Complete hydrodechlorination of DDT and its derivatives using a hydroxyapatite-supported Pd nanoparticle catalyst

Article abstract of DOI:10.1246/cl.2010.49

Complete hydrodechlorination of 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane (DDT) and its derivatives 1,1-dichloro-2,2-bis(4-chlorophenyl)ethene (DDE) and 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane (DDD) was achieved using a hydroxyapatite-supported Pd nanoparticle catalyst (Pd⁰HAP) in the presence of molecular hydrogen under mild reaction conditions. The catalytic activity of Pd⁰HAP was significantly higher than those of previously reported Pd catalysts.

Full text of DOI:10.1246/cl.2010.49

doi:10.1246/cl.2010.49
Published on the web December 12, 2009
49
Complete Hydrodechlorination of DDT and Its Derivatives Using
a Hydroxyapatite-supported Pd Nanoparticle Catalyst
1
2
2
1
1
Norifumi Hashimoto, Takayoshi Hara, Shogo Shimazu, Yusuke Takahashi, Takato Mitsudome,
1
1
1,3
Tomoo Mizugaki, Koichiro Jitsukawa, and Kiyotomi Kaneda*
1
Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531
2
Graduate School of Engineering, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522
3
Research Center for Solar Energy Chemistry, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531
(
Received October 27, 2009; CL-090956; E-mail: kaneda@cheng.es.osaka-u.ac.jp)
II
Complete hydrodechlorination of 1,1,1-trichloro-2,2-bis(4-
chlorophenyl)ethane (DDT) and its derivatives 1,1-dichloro-2,2-
bis(4-chlorophenyl)ethene (DDE) and 1,1-dichloro-2,2-bis(4-
chlorophenyl)ethane (DDD) was achieved using a hydroxy-
The HAP-supported Pd(II) complex (Pd HAP) was synthe-
1
2
sized according to a procedure described in a previous paper.
Powdered HAP was stirred in an acetone solution of
PdCl2(PhCN)2 at room temperature for 3 h, and the resulting
slurry was filtered, washed with acetone and dried under
0
apatite-supported Pd nanoparticle catalyst (Pd HAP) in the
II
¹1
presence of molecular hydrogen under mild reaction conditions.
vacuum, affording Pd HAP (2.01 g, Pd content: 0.02 mmol g
)
0
II
The catalytic activity of Pd HAP was significantly higher than
as a pale yellow powder. Characterization of Pd HAP by
elemental analysis, XPS, EDX, and Pd K-edge XAFS showed
that a monomeric PdCl2 species was grafted by chemisorption
onto the HAP surface. Next, the HAP-supported Pd nanoparticle
catalyst Pd HAP was prepared as follows: Pd HAP (0.2 g)
was placed in a stainless steel autoclave with a glass lining
(100 mL) and reduced with H2 (1 atm) in the presence of Cs2CO3
(1.5 mmol) and 2-propanol (6 mL) at 60 °C for 30 min to form a
those of previously reported Pd catalysts.
0
II
Chlorinated organic compounds are manufactured on a
large scale and used in a variety of chemical industries.
However, they have an often fatal impact on the environment
1
and living organisms. The most infamous of these compounds,
0
1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT), was wide-
gray powder. For analysis, the Pd HAP catalyst was separated
ly adopted as a pesticide and insecticide, particularly for the
elimination of mosquitoes in malaria-infested areas of the world,
due to its high effectiveness and low cost. Nowadays, many
countries have prohibited the use of DDT because of its toxicity
and chemical stability, which lead to water pollution and soil
by filtration and characterized by field-emission scanning
electron microscopy (FE-SEM). Figure 1a shows the formation
of Pd nanoparticles with a mean diameter (d) of 4 nm and a
narrow size distribution (standard deviation: · = 0.30 nm,
·/d = 7.5%) on the HAP surface.
2
contamination.
For the hydrodechlorination reaction, DDT (0.2 mmol) was
added and the vessel was repressurized with H2. The results
obtained are shown in Table 1. After 10 h, the completely
dechlorinated product 1,1-diphenylethane (1) was obtained in
Much attention has been given to the disposal of large
quantities of DDT, and many approaches to complete dechlori-
3
4
nation of DDT®including photochemical, electro-chemical,
biochemical, and mechanochemical6 reactions®have been
developed. However, most of these processes require severe
conditions and special equipment. In order to achieve the
disposal of DDT using green and sustainable technology, the
development of an efficient catalytic system for decomposition
of DDT under mild conditions is desirable.
5
quantitative yield. The reaction rate increased with increasing
13
H2 pressure (Entries 1­4); complete dechlorination to 1 was
achieved in 1 h under 10 atm of H2 (Entry 4). When the reaction
was carried out without Cs CO , 1 was obtained in extremely
2
3
0
low yield (Entry 5), and in the absence of the Pd HAP catalyst,
DDT was not converted at all (Entry 6). Various bases were
screened as acceptors of HCl generated in the hydrodechlorina-
tion reaction: the use of Na2CO3, K2CO3, and triethylamine
resulted in low yields of 1 (Entries 7­9). Among the various
solvents examined, 2-propanol was found to be optimal, and
DMF also provided a good yield of 1 (Entries 4 and 10). In
contrast, low yields of 1 were obtained using other solvents such
Catalytic hydrodechlorination using molecular hydrogen is
one of the most promising and greenest methodologies for
decomposition of DDT without the formation of persistent
7
organic pollutants such as dioxins and PCBs. Hydrodechlori-
nation of DDT using Pd catalysts has been studied for many
8
years, however previously reported catalyst systems suffered
from low activity, and complete dechlorination of DDT was not
achieved.
(a)
(b)
We recently developed novel heterogeneous catalysts using
9
hydroxyapatite (HAP), Ca10(PO4)6(OH)2, as a macroligand for
catalytically active species in various environmentally benign
10
organic transformations. In particular, the HAP-bound Pd nano-
0
11a
particle catalyst (Pd HAP) and magnetically functionalized
3
0 nm
30 nm
0
11b
Pd HAP­£-Fe O
acted as efficient heterogeneous catalysts
2
3
for complete hydrodechlorination of aryl chlorides and benzyl
chlorides under atmospheric pressure of molecular hydrogen. In
this paper, we demonstrate complete dechlorination of DDT and
Figure 1. FE-SEM photographs of Pd nanoparticles on
0
Pd HAP (a) after pretreatment with H and (b) after hydro-
2
0
its derivatives catalyzed by Pd HAP using molecular hydrogen.
dechlorination of DDT.
Chem. Lett. 2010, 39, 49­51
© 2010 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/

