Double-metal cyanide-supported Pd catalysts for highly efficient hydrogenative ring-rearrangement of biomass-derived furanic aldehydes to cyclopentanone compounds

Article abstract of DOI:10.1016/j.jcat.2019.08.036

The hydrogenative ring-rearrangement of biomass-derived furanic aldehydes (furfural or 5-hydroxymethyl furfural) to cyclopentanone compounds (cyclopentanone or 3-hydroxymethyl cyclopentanone) is of great significance for high-value chemicals. The Br?nsted acid in metal-support bifunctional catalysts causes a serious carbon loss, and the weak Lewis acid is difficult to induce hydrolysis reaction steps. Here, a double-metal cyanide (DMC) catalyst with pure moderate Lewis acid sites was investigated for solving the above problems. The crystal structure and the Lewis acidity of the catalyst are controlled by different kinds of metals, and the surface properties are changed by a complexing effect. Pd clusters of 8 nm are uniformly dispersed on the surface after impregnation on the double-metal cyanide. For the reaction of furanic aldehydes, the Pd/FeZn-DMC catalyst with a moderate Lewis acidity shows a high efficiency for the synthesis of cyclopentanone compounds, whereas the Pd/FeNi-DMC and Pd/FeCo-DMC catalysts with a weak Lewis acidity result in a yield above 90.2% of furanic alcohols (furfuryl alcohol or 2,5-bis(hydroxymethyl)furan). The catalytic activity of Pd/FeZn-DMC is controlled by the surface area based on the accessibility of the Lewis acid sites, and the highest yields of 96.6% and 87.5% are obtained for cyclopentanone and 3-hydroxymethyl cyclopentanone, respectively. Furthermore, the catalyst is resistant to leaching and performs stably after 6 runs. This study not only provides a promising route for efficient production of cyclopentanone compounds but also shows the excellent advantage of DMC-based bifunctional catalysis in biomass conversion reactions.

Full text of DOI:10.1016/j.jcat.2019.08.036

Journal of Catalysis 378 (2019) 201–208
Contents lists available at ScienceDirect
Journal of Catalysis
journal homepage: www.elsevier.com/locate/jcat
Double-metal cyanide-supported Pd catalysts for highly efficient
hydrogenative ring-rearrangement of biomass-derived furanic
aldehydes to cyclopentanone compounds
Xiang Li a,b,1, Qiang Deng a,b, ,1, Shihong Zhou a,b, Jiedong Zou a,b, Jun Wang a,b, Rong Wang a,b
,
⇑
Zheling Zeng a,b, Shuguang Deng a,b,c,
⇑
a Key Laboratory of Poyang Lake Environment and Resource Utilization, Nanchang University, Ministry of Education, Nanchang 330031, PR China
b School of Resource, Environmental and Chemical Engineering, Nanchang University, Nanchang 330031, PR China
c School for Engineering of Matter, Transport and Energy, Arizona State University, 551 E. Tyler Mall, Tempe, AZ 85287, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
The hydrogenative ring-rearrangement of biomass-derived furanic aldehydes (furfural or
5-hydroxymethyl furfural) to cyclopentanone compounds (cyclopentanone or 3-hydroxymethyl
cyclopentanone) is of great significance for high-value chemicals. The Brønsted acid in metal-support
bifunctional catalysts causes a serious carbon loss, and the weak Lewis acid is difficult to induce hydrol-
ysis reaction steps. Here, a double-metal cyanide (DMC) catalyst with pure moderate Lewis acid sites was
investigated for solving the above problems. The crystal structure and the Lewis acidity of the catalyst are
controlled by different kinds of metals, and the surface properties are changed by a complexing effect. Pd
clusters of 8 nm are uniformly dispersed on the surface after impregnation on the double-metal cyanide.
For the reaction of furanic aldehydes, the Pd/FeZn-DMC catalyst with a moderate Lewis acidity
shows a high efficiency for the synthesis of cyclopentanone compounds, whereas the Pd/FeNi-DMC
and Pd/FeCo-DMC catalysts with a weak Lewis acidity result in a yield above 90.2% of furanic alcohols
(furfuryl alcohol or 2,5-bis(hydroxymethyl)furan). The catalytic activity of Pd/FeZn-DMC is controlled
by the surface area based on the accessibility of the Lewis acid sites, and the highest yields of 96.6%
and 87.5% are obtained for cyclopentanone and 3-hydroxymethyl cyclopentanone, respectively.
Furthermore, the catalyst is resistant to leaching and performs stably after 6 runs. This study not only
provides a promising route for efficient production of cyclopentanone compounds but also shows the
excellent advantage of DMC-based bifunctional catalysis in biomass conversion reactions.
Received 29 January 2019
Revised 16 August 2019
Accepted 22 August 2019
Keywords:
Furanic aldehydes
Pd/DMC
Hydrogenative ring-rearrangement
Cyclopentanone compounds
High-value chemicals
Ó 2019 Elsevier Inc. All rights reserved.
1. Introduction
the excessive dependence on petroleum and extend the application
of biomass, the synthesis of biomass-based fine chemicals has
Cyclopentanone
compounds
(cyclopentanone
or
attracted great attention [4,5]. Lignocellulose, the most abundant
organic substance in nature, can be transformed into biomass plat-
form furanic aldehydes (furfural or 5-hydroxymethyl furfural),
which play an important role in the catalytic conversion of biomass.
