Catalytic decomposition of 4-phenoxyphenol to aromatics over palladium catalysts supported on activated carbon aerogel bearing sulfonic acid group

Article abstract of DOI:10.1016/j.catcom.2012.01.016

A series of activated carbon aerogel (ACA) bearing sulfonic acid group (SO₃H) was prepared at different sulfonation temperatures (ACA-SO₃H (X), X = 30, 60, 90, 120, and 150 in Celsius). Palladium catalysts were then supported on ACA-SO₃H (X) (Pd/ACA-SO₃H (X)) for use in the decomposition of 4-phenoxyphenol to aromatics. 4-Phenoxyphenol was used as a lignin model compound for representing 4-O-5 bond in lignin. Acidity of Pd/ACA-SO₃H (X) catalysts played an important role in the reaction. Among the catalysts tested, Pd/ACA-SO₃H (90) with the largest acidity showed the highest conversion of 4-phenoxyphenol and total yield for main products (cyclohexanol, benzene, and phenol).

Full text of DOI:10.1016/j.catcom.2012.01.016

Catalysis Communications 20 (2012) 89–93
Contents lists available at SciVerse ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
Catalytic decomposition of 4-phenoxyphenol to aromatics over palladium catalysts
supported on activated carbon aerogel bearing sulfonic acid group
Hai Woong Park, Ung Gi Hong, Yoon Jae Lee, 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
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of activated carbon aerogel (ACA) bearing sulfonic acid group (\SO H) was prepared at different sul-
3
Received 28 October 2011
Received in revised form 10 January 2012
Accepted 16 January 2012
Available online 24 January 2012
fonation temperatures (ACA-SO
supported on ACA-SO H (X) (Pd/ACA-SO
matics. 4-Phenoxyphenol was used as a lignin model compound for representing 4-O-5 bond in lignin. Acid-
ity of Pd/ACA-SO H (X) catalysts played an important role in the reaction. Among the catalysts tested, Pd/
ACA-SO H (90) with the largest acidity showed the highest conversion of 4-phenoxyphenol and total yield
for main products (cyclohexanol, benzene, and phenol).
3
H (X), X=30, 60, 90, 120, and 150 in Celsius). Palladium catalysts were then
3
3
H (X)) for use in the decomposition of 4-phenoxyphenol to aro-
3
3
Keywords:
Lignin
C\O bond
© 2012 Elsevier B.V. All rights reserved.
Pd/ACA-SO
-Phenoxyphenol
Aromatics
3
H
4
1
. Introduction
compounds, 4-phenoxyphenol has been widely employed for repre-
senting 4-O-5 bond in lignin [12,13].
Fossil fuels such as coal and crude oil are not sustainable [1–3].
Catalytic decomposition of lignin has been considered as an advan-
tageous technology for producing aromatics because thermal cracking
requires high temperature (over 450 °C) and pressure (over 100 atm)
for considerable performance [14,15]. Selective cleavage of C\O bond
in the lignin over novel metal catalyst supported on activated carbon
is known to be an efficient technology for the decomposition of lignin
Furthermore, carbon dioxide from burning of fossil fuels has been
considered as a contributor to global warming. Biomass has received
much attention as an environmental and sustainable energy resource,
because biofuels can reduce the dependence on fossil fuel and carbon
dioxide emission [4].
First generation biofuels derived from corn sugar and vegetable oil
are environmentally friendly, but feedstocks for first generation bio-
fuels are limited and compete with food resource. However, second
generation biofuels derived from lignocellulosic feedstocks do not
compete with food resource [5,6]. Moreover, lignin, which is a com-
ponent of lignocelluloses, is the richest source of aromatics in nature
to aromatics [16]. Liquid acid such as H and solid acid such as Cs-
3
PO
4
exchanged heteropolyacid (Cs H3.0 − xPW12O40, X=2.0–3.0) are also
x
known as promising catalysts for the decomposition of lignin to aro-
matics [17,18].
Activated carbon aerogel has received much attention as catalyst
support, electrochemical capacitor, and adsorbent, because activated
carbon aerogel provides both micropores and mesopores [19]. Pore
structure of activated carbon aerogel can be controlled by adjusting
activation conditions such as activation agent, ratio of activation
agent with respect to carbon aerogel, activation temperature, and ac-
tivation time.
[7,8]. Therefore, decomposition of lignin to aromatics has received
much attention as an advantageous technology for producing aro-
matics as biofuels.
