Basic anion-exchange resin (AER)-supported Au-Pd alloy nanoparticles for the oxidation of 5-hydroxymethyl-2-furfural (HMF) into 2,5-furan dicarboxylic acid (FDCA)

Article abstract of DOI:10.1016/j.apcata.2017.09.012

Au-Pd alloy nanoparticles supported on basic anion-exchange resin (AER) have exceptional catalytic activity for the oxidation of 5-hydroxymethyl-2-furfural (HMF) into 2,5-furan dicarboxylic acid (FDCA) with an equimolar amount of base. SEM-EDX and TEM analyses show that 5–20 nm Au-Pd alloy nanoparticles are well dispersed both on the resin surface and inside resin spheres by a simple procedure without any assistance of additives. XPS analysis reveals that Au- and Pd metals exist in an alloy form on the AER support, which is confirmed by a comparison study with a mixture of AER-supported monometallic nanoparticles (AER-supported Au and AER-supported Pd). In the presence of a 1:1 ratio of Au-Pd alloy nanoparticles over Amberlite IRA-743 resin with O₂ (10 bar) at 373 K in an equimolar Na₂CO₃ aqueous solution, HMF is oxidized to FDCA with a 93.2% yield. On the other hand, mixture of AER-supported Au and AER-supported Pd affords only a 52% FDCA yield under identical conditions. This catalyst can be used 6 times without any significant loss of activity. FDCA is also obtained from HMF with an 82.9% yield in air (40 bar).

Full text of DOI:10.1016/j.apcata.2017.09.012

Accepted Manuscript
Title: Basic anion-exchange resin (AER)-supported Au-Pd
alloy nanoparticles for the oxidation of
5-hydroxymethyl-2-furfural (HMF) into 2,5-furan
dicarboxylic acid (FDCA)
Authors: Churchil A. Antonyraj, Nhan Thanh Thien Huynh,
Seok-Kyu Park, Seunghan Shin, Yong Jin Kim, Sangyong
Kim, Kwan-Young Lee, Jin Ku Cho
PII:
S0926-860X(17)30441-6
DOI:
Reference:
http://dx.doi.org/10.1016/j.apcata.2017.09.012
APCATA 16406
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
7-6-2017
5-9-2017
9-9-2017
Please cite this article as: Churchil A.Antonyraj, Nhan Thanh Thien Huynh, Seok-
Kyu Park, Seunghan Shin, Yong Jin Kim, Sangyong Kim, Kwan-Young Lee, Jin
Ku Cho, Basic anion-exchange resin (AER)-supported Au-Pd alloy nanoparticles for
the oxidation of 5-hydroxymethyl-2-furfural (HMF) into 2,5-furan dicarboxylic acid
(FDCA), Applied Catalysis A, Generalhttp://dx.doi.org/10.1016/j.apcata.2017.09.012
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1
Basic anion-exchange resin (AER)-supported Au-Pd alloy nanoparticles for the oxidation of 5-
hydroxymethyl-2-furfural (HMF) into 2,5-furan dicarboxylic acid (FDCA)
a
b
a,c
a,b
Churchil A. Antonyraj , Nhan Thanh Thien Huynh , Seok-Kyu Park , Seunghan Shin , Yong Jin
a,b
a,b
c
a,b,
Kim , Sangyong Kim , Kwan-Young Lee ,Jin Ku Cho *
aGreen Chemistry and Material Group, Korea Institute of Industrial Technology (KITECH),
Cheonan, Chungnam 31056, Korea
b
Department of Green Process and System Engineering, Korea University of Science and
Technology (UST), Daejeon 34113, Korea
c
Department of Chemical and Biological Engineering, Korea University, Seoul 02841, Korea
Graphical Abstract
Basic anion-exchange resin (AER)-supported Au-Pd alloy nanoparticles were readily prepared and
successfully applied to the oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furan dicarboxylic acid
(
FDCA).

