Direct Conversion of 5-Hydroxymethylfurfural to Furanic Diether by Copper-Loaded Hierarchically Structured ZSM-5 Catalyst in a Fixed-Bed Reactor

Article abstract of DOI:10.1002/cctc.202100489

The highly-efficient conversion of 5-hydroxymethylfurfural (HMF) to 2,5-bis(ethoxymethyl)furan (BEMF) was achieved over the copper-loaded hierarchically structured ZSM-5 (Cu/HSZ) catalysts in the continuous fixed-bed reactor. The main reaction path for BEMF synthesis on the Cu/HSZ catalysts was confirmed as following: HMF was firstly hydrogenated to BHMF intermediates over metal sites and then the formed BHMF was etherified by acid sites. Benefiting from the ammonia evaporation (AE) method promoted the dispersion of copper and reduced the acidity, the Cu/HSZ-AE catalyst exhibited more excellent BEMF yield and stability than the catalyst prepared by conventional incipient-wetness impregnation (Cu/HSZ-IW). Indeed, the inactivation of Cu/HSZ-IW catalyst was mainly attributed to the deactivation of copper by carbon species deposition.

Full text of DOI:10.1002/cctc.202100489

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ChemCatChem
Direct Conversion of 5-Hydroxymethylfurfural to Furanic
Diether by Copper-Loaded Hierarchically Structured ZSM-5
Catalyst in a Fixed-Bed Reactor
+
[a]
+ [a, b]
[a, c]
[a, c]
[a, b]
Hualei Hu , Tingting Xue ,
Zhenxin Zhang, Jiang Gan, Liangqi Chen,
[
a, c]
[b]
[b]
[a, d]
Jian Zhang,* Fengzuo Qu, Weijie Cai,* and Lei Wang*
The highly-efficient conversion of 5-hydroxymethylfurfural
HMF) to 2,5-bis(ethoxymethyl)furan (BEMF) was achieved over
by acid sites. Benefiting from the ammonia evaporation (AE)
method promoted the dispersion of copper and reduced the
acidity, the Cu/HSZ-AE catalyst exhibited more excellent BEMF
yield and stability than the catalyst prepared by conventional
incipient-wetness impregnation (Cu/HSZ-IW). Indeed, the inacti-
vation of Cu/HSZ-IW catalyst was mainly attributed to the
deactivation of copper by carbon species deposition.
(
the copper-loaded hierarchically structured ZSM-5 (Cu/HSZ)
catalysts in the continuous fixed-bed reactor. The main reaction
path for BEMF synthesis on the Cu/HSZ catalysts was confirmed
as following: HMF was firstly hydrogenated to BHMF intermedi-
ates over metal sites and then the formed BHMF was etherified
Introduction
(hydroxymethyl)furan (BHMF) and then etherifying BHMF with
[
6]
alcohols to produce 2,5-bis(alkoxymethyl)furans (BAMF). As
compared with the mono-ether AMF, the diether BAMF possess
the higher stability of the molecular structure as well as the
With the depletion of fossil resources and the serious environ-
mental pollution, utilization of renewable biomass resources to
produce the valuable fuels and chemicals has received growing
[5]
wider carbon number range and application fields.
[1]
interests. 5-Hydroxymethylfurfural (HMF), obtained from bio-
mass-derived sugars via dehydration, has been identified as the
key platform compound for synthesis of 2,5-furandicarboxylic
acid (FDCA), levulinic acid (LA), furanic ethers, and other high-
So far, the two-step route, i.e., the isolated HMF hydro-
genation and BHMF etherification process, had been widely
[7]
investigated over various heterogeneous catalysts. For in-
[7a]
stance, Chatterjee et al. used the Pt/MCM-41 as catalyst for
HMF hydrogenation, obtaining 98.9% yield of BHMF under
[
2]
valued chemicals. Among them, furanic ethers have drawn
considerable attention in recent years considering their high
energy density, high cetane number, and suitable fuel blending
[
7b]
0.8 MPa of H at 35°C for 2 h. Han et al. reported that the
2
Ru(OH)x/ZrO catalyst gave 99% yield of BHMF under 1.5 MPa
2
[3]
[7c]
properties. Currently, most of the literature has focused on the
etherification of HMF with alcohols to produce 5-(alkoxymethyl)
of H at 120°C for 2 h. Balakrishnan et al. tested the perform-
2
ance of Amberlyst-15 in etherification of BHMF with ethanol, in
which a 80% yield of 2,5-bis(ethoxymethyl)furan (BEMF) was
[4]
furfural (AMF). However, the remained aldehyde functional
[5]
[7d]
group significantly reduces its molecule stability. To overcome
this drawback, some researchers hydrogenating HMF to 2,5-bis
achieved after reaction at 40°C for 16 h. Musolino et al.
demonstrated that the acid purolite could efficiently accelerate
the etherification of BHMF, leading to a 99% yield of BEMF
under mild conditions (at 40°C for 24 h). In our previous work,
+
+
[
a] Dr. H. Hu, T. Xue, Z. Zhang, J. Gan, L. Chen, Prof. J. Zhang, Prof. L. Wang
Ningbo Institute of Materials Technology & Engineering
Chinese Academy of Sciences
the potassium-doped Cu/Al O catalyst was found to exhibit
2
3
superior performance in selective hydrogenation of HMF and a
1
219 Zhongguan West Road
Ningbo 315201 (P. R. China)
E-mail: jzhang@nimte.ac.cn
wanglei@nimte.ac.cn
98.9% yield of BHMF was achieved in fixed bed reactor under
[
8]
2
.0 MPa of H at 120°C. Moreover, the hierarchically structured
2
+
ZSM-5 zeolites (HSZ) was applied in our group for the ether-
ification of BHMF with ethanol, obtaining 94.7% and 90.4%
yield of BEMF in the batch and fixed bed reactors, respectively.
[
b] T. Xue, L. Chen, Prof. F. Qu, Prof. W. Cai
Dalian Polytechnic University
No. 1st Qinggongyuan
[
9]
Ganjingzi, Dalian 116034 (P. R. China)
E-mail: caiwj@dlpu.edu.cn
c] Z. Zhang, J. Gan, Prof. J. Zhang
University of Chinese Academy of Sciences
No.19(A) Yuquan Road, Shijingshan District
Beijing 100049 (P. R. China)
However, as for the two-step route, heavy costs incurred in the
intermediate product separation and purification is unavoid-
able, which restrict its pilot-scale application to some extent.
The direct conversion of HMF to BAMF (i.e., one-step route)
could avoid the tedious purification steps and thus help to
reduce the energy consumption, cost operation and waste
emission, thereby resulting in a green and sustainable synthesis
[
[
d] Prof. L. Wang
Zhejiang Sugar Energy Technology Co. Ltd.