In order to investigate decomposition mechanism of lignin inner
bond, dimeric lignin model compounds for representing C\O and
C\C bonds in lignin have been used as a lignin feedstock due to the
complex structure of lignin [9–11]. Therefore, dimeric chemical
compounds containing C\O bond such as β-O-4, α-O-5, and 4-O-5
have been used as lignin model compounds, because C\O bonds are
abundant linkage type in the lignin. Among various lignin model
In this work, activated carbon aerogel (ACA) was prepared by acti-
vating carbon aerogel with H
with H SO to obtain activated carbon aerogel bearing sulfonic acid
group (ACA-SO H (X), X=30, 60, 90, 120, and 150 in Celsius). Palladi-
um catalysts supported on activated carbon aerogel bearing sulfonic
acid group (Pd/ACA-SO H (X)) were then prepared by an incipient
3 4
PO , and subsequently, it was sulfonated
2
4
3
3
wetness impregnation method, and they were applied to the decom-
position of 4-phenoxyphenol to aromatics. 4-Phenoxyphenol was
chosen as a lignin model compound for representing 4-O-5 bond in
⁎
Corresponding author. Tel.: +82 2 880 9227; fax: +82 2 889 7415.
E-mail address: inksong@snu.ac.kr (I.K. Song).
1566-7367/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.catcom.2012.01.016

90
H.W. Park et al. / Catalysis Communications 20 (2012) 89–93
lignin. For comparison, palladium catalyst supported on activated car-
bon aerogel (Pd/ACA) was also employed for the decomposition of 4-
phenoxyphenol to aromatics. This is the first example reporting the
according to the following equations. Yield for product (cyclohexanol,
benzene, and phenol) was calculated by multiplying conversion of 4-
phenoxyphenol and corresponding product selectivity.
Conversion of 4-phenoxyphenol
catalytic performance of Pd/ACA-SO
3
H (X) in the decomposition of
lignin model compound to aromatics.
¼
moles of 4ꢀphenoxyphenol reacted :
ð1Þ
2
. Experimental
moles of 4ꢀphenoxyphenol supplied
2
.1. Preparation of palladium catalysts supported on ACA-SO
3
H (X)
Total selectivity for main products
Total moles of cyclohexanol; benzene; and phenol formed
moles of 4ꢀphenoxyphenol reacted
Carbon aerogel (CA) and activated carbon aerogel (ACA) were
prepared according to the method in the literature [20]. 2 g phospho-
ric acid (H PO ) was dissolved in 10 ml DI water and 2 g carbon aero-
¼
:
ð2Þ
3
4
gel was dispersed into an aqueous solution of phosphoric acid. After
Total yield for main products
stirring the solution for 1 h, the solid was filtered and dried at
1
10 °C for 3 h. The mixture of phosphoric acid and carbon aerogel
¼ ðConversion of 4ꢀphenoxyphenolÞ
ðTotal selectivity for main productsÞ:
ꢁ
ð3Þ
was heated to react at 800 °C for 1 h under N stream to obtain acti-
2
vated carbon aerogel. The containing phosphoric acid in activated
carbon aerogel was washed off by DI water till the pH value of solu-
tion reached ca. 7. The residual material was finally dried at 110 °C
for 5 h to obtain activated carbon aerogel (ACA).
3. Results and discussion
Activated carbon aerogel bearing sulfonic acid group (ACA-SO
X)) was prepared by sulfonation of activated carbon aerogel (ACA)
at different sulfonation temperatures (30, 60, 90, 120, and 150 °C).
g activated carbon aerogel was dispersed into 100 ml H SO solu-
tion (10 M). After stirring the mixture at different temperature for
0 h under nitrogen stream, the solid was filtered and washed with
DI water at 70 °C. The residual solid was dried at 110 °C for 5 h to ob-
tain activated carbon aerogel bearing sulfonic acid group (ACA-SO
X), X=30, 60, 90, 120, and 150 in Celsius).
wt.% palladium catalyst was supported on ACA-SO
cipient wetness impregnation method. Palladium nitrate (Pd(NO
Sigma-Aldrich) was dissolved in DI water, and it was then introduced
into the pores of ACA-SO H (X). The supported palladium catalysts
3
H
3
3.1. Characterization of Pd/ACA-SO H (X)
(
Fig. 1 shows the N
and Pd/ACA-SO H (X) catalysts. Both Pd/ACA and Pd/ACA-SO
(X=30, 60, 90, 120, and 150) catalysts showed type-IV isotherm
with type-H2 hysteresis loop. This indicates that Pd/ACA-SO H (X)
catalysts still retained a porous structure even after the sulfonation
of activated carbon aerogel with H SO . Surface area of Pd/ACA-
2
adsorption–desorption isotherms of Pd/ACA
1
2
4
3
3
H (X)
1
3
3
H
2
4
2
2
(
3
SO H (X) increased (711 m /g→779 m /g) with increasing sulfona-
5
3
H (X) by an in-
tion temperature (30 °C→150 °C) as listed in Table 1.
