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Hydrogenation hydrogen-spinel

Figure 8.9 Calculated free energies of trihydroxides (solid lines) and monohydroxides (dashed lines) relative to a-AfOs. The dotted line represents the calculated free energy for a hypothetical hydrogen spinel structure postulated fory-AfOs. Adapted from reference [61],... Figure 8.9 Calculated free energies of trihydroxides (solid lines) and monohydroxides (dashed lines) relative to a-AfOs. The dotted line represents the calculated free energy for a hypothetical hydrogen spinel structure postulated fory-AfOs. Adapted from reference [61],...
The predominant process for manufacture of aniline is the catalytic reduction of nitroben2ene [98-95-3] ixh. hydrogen. The reduction is carried out in the vapor phase (50—55) or Hquid phase (56—60). A fixed-bed reactor is commonly used for the vapor-phase process and the reactor is operated under pressure. A number of catalysts have been cited and include copper, copper on siHca, copper oxide, sulfides of nickel, molybdenum, tungsten, and palladium—vanadium on alumina or Htbium—aluminum spinels. Catalysts cited for the Hquid-phase processes include nickel, copper or cobalt supported on a suitable inert carrier, and palladium or platinum or their mixtures supported on carbon. [Pg.231]

The verification of the presence of hydrogen in the film has proved more controversial, primarily because many of the structural investigations have been carried out after the film has been dried in vacuo. An example of the problems here is the fact that electron diffraction, which has to be carried out in vacuo, reveals a relatively well-crystallised spinel lattice whose origin may be the comparatively high sample heating encountered in the electron beam. Moreover, the use of in situ techniques, such as Mossbauer and X-ray absorption spectroscopy, clearly reveals marked differences between the spectra of the films in situ and the spectra of the same films ex situ as well as the spectra of y-Fe203 and y-FeOOH standards. These differences are most naturally ascribed to hydration of the spinel forms. [Pg.331]

A clear advantage of alkaline electrolysers is the use of nickel-based electrodes, thus avoiding the use of precious metals. Catalytic research is aimed at the development of more active anodes and cathodes, primarily the development of high surface area, stable structures. Nickel-cobalt spinel electrodes for oxygen evolution and high surface area nickel and nickel cobalt electrodes for hydrogen evolution have been shown at the laboratory scale to lead to a decrease in electrolyzer cell voltage [47]. More active electrodes can lead to more compact electrolysers with lower overall systems cost. [Pg.317]

Alkaline Fuel Cell (AFC) The electrolyte in this fuel cell is concentrated (85 wt%) KOH in fuel cells operated at high temperature ( 250°C), or less concentrated (35-50 wt%) KOH for lower temperature (<120°C) operation. The electrolyte is retained in a matrix (usually asbestos), and a wide range of electrocatalysts can be used (e.g., Ni, Ag, metal oxides, spinels, and noble metals). The fuel supply is limited to non-reactive constituents except for hydrogen. CO is a poison, and CO2 will react with the KOH to form K2CO3, thus altering the electrolyte. Even the small amount of CO2 in air must be considered with the alkaline cell. [Pg.19]

Bessekhouad, Y, Trari, M. 2002. Photocatalytic hydrogen production from suspension of spinel powders AMnj03(A=Cu and Zn). Int J Hydrogen Energy 27 357-362. [Pg.153]

Since the spinel phase must be prepared at low temperatures (by hydrothermal synthesis or by careful oxidation of magnetite at a temperature T < 300 C, for example) it has been widely suspected that some incorporation of hydrogen is needed to stabilize it. However, Schrader and Buttner have shown that pure y-Fe203 does exist, and Coey et al. have been able to prepare Fe3 j04 in the compositional range 0 < x < 0.08 by quenching non-stoichiometric magnetite prepared at 1450 °C. There is no evidence that hydrogen is needed to stabilize the system. [Pg.27]

Keyser et al. studied Mn-Co F-T catalysts and found that, under industrial relevant conditions, the WGS activity of the catalysts increases with increasing Mn content, but decreases with increasing pressure. A lower olefin yield was also observed at high pressures. It was stated that structural changes in the cobalt spinel occur over a long period of time and are responsible for the increased hydrogenation activity and increased WGS activity. Mn seems in this... [Pg.36]

Compensation behavior found for the decomposition of hydrogen peroxide on preparations of chromium (III) oxide, which had previously been annealed to various temperatures, was attributed to variations in the energy states of the active centers (here e 0.165). Compensation behavior has also been observed (284) in the decomposition of hydrogen peroxide on cobalt-iron spinels the kinetic characteristics of reactions on these catalysts were ascribed to the electronic structures of the solids concerned. [Pg.303]


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