Nickel promoted catalysts

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). 

Hydrogenation Catalysts. The key to catalytic hydrogenation is the catalyst, which promotes a reaction which otherwise would occur too slowly to be useful. Catalysts for the hydrogenation of nitro compounds and nitriles are generally based on one or more of the group VIII metals. The metals most commonly used are cobalt, nickel, palladium, platinum, rhodium, and mthenium, but others, including copper (16), iron (17), and tellurium... 

In past years, metals in dilute sulfuric acid were used to produce the nascent hydrogen reductant (42). Today, the reducing agent is hydrogen in the presence of a catalyst. Nickel, preferably Raney nickel (34), chromium or molybdenum promoted nickel (43), or supported precious metals such as platinum or palladium (35,44) on activated carbon, or the oxides of these metals (36,45), are used as catalysts. Other catalysts have been suggested such as molybdenum and platinum sulfide (46,47), or a platinum—nithenium mixture (48). 

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 ... 

The NHCs have been used as ligands of different metal catalysts (i.e. copper, nickel, gold, cobalt, palladium, rhodium) in a wide range of cycloaddition reactions such as [4-1-2] (see Section 5.6), [3h-2], [2h-2h-2] and others. These NHC-metal catalysts have allowed reactions to occur at lower temperature and pressure. Furthermore, some NHC-TM catalysts even promote previously unknown reactions. One of the most popular reactions to generate 1,2,3-triazoles is the 1,3-dipolar Huisgen cycloaddition (reaction between azides and alkynes) [8]. Lately, this [3h-2] cycloaddition reaction has been aided by different [Cu(NHC)JX complexes [9]. The reactions between electron-rich, electron-poor and/or hindered alkynes 16 and azides 17 in the presence of low NHC-copper 18-20 loadings (in some cases even ppm amounts were used) afforded the 1,2,3-triazoles 21 regioselectively (Scheme 5.5 Table 5.2). 

Nickel catalysts can be used instead of copper catalysts to promote the conjugate addition reaction, providing, in some cases, better results than the corresponding copper catalysts. In 2000, Yang et al. discovered a series of (li ,25, 3i )-3-mercaptocamphan-2-ol derivatives, which proved to be efficient ligands in the conjugate addition of ZnEt2 to chalcone upon catalysis with Ni(acac)2 (Scheme 2.29). 

Accent [Aqueous carbon compound effluent treatment] A process for oxidizing organic contaminants in aqueous streams by catalyzed oxidation with sodium hypochlorite. The catalyst is promoted nickel oxide, which retains active oxygen at its surface, as well as adsorbing the organics. Developed by ICI Katalco and first offered in 1998. 

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. 

A solid oxide fuel cell (SOFC) consists of two electrodes anode and cathode, with a ceramic electrolyte between that transfers oxygen ions. A SOFC typically operates at a temperature between 700 and 1000 °C. at which temperature the ceramic electrolyte begins to exhibit sufficient ionic conductivity. This high operating temperature also accelerates electrochemical reactions therefore, a SOFC does not require precious metal catalysts to promote the reactions. More abundant materials such as nickel have sufficient catalytic activity to be used as SOFC electrodes. In addition, the SOFC is more fuel-flexible than other types of fuel cells, and reforming of hydrocarbon fuels can be performed inside the cell. This allows use of conventional hydrocarbon fuels in a SOFC without an external reformer. 

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). 

Ce02-supported noble-metal catalysts such as Pt, Pd and Rh are of interest because of their importance in the so-called three-way converter catalysts (TWC), designed to reduce emissions of CO, NOx and uncombusted hydrocarbons in the environment and to purify vehicle-exhaust emissions. Such catalysts are also of current interest in steam reforming of methane and other hydrocarbons. Conventional practical catalysts for steam reforming consist of nickel supported on a ceramic carrier with a low surface area and are used at high temperatures of 900 C. This catalyst suffers from coke formation which suppresses the intrinsic catalyst activity. Promoters such as Mo are added to suppress coke formation. Recently, Inui etal(l991) have developed a novel Ni-based composite... 

McQuade et al. [11] have pubhshed a nice synthesis using a microencapsulated nickel-based catalyst for promoting a Henry reaction based upon the work of Evans [12]. Torrens et al. have pubhshed a somewhat longer synthesis from D-mannitol bisacetonide [13]. 

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 desulfurized feedstock is then mixed with superheated steam and passed over a nickel catalyst (730 to 845°C 1350 to 1550°F 400 psi) to produce a mixture of hydrogen, carbon monoxide, and carbon dioxide as well as excess steam. The effluent gases are cooled (to about 370°C 700°F) and passed through a shift converter which promotes reaction of the carbon monoxide with stream to yield carbon dioxide and more hydrogen. The shift converter may contain two beds of catalyst with interbed cooling the combination of the two catalyst beds promotes maximum conversion of the carbon monoxide. This is essential in the event that a high-purity product is required. 

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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