CsxH3-0-xPW12O40 (X = 2.0-3.0) heteropolyacid nano-catalysts for catalytic decomposition of 2,3-dihydrobenzofuran to aromatics

Article abstract of DOI:10.1166/jnn.2014.9947

Cesium-exchanged Cs_xH_3-0-xPW₁₂O₄₀ (X = 2.0, 2.3, 2.5, 2.8, and 3.0) heteropolyacid nanocatalysts were prepared, and they were applied to the catalytic decomposition of lignin model compound to aromatics. Success

Full text of DOI:10.1166/jnn.2014.9947

Article
Journal of
Nanoscience and Nanotechnology
Vol. 14, 8884–8890, 2014
Copyright © 2014 American Scientific Publishers
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CsxH3ꢀ0−xPW12O40 (X = 2.0–3.0) Heteropolyacid
Nano-Catalysts for Catalytic Decomposition of
2,3-Dihydrobenzofuran to Aromatics
Jeong Kwon Kim, Hai Woong Park, Ung Gi Hong, Jung Ho Choi, and In Kyu Song∗
School of Chemical and Biological Engineering, Institute of Chemical Processes, Seoul National University,
Shinlim-Dong, Kwanak-Ku, Seoul 151-744, South Korea
Cesium-exchanged Csx H3ꢀ0−x PW12O40 (X = 2.0, 2.3, 2.5, 2.8, and 3.0) heteropolyacid nano-
catalysts were prepared, and they were applied to the catalytic decomposition of lignin model com-
pound to aromatics. Successful formation of cesium-exchanged Csx H3ꢀ0−x PW12O40 (X = 2ꢀ0–3.0)
catalysts was confirmed by FT-IR, ICP-AES, and XRD measurements. 2,3-Dihydrobenzofuran was
employed as a lignin model compound for representing ꢁ-5 bond in lignin. Phenol, ethylbenzene,
and 2-ethylphenol were mainly produced by the catalytic decomposition of 2,3-dihydrobenzofuran.
Conversion of 2,3-dihydrobenzofuran and total yield for main products (phenol, ethylbenzene, and
2-ethylphenol) were closely related to the surface acidity of Csx H3ꢀ0−x PW12O40 (X = 2ꢀ0–3.0) cata-
lysts. Conversion of 2,3-dihydrobenzofuran and total yield for main products increased with increas-
ing surface acidity of the catalysts. Among the catalysts tested, Cs2ꢀ5H0ꢀ5PW12O40 with the largest
surface acidity showed the highest conversion of 2,3-dihydrobenzofuran and the highest total yield
for main products. These results indicate that surface acidity of Csx H3ꢀ0−x PW12O40 (X = 2ꢀ0–3.0)
catalysts served as an important factor determining the catalytic performance in the decomposition
of 2,3-dihydrobenzofuran to aromatics.
Keywords: Lignin, 2,3-Dihydrobenzofuran, Heteropolyacid Catalyst, Aromatics, Decomposition.
1. INTRODUCTION
However, these mineral acids involve many drawbacks in
an environmental point of view, because their corrosive
and homogeneous properties cause corrosion of reaction
system and disposable problem. Other catalysts examined
for lignin decomposition include Mo- or W- based sulfides
supported on alumina.9–12 Hydrocracking over these cata-
lysts requires severe reaction conditions such as high tem-
perature and high pressure. For effective decomposition of
lignin, therefore, it is necessary to develop an environmen-
tal benign catalyst that can give high catalytic activity and
stable performance under mild reaction conditions.
It has been reported that acid strength of heteropoly-
acids (HPAs) is stronger than that of conventional solid
acids.13ꢀ14 For this reason, HPAs have been widely uti-
lized as solid acid nano-catalysts in several acid-catalyzed
reactions.13–17 HPAs salt with K+, Cs+, and NH+4 cations
have high surface area and porous structure by form-
ing a tertiary structure.13 It is well known that sur-
face acidity of cation-exchanged HPAs varies depending
As one of the most significant renewable resources,
biomass has attracted much attention to reduce carbon
dioxide emission and global dependency on fossil fuels.1
In particular, lignin has received continuous attention as a
valuable biomass, because it does not compete with food
resources.2ꢀ3 In addition, lignin, which is an amorphous
polymer comprising aromatic compounds, is regarded as
the richest source of aromatics in nature.4ꢀ5 Therefore,
decomposition of lignin to aromatics becomes as an advan-
tageous technology for producing aromatics as biofuels.