Recently, the hydrogenative ring-rearrangement of furanic
aldehydes to cyclopentanone compounds was widely reported
under Group VIII or IB metal supported bifunctional catalysts in
aqueous solutions, and the whole reactions were through C@O
hydrogenation, furan ring hydrolysis, C@C hydrogenation,
intramolecular aldol, and dehydration reaction steps [6,7]. It is
confirmed that Lewis acids have a crucial effect on the hydrogena-
tive ring-rearrangement reaction by promoting the hydrolysis and
intramolecular aldol steps, but Brønsted acids easily promote the
intermolecular CAC bond reaction of intermediates, leading to
3-hydroxymethyl cyclopentanone) are important intermediates
for fine chemicals, which can be used for the synthesis of medicines,
spices, pesticides, dyes, rubber and high-density fuels [1,2].
Currently, cyclopentanone is mainly synthesized from the
decarboxylation cyclization of petroleum-derived adipic acid [3].
However, 3-hydroxymethyl cyclopentanone has not been industri-
ally synthesized from petroleum-derived chemicals yet. To reduce
⇑
Corresponding authors at: Key Laboratory of Poyang Lake Environment and
Resource Utilization, Nanchang University, Ministry of Education, Nanchang
330031, PR China.
E-mail addresses: dengqiang@ncu.edu.cn (Q. Deng), Shuguang.Deng@asu.edu (S.
Deng).
1
These authors contributed equally to this work.
https://doi.org/10.1016/j.jcat.2019.08.036
0021-9517/Ó 2019 Elsevier Inc. All rights reserved.

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X. Li et al. / Journal of Catalysis 378 (2019) 201–208
the production of humins [8]. Up to now, many acidic materials,
such as acidic metal oxides (including TiO2, ZnO, Co3O4, Al2O3)
and acidic molecular sieves (including HY, HZSM-5, SBA-15), were
used as supports for the furfural reaction [1,9–15]. Meanwhile,
unlike furfural, a stronger acidic support (Ta2O5, Nb2O5) is needed
for 5-hydroxymethyl furfural because its hydrogenation interme-
diate 2,5-bis(hydroxymethyl)furan is more difficult to hydrolyze
because of the electron withdrawing hydroxymethyl group
[16–18]. Unfortunately, under the coexisting action of Lewis and
Brønsted acids on the traditional supports, the synthesis efficiency
of cyclopentanone compounds is unsatisfactory, because
a large amount of intermediates (furfuryl alcohol or 2,5-bis-
(hydroxymethyl)furan) and low-value humins are generated. It
has been reported that the pure Lewis acidic Cr-MIL-101-based
catalyst completely prevents the generation of humins and shows
a considerable yield of cyclopentanone over 60% from furfural [19].
However, because of the weak Lewis acidity of the unsaturated
coordination of Cr3+ ions, it can only catalyze 5-hydroxymethyl
furfural to 2,5-bis(hydroxymethyl)tetrahydrofuran, and cannot
further open the furan ring and trigger the synthesis of
3-hydroxymethyl cyclopentanone [19]. Therefore, to efficiently
synthesize cyclopentanone compounds, the synthesis of pure
moderate Lewis acidity materials as the support is important.
Double-metal cyanides (DMCs), famous for Prussian blue, are
constructed by octahedral metal cyanide anion groups bridged
with metal ions through a cyanide group (C„N). It is safe for
human health.[20] It shows wide prospects in adsorption [21],
energy storage [22], biomedicine [23] and catalysis [24,25].
Usually, triblock copolymers as a complexing agent were added
in the synthesis process to suppress overgeneration and thus
adjust the surface area. Meanwhile, the structure of DMCs can be
easily controlled by different metals. For instance, FeZn-DMC is
prone to having a rhombohedral lattice structure with an R-3c
space group. However, FeNi-DMC and FeCu-DMC have a cubic
structure with an Fm3m space group although the synthesis condi-
tions are the same [26]. On the inner and outer surface edges of a
DMC crystal, the coordination unsaturated vacancy M2+ ions can be
used as Lewis acid sites. At present, as a monofunctional Lewis
acidic catalyst, DMCs are mainly used to catalyze polymerization
[27], esterification [28], transesterification [28,29], polyesterifica-
tion [30], hydroamination [31], Prins condensation [32] and
oxidation reactions [33]. Especially, they have industrial
applications on the polymerization of epoxides based on their high
activity, stability and low price. To the best of our knowledge,
DMCs have not been reported in the field of bifunctional catalysis
up to now.
nickel chloride (NiCl2Á6H2O) and cobalt chloride (CoCl2Á6H2O),
tert-butanol, palladium chloride (PdCl2), TiO2, Nb2O5, and Al2O3
were purchased from Sinopharm Chemical Reagent Company.
5-Hydroxymethyl furfural (99%) was obtained from Beijing Cou-
pling Technology Company. Poly(ethyleneglycol)-block-poly(pro
pylene glycol)-block-poly-(ethylene glycol) (P123, average molecu-
lar weight = 5800) was purchased from Sigma-Aldrich. All chemi-
cals were used without further purification. Hb (SiO2/Al2O3 = 25)
supplied by Tianjin Nankai Catalysts Company was calcined in air
for 6 h at 550 °C. Al-MCM-41 (SiO2/Al2O3 = 26.8) and Cr-MIL-101
were synthesized according to previous studies [2,34].
2.2. Synthesis of catalysts
FeZn DMC was synthesized by a simple precipitation method. A
mixture of 0.1 mol ZnCl2, 20 mL water and 20 mL tert-butanol was
added to 40 mL 0.25 mol/L K4Fe(CN)6Á3H2O aqueous solution
slowly over 1 h at 50 °C under vigorous stirring. Then, quantitative
amounts of P123 in 2 mL water and 40 mL tert-butanol were added
over 10 min and stirred continuously for 1 h. Subsequently, the
solid was centrifuged and washed with water to remove the
uncompleted ions and complexing agent, followed by drying at
60 °C for 8 h. The amounts of P123 were 0, 5, 10, and 15 g, and
the resultant white solids were labeled FeZn-0, FeZn-5, FeZn-10,
and FeZn-15, respectively. As a comparison, some small particles
of FeZn-0 were ball-milled in an agate grinding jar for 30 min
and labeled FeZn-0B. Similarly, dark green FeCo and green FeNi
solids were synthesized with 15 g P123 by changing ZnCl2 to NiCl2-
Á6H2O and CoCl2Á6H2O and labeled FeNi-15 and FeCo-15,
respectively.