1
818 Zhongguan West Road
Ningbo 315201 (P. R. China)
[10]
+
process. Nowadays, only few works have been conducted on
the direct production of BAMF from HMF under hydrogen
[
] These authors contributed equally to this work.
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/cctc.202100489
[7c]
atmosphere. Balakrishnan et al. combined the Pt/Al O and
2
3
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Amberlyst-15 catalysts for hydrogenation and etherification in Results and Discussion
one batch reactor, in which only 59% yield of BEMF was
[
6a]
achieved at 60°C for 18 h under 1.38 MPa H . Cao et al. used
Figure 1a shows the XRD patterns of the synthesized HSZ
support and Cu/HSZ catalysts. The diffraction patterns of the
HSZ were consistent with the reported MFI-structured materials
and no other diffraction peaks could be detected, indicating
that the synthesized HSZ sample was the pure MFI-type
2
Cu/SiO and ZSM-5 as the catalysts for 2,5-bis(methoxymethyl)
furan (BMMF) synthesis and 68% yield of BMMF was observed
2
after reaction at 120°C for 12 h under 2.5 MPa H . In contrast to
2
the physical combination of two different catalysts, using
bifunctional catalyst (containing two types of active compo-
nents within nanoscale distances) could enable the reaction
[14]
zeolite.
All of the Cu/HSZ catalysts exhibited the similar
diffraction peaks to HSZ sample, implying that the framework
structure of HSZ was maintained after the copper loading.
Moreover, no diffraction peaks corresponding to CuO could be
observed on the Cu/HSZ catalysts, which might be ascribed to
its higher dispersion in HSZ crystals or the small particles below
[11]
more successively and efficiently in the catalysis cascade. Wei
[12]
et al. used the Cu-USY bifunctional catalyst for conversion of
HMF to BMMF. Unfortunately, only 11.4% yield of BMMF was
achieved due to the unsatisfactory catalyst activity. Therefore, it
is urgent to develop efficient and stable bifunctional catalyst for
the direct transformation of HMF to furanic diether. Moreover,
most of research work conducted the reaction in the batch
reactor. In contrast, the continuous operation in the fixed-bed
reactor is more efficient and more advantageous for the large-
[8,15]
the detection limit of XRD.
Figure 1b shows the N physisorption-isotherms of the as-
2
prepared catalysts. It can be seen that all of the samples
showed the type-IV hysteresis loop, which was associated with
the capillary condensation of the probe molecule in
[13]
[16]
scale industrial production.
mesopores. Moreover, the BJH pore size distribution of these
In this work, the copper-loaded HSZ bifunctional catalyst
was prepared via the incipient-wetness impregnation (IW) and
ammonia evaporation (AE) method, respectively. The effect of
copper loading on the physicochemical properties of the
bifunctional catalysts was systemic characterized. By evaluating
the catalytic performance of bifunctional catalysts in the fixed
bed reactor, the role of metal and acid sites in the hydro-
genation-etherification process was investigated in detail to
propose the reaction path.
samples was given in Figure 1b insert. Both the HSZ sample and
copper-loaded HSZ catalysts possessed the similar pore size
distribution (3~100 nm). As listed in Table 1, the micropores
3
À 1
and mesopores volume of HSZ sample was 0.097 cm ·g and
3
À 1
0.36 cm ·g , confirming that the synthesized HSZ sample was
hierarchically structured ZSM-5 zeolites. As for the Cu/HSZ-IW
prepared by incipient-wetness impregnation, both the micro-
pores and mesopores volume was slightly lower than that of
the HSZ sample, which could be attributed to that the partially
[17]
pore was blocked by the copper component. While for the
2
Figure 1. XRD patterns (a), N adsorption-desorption isotherms (b), and pore size distribution (inset) of the samples.
Table 1. Chemical compositions and physicochemical properties of the samples.
Sample
Si/Al
moral ratio
Cu
[wt%]
Cu
[wt%]
Surf. Cu
[wt%]
S
BET
2
V
micro
3
V
meso
3
D
[%]
Cu
[g]
S
Cu
d
[nm]
Cu
X
[%]
Cu0
[a]
[a]
[b]
[c]
À 1 [d]
À 1 [e]
À 1 [f]
2
[f]
[g]
[h]
[m ·g
]
[cm ·g
]
[cm ·g
]
[m /g]
HSZ
Cu/HSZ-IW
Cu/HSZ-AE
102.1
101.3
96.8
0
5.15
5.30
0
5.01
4.92
0
9.72
15.0
417
371
378
0.097
0.084
0.077
0.36
0.33
0.39
/
/
/
/
35.4
43.3
229.7
280.9
2.82
2.30
45.0
45.5
[
a] Calculated by XRF. [b] Calculated by ICP-OES. [c] Calculated by XPS. [d] Determined by BET method. [e] Estimated using the t-plot method. [f] Determined
by a subtraction of total pore volume at a relative pressure of P/P
exposed metallic copper surface area, and copper particle size were calculated by N
Cu ) by deconvolution of Cu LMM XAES.
0
=0.99 from the microporous pore volume obtained from the t-plot. [g] Copper dispersion,
0
+
2
O adsorption-decomposition.[h] Intensity ratio between Cu and (Cu
+
0
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Cu/HSZ-AE sample, although the volume of micropores de-
exhibited a regular ellipsoidal shape with a particle size of
about 200~500 nm. Moreover, numerous cavities could be
observed on their surfaces. The TEM images depicted that these
ellipsoidal particles were formed by the aggregation of
crystalline nanoparticles. Thus, the additional mesoscale poros-
3
À 1
creased to 0.077 cm ·g , the mesopores volume increased to
3
À 1
0
.39 cm ·g . This could be ascribed to that a part of framework
siliceous species was extracted by the alkaline ammonia
solution, which in turn generated the additional mesopores at
[18]
[16]
the expense of micropores.
This also well explained the
ity was created between these nanoparticles.
decline of diffraction peaks intensity and Si/Al ratio of Cu/HSZ-
AE catalyst.
NH -TPD and Py-IR were performed to investigate the acidic
3
properties of the samples. As shown in Figure 3a, the NH -TPD
3
Figure 2 gives the SEM and TEM images of the synthesized
HSZ samples. As seen in Figure 2a and 2b, the HSZ sample
profiles of the synthesized HSZ sample exhibited three peaks,
denoted as low-temperature, middle-temperature, and high-
temperature peaks, which could be attributed to the ammonia
molecules absorbed on the weak, moderate, and strong acid
[19]
sites, respectively. In contrast, the peak temperature of strong
acid sites on the reduced Cu/HSZ samples was obviously lower,
suggesting that the loading of copper led to the greatly
decrease in the acid strength. This might be due to the
interaction of the surface acid sites and the introduced copper
[20]
species. In addition, it was also noted that the amount of
moderate acid sites on the Cu/HSZ catalysts remarkably
increased, which led to the increase in total acid amount
(
Table 2). According to the literature, the copper species could
[
21]
adsorb the ammonia molecules and then desorb sequentially.