Catalytic decomposition of lignin has attracted signif-
icant interest as a promising technology for the produc-
tion of aromatic compounds, because polymeric lignin is
thermally stable.6ꢀ7 Conventional catalytic process for the
production of aromatic compounds is based on cleavage
of C O bond over acid catalysts such as HCl and HI.8
∗Author to whom correspondence should be addressed.
8884
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1533-4880/2014/14/8884/007
doi:10.1166/jnn.2014.9947

Kim et al.
Catalytic Decomposition of 2,3-Dihydrobenzofuran
2.3. Catalytic Decomposition of
on cation content. For example, surface acidity of
CsxH3ꢁ0−xPW12O40 (X = 2ꢁ0–3.0) shows a volcano-shaped
trend with respect to cesium content within the range of
X = 2ꢁ0–3.0.13ꢀ14ꢀ16
2,3-Dihydrobenzofuran
Decomposition of 2,3-dihydrobenzofuran over cesium-
exchanged CsxH3ꢁ0−xPW12O40 (X = 2ꢁ0–3.0) nano-
catalysts was carried out in a stainless steel autoclave
reactor (25 ml) under nitrogen atmosphere. Tetralin
Due to the complex structure of lignin,18 stud-
ies on lignin decomposition have been simplified by
employing lignin model compounds rather than lignin
itself.5ꢀ18 Among various lignin model compounds, 2,3-
dihydrobenzofuran has been widely used as a model com-
pound for representing ꢂ-5 bond in lignin.7ꢀ18
(Sigma-Aldrich) was used as
a solvent for 2,3-
dihydrobenzofuran (Sigma-Aldrich) and as a hydrogen
donor in the decomposition of 2,3-dihydrobenzofuran.
0.05 g of CsxH3ꢁ0−xPW12O40 (X = 2ꢁ0, 2.3, 2.5, 2.8,
and 3.0) and a mixture of 2,3-dihydrobenzofuran (1 ml),
tetralin (15 ml), and hexadecane (1 ml, an internal stan-
dard) were charged into the reactor at room temperature.
The reactor was purged with nitrogen several times in
order to remove air. The reactor was then heated to reac-
tion temperature (250 ꢀC). The reaction was carried out for
1 h at nitrogen pressure of 30 bar in order to prevent vapor-
ization of reaction mixture. After 1 h-reaction, reaction
products were sampled and analyzed using a gas chro-
matograph (Younglin, YL6100 GC-FID) equipped with a
capillary column (Agilent, DB-5MS, 60 m × 0.320 mm).
Conversion of 2,3-dihydrobenzofuran and selectivity for
product (phenol, ethylbenzene or 2-ethylphenol) were
calculated according to the following equations on the
basis of mole balance. Yield for product (phenol, ethyl-
benzene or 2-ethylphenol) was calculated by multiplying
conversion of 2,3-dihydrobenzofuran and corresponding
product selectivity. For comparison, commercial HZSM-5
(Zeolyst International, Si/Al = 50) was also employed for
the decomposition of 2,3-dihydrobenzofuran.
In this work, cesium-exchanged CsxH3ꢁ0−xPW12O40
nano-catalysts were prepared with a variation of cesium
content (X = 2ꢁ0, 2.3, 2.5, 2.8, and 3.0), and they were
applied to the catalytic decomposition of 2,3-dihydro-
benzofuran (a lignin model compound) to aromatics.
Correlations between catalytic performance and surface
acidity of CsxH3ꢁ0−xPW12O40 (X = 2ꢁ0–3.0) nano-catalysts
were then established and discussed.