3
2
) ,
3
Successful impregnation of palladium metal on ACA-SO H (X)
(X=30, 60, 90, 120, and 150) was confirmed by XRD analysis, as
shown in Fig. 2. Pd/ACA-SO H (X) exhibited characteristic XRD
3
3
were dried at 80 °C for 3 h, and calcined at 250 °C for 5 h. The supported
peaks at 39.8°, 46.3°, and 68.1°. This result indicates that metallic pal-
ladium was well formed after the reduction process. Average palladi-
um particle size of Pd/ACA-SO H (X) catalysts calculated by the
3
3
catalysts were reduced with a mixed stream of hydrogen (5 cm /min)
3
and nitrogen (30 cm /min) at 120 °C for 10 h to obtain Pd/ACA-SO
3
H
(
X). For comparison, palladium catalyst supported on ACA was also pre-
Debye–Scherrer equation was in the range of 10.4–11.2 nm with no
pared by an incipient wetness impregnation method (Pd/ACA).
great difference, as listed in Table 1. ICP-AES analysis (Shimadz, ICP-
1
000 IV) revealed that phosphoric acid did not remain in the final cat-
2
.2. Characterization
alyst (Pd/ACA-SO H (X)), because phosphoric acid used as a chemical
3
activation agent was removed during the activation and washing
steps.
3
Surface area of Pd/ACA-SO H (X) was determined by nitrogen
adsorption-desorption isotherm (ASAP 2010, Micromeritics). Crystal-
line state and palladium dispersion of Pd/ACA-SO H (X) were deter-
mined by XRD (D-MA2500-PC, Rigaku) measurements using Cu-Kα
radiation. Average palladium particle size of Pd/ACA-SO H (X) was
calculated using the Debye–Scherrer equation. NH -TPD experiment
was conducted to determine the acid property of Pd/ACA-SO H (X)
BEL Japan, BELCAT-B). Sulfur content on the catalysts was deter-
mined using CHNS analysis (US/CHNS-932, LECO). FT-IR analysis (Ni-
colet, Nicolet 6700) of Pd/ACA-SO H (X) and Pd/ACA was performed
to check the form of S-containing species in the catalysts.
Sulfur content of Pd/ACA-SO
was in the range of 0.63–0.94 wt.% as listed in Table 1. Among the cat-
alysts tested, Pd/ACA-SO H (90) showed the highest sulfur content
(0.94 wt.%). In order to investigate the acid property of Pd/ACA-
3
H (X) determined by CHNS analysis
3
3
3
3
3
(
Pd/ACA-SO H (150)
3
3
Pd/ACA-SO H (120)
3
Pd/ACA-SO H (90)
3
2
.3. Decomposition of 4-phenoxyphenol
Pd/ACA-SO H (60)
3
6 5 6 4
Decomposition of 4-phenoxyphenol (C H OC H OH, Sigma-
Aldrich) over Pd/ACA-SO H (X) and Pd/ACA was carried out in an auto-
3
Pd/ACA-SO H (30)
3
clave reactor under hydrogen atmosphere. 9 ml hexadecane (Sigma-
Aldrich) (a solvent) and 0.01 g catalyst were charged into the reactor.
Pd/ACA
0
.2 g 4-phenoxyphenol was then added into the reactor. The catalytic
reaction was performed at 200 °C and 10 atm (H ) for 1 h with agitation
2
0
0.2
0.4
0.6
0.8
1.0
speed of 100 rpm. Reaction products were analyzed with a gas chro-
matograph (Younglin, ACME 6100) equipped with DB-5 column and
flame ionization detector. Conversion of 4-phenoxyphenol and selectiv-
ity for product (cyclohexanol, benzene, and phenol) were calculated
Relative pressure (P/P0)
Fig. 1. N
2
adsorption–desorption isotherms of Pd/ACA and Pd/ACA-SO
60, 90, 120, and 150) catalysts.