Thus, the increase in the acid sites amount observed on the Cu/
HSZ catalysts was reasonable. As compared to the Cu/HSZ-IW
catalyst, both the strength and amount of acid sites on the Cu/
HSZ-AE sample was relatively lower, which could be attributed
to that the leaching of framework siliceous species in the
Figure 2. SEM (a–b) and TEM (c–d) images of the HSZ samples.
3
Figure 3. NH -TPD (a), Py-IR (b) and Cu 2p XPS spectra (c and d) of the samples.
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Table 2. Surface acid properties of the HSZ and Cu/HSZ samples.
À 1 [a]
Catalyst
3
Number of acid sites (mmol of NH g )
[
b]
[c]
[c]
weak
moderate
strong
Total acid
Ratio of B/L
Brønsted acid
Lewis acid
(
<200°C)
(200~300°C)
(>300°C)
HSZ
Cu/HSZ-IW
Cu/HSZ-AE
0.42
0.22
0.23
0.05
1.00
0.94
0.63
0.38
0.28
1.10
1.60
1.45
5.63
0.18
0.15
0.93
0.24
0.19
0.17
1.36
1.26
[
a] Calculated by NH
3
-TPD. [b] Determined by Py-IR. [c] Number of Brønsted and Lewis acid were calculated by the ratio of B/L and the total amount of acid
-TPD, respectively.
sites, which determined by Py-IR and NH
3
ammonia-evaporation method also reduced the amount of
framework aluminum species being responsible for the for-
[22]
mation of acid sites.
Figure 3b shows the Py-IR spectra of the samples. The bands
À 1
À 1
at 1545 cm and 1454 cm were ascribed to the adsorptions
[23]
of pyridine on the Brønsted and Lewis acid sites, respectively.
It can be seen that the amount ratio of Brønsted acid sites to
Lewis acid sites (abbreviated as B/L) of the HSZ sample was 5.63
(Table 2), indicating that the aluminum species on the synthe-
sized HSZ sample mainly existed as the coordinatively saturated
sites (Brønsted acid). With the introduction of copper, the band
intensity assigned to Brønsted acid decreased, while the band
intensity assigned to Lewis acid significantly increased, which
might be due to that some Brønsted acid sites of zeolite were
2
+ [24]
converted to Lewis acid by exchanged with Cu
.
This also
led to the dramatically declined in B/L ratio of Cu/HSZ catalysts.
In addition, this phenomenon further confirmed the interaction
of surface acid sites and copper species from the other side.
The chemical states of copper over the calcined and
reduced Cu/HSZ catalysts were detected via XPS technique. In
contrast to the calcined samples, the spectra peaks at 940–
Figure 4. HAADF/STEM images (left) and the relevant particle size distribu-
tions (right) of the reduced Cu/HSZ-IW (a) and Cu/HSZ-AE (b) samples.
9
45 eV and 960–965 eV disappeared in the reduced samples.
and sintering of copper particles during thermal treatment
process.
[27]
Meanwhile, the peak at a binding energy of 935.5 eV was
shifted to about 932.7 eV, meaning that the Cu on the Cu/
HSZ catalysts had been reduced to Cu or Cu during the
reduction process. In order to discriminate the Cu species
2
+
H -TPR was conducted to investigate the reduction behavior
2
+
0
of the Cu/HSZ catalysts. As shown in Figure 5, the reduction
[25]
+
peaks in the range of temperature 140–220°C were observed
0
from Cu species, the Cu LMM XAES spectra were collected
on Cu/HSZ samples, which could be ascribed to the reduction
[8]
(Figure 1S). The XAES profiles were split into two symmetrical
of CuO. On the other hand, a reduction peak at the temper-
peaks centered at about 914.0 and 917.0 eV, corresponding to
ature of 184°C was noted for the Cu/HSZ-IW sample. As for the
+
0
0
Cu and Cu species, respectively, indicating that both Cu and
+
Cu coexisted on the surface of the reduced Cu/HSZ
[26]
0
catalysts. Moreover, the percentage of Cu on the Cu/HSZ-IW
and Cu/HSZ-AE catalyst was similar (Table 1).
The dark-field TEM images and relevant particle size
distributions of the reduced Cu/HSZ samples are shown in
Figure 4. It can be seen that in all cases, the copper particles
were uniformly dispersed on the HSZ support. In contrast, the
average size of the copper particles on Cu/HSZ-AE (2.25 nm)
was lower than that of Cu/HSZ-IW (2.80 nm), which was
consistent with the copper dispersion measured by N O
2
adsorption-decomposition (Table 1). This finding indicated that
using the ammonia-evaporation method could facilitate the
formation of copper particles with smaller size. The reason
might be attributed to that the strong interaction between the
copper species and HSZ support prevented the transmigration
Figure 5. H -TPR profiles of Cu/HSZ samples synthesized by different
methods.
2
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Cu/HSZ-AE sample, the reduction peaks shifted to 172°C,
suggesting that the CuO species on the Cu/HSZ-AE sample
were relatively easier to be reduced than the Cu/HSZ-IW
sample. It is well known that as compared to the bulk CuO
particles, the highly dispersed copper species can be more
easily reduced because of their relatively higher surface area
increasing the reaction time, the HMF conversion of Cu/HSZ-IW
catalyst slowly decreased to 93.9%, indicating the gradual
catalyst deactivation during the reaction. While for the Cu/HSZ-
AE catalyst, the conversion of HMF was still maintained at
above 99.0%. The result depicted that the Cu/HSZ-AE catalyst
in the direct conversion of HMF was more stable than the Cu/
HSZ-IW catalyst.
[28]
exposed to H2. As suggested by TEM and N O adsorption-
2
decomposition, the Cu/HSZ-AE sample possessed the smaller
average size of copper particles and higher copper dispersion,
thereby resulting in the decrease of reduction temperature.
In order to check the distribution of copper nanoparticles
on the HSZ support, the ICP-OES, XRF, and XPS were used. As
seen in Table 1, the copper content detected by the ICP-OES
and XRF was closer to the nominal value. In contrast, the
content of surface copper calculated from the intensities of
signals in XPS spectra was significantly higher, indicating that
the copper species was favored to distribute on the outer
The BEMF yield on the different catalysts was displayed in
Figure 6b. It can be seen that the yield of BEMF on the HSZ
catalyst was lower than 3.5% all along, indicating that HMF was
mainly converted into other products. For the Cu/HSZ catalysts,
the yield of BEMF increased during the first 1.5 h and reached a
maximum of 77.1%. However, in the subsequent time, the two
Cu/HSZ catalysts exhibited the significant difference in the
trend of BEMF yield. For the Cu/HSZ-IW, the BEMF yield sharply
decreased to 63.3%, while the Cu/HSZ-AE catalyst maintained
at about 80.0% yield of BEMF. This clearly indicated the higher
stability of Cu/HSZ-AE catalyst.