2. EXPERIMENTAL DETAILS
2.1. Catalyst Preparation
Cesium-exchanged CsxH3−xPW12O40 (X = 2.0–3.0) het-
eropolyacid nano-catalysts were prepared according to the
method reported in the literatures.13ꢀ16 Commercially avail-
able H3PW12O40 (Sigma-Aldrich) was thermally treated
at 300 ꢀC for 2 h for precise quantification, prior to
the preparation of cesium-exchanged heteropolyacid nano-
catalysts. A series of cesium-exchanged heteropolyacid
nano-catalysts (CsxH3ꢁ0−xPW12O40) were prepared by an
ion exchange method with a variation of cesium content
(X = 2ꢁ0, 2.3, 2.5, 2.8, and 3.0). A known amount of
cesium nitrate (CsNO3, Sigma-Aldrich) was dissolved in
distillated water. The solution was added dropwise into
an aqueous solution containing H3PW12O40 with constant
stirring. The resulting solution was then slowly heated at
Conversion of 2,3-dihydrobenzofuran
moles of 2,3-dihydrobenzofuran reacted
=
(1)
moles of 2,3-dihydrobenzofuran supplied
Selectivity for product
ꢀ
60 C for 12 h to obtain a solid. The solid product was
(phenol, ethylbenzene or 2-ethylphenol)
dried overnight at 70 ꢀC, and then it was calcined at 300 ꢀC
for 2 h to yield CsxH3ꢁ0−xPW12O40 (X = 2ꢁ0, 2.3, 2.5, 2.8,
and 3.0) catalysts.
= moles of phenol, ethylbenzene or 2-ethylphenol formed
·ꢅmoles of 2,3-dihydrobenzofuran reactedꢆ−1
Total selectivity for main products
= Total moles of phenol, ethylbenzene or
and 2-ethylphenol formed
(2)
2.2. Catalyst Characterization
Successful
formation
of
cesium-exchanged
CsxH3−xPW12O40 (X = 2.0–3.0) nano-catalysts was con-
firmed by FT-IR (Nicolet, Nicolet 6700) measurements.
Chemical compositions of constituent elements in the
CsxH3ꢁ0−xPW12O40 (X = 2.0–3.0) catalysts were deter-
mined by ICP-AES (Shimadzu, ICP-1000IV) analyses.
Crystalline phases of the catalysts were investigated by
XRD (Rigaku, D-MAX2500-PC) measurements using
Cu-Kꢃ radiation (ꢄ = 1ꢁ541 Å) operated at 40 kV
and 20 mA. Crystal size and morphology of the cat-
alysts were examined by SEM (Jeol, JSM-ꢀ6700F).
All the catalysts were thermally treated at 300 C in a
stream of nitrogen prior to characterization and catalytic
reaction.
·ꢅmoles of 2,3-dihydrobenzofuran reactedꢆ−1 (3)
Total yield for main products
= ꢅConversion of 2,3-dihydrobenzofuranꢆ
×ꢅTotal selectivity for main productsꢆ
(4)
3. RESULTS AND DISCUSSION
3.1. Catalysts Characterization
Successful formation of CsxH3ꢁ0−xPW12O40 (X = 2.0–3.0)
heteropolyacid (HPA) catalysts was confirmed by FT-IR
J. Nanosci. Nanotechnol. 14, 8884–8890, 2014
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Catalytic Decomposition of 2,3-Dihydrobenzofuran
Kim et al.
Table I. Chemical compositions of cesium, phosphorous, and tungsten
in the CsxH3ꢁ0−xPW12O40 (X = 2.0–3.0) catalysts determined by ICP-AES
analyses.
Cs3.0PW12O40
Ratio of Cs:P:W
Catalyst
Theoretical value
Measured value
Cs2.8H0.2PW12O40
Cs2.5H0.5PW12O40
Cs2.3H0.7PW12O40
Cs2ꢁ0H1ꢁ0PW12O40
Cs2ꢁ3H0ꢁ7PW12O40
Cs2ꢁ5H0ꢁ5PW12O40
Cs2ꢁ8H0ꢁ2PW12O40
Cs3ꢁ0PW12O40
2.0:1.0:12.0
2.3:1.0:12.0
2.5:1.0:12.0
2.8:1.0:12.0
3.0:1.0:12.0
1.9:1.0:12.0
2.3:1.0:12.0
2.5:1.0:12.0
2.8:1.0:12.0
3.0:1.0:12.0
changed. This result was in good agreement with the
precious work,20ꢀ21 indicating successful formation of
CsxH3ꢁ0−xPW12O40 (X = 2.0–3.0) heteropolyacid catalysts.