3
H (X) (X=30,

H.W. Park et al. / Catalysis Communications 20 (2012) 89–93
91
Table 1
Surface area, acidity, average palladium particle size, sulfur content, and catalytic performance of Pd/ACA-SO
3
H (X) and Pd/ACA in the decomposition of 4-phenoxyphenol.
Catalyst
X in Pd/ACA-SO
X=30
3
H (X)
X=60
Pd/ACA
X=90
X=120
X=150
2
a
S
BET (m /g)
711
71
729
73
10.4
0.78
69.0
82.4
31.8
41.7
8.9
56.9
22.0
28.8
6.1
743
79
769
69
779
61
824
34
11.5
–
Acidity (μmol NH
3
/g)b
Particle size of Pd
c
10.9
0.67
68.3
83.6
32.1
44.5
7.0
57.1
21.9
30.4
4.8
10.7
0.94
71.9
84.9
35.4
39.5
10.0
61.0
25.4
28.4
7.2
11.2
0.71
68.8
81.6
34.6
36.8
10.2
56.1
23.8
25.3
7.0
11.1
0.63
67.1
82.3
32.5
39.4
10.4
55.2
21.8
26.4
7.0
d
Sulfur content (wt.%)
Conversion (%)e
62.4
80.0
38.7
30.1
11.2
49.9
24.1
18.8
7.0
e
Total selectivity for main products (%)
Cyclohexanol (%)
Benzene (%)
Phenol (%)
Total yield for main products (%)
Cyclohexanol (%)
Benzene (%)
Phenol (%)
e
a
Calculated by N
Calculated by peak area of NH -TPD profiles.
Calculated by the Debye–Scherrer equation.
Determined by CHNS analysis.
Calculated according to the Eqs. (1)–(3).
2
adsorption–desorption isotherm.
b
c
3
d
e
SO
SO
3
H (X), NH
3
-TPD experiment was carried out. Acidity of Pd/ACA-
that characteristics of carbon aerogel were well maintained even after
the activation using H PO and the sulfonation using H SO
3
H (X) determined from TPD peak area is listed in Table 1 (NH
3
-
3
4
2
4
.
TPD profiles are not shown here). It is interesting to note that acidity
of Pd/ACA-SO H (X) showed a volcano-shaped trend with respect to
sulfonation temperature (X). Among the catalysts tested, Pd/ACA-
SO H (90) showed the largest acidity (79 μmol NH /g).
Fig. 3 shows the correlation between and S content and acidity of Pd/
ACA-SO H (X) catalysts. The correlation shows that acidity of Pd/ACA-
SO H (X) was closely related to S content of Pd/ACA-SO H (X). Acidity
of Pd/ACA-SO H (X) increased with increasing S contents of Pd/ACA-
SO H (X). Among the catalysts, Pd/ACA-SO H (90) with the largest S
content (0.94 wt.%) showed the largest acidity (79 μmol NH /g).
The form of S-containing species of Pd/ACA-SO H (X) (X=30, 60,
0, 120, and 150) was confirmed by FT-IR analysis. FT-IR spectra of
Pd/ACA-SO H (X) and Pd/ACA catalysts are shown in Fig. 4. The forma-
tion of \SO
identified by IR bands appearing at 3400–3800 cm
3
3.2. Catalytic performance of Pd/ACA-SO
4-phenoxypheonol
3
H (X) in the decomposition of
3
3
3
4-Phenoxyphenol was chosen as a lignin model compound for
representing 4-O-5 bond in lignin [9,10]. Fig. 5 shows the scheme for
the decomposition of 4-phenoxyphenol to aromatics over Pd/ACA-
SO H (X) catalysts. Phenol is produced by the cleavage of C\O bond
3
in 4-phenoxyphenol. Phenol is then converted to cyclohexanone,
and it is further converted to benzene and cyclohexanol. As a result
of decomposition of 4-phenoxyphenol over Pd/ACA-SO
matic compounds such as phenol, benzene, and cyclohexanol were
mainly produced. Small amounts of light hydrocarbons (C \C ) and
alcohols were produced as by-products in the decomposition of 4-
phenoxyphenol.
3
3
3
3
3
3
3
9
3
H (X), aro-
3
3
H group and \SH group on Pd/ACA-SO
3
1
H (X) could be
and 700 cm
2
6
−
−1
,
respectively [21–23]. This result indicates that two types of S-
containing species (\SO H and \SH) were formed after sulfonation
of activated carbon aerogel [24,25]. IR bands at 1479, 2942, and
3
3
Metallic palladium should be supported on ACA and ACA-SO H (X) to
show the catalytic activity in the decomposition of 4-phenoxyphenol to
aromatics, because adsorption and activation steps of C\O bond on pal-
ladium surface played important roles in determining the catalytic
−
1
2
874 cm
IR bands at 1222 and 1092 cm
stretching vibration between resorcinol molecules. The bands at
were associated with CH
2
scissor vibration and stretching.