[29]
surface of the HSZ support.
Figure 6 gives the catalytic performance of the synthesized
HSZ catalyst and Cu/HSZ catalysts in the direct conversion of
HMF to BEMF. As shown in Figure 6a, the conversion of HMF
over the HSZ increased to 75.4% at the first 1.5 h and then
maintained at about 77.0% in the next 6.5 h. In comparison
with HSZ support, the Cu/HSZ-IW and Cu/HSZ-AE catalysts
exhibited higher catalytic activity, obtaining about 98.4% and
In order to investigate the reason for the high BEMF yield
obtained over the Cu/HSZ-AE catalyst as well as its high
stability, it is necessary to understand the conversion path of
HMF and the role of copper and acid sites. In general, HMF
could be converted to the targeted product BEMF via the
reaction path as follows (Figure 7): a) HMF was firstly hydro-
genated into BHMF by the metal sites and then BHMF was
etherified with ethanol over the acid sites to produce EMFA and
BEMF in sequence. b) HMF was etherified into EMF by the acid
sites, and the formed EMF was then hydrogenated into EMFA
over the metal sites. Finally, the EMFA was further etherification
with ethanol to produce BEMF. c) HMF was firstly hydrogenated
into BHMF by the acid catalyzed Meerwein-Ponndorf-Verley
9
9.3% conversion of HMF at 1.5 h, respectively. With further
(
MPV) reaction. Then, the formed BHMF was converted to BEMF
[3,12]
via the acid-catalyzed etherification.
With the aim to verify the specific reaction path, the
performance of Cu/HSZ-AE catalyst was evaluated under the
nitrogen atmosphere. In this case, BHMF could not be formed
via the copper catalyzed hydrogenation of HMF with hydrogen.
As shown in Figure 2S, the maximum HMF conversion and
BEMF yield on the Cu/HSZ-AE catalyst was only about 72.7%
and 20.5%, respectively. Moreover, upon increasing reaction
time, the yield of BEMF rapidly decreased to 6.2%. This
suggested that the Cu/HSZ-AE catalyst could indeed facilitate
the conversion of HMF to BHMF via the MPV reaction, but it
might not be the main reaction path for the synthesis of BEMF.
Figure 6. Catalytic performances of the HSZ and Cu/HSZ catalysts in the
direct conversion of HMF to BEMF. (Reaction conditions: 1.0 g catalyst,
À 1
À 1
2
.0 gL HMF/ethanol, WHSV of HMF=0.05 h , 2.0 MPa H
2
, and 140°C.
Figure 7. Proposed reaction pathways for the conversion of HMF to BEMF.
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Table 3. The activity and selectivity of HSZ and Cu/HSZ catalysts in the direct conversion of HMF to BEMF.
Catalyst
Raw material
Conversion
%]
Selectivity [%]
[
BEMF
EMFA
BHMF
EMF
EMFDEA
HMFDEA
ROP
THP
unknown
HSZ
HMF
HMF
HMF
77.4
93.9
99.0
65.5
1.9
4.4
2.6
1.8
3.3
/
/
/
68.3
3.6
/
2.6
/
/
17.3
4.8
2.1
/
/
5.5
5.0
8.0
10.6
Cu/HSZ-IW
Cu/HSZ-AE
Cu/HSZ-AE
67.4
80.6
9.5
13.5
6.5
/
3.1
1.8
/
HMF(N
2
)
11.4
4.4
14.4
46.4
À 1
À 1
Reaction conditions: 1.0 g catalyst, 2.0 gL HMF/ethanol, WHSV of HMF=0.05 h , 2.0 MPa H
2
, 140°C, 8 h.
According to the literature, both the Brønsted acid sites and
Lewis acid sites could catalyze the etherification reaction, but
only the Lewis acid sites could catalyze the MPV reaction.
acid bifunctional catalysts, this phenomenon might be due to
the deactivation of metal sites or acid sites. In this case, the
catalytic performance of Cu/HSZ-IW catalyst in etherification of
BHMF with ethanol was tested. As seen in Figure 8a, both the
BHMF conversion and BEMF yield were increased at the
beginning and then maintained at about 100% and 72~74%,
respectively, during the whole testing period. Subsequently, the
performance of the used Cu/HSZ-IW catalyst (HMF feeding,
reaction at 140°C for 8 h) was evaluated in the etherification of
[3]
Although the introduction of copper significantly increased the
amount of Lewis acid sites, the MPV reaction was promoted
slightly, suggesting that the introduced Lewis acid sites was not
highly active for this reaction. The reason could be ascribed to
that the strength of these Lewis acid sites was lower than the
[3b]
Lewis acid sites formed by framework Sn or Zr. Moreover, in
the reductive etherification of HMF, the MPV conversion of HMF
BHMF by transforming the HMF into BHMF (Figure 8b). It can be
seen that after feeding with BHMF, the BEMF yield increased to
73%, which was closing to that observed on the fresh Cu/HSZ-
IW catalyst. Thus, for the direct conversion of HMF, the
dramatically decrease of BEMF yield observed over the Cu/HSZ-
IW catalyst should be attributed to the deactivation of metal
sites.
[5a]
to BHMF is the rate-determining step. In this case, the contact
time of the formed BHMF and acid sites was further shortened,
which led to the presence of BHMF in the product. Then, the
performance of Cu/HSZ-AE catalyst were further tested in EMF
conversion (Figure 3S). It can be seen that although the
conversion of EMF could be reached to above 90%, no BEMF
was generated and the yield of EMFA was lower than 2.0% all
along, indicating that the Cu/HSZ-AE catalyst could not
effectively produce the BEMF from HMF via the intermediate
EMF. Based on the above results, it was reasonable to propose
that the main reaction path for the synthesis of BEMF over the
Cu/HSZ-AE catalyst was route a, i.e., HMF was firstly hydro-
genated overactive copper species and then the formed BHMF
was etherified by acid sites.
The product selectivity of the HSZ and Cu/HSZ catalysts are
listed in Table 3. For the HSZ catalyst, the selectivity of EMF and
5
-(hydroxymethyl)-furfural diethyl acetal (HMFDEA) was reached
to 68.3% and 17.3%, respectively, which should be ascribed to
that the catalyst only possessed the acid sites. While for the Cu/
HSZ catalysts, HMF could be effectively converted into BEMF. As
compared to the HSZ catalyst, the selectivity of ring-opening
products (ROP) and transitional hydrogenation products (THP)
on the Cu/HSZ catalysts was significantly higher, suggesting
that the side reactions such as transitional hydrogenation,
hydrogenolysis, and ring-opening was indeed promoted by the
[8,30]
coexistence of copper and acid sites.