Crystal size and morphology of CsxH3ꢁ0−xPW12O40
(X = 2.0–3.0) catalysts were examined by SEM analyses.
Figure 3 shows the SEM images of CsxH3ꢁ0−xPW12O40
(X = 2.0–3.0) catalysts and their crystal size distribution.
It was observed that crystallites of cesium-exchanged het-
eropolyacid catalysts were composed of elementary parti-
cles, which were agglomerated in large-spherical particles
within the range of 30–260 nm. Crystal size of het-
eropolyacids increased with increasing cesium content
(X). This result was well consistent with the previous
reports.22ꢀ23
Cs2.0H1.0PW12O40
P-O
W=O
W-O-W
900
1200
1100
1000
800
700
Wavenumber (cm–1
)
Figure 1. FT-IR spectra of CsxH3ꢁ0−xPW12O40 (X = 2.0–3.0) catalysts.
analyses, which provided information about the main-
tenance of heteropolyacid structure.13 FT-IR spectra of
CsxH3ꢁ0−xPW12O40 (X = 2.0–3.0) catalysts are shown in
Figure 1. The structure of CsxH3ꢁ0−xPW12O40 (X = 2.0–
3.0) catalysts could be identified by four characteristic IR
bands appearing in the range of 700–1200 cm−1. The four
characteristic IR bands of CsxH3ꢁ0−xPW12O40 (X = 2.0–
3.0) catalysts appeared at 1080 cm−1 (P O), 985 cm−1
3.2. Catalytic Performance in the Decomposition of
2,3-Dihydrobenzofuran
Cleavage of dihydrofuran ring in the 2,3-
dihydrobenzofuran over acid catalysts mainly produces
2-ethylphenol.8 Figure 4 shows that 2-ethylphenol is
produced by the primary cleavage of ꢂ-5 bond in the 2,3-
dihydrobenzofuran over CsxH3ꢁ0−xPW12O40. 2-Ethylphenol
is further converted to phenol and ethylbenzene through
the secondary reaction over the catalysts. As shown
in Figure 4, aromatic compounds such as phenol,
(W O), 890 cm−1 (inter-octahedral W
810 cm−1 (intra-octahedral W
W), in good agree-
O
W), and
O
ment with the characteristic IR bands of H3PW12O40.
This result was well consistent with the previous work,19
indicating successful formation of CsxH3ꢁ0−xPW12O40 (X =
2.0–3.0) heteropolyacid catalysts.
Successful formation of CsxH3ꢁ0−xPW12O40 (X = 2.0–
3.0) catalysts was further confirmed by ICP-AES anal-
yses. Chemical compositions of cesium, phosphorous,
and tungsten in the CsxH3ꢁ0−xPW12O40 (X = 2.0–3.0)
catalysts determined by ICP-AES analyses are summa-
rized in Table I. The measured Cs:P:W ratios in the
CsxH3ꢁ0−xPW12O40 (X = 2.0–3.0) catalysts were in good
agreement with the theoretical values.
Cs3.0PW12O40
Cs2.8H0.2PW12O40
Cs2.5H0.5PW12O40
In order to examine the crystalline phase of
CsxH3ꢁ0−xPW12O40 (X = 2.0–3.0) heteropolyacid cata-
lysts, XRD measurements were carried out. Figure 2
shows the XRD patterns of CsxH3ꢁ0−xPW12O40 (X = 2.0–
3.0) catalysts. It was observed that CsxH3ꢁ0−xPW12O40
(X = 2.0–3.0) catalysts exhibited the same diffraction
patterns corresponding to cubic phase of Pn3m crys-
talline structure, indicating that the crystalline struc-
ture of CsxH3ꢁ0−xPW12O40 (X = 2.0–3.0) was not
Cs2.3H0.7PW12O40
Cs2.0H1.0PW12O40
5
10
15
20
25
30
35
40
45
50
2 Theta (Degree)
Figure 2. XRD patterns of CsxH3ꢁ0−xPW12O40 (X = 2.0–3.0) catalysts.
