a variety of reaction times (30 to
75 min). As depicted in Fig. 7d, it was demonstrated that
the 5-HMF yield rose to 62% after 60 min, and after that, it
decreased, arising from the formation of more humins and
covering active sites of the prepared catalyst. The conversion
of sucrose by the VK1 catalyst could be almost completed
(>94%) after 75 min.
5
-HMF was studied, as represented in Fig. 7a. The results
show that VK1 with a lower loading amount is eꢀective in
catalytic activity. It seems that two parameters can aꢀect
the higher catalytic activity: surface area and surface acid-
ity. The higher surface area as a result of the lower loading
amount of VHP causes a higher 5-HMF yield. Conversely,
higher surface acidity, as a result of higher loading amount
of VHP, results in lower 5-HMF yield, arising from an
increase in unwanted rehydration and polymerization reac-
tions. Accordingly, the VK1 catalyst with lower surface
acidity, higher surface area and lower loading of VHP is
capable of providing higher catalytic activity in comparison
with the VK2 catalyst and unsupported VHP. Also, it can be
observed that uncalcined VPO with higher total acidity pos-
sesses a little higher 5-HMF yield compared with calcined
VPO. Furthermore, the negligible 5-HMF yield without
catalysts in the reaction conꢁrms a high catalytic activity in
the dehydration reaction.
The efect oꢀ sucrose concentration
The behavior of the VK1 catalyst in the dehydration reac-
tion was investigated in diꢀerent sucrose concentrations
(Fig. 7e). It was conꢁrmed that the sucrose conversion could
be almost accomplished (>92%) in various sucrose concen-
trations. Nevertheless, it was indicated that the 5-HMF yield
increased rapidly with the concentration increasing up to
250 mg. However, at higher dosages, due to the acceleration
of humins formation, it decreased [65].
The efect oꢀ solvent
The eꢀect of diꢀerent solvents, including DMSO, NMP,
H O and H O/THF, on the performance of the VK1 catalyst,
2
2
1
3

Journal of the Iranian Chemical Society
HO
O
OH
O
OH
HO
O
HO
HO
OH
Sucrose
OH
H O
2
OH
2
V
O
Glucose
O
Fructose
O
P
H
O
H
2
C
OH
O
C
O
H+
O
H
H
OH
H
O
HO
H
H
HO
H
H
2
O
O
O
P
OH
OH
V
OH
OH
OH
O
H
H
-
H O
2
CH OH
2
2
CH OH
H
O
C
OH
HO
HO
H
H
H
OH
H
H
H
OH
H
C
O
O
H
C
O
O
C
O
V
O
V
O
V
O
H
O
O
H
H
OH
OH
HO
HO
H
HO
H
H
HO
H
OH
OH
OH
OH
-H
O
2
H
H
OH
OH
2
CH OH
H
H
HO
CH
2
OH
CH
2
OH
OH
OH
CH
2
OH
O
Tautomerism
HO
H
O
H
O
C
C
-
H O
2
O
H
O
H
HO
O
-
H O
-H O
2
2
-H O
2
O
O
H
OH
OH
H
HOH
2
C
CHO
H
H
OH
5
-HMF
HO
CH
2
OH
2
CH OH
3-Deoxy-D-glucosone
Scheme 2 The proposed mechanism for the dehydration reaction of sucrose to 5-HMF
was studied (Fig. 7f). It was found that there are substantial
diꢀerences between DMSO and the other three solvents in
both the sucrose conversion and 5-HMF yield. It has been
reported that DMSO is capable of presenting catalytic activ-
ity in carbohydrates dehydration among all the high boiling
points aprotic solvents [66, 67]. In the present study, the
sucrose conversion and 5-HMF yield obtained> 94% and
which resulted in a slight increase in the 5-HMF yield to 6%
at 170 °C for 1 h. The HPLC chromatogram of 5-HMF is
presented in Fig. S5.
The efect oꢀ carbohydrate type
The performance of the VK1 catalyst on dehydration of dif-
ferent carbohydrates, including glucose, fructose and malt-
ose, was studied under the optimum conditions. As listed
in Table 3, the 5-HMF yield for fructose dehydration was
obtained 68% at 170 °C for 1 h. Generally, fructose dehy-
dration reaction is performed under milder conditions when
6
7% in DMSO, respectively. Furthermore, the sucrose con-
version of 94% and 5-HMF yield of 26% was obtained in
NMP. However, when H O was employed as a protic sol-
2
vent, no detectable HMF was observed. Besides, a mixture
of THF/H O was used in the sucrose dehydration reaction,
2
1
3