2
Highlights





Au-Pd alloy nanoparticles were simply supported on basic anion-exchange resin.
The nanoparticles were dispersed both on the resin surface and inside resin sphere
HMF was oxidized to FDCA with 93.2% yield using this catalyst.
This catalyst could be used 6 times without any significant loss of activity.
With this catalyst, FDCA was obtained from HMF with an 82.9% in air.
Abstract
Au-Pd alloy nanoparticles supported on basic anion-exchange resin (AER) have exceptional catalytic
activity for the oxidation of 5-hydroxymethyl-2-furfural (HMF) into 2,5-furan dicarboxylic acid
(FDCA) with an equimolar amount of base. SEM-EDX and TEM analyses show that 5-20 nm Au-Pd
alloy nanoparticles are well dispersed both on the resin surface and inside resin spheres by a simple
procedure without any assistance of additives. XPS analysis reveals that Au- and Pd metals exist in
an alloy form on the AER support, which is confirmed by a comparison study with a mixture of AER-
supported monometallic nanoparticles (AER-supported Au and AER-supported Pd). In the presence
of a 1:1 ratio of Au-Pd alloy nanoparticles over Amberlite IRA-743 resin with O
2
(10 bar) at 373 K
in an equimolar Na CO aqueous solution, HMF is oxidized to FDCA with a 93.2% yield. On the
2
3
other hand, mixture of AER-supported Au and AER-supported Pd affords only a 52% FDCA yield
under identical conditions. This catalyst can be used 6 times without any significant loss of activity.
FDCA is also obtained from HMF with an 82.9% yield in air (40 bar).
Keywords: Anion-exchange resin (AER);Au-Pd alloynanoparticles; oxidation; 5-hydroxymethyl-2-
furfural (HMF); 2,5-furan dicarboxylic acid (FDCA)
1
. Introduction
Polyethylene terephthalate (PET) is a well-known fossil-derived polymer obtained by the
condensation polymerization of ethylene glycol and terephthalic acid that has a market size
approaching 4 billion lb/yr [1]. Purified terephthalic acid was also used to make resins, fibers and
films and was a versatile plastic precursor; however, as of today, it has harmful effects because of its
bioaccumulation in living organisms [2]. 2,5-Furan dicarboxylic acid (FDCA) is a renewable

3
chemical obtained by the oxidation of biomass derived 5-hydroxymethyl-2-furfural (HMF) that can
replace terephthalic acid in PET [3,4]. The synthesis of p-xylene from HMF which can further be
converted to terephthalic acid is another multi-step approach towards renewable PET [5,6].
Poly(ethylene furanoate) (PEF), which is obtained from the polymerization of ethylene glycol and
FDCA is an easily degradable polymer that also evades bioaccumulation. Furthermore, PEF has better
physical properties than PET, such as a higher gas impermeability, and higher glass transition
temperature [7,8]. Multiple reports are available on the successful oxidation of HMF to FDCA over
Au or Pt supported on metal oxides [9-16]. However, Au catalysts are found to be deactivated by the
byproducts or intermediates in some cases [17]. To overcome the weakness, bimetallic catalysts
containing Au have been developed to have catalytic activities towards HMF oxidation that are
superior to those of the monometallic catalysts because of the alloying effect [18-22]. Oxidation is a
complex multi-step reaction and recent reports claim that no commercial process is available for the
production of FDCA [23]. Another important issue with the existing powder catalysts is the need to
overcome mass transfer limitations when used in continuous reactors. Polymer materials could be
ideal catalyst supports to meet the specific demands of catalysts for different chemical reactions
because of their various structures, excellent processability, recyclability and surface properties. More
importantly, the acidity or basicity of polymer materials can be adjusted at the molecular level by
means of chemical functionalization, so that the desired reaction could be promoted and/or side
reactions could be minimized [24]. In addition, swollen polymeric resins can provide reactants and
reaction intermediates easy access to catalysts in the aqueous phase, which is a crucial role of the
support [18].
Herein we report the use of Au-Pd alloy nanoparticles supported on basic anion-exchange resins
(AERs) as a catalyst for the oxidation of HMF. Using this catalyst, a mild and efficient conversion of
HMF to FDCA can be performed with oxygen and an equimolar amount of base in the aqueous phase.
AER-supported Au-Pd alloy nanoparticles are simple to synthesize in the absence of a stabilizer via
3
+
2+
two step procedure: (i) Entrapment of Au and Pd by the interaction between the metal cations and
the phenyl rings of polystyrene backbone, when metal species can be dispersed all around resin
sphere, then (ii) reduction of metal cations to Au-Pd alloy nanoparticles (Fig 1) [25-27]. Moreover,
these bead-shaped resin supports are commercially available and readily packed in column, which
can easily be extended to the larger scale production of the catalyst for industrial purposes.