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Kim et al.
Catalytic Decomposition of 2,3-Dihydrobenzofuran
25
20
15
10
5
Cs2.0H1.0PW12O40
Cs2.5H0.5PW12O40
Cs3.0PW12O40
0
500nm
500nm
500nm
30 40 50 60 70 80 90 100
Crystal size (nm)
25
20
15
10
5
0
130 140 150 160 170 180 190 200
Crystal size (nm)
25
20
15
10
5
0
190 200 210 220 230 240 250 260
Crystal size (nm)
Figure 3. SEM images of CsxH3ꢁ0−xPW12O40 (X = 2.0–3.0) catalysts and their crystal size distribution.
ethylbenzene, and 2-ethylphenol are mainly produced in
the decomposition of 2,3-dihydrobenzofuran.
(2.3–4.7%), because phenol and ethylbenzene were
produced by the secondary reaction of 2-ethylphenol.
Among the secondary products, selectivity for phenol
(15.5–20.2%) was higher than that for ethylbenzene (2.3–
4.7%). Selectivity for by-products such as light hydro-
carbons (C2–C8) and alcohols was in the range of
30.3–37.3%.
Yield for 2-ethylphenol (10.4–28.1%) was much higher
than that for phenol (3.7–12.6%) and ethylbenzene (0.9–
2.7%). Yield for phenol (3.7–12.6%) was higher than
that for ethylbenzene (0.9–2.7%). Total selectivity for
main products (phenol, ethylbenzene, and 2-ethylphenol)
over CsxH3ꢁ0−xPW12O40 was in the range of 62.7–
69.7%. Total yield for main products (phenol, ethylben-
zene, and 2-ethylphenol) over CsxH3ꢁ0−xPW12O40 was in
the range of 15.2–43.4%. Among the catalysts tested,
Catalytic performance of CsxH3ꢁ0−xPW12O40 (X = 2ꢁ0,
2.3, 2.5, 2.8, and 3.0) in the decomposition of 2,3-
dihydrobenzofuran performed at 250 ꢀC and 30 bar for 1 h
is listed in Table II. Conversion of 2,3-dihydrobenzofuran
over CsxH3ꢁ0−xPW12O40 was in the range of 23.5–62.2%.
Selectivity for 2-ethylphenol (40.2–45.2%) was much
higher than that for phenol (15.5–20.2%) and ethylbenzene
OH
+
H
Phenol
O
OH
2,3-Dihydrobenzofuran
2-Ethylphenol
Ethylbenzene
Cs2ꢁ5H0ꢁ5PW12O40 catalyst showed the best catalytic per-
formance in terms of conversion of 2,3-dihydrobenzofuran
and total yield for main products (Table II).
Figure 4. Scheme for the decomposition of 2,3-dihydrobenzofuran over
CsxH3ꢁ0−xPW12O40.
J. Nanosci. Nanotechnol. 14, 8884–8890, 2014
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Catalytic Decomposition of 2,3-Dihydrobenzofuran
Kim et al.
Table II. Catalytic performance of CsxH3ꢁ0−xPW12O40 (X = 2ꢁ0, 2.3,
2.5, 2.8, and 3.0) in the decomposition of 2,3-dihydrobenzofuran per-
formed at 250 ꢀC and 30 bar for 1 h.
