Catalytic production of 1,4-pentanediol from furfural in a fixed-bed system under mild conditions

Article abstract of DOI:10.1039/d0gc00233j

Furfural is one of the most important biomass-derived chemicals. Its large-scale availability calls for the exploration of new transformation methods for further valorization. Here we report on the direct, one-step conversion of furfural into 1,4-pentanediols (1,4-PeDs) using a combination of Amberlyst-15 and Ru-FeO_x/AC catalysts. It is interesting to find that the introduction of a suitable amount of FeO_xresults in a great improvement in the dispersion of Ru and a decrease in the Lewis acidity. Both XPS and H₂-TPR show that there is electron transfer from Ru to Fe, and the electronic interaction facilitates the reduction of both Ru and Fe species. When used in combination with Amberlyst-15, the Ru-6.3FeO_x/AC catalyst afforded the best performance with a 1,4-PeD yield of 86%; by contrast, Ru/AC free of FeO_xonly gave levulinic acid as the major product, demonstrating the key role of the acid/metal balance in the one-pot conversion of furfural to 1,4-PeD. Moreover, such a dual catalyst exhibited excellent durability within 175 h time-on-stream.

Full text of DOI:10.1039/d0gc00233j

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DOI: 10.1039/D0GC00233J
ARTICLE
Catalytic production of 1, 4-Pentanediol from furfural in a fix-bed
system under mild conditions
a
Qiaoyun Liu,‡a,b Botao Qiao,‡ Fei Liu,*a Leilei Zhang,a Yang Su,a Aiqin Wang,*a,c and Tao Zhanga,c
Received 00th January 20xx,
Accepted 00th January 20xx
Furfural is one of the most important biomass-derived chemicals. Its large-scale availability calls for the exploration of new
transformation routes for further valorization. Here we report on the direct, one-step conversion of furfural into 1, 4-
pentanediols (1, 4-PeD) using a combination of Amberlyst-15 and Ru-FeOx/AC catalysts. It is interesting to find that the
introduction of a suitable amount of FeOx results in a great improvement in the dispersion of Ru and a decrease in the Lewis
acidity. Both XPS and H2-TPR show that there is electron transfer from Ru to Fe, and the electronic interaction facilites the
reduction of both Ru and Fe species. When in combination use with Amberlyst-15, the Ru-6.3FeOx/AC afforded the best
performance with 1, 4-PeD yield of 86%; by contrast, the Ru/AC free of FeOx only gave levulinic acid as the major product,
demonstrating the key role of the acid/metal balance in the one-pot conversion of furfural to 1, 4-PeD. Moreover, such a
dual catalyst exhibited excellent durability within 175 h time-on-stream.
DOI: 10.1039/x0xx00000x
furfural as the starting material, the selectivity of 1,5-PeD was
decreased to 71.4% due to multiple side reactions stemming
from hydrolysis, over-hydrogenolysis, dehydroxylation and
polymerization.8 The similar phenomenon was also observed in
the synthesis of 1,2-PeD.9 These previous studies indicate that
the high chemical reactivity of furfural has become a big barrier
for controlling product selectivity. Therefore, it is keenly desired
to develop a novel catalytic strategy that can effectively inhibit
the occurrence of side reactions on furfural molecule.
Generally, the transformation of furfural to PeDs involves
hydrogenation, ring-opening and de-oxygenation (Scheme 1),
which requires exquisite balance of metallic and acid sites to
obtain a high selectivity. Recently, we reported that furfural
was transformed into 1, 4-PeD with a yield as high as 90% by
using a combination of a proton acid catalyst (CO2/H2O) and a
hydrogenation catalyst (Ru/CMK-3).12 Unfortunately, the
Ru/CMK-3 catalyst could not survive under an aqueous acid
Introduction
Furfural is an important biomass-derived platform molecule
with both furan ring and aldehyde functional groups, starting
with which a variety of chemicals can be produced such that
renewability and sustainability of the involved chemistry can be
improved greatly.1, 2 Among others, pentanediols (PeDs) are an
important class of chemicals which have been widely used as
monomers in polyester industry, functional ingredients in
cosmetics, and intermediates in pharmaceutics.3, 4 When using
furfural as the feedstock to produce PeDs, selectivity control is
a key scientific issue and in many cases a mixture of PeDs
(including 1, 4-PeD, 1,5-PeD, and 1,2-PeD) are obtained, which
will greatly increase the separation cost.5 Therefore, through
catalyst manipulation to obtain one specific PeD with a high
selectivity remains challenging.
