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Platinum powders, hydrogen

Analogous studies of the chemisorption of 14C-labeled benzene on copper powder and on platinum powder showed no chemisorption on the former, and the establishment of a low surface coverage over a range of temperature on the latter (Fig. 1). Again the surface coverage of hydrogen on platinum appeared to be about three times that achieved by benzene. [Pg.126]

Inelastic neutron TOF spectra have also been obtained for hydrogen adsorbed on platinum powders (31,32). Both experiments observed a sharp surface vibratory mode of the hydrogen near 400... [Pg.267]

We obtained initial rates for the reaction of neopentane on supported platinum and platinum powder catalysts at 300°, 1 atm total pressure, and a hydrogen-to-neopentane ratio equal to 10. As before, surface platinum atoms were titrated by selective chemisorption of hydrogen (27). Before discussing the results, it is important to stress the reproducibility of the results on samples of different origin but nearly identical dispersion and pretreatment. Thus, the same value of the selectivity to isomerization was found on two catalysts an experimental catalyst containing 2% platinum on t -alumina and a commercial sample with 0.6% platinum on y-alumina. Percentage dispersion of the metal was 64 and 73, respectively, and the selectivity was 1.5. Both samples were reduced at 500° under identical standard conditions. [Pg.162]

C.M. Sayers C.J. Wright (1984). J. Chem. Soc. Faraday Trans. I, 80,1217-1220. Hydrogen adsorbed on nickel, palladium and platinum powders. [Pg.359]

Previously, the common approach to fabricating membrane and electrode assemblies for proton exchange membrane fuel cells involves hot-pressing a mixture of platinum powder and polytetrafluoroethylene (PTFE) on both sides of a proton exchange membrane. This method has resulted in hydrogen-oxygen fuel cells capable of high power densities. [Pg.144]

From any point of view the most important, and, if I may use the expression, the most brilliant discovery of last year is, without doubt, thatfine platinum powder has the ability to unite oxygen and hydrogen even at low temperatures. [Pg.518]

Zirconium powder reacts exothermically with many other elements, including hydrogen, boron, carbon, nitrogen, and the halogens, although the ignition temperature is usually above 200°C. The reaction between zirconium powder and platinum is especially violent. [Pg.432]

Carbon and Hydrogen.—Carbon compounds are frequently inflammable, and when heated on platinum foil take fipe or char and burn away. A safer test is to heat the substance with some easily reducible metallic oxide, the oxygen of which forms carbon diovide with the carbon present. Take a piece of soft glass tube about 13 cm. (5 in.) long, and fuse it together at one end. Heat a gram or two of fine copper oxide in a porcelain crucible for a few minutes to drive off the moisture, and let it cool in a desiccator. Mix it with about one-tenth of its bulk of powdered sugar in a mortar. Pour the mixture into the tube, the open end of which is now drawn out into a wide capillary and oeni. at the same time into the form Fig. i. [Pg.1]

Palladium proved especially useful in the hydrogenation of 2-hydroxy-3-nitropropanoic acid. Reduction over palladium-on-carbon gave pure, powdery isoserine, whereas platinum failed to reduce the nitro function under neutral or acidic conditions reduction over Raney nickel gave a bright green powder (96). [Pg.105]

Platinum and palladium are the most common catalysts for alkene hydrogenations. Palladium is normally used as a very fine powder supported" on an inert material such as charcoal (Pd/C) to maximize surface area. Platinum is normally used as PtC, a reagent called Adams catalyst after its discoverer, Roger Adams. [Pg.230]

The brown oxide is a heavy granular powder which settles to the bottom of the solution in the bottle in which the reduction is carried out (p. 10). It must be reduced to platinum black before it becomes a catalyst for the reduction. When the hydrogen is admitted and the bottle shaken the brown oxide becomes black and whips up into a fine suspension. The time necessary for the change of the oxide to platinum black is called the lag. The time of lag varies usually from several seconds to two or three minutes, depending upon the conditions under which... [Pg.95]