4
Fig. 1. Schematic view of preparing procedure onanion-exchange resin (AER)-supported Au-Pd alloy
nanoparticles (AER: Amberlite IRA-743).
2
. Experimental
2
.1. Materials
Gold (III) chloride trihydrate (AuCl
3
·3H
2
O 99.9%); palladium (II) chloride (PdCl , 99.9+%); 5-
2
hydroxymethyl-2-furfural (HMF, 99%); 2,5-furandicarboxylic acid (FDCA, 97%); sodium carbonate

5
(99.995%);methanol (99.8%); ethanol (99.5%); sodium boro hydride (98%); and anion-exchange
resins including Amberlite IRA-743 free base (IRA-743), Amberlite IRA-400 chloride form (IRA-
00), and Amberlite IRA-900 chloride form (IRA-900) were purchased from Sigma-Aldrich (USA).
All reagents were directly used without further purification unless otherwise mentioned.
4
2
.2. Methods
SEM-EDX analysis was performed using a JEOL-JSM-6701F field-emission scanning electron
microscope and elemental analysis was performed using an energy dispersive X-ray
detector.Transmission electron microscope (TEM) images were taken with a Maker FEI, model
Technai G2 microscope with an acceleration voltage of 200 kV using carbon-coated 200 mesh copper
grids. XPS measurements were carried out on a Thermo Fischer Scientific K-alpha using mono-
chromatized Al Kα radiation (hν = 1486.6 eV) and processed using Thermo Avantage software. The
specific surface area of the resins was determined in a BET surface analyzer (Bruanuer-Emmett-
Teller, ASAP2010, Micromeritics, USA) using N
2
as the adsorbent at liquid nitrogen temperature (77
K) in a relative pressure (P/P ) range of 0 to 0.25. The resin samples (in powder form) were degassed
0
in air for over 12 h at 100 C prior to analysis. The conversion of HMF and the selectivity of the
products, including FDCA were determined using high-performance liquid chromatography (HPLC,
Agilent 1200 series) equipped with a refractive index (RI) detector and an Aminex HPX-87H column
(
Bio-Rad laboratories, Inc.). The HPLC analysis conditions were as follows: eluent, 0.01 N H
2
SO ;
4
-1
flow rate, 0.6 mL min ; and column temperature, 45 C. Prior to the HPLC analysis, all samples were
subjected to dilution with water (HPLC grade) to prevent signal overload and damage to the
1
system.NMRSynthetic HMF was characterized by HPLC and confirmed by H NMR (400 MHz,
JNM-AL400, JEOL), which was processed by the Delta program (ver. 4.3.6). Elemental chemical
analysis of the samples was determined by inductively coupled plasma optical emission spectrometry
(
ICP-OES, Thermo Scientific, U.K., iCAP 6000 Series) by digesting the sample in a concentrated
HNO and H SO mixture (4:1). The loading of “N” content (mmol/g) in the resins were determined
3
2
4
by a CHN elemental analysis (Automatic Elemental analyzer, FLASH 2000 Series, Thermo
Scientific, USA). Each resin was analysed 3 times and the average amount of nitrogen over sample
weight were calculated and presented in Table 3.
2
.3. Procedures