Current catalytic strategies involve the hydrogenolysis of C-
O bond of a relatively stable furfural derivative to obtain one
specific PeD, and the product selectivity critically relies on the
catalyst composition.6-11 For example, when bimetallic catalysts
composed of a platinum group metal (Pt, Pd, Ir, etc.) and an
oxophilic metal (Re, Mo, or W) were employed in the
hydrogenolysis of tetrahydrofurfuryl alcohol (THFA), 1,5-PeD
was obtained with a selectivity up to 94%.6, 7 However, with
a. Key Laboratory of Science and Technology on Applied Catalysis, Chinese
Academy of Sciences, Dalian 116023, China. E-mail: fei.liu@dicp.ac.cn,
aqwang@dicp.ac.cn
b. University of Chinese Academy of Sciences, Beijing 100049, China
c. State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese
Academy of Sciences, Dalian 116023, China
Scheme 1. Scientific strategy of this work and abbreviation of
main chemicals discussed in this work.
†Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
solution, resulting in leaching and aggregation of catalytically
active Ru species and consequently significant loss of activity.
To improve the catalyst stability, using a solid acid catalyst in
‡These authors contributed equally.
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combination with a hydrogenation metal catalyst would be a the stabilization of baseline, the CO adsorption was carried out
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DOI: 10.1039/D0GC00233J
reasonable choice.
by the pulse adsorption of 5% CO in He.
In this work, we report a dual catalyst system composed of
High-angel annual dark-field scan transmission electron
Ru-FeOx/AC catalyst and solid acid Amberlyst-15, for the microscopy (HAADF-STEM) analyses were performed with a JEOL
transformation of furfural to 1, 4-PeD. Choosing FeOx as the JEM-2100F microscope operated at 200 kV. And the abreaction-
promoter is inspired by the previous reports that it can promote corrected HAADF-STEM images were obtained on a JEM ARM
the dispersion of noble metals as single atoms owing to the microscope. For all microscopy analysis the samples were
strong metal-support interaction. 13-15 The introduction of FeOx ultrasonically dispersed in ethanol and then a drop of the
to Ru/C can greatly improve the dispersion of Ru meanwhile solution was put onto microgrid carbon polymer supported on
decrease the Lewis acidity. The exquisite balance between acid copper grid.
and metallic functions allows for good to excellent yields of 1,
Hydrogen temperature-programmed reduction (H2-TPR) was
4-PeD being achieved under mild reaction conditions. More performed using Micromeritics Autochem II 2920. The calcined
importantly, thanks to the use of solid acid, the durability of the sample (100 mg) was placed in the U-shaped quartz reactor and
catalyst system was improved greatly such that it could be heated at 473 K in Ar for 30 min to remove the physically
operated in a continuous fixed-bed system for at least 175 h adsorbed water and other contaminants. After cooling the
without any loss of activity and selectivity.
sample down to 323 K, the gas was switched to 10% H2/Ar, and
the sample was heated to 1073 K at a ramp rate of 10 K min-1
for reduction. H2 consumption during sample reduction was
monitored via TCD and double-checked using mass
spectrometry.
Experimental
Catalysts preparation
X-ray photoelectron spectroscopy (XPS) was performed using
an ESCALAB 250 instrument equipped with an Al Kα X-ray
radiation source (1486.6 eV). Before the measurement, the
catalyst was reduced in 10% H2/He at 473 K for 30 min, and after
cooling to room temperature in He, the sample was transferred
to the sample holder without tableting. Binding energies were
calibrated using the C 1s peak at 284.6 eV.
The acidities of Ru-yFeOx/AC catalysts used in this work
were characterized by the NH3-TPD which was carried out with
a Micromeritics AutoChem II2920. Before each test, 0.1 g
calcinated sample was placed in a quartz reactor, pretreated in
10% H2/Ar flow at 473 K for 30 min and cooled down in He flow
to 373 K. After the saturated adsorption NH3, the sample was
heated at 373 K in He for 30 min to remove the physically
adsorbed NH3. Desorption of NH3 was conducted in He flow
from 373 K to 1073 K at a heating rate of 10 K min-1. The
desorbed NH3 molecules were detected by a Cirrus 2 mass
spectrometry (MS). In the measurement, m/e =16 was
monitored to analyse the desorbed NH3 to avoid the
interference of water.