Journal of the Iranian Chemical Society
Fig. 7 The eꢀect of diꢀerent conditions on sucrose conversion and
d 200 mg sucrose, 4 ml DMSO, 10 mg catalyst of VK1, temperature:
170 °C; e 4 ml DMSO, 10 mg catalyst of VK1, temperature: 170 °C,
time: 60 min; and f 250 mg sucrose, 4 ml solvent, 10 mg catalyst
of VK1, temperature: 170 °C, time: 60 min. RSD: 5-HMF<7%,
sucrose<8%
5
1
4
2
-HMF yield. Reaction conditions: a 200 mg sucrose, 4 ml DMSO,
0 mg catalyst, time: 30 min, temperature: 130 °C; b 200 mg sucrose,
ml DMSO, catalyst of VK1, time: 30 min, temperature: 130 °C; c
00 mg sucrose, 4 ml DMSO, 10 mg catalyst of VK1, time: 30 min;
Table 3 The catalytic activity of the VK1 catalyst on dehydration of
other carbohydrates
Carbohydrate
5-HMF yield (%)
Carbohydrate
conversion
(
%)
9
0
Fructose
Glucose
Maltose
Maltose*
68
33
20
43
100
94
91
7
0
)
%
(
98
e
5
0
g
a
t
n
Conditions: Carbohydrate: 250 mg, VK1 catalyst: 10 mg, Solvent:
e
c
3
0
r
4
mL DMSO, Temperature: 170 °C, Time: 60 min, *Time: 150 min.
e
P
RSD: 5-HMF<6%, carbohydrates<8%
1
0
4
compared to glucose and maltose, which is comprised of two
glucose monomers.
C
o
n
3
versio
n
2
Yield
1
The catalyst reusability
Fig. 8 Reusability eꢂciency of the VK1 catalyst. Conditions:
sucrose: 250 mg, VK1 catalyst: 10 mg, Solvent: 4 mL DMSO, tem-
perature: 170 °C, time: 60 min. RSD: 5-HMF<7%, sucrose<3%
and drying at 120 °C overnight before being utilized for the
next run. It should be noted that no considerable change
Four consecutive dehydration reactions were performed
under the optimized conditions to evaluate the reusability
of the VK1 catalyst, as depicted in Fig. 8. After the accom-
plishment of each dehydration reaction, VK1 was separated
by using centrifugation, followed by washing with acetone
1
3

Journal of the Iranian Chemical Society
Table 4 Comparison between
the performance of the VK1
catalyst and some catalysts
of previous studies in sucrose
dehydration
Entry
Catalyst
T (°C)
Time (h)
Solvent
5-HMF
Reference
yield (%)
1
2
3
4
5
Nb W oxide
140
100
130
189
165
2
15
3
1
1
H O/iso-butanol
46
50
77
57.7
67
[68]
[69]
[70]
[71]
5
5
2
Amberlite IR 120
H O
2
CC-SO H
[GLY(mim) ][Cl]
3
3
3
ZnCl2
VK1
H O
2
DMSO
This work
was observed in both the 5-HMF yield and the sucrose
conversion.
possessing higher surface area and lower surface acidity
could provide much better catalytic activity.
The analysis of the recycled VK1 catalyst was conducted
by using FT-IR and XRD analyses. It is obvious in Fig. S1
that there are no additional bands in the FT-IR spectrum
of the recycled catalyst. According to Fig. S6, the retained
phase of VOHPO .0.5H O can be conꢁrmed through the
Besides, the eꢀect of diꢀerent parameters on the dehy-
dration reaction was studied in this work to achieve a better
sucrose conversion and a superior 5-HMF yield. Based on
the obtained results, it was concluded that the VHP loading
value and solvent type played an essential role in the reac-
tion because of the surface acidity value and catalytic activ-
ity of DMSO in dehydration reaction, respectively. Besides,
not only the outstanding catalytic activity in dehydration of
sucrose and other carbohydrates but also simply recycling
the catalysts indicated their ability to produce value-added
materials.
4
2
wide-angle XRD pattern of the reused VK1. In both analy-
ses, the intensity of the peaks decreased compared to the
fresh one indicating some VHP leaching during the reaction.
Comparison to previous reports
Supplementary Information The online version of this article (https://
doi.org/10.1007/s13738-021-02191-2) contains supplementary mate-
rial, which is available to authorized users.
For better evaluation of the present catalytic system eꢂ-
ciency, a comparison was drawn with the same systems hav-
ing been reported in the literature, as presented in Table 4.
The 5-HMF yield in the present research was appreci-
ably higher than the one provided by using the acidic ion
exchange resin Amberlite IR 120 or Nb-W Oxide (entries
Acknowledgments The authors would like to thank the financial
supports from the Isfahan University of Technology for this work
(
Research Council Grant).
1
, 2) and only slightly lower than the one provided by using
CC-SO H and ionic liquid, (entries 3), in which the ionic
3
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