5
0
Table 1. Dechlorination of DDT under various conditionsa
Cl
Cl
Cl
Cl
Cl
Cl
Pd catalyst (Pd: 4 µmol)
H2, base, solvent,
Cl
Cl
Cl
Cl
DDE
0
Pd HAP
Cl
Cl
60 °C, 1 h
1
0.2 mmol
Cl
1
Cs CO , i-PrOH,
2
3
>99 % yields
H2
Time Conv.
Yield
of 1/%
Entry
Base
Solvent
H2 10 atm, 60 °C, 1 h
b
b
/
atm
/h
/%
1
2
3
4
5
6
7
8
1
4
7
Cs2CO3 i-PrOH
Cs2CO3 i-PrOH
Cs2CO3 i-PrOH
10
5
2
1
1
1
1
1
1
1
1
1
1
1
1
1
>99
>99
>99
>99
99
0
99
>99
>99
>99
16
76
74
31
>99
>99
>99
>99
>99
>99
4
DDD
0
Scheme 2. Pd HAP-catalyzed dechlorination of DDT metabo-
lites using H . Reaction conditions: DDE or DDD (0.25 mmol),
Pd HAP (Pd: 4 ¯mol), Cs CO (1.5 equiv relative to Cl atom),
and i-PrOH (6 mL).
10 Cs2CO3 i-PrOH
10 None i-PrOH
10 Cs2CO3 i-PrOH
10 Na CO3 i-PrOH
10
10
10 Cs2CO3
10 Cs2CO3 MeOH
10 EtOH
10 Cs2CO3 Me-c-Hex
10 Cs CO3 Anisole
2
0
2
3
c
0
54
85
32
72
<1
3
4
2
19
16
2
reaction conditions. The second dechlorination of DDT pro-
ceeded at a similar rate to the fresh reaction, affording a 92%
yield of 1. It was concluded that the Pd HAP-based catalytic
hydrodechlorination system provided a simple and practical
degradative treatment of DDT.
K2CO3
NEt3
i-PrOH
i-PrOH
DMF
d
9
0
10
1
1
0
12
13
14
15
16
2
Cs CO3
FE-SEM analysis of the spent Pd HAP catalyst showed that
e
the average size of the Pd nanoparticles on the HAP surface was
similar to that of the fresh catalyst, and there was no apparent
aggregation (Figure 1b). Inductively coupled plasma (ICP)
analysis confirmed that no palladium had leached into the
2-propanol solution after dechlorination of DDT (<0.1 ppm).
These results reveal that the HAP support was effective in
preventing both leaching and agglomeration of Pd nanoparticles,
probably due to its strong adsorption capacity. This is consistent
with the retention of high catalytic activity in the recycling
experiments.
2
f
10 Cs2CO3 i-PrOH
10 Cs2CO3 i-PrOH
g
a
b
Base (1.5 mmol), solvent (6 mL). Determined by GC using
c
0
d
an internal standard. Without Pd HAP catalyst. NEt3
(
catalyst. 5 wt % Pd/Al2O3 was used as a catalyst.
e
f
3 mmol). Methylcyclohexane. 5 wt % Pd/C was used as a
g
Cl
Cl
Cl
0
The Pd HAP catalyst was further applied to the dechlori-
0
Pd HAP
1
nation of the DDT derivatives 1,1-dichloro-2,2-bis(4-chloro-
phenyl)ethene (DDE) and 1,1-dichloro-2,2-bis(4-chlorophenyl)-
ethane (DDD), which are known metabolites of DDT found
in the environment (Scheme 2). These substrates, containing
aliphatic sp and sp C­Cl bonds, respectively, gave 1
quantitatively in 1 h under the same reaction conditions. In
Cs CO , i-PrOH,
H2 10 atm, 60 °C, 28 h
Cl
isolated yield = 87 %
2
3
(
conv. >99 %)
Cl
TON = 1,087
0
2
3
Scheme 1. Dechlorination of DDT using Pd HAP catalyst.
0
Reaction conditions: DDT (1 mmol), Pd HAP (Pd: 4 ¯mol),