The Ru-yFeOx/AC catalysts were prepared by co-deposition-
precipitation method as following. Firstly, 0.5g activated carbon
(AC) was added into 30 ml ultrapure water in a round-bottom
flask, and stirring at 80oC. Then 0.5g Na2CO3 was put into the
suspension. A given amount of aqueous solutions of RuCl3·3H2O
and Fe(NO3)3 were mixed and then added dropwise to the
suspension during stirring, which was maintained at 80oC for 2
h. The pH of the reaction system was controlled to between 9
and 10 after precipitation. When the reaction was completed,
the mixture was aged for 2 h. Next the precipitate was filtered
and washed repeatedly till the filtrate was neutral, then dried
at 60 oC for 12 h. The catalysts were calcinated at 300 oC for 5 h
in N2 and reduced in 10% H2-90% He flow at 200 oC for 30 min
before use.
Characterizations
The actual Ru, Fe loadings of various catalysts were determined
by inductively coupled plasma atomic emission spectroscopy
(ICP-AES) on an IRIS Intrepid II XSP instrument (Thermo Electron
Corporation).
X-ray diffraction patterns were collected at a PW3040/60 X’
Pert PRO (PANalytical) diffractometer equipped with a copper
target (Cu Kα, λ = 0.15432 nm), operating at 40 kV and 40 mA.
A continuous mode was used for data collecting in the 2θ range
from 10o to 80o at a scanning speed of 10° min-1.
The CO chemisorption of the Ru-yFeOx/AC catalysts was
carried out with a Micromeritics AutoChem II 2920 Automated
Catalyst Characterization System. The Ru dispersion on the
catalysts was calculated according to the molar ratios of the
chemically adsorbed CO on the catalysts and the Ru in the
catalysts (assuming that the stoichiometry of chemically
adsorbed CO to surface Ru atom is one). These values
correspond to the ratio of surface Ru atoms to total Ru atoms.
Before each test, the sample was heated in He flow at 473 K for
1 h to remove the physically adsorbed water. The sample was
reduced in 10% H2/Ar flow at 473 K for 30 min, cooled down in
He flow to 323 K and purged in He flow at 323 K for 30 min. After
Reaction tests
All the reactions were conducted in a 50 mL Parr batch reactor.
In a typical experiment, 30 mg Ru-yFeOx/AC and 40 mg
Amberlyst-15 was added to a mixture of H2O (5 mL) and furfural
(100 mg, 1.04 mmol). This solution was placed inside the
autoclave and was flushed with H2 for several times. Next, the
autoclave was pressurized with H2 to 0.2 MPa. The reaction
mixture was stirred and heated to 80oC for 20 h. After reaction
the autoclave was cooled to room temperature, vented, and
opened. The catalyst was separated by centrifugation, and the
recovered solution was then analysed by gas chromatography
(GC), with n-butanol as the internal standard, on Agilent 7890B
equipped with an FID detector (270oC) and an HP-INNOWAX
column (30 m x 0.32 mm, 0.5 m). The conversion of furfural
and the selectivity of diols are determined by GC-MS analysis
(Figure S1).
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Stability test
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DOI: 10.1039/D0GC00233J
The stability test was conducted in a continuous flow fixed-bed
reaction system with a stainless-steel tubular reactor (internal
diameter 9 mm, length 370 mm). Prior to the reaction, 0.79 g of
Ru-6.3FeOx/AC was pre-reduced at 473 K in 10% H2/He for 0.5
h, and then mixed with 1.10 g of Amberlyst-15 and ground into
powder. The mixture catalyst was placed in the center of the
reactor with a bed height of 60 mm. Both sides of the catalyst
bed were packed with silica sand and separated from the
catalyst by a thin layer of silica wool. Upon being heated to 353
K, an aqueous solution of 2 wt% furfural and H2 were co-fed into
the reactor. The liquid flow rate was 0.007 ml/min and the gas
flow rate was 8 ml/min. The outlet stream was condensed with
a cold trap, and the liquid sample was obtained for analysis.
Figure 1. XRD patterns of Ru/AC, Ru-1.25FeOx/AC, Ru-
6.3FeOx/AC and Ru-7.9FeOx/AC.