40
35
30
25
20
15
10
5
Ethylbenzene
Phenol
2-Ethylphenol
X in CsxH3ꢁ0−xPW12O40 (X = 2ꢁ0–3.0)
X = 2ꢁ0 X = 2ꢁ3 X = 2ꢁ5 X = 2ꢁ8 X = 3ꢁ0
Conversion (%)
Total selectivity for main 63ꢁ0
productsa (%)
37ꢁ7
52ꢁ4
65ꢁ6
62ꢁ2
69ꢁ7
58ꢁ4
62ꢁ7
23ꢁ5
64ꢁ6
Phenol (%)
16ꢁ3
2ꢁ3
44ꢁ4
23ꢁ7
17ꢁ2
3ꢁ4
45ꢁ0
33ꢁ4
20ꢁ2
4ꢁ3
45ꢁ2
43ꢁ4
20ꢁ0
2ꢁ5
40ꢁ2
36ꢁ7
15ꢁ5
4ꢁ7
44ꢁ4
15ꢁ2
Ethylbenzene (%)
2-Ethylphenol (%)
Total yield for main
productsb (%)
0
2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0
Phenol (%)
Ethylbenzene (%)
2-Ethylphenol (%)
6ꢁ1
0ꢁ9
16ꢁ7
9ꢁ0
1ꢁ8
23ꢁ6
12ꢁ6
2ꢁ7
28ꢁ1
11ꢁ7
1ꢁ5
23ꢁ5
3ꢁ7
1ꢁ1
10ꢁ4
X in CsxH3.0-xPW12O40
Figure 6. Yields for phenol, ethylbenzene, and 2-ethylphenol plotted as
a function of cesium content.
a
Notes: Calculated by Eq. (3); bCalculated by Eq. (4).
3.3. Effect of Cesium Content on the
Catalytic Performance
As mentioned above, yield for 2-ethylphenol was much
higher than that for phenol and ethylbenzene.
Figure
5
shows the catalytic performance of
CsxH3ꢁ0−xPW12O40 catalysts in the decomposition of
2,3-dihydrobenzofuran plotted as a function of cesium
content. Conversion of 2,3-dihydrobenzofuran showed
a volcano-shaped curve with respect to cesium content.
Total yield for main products also showed a volcano-
shaped curve with respect to cesium content. Among
the catalysts tested, Cs2ꢁ5H0ꢁ5PW12O40 catalyst showed
the best catalytic performance in terms of conversion of
2,3-dihydrobenzofuran and total yield for main products.
Figure 6 shows the yields for phenol, ethylbenzene,
and 2-ethylphenol plotted as a function of cesium con-
tent. Yields for phenol, ethylbenzene, and 2-ethylphenol
showed volcano-shaped curves with respect to cesium
content. Among the catalysts tested, Cs2ꢁ5H0ꢁ5PW12O40
catalyst showed the best catalytic performance in terms
of yields for phenol, ethylbenzene, and 2-ethtylphenol.
3.4. Effect of Surface Acidity on the
Catalytic Performance
Figure 7(a) shows the correlation between conversion of
2,3-dihydrobenzofuran over CsxH3ꢁ0−xPW12O40 catalysts
and surface acidity of CsxH3ꢁ0−xPW12O40 catalysts. Sur-
face acidity data of CsxH3ꢁ0−xPW12O40 catalysts were taken
from a literature.24 Conversion of 2,3-dihydrobenzofuran
increased with increasing surface acidity of cesium-
exchanged heteropolyacid (HPA) catalysts. This result
clearly shows that conversion of 2,3-dihydrobenzofuran
is closely related to the surface acidity of the catalysts.
Among the catalysts examined, Cs2ꢁ5H0ꢁ5PW12O40 catalyst
with the largest surface acidity showed the highest conver-
sion of 2,3-dihydrobenzofuran.
Figure 7(b) shows the correlation between total yield for
main products (phenol, ethylbenzene, and 2-ethylphenol)
over CsxH3ꢁ0−xPW12O40 catalysts and surface acidity of
CsxH3ꢁ0−xPW12O40 catalysts. Total yield for main products
increased with increasing surface acidity of the catalysts.
This result also shows that total yield for main products
is closely related to the surface acidity of the catalysts.
Thus, cesium-exchanged CsxH3ꢁ0−xPW12O40 heteropoly-
acid nano-catalysts served as an efficient acid catalyst in
the decomposition of 2,3-dihydrobenzofuran to aromatics.
It is concluded that surface acidity of CsxH3ꢁ0−xPW12O40
heteropolyacid nano-catalysts played an important role in
determining the catalytic performance in the decomposi-
tion of 2,3-dihydrobenzofuran.