The other direct
evidence was that when using the nitrogen as carrier gas, in
which the hydrogenation performance of copper sites was
suppressed, the ROP and THP products were not detected over
the Cu/HSZ-AE catalyst. We also noted that the selectivity of
ROP and THP products on the Cu/HSZ-IW catalyst was higher
than that on the Cu/HSZ-AE catalyst, which might be ascribed
to that the relatively weak acidity of Cu/HSZ-AE catalyst
suppressed the occurrence of side reactions.
Figure 8. Catalytic performances of the Cu/HSZ-IW catalyst in etherification
À 1
As discussed above, the Cu/HSZ-IW catalyst exhibited the
poor stability in the direct conversion of HMF. For the metal-
of BHMF to BEMF. (Reaction conditions: 1.0 g catalyst, 2.0 gL BHMF
À 1
/
ethanol, WHSV of BHMF=0.05 h , 2.0 MPa H
2
, and 140°C).
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The copper content and particle size distributions of the
etherified to produce BEMF. Moreover, the deactivation of Cu/
HSZ catalysts should be attributed to the deposition of carbon
species on the copper sites. As compared to the Cu/HSZ-IW
catalyst prepared via incipient-wetness impregnation, the Cu/
HSZ-AE catalyst prepared by the ammonia evaporation (AE)
method exhibited more excellent BEMF yield and stability. This
reason could be ascribed to that the AE method facilitated the
dispersion of copper particles and reduced the acidity, which in
turn improved the hydrogenation activity and carbon deposi-
tion tolerance of the catalyst. The results of this work would
help to develop efficient metal-acid bifunctional catalyst for the
industrial production of BAMF from HMF.
used catalysts were also characterized by ICP-OES, TEM and N2
adsorption (Table 4). The results showed that the amount of
copper species on the used Cu/HSZ-IW and Cu/HSZ-AE catalysts
was 4.79 wt% and 4.74 wt%, which was lower than that of the
fresh catalysts. This change was mainly due to the formation of
carbon deposition on the catalyst. After adjusting the Cu
content by deducting the carbon deposition, the actual content
of Cu was almost same to that of the fresh catalysts. Moreover,
the average size of the copper particles was also maintained
after the reaction (Figure 4S). These results indicated that the
leaching of copper species and transmigrating of copper
particles during the reaction were negligible. In this case, it was
reasonable to deduce that the deactivation of Cu/HSZ-IW
catalyst should be due to the inactivation of copper species.
According to the literature, the carbon deposition might be
Experimental Section
Materials: Ethanol (EtOH,�99.7%), tetraethyl orthosilicate (TEOS,
[31]
the main reason for the deactivation of the Cu-base catalysts.
SiO �28.4%), copper nitrate trihydrate (Cu(NO ) ·3H O, 99%),
2
3 2
2
Then, TG technique was selected to quantitatively analyze the
carbon deposition on these catalysts after 8 h reaction time
Figure 5S). As listed in Table 4, the carbon content of Cu/HSZ
ammonium hydroxide (NH ·H O, 25%), and tetra-n-propylammo-
3 2
nium hydroxide (TPAOH, 25%) were obtained from Sinopharm
Chemical Reagent Co., Ltd. (Shanghai, China). Aluminum isoprop-
oxide (AIP, 99.99%), hexadecyltrimethoxysilane (HTS,�85%), and
(
catalysts was higher than 2.5%, meaning that a small part of
HMF or its derivatives was converted into carbon deposition via
the polymerization. The decrease in the BET surface area of the
used catalyst also confirmed the influenced of carbon deposi-
tion on the catalyst from the other side. It is worth noting that
the stronger acidity of zeolites could promote generation of
5-ethoxymethylfurfural (EMF, 97%) were purchased from Aladdin
Industrial Inc. (Shanghai, China). 5-Hydroxymethylfurfural (HMF,
9%) and 2,5-bis(hydroxymethyl)furan (BHMF, 99%) were provided
9
by Zhejiang Sugar Energy Technology Co., Ltd. (Ningbo, China).
Catalyst synthesis: Hierarchically structured ZSM-5 zeolite (HSZ)
was prepared by a dry-gel conversion method. The preparation
procedure of the HSZ sample was as follows: Firstly, AIP, TPAOH,
and 500 mL of the EtOH were mixed under stirring. After the AIP
was completely dissolved to form clear solutions A, TEOS, HTS, and
[2]
carbonaceous deposit. The direct evidence is that the HSZ
catalyst which possesses the stronger acidity, has the maximum
amount of carbon deposition (3.67%). As compared to the Cu/
HSZ-IW catalyst, the acidity of Cu/HSZ-AE catalyst was relatively
weaker, which could help to decrease the generate rate of
carbon deposition. Moreover, considering the carbon deposi-
tion is a slow process, the deactivation of Cu/HSZ-IW catalyst
was observed after first 1.5 h, while the Cu/HSZ-AE catalyst
maintained the high BEMF yield even though extend the time
to 8 h. Hence, it is reasonable to deduce that the carbon
deposition tolerance of Cu/HSZ-AE catalyst was higher, which
should be attributed to its smaller size of copper particles.
500 mL of ethanol were successively added to the solutions A to
obtain a mixed solution with a molar ratio of 1SiO : 0.005Al O :
2
2
3
0
.2TPAOH: 0.05HTS: 20EtOH. The mixed solution was then intensely
stirred until a homogeneous gel was achieved. Subsequently, the
gel was aged in fume cupboard for 5 days at room temperature to
obtain the dry gel by evaporating the solvent. Dry gel was added
into a 50 mL PTFE inner cup before placed in a Teflon-lined
autoclave reactor (250 mL). Moreover, 70 mL of deionized water
was added between the two PTFE inner cups. The crystallization
was carried out in an oven at 180°C for 72 h. After crystallization,
the obtained product was filtered and washed with deionized water
for three times. Then the product was dried in an oven at 100°C for
1
2 h and calcined in a muffle furnace at 550°C for 7 h to obtain the
H-form HSZ catalyst.
Conclusion
The HSZ supported Cu catalysts were prepared by incipient-
wetness impregnation (IW) and ammonia-evaporation deposition-
precipitation (AE), which were denoted as Cu/HSZ-IW, Cu/HSZ-AE,
respectively. The nominal Cu loading of these catalysts was 5.0 wt
In this work, the direct conversion of HMF to BEMF was
investigated in detail over the copper-loaded hierarchically
structured ZSM-5 catalyst. The results demonstrated that for the
Cu/HSZ catalysts, the main reaction path was that HMF was
firstly hydrogenated into BHMF and then the BHMF was
%
.