Results and discussion
Characterization of Ru-yFeOx/AC catalysts
The Ru-FeOx/AC catalysts with different Fe/Ru mass ratios
were prepared by a co-deposition-precipitation method. ICP
analysis revealed that the mass ratio of Fe to Ru in the three
samples was 1.25, 6.3 and 7.9, respectively, which are denoted
hereafter as Ru-1.25FeOx/AC, Ru-6.3FeOx/AC and Ru-
7.9FeOx/AC, respectively. Figure 1 shows the X-ray diffraction
(XRD) patterns of the Ru-yFeOx/AC catalysts. For all the three
samples as well as the reference Ru/AC, no any Ru diffraction
peak was observed, indicating that Ru species are highly
dispersed on the support. On the other hand, the dispersion of
Fe2O3 decreased with an increase of the Fe loading. When the
Fe/Ru mass ratio was equal to or above 6.3, the reflections of
Fe2O3 could be clearly observed, indicating the aggregation of
Fe2O3 nanoparticles. High-angle annular dark-field scanning
transmission electron microscopy (HAADF-STEM) images
provided further evidence. For both the Ru-6.3FeOx/AC and
Ru-1.25FeOx/AC samples, finely dispersed nanoparticles, with
a mean particle size of 1.06 nm and 1.19 nm, respectively,
could be visually observed (Figure. 2a, 2b). On the contrary,
large particles were clearly observed in the Ru-7.9FeOx/AC
Figure 2. HAADF-STEM images of (A) Ru-1.25FeOx/AC, (B) Ru-
6.3FeOx/AC, (C) Ru-7.9FeOx/AC and (D) elemental mapping of
Ru-6.3FeOx/AC.
Table 1. The actual metal contents, average metal particle sizes, metal dispersions and acid sites on different catalysts
Actual Ru
content
(wt.%)a
Metal
dispersion
(%)c
Amount of acid sites
Average metal
particle size (nm)b
CO chemisorption
(mmol g-1)
Catalyst
(mol g-1)d
Ru-7.9FeOx/AC
Ru-6.3FeOx/AC
Ru-1.25FeOx/AC
Ru/AC
2.0
1.5
1.5
2.1
1.30±0.01
1.06 ± 0.01
1.19 ± 0.02
2.47 ± 0.05
27.9
42.4
29.4
34.8
14.1
28.6
19.8
16.7
119
193
243
385
a The actual metal contents in the catalysts were measure by ICP analysis.
b The average metal particle sizes were estimated according to the STEM results.
c The metal dispersions were calculated according to the CO chemisorption results.
d The amount of acid sites were measured by the microcalorimetric measurements of ammonia adsorption.
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selectivity of 1, 4-PeD (86%). Such a promising performance
sample (Figure 2c). This result suggests that there is an optimal
ratio of Fe to Ru, at which value (~ 6.3) both Ru and Fe can be
highly dispersed. Elemental mapping (Figure 2d) of the Ru-
6.3FeOx/AC sample revealed that Ru and Fe are close to each
other and homogeneously dispersed. In agreement with the
XRD and HAADF-STEM results, the CO chemisorption data also
showed that the Ru-6.3FeOx/AC catalyst had the highest
dispersion of Ru, followed by Ru-1.25FeOx/AC and Ru-
7.9FeOx/AC (Table 1).
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could be well correlated with the charaDcOteI:r1iz0a.1t0i3o9n/Dr0eGsCu0lt0s2.3A3Js
stated above, XRD, TEM, chemisorption of CO, and XPS
revealed that the Ru-6.3FeOx/AC catalyst possessed the
highest fraction of Ru0 species on the surface, which
contributed to the high activity for hydrogenation. The
formation of 3-AP on the other two Ru-yFeOx/AC catalysts
suggested their insufficient capability for further
hydrogenation (Scheme 1) due to the low concentration of
surface Ru0 species. On the other hand, the Ru-yFeOx/AC
Figure 3 displays H2-TPR profiles of the Ru-yFeOx/AC
samples. Compared with Ru/AC, the introduction of Fe resulted
in the shift of reduction temperatures to lower values.
Moreover, for the Ru-6.3FeOx/AC and Ru-7.9FeOx/AC samples,
the first reduction peak, which can be ascribed to the reduction
of Ru, became sharper, suggesting the Ru species are more
uniform than that on Ru/AC and Ru-1.25FeOx/AC. In order to
understand the role of FeOx in promoting the reduction of Ru,
XPS analysis was performed on the freshly reduced catalysts
(Figure. 4 and Table 2). In the Ru 3p3/2 XPS spectra, a dominant
peak at binding energy (BE) of 461.9 eV and a minor peak at BE
of 464.9 eV are present in the Ru/C sample, which can be
17
ascribed to Ru0 and Ru3+, respectively.16,
Compared with
Ru/AC, all the Ru-yFeOx/AC samples have a higher Ru0/Ru3+
ratio, in agreement with H2-TPR that the introduction of FeOx
promoted the reduction of Ru species. Moreover, the Ru0
species in both the Ru-6.3FeOx/AC and Ru-1.25FeOx/AC
present a positive shift compared to that in Ru/AC, suggesting
the electron transfer from Ru to FeOx. In line with this, the XPS
spectra of Fe species in the Ru-yFeOx/AC samples show the
negative shift compared to the Ru-free FeOx/AC sample, and
the Fe2+/Fe3+ ratio decreases with increasing the Fe content,
Figure 3. H2-TPR profiles of Ru-yFeOx/AC catalysts.
demonstrating Ru also promotes the reduction of Fe3+ species.