6
Preparation of catalysts: A calculated amount of metal/metals (2 wt% of resins) in the form of the
chloride salt was completely dissolved in 200 mL of ethanol (a high Pd content requires more time
to dissolve). Five grams of resin (the commercial resin was dried overnight under vacuum at 313 K
and then used) was then added and stirred slowly for 24 h without breaking the resin beads. The
metal/metals were reduced using an excess of sodium boro hydride (5equiv).The metal/metals-
supported resin was filtered and washed with 400 mL of hot ethanol and then dried under vacuum for
1
2h before being used as the oxidation catalyst.
Oxidation of HMF into FDCA: The experiment was conducted in a high-pressure reactor (Series 4560
Mini Reactors, Parr Instrument Company) starting with 2mM of HMF, 200mg of resin catalyst, and
2
mM of Na
2
CO
3
in 20 mL H O. Oxygen (10 bar) was used as the oxidative agent at 373K, with
2
continuous mechanical stirring at 300 rpm for 4 h. After the reaction, the aqueous sample was taken
1
and analyzed by HPLC. After isolation, FDCA was characterized by H NMR.
3
. Results and Discussion
3
.1. Characterization of catalyst
The SEM-EDX analysis of 2 wt% Au-Pd supported on the anion-exchange resin (2% Au-Pd/IRA-
43) showed that Au and Pd were homogeneously dispersed both on the surface and inside the resin.
7
This meant that the resin swelled in the solvent during the synthesis, and the metal gained access to
the interior of resin because of macroporous nature of IRA-743 (Fig. 2a and 2b). TEM images of this
metal supported on resins showed 5-20 nm metal nanoparticles dispersed throughout the material
(Fig. 2c and 2d).

7
Fig. 2. SEM-EDX analysis of the (a) surface and (b) cross-section of Au-Pd/IRA-743 and TEM
images of (c) IRA-743 and (d) Au-Pd/IRA-743.
To investigate the chemical state and surface composition of the metal catalysts, XPS analysis was
carried out. Two binding energy peaks, positioned at 83.9 and 87.6 eV, appear with an energy
separation of 3.7 eV and an intensity ratio of 0.75, which clearly represent the spin orbit splitting of
0
metallic Au . The binding energies of the Au 4f7/2 for 2% Au/IRA-743 and 2% Au-Pd(1:1)/IRA-743
were 83.95 eV and 83.91 eV, respectively (Fig 3a and 3b). A slight shift towards lower binding energy
was observed in 2% Au-Pd(1:1)/IRA-743. On the other hand, the binding energy of the Pd 3d5/2 for
2
2
% Au-Pd(1:1)/IRA-743 was 335.94 eV, which was shifted to a high value compared with that for
% Pd/IRA-743 (335.38 eV) (Fig 3b). This shift indicated that two metal elements (Au and Pd)
formed an alloy [18,28] and this Au-Pd alloy was expected to enhance the catalytic activity via the
electron transfer between Au and Pd [29].

8
a
b
8
0
85
90
95
100
80
85
90
95
100
Binding Energy (eV)
Binding Energy (eV)
c
d
3
28 330 332 334 336 338 340 342 344 346 348
328 330 332 334 336 338 340 342 344 346 348
Binding Energy (eV)
Binding Energy (eV)
Fig. 3. XPS spectra of (A) Au 4f profile of Au/IRA-743, (B) Au 4f profile of AuPd/IRA-743, (C) Pd
d profile of Pd/IRA-743, (D) Pd 3d profile of AuPd/IRA-743
3
ICP analysis of the samples were done to find out the extent of the metal loading on to the surface of
the resin and the results of the selected samples were given in Table 1
Table 1. ICP analysis of the AER-supported Au-Pd alloy nanoparticles
Calculated
Analysed
Name
Au (wt %)
Pd (wt %)
Au (wt %)
Pd (wt %)
2
1
1
% AuPd(1:1)/IRA-743
% Pd/IRA-743
1.00
0
1.00
0.53
0
0.58
1.00
0
0.58
0
% Au/IRA-743
1.00
0.73