−
1
were associated with CH \O\CH
2
2
−
1
−1
1
614 cm
and 3100 cm
were assigned to aromatic stretching vi-
bration and OH stretching vibration [26,27]. These results also indicate
80
Pd/ACA-SO H (90)
3
7
5
0
Pd/ACA-SO H (150)
3
Pd/ACA-SO H (30)
3
Pd/ACA-SO H (60)
3
7
Pd/ACA-SO H (120)
3
Pd/ACA-SO H (120)
3
Pd/ACA-SO H (90)
65
3
Pd/ACA-SO H (60)
3
6
0
5
Pd/ACA-SO H (150)
3
Pd/ACA-SO H (30)
3
5
0
.6
0.7
0.8
0.9
1.0
1
0
20
30
40
50
60
70
80
S content of Pd/ACA-SO H (X) (wt%)
2
Theta (Degree)
3
Fig. 2. XRD patterns of Pd/ACA-SO
3
H (X) (X=30, 60, 90, 120, and 150) catalysts.
Fig. 3. A correlation between S content and acidity of Pd/ACA-SO
3
H (X) catalysts.

92
H.W. Park et al. / Catalysis Communications 20 (2012) 89–93
a
7
5
(
(
f)
SO H
3
e)
SH
(
(
d)
c)
Pd/ACA-SO H (90)
3
7
0
Pd/ACA-SO H (120)
3
(
(
b)
a)
Pd/ACA-SO H (60)
3
Pd/ACA-SO H (30)
3
4
000
3500
3000
2500
2000
1500
1000
Pd/ACA-SO H (150)
3
-
1
Wavenumber (cm )
65
65
6
0
65
70
75
80
85
Fig. 4. FT-IR spectra of (a) Pd/ACA-SO
3
H (30), (b) Pd/ACA-SO
3 3
H (60), (c) Pd/ACA-SO H
Acidity of Pd/ACA-SO H (X) ( mol NH /g)
3
3
(
90), (d) Pd/ACA-SO H (120), (e) Pd/ACA-SO
3
3
H (150), and (f) Pd/ACA.
b
activity [28,29]. Therefore, ACA and ACA-SO
alytic activity in the decomposition of 4-phenoxyphenol to aromatics.
Catalytic performance of Pd/ACA-SO H (X) in the decomposition
of 4-phenoxyphenol performed at 200 °C and 10 atm for 1 h is listed
in Table 1. Conversion of 4-phenoxyphenol over Pd/ACA-SO H (X)
X=30, 60, 90, 120, and 150) was in the range of 67.1–71.9%. Total
3
H (X) did not show the cat-
3
Pd/ACA-SO H (90)
3
3
(
selectivity for main products and total yield for main products
were in the range of 81.6–84.9% and 55.2–61.0%, respectively. Yield
for benzene (25.3–30.4%) was higher than that for cyclohexanol
6
5
0
5
Pd/ACA-SO H (30)
3
(
21.8–25.4%) and phenol (4.8–7.2%). These results indicate that Pd/
ACA-SO H (X) catalysts served as an efficient catalyst in the decom-
position of 4-phenoxyphenol to aromatics.
Pd/ACA-SO H (120)
3
3
Pd/ACA-SO H (60)
3
Pd/ACA-SO H (150)
3
3
.3. Correlation between catalytic performance and acidity of
Pd/ACA-SO H (X)
3
6
0
65
70
75
80
85
Acidity of Pd/ACA-SO H (X) ( mol NH /g)
Fig. 6(a) shows the correlation between conversion of 4-
phenoxyphenol over Pd/ACA-SO H (X) and acidity of Pd/ACA-SO
X) (X=30, 60, 90, 120, and 150) catalysts. The correlation shows
that conversion of 4-phenoxyphenol over Pd/ACA-SO H (X) was
closely related to the acidity of Pd/ACA-SO H (X). Conversion of 4-
phenoxyphenol increased with increasing acidity of Pd/ACA-SO
X). Among the catalysts tested, Pd/ACA-SO H (90) with the largest
acidity showed the highest conversion of 4-phenoxyphenol.