The photo-Kolbe reaction is the decarboxylation of carboxylic acids at tow voltage under irradiation at semiconductor anodes (TiO ), that are partially doped with metals, e.g. platinum [343, 344]. On semiconductor powders the dominant product is a hydrocarbon by substitution of the carboxylate group for hydrogen (Eq. 41), whereas on an n-TiOj single crystal in the oxidation of acetic acid the formation of ethane besides methane could be observed [345, 346]. Dependent on the kind of semiconductor, the adsorbed metal, and the pH of the solution the extent of alkyl coupling versus reduction to the hydrocarbon can be controlled to some extent [346]. The intermediacy of alkyl radicals has been demonstrated by ESR-spectroscopy [347], that of the alkyl anion by deuterium incorporation [344]. With vicinal diacids the mono- or bisdecarboxylation can be controlled by the light flux [348]. Adipic acid yielded butane [349] with levulinic acid the products of decarboxylation, methyl ethyl-... [Pg.140]

Similar size effects have been observed in some other electrochemical systems, but by far not in all of them. At platinized platinum, the rate of hydrogen ionization and evolution is approximately an order of magnitude lower than at smooth platinum. Yet in the literature, examples can be found where such a size effect is absent or where it is in the opposite direction. In cathodic oxygen reduction at platinum and at silver, there is little difference in the reaction rates between smooth and disperse electrodes. In methanol oxidation at nickel electrodes in alkaline solution, the reaction rate increases markedly with increasing degree of dispersion of the nickel powders. Such size effects have been reported in many papers and were the subject of reviews (Kinoshita, 1982 Mukerjee, 1990). [Pg.538]

The catalysts most frequently used are based on noble metals (mainly palladium and platinum) on various supports, or on nickel catalysts (mainly Raney type). Hydrogenations are generally performed in the liquid phase, under relatively mild conditions of temperature and pressure (1—40 bar). Most processes are performed batch-wise using powder catalysts in stirred tank or loop-type reactors with sizes up to 10 m . [Pg.30]

Alloys of zinc with iridium, platinum or rhodium, after extraction with acid, leave residues which explode on warming in air, owing to the presence of occluded hydrogen (or oxygen) in the catalytic metal powders so produced. [Pg.1921]

The structure of the metal particles dispersed on a silica powder support ( Aerosil 380, 70 A average silica particle diameter) has been studied by Avery and Sanders (47) using electron microscopy in both bright and dark field, to determine the extent to which the metal particles were multiply twinned or of ideal structure. Platinum, palladium, and gold were examined. These catalysts were prepared by impregnation using an aqueous solution of metal halide derivatives, were dried at 100°-150°C, and were hydrogen... [Pg.11]

The activity of metals other than platinum for skeletal reactions of larger molecules is not well documented, particularly in a mechanistic sense. Carter, Cusumano, and Sinfelt (157) have recently studied the reaction of n-heptane on a series of group VIII metals in the form of hydrogen-reduced (300°C) metal powders. The nature of the reaction pathways is summarized in Table IX. Although many metals have been... [Pg.60]


See other pages where Platinum powders, hydrogen is mentioned: [Pg.164]    [Pg.47]    [Pg.208]    [Pg.211]    [Pg.45]    [Pg.614]    [Pg.235]    [Pg.690]    [Pg.266]    [Pg.267]    [Pg.41]    [Pg.608]    [Pg.83]    [Pg.215]    [Pg.128]    [Pg.421]    [Pg.104]    [Pg.149]    [Pg.240]    [Pg.80]    [Pg.97]    [Pg.407]    [Pg.438]    [Pg.135]    [Pg.208]    [Pg.337]    [Pg.53]    [Pg.53]    [Pg.111]    [Pg.1636]    [Pg.1674]    [Pg.144]    [Pg.220]    [Pg.495]   
See also in sourсe #XX -- [ Pg.267 ]




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Hydrogen platinum

Platinum hydrogenation

Platinum powder

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