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Raney nickel composition

Dry reduced nickel catalyst protected by fat is the most common catalyst for the hydrogenation of fatty acids. The composition of this type of catalyst is about 25% nickel, 25% inert carrier, and 50% soHd fat. Manufacturers of this catalyst include Calsicat (Mallinckrodt), Harshaw (Engelhard), United Catalysts (Sud Chemie), and Unichema. Other catalysts that stiH have some place in fatty acid hydrogenation are so-called wet reduced nickel catalysts (formate catalysts), Raney nickel catalysts, and precious metal catalysts, primarily palladium on carbon. The spent nickel catalysts are usually sent to a broker who seUs them for recovery of nickel value. Spent palladium catalysts are usually returned to the catalyst suppHer for credit of palladium value. [Pg.91]

Replacement of halides with deuterium gas in the presence of a surface catalyst is a less useful reaction, due mainly to the poor isotopic purity of the products. This reaction has been used, however, for the insertion of a deuterium atom at C-7 in various esters of 3j -hydroxy-A -steroids, since it gives less side products resulting from double bond migration. Thus, treatment of the 7a- or 7j5-bromo derivatives (206) with deuterium gas in the presence of 5% palladium-on-calcium carbonate, or Raney nickel catalyst, followed by alkaline hydrolysis, gives the corresponding 3j3-hydroxy-7( -di derivatives (207), the isotope content of which varies from 0.64 to 1.18 atoms of deuterium per mole. The isotope composition and the stereochemistry of the deuterium have not been rigorously established. [Pg.200]

Concurrent hydrogenation of acetone (A) and cyclohexene (B) in cyclohexane occurs with Raney nickel catalyst at 25. Catalyst concentration was 2 g/liter and the product compositions also are in g/liter. Determine the orders and relate the amounts of the reactants. [Pg.231]

Hydrogenation over Raney nickel was found to be even less stereoselective. 2-, 3- and 4-methylmethylenecyclohexenes gave different mixtures of cis and irons dimethylcyclohexanes depending not only on the structure of the starting alkene but also on the method of preparation and on the freshness of the catalysts. The composition of the stereoisomers ranged from 27-72% cis to 28-73% irons [340],... [Pg.41]

Dimethyl-7-methoxyoctan-2-ol is prepared by hydrochlorination of dihy-dromyrcene, methoxylation of the resulting 2-chloro-2,6-dimethyl-7-octene and epoxidation. The alcohol is obtained by hydrogenation of the epoxide in the presence of Raney nickel and triethylamine [53]. It is used in perfumery as a top note in high quality sandalwood compositions for cosmetics, toiletries, and soaps. [Pg.34]

On the other hand, hydrogenation with Raney nickel causes reduction mainly in the substituted aromatic ring [Eq. (11.16)]. Differences in product composition brought about by the different metals are explained in terms of steric hindrance of the substituted ring (Pt, Pd) versus the anchor effect of the methyl substituent (Ni).106... [Pg.631]

Microscopic and spectroscopic investigations (SEM and XPS) reveal the relatively fast change of the chemical composition of nickel sulfide coatings upon the onset of cathodic hydrogen evolution (74). Indeed, at 90°C all nickel sulfide phases are reduced to porous nickel within several days to a week s time. They lose some catalytic activity with time with an increase in overvoltage between 0.15 and 0.3 V after continuous operation for 1 year. It is clear that the catalyst after I week is already no longer nickel sulfide but some type of Raney nickel. Thus far the initial catalytic activity of the NiS, coating is of little relevance. The respective results and data are due to be published by the present authors (73). [Pg.113]

Newman and co-workere 240 published in lt)4D a careful study of tile variation in production composition when 1,2-epoxy octane was reduced over Raney nickel at 150° under neutral, alkaline, and acidic conditions. Their results, Bonmarized in Eq. (3 1), are rather striking. [Pg.391]

Raney nickel catalysts, unpromoted or doped with molybdenum or chromium, were prepared from the precursor alloys of the type Ni A13. The structure and phase composition of the catalysts have been deternfmetl. Hydrogenation of valeronitri le at 90°C and 1.6 MPa in cyclohexane was performed to evaluate catalyst activities and the relative amounts of amines formed. Doping catalysts by chromium improved reaction rates and yields of primary amine, whereas molybdenum addition was ineffective. [Pg.113]

