Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Hydrogen intermediate phase

A few general remarks about a group of metal-hydrogen phases have been included in 3.8.4.1 where interstitial hydrogen solutions in metallic structures have been described. However, as previously observed, a number of intermediate phases are also formed in several systems. A short summary of these is shown in Table 5.2 where their formulae very often have only an indicative character and several structure types correspond to more or less extended solid solution ranges. [Pg.331]

The solid-solid transformation of 2-amino-3-hydroxy-6-phenylazopyridine, 57a, to 57b proceeds through two intermediate phases (119). X-Ray and IR studies of the former, low-temperature, and the latter, high-temperature phase show that they are the phenolazo and quinone hydrazone forms, respectively. This solid-state tautomerism can be accounted for by a cooperative intermolecular shift of protons across the various hydrogen bonds. However, because of the complexity of the hydrogen-bond network, the actual pathway of the proton shift has not been uniquely defined. [Pg.164]

Study of the addition of gas-phase D atoms to 1-alkene monolayers adsorbed on Cu(100) suggested that addition to the terminal carbon predominates to generate the corresponding secondary alkyl group (half-hydrogenated intermediate).353... [Pg.667]

Over the past several years, Gruen and coworkers have examined the SH response from iron electrodes in alkaline solutions [45, 53, 172]. In their work on polycrystalline iron, they concluded that the potential dependent SH response which was observed during surface oxidation could be attributed to two intermediate phases on the electrode surface between the passive film at oxidative potentials and the reduced metal at hydrogen evolution potentials [53]. They have recently extended this work to Fe(110). In this study [172], they examined the SH rotational anisotropy from this crystal under ambient conditions. They found that the experiments reveal the presence of both twofold and threefold symmetric species at the metal/oxide interface. When their data is fit to the theory of Tom et al. [68], they conclude that the measured three-fold symmetric oxide is found to be tilted by 5° from the Fe(110) plane. The two-fold symmetric structure is aligned with the Fe(110) surface. [Pg.197]

Kim et al. (2004) CuO, Cu20 Reduction kinetics, intermediate phases + + + Reductive activation with hydrogen... [Pg.320]

The above discussion indicates that acidic phosphate salts may play an important role in forming CBPCs. To use acid phosphates as the acidic components in acid-base reactions, primary requirement is solubility in water. Table 4.1 lists solubilities of some of the common hydrogen phosphates that are available in the literature and are useful intermediate phases during formation of CBCs. [Pg.48]

For the first decomposition step the formation of [Bi2Hi2] anion as a possible intermediate phase is discussed [35]. Different enthalpy values in the range —40 to 5 7 kj mol H2 for the first decomposition step at about 277 ° C have been determined from experimental data [35, 36[. From density functional theory (DFT) calculations a reaction enthalpy of 38 kj mol H2 at 27 ° C was confirmed [37]. Cycling experiments performed at 350 ° C under 10 MPa hydrogen lead to re-absorption of more than 3 wt.% hydrogen, showing lhat the second decomposition step is reversible [33, 36]. [Pg.124]

Similarly, the magnesium-aluminum system shows several intermediate phases which react with hydrogen, such as Mg2Als [81] and Mgi7Ali2 [82]. [Pg.204]

In some cases, the initial compounds form hydrogen-rich intermediate phases, which release hydrogen at lower temperature than the starting compounds. A number of such new phases were presented both by oral presentations and posters. These presentations were a tnix of pure and applied research. [Pg.328]

In the ISHE it was possible to connect PCX diagrams which characterize the bulk properties of a system, with diffraction studies that help to determine which phases are involved in reactions when more than two components are present in the mixture. The measurement of PCX diagrams tends to go first, as they demonstrate whether the destabilization is achieved. Diffraction study can clarify the mechanism of such destabilization , i.e. the reaction mechanism. In particular, the dehydrogenation process has to be analyzed for new intermediate phases, and for new hydrogen-poor (or hydrogen-free) decomposition products. The latter may be tested as starting compounds in rehydrogenation processes. New compounds may show different properties and maybe even reversibility ... [Pg.329]

The fuel cell is highly efficient at converting hydrogen into electricity, without the use of combustion as an intermediate phase [3], This conversion is accompanied by considerably fewer harmful side effects than in conventional installations, since the fuel cell generates practically no harmful waste products, and no noise nuisance whatsoever. [Pg.12]

The yield of labeled benzene can be enhanced by the presence of the benzene-iodine complex during irradiation. Pozdeev et al. (1962a) ascribe this effect to stabilization of a highly excited intermediate which results in increased probability of hydrogen loss from the intermediate. Phase-effect studies on cyclohexane, cyclohexene, cyclohexadiene and benzene by Pozdeev et al. (1962b) lend further support to the excited-... [Pg.243]


See other pages where Hydrogen intermediate phase is mentioned: [Pg.388]    [Pg.181]    [Pg.327]    [Pg.121]    [Pg.1598]    [Pg.854]    [Pg.10]    [Pg.870]    [Pg.172]    [Pg.194]    [Pg.143]    [Pg.200]    [Pg.328]    [Pg.36]    [Pg.48]    [Pg.273]    [Pg.30]    [Pg.35]    [Pg.249]    [Pg.839]    [Pg.12]    [Pg.116]    [Pg.414]    [Pg.435]    [Pg.438]    [Pg.445]    [Pg.469]    [Pg.470]    [Pg.152]    [Pg.400]    [Pg.1390]    [Pg.559]    [Pg.520]    [Pg.529]    [Pg.176]    [Pg.502]    [Pg.72]    [Pg.177]   
See also in sourсe #XX -- [ Pg.268 ]




SEARCH



Hydrogen intermediate

Hydrogenation intermediates

Intermediate phases

Phase hydrogenation

© 2024 chempedia.info