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Noble Metal Catalysts (noble + metal_catalyst)
Selected AbstractsThe Role of Carbon Dioxide in Chemoselective Hydrogenation of Halonitroaromatics over Supported Noble Metal Catalysts in Supercritical Carbon Dioxide.CHEMINFORM, Issue 27 2005Shinichiro Ichikawa Abstract For Abstract see ChemInform Abstract in Full Text. [source] Silane reduction of onium saltsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2010James V. Crivello Abstract Novel redox initiators for cationic polymerizations were developed consisting of an onium salt together with a SiH functional silane or siloxane. The reduction of the onium salt by the silane is catalyzed by noble metal complexes or certain transition metal compounds and takes place spontaneously at room temperature. The redox reaction of the onium salt with the silane results in the liberation of a strong Brønsted acid that can be subsequently used to initiate cationic polymerizations. Typical onium salts that have been employed in these redox initiator systems are diaryliodonium salts, triarylsulfonium salts and S,S -dialkyl- S -phenacylsulfonium salts. Studies of the effects of variations in the structures of the onium salt, the silane and the type of noble metal catalyst were carried out. In principle, the redox initiator systems are applicable to all types of cationically polymerizable monomers and oligomers, including the ring-opening polymerizations of such heterocyclic monomers as epoxides and oxetanes and, in addition, the polymerization of vinyl monomers such as vinyl ethers, N -vinylcarbazole and styrenic monomers. The use of these novel initiator systems for carrying out commercially attractive crosslinking polymerizations for coatings, composites and encapsulations is discussed. Copyright © 2009 John Wiley & Sons, Ltd. [source] High-Performance Alkaline Polymer Electrolyte for Fuel Cell ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Jing Pan Abstract Although the proton exchange membrane fuel cell (PEMFC) has made great progress in recent decades, its commercialization has been hindered by a number of factors, among which is the total dependence on Pt-based catalysts. Alkaline polymer electrolyte fuel cells (APEFCs) have been increasingly recognized as a solution to overcome the dependence on noble metal catalysts. In principle, APEFCs combine the advantages of and alkaline fuel cell (AFC) and a PEMFC: there is no need for noble metal catalysts and they are free of carbonate precipitates that would break the waterproofing in the AFC cathode. However, the performance of most alkaline polyelectrolytes can still not fulfill the requirement of fuel cell operations. In the present work, detailed information about the synthesis and physicochemical properties of the quaternary ammonia polysulfone (QAPS), a high-performance alkaline polymer electrolyte that has been successfully applied in the authors' previous work to demonstrate an APEFC completely free from noble metal catalysts (S. Lu, J. Pan, A. Huang, L. Zhuang, J. Lu, Proc. Natl. Acad. Sci. USA2008, 105, 20611), is reported. Monitored by NMR analysis, the synthetic process of QAPS is seen to be simple and efficient. The chemical and thermal stability, as well as the mechanical strength of the synthetic QAPS membrane, are outstanding in comparison to commercial anion-exchange membranes. The ionic conductivity of QAPS at room temperature is measured to be on the order of 10,2,S cm,1. Such good mechanical and conducting performances can be attributed to the superior microstructure of the polyelectrolyte, which features interconnected ionic channels in tens of nanometers diameter, as revealed by HRTEM observations. The electrochemical behavior at the Pt/QAPS interface reveals the strong alkaline nature of this polyelectrolyte, and the preliminary fuel cell test verifies the feasibility of QAPS for fuel cell applications. [source] Characterization of the active site structure of Pd and Pd-promoted Mo sulfide catalysts by means of XAFSJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001Takeshi Kubota Recently, noble metal catalysts are noted as promising candidates for new super-deep-hydrodesulfurization (HDS) catalysts. In this study, we investigated the structure of Pd particles supported on zeolite and Al2O3 under a sulfidation or reduction condition. From EXAFS analysis, it was found for sulfided Pd catalysts that small Pd sulfide clusters are formed without sintering. It was also revealed that no extensive growth of metal Pd particles occurs in Pd/NaY sulfide catalysts even after a treatment with H2 at 673 K. The dispersion of Pd metal particles is improved by H2/H2S treatment. These results indicate that in the presence of H2S, Pd shows high resistance against particle growth. A comparison of the Mo and Pd K-edge EXAFS spectra for MoSx/Pd-NaY and Pd-NaY catalysts revealed the existence of Mo-Pd bondings by the addition of Mo sulfide, indicating a direct interaction between Mo and Pd sulfides. [source] | ||||||||||