A series of supported Pd catalysts was prepared by the incipient
wetness impregnation method. Typically, given amounts of PdCl2
and 1 g DMC were added to 10 mL water, thoroughly mixed, and
dried at 80 °C over a rotary evaporator. The solid was recovered,
dried at 100 °C for 6 h, and reduced in a quartz tube furnace at
300 °C for 3 h under a gas mixture of 10% H2/90% N2. If not men-
tioned, the Pd loading is 5 wt%.
2.3. Catalyst characterizations
The crystal structures of the catalysts were studied by powder
X-ray diffraction (XRD) using a PANalytical Empyrean diffractome-
ter with Cu-Ka radiation. The pore textural properties were mea-
sured by N2 adsorption-desorption at À196 °C on an ASAP 2046
surface analyzer. The specific surface area was calculated by the
BET method. Morphologies were obtained with a JSM-6701F scan-
ning electron microscope and a JEM-2100 transmission electron
microscope. Acid properties were analyzed by the infrared spec-
troscopy of adsorbed pyridine using a Bruker VERTEX 70 spectrom-
eter. For the IR analysis, self-supported wafers (10 mg/cm2) were
degassed for 1 h under vacuum at 200 °C, then the adsorption of
pyridine proceeded at 60 °C for 30 min followed by desorption at
150 °C and 250 °C for 20 min, and the transmission spectra were
recorded. Elemental analysis was carried out using Inductively
Coupled Plasma Optical Emission Spectrometry on a PerkinElmer
Optima 8000 spectrometer. The thermal stabilities were analyzed
by thermal gravimetric analysis on a NETZSCH-STA 2500 instru-
ment in a N2 atmosphere.
Here, we focus on Lewis acidic DMC-supported Pd nanoparticle
bifunctional catalysts as a highly efficient catalyst for the hydro-
genative ring-rearrangement of furanic aldehydes. These catalysts
show a controllable Lewis acidity and surface by adjusting the
structure and the amount of the complexing agent. As a result,
the Pd/FeZn-DMC catalysts show a higher activity and selectivity
to cyclopentanone compounds than traditional catalysts, which is
attributed to the appropriate Pd particle size, pure moderate Lewis
acidity, and suitable accessibility of active sites. Moreover, it is
highly stable against leaching and shows an unchanged perfor-
mance after six runs. The DMC-based bifunctional catalysis is
promising in the catalytic transformation of biomass derivatives.
2.4. Catalytic reactions
2. Experimental
The catalytic reactions were carried out in a 100 mL batch auto-
clave (Parr Instrument) equipped with mechanical stirring. Typi-
cally, a mixture of furanic aldehydes (10.4 mmol) and water
(40 mL) and 0.1 g catalyst were added to the autoclave, then
reacted under 4.0 MPa H2 at 150 °C and sampled periodically. Then,
2.1. Materials
Furfural (99.5%), N,N-dimethyl formamide, ethanol, potassium
hexacyanoferrate(II) (K4[Fe(CN)6]Á3H2O), zinc chloride (ZnCl2),

X. Li et al. / Journal of Catalysis 378 (2019) 201–208
203
a certain amount of N,N-dimethyl formamide was added as an
internal standard substance. The products were analyzed by an
Agilent 6890 N GC/5973 MS detector and quantified by a Trace
1300 gas chromatograph equipped with an FID detector and a
TG-WAXMS capillary column (30 m  0.32 mm). The reported data
were the mean values of three trials with small error bars.
3. Results and discussion
3.1. Structural characteristics of Pd/DMC
Fig. 1A shows the XRD patterns of the DMC. It is found that the
DMC is consistent with the uniform K2M3[Fe(CN)6]2 (M = Zn2+, Ni2+
,
Co2+) structure type, which suggests that FeZn has an R-3c space
group structure in which Zn2+ is tetra-coordinated connecting with
four N„C bonds. Differently, FeNi and FeCo have an Fm3m space
structure, and Ni/Co is hexa-coordinated connecting with four
N„C bonds and two water molecules, which is in good agreement
with the reported results [35,36]. The addition of P123 reduces the
crystalline intensity slightly, because the complexing agent pre-
vents the DMC from growing largely. However, the ball-milled
sample FeZn-0B has greatly destroyed the crystalline structure by
reducing the crystal particle size. After impregnation, the XRD pat-
terns are almost identical to the pure DMC, confirming the well
preservation of the DMC structure after the incorporation of Pd
(Fig. 1B).
Elemental analysis shows the Pd content on Pd/DMC catalysts is
5.0 wt% via the impregnation method (Table 1). The Zn:Fe molar
ratio is 1.57:1 for Pd/FeZn-0, meaning that the Zn:Fe ratio is
slightly higher than the stoichiometrically expected 1.5. Because
of the excess of Zn2+ in the synthesis mixture, it is indicated that
zinc terminates the crystals and is abundant on the outer surface.
Meanwhile, the addition of P123 suppresses overgenaration and
increases Zn:Fe molar ratio from 1.57 to 1.80 for Pd/FeZn [31].