Table 1 Composition and characterization of Raney-nickel catalysts... Table 1 Composition and characterization of Raney-nickel catalysts...
Figure 1 illustrates the ooserved product composition as a function of time in standard conditions. In the presence of Raney nickel, if AC is still present (step 1), the hydrogenation gives almost exclusively PE and very little MCK. When all AC has disappeared (step 2) the rate of hydrogenolysis of... [Pg.246]

For hydrogen oxidation bi-component metal doped systems deposited on Raney nickel for AFC Mo and W carbides for AFC prepared by method of precipitation from a gas phase Radicals of following composition -OH, -OSO3H, -COOH, -OPO(OH)3 for PEMFC Some organic catalysts like biologically active [NiFe]-hydrogenase, pyropolymers, etc. ... [Pg.182]

ESMS has been used to characterize the intermediate Nin-complexes formed in the coupling reaction of 2-bromo-6-methylpyridine in the presence of Raney nickel (Scheme 1) [45]. The composition of the intermediate had already been determined previously by elemental analysis, but the ES mass spectra, showing a strong peak for the ion [Ni2(dmbp)2Br3]+, pointed to a dimeric structure. It was concluded that this ion was formed by the loss of Br from the dimeric structure 1. An alternative explanation is that the intermediate has the more common four-coordinate structure 2, and that the observed peak was due to the ion-paired species [Ni2(dmbp)2Br2]2++Br. The dimeric nature of the intermediate was confirmed by a cross experiment when mixtures of differently substituted pyridines were reacted, mixed ligand dinickel species were observed in the ES mass spectra. [Pg.162]

Raney nickel electrocatalysts have also found useful applications as active electrodes for the HER (179, 180). The activity of Raney Ni catalysts is established after leaching out the base metal, Al or Zn. Choquette et al. (181) have examined the changes in morphology and composition of Raney-Ni composite catalytic electrodes accompanying dissolution of the base metal in concentrated NaOH. The depletion of Al from the Raney particles is, of course, accompanied by a major increase in real area with time of leaching and also, interestingly, with possible phase transformations (181). The electro-catalytic activity is, however, surprisingly, practically independent of time. [Pg.68]

Raney nickel is a sponge-like material made up of 2.5-15 nm microcrystallites that are agglomerated into macroparticles several microns in diameter. The surface area and composition of these particles depend on the base concentration and temperature used for the removal of the aluminum from the alloy. High temperature preparations that remove almost all of the aluminum generally have a surface area of 50-80 m /g. Catalysts prepared at temperatures of 50°C or lower have more aluminum present and surface areas of 100-120 m /g. These surface areas are related to the pore diameters and pore volume of the catalysts. The more extensive the base attack on the alloy the larger the average pore diameter and pore volume of these particles and the smaller their surface area. ... [Pg.246]

Porous alloy electrodes of Raney nickel are often used in electrolyzers. Raney nickel is produced by first making an alloy composed of 50% aluminum and 50% nickel. This composite is then treated with potassium hydroxide, which eats away the aluminum and leaves a porous nickel sponge material, known as Raney nickel after Murray Raney, the inventor of the process. Electrolyzer electrodes of this material have a large surface area due to their porosity and will produce more gas with smaller electrodes, compared to electrodes made of materials with less surface area, such as sheet or screen. Although Raney nickel is preferred, it is more expensive than either sheet or screen. The porous texture that creates a larger surface area also acts as a filter for small particles. The sediment which forms reduces the active surface area over time, inhibiting gas formation and thus efficiency. [Pg.77]


See other pages where Raney nickel composition is mentioned: [Pg.24]    [Pg.87]    [Pg.173]    [Pg.119]    [Pg.454]    [Pg.219]    [Pg.358]    [Pg.87]    [Pg.232]    [Pg.89]    [Pg.89]    [Pg.227]    [Pg.93]    [Pg.13]    [Pg.427]    [Pg.87]    [Pg.241]    [Pg.217]    [Pg.207]    [Pg.31]    [Pg.419]    [Pg.321]    [Pg.233]    [Pg.156]    [Pg.842]   
See also in sourсe #XX -- [ Pg.246 ]




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