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Nickel requirement

Nickel catalysts although less expensive than rhodium and platinum are also less active Hydrogenation of arenes m the presence of nickel requires high temperatures (100-200°C) and pressures (100 atm)... [Pg.428]

The most efficient processes in Table I are for steel and alumintim, mainly because these metals are produced in large amounts, and much technological development has been lavished on them. Magnesium and titanium require chloride intermediates, decreasing their efficiencies of production lead, copper, and nickel require extra processing to remove unwanted impurities. Sulfide ores produce sulfur dioxide (SO2), a pollutant, which must be removed from smokestack gases. For example, in copper production the removal of SO, and its conversion to sulfuric acid adds up to 8(10) JA g of additional process energy consumption. In aluminum production disposal of waste ciyolite must be controlled because of possible fiuoride contamination. [Pg.772]

Electrolysis Highly conductive (both nickel Requires specialized equipment/... [Pg.393]

The synthesis of aromatic amines is an active and important area of research.2 Many methods are available in the literature for the synthesis of these compounds. Though some of these are widely used, still they have limitations based on safety or handling considerations. For example, catalytic hydrogenation3 of nitro or azido compounds in the presence of metals such as palladium on carbon or Raney nickel require stringent precautions because of their flammable nature in the presence of air. In addition, these methods require compressed hydrogen gas and a vacuum pump to create high pressure within the reaction flask. To overcome these difficulties, several new methods have been reported in the... [Pg.98]

Y. P. Chen, D. C. Yoch (1987) Regulation of two nickel-requiring (inducible and constitutive) hydrogenases and their coupling to nitrogenase in Methylosinus trichosporium OB3b. J. Bacteriol., 169 4778-4783... [Pg.30]

No nickel-requiring enzymes or proteins are known in vertebrates, although biological roles of nickel enzymes and cofactors have been found in plants and bacteria. Although the role of nickel in human physiology has not been confirmed directly, the evidence strongly suggests that nickel is required by humans [263],... [Pg.207]

Gleichmann E Oral tolerance to nickel requires CD4+ invariant NKT cells for the infectious spread of tolerance and the induction of specific regulatory T cells. J Immunol 2004 173 1043-1050. [Pg.100]

Friedrich, B., Heine, E., Finck, A. and Friedrich, C. G. (1981) Nickel requirement for active hydrogenase formation in Alcaligenes eutropbus. ]. Bacterial., 145, 1144-9. [Pg.263]

Studies identifying endocrine effects in animals do not clearly identify a dose-response relationship. In addition, it has been suggested that nickel has a physiological role in endocrine gland function, affecting prolactin levels (Kenney and McCoy 1992). Therefore, further research is required to differentiate levels of nickel required by humans for normal endocrine function, compared to levels that may impair endocrine function leading to adverse effects. It is unlikely that environmental exposure or exposure to nickel at hazardous waste sites will result in endoerine effects. [Pg.127]

Thioketals, unlike ordinary ketals, are formed readily from ketones and thiols (RSH) in the presence of acid catalysts. The desulfurization procedure usually goes well, but the product is rather difficult to separate by extraction from the large excess of Raney nickel required for optimum yields. [Pg.712]

Nickel is deposited quantitatively from ammoniacal solutions, incompletely from weakly acidic solutions, and not at all from strongly acidic ones. (A quantitative separation of copper from nickel requires that the acid concentration be kept high.) Among the important interferences in the determination of nickel are silver, copper, arsenic, and zinc, which can be removed by precipitation with hydrogen sulfide. Iron(II) and chromates are objectionable, but can be removed by precipitation of the hydrous oxides. [Pg.272]

W2 Raney nickel is appreciably more active than Wl as shown by the fact that the hydrogenation of P-naphthol at a specific temperature and pressure required 240 minutes with the Wl catalyst but was complete in 15 minutes using the W2 Raney nickel. For this same reaction, W4 Raney nickel required only half as long as did the W2 (Eqn. 12.11). This increased activity of the W4... [Pg.242]