9
This shows with the reported synthetic route only a portion of metal was loaded on to the surface of
the resin. Au supported materials showed relatively higher loading than Pd supported or Au-Pd
supported AERs.
3
.2. Oxidation of HMF into FDCA
To elucidate the activity of the catalysts, oxidation of HMF into FDCA was studied in water with 10
bar of oxygen at 373 K (Table 2). Equimolar Na CO to HMF was used as the base. The anion-
2
3
exchange resin (IRA-743) in the absence of an active metal showed only a 2.3% FDCA selectivity
with a 68.7% conversion efficiency (Entry 1). The resin containing monometallic gold showed a high
conversion of HMF but a relatively low FDCA selectivity: both 1% Au/IRA-743 and 2% Au/IRA-
7
3
43 gave 100% HMF conversion with 27.6% and 39.1% FDCA selectivities, respectively (Entry 2-
). In the case of resin containing monometallic palladium, 80.4% and 83.5% conversion efficiencies
with 7.0% and 17.4% FDCA selectivities were observed for 1% Pd/IRA-743 and 2% Pd/IRA-743
catalyst, respectively (Entry 4-5). However, the addition of palladium to gold on the supported resin
enormously influenced the FDCA selectivity, the 1:1 Au-Pd catalyst with a 2% total metal loading
(2% AuPd(1:1)/IRA-743) showed a ~93% selectivity with 100% conversion (Entry 6). A simple
mixture of the two monometallic catalysts (1% Au/IRA-743 plus 1% Pd/IRA-743) gave only a 52.0%
FDCA selectivity (Entry 7), which could support the bimetallic effect of the Au-Pd catalyst. This
result is comparable with the recent results on bimetallic catalysts with a minimum base concentration
[
19-23]. Though reports are available for base-free heterogeneous catalytic HMF oxidation to FDCA,
the leaching of solid base materials into water and the partial solubility of FDCA makes this reaction
technically complex [13,18,30]. The catalyst leaching study was performed by taking the active
catalyst in solvent and the base without the reactant, and the reaction was conducted for 2 h. Then,
the reaction catalyst was filtered, HMF was added to the used solvent, and the reaction was conducted;
no activity was observed.
Table 2. Oxidation of HMF into FDCA using AER-supported Au-Pd alloy nanoparticlesa
Entry Catalyst
HMF Conversion (%) FDCA Selectivity (%)
1
2
IRA-743
68.7
100
2.3
1% Au/IRA-743
27.6

1
0
3
4
5
6
7
8
2% Au/IRA-743
100
80.4
83.5
100
56.3
100
39.1
7.0
1% Pd/IRA-743
2% Pd/IRA-743
17.4
93.2
5.8
2% AuPd(1:1)/IRA-743
2% AuPd(1:1)/IRA-743
1% Au/IRA-743 + 1% Pd/IRA-743
*
52.0
a
Reaction conditions: HMF (2 mM),catalyst (200 mg), Na
2
CO
3
(2 mM), O
2
(10 bar), H O (20 mL),
2
3
73 K, 4 h. * Reaction conditions same as above without Na
2
CO
3
3
.3. Time course study
To understand the mechanism of this oxidation using our catalyst, time on stream investigations were
performed for FDCA. 1% Au/IRA-743 converted 85% of HMF in 1 h of reaction time with a 5-
hydroxymethylfuran-2-carboxylic acid (HMFCA) selectivity of 77%. As time progressed, the FDCA
selectivity increased from <5% at 0.5 h to 36% at 5 h at the expense of HMFCA, but the selectivity
of 5-formylfuran-2-carboxylic acid (FFCA) remained ~20% throughout the reaction. Though
additional FDCA may be formed for longer reaction intervals, it may not be economical for fine
chemicals (Fig 4a). 1% Pd/IRA-743 reacted different than Au did, i.e. the HMFCA selectivity
remained ~50% from 0.5 h to 5 h; similarly FFCA and FDCA selectivities also remained stable
throughout the reaction.

