Characterization of a Polymer-Bound Palladium Acetate Catalyst and Studies on the Selective Hydrogenation of Dienes and Alkynes
01 Aug 1993-Journal of Macromolecular Science, Part A (Taylor & Francis Group)-Vol. 30, Iss: 8, pp 557-569
Abstract: Palladium(II) acetate has been anchored onto a copolymer support containing pyridyl and carboxyl groups. XPS studies showed the Pd 3d binding energies for the recovered catalyst to be less by 1 eV after being used in hydrogenation studies. However, x-ray studies and a chemical test based on KCN treatment failed to reveal any palladium oxide or palladium metal formation in the recovered catalyst. It is presumed that an acetate ligand is lost during hydrogenation, which could be the reason for the lowering of the palladium 3d binding energies in the recovered catalyst. Results of investigations of the hydrogenation of olefins and selectivity of the catalyst toward the hydrogenation of dienes and alkynes are presented. The loss of palladium due to leaching under the reaction conditions employed was found to be very low (<1%/cycle).
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Abstract: This paper is a review of the metal complex forming coordination polymers. A polymer–metal complex is composed of synthetic polymer and metal ions bound to the polymer ligand by a coordinate bond. A polymer ligand contains anchoring sites like nitrogen, oxygen or sulphur obtained either by the polymerization of monomer possessing the coordinating site or by a chemical reaction between a polymer and a low molecular weight compound having the coordinating ability. The polymer–metal complexes may be classified into different groups according to the position occupied by the metal, which is decided by the method of preparation. The method include the complexation of polymeric ligand with various metal ions, cross-linked polymers with pendent, ligands forming either intramolecular and/or intermolecular chelating functions are highlighted in the first part. The various works on the coordination complexes has revealed that the heterogeneous systems possess more economical potentials and advantages over homogeneous systems. The co-ordination polymers belong to the former case. The high molecular weight polymer–metal complexes work as storage houses for solar energy. Efficient chemical conversion in the storage of solar energy will be difficult with the homogeneous systems. The synthesis results in an organic polymer with inorganic functions. The metal atoms attached to the polymer backbone are bound to exhibit characteristic catalytic behaviour, which are distinctly different from their low molecular weight analogue. Many synthetic polymer–metal complexes, found to possess high catalytic efficiency, in addition to ion selectivity in waste water treatment, recovery of trace metal ions, and hydrometallurgy are enlightened in the final part.
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TL;DR: It is shown that boiling of the obtained spheres in 28 wt % HNO3 did not affect the shape and bulk structure of the spheres, but led to creation of a considerable amount of surface oxygen-containing functional groups and increase of the content of sp(2) hybridized carbon on the surface.
Abstract: Amorphous, low-porosity carbon spheres on the order of a few micrometers in size were prepared by carbonization of squalane (C30H62) in supercritical CO2 at 823 K. The spheres were characterized and used as catalysts’ supports for Pd. Near-edge X-ray absorption fine structure studies of the spheres revealed sp2 and sp3 hybridized carbon. To activate carbons for interaction with a metal precursor, often oxidative treatment of a support is needed. We showed that boiling of the obtained spheres in 28 wt % HNO3 did not affect the shape and bulk structure of the spheres, but led to creation of a considerable amount of surface oxygen-containing functional groups and increase of the content of sp2 hybridized carbon on the surface. This carbon was seen by scanning transmission electron microscopy in the form of waving graphene flakes. The H/C atomic ratio in the spheres was relatively high (0.4) and did not change with the HNO3 treatment. Palladium was deposited by impregnation with Pd acetate followed by reducti...
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Abstract: In this work thermo-responsive ruthenium catalysts, based on the poly(propylene imine) dendrimers cross-linked with the poly(ethylene glycol) diglycidyl ether, have been prepared for the first time. The materials obtained were characterized by X-ray photoelectron spectroscopy and transmission electron microscopy, and tested in the phenol and benzene hydrogenation. Conditions for the metal impregnation into the polymeric matrix were demonstrated to have a great influence both on physical chemical properties of the synthesized catalysts (metal loading, mean particles size, surface structure etc.), and, as a consequence, on their hydrogenation activity and thermo-responsive properties.
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