Copper, nickel, and cobalt were found by Seitz (5) to diminish the height of the zinc current peak by broadening it. Although the concentration of cobalt in seawater was deemed too low to cause serious problems, the eflFect of copper and nickel required further study. The interference by copper in the stripping determination of zinc was extensively investigated by Bradford (8). He concluded that in the mercury film, copper and zinc formed a 1 1 intermetallic compound that dissociated to release zinc during the oxidation. Thus zinc peak areas remained proportional to the zinc concentration even in the presence of copper, and the analysis of zinc by standard addition was not affected. The interference from nickel was found to be similar to that from copper although the stoichiometry of the intermetallic compoimd could not be determined. [Pg.90]

The normative nickel requirement of ruminants amounts to 100-350 ig kg feed DM, while that of humans amounts to 35-50 pg per day (Anke etal. 1973a,... [Pg.317]

Anke 1985). The nickel requirement of animals and man is met by all natural diets. Thus, secondary nickel deficiency is to be expected probably because some rumen bacteria use nickel as a part of their enzyme urease. There is clear evidence that nickel is essential for the fauna. [Pg.317]

At 25-35 pg, the normal daily nickel requirement (Nielsen 1987, Anke et al. 1991a) is comparable with that of molybdenum and selenium (Table 4.8). The normative requirement per kg body weight is 0.5 pg Ni (Anke et al. 2000e, Eder and Kirch-gessner 1997, Triipschuch 1997). [Pg.350]

Relevant to the conflicting reports of copper versus nickel requirements for enzyme activity,biochemical studies demonstrated the existence of a labile nickel associated with the a subunit of ACS/CODH. Very recently, model studies on a metal-ion capture of a peptide-backbone, nonlabile [NiN2S2] (26) unit have established the capability of such a nickel dithiolate to bind exogeneous metals. A qualitative ranking of the binding ability of complex (26) with Zn +, Cu+, and Ni + was established by a metal-ion displacement experiment (Zn + < Ni + < Cu+), as shown in Scheme 9. A concept that the chemically most reasonable dinickel ACS... [Pg.2900]

Oxidative hydrolysis of an ethylene dithioketal. Cain and Welling report that the method of Corey and Erickson (4,216) for oxidative hydrolysis of 2-acyl-1,3-dithianes is also useful for unmasking of ethylene dithioketals. Thus treatment of the bisethylene dithioketal (1) with 4 eq. of NBS in 10% aqueous acetone at 0° for 20 min. selectively removes the less hindered ethylene dithioketal group at C to give (2) in 80% yield. Removal of the ethylene dithioketal group at C2 with Raney nickel requires reflux in ethanol and is accompanied by reduction of the carbonyl group. [Pg.41]

Medical Significance. An initial impression Is that nickel nutrlture would not be of practical significance. I W reported that 50 yg of nickel/kg of diet satisfied the dietary nickel requirement of chicks, and Schnegg and Kirchgessner ( ) reported a similar requirement for rats. If animal data were extrapolated to man, the dietary nickel requirement of humans... [Pg.31]

Limited studies indicate that the oral intake of nickel by humans ranges between 170 and 700 yg per day (33) which would be ample to meet the hypothesized nickel requirement. [Pg.32]

It is interesting to note that the results obtained in this work for the high-temperature reaction between acetone and H2 show that hydrogenation of MSO to MIBK by nickel is easier to carry out than that of acetone to 2-propanol, since 2-propanol is produced only when a high excess of reduced nickel is present with respect to the nickel required to hydrogenate all the MSO found. [Pg.388]


See other pages where Nickel requirement is mentioned: [Pg.135]    [Pg.409]    [Pg.211]    [Pg.361]    [Pg.11]    [Pg.119]    [Pg.284]    [Pg.620]    [Pg.191]    [Pg.389]    [Pg.389]    [Pg.136]    [Pg.284]    [Pg.422]    [Pg.299]    [Pg.908]    [Pg.205]    [Pg.223]    [Pg.104]    [Pg.846]    [Pg.851]    [Pg.76]    [Pg.126]   
See also in sourсe #XX -- [ Pg.317 , Pg.851 ]




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