Cu/HSZ-IW catalyst was prepared as follows: 1.0 g Cu-
(NO ) ·3H O was first dissolved in 8 g deionized water. Then, 5 g
3
2
2
HSZ was immersed in the solution for 24 h. The obtained solid was
dried in an air oven at 100°C for 24 h and calcined at 480°C for
10 h.
Table 4. Physicochemical properties of the used Cu/HSZ catalysts.
Cu/HSZ-AE catalyst was synthesized by deposition precipitation
using ammonia evaporation. 1.0 g Cu(NO ) ·3H O, 60 g deionized
Catalyst
Cu
d
[nm]
Cu
S
BET
2
Carbon deposition
[wt%]
3 2
2
[
a]
[b]
À 1 [c]
[d]
[
wt%]
[m ·g
]
water, and 8 mL NH ·H O were added to a 100 mL three-neck flask.
3 2
After mechanical stirring (200 rpm) for 10 min, 5 g HSZ was added
to flask and then stirred for 4 h at room temperature. The mixture
was heated to 90°C under stirring and hold on 90°C until the pH
Cu/HSZ-IW
Cu/HSZ-AE
4.79
4.74
2.80
2.25
296
304
3.36
2.66
[a] Calculated by ICP-OES. [b] Average Cu particle size was calculated by
value of the suspension decreased to 7. Then, the product was
filtered and washed by deionized water for several times. The
HAADF/STEM images. [c] Determined by BET method. [d] The content of
carbon deposition was determined by TG.
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7
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obtained solid was dried at 100°C for 24 h and calcined in air at
Catalytic activity test:
4
80°C for 10 h.
All evaluation experiments were carried out in a continuous flow
fixed bed reactor with a stainless steel tube (8 mm inner diameter).
In each test, 1 g of catalyst were diluted using 5.0 g of quartz sand
with identical mesh size and then loaded into the middle of the
Catalyst characterization: X-ray diffraction (XRD) patterns were
measured with a Bruker D8 ADVANCE X-ray diffractometer using Cu
Kα radiation at λ=0.154 nm. The SEM and TEM images were
collected using Thermo Sicentifc Verios G4 UC scanning electronic
microscope and ThermoFisher Talos F200X transmission electron
microscope, respectively. The compositions of the samples were
determined using a Rigaku ZSX Primus II X-ray fluorescence
reactor by glass wool. The catalyst was reduced in situ at 300°C for
À 1
5 h in flowing H with a rate of 20 mL·min . After the reactor was
2
cooled to the 140°C, the temperature was maintained at 140°C
and the pressure of H was increased from 0.1 MPa to 2.0 MPa. A
2
instrument. The N physisorption isotherms at 77 K were measured
mixture of HMF or BHMF and ethanol (HMF concentration of
2
À 1
À 1
using a Micromeritics ASAP-2020 instrument. The compositions of
the sample were determined by the inductively coupled plasma
optical emission spectrometer (ICP-OES).
2 g·L ) was then fed into the reactor (WHSV=0.05 h ) with a co-
À 1
feeding H flow of 20 mL·min . The liquid phase products were
2
collected in the gas-liquid separator using cold trap. The reaction
products were periodically extracted from the separator. Qualitative
analysis of products was performed using an Agilent 7890B–5977A
GC-MS instrument combined with an Agilent DB-wax capillary
column. Quantitative analysis of products was performed using an
Agilent 1260 HPLC Infinity instrument equipped with an ultraviolet
NH temperature-programmed desorption (NH -TPD) of the sample
3
3
was conducted using a Tianjin XQ TP-5076 instrument equipped
with a Hiden QGA mass spectrum detector. 0.1 g of the sample was
first reduced at 300°C for 5 h in the flow of 8% H /Ar mixed gas.
2
After the sample was cooled to 100°C in an Ar gas flow, the 5%
(
UV) detector and an Agilent C18 column. Quantitative analysis of
NH /Ar mixed gas was introduced for 1 h. NH desorption was
3
3
HMF and EMF was performed with UV detector at 278 nm, a
measured between 100 and 650°C with a heating rate of
mixture of trifluoroacetate aqueous solution and methanol [70:30
À 1
1
0°Cmin .
À 1
(
v/v)] was used as the mobile phase at a flow rate of 0.8 mL·min ,
and the column temperature was maintained at 40
°
C. Quantitative
The dispersion of the sample was determined by N O chemisorp-
2
tion. The sample was firstly reduced in 8% H /Ar mixture at 300°C
analysis of BHMF, EMFA, and BEMF was performed with UV detector
at 220 nm, a mixture of trifluoroacetate aqueous solution and
methanol [45:55 (v/v)] was used as the mobile phase at a flow rate
2
for 2 h. The amount of H consumed was monitored by TCD and
2
labeled as A. After the sample was cooled to 50°C in the flow of Ar,
À 1
the pure N O was introduced for 60 min to oxidize the surface
of 1.0 mL·min , and the column temperature was maintained at
2
40
°
C. The other by-products were analyzed by an off-line gas-
copper atoms. Then, the reduction of surface Cu O was conducted
2
in 8% H /Ar mixture at 300°C for 2 h. The amount of H consumed
chromatography (GC8860, Agilent, USA) using a capillary column
DB-wax and an FID detector.
2
2
was recorded by TCD and denoted as B. The dispersion (D ) of
Cu
metallic copper, exposed Cu specific surface (S ) and copper
Cu
[
27,32]
particle size (d ) were calculated from Equations (1)–(3):
Cu
DCu ¼ ð2 ꢀ BÞ=A ꢀ 100 %
(1) Acknowledgements
SCu ¼ ð2 ꢀ B ꢀ N Þ=ðA ꢀ M ꢀ 1:46 ꢀ 1019Þ
(2)
(3)
A
Cu
This work was financially supported by Zhejiang Provincial
Natural Science Foundation of China (LR16B030001,
LQ19B060002, LY19B030003), the Key Research Program of
Frontier Sciences of CAS (No. QYZDB-SSW-JSC037), K. C. Wong
Education Foundation (rczx0800), Fujian Institute of Innovation of
Chinese Academy of Sciences (FJCXY18020202), Ningbo Municipal
Bureau of Science and Technology (2019B10096, 2019A610029,
dCu ¼ 6=ðSCu ꢀ 1 Þ ¼ 0:5 ꢀ A=B
Cu
23
À 1
where NA is Avogadro’s constant (6.02×10 atoms·mol ), M is
Cu
À 1
19
the molar mass of copper (63.546 g·mol ), 1.46×10 is the
2
number of copper atoms per m , and 1 is the density of copper
8.92 g/cm ).
