Fabrication of a form- and size-variable microcellular-polymer-stabilized metal nanocomposite using supercritical foaming and impregnation for catalytic hydrogenation.

Department of Chemistry, National DongHwa University, Shoufeng, Hualien, 97401, Taiwan. .
Nanoscale Research Letters (Impact Factor: 2.48). 05/2012; 7(1):283. DOI: 10.1186/1556-276X-7-283
Source: PubMed

ABSTRACT 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.

  • [Show abstract] [Hide abstract]
    ABSTRACT: A series of supported palladium catalysts were evaluated for their ability to mediate the complete hydrogenation of polycyclic aromatic hydrocarbon (PAH) compounds. Benzo[a]pyrene (B[a]P) or phenanthrene (Phe) in hexane was merged with a hydrogen-carbon dioxide [5% (w/w) H(2)/CO(2)] stream and transferred to a flow through mini-reactor (capacity ca. 1 g) that was maintained at 90 degrees C under a back-pressure of 20.68 MPa. Effluent from the reactor trapped in hexane was monitored/quantified by gas chromatography-mass spectrometry. Catalyst formulations supported on iron powder, high density polyethylene (HDPE) or gamma-alumina were prepared and compared in terms of hydrogenation activity as measured by the quantity of substrate per unit time that could be perhydrogenated to toxicologically innocuous products. Both of the Pd preparations supported on gamma-alumina were more efficient than a commercial Pd(0) (5% w/w) on gamma-Al(2)O(3) formulation or preparations supported on HDPE or the iron powder. Bimetallic mixtures with Pd increased the hydrogenation activity when co-deposited with Cu or Ni but not with Ag or Co. However, increases in hydrogenation activity by increasing the loading of Pd (or bimetallic mixture) on this surface were limited. Despite using supercritical carbon dioxide (scCO(2)) to swell the surfaces of the polymer, the deposition of nanoparticles within the polyethylene formulation was appreciably less active than either the oxidic or the Fe(0) formulations.
    Journal of Environmental Monitoring 01/2008; 9(12):1344-51. · 2.11 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Hydrodechlorination of 4-chlorobiphenyl in supercritical fluid carbon dioxide (SF-CO(2)) catalyzed by palladium nanoparticles stabilized in high-density polyethylene beads proceeds by consecutive reactions to the final product bicyclohexyl. Each step of the reaction sequence, that is, 4-chlorobiphenyl --> biphenyl --> cyclohexylbenzene --> bicyclohexyl, follows pseudo-first-order kinetics. Arrhenius parameters of each reaction step were determined separately in SF-CO(2) by in situ absorption spectroscopy using a high-pressure fiber-optic cell. A simulation of product distributions using the first-order consecutive reaction equations was performed and compared with the experimental results obtained by GC/MS analysis of the 4-chlorobiphenyl reaction system. The differences are explained in terms of adsorption/desorption behavior of the intermediates on the catalytic metal surface with respect to the stereostructures of the molecules generated by a molecular mechanics method.
    The Journal of Physical Chemistry A 08/2009; 113(36):9772-8. · 2.77 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Swelled plastics in supercritical carbon dioxide provide unique environments for stabilizing palladium and rhodium nanoparticles and for catalytic hydrogenation. Complete hydrogenation of benzene to cyclohexane can be achieved in 10 minutes using the plastic stabilized Rh nanoparticles at 50 degrees C in supercritical CO(2). High efficiency, reusability, and rapid separation of products are some advantages of the plastic stabilized metal nanoparticles for catalytic hydrogenation in supercritical CO(2).
    Chemical Communications 05/2004; · 6.72 Impact Factor


Available from