80
Conversion of 2,3-dihydrobenzofuran
Total yield for main products
70
60
50
40
30
20
10
2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0
3.5. Comparison of Catalytic Performance Between
Cs2ꢁ5H0ꢁ5PW12O40 Catalyst and HZSM-5 Catalyst
in the Decomposition of 2,3-Dihydrobenzofuran
In order to compare the performance of acid cataly-
sis, commercial HZSM-5 was employed as a catalyst
X in CsxH3.0-xPW12O40
Figure 5. Catalytic performance of CsxH3ꢁ0−xPW12O40 catalysts in the
decomposition of 2,3-dihydrobenzofuran plotted as a function of cesium
content.
8888
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Kim et al.
Catalytic Decomposition of 2,3-Dihydrobenzofuran
(a)
(b)
50
40
30
20
10
70
60
50
40
30
20
Cs2.5H0.5PW12O40
Cs2.5H0.5PW12O40
Cs2.8H0.2PW12O40
Cs2.8H0.2PW12O40
Cs2.3H0.7PW12O40
Cs2.3H0.7PW12O40
Cs2.0H1.0PW12O40
Cs2.0H1.0PW12O40
Cs3.0PW12O40
Cs3.0PW12O40
10 20
0
30
40
50
60
0
10
20
30
40
50
60
Surface acidity (µmol-NH3/g)
Surface acidity (µmol-NH3/g)
Figure 7. Correlations (a) between conversion of 2,3-dihydrobenzofuran over CsxH3ꢁ0−xPW12O40 and surface acidity of CsxH3ꢁ0−xPW12O40, and (b)
between total yield for main products (phenol, ehtylbenzene, and 2-ethylphenol) over CsxH3ꢁ0−xPW12O40 and surface acidity of CsxH3ꢁ0−xPW12O40.
Surface acidity data were taken from a literature.28
100
measurements. 2,3-Dihydrobenzofuran was used as a
lignin model compound for representing ꢂ-5 bond in
lignin. Conversion of 2,3-dihydrobenzofuran and total
yield for main products (phenol, ethylbenzene, and
Conversion of 2,3-dihydrobenzofuran
Total selectivity for main products
80
Total yield for main products
2-ethylphenol) over CsxH3ꢁ0−xPW12O40 (X = 2ꢁ0–3.0)
60
catalysts were in the range of 23.5–62.2% and 15.2–
43.4%, respectively. Conversion of 2,3-dihydrobenzofuran
40
and total yield for main products were closely related
to the surface acidity of CsxH3ꢁ0−xPW12O40 catalysts.
Among the catalysts tested, Cs2ꢁ5H0ꢁ5PW12O40 catalyst
20
with the largest surface acidity showed the highest con-
version of 2,3-dihydrobenzofuran and total yield for
main products. It is concluded that surface acidity of
CsxH3ꢁ0−xPW12O40 catalysts played an important role in
determining the catalytic performance in the decomposi-
tion of 2,3-dihydrobenzofuran to aromatics.
0
HZSM-5
Cs2.5H0.5PW12O40
Catalyst
Figure 8. Comparison
Cs2ꢁ5H0ꢁ5PW12O40 and HZSM-5 in the decomposition of 2,3-
dihydrobenzofuran.
of
catalytic
performance
between
Acknowledgments: This work was supported by the
National Research Foundation of Korea Grant funded by
the Korean Government (MEST) (NRF-2009-C1AAA001-
0093292).
for the decomposition of 2,3-dihydrobenzofuran. Figure 8
shows the comparison of catalytic performance between
Cs2ꢁ5H0ꢁ5PW12O40 and HZSM-5 in the decomposition of
2,3-dihydrobenzofuran at the reaction conditions. Con-
version of 2,3-dihydrobenzofuran over Cs2ꢁ5H0ꢁ5PW12O40
(62.2%) was much higher than that over HZSM-5 (38.2%).
Total yield for main products over Cs2ꢁ5H0ꢁ5PW12O40 cat-
alyst (43.4%) was much higher than that over HZSM-
5 catalyst (25.0%). Thus, Cs2ꢁ5H0ꢁ5PW12O40 was more
efficient than HZSM-5 in the decomposition of 2,3-
dihydrobenzofuran to aromatics.
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Received: 11 March 2013. Accepted: 18 February 2014.
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