Cs2CO3 (7.5 mmol), and i-PrOH (12 mL).
3
addition, other chlorinated compounds containing sp C­Cl
bonds were successfully dechlorinated using the same catalytic
system; for example, (2-chloroethyl)benzene and 1-(2-chloro-
ethyl)naphthalene were dechlorinated to give ethylbenzene and
1-ethylnaphthalene in quantitative yield, respectively, in 12 h
under the same reaction conditions.
as methanol, ethanol, methylcyclohexane, and anisole (Entries
0
11­14). Notably, the catalytic activity of Pd HAP for complete
dechlorination to 1 was significantly higher than those of
commercially available heterogeneous Pd catalysts (Entries 15
1
4
0
and 16).
In conclusion, the Pd HAP system served as an efficient
0
As highlighted in Scheme 1, the Pd HAP catalyst (Pd:
.08 mol % relative to chlorine) converted 0.35 g (1 mmol) of
heterogeneous catalyst for complete dechlorination of DDT and
its derivatives. The catalytic methodology described here is a
powerful candidate for a green disposal protocol for DDT as it
has the following advantages: (1) a simple work-up procedure,
(2) the use of molecular hydrogen as a clean hydrogen donor, (3)
high catalytic performance with a TON of around 1000, and (4)
reusability.
0
DDT to give 1 in 87% isolated yield (0.16 g) under 10 atm of H2
at 60 °C for 28 h; the turnover number (TON, mol of Cl atoms
removed per mol Pd content) reached 1087. This TON value was
much greater than those of previously reported catalytic systems
for dechlorination of DDT, such as 5 wt % Pd on carbon/KOH
8
a
8b
(
TON = 175), 10 wt % Pd on carbon/NEt3 (TON = 149),
8c
sol­gel entrapped Pd[Rh(cod)Cl] (TON = 90), and 5 wt % Pd
This work was supported by a Grant-in-Aid for Scientific
Research from the Ministry of Education, Culture, Sports,
Science and Technology of Japan. The work was also supported
by Grant-in-Aid for Scientific Research on Priority Areas
(No. 18065016, “Chemistry of Concerto Catalysis”) from
Ministry of Education, Culture, Sports, Science and Technology,
Japan. We thank Mr. Masao Kawashima for support with regard
to FE-SEM analysis.
2
on carbon/NaOH (TON = 53).8d It can be seen that the surface-
supported Pd nanoparticles react efficiently with bulky DDT
15
molecules because of the nonporous structure of HAP.
0
Moreover, the Pd HAP catalyst showed good reusability
without significant loss of activity. Upon complete dechlorina-
tion of DDT, portions of DDT and Cs CO were successively
2
3
added to the resulting mixture and further treated under identical
Chem. Lett. 2010, 39, 49­51
© 2010 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/

5
1
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7
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www.csj.jp/journals/chem-lett/