Cu
3
(
2
018B10056), Zhejiang Provincial Key Research and Development
Pyridine adsorption Fourier-transform infrared (Py-IR) was con-
ducted using a Bruker Vertex 70 FT-IR spectrometer. Firstly, the
sample was pressed into a wafer and then heat-treated in an Ar
Program (2021C01062).
À 1
flow (25 mL·min ) at 400°C for 1 h. After cooling down to room
temperature, the IR spectrum of the sample was recorded. Then,
the pyridine was introduced into the cell at room temperature for
Conflict of Interest
1
1
h. The IR spectrum was collected after evacuation at 350°C for
The authors declare no conflict of interest.
h.
H -TPR of the samples was conducted using an Auto ChemII2920
instrument equipped with a TCD detector. The sample was heat-
2
Keywords: 5-Hydroxymethylfurfural
·
Hydrogenation
·
treated in He flow at 200°C for 1 h and then cooled to room
Etherification · 2,5-Bis(ethoxymethyl)furan · Bifunctional catalyst
temperature. A gas mixture of 8% H in He was shifted, and the
hydrogen consumption was recorded by TCD from 30°C to 300°C
2
À 1
with a heating rate of 10°Cmin .
[
[
1] a) R. A. Sheldon, Green Chem. 2014, 16, 950–963; b) O. Ellabban, H. Abu-
Rub, F. Blaabjerg, Renewable Sustainable Energy Rev. 2014, 39, 748–764;
c) R. R. Chen, J. Y. Xin, D. X. Yan, H. X. Dong, X. M. Lu, S. J. Zhang,
ChemSusChem 2019, 12, 2715–2724.
2] a) A. A. Rosatella, S. P. Simeonov, R. F. M. Frade, C. A. M. Afonso, Green
Chem. 2011, 13, 754–793; b) Z. Y. Nakagawa, M. Tamura, K. Tomishige,
ACS Catal. 2013, 3, 2655–2668; c) I. Thapa, B. Mullen, A. Saleem, C.
Leibig, R. T. Baker, J. B. Giorgi, Appl. Catal. A 2017, 539, 70–79; d) W.
Thermogravimetry (TG) was evaluated by a Perkin-Elmer Pyris
Diamond apparatus using a temperature ramp from 30 to 800°C
À 1
with a heating rate of 10°Cmin in an air atmosphere.
ChemCatChem 2021, 13, 1–10
www.chemcatchem.org
8
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��
These are not the final page numbers!

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doi.org/10.1002/cctc.202100489
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Cheng, B. Saha, D. G. Vlachos, ChemSusChem 2018, 11, 3609–3617;
[16] K. K. Zhu, J. M. Sun, J. Liu, L. Q. Wang, H. Y. Wan, J. Z. Hu, Y. Wang,
C. H. F. Peden, Z. M. Nie, ACS Catal. 2011, 1, 682–690.
e) P. L. Zhang, J. Yang, H. L. Hu, D. X. Hu, J. Gan, Y. X. Zhang, C. L. Chen,
X. Q. Li, L. Wang, J. Zhang, Catal. Sci. Technol. 2020, 10, 4684–4692.
3] a) E. R. Sacia, M. Balakrishnan, A. T. Bell, J. Catal. 2014, 313, 70–79;
b) J. D. Lewis, S. Van de Vyver, A. J. Crisci, W. R. Gunther, V. K. Michaelis,
R. G. Griffin, Y. Román-Leshkov, ChemSusChem 2014, 7, 2255–2265; c) L.
Hu, L. Lin, Z. Wu, S. Y. Zhou, S. J. Liu, Renewable Sustainable Energy Rev.
[17] a) A. Bansode, B. Tidona, P. R. von Rohr, A. Urakawa, Catal. Sci. Technol.
2013, 3, 767–778; b) C. Z. Li, J. S. Ma, Z. H. Xiao, S. B. Hector, R. K. Liu,
S. M. Zuo, X. F. Xie, A. H. Zhang, H. Wu, Q. Liu, Fuel 2018, 218, 59–66.
[18] a) N. Suárez, J. Pérez-Pariente, F. Mondragón, A. Moreno, Microporous
Mesoporous Mater. 2019, 280, 144–150; b) L. Chen, X. M. Zhang, Q. Han,
L. J. Xu, S. Y. Zhang, Y. Y. Yuan, L. Xu, Appl. Catal. A 2020, 598, 117588.
[19] K. H. Chung, D. R. Chang, B. G. Park, Bioresour. Technol. 2008, 99, 7438–
7443.
[
2
017, 74, 230–257; d) J. N. Wei, X. J. Cao, T. Wang, H. Liu, X. Tang, X. H.
Zeng, Y. Sun, T. Z. Lei, S. J. Liu, L. Lin, Catal. Sci. Technol. 2018, 8, 4474–
484.
4
[
4] a) F. F. Yang, S. G. Zhang, Z. C. Zhang, J. B. Mao, S. M. Li, J. M. Yin, J. X.
Zhou, Catal. Sci. Technol. 2015, 5, 4602–4612; b) G. Raveendra, A.
Rajasekhar, M. Srinivas, P. S. S. Prasad, N. Lingaiah, Appl. Catal. A 2016,
[20] S. Wang, Z. Huang, Y. J. Luo, J. H. Wang, Y. Fang, W. M. Hu, Y. H. Yue,
H. L. Xu, W. Shen, Catal. Sci. Technol. 2020, 10, 6562–6572.
[21] H. Wang, R. N. Xu, Y. Jin, R. D. Zhang, Catal. Today 2019, 327, 295–307.
[22] a) M. Bjørgen, F. Joensen, M. S. Holm, U. Olsbye, K. Lillerud, S. Svelle,
Appl. Catal. A 2008, 345, 43–50; b) K. Sadowska, A. Wach, Z. Olejniczak,
P. Kuśtrowski, J. Datka, Microporous Mesoporous Mater. 2013, 82–88;
c) S. J. You, E. D. Park, Microporous Mesoporous Mater. 2014, 186,121–
129.
5
20, 105–113; c) P. Lanzafame, K. Barbera, G. Papanikolaou, S.
Perathoner, G. Centi, M. Migliori, E. Catizzone, G. Giordano, Catal. Today
018, 304, 97–102.
5] a) J. Jae, E. Mahmoud, R. F. Lobo, D. G. Vlachos, ChemCatChem 2014, 6,
08–513; b) H. Nguyen, N. Xiao, S. Daniels, N. Marcella, J. Timoshenko,
2
[
[
[
5
A. Frenkel, D. G. Vlachos, ACS Catal. 2017, 7, 7363–7370.
6] a) Q. Cao, W. Y. Liang, J. Guan, L. Wang, Q. Qu, X. Z. Zhang, X. C. Wang,
X. D. Mu, Appl. Catal. A 2014, 481, 49–53; b) T. A. Natsir, S. Shimazu, Fuel
Process. Technol. 2020, 200, 106308.