18
Catalytic performances
The furfural transformation reaction was conducted at 0.2
MPa H2 and 80 oC by employing the dual catalyst composed of
the above Ru-yFeOx/AC catalyst with Amberlyst-15, the latter
being a widely used solid acid catalyst in industry owing to its
strong acidity and environmental friendliness.19 Figure 5
illustrates the furfural conversion and products selectivity over
different catalysts. It is noted that neither Ru/AC nor Ru/Fe3O4
could produce 1, 4-PeD; instead, LA and FA were observed as
the main products, respectively, and only moderate furfural
conversions were reached. In contrast, the Ru-yFeOx/AC
catalysts afforded much enhanced furfural conversions under
identical conditions. More interestingly, the Ru-6.3FeOx/AC
catalyst gave the highest catalytic activity (100%) and
Figure 4. XPS of (a) Ru 3p and (b) Fe 2p spectra of Ru/AC and
Ru-yFeOx/AC.
Table 2. XPS analysis results for Ru/AC and Ru-yFeOx/AC catalysts.
Binding Energy (eV)
Catalysts
Content (%)
Ru3+ Fe2+
Ru0/Ru3+
Fe2+/Fe3+
Ru3+
Ru0
Fe2+
-
Fe3+
-
Ru0
82.7
86.3
86.7
84.8
Fe3+
-
Ru/AC
464.9
465.9
465.3
465.8
461.9
462.4
462.3
462.0
17.3
13.7
13.3
15.2
-
4.8
6.3
6.5
5.6
-
Ru-1.25FeOx/AC
Ru-6.3FeOx/AC
Ru-7.9FeOx/AC
710.5
710.6
710.3
713.0
712.7
711.8
56.3
50.5
36.4
43.7
49.5
63.6
1.3
1.0
0.6
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catalysts possessed Lewis acid sites,20,
ARTICLE
and the amount a delicate balance of acidity and hydrogenation VcieawpAarbticilleitOyn.liInne
21
increased with decreasing the Fe content (Table 1 and Figure contrast, when the H+/Ru0 ratio isDOsI:m10a.l1l0e3r9/Dth0GanC00120330J,
S2): Ru-7.9FeOx/AC < Ru-6.3FeOx/AC < Ru-1.25FeOx/AC < hydrogenation of furfural predominates the reaction leading to
Ru/AC. Since the formation of 1, 4-PeD requires good match a high yield of FA; whereas the H+/Ru0 ratio >170 leads to the
between two functional sites (acid sites and metallic dominant formation of 3-AP. More detailed investigations on
hydrogenation sites), the excess amount of acid sites on both the reaction temperature and H+/Ru0 ratio (Fig. S3, Table S2)
the Ru-1.25FeOx/AC and Ru/AC lead to the predominance of reveal that, compared with 1,4-PeD, the GVL formation through
hydrolysis step (Path 2 in Scheme 1), thus lowering the LA route (Scheme 1) requires a slightly higher reaction
selectivity of 1, 4-PeD. Therefore, it can be concluded that the temperature (e.g 100 oC). However, higher H+/Ru0 ratios led to
number of acid sites and metallic sites on the Ru-6.3FeOx/AC the formation of 3-AP and oligomers.
catalyst is such balanced that the best activity and selectivity of
1, 4-PeD could be obtained. Detailed investigation of the
reaction conditions (H2 pressure, catalyst amount, etc., Table S1
and Fig. S3) confirmed it is necessary to make the reaction rate
for each elementary step match each other for achieving the
satisfied yield of 1, 4-PeD.
Finally, the stability of dual catalyst Ru-6.3FeOx/AC +
Amberlyst-15 was examined in a continuous flow fixed-bed
reaction system. Figure. 8 illustrates the furfural conversion and
the product selectivity with time on stream at 80 oC. The
catalyst showed promising stability in 175 h, the selectivity of
1,4-PeD declined only slightly from the initial 78% to 73%.
