Hydrogen activating nickel

Fan, C. L., Teixeira, M., Moura, J., Moura, I., Huynh, B. H., Legall, J., Peck, H. D. and Hoffman, B. M. (1991) Detection and characterization of exchangeable protons bound to the hydrogen-activation nickel site of Desulfovibrio gigas hydrogenase - a H-1 and H-2 Q-band ENDOR study./. Amer. Chem. Soc., 113, 1-24... 

Fan C,Teixeira M, Moura J, et al. 1991. Detection and characterization of exchangeable protons bound to the hydrogen-activating nickel site of Desulfovibrio gigas hydrogenase a and Q-band ENDOR study. J Am Chem Soc 113 20. ... 

Fan C, Teixeira M, Moura JJG, Moura I, Huynh BH, LeGall J, Peck Jr HD, Hofftnan BM. 1991. Detection and characterisation of exchangable protons bound to the hydrogen-activation nickel site of desulfovibrio gigas hydrogenase a H and H Q-Band ENDOR study. JAm Chem Soc 113 20-24. 

In normal battery operation several electrochemical reactions occur on the nickel hydroxide electrode. These are the redox reactions of the active material, oxygen evolution, and in the case of nickel-hydrogen and nickel-metal hydride batteries, hydrogen oxidation. In addition there are parasitic reactions such as the corrosion of nickel current collector materials and the oxidation of organic materials from separators. The initial reaction in the corrosion process is the conversion of Ni to Ni(OH)2. 

Recently, other authors when studying the activation of hydrogen by nickel and nickel-copper catalysts in the hydrogen-deuterium exchange reaction concentrated for example only on the role of nickel in these alloys (56) or on a correlation between the true nickel concentration in the surface layer of an alloy, as stated by the Auger electron spectroscopy, and the catalytic activity (57). 

On the basis of information on the properties of the nickel-hydrogen and nickel-copper-hydrogen systems available in 1966 studies on the catalytic activity of nickel hydride as compared with nickel itself were undertaken. As test reactions the heterogeneous recombination of atomic hydrogen, the para-ortho conversion of hydrogen, and the hydrogenation of ethylene were chosen. 

Reactions leading to the formation of the catalytically active nickel hydride species from organonickel precursors (Section III) can be regarded as model reactions for olefin oligomerization reactions. The reactions described by Eq. (8) and Scheme 3 (Section III) show that RNiX compounds (R = methyl orallyl, X = halide or acetylacetonate) activated by Lewis acids add to double bonds under mild reaction conditions (-40° or 0°C). It follows further from these reactions that under conditions leading to olefin dimerization a rapid nickel hydride /3-hydrogen elimination reaction occurs. The fact that products resulting from olefin insertion into the nickel-carbon bond are only observed when /3-hydride... 

Raney nickel has long been known as a hydrogenation catalyst. Other forms of active nickel can be easily prepared by reducing nickel salts in situ with NaBH4, Fe, Grignard reagents, etc. (199-202). 

Carbon monoxide oxidation is a relatively simple reaction, and generally its structurally insensitive nature makes it an ideal model of heterogeneous catalytic reactions. Each of the important mechanistic steps of this reaction, such as reactant adsorption and desorption, surface reaction, and desorption of products, has been studied extensively using modem surface-science techniques.17 The structure insensitivity of this reaction is illustrated in Figure 10.4. Here, carbon dioxide turnover frequencies over Rh(l 11) and Rh(100) surfaces are compared with supported Rh catalysts.3 As with CO hydrogenation on nickel, it is readily apparent that, not only does the choice of surface plane matters, but also the size of the active species.18-21 Studies of this system also indicated that, under the reaction conditions of Figure 10.4, the rhodium surface was covered with CO. This means that the reaction is limited by the desorption of carbon monoxide and the adsorption of oxygen. 

As Figure 14.5 shows, the enantio-differentiating (e.d.) hydrogenation consists of three processes (1) catalyst preparation, (2) chiral modification, and (3) hydrogenation reaction. These processes imply preparation variables for activated nickel, as a base catalyst for modified Ni, modification variables for the activated catalyst, and reaction variables of the hydrogenation processes, respectively. All these factors should be optimized for each type of substrate. 

F-T Catalysts The patent literature is replete with recipes for the production of F-T catalysts, with most formulations being based on iron, cobalt, or ruthenium, typically with the addition of some pro-moter(s). Nickel is sometimes listed as a F-T catalyst, but nickel has too much hydrogenation activity and produces mainly methane. In practice, because of the cost of ruthenium, commercial plants use either cobalt-based or iron-based catalysts. Cobalt is usually deposited on a refractory oxide support, such as alumina, silica, titania, or zirconia. Iron is typically not supported and may be prepared by precipitation. 

Complete reduction of alkynes to alkanes is easily accomplished by catalytic hydrogenation, especially using palladium [386, 387], platinum oxide and active nickel catalysts [559]. 

Concerning the possible reaction mechanism, the activated lithium can both reduce the nickel(II) salt to give nickel(O) and react with the crystallization water present in the metallic salt to produce molecular hydrogen. However, no gas evolution was observed in the reaction, so the hydrogen initially formed was probably adsorbed on the surface of the active nickel to perform like hydrogenation without hydrogen in the sense that no external source of molecular hydrogen was employed. 

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