[23] a) C. A. Emeis, J. Catal. 1993, 141, 347–354; b) H. L. Hu, J. H. Lyu, J. Y. Rui,
J. Cen, Q. F. Zhang, Q. T. Wang, W. W. Han, X. N. Li, Catal. Sci. Technol.
2016, 6, 2647–2652.
[24] a) F. Benaliouche, Y. Boucheffa, P. Ayrault, S. Mignard, P. Magnoux,
Microporous Mesoporous Mater. 2008, 111, 80–88; b) S. R. Wang, W. W.
Guo, L. J. Zhu, H. X. Wang, K. Z. Qiu, K. F. Cen, J. Phys. Chem. C 2015, 119,
7] a) M. Chatterjee, T. Ishizaka, H. Kawanami, Green Chem. 2014, 16, 4734–
4739; b) J. Han, Y. Kim, B. Y. Jung, S. Y. Hwang, J. Jegal, J. W. Kim, Y. Lee,
5
24–533.
25] H. W. Zhang, H. R. Tan, S. Jaenicke, G. K. Chuah, J. Catal. 2020, 389, 19–
8.
26] C. C. Chen, L. Lin, R. P. Ye, M. L. Sun, J. X. Yang, F. Li, Y. G. Yao, J. Catal.
020, 389, 421–431.
RSC Adv. 2016, 6, 93394–93397; c) M. Balakrishnan, E. R. Sacia, A. T. Bell,
Green Chem. 2012, 14, 1626–1634; d) M. Musolino, M. J. Ginés-Molina, R.
Moreno-Tost, F. Aricò, ACS Sustainable Chem. Eng. 2019, 7, 10221–
[
[
[
2
10226; e) Y. F. Zhu, X. Kong, H. Y. Zheng, G. Q. Ding, Y. L. Zhu, Y. W. Li,
2
Catal. Sci. Technol. 2015, 5, 4208–4217.
27] H. Du, X. Y. Ma, P. F. Yan, M. Jiang, Z. Zhao, Z. C. Zhang, Fuel Process.
Technol. 2019, 193, 221–231.
[
8] D. X. Hu, H. L. Hu, H. Zhou, G. Z. Li, C. L. Chen, J. Zhang, Y. Yang, Y. P.
Hu, Y. J. Zhang, L. Wang, Catal. Sci. Technol. 2018, 8, 6091–6099.
9] a) H. L. Hu, D. X. Hu, H. T. Jin, P. L. Zhang, G. Z. Li, H. Zhou, Y. Yang, C. L.
Chen, J. Zhang, L. Wang, ChemCatChem 2019, 11, 2179–2186; b) W. T.
Fang, H. L. Hu, P. Dong, Z. S. Ma, Y. L. He, L. Wang, Y. J. Zhang, Appl.
Catal. A 2018, 565, 146–151; c) D. X. Hu, H. L. Hu, H. T. Jin, P. L. Zhang,
Y. H. Hu, S. H. Ying, X. M. Li, Y. Yang, J. Zhang, L. Wang, Appl. Catal. A
[
[
28] F. F. Cai, W. Zhu, G. M. Xiao, Catal. Sci. Technol. 2016, 6, 4889–4900.
29] J. Florek-Milewska, P. Decyk, M. Ziolek, Appl. Catal. A 2011, 393, 215–
[
224.
[
30] a) R. Alamillo, M. Tucker, M. Chia, Y. Pagán-Torres, J. Dumesic, Green
Chem. 2012, 14, 1413–1419; b) A. Iriondo, A. Mendiguren, M. B. Güemez,
J. Requies, J. F. Cambra, Catal. Today 2017, 279, 286–295.
2
020, 590, 117338.
10] J. Z. Chen, Y. Y. Guo, J. Y. Chen, L. Song, L. M. Chen, ChemCatChem
014, 6, 3174–3181.
11] a) C. Ju, M. R. Li, Y. M. Fang, T. W. Tan, Green Chem. 2018, 20, 4492–
499; b) Y. Y. Bai, L. Wei, M. F. Yang, H. Y. Chen, S. Holdren, G. H. Zhu,
D. T. Tran, C. L. Yao, R. C. Sun, Y. B. Pan, D. X. Liu, J. Mater. Chem. A 2018,
, 7693–7705.
[
31] a) Y. F. Zhu, X. Kong, H. Y. Zheng, G. Q. Ding, Y. L. Zhu, Y. W. Li, Catal.
Sci. Technol. 2015, 5, 4208–4217; b) B. S. Solanki, C. V. Rode, Green Chem.
[
[
2
2
019, 21, 6390–6406; c) K. T. V. Rao, Y. L. Hu, Z. S. Yuan, Y. S. Zhang,
C. B. C. Xu, Appl. Catal. A 2021, 609, 117892.
4
[
32] S. X. Xia, R. F. Nie, X. Y. Lu, L. Wang, P. Chen, Z. Y. Hou, J. Catal. 2012,
296, 1–11.
6
[12] J. N. Wei, T. Wang, X. J. Cao, H. Liu, X. Tang, Y. Sun, X. H. Zeng, T. Z. Lei,
S. J. Liu, L. Lin, Appl. Catal. B 2019, 258, 117793.
[
13] a) N. Künzle, R. Hess, T. Mallat, A. Baiker, J. Catal. 1999, 186, 239–241;
b) S. Lima, D. Chadwick, K. Hellgardt, RSC Adv. 2017, 7, 31401–31407.
14] H. V. Koningsveld, J. C. Jansen, H. V. Bekkum, Zeolites 1990, 10, 235–242.
15] S. Goodarznia, K. J. Smith, J. Mol. Catal. A 2010, 320, 1–13.
Manuscript received: April 3, 2021
Revised manuscript received: May 10, 2021
Version of record online: ■■■, ■■■■
[
[
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Bifunctional catalyst: The highly-
efficient conversion of 5-
Dr. H. Hu, T. Xue, Z. Zhang, J. Gan, L.
Chen, Prof. J. Zhang*, Prof. F. Qu,
Prof. W. Cai*, Prof. L. Wang*
hydroxymethylfurfural (HMF) to 2,5-
bis(ethoxymethyl)furan (BEMF) was
achieved by using the copper-loaded
hierarchically structured ZSM-5 (Cu/
HSZ) catalysts in the continuous
fixed-bed reactor.
1
– 10
Direct Conversion of 5-
Hydroxymethylfurfural to Furanic
Diether by Copper-Loaded Hier-
archically Structured ZSM-5 Catalyst
in a Fixed-Bed Reactor