Fig. 2 shows the N2 adsorption-desorption isotherms of Pd/DMC
catalysts. Pd/FeZn-0 shows a type II adsorption-desorption iso-
therm, and Pd/FeZn-5, 10, and 15 slightly show a type IV isotherm,
Fig. 2. N2 adsorption isotherms of Pd/DMC.
indicating the existence of mesopores after introducing the organic
complexing agents. The controllable BET surface area, pore volume
and pore size range from 10.3 to 26.8 m2/g, 0.034 to 0.040 cm3/g,
and 18.0 to 24.2 nm, respectively, for Pd/FeZn-0 to Pd/FeZn-15 by
adjusting the amount of P123 (Table 1). Meanwhile, the simple
ball-milled Pd/FeZn-0B also shows a type IV isotherm with a BET
surface of 27.6 m2/g by decreasing the crystal particle size. Cubic
FeNi-15 and FeCo-15 have a larger BET surface of 85.2 and
75.3 m2/g, respectively (Fig. S1).
The SEM image shows that the DMC has very uniformly sized
particles of 1–2 mm, and the particle size did not change by adding
complexing agents (Fig. 3A–C), except for the ball-milled sample
Pd/FeZn-0B with a smaller size. The presence of well dispersed
Pd nanoparticles of approximately 8 nm was observed on the sur-
face of the FeZn-DMC host, without any aggregation (Fig. 3D–F).
The FeNi-DMC and FeCo-DMC show Pd nanoparticles of about
9 nm. As a comparison, other acidic materials supported Pd (Pd/
C, Pd/Hb, Pd/Al-MCM-41, Pd/Al2O3, Pd/Nb2O5, Pd/TiO2, Pd/MIL-
Fig. 1. X-ray diffraction patterns of (A) DMC and (B) Pd/DMC.
Table 1
Physical properties of the synthesized catalysts. a: after 6 catalytic runs.
Samples
SBET (m2/g)
Pore volume (cm3/g)
Pore Size (nm)
Zn:Fe (molar ratio)
Pd content (wt%)
Pd/FeZn-0B
Pd/FeZn-0
Pd/FeZn-5
Pd/FeZn-10
Pd/FeZn-15
Pd/FeZn-15a
27.6
10.3
13.2
14.9
26.8
18.6
0.081
0.036
0.034
0.038
0.040
0.038
24.9
18.0
19.1
20.8
24.2
21.6
1.62:1
1.57:1
1.65:1
1.73:1
1.80:1
1.75:1
4.98
4.96
5.01
4.97
4.95
4.93

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X. Li et al. / Journal of Catalysis 378 (2019) 201–208
Fig. 3. SEM and TEM micrographs of (A) FeZn-0, (B) FeZn-15, (C) FeZn-0B, (D) Pd/FeZn-15, (E) Pd/FeNi-15 and (F) Pd/FeCo-15.
101) shows smaller Pd nanoparticles ranged from 3 to 6 nm
(Fig. S2). As shown in Fig. S3, pyridine-adsorbed FTIR spectra were
used to detect the acid sites. Adsorption peaks are observed at
1450 cmÀ1 for all the samples. Meanwhile, no peaks are observed
at 1540 cmÀ1. This confirms a pure Lewis support without any
Brønsted acids. Notably, the area of the most intensive peak
(1450 cmÀ1) is well associated with the BET surface area for the
sample treated at 150 °C (Fig. 4), with Pd/FeZn-0 at 150 °C as a
baseline, because a larger area is more likely to expose more acid
sites that adsorb more pyridine [30]. However, at the higher
adsorption temperature (250 °C), due to the strong Lewis acidity
in the catalyst, the signal of Pd/FeZn is higher than that of Pd/FeCo
and Pd/FeNi, showing a stronger Lewis acidity of tetra-coordinated
unsaturated Zn2+. Meanwhile, with the increase in desorption tem-
peratures, the amount of the adsorbed pyridine in all Pd/FeZn sam-
ples was synchronously decreased, showing that the introduction
of P123 only expands the internal structure of particles and cannot
influence their Lewis acidity. Meanwhile, as shown in Fig. S4, the
acidic molecular sieves (Hb, Al-MCM-41) show both Lewis and
Brønsted acidity.
3.2. Hydrogenative ring-rearrangement of furfural to cyclopentanone
As shown in Fig. 5A, furfural (FFA) was first converted to
furfuryl alcohol (FA) by C@O hydrogenation at the beginning, then
acid-catalytically hydrolyzed to form 2-pentene-1,4-dione
(PED) at the acid sites of the catalysts, and further generated
3-hydroxycyclopentanone (HCPO) via acid-catalytic conversion of
an
intramolecular
aldol
intermediate
4-hydroxy-2-
cyclopentenone (HCPEO) in a subsequent C@C hydrogenation
reaction. Finally, cyclopentanone (CPO) is obtained by dehydration
in a subsequent C@C hydrogenation reaction. The fact that trace
amounts of PED, HCPEO and HCPO are detected in gas chro-
matograph confirms the reaction mechanism. Meanwhile, it also
shows that the intramolecular aldol, C@C hydrogenation, and
dehydration reactions occurred quickly. Apart from the main reac-
tion pathway, there are some side reactions, including the exces-
sive hydrogenation of FFA to form tetrahydrofurfuryl alcohol
(THFA) and the intermolecular CAC bonding reaction of intermedi-
ates to form humins. Pd/DMC only shows a high hydrogenation
activity of furfural, but a low activity of hydrolyzing the furan ring.