1
1
1
00
100
80
60
40
20
0
8
6
4
2
0
0
0
0
0
0
1
2
3
4
5
0
1
2
3
4
5
100
80
60
HMF
HMFCA
FFCA
40
FDCA
20
0
0
1
2
3
4
5
Time (h)
Fig. 4. Time course investigation on the oxidation of HMF using (a) 1% Au/IRA-743, (b) 1% Pd/IRA-
43, and (c) 2% Au-Pd(1:1)/IRA-743 (reaction conditions: HMF (2 mM), catalyst (200 mg), Na CO
2 mM), O (10 bar), H O (20 mL), 373 K.
7
2
3
(
2
2
This seems that the catalyst did not have the tendency to shift the equilibrium towards FDCA (Fig
b). 2% AuPd(1:1)/IRA-743 showed a 95% HMF conversion with a 61% FFCA selectivity in 0.5 h
of reaction time. As time progressed, the selectivity of FDCA also increased, reaching a 91%
4

1
2
selectivity in 3 h and 95% in 5 h (Fig 4c).The time on stream study also confirmed that the FDCA
produced was stable under the reaction conditions for a long time which makes it suitable for
industrial production. Interestingly, 2,5-diformylfuran (DFF) was not observed under our reaction
conditions unlike stoichiometric oxidant KMnO4 [31], enzyme [32-34], ruthenium-based catalysts
[
35,36], oxidizing HMF to FDCA via DFF intermediate, but HMF oxidation proceeded via HMFCA
intermediate. It meant that the AER-supported Au-Pd alloy nanoparticles could catalyze the oxidation
from aldehyde to carboxylic acid more effectively than the oxidation from alcohol to aldehyde. The
possible mechanism of this oxidation reaction is given in Fig. 4 and which similar to what was already
observed by Albonetti et. al [23].
3
.4. Effect of polymeric-supports and metal ratios
To understand the influence of the supporting resin, IRA-743 (macroporous-type resin) was compared
with other anion-exchange resins having different support morphologies like IRA-900 (gel-type
resin) and IRA-400 (macroreticular-type resin) and characterization of each anion-exchange resin
was summarized in Table 3. Au-Pd (1:1) was supported on different resins and the oxidation ability
was studied. Among the supports, IRA-743 was found to be highly active. 2% Au-Pd(1:1)/IRA-400
showed a 98% conversion with a 26% FDCA selectivity and 2% Au-Pd(1:1)/IRA-900 showed a 91%
conversion with a 5% FDCA selectivity (Table 4). From this result, the macroporous morphology
appears beneficial for access to substrate (HMF). However, BET surface area analyses of 2%
2
2
AuPd(1:1)/IRA-743, 2% AuPd(1:1)/IRA-400 and 2% AuPd(1:1)/IRA-900 are 19 m /g, 0 m /g and 2
2
m /g, respectively. The surface areas of all catalysts were very low, and they did not have a significant
influence on catalytic behavior. Instead, it was noticed that basicity of the resins could affect the
oxidation ability because the terminal functional groups of IRA-400 and IRA-900 are tetraalkyl
ammonium salts; on the other hand, the terminal fucntional group of IRA-743 is tertiary amine,
having a weaker basicity than the others [37]. To examine the influence of the palladium on the gold,
the ratio of Au-Pd was varied from 6:1 to 0.5:1 by maintaining a total metal loading of 2wt%, and the
results are given in Fig. 5. As the palladium concentration increased, the selectivity of FDCA also
increased, i.e. 2% AuPd(6:1)/IRA-743 had 100% conversion with a 55.1% FDCA selectivity whereas
2
% AuPd(1:1)/IRA-743 had 100% conversion with a 93.2% selectivity. A further increase in
palladium concentration did not show improvement in the FDCA selectivity, which might be due to
the decrease of the active metal (Au) concentration. The turnover number (TON) calculated for the
active 2% AuPd(1:1)/IRA-743 catalyst after 4 h was 65, which is comparable to other active catalysts
reported in the literature.

