Supported nickel

Supported Nickel. - The interaction of nickel with siUca and alumina at various stages of catalyst preparation has been extensively studied and only some recent evidence for interaction and its effect on performance are noted here. Nickel nitrate impregnated on silica decomposed to NiO during calcination, which interacted little with the support, whereas the ESCA spectrum of low nickel loadings on 7-alumina were quite different and NiO only appeared once the surface sites were filled. After reduction at 673 K and examination by ESCA without exposure to air, it was shown that percentage reduction depended on both Ni content and calcination temperature, which was considered indicative of a strong interaction between nickel and alumina. Nickel ions in octahedral sites are readily reduced and increasing the calcination temperature makes them diffuse to tetrahedral sites where they are difficult to reduce. 

Metal-support interaction was observed in two nickel-silica catalysts, but they were prepared either by precipitating a complex carbonate from nickel nitrate solution containing Si02 as a slurry or co-precipitating the carbonate from a solution of nickel nitrate and sodium silicate. The similar spectra from the unreduced catalysts resembled in shape and binding energy a NiSi03 standard and were quite distinct from NiO. The interaction was 

Mattogno, G. Polsonetti, and G. R. Tauszik, J. Electron Spectrosc. Relat. Phenom., 1978, 14, 237. 

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Reduction. Acetaldehyde is readily reduced to ethanol (qv). Suitable catalysts for vapor-phase hydrogenation of acetaldehyde are supported nickel (42) and copper oxide (43). The kinetics of the hydrogenation of acetaldehyde over a commercial nickel catalyst have been studied (44). 

Chemical exchange between hydrogen and steam (catalyzed by nickel—chromia, platinum, or supported nickel catalysts) has served as a pre-enrichment step in an electrolytic separation plant (10,70). If the exchange could be operated as a dual-temperature process, it very likely... 

Hydrogenation of Acetaldehyde. Acetaldehyde made from acetylene can be hydrogenated to ethanol with the aid of a supported nickel catalyst at 150°C (156). A large excess of hydrogen containing 0.3% of oxygen is recommended to reduce the formation of ethyl ether. Anhydrous ethanol has also been made by hydrogenating acetaldehyde over a copper-on-pumice catalyst (157). 

This solution Is heated to 65°C and barium hydroxide added in quantity sufficient to make the concentration of the barium hydroxide 0.2 mol/liter. The solution is agitated and maintained at 65°C for 6 hours after the addition of the barium hydroxide. It is then cooled and neutralized to a pH of 6.8 with sulfuric acid. The precipitated barium sulfate is filtered out. A quantity of activated supported nickel catalyst containing 5 g of nickel is added. 

Nickel. As a methanation catalyst, nickel is presently preeminent. It is relatively cheap, it is very active, and it is the most selective to methane of all the metals. Its main drawback is that it is easily poisoned by sulfur, a fault common to all the known active methanation catalysts. The nickel content of commercial nickel catalysts is 25-77 wt %. Nickel is dispersed on a high-surface-area, refractory support such as alumina or kieselguhr. Some supports inhibit the formation of carbon by Reaction 4. Chromia-supported nickel has been studied by Czechoslovakian and Russian investigators. 

When we first contemplated thermochemical products available from Glu, a search of the literature revealed no studies expressly directed at hydrogenation to a specific product. Indeed, the major role that Glu plays in hydrogenation reactions is to act as an enantioselectivity enhancer (17,18). Glu (or a number of other optically active amino acids) is added to solutions containing Raney nickel, supported nickel, palladium, or ruthenium catalysts and forms stereoselective complexes on the catalyst surface, leading to enantioselective hydrogenation of keto-groups to optically active alcohols. Under the reaction conditions used, no hydrogenation of Glu takes place. 

A new isomerization catalyst can be prepared by the modification of silica-supported nickel with tetrabutyltin. This catalyst is capable of the selective isomerization of 3-carene to 2-carene.269... 

Oldenberg and Rase (13) have studied the catalytic vapor phase hydrogenation of pro-pionaldehyde over a commercially supported nickel catalyst. Their data indicate that the mathematical form of the reaction rate at very low conversions and 150 °C can be expressed quite well in the following manner. 

Mixtures of ethylene and aluminium chloride, initially at 30-60 bar, rapidly heat and explode in presence of supported nickel catalysts, methyl chloride or... 

As the data in Table XIV indicate, over platinum demethylation of a ring is slow compared to C—C bond rupture within a ring. On the other hand, it is well established [e.g., Kochloefl and Bazant (161) that if one uses a supported nickel catalyst which is known to favor stepwise alkane degradation, reaction with an alkylcycloalkane is largely confined to the alkyl group (s) which are degraded in a stepwise fashion and are finally removed entirely from the ring. 

Fig. 2. (a) Magnetization-volume isotherms for the chemisorption of hydrogen and of benzene on kieselguhr-supported nickel at 150° C (16). (b) Average number of bonds formed by benzene adsorbed on nickel-silica as a function of temperature (17). From J. Amer. Chem. Soc. 79, 4637 (1957) 83, 1033 (1961). Copyright by the American Chemical Society. Reprinted by permission of copyright owner. 

In the cracking of benzene to acetylene over alumina- and silica-supported nickel catalysts it was observed that the selectivity of the reaction, expressed as the ethyne/ ethene ratio, was dramatically affected (from 1 9 to 9 1) by controlling the micro-wave energy input (i. e. 90% selectivity) [83]. 

Alstrup, I. and Tavares, T., Kinetics of carbon formation from CH4-H2 on silica-supported nickel and Ni-Cu catalysts, /. Catal., 139, 513,1993. 

Piao, L. et al., Methane decomposition to carbon nanotubes and hydrogen on an alumina supported nickel aerogel catalyst, Catal. Today, 74,145, 2002. 

Carbon-Supported Nickel-Based Nanoparticles under Superheated Liquid-Film Conditions.452... 

The feasibility of carbon-supported nickel-based catalysts as the alternative to the platinum catalyst is studied in this chapter. Carbon-supported nickel (Ni/C, 10 wt-metal% [12]), ruthenium (Ru/C, 10 wt-metal% [12]), and nickel-ruthenium composite (Ni-Ru/C, 10 wt-metal%, mixed molar ratio of Ni/Ru 0.25,1,4, 8, and 16 [12]) catalysts were prepared similarly by the impregnation method. Granular powders of the activated carbon without the base pretreatment were stirred with the NiCl2, RuC13, and NiCl2-RuCl3 aqueous solutions at room temperature for 24 h, respectively. Reduction and washing were carried out in the same way as done for the Pt/C catalyst. Finally, these nickel-based catalysts were evacuated at 70°C for 10 h. 

Corbella, B.M. et al., Performance in a fixed-bed reactor of titania-supported nickel oxide as oxygen carriers for the chemical-looping combustion of methane in multicycle tests, I EC Res., 45(1), 157, 2006. 

Aniline is to be hydrogenated to cyclohexylamine in a suspended-particle agitated-tank reactor at 403 K (130°C) at which temperature the value of k is 90 s 1. The diameter dp of the supported nickel catalyst particles will be 0.1 mm and the effective diffusivity De for hydrogen when the pores of the particle are filled with aniline is 1.9 x 10 9 m2/s. 

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