However, FeZn-DMC does not have the catalytic activity for fur-
fural. It confirms that noble metals and acid supports play respec-
tive roles in this reaction (Fig. 6A). To promote the hydrogenation
reaction, the Pd loading is optimized, and a satisfactory activity is
achieved on a catalyst with 5 wt% Pd (Fig. S6). Fig. 5B and C show
the time-dependent product distribution over Pd/FeZn-15 and Pd/
MIL-101. Although the surface area of Pd/DMC is much lower than
that of Pd/MIL-101, it shows three obvious advantages over Pd/
MIL-101 in this reaction. First, the hydrogenation of C@O acceler-
ated significantly with the conversion of FFA, increasing from
60.5% to 99.9% within 6 h, because Pd with a uniform appropriate
particle size on the surface of the host is easily accessible by the
reactants. Second, a stronger Lewis acidity of the DMC can greatly
promote the hydrolysis of FA, with the yield of FA decreasing from
10.0% to 0.0%. Third, the hydrogenation of the furan ring is almost
completely inhibited with the yield of THFA decreasing from 4.5%
to 1.4%, because FA is quickly consumed and Pd with an appropri-
ate particle size is not conducive to the hydrogenation of the furan
ring [37,38].
The thermal stability of Pd/DMC (Fig. S5) shows that the weight
decreased from 60 °C to 200 °C by the loss of crystal and noncrystal
water. Pd/DMC retains its structure at 300 °C, indicating that it has
a great stability under severe reaction conditions.
Fig. 6A further compares the conversion and selectivity for this
reaction with several reported supports. Zeolite-based Pd/Hb and
Fig. 4. Relation between the intensity of the 1450 cmÀ1 peak and the BET surface.

X. Li et al. / Journal of Catalysis 378 (2019) 201–208
205
Fig. 5. The reaction pathway scheme (A) and the product distribution of FFA hydrogenative ring-rearrangement using Pd/FeZn-15 (B) and Pd/MIL-101 (C). Reaction
conditions: FFA (10.4 mmol), catalyst (0.1 g), water (40 mL), temperature 150 °C, 4.0 MPa H2.
Fig. 6. Hydrogenative ring-rearrangement of FFA to CPO over various often-used catalysts (A) and (B) Pd/DMC. Reaction conditions: FFA (10.4 mmol), catalyst 0.1 g, water
(40 mL), temperature 150 °C, 4.0 MPa H2, time 6 h.
Pd/Al-MCM-41 show a considerable activity of furfural hydrogena-
tion. However, THFA is generated largely, because Pd with a small
particle size prefers to promote the furan ring hydrogenation, and
the selectivity of cyclopentanone is approximately 40% [37,38].
Additionally, considerable humins are generated via the Brønsted
acid catalysis [8]. Pd/Al2O3 also mainly generates THFA and humins
by Pd with a small particle size and the Brønsted acid catalysis
[8,39]. Comparatively, although the humins cannot be avoided
completely, Pd/Nb2O5 and Pd/TiO2 have a higher selectivity to
CPO due to their more Lewis acid sites. Pd/MIL-101 shows a higher
selectivity of cyclopentanone based on the pure Lewis acidity.
However, its activity is low, because the Pd particle and the Lewis
acid sites are located in the framework of MIL-101, and hardly
accessible to the reactants [40]. These results indicate that the
selective synthesis of cyclopentanone is a challenge.
to be hydrolyzed with weak Lewis acidic sites. It is worth mention-
ing that FA cannot be transformed to THFA via furan ring hydro-
genation because Pd with an appropriate particle size in the
catalyst is hard to adsorb and convert the furan ring [37,38]. In con-
trast, Pd/FeZn with a medium-strength Lewis acidity shows a highly
efficient effect of furan ring opening and a high selectivity for
cyclopentanone (Scheme 1). In addition, the activity is increased
with the surface area of Pd/FeZn, due to the more efficient accessi-
bility of Lewis acid sites. At last, 99.9% conversion of furfural and
96.6% selectivity of cyclopentanone were obtained with Pd/FeZn-
15. Indeed, Pd/FeZn-0B shows a higher activity and selectivity than
Pd/FeZn-0 by increasing the surface area, but lower ones than Pd/
FeZn-15 due to the destruction of the crystal structure.
To clearly clarify the performance of Pd/DMC, kinetic studies
about the hydrogenation step of FFA and the hydrolysis step of
FA are carried out. For the hydrogenation study, the ln(C/C0) of
FFA against time gives good straight-line plots, which reveals that
the hydrogenation step of FFA followed pseudo first-order kinetics
(Fig. S7). Pd/DMC (Pd/FeZn, Pd/FeNi and Pd/FeCo) shows obviously
Fig. 6B shows the catalytic effect of DMC-based catalysts. Inter-
estingly, Pd/FeNi and Pd/FeCo exhibited a high furfural conversion
above 98.0% with a high selectivity toward furfuryl alcohol above
93.1% within 6 h, demonstrating that furfuryl alcohol was difficult

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X. Li et al. / Journal of Catalysis 378 (2019) 201–208
Scheme 1. Highly oriented synthesis of cyclopentanone and furfuryl alcohol via different catalysts.
higher kinetic parameters among all catalysts. For the hydrolysis
study, to eliminate the influence of furan ring hydrogenation, the
reaction is conducted without hydrogen. Pd/FeZn shows the high-
est kinetic parameters, whereas Pd/FeCo and Pd/FeNi are inactive.
These results clearly show that the excellent catalytic efficiency of
Pd/FeZn is ascribable to two advantages in the two steps.
Differently, the hydrogenation of HHED occurs to form the inter-
mediate HHD first, and then HHCPN is produced by the intramolec-
ular aldol reaction of HHD, which is transformed to HCPN finally.
