NANO EXPRESS Open Access
Fabrication of a form- and size-variable
nanocomposite using supercritical foaming and
impregnation for catalytic hydrogenation
Weisheng Liao1, Ben-Zen Wu1, Hungchi Nian1, Hsiang-Yu Chen2, Jya-Jyun Yu3and KongHwa Chiu1*
This article presents the fabrication of size-controllable and shape-flexible microcellular high-density polyethylene-
stabilized palladium nanoparticles (Pd/m-HDPE) using supercritical foaming, followed by supercritical impregnation.
These nanomaterials are investigated for use as heterogeneous hydrogenation catalysts of biphenyls in supercritical
carbon dioxide with no significant surface and inner mass transfer resistance. The morphology of the Pd/m-HDPE is
examined using scanning electron microscopy images of the pores inside Pd/m-HDPE catalysts and transmission
electron microscopy images of the Pd particles confined in an HDPE structure. This nanocomposite simplifies
industrial design and operation. These Pd/m-HDPE catalysts can be recycled easily and reused without complex
recovery and cleaning procedures.
Keywords: Nanoparticle, Heterogeneous catalysis, Supercritical fluids, Foaming, Impregnation
Nanotechnology has resulted in research that examines
a scale of matter typically between 1 and 100 nm
wherein properties are dependent on the size and form.
The greater surface area per mass compared with larger
particles with identical chemical composition makes
nanomaterials an excellent catalyst and also makes them
more biologically active. When examining possible ex-
posure routes for manufactured nanoparticles or during
their production and inhalation, oral and dermal expos-
ure are the most obvious, depending on the type of
product in which nanoparticles are used. Hence, the de-
velopment of green methods for the fabrication of nano-
materials has become increasingly relevant as chemists
look to shape a more sustainable future.
Heterogeneous catalytic hydrogenation in supercritical
fluids, especially in supercritical carbon dioxide (sc-
CO2), has recently become an active research area be-
cause of its advantages over conventional organic-
solvent-based systems. Sc-CO2has proven to be an ef-
fective solvent for a wide range of homogeneous transi-
tion-metal-catalyzed reactions. The readily achievable
critical point of sc-CO2(Tc=31.1 °C, Pc=73.7 bar) is
one of its many advantages, which also include its low
cost, low toxicity, no flammability, and the ability to
tune the reactive properties by small variations, i.e., vari-
ation in temperature or pressure in the sc-CO2density
. Their advantages also include enhanced mass and
heat transfer, adjustable salvation ability, total H2misci-
bility, elimination of the gas/liquid interface, extended
catalyst lifetime, ease of separation from products, and
minimal organic solvent waste [2-4]. Transition metals
(e.g., Pd, Rh, Ru, and Pt) supported on various matrices
(e.g., activated carbon, Al2O3, SiO2, SBA-15, and MCM-
48) have been prepared and applied for catalytic hydro-
genation of various reactants in supercritical fluids.
Previous research showed that nanosized palladium
particles (diameter=2 to 10 nm) could be deposited uni-
formly in the interior of high-density polyethylene
(HDPE) beads (diameter=3 to 4 mm) using supercritical
impregnation and catalyzed hydrogenation of numerous
aromatic compounds in sc-CO2, including benzene and
* Correspondence: firstname.lastname@example.org
1Department of Chemistry, National DongHwa University, Shoufeng, Hualien
Full list of author information is available at the end of the article
© 2012 Liao et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction
in any medium, provided the original work is properly cited.
Liao et al. Nanoscale Research Letters 2012, 7:283
Chung-Li Tao-Yuan32023, Taiwan.3Department of Environmental
Engineering and Science, Feng Chia University, Taichung 40724, Taiwan.
WS carried out the nanocomposite preparation and characterization,
designed the concept and experiment, analyzed the results and drafted,
revised and finalized the manuscript. BZ participated in the reusability of Pd/
m-HDPE catalysts and in the experiment data analysis. HY and JJ contributed
to the preparation and discussion of the experimental data analysis and
preparation of the figures. KH integrated the research, revised, and finalized
the manuscript. All authors read and approved the final manuscript.
Received: 8 March 2012 Accepted: 31 May 2012
Published: 31 May 2012
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Cite this article as: Liao et al.: Fabrication of a form- and size-variable
microcellular-polymer-stabilized metal nanocomposite using
supercritical foaming and impregnation for catalytic hydrogenation.
Nanoscale Research Letters 2012 7:283.
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