Fig. 6(b) shows the correlation between total yield for main prod-
ucts over Pd/ACA-SO H (X) and acidity of Pd/ACA-SO H (X) (X=30,
0, 90, 120, and 150) catalysts. The correlation shows that total
yield for main products over Pd/ACA-SO H (X) was also closely relat-
ed to the acidity of Pd/ACA-SO H (X). Total yield for main products
increased with increasing acidity of Pd/ACA-SO H (X). Among the
catalysts tested, Pd/ACA-SO H (90) with the largest acidity showed
the highest total yield for main products. Thus, acidity of Pd/ACA-
SO H (X) played an important role in determining the catalytic per-
3
3
3
3
H
3
Fig. 6. Correlations (a) between conversion of 4-phenoxyphenol over Pd/ACA-SO H
(
(
X) and acidity of Pd/ACA-SO
3
H (X), and (b) between total yield for main products
3
and acidity of Pd/ACA-SO
3 3
H (X). Acidity of Pd/ACA-SO H (X) catalysts was taken
3
from Table 1. Reaction condition: temperature=200 °C, pressure=10 atm (H
2
),
time=1 h.
3
H
(
3
100
Conversion of 4-phenoxyphenol
Total selectivity for main products
3
3
Total yield for main products
6
84.9
8
0.0
3
80
60
71.9
3
3
6
2.4
61.0
3
49.9
3
4
2
0
0
0
formance in the decomposition of 4-phenoxyphenol.
O
H2
2H2
H2
H2
2
HO
HO
OH
HO
Pd/ACA
Pd/ACA-SO H (90)
3
Catalyst
+
H O
2
Fig. 7. Comparison of catalytic performance between Pd/ACA and Pd/ACA-SO
the decomposition of 4-phenoxyphenol. Reaction condition: temperature=200 °C,
pressure=10 atm (H ), time=1 h.
3
H (90) in
Fig. 5. Scheme for cleavage of 4-O-5 bond in 4-phenoxyphenol.
2

H.W. Park et al. / Catalysis Communications 20 (2012) 89–93
93
3
.4. Comparison of catalytic performance of Pd/ACA-SO
3
H (90) and
3
was also observed that Pd/ACA-SO H (X) showed a better catalytic
Pd/ACA
performance than Pd/ACA. It is concluded that acidity of Pd/ACA-
SO H (X) catalysts played an important role in the decomposition of
3
For comparison, palladium catalyst supported on activated carbon
aerogel (Pd/ACA) was prepared by an incipient wetness impregnation
4-phenoxyphenol to aromatics, and Pd/ACA-SO
ble and reproducible catalyst in the reaction.
3
H (X) served as a sta-
3
method. Palladium particle size of Pd/ACA-SO H (90) (10.7 nm) and
Pd/ACA (11.5 nm) was almost same as listed in Table 1. Surface area
Acknowledgments
2
of Pd/ACA (824 m /g) was higher than that of Pd/ACA-SO
3
H (90)
/g) was much
/g).
Fig. 7 shows the catalytic performance of Pd/ACA and Pd/ACA-
H (90) in the decomposition of 4-phenoxyphenol. Conversion of
-phenoxyphenol (71.9%) and total yield for main products (61.0%)
over Pd/ACA-SO H (90) were much higher than those over Pd/ACA
62.4% and 49.9%, respectively), because acidity of Pd/ACA-SO
90) (79 μmol NH /g) was much larger than that of Pd/ACA
34 μmol NH /g). It should be noted that Pd/ACA-SO H (X) catalysts
better catalytic performance than Pd/ACA catalyst
Table 1). That further approved acidity of Pd/ACA-SO H (X) catalysts
2
(
743 m /g), while acidity of Pd/ACA (34 μmol NH
3
This work was supported by the National Research Foundation of
Korea Grant funded by the Korean Government (MEST) (NRF-2009-
C1AAA001-0093292).
smaller than that of Pd/ACA-SO H (90) (79 μmol NH
3
3
SO
3
4
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To investigate the stability and reproducibility of the catalyst, re-
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Activated carbon aerogel bearing sulfonic acid group (\SO H)
1.
was prepared by sulfonation of activated carbon aerogel at different
sulfonation temperature (ACA-SO H (X), X=30, 60, 90, 120, and
50 in Celsius). Palladium catalysts supported on activated carbon
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total yield for main products increased with increasing acidity of
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with the largest acidity showed the highest conversion of 4-
phenoxyphenol (71.9%) and total yield for main products (61.0%). It
4