2,5-Bis(hydroxymethyl)tetrahydrofuran (THBHF) was also gener-
ated by the excessive hydrogenation, as shown in Fig. 7A. Trace
amounts of HHED and HHCPN were detected in these reactions,
indicating that the C@C hydrogenation and dehydration reactions
are fast, as discussed above. Unlike furfural, many intermediates
BHF and HHD are detected in the 5-hydroxymethyl furfural reac-
tion because the hydroxymethyl group transfers electrons to the
furan ring or the carbonyl group, thus reducing the reactivity of
BHF and HHD (Fig. 7B, C). Moreover, the hydroxymethyl group
brings up the steric hindrance that also makes the reaction more
3.3. Hydrogenative ring-rearrangement of 5-hydroxymethyl furfural
to 3-hydroxymethyl cyclopentanone
Similar to furfural, 5-hydroxymethyl furfural generates 2,5-bis
(hydroxymethyl)furan (BHF) and 1-hydroxy-3-hexene-2,5-dione
(HHED) via C@O hydrogenation and hydrolysis reactions.
Fig. 7. The reaction pathway scheme (A) and the product distribution of HMF hydrogenative ring-rearrangement using Pd/FeZn-15 (B) and Pd/MIL-101 (C). Reaction
conditions: FFA (10.4 mmol), catalyst (0.1 g), water (40 mL), temperature 150 °C, 4.0 MPa H2.

X. Li et al. / Journal of Catalysis 378 (2019) 201–208
207
Fig. 8. Hydrogenative ring-rearrangement of HMF to HCPN over various often-used catalysts (A) and (B) Pd/DMC. Reaction conditions: HMF (10.4 mmol), catalyst 0.1 g, water
(40 mL), temperature 150 °C, 4.0 MPa H2, time 12 h. Pd/FeZn-15a catalyst: 24 h reaction time.
3.4. Catalyst stability and recycling
A rapid, hot-catalyst filtration test was performed, and no fur-
ther conversion of furfural and yield of cyclopentanone in the fil-
trate were found after the removal of Pd/FeZn DMC (Fig. S8),
which proves the true heterogeneously catalytic nature of each
reaction step and suggests the stability of Pd particles and the
DMC. The recycling of Pd/DMC was further evaluated in the hydro-
genative ring-rearrangement of furfural. The catalyst was cen-
trifuged after the reaction, washed with water, and used for the
next run. As shown in Fig. 9, after 6 runs, both the conversion
and the selectivity still stay above 95.1%. The slight decrease of cat-
alytic activity in catalytic kinetic can be attributed to the decrease
of specific surface area (Table 1, Fig. S9). However, the crystalline
structures, Lewis acidity, and chemical compositions are well pre-
served in the used catalyst as evidenced by the XRD, pyridine-
adsorbed FTIR and ICP-OES data (Table 1, Fig. S10, S11), showing
that the catalysts are stable under the present reaction conditions.
Fig. 9. Recycling Performance of Pd/FeZn-15 in furfural hydrogenative ring-
rearrangement. Reaction conditions: HMF (10.4 mmol), Pd/FeZn-15 (0.1 g), water
(40 mL), temperature 150 °C, 4.0 MPa H2, time 6 h.
4. Conclusions
difficult [41]. The transformation efficiency of HMF to HCPN is
lower, so the reaction time extends to 12 h. Likewise, compared
with Pd/MIL-101, Pd/DMC has a higher activity of C@O hydrogena-
tion without any hydrogenation of the furan ring. Better yet, the
DMC promotes the hydrolysis of BHF and further intramolecular
aldol reaction, whereas Pd/MIL-101 with a weak Lewis acidity can-
not open the furan ring and a large amount of BHF is produced. At
last, the reaction upgraded the conversion of HMF, which increased
from 74.9% to 93.1%, and the yield of HCPN, which increased from
2.1% to 60.2%, in 12 h by changing Pd/MIL-101 to Pd/DMC.
A highly efficient DMC-based bifunctional catalyst is developed
for the hydrogenative ring-rearrangement of biomass-derived
furanic aldehydes. Various pure Lewis acidities can be obtained
by different types of metals. Pd/DMC shows conversion of a much
higher activity and selectivity compared with traditional reported
supports. Among the catalysts studied in this work, Pd/FeZn with
a moderate pure Lewis acidity shows a yield of cyclopentanone
compounds over 87.5%, whereas Pd/FeNi and Pd/FeCo with a weak
Lewis acidity show a yield of furanic alcohols over 90.2%. A higher
conversion can be achieved with more complexing agent. In addi-
tion, Pd/DMC shows an excellent stability in recycling runs, with-
out any obvious Pd leaching and DMC structure degradation. This
study provides a promising method for the synthesis of cyclopen-
tanone and demonstrates the new prospect for the application of
DMCs as a bifunctional catalyst.
Fig. 8A also compares the activity of the various catalysts. Pd/
Al2O3, Pd/Hb and Pd/Al-MCM-41 have a high selectivity of THBHF.
Differently, Pd/Nb2O5 with a higher acidity shows a higher selectiv-
ity to HCPN than weak acidic Pd/TiO2, which further confirms that
a
strong acidity support is important for hydrolysis and
intramolecular aldol steps for the HMF reaction. Pd/MIL-101 can-
not open the furan ring, and a large amount of BHF is further
hydrogenated to THBHF by small Pd particles. Pd/FeNi and Pd/FeCo
only show a high activity of C@O hydrogenation, and BHF yields of
93.1% and 90.2% were obtained, respectively (Fig. 8B). All FeZn-
based catalysts exhibit product transformation via main reaction
routes, and there is almost no other byproducts. The selectivity
of HCPN is increased from 54.0% to 67.7% with the surface area
of Pd/FeZn-0 to Pd/FeZn-15, because more Lewis acid sites promote
HHD and BHF to be consumed via hydrolysis and intramolecular
aldol reactions. In addition, after 24 h, the conversion over
Pd/FeZn-15 is 99.9% with a selectivity of 87.5%.
Acknowledgements
The authors appreciate the supports from the National
Natural Science Foundation of China (21878138, 21706112,
21666021), Natural Science Foundation of Jiangxi Province
(20171BAB213017), Postdoctoral Science Foundation of China
(2017M622104), and the ‘‘Thousand Talents Plan” of China.
