Nickel powder catalyst

Nickel sulfide, NiS, can be prepared by the fusion of nickel powder with molten sulfur or by precipitation usiag hydrogen sulfide treatment of a buffered solution of a nickel(II) salt. The behavior of nickel sulfides ia the pure state and ia mixtures with other sulfides is of iaterest ia the recovery of nickel from ores, ia the high temperature sulfide corrosion of nickel alloys, and ia the behavior of nickel-containing catalysts. 

Nickel plays a role in the Reppe polymeriza tion of acetylene where nickel salts act as catalysts to form cyclooctatetraene (62) the reduction of nickel haUdes by sodium cyclopentadienide to form nickelocene [1271 -28-9] (63) the synthesis of cyclododecatrienenickel [39330-67-1] (64) and formation from elemental nickel powder and other reagents of nickel(0) complexes that serve as catalysts for oligomerization and hydrocyanation reactions (65). 

Recently we found that freshly prepared nickel powder is an efficient hydrosilation catalyst when continuously irradiated(49). 

A significant cost advantage of alkaline fuel cells is that both anode and cathode reactions can be effectively catalyzed with nonprecious, relatively inexpensive metals. To date, most low cost catalyst development work has been directed towards Raney nickel powders for anodes and silver-based powders for cathodes. The essential characteristics of the catalyst structure are high electronic conductivity and stability (mechanical, chemical, and electrochemical). 

Combustion tests carried out for a rocket motor demonstrate a typical T combustion instability. Double-base propellants composed of NC-NG propellants with and without a catalyst (1 % nickel powder) were burned. Detailed chemical compositions of both propellants are given in Section 6.4.6 and the burning rate characteristics are shown in Fig. 6.29. The addition of nickel is seen to have no effect on burning rate and the pressure exponent is n = 0.70 for both propellants. 

The use of additional substances to increase the activity of a catalyst is a well known phenomenon. Hydrogen chloride or traces of water are known to promote aluminum chloride catalyzed reactions. In the same way the reaction of isoparaffins with olefins has been shown to be catalyzed by boron trifluoride in the presence of nickel powder and with water as the promoter (Ipatieff and Grosse, 76). Hydrogen fluoride can take the place of the water and thus serve as the promoter. 

In the last few decades, the study of adsorption phenomena at nickel electrodes by a radiotracer method has been the subject of several studies (see [34-40] and literature cited therein). M ost of these studies were carried out at smooth electrodes however, in some cases, nickel powder and Raney-nickel catalysts were used. 

Microwave heating was also used to induce catalytic oligomerization of methane to afford C2-C4 hydrocarbons.571 Changing the catalysts and the applied power and the use of diluent gas (He) allowed significant alteration of product selectivities. Selectivity to benzene over nickel powder or activated carbon was 24 and 33%, respectively. 

As a rule, synthetic chemists will consider only those new reactions and catalysts for preparative purposes where the enantioselectivity reaches a certain degree (e.g. >80%) and where both the catalyst and the technology are readily available. For heterogeneous catalysts this is not always the case because the relevant catalyst parameters are often unknown. It is therefore of interest that two types of modified Nickel catalysts are now commercially available a Raney nickel/tartrate/NaBr from Degussa [64] and a nickel powder/tartrate/NaBr from Heraeus [65, 66]. It was also demonstrated that commercial Pt catalysts are suitable for the enantioselective hydrogenation of a-ketoesters [30, 31]. With some catalytic experience, both systems are quite easy to handle and give reproducible results. 

Catalysts (coni.) copper, for reaction of methyl chloride with silicon, 3 56 iron, for preparation of sodium amide, 2 133 nickel powder, 5 197 silica gel for, or for supports,... 

Photocatalytic Decomposition of Water into H2 and O2 over NiO-SrTiCh Powder. 1. Structure of the Catalyst. Nickel metal also found at the interface of NiO and SrTiCh. See also Entries 7,15 and 16. 404... 

The hydrogenations of allenes may proceed through allylic intermediates. The distribution of products formed during the reaction of 1,2-butadiene with D2 depends on the particular nickel catalyst used. Reactions on the more selective catalysts (Ni powder, Ni/Si02) are presumed to proceed mainly via vinyl intermediates reactions on the less selective catalysts (Ni/AhOs) proceed via allylic intermediates (equation 34). A similar dichotomy of mechanisms is assumed to characterize reactions on Pd. 

An electronic effect was also used to explain the difference in 1,3-butadiene hydrogenation selectivity observed over various types of nickel catalysts such as Ni(B), Raney nickel, nickel powder from the decomposition of nickel formate, Ni(P), and Ni(S). As discussed in Chapter 12, chemical shifts in XPS binding energies (Aq) for the various nickel species were compared with that of the decomposed nickel catalyst to determine the extent of 1-butene formation as related to the electron density on the metal. The higher the electron density, the more 1-butene formation was favored. 

Six grams of 42% nickel, 58 % aluminum catalyst powder, all of which would pass a 150 mesh screen, was mechanically mixed in o porcelain mortar with ten grams of the elemental nickel powder for fifteen minutes. The calculated nickel content of the nickel aluminum powder was 2.52 grams, so that the added nickel was practically four times the nickel contained in the nickel aluminum alloy. The added nickel was not combined chemically with the aluminum, but was thoroughly mixed mechanically with the nickel aluminum powder. The six grams of 42% nickel, 58% aluminum powder had a calculated content of 3.48 grams of aluminum. Seven grams of 76% flake sodium hydroxide were used to make a 25% sodium hydroxide water solution. Potassium hydroxide or other caustic alkali solution may be used in place of sodium hydroxide and nickel carbonyl powder may be used in place of elemental nickel powder. Also, a nickel silicon alloy or an alloy of nickel with another alkali soluble metal may be used in place of the nickel aluminum alloy. 

When a samples of iron-nickel powder was heated in the presence of a CO/H2 mixture the maximum catalytic activity in terms of the conversion of CO to solid carbon and CO2 was found to occur at temperatures between 500 to 600°C. On continued heating to higher temperatures a precipitous drop in the activity of the catalyst towards the formation of these two produets and at 725°C almost complete deactivation was observed. This behavior appeared to be most pronounced for the bimetallie powders containing a relatively high fraction of nickel. If, however, the sample temperature was simply lowered from 750° to 600°C, the performance of the catalyst was restored to its original high level. 

Hydrogenation of 2-phenylpyridine (7) (5 mmol.) over activated I-H4 (3.5 g) was also carried out in a 50ml autoclave at several temperatures for 3-6 h. An elevated temperature, such as 240°C, was needed to obtain higher conversion rates. The reaction at 240°C for 6 h yielded 2-cyclo-hexylpyridine (8) (53 %) as a major product along with substantial 2-phenylpiperidine (9) (23 %). It was reported that hydrogenation of 7 with H2 over platinum or nickel catalysts mainly yields 9. These results indicate that the catalytic nature of 1 is different from that of nickel powder [14,15]. 

Some preliminary runs using nickel carbonate in the presence of hydrogen have also yielded promising results. In these runs the nickel carbonate was reduced in situ to finely divided nickel which presumably functioned as the catalyst. Commercially available nickel powders did not appear to be as effective as Raney nickel or nickel produced in situ. 

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