Hydrogenations over Noble Metal Nanoparticles

The Pd nanoparticles were spherical and crystalline with a narrow size distribution of 3.2 0.7 nm as determined by transmission electron microscopy (TEM). 

The viscous brownish-gray polymers were coated as a thin film of 0.25 pm onto 

For each compound, datasets were obtained from temperature and flow (contact time) dependent conversion measurements, which were then incorporated into kinetic models based on a Langmuir-Hinshelwood mechanism to determine the reaction rate constants k and activation parameters (Gibbs activation energy AG, activation enthalpy AH, and activation entropy AS ). 

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Very fine and stable noble metal nanoparticles (lr(0) and Ru(0), 2.0-2.5 nm in diameter) can, of course, also be synthesized in ILs by chemical reduction [20]. Metal nanoparticles are extraordinarily stable in ILs as a solvent/stabihzer-system, as indicated by the really extraordinarily high turn over numbers in catalytic hydrogenation. 

Several transition metals such as V, Nb, Ta, and Pd can form stable bulk hydrides, so-called interstitial hydrides the bonding in the hydride phase is not ionic but mostly metallic in character, and the hydrogen to metal ratio is not necessarily stoichiometric. Especially, nanoparticles of noble metals such as Pd are relatively easy to prepare by various methods, such as vapor phase deposition on substrates, reductions of salts in solution (electrochemically or electroless), and the inverse micelle templated growth. They are not easily oxidized, and, in recent years, several methods have been developed to precisely control the size of the particles or clusters. Furthermore, growth in solution in the presence of surfactants and stabilizers allows control over the shape of the final particles [35, 36, 42]. 

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