Declaration of Competing Interest
The authors declare no conflict of interest.

208
X. Li et al. / Journal of Catalysis 378 (2019) 201–208
[21] A. Takahashi, H. Tanaka, D. Parajuli, T. Nakamura, K. Minami, Y. Sugiyama, Y.
Appendix A. Supplementary material
Hakuta, S.-I. Ohkoshi, T. Kawamoto, Historical pigment exhibiting ammonia
gas capture beyond standard adsorbents with adsorption sites of two kinds, J.
Am. Chem. Soc. 138 (2016) 6376–6379.
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.jcat.2019.08.036.
[22] D. Su, M. Cortie, H. Fan, G. Wang, Prussian blue nanocubes with an open
framework structure coated with pedot as high-capacity cathodes for lithium-
sulfur batteries, Adv. Mater. 29 (2017) 1700587.
[23] L. Catala, T. Mallah, Nanoparticles of prussian blue analogs and related
coordination polymers: from information storage to biomedical applications,
Chem. Rev. 346 (2017) 32–61.
[24] N. Zhu, X. Hao, J. Ulstrup, Q. Chi, Single-nanoparticle resolved biomimetic long-
range electron transfer and electrocatalysis of mixed-valence nanoparticles,
ACS Catal. 6 (2016) 2728–2738.
[25] X. Li, J. Liu, A.I. Rykov, H. Han, C. Jin, X. Liu, J. Wang, Excellent photo-Fenton
catalysts of Fe–Co Prussian blue analogues and their reaction mechanism
study, Appl. Catal. B: Environ. 179 (2015) 196–205.
[26] M. Avila, L. Reguera, J. Rodríguez-Hernández, J. Balmaseda, Porous framework
of T2[Fe(CN)6]ÁxH2O with T=Co, Ni, Cu, Zn, and H2 storage, J. Solid State Chem.
181 (2008) 2899–2907.
[27] J. Sebastian, D. Srinivas, Effects of method of preparation on catalytic activity
of Co-Zn double-metal cyanide catalysts for copolymerization of CO2 and
epoxide, Appl. Catal. A: Gen. 482 (2014) 300–308.
[28] R. Srivastava, D. Srinivas, P. Ratnasamy, Fe-Zn double-metal cyanide
complexes as novel, solid transesterification catalysts, J. Catal. 241 (2006)
34–44.
[29] P.S. Sreeprasanth, R. Srivastava, D. Srinivas, P. Ratnasamy, Solid acid catalyts
for production of biofuels and lubricants, Appl. Catal. A: Gen. 314 (2006) 148–
159.
References
[1] Y. Yang, Z. Du, Y. Huang, F. Lu, F. Wang, J. Gao, J. Xu, Conversion of furfural into
cyclopentanone over Ni-Cu bimetallic catalysts, Green Chem. 15 (2013) 1932–
1940.
[2] Q. Deng, G. Nie, L. Pan, J.-J. Zou, X. Zhang, L. Wang, Highly selective self-
condensation of cyclic ketones using MOF-encapsulating phosphotungstic acid
for renewable high-density fuel, Green Chem. 17 (2015) 4473–4481.
[3] M. Renz, Ketonization of Carboxylic acids by decarboxylation: mechanism and
scope, Eur. J. Org. Chem. 6 (2005) 979–988.
[4] C.O. Tuck, E. Pérez, I.T. Horváth, R.A. Sheldon, M. Poliakoff, Valorization of
biomass: deriving more value from waste, Science 337 (2012) 695–699.
[5] A. Berlin, No barriers to cellulose breakdown, Science 342 (2013) 1454–1456.
[6] M. Hronec, K. Fulajtarová, T. Liptaj, Effect of catalyst and solvent on the furan
ring rearrangement to cyclopentanone, Appl. Catal. A: Gen. 437–438 (2012)
104–111.
[7] M. Hronec, K. Fulajtarová, T. Soták, Highly selective rearrangement of furfuryl
alcohol to cyclopentanone, Appl. Catal. B: Environ. 154–155 (2014) 294–300.
[8] T.D. Swift, H. Nguyen, Z. Erdman, J.S. Kruger, V. Nikolakis, D.G. Vlachos, Tandem
Lewis acid/Brønsted acid-catalyzed conversion of carbohydrates to 5-
hydroxymethylfurfural using zeolite beta, J. Catal. 333 (2016) 149–161.
[9] M. Hronec, K. Fulajtarová, Selective transformation of furfural to
cyclopentanone, Catal. Commun. 24 (2012) 100–104.
[10] G.-S. Zhang, M.-M. Zhu, Q. Zhang, Y.-M. Liu, H.-Y. He, Y. Cao, Towards
quantitative and scalable transformation of furfural to cyclopentanone with
supported gold catalysts, Green Chem. 18 (2016) 2155–2164.
[11] J. Guo, G. Xu, Z. Han, Y. Zhang, Y. Fu, Q. Guo, Selective conversion of furfural to
cyclopentanone with CuZnAl catalysts, ACS Sustain. Chem. Eng. 2 (2014)
2259–2266.
[12] X.-L. Li, J. Deng, J. Shi, T. Pan, C.-G. Yu, H.-J. Xu, Y. Fu, Selective conversion of
furfural to cyclopentanone or cyclopentanol using different preparation
methods of Cu-Co catalysts, Green Chem. 17 (2015) 1038–1046.
[13] Y. Wang, S. Sang, W. Zhu, L. Gao, G. Xiao, CuNi@C catalysts with high activity
derived from metal-organic frameworks precursor for conversion of furfural to
cyclopentanone, Chem. Eng. J. 299 (2016) 104–111.
