Nickel Promoted

Selectivity is primarily a function of temperature. The amount of by-products tends to increase as the operating temperature is raised to compensate for declining catalyst activity. By-product formation is also influenced by catalyst impurities, whether left behind during manufacture or otherwise introduced into the process. Alkaline impurities cataly2e higher alcohol production whereas acidic impurities, as well as trace iron and nickel, promote heavier hydrocarbon formation. 

Catalysts used for preparing amines from alcohols iaclude cobalt promoted with tirconium, lanthanum, cerium, or uranium (52) the metals and oxides of nickel, cobalt, and/or copper (53,54,56,60,61) metal oxides of antimony, tin, and manganese on alumina support (55) copper, nickel, and a metal belonging to the platinum group 8—10 (57) copper formate (58) nickel promoted with chromium and/or iron on alumina support (53,59) and cobalt, copper, and either iron, 2iac, or zirconium (62). 

Catalyst choice is strongly influenced by the nature of the feedstock to be hydrotreated. Thus, whereas nickel-promoted and cobalt—nickel-promoted molybdenum catalysts can be used for desulfurization of certain feedstocks and operating conditions, a cobalt-promoted molybdenum catalyst is generally preferred in this appHcation. For denitrogenation and aromatics saturation, nickel-promoted molybdenum catalysts usually are the better choice. When both desulfurization and denitrogenation of a feedstock are required, the choice of catalyst usually is made so that the more difficult operation is achieved satisfactorily. 

Here we illustrate how to use kinetic data to establish a power rate law, and how to derive rate constants, equilibrium constants of adsorption and even heats of adsorption when a kinetic model is available. We use the catalytic hydrodesulfurization of thiophene over a sulfidic nickel-promoted M0S2 catalyst as an example ... 

A nickel-promoted C—S bond cleavage has been reported,860 which occurs when solutions of the Ni1 complex of (330) are electrogenerated. The product was identified by cyclic voltammetry and spectroscopy as [Ni(C6H4S2)2]2. EPR and NMR evidence suggests a one-electron mechanism, involving reduction to a 19-electron Ni1 species, electron transfer, and concomitant C—S bond cleavage, extrusion of ethylene followed by a further one-electron reduction and extrusion of ethylene sulfide. 

The sulfidation mechanisms of cobalt- or nickel-promoted molybdenum catalysts are not yet known in the same detail as that of M0O3, but are not expected to be much different, as TPS patterns of Co-Mo/A1203 and Mo/Al203 are rather similar [56J. However, interactions of the promoter elements with the alumina support play an important role in the ease with which Ni and Co convert to the sulfidic state. We come back to this after we have discussed the active phase for the hydrodesulfurization reaction in more detail. 

In the absence of the olefin, the corresponding biaryls are formed in moderate yields (like the Raney nickel-promoted detellurations (see Section 4.6.1.1)). 

Ji et al. have shown that nickel-promoted tungsten carbide catalysts can also directly convert cellulose to ethylene glycol in a one step process [52, 53]. These Ni-W2C/AC catalysts exhibited a remarkable higher selectivity for ethylene glycol than Pt/Al203 and Ru/C. Indeed, after 30 min of reaction at 518 K under 60 bar of H2, cellulose was completely converted into water-soluble polyols over a 2% Ni-30% W2C/AC-973 catalyst (61% yield in ethylene glycol). 

Nickel-promoted couplings between 1,3-dienes, C02 and organozincs have also been reported78. Thus, 1,3-cyclohexadiene in the presence of Ni(COD)2 and DBU, under an... 

Molybdena catalysts have been with us for quite a long time. The term molybdena is used here to denote a composite catalyst consisting of molybdenum oxide supported on an activated support, commonly alumina. Early it was found that certain transition metals, notably cobalt and nickel, promote the molybdena catalyst for hydrodesulfurization (HDS) reactions. 

The Structural Form of Cobalt and Nickel Promoters in Oxidic HDS Catalysts... 

Nickel Promoted Catalysts. Nickel containing catalysts are known to be sensitive for too high temperatures. The Dutch patent 123195 (17) claims that active nickel-molybdenum-alumina catalysts are obtained, when nickel is impregnated first. The calcination is critical however. According to this patent, catalysts calcined at 480 are twice as active as catalysts, calcined at 650°C. 

Similar interactions have been observed for the nickel promoted catalyst. However, the degree of interaction depends on the calcination temperature. This interaction disappears for a great part at increasing temperatures. This is ascribed to bulk nickel aluminate formation. 

These observations might contribute to the understanding of the differences in catalytic performance between cobalt and nickel promoted hydrodesulfurization catalysts. 

A wide variety of metals are active hydrogenation catalysts those of most interest are nickel, palladium, platinum, cobalt, iron, nickel-promoted copper, and copper chromite. Special preparations of the first three are active at room temperature and atmospheric pressure. The metallic catalysts are easily poisoned... 

Virtually all of these processes rely on promoted molybdenum sulfide (MoS2) catalysts. Hydrodenitrogenation catalysts are usually nickel-promoted... 

The dibenzazonine (13), related to a biosynthetic precursor of the Erythrina alkaloids, has been prepared in 35% yield by the intramolecular nickel-promoted coupling of the bis-(2-phenylethyl)amine (14), which in turn was obtained from the commercially available (3-methoxyphenyl)acetic acid by a conventional series of reactions.16... 

The sulfidation mechanisms of cobalt- or nickel-promoted molybdenum catalysts are not yet known in the same detail as that of M0O3, but they are not ex-... 

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