Figure 5. Furfural conversions (black) and the carbon yields of
1, 4-PeD (red), GVL (blue), 3-AP (orange), FA (pink), THFA
(green) and LA (olivine) over different solid-acid catalysts. Figure 6. Furfural conversions (black) and the carbon yields of
Reaction conditions: 353 K, 20h; 5 g 2 wt% aqueous solution of 1, 4-PeD (red), GVL (blue), FA (pink) and THFA (green) over
furfural, 30 mg Ru-based catalyst and 40 mg Amberlyst-15 were different solid-acid catalysts. Reaction conditions: 353 K, 0.2
used for each test. Other products stem from acid-catalyzed MPa H2, 20 h; 5 g 2 wt% aqueous solution of furfural, 30mg Ru-
degradation of intermediates leading to the formation of 6.3FeOx/AC and 40 mg solid acid catalyst were used for each
oligomeric and tar-like product.
test.
In addition to intrinsic Lewis acid sites on the Ru-yFeOx/AC
catalysts, the presence of Brønsted acid is even more important
for the ring-opening of FA (Scheme 1). Figure 6 compares the
performances of different Brønsted acid catalysts when used in
combination with the Ru-6.3FeOx/AC catalyst. It clearly shows
that Nafion-212, H-Beta and H-ZSM-5 led to the dominant
formation of FA since their much lower amount of acid sites
than the Amberlyst-15 was unfavourable to the acid-catalyzed
ring-opening of FA, thus suppressing the formation of 1, 4-PeD.
On the other hand, stronger acid catalyst like Amberlyst-36
would promote the hydrolysis reaction, thus leading to the
decreased selectivity of 1, 4-PeD due to the formation of GVL
from furfural. Evidently, the combination of Amberlyst-15 and
Ru-6.3FeOx/AC catalysts is the most efficient dual catalyst for
the direct formation of 1, 4-PeD from furfural.
In order to further evaluate the respective role of acid sites
and hydrogenation sites, we depicts the product selectivity as a
function of the H+/Ru0 ratio. As shown in Fig. 7, the highest yield
of 1,4-PeD occurs only when the H+/Ru0 ratio is approximately
150, suggesting that the selective formation of 1,4-PeD requires
Figure 7. The products distribution as a function of H+/Ru0
ratios.
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20
0
25
50
75
100
125
150
175
Time(h)
7.
Figure 8. Catalytic performances vs. time on stream over Ru-
6.3FeOx/AC catalyst with Amberlyst-15 at 80oC. Reaction
conditions: 1.89 g catalyst (Ru-6.3FeOx/AC and Amberlyst-15
mass ratio: 0.73), 2 wt% furfural aqueous solution: flow rate
0.007ml/min, H2 flow rate 8ml/min.
8.
9.
Conclusions
10.
11.
12.
In summary, we have shown that the direct and highly selective
transformation of furfural to 1, 4-PeD was realized using a
combination of Amberlyst-15 and Ru-6.3FeOx/AC catalyst
o
under rather mild condition (80 C and 0.2MPa). The superior
performance can be attributed to the greatly enhanced
dispersion of Ru by introduction of FeOx, which accelerates the
hydrogenation of furfural to FA. On the other hand, the
presence of a suitable amount of FeOx decreased the Lewis
acidity of Ru/AC, thus suppressing the hydrolysis of FA to LA.
The exquisite balance between acid and metal sites offers the
1, 4-PeD yield as high as 86%, and the catalyst displays
promising durability in 175 h time-on-stream. The strategy by
introducing FeOx to modify the acidity and metallic
bifunctionality of Ru/C can be extended to other systems, thus
paving a new way to directly producing high-value-added
chemicals and biofuels from furfural.
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Conflicts of interest
There are no conflicts to declare.
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Acknowledgements
This work was supported by the National Key R&D Program of
China (2018YF1501602), National Natural Science Foundation
of China (21606227, 21690080, 21690084, 21721004,
21673228, and 21878289), Strategic Priority Research Program
of the Chinese Academy of Sciences (XDB17020100) and Dalian
National Laboratory for Clean Energy (DNL180303).
Notes and references
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 6
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Green Chemistry
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DOI: 10.1039/D0GC00233J
Table of Contents Graphic
Synopsis
A dual catalyst system composed of Ru-FeOx/AC catalyst and solid acid
Amberlyst-15, for the direct transformation of furfural to 1,4-PeD with
excellent stability and yield.