[14] X. Cao, T. Lyu, W. Xie, A. Mirjalili, A. Bradicich, R. Huitema, B.W.-L. Jang, J.K.
Keum, K. More, C. Liu, X. Yan, Preparation and investigation of Pd doped Cu
catalysts for selective hydrogenation of acetylene, Front. Chem. Sci. Eng.
(2019), https://doi.org/10.1007/s11705-019-1822-3.
[30] M. Kotwal, S.S. Deshpande, D. Srinivas, Esterification of fatty acids with
glycerol over Fe-Zn double-metal cyanide catalyst, Catal. Commun. 12 (2011)
1302–1306.
[31] A. Peeters, P. Valvekens, R. Ameloot, G. Sankar, C.E.A. Kirschhock, D.D. Vos,
Lewis acid double metal cyanide catalysts for hydroamination of
phenylacetylene, Chem. Commun. 47 (2011) 4114–4116.
[32] M.V. Patil, M.K. Yadav, R.V. Jasra, Prins condensation for synthesis of nopol
from pinene and paraformaldehyde on novel Fe-Zn double metal cyanide solid
acid catalyst, J. Mol. Catal. A: Chem. 273 (2007) 39–47.
[33] A. García-Ortiz, A. Grirrane, E. Reguera, H. García, Mixed (Fe2+ and Cu2+) double
metal hexacyanocobaltates as solid catalyst for the aerobic oxidation of
oximes to carbonyl compounds, J. Catal. 311 (2014) 386–392.
[34] J.-J. Zou, Y. Xu, X. Zhang, L. Wang, Isomerization of endo-dicyclopentadiene
using Al-grafted MCM-41, Appl. Catal. A: Gen. 421–422 (2012) 79–85.
[35] M.S. Kandanapitiye, F.J. Wang, B. Valley, C. Gunathilake, M. Jaroniec, S.D.
Huang, Selective ion exchange governed by the Irving-Williams series in
K2Zn3[Fe(CN)6]2 nanoparticles: toward
a designer prodrug for Wilson’s
disease, Inorg. Chem. 54 (2015) 1212–1214.
[36] J. Liu, X. Li, A.I. Rykov, Q. Fan, W. Xu, W. Cong, C. Jin, H. Tang, K. Zhu, A.S.
Ganeshraja, R. Ge, X. Wang, J. Wang, Zinc-modulated Fe-Co prussian blue
analogues with well-controlled morphology for efficient cesium sorption, J.
Mater. Chem. A 5 (2017) 3284–3292.
[15] C.-Y. Liu, R.-P. Wei, G.-L. Geng, M.-H. Zhou, L.-J. Gao, G.-M. Xiao, Aqueous-
phase catalytic hydrogenation of furfural over Ni-bearing hierarchical Y zeolite
catalysts synthesized by a facile route, Fuel Process. Technol. 134 (2015) 168–
174.
[37] B.L. Wegenhart, L. Yang, S.C. Kwan, R. Harris, H.I. Kenttämaa, M.M. Abu-Omar,
From furfural to fuel: synthesis of furoins by organocatalysis and their
[16] J. Ohyama, R. Kanao, Y. Ohira, A. Satsuma, The effect of heterogeneous acid-
base catalysis on conversion of 5-hydroxymethylfurfural into
cyclopentanone derivative, Green Chem. 18 (2016) 676–680.
a
hydrodeoxygenation by cascade catalysis, ChemSusChem
2747.
7 (2014) 2742–
[17] J. Ohyama, R. Kanao, A. Esaki, A. Satsuma, Conversion of 5-
hydroxymethylfurfural to cyclopentanone derivative by ring
[38] H. Li, J. Chen, Y. Wan, W. Chai, F. Zhang, Y. Lu, Water-medium Ullmann
reaction over a highly active and selective Pd/Ph-SBA-15 catalyst, Green Chem.
9 (2007) 273–280.
a
rearrangement over supported Au nanoparticles, Chem. Commun. 50 (2014)
5633–5636.
[39] S. Bhogeswararao, D. Srinivas, Catalytic conversion of furfural to industrial
chemicals over supported Pt and Pd catalysts, J. Catal. 327 (2015) 65–77.
[40] M. Samy El-Shall, V. Abdelsayed, A.E. Rahman, S. Khder, H.M.A. Hassan, H.M.
El-Kaderi, T.E. Reich, Metallic and bimetallic nanocatalysts incorporated into
highly porous coordination polymer MIL-101, J. Mater. Chem. 19 (2009) 7625–
7631.
[41] Q. Deng, J. Xu, P. Han, L. Pan, L. Wang, X. Zhang, J.-J. Zou, Efficient synthesis of
high-density aviation biofuel via solvent-free aldol condensation of cyclic
ketones and furanic aldehydes, Fuel Process. Technol. 148 (2016) 361–366.
[18] R. Ramos, A. Grigoropoulos, N. Perret, M. Zanella, A.P. Katsoulidis, T.D.
Manning, J.B. Claridge, M.J. Rosseinsky, Selective conversion of 5-
hydroxymethylfurfural to cyclopentanone derivatives over Cu-Al2O3 and Co-
Al2O3 catalysts in water, Green Chem. 19 (2017) 1701–1713.
[19] R. Fang, H. Liu, R. Luque, Y. Li, Efficient and selective hydrogenation of
biomass-derived furfural to cyclopentanone using Ru catalysts, Green Chem.
17 (2015) 4183–4188.
[20] J. Luo, A. Sam, B. Hu, C. DeBruler, X. Wei, W. Wang, T.L. Liu, Unraveling pH
dependent cycling stability of ferricyanide/ferrocyanide in redox flow
batteries, Nano Energy 42 (2017) 215–221.