1
3
Table 3. Characterization of anion-exchange resins
Loading level
of ‘N’ content
Surface area
Name of
resin
Morphology of
resin
Chemical structure of
terminal group
2
(
m /g)
(
mmol/g)
Amberlite
IRA-743
Macroporous
18.76±0.08
0.03±0.02
20..±0.01
1.9
Amberlite
IRA-400
Gel
3.3
3.8
Amberlite
IRA-900
Macroreticular
Table 4. HMF conversion according to the morphology of the resin supports
Catalyst
HMF
Con%
FFCA
Sel%
FDCA
Sel%
HMFCA
Sel%
Others
Sel%
2
2
2
%AuPd (1:1)/IRA743
%AuPd (1:1)/IRA900
%AuPd (1:1)/IRA400
100.0
91.5
97.8
3.3
93.2
5.0
0.0
3.5
42.6
48.3
39.6
12.9
12.8
12.9
25.9

1
4
Fig. 5. According to the ratio of Au/Pd metals, the HMF conversion (red) and selectivity of FDCA
green) are shown. Reaction conditions: HMF (2 mM), catalyst (200 mg), Na CO (2 mM), O (10
bar), H O (20 mL), 373 K, 4 h.
(
2
3
2
2
3
.5. Reusability
Immediately after the reaction, the catalyst was filtered, washed with water, dried in vacuum and used
for new reaction; the results are given in Table 5. The catalyst was reusable up to 6 cycles without
any marginal change in the conversion and selectivity. No leaching of Au or Pd was detected in the
filtrates, and the reaction times were similarly kept for all runs; this proves the potential of the catalyst
to be extended for industrial production.
Table 5. HMF conversion and the selectivity of FFCA and FDCA using recycled AuPd(1:1)/IRA-
7
43.The reaction conditions are the same as Fig. 5
Cycle No
HMF Con. (%)
FFCA Sel. (%)
FDCA Sel. (%)
1
2
3
4
5
6
cycle
cycle
cycle
cycle
cycle
cycle
100
100
100
100
100
100
2.7
5.0
8.0
6.5
6.7
6.9
96.8
95.0
92.0
93.5
93.3
93.1

1
5
3
.6. Practical approach
For bringing this reaction close to a practical application, HMF produced from our laboratory
KITECH HMF) using high fructose corn syrup (HFCS) was used for this oxidation [38]. Both
(
Aldrich HMF and our HMF were studied under similar reaction conditions, and both showed 100%
conversion and FDCA selectivities of 93.2% and 91.9% respectively. It is clear that our catalyst was
not only active for pure commercial HMF but also for crude HMF synthesized in our laboratory. The
reaction was also conducted using air as the oxidant. Previously, HMF oxidation to FDCA using Au-
Pd alloy supported on carbon nanotube [18] or zinc hydroxycarbonate [22] used molecular oxygen
as an oxidant. The AER-supported Au-Pd afforded 100% HMF conversion with 82.9% FDCA
selectivity using an air pressure of 40 bar (Table 6).
Table 6. Influence of HMF source on oxidation a
HMF
Selectivity (%)
FFCA
Source
Conversion
HMFCA
FDCA
(%)
Aldrich HMF
KITECH HMF
Aldrich HMF b
100
100
100
0
0
3.3
8.9
2.2
93.2
91.9
82.9
14.9
a
Reaction conditions: HMF (2 mM), Au-Pd(1:1)/IRA-743 (200 mg), Na
2
CO
3
(2 mM), O (10 bar),
2
H
2
O (20 mL), 373 K, 4 h
b
Air (40 bar) used instead of O .
2

1
6
4
. Conclusion
In summary, we report the simple synthesis of Au-Pd alloy nanoparticles supported on basic anion-
exchange resins and its application to efficient oxidation of HMF to FDCA. Cross-sectional SEM-
EDX analysis confirms that alloy particles are present both on the surface and in the cross-section
of the resin spheres and XPS shows that the Au- and Pd metals exist in an alloy form. A 1:1 ratio of
Au-Pd supported on Amberlite IRA-743 resin having a terminal functional group of a tertiary amine
gives FDCA from HMF in a great yield (93.2%) with O
2
(10 bar) at 373 K in an equimolar Na
2
CO
3
aqueous solution and this catalyst can be used 6 times without any significant loss of activity.
FDCA is also obtained from HMF with an 82.9% yield in air (40 bar).
Acknowledgement
This work was financially supported by the National Research Council of Science & Technology
NST) grant by the Korea government (No. CAP-11-04-KIST) and we acknowledge financial
(
support for this research by the Internal Research Program (PEO17250 & PJB17130) of Korea
Institute of Industrial Technology (KITECH).

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