Nickel catalyst alternatives

A temperature of 700 to 800 °C is optimal, with a nickel catalyst. Alternatively, methane can be partially oxidized with pure oxygen ... 

The effect of physical processes on reactor performance is more complex than for two-phase systems because both gas-liquid and liquid-solid interphase transport effects may be coupled with the intrinsic rate. The most common types of three-phase reactors are the slurry and trickle-bed reactors. These have found wide applications in the petroleum industry. A slurry reactor is a multi-phase flow reactor in which the reactant gas is bubbled through a solution containing solid catalyst particles. The reactor may operate continuously as a steady flow system with respect to both gas and liquid phases. Alternatively, a fixed charge of liquid is initially added to the stirred vessel, and the gas is continuously added such that the reactor is batch with respect to the liquid phase. This method is used in some hydrogenation reactions such as hydrogenation of oils in a slurry of nickel catalyst particles. Figure 4-15 shows a slurry-type reactor used for polymerization of ethylene in a sluiTy of solid catalyst particles in a solvent of cyclohexane. 

The bottle is connected to the hydrogenation apparatus and alternately evacuated and filled with hydrogen twice. Hydrogen is then admitted to the system until the pressure gauge reads 40 lb. The shaker is started, and the pressure drops to the theoretical value for absorption of 0.6 mole in 15-20 minutes beyond this point shaking causes no further absorption of hydrogen (Note 2). The bottle is removed and the nickel catalyst is allowed to settle. The tetrahydropyrane is decanted, but enough... 

A. 2,4,6-Tnphenylaniline. To a filtered solution of 70 g. (0.20 mole) of 2,4,6-triphenylnitrobenzene (Note 1) in 500 ml. of dioxane (total volume ca. 540 ml.) in a 1-1. pressure vessel equipped with a magnetic stirrer is added 10 g. of Raney nickel catalyst (Note 2) that has been previously rinsed with absolute ethanol. The head and fittings are attached, and the vessel is connected to a hydrogen cylinder. The system is alternately... 

Enalapril Enalapril, (S)-l-[iV-[l-(ethoxycarbonyl)-3-phenylpropyl]-L-alanyl]-L-proline (22.7.12), is synthesized by reacting the benzyl ester of L-alanyl-L-proline with the ethyl ester of 3-benzoylacrylic acid, which forms the product 22.7.11, the reduction of which with hydrogen using a Raney nickel catalyst removes the protective benzyl group, giving the desired enalapril (22.7.12) [24], Alternative methods of syntheses have also been proposed [25-29]. 

Alternative catalyst formulations for methane ATR based on bimetallic catalysts have been studied, aiming at increasing the activity of nickel catalysts by the addition of low contents of noble metals. 

However, since C10 (aq) is thermodynamically unstable with respect to decomposition to chloride ion and oxygen gas (see Exercise 12.2), catalytic decomposition is an attractive alternative to chemical reduction. ICI s HY-DECAT system achieves this with a proprietary supported nickel catalyst.5... 

Alternatively, methane can be manufactured by the reaction of carbon monoxide and hydrogen in the presence of a nickel catalyst. Methane also is formed by reaction of magnesium methyl iodide (Grignard s reagent) in anhydrous ether with substances containing the hydroxyl group. Methyl iodide (bromide, chloride) is preferably made by reaction of methyl alcohol and phosphorus iodide (bromide, chloride). 

Supported and coprecipitated nickel catalyst represent an interesting alternative, from the economical point of view, to other selective hydrogenation catalysts such as Pt or Pd, of higher performance but also with a higher price. In the present study, a coprecipitated NiO/NiAl 04 catalyst has been selected to cany out the selective hydrogenation of acetylene to ethylene as a test reaction. One important characteristic of this process is the large amount of coke which may be generated [l]. 

Because of its pyrophoric nature, the nickel catalyst should not be allowed to dry on the filter. A convenient alternative procedure for removing catalyst is to centrifuge the reaction mixture. 

Alternative catalysts such as palladium-on-barium sulfate (poisoned by synthetic quinoline) (24), "P-2" nickel boride (with ethylenediamine) (25), and other nickel catalysts (19c) can be used in place of Lindlar catalyst. However, in our hands selective hydrogenation of triple bonds to Z olefins proceeds with the greatest stereoselectivity with Lindlar catalyst. Palladium-on-barium sulfate (in ethanol with quinoline) can give considerable over-reduction and isomerization to the E isomer (22a). Use of "P-2" nickel boride as the catalyst at room temperature usually gives a. 2% of the J5 isomer (e.g. 23). 

If a carrier is to be incorporated in the final catalyst, the original precipitation is usually carried out in the presence of a suspension of the finely divided support or, alternatively, a compound or suspension, which will eventually be converted to the support, may initially be present in solution. Thus, a soluble aluminum salt may be converted to aluminum hydroxide during precipitation and ultimately to alumina. Alternatively, a supported nickel catalyst could be prepared from a solution of nickel nitrate, containing a suspension of alumina, by precipitation of a nickel hydroxide with ammonia. 

Supported nickel catalysts, the analogues Raney nickel prepared from amorphous alloys of Ni-Al with a metalloid such as B or P, and supported Rh catalysts are some of the alternatives currently under study. 

Figure 14 Alternative propylene insertion modes in diimine-nickel catalysts (RLS = rate-limiting step).

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