Raney nickel catalysts modification

The modification of the Ni Al alloy by addition of molybdenum or chromium has a significant effect on the properties of the Raney nickel catalyst in the reaction of hydrogenation of valeronitrile. In the case of molybdenum, the catalytic properties may be correlated to the physico-chemical characteristics of the catalysts. Chromium is an effective promoter for initial activity and for selectivity. The mechanism for promotion of chromium in Raney nickel is not known exactly. 

Bipyridine has been prepared by the action of ferric chloride,8,9 iodine,10 or a nickel-alumina catalyst10 on pyridine at temperatures ranging from 300° to 400°. It has also been obtained from the reaction of 2-bromopyridine and copper.11 The present procedure is a modification of a previously published, general method.3 The W7-J nickel catalyst was developed from the description of the W7 Raney nickel catalyst of Billica and Adkins.12... 

Raney nickel catalyst was modified with 0.5 wt % V or Mg to increase the selectivity to secondary amines in the alkylation of ammonia with n-propanol or i-butanol. Due to the modification selectivities around 70-80 % were obtained at 90-95 % conversions. The mixed secondary alkylamine, N-ethyl-N-n-butylamine was prepared from ethylamine and n-butanol on a commercial Cu0-Zn0-Al203 catalyst. The highest yield of EtNHn-Bu around 76 % was obtained at 190 °C and EtNH2/n-BuOH molar ratio 5 or above. 

In this paper the effect of modification of Raney nickel catalyst with V or Mg on the selectivity of secondary amine in the alkylation of ammonia with n-propanol and i-butanol is studied. In addition, we report the preparation of N-ethyl-N-n-butylamine over a commercial CuO-ZnO-Al203 catalyst. The effect of reaction temperature and ammonia or primary amine to alcohol molar ratio on the selectivities and yields of symmetrical and mixed secondary amines will be discussed. 

Conversions, selectivities and yield of i-Bu2NH obtained in the alkylation of ammonia with i-butanol are summarized in Table 2. The modification of the Raney nickel catalyst with vanadium resulted in 4-5 % increase in the selectivity of secondary and primary amine, whereas the conversion only slightly decreased (compare exp.s N°1 and N°2 in Table 2.). 

The modification of the Raney nickel with low Mo amount (x = 0.05 or 0.1) lead to catalysts which had roughly the same kinetic behaviour as the undoped. Further introduction of molybdenum in the Ni A13 alloy had a substantial negative effect on the properties of the catalysts, with a drop in the... 

The observation that no hydrogenolysis of the C-X bond takes place as long as either nitro compounds or reaction intermediates are present can be explained by the strong adsorption of these molecules, thereby preventing the interaction of the C-Cl bond with the catalyst. The mode of action of the modifiers is less clear. It could be due to a modification of the catalytic properties of the Raney nickel or also to a competitive adsorption between the effective modifiers and the... 

Among the other metal catalysts for hydrogen oxidation, the Raney nickel deposited on the surface of graphite is widely known [10, 13], The modification of Raney nickel with such metals like Fe, Cr, Cu, La, Ti has been proposed [11] with the aim to increase its effectiveness. The effectiveness of the doping metals follows the series Cr>La>Ti>Cu>Fe. 

Raney nickel is very probably the most commonly used nickel catalyst. It is also the most versatile of catalysts. In one or other of its several modifications it has been used for hydrogenations over a wide range of pressures varying from high to subatmospheric, for desulfuration, for dehalogenation, and for very many other reactions. 

Systematic studies on the enantioselective heterogeneous catalytic hydrogenation of carbonyl compounds were carried out by Izumi using Raney nickel modified with various chiral reagents. Hydroxy acids or amino acids were used for the modification of the nickel catalyst, and (-i-)-tartaric acid (2R,3R)... 

The skeletal nickel catalyst (Ni) was prepared by leaching a 50 wt% Ni-Al alloy with 20 wt% Na0H-H20 solution at 50 °C as desrcibed elsewhere [14]. Modification of Raney Ni catalyst with... 

Note the particularly mild reaction conditions and the fact that the reaction depicted by Eq. (6) progresses without cleavage of the allylic hydroxyl group. These copper-modified nickel catalysts were found to be more selective than the analogous Cu(B) formulations derived from borohydride reduction of copper chloride [17]. Copper modification of Raney nickel has also been shown to benefit the selectivity of phenylacetylene hydrogenation, but not to the same extent as the Cu-Ni(B) catalyst. 

The usual conditions of catalytic hydrogenation can be applied, with certain modifications, for the saturation of carbon-carbon double and triple bonds. Platinum and Raney nickel are the usual catalysts described. It is important that catalysts used for deuteration shall be pretreated with deuterium noble-... 

Modification of deuterated Raney nickel with L-glutamic acid also results in lower deuterium contents in the products but does not drastically alter deuterium distributions (experiments D28B and D28C). In contrast to other work on C=C double bonds [12], little asymmetric induction was obtained. For example, the deuteriumation of III over MRNiD(A) and IV over MRNiD(B) produced products with optical purities of 0.4 and 1.1% respectively. Low enantioselectivi-ties from these catalysts might result from processes associated with extensive exchange. 

A recent modification in the use of Raney nickel may greatly enhance its utility. Industrial use of the standard procedure has been limited by the necessity to use such large quantities of the very expensive Raney nickel. It now appears that the use of the nickel-aluminium alloy itself in formic acid leads to very efficient desulphurizations with Ni/S ratios of only 0 2. High proportions of the aluminium seem to give the best results, apparently because of the ability of the aluminium to regenerate the active nickel catalyst. Similar results were obtained using nickel or cobalt salts in the presence of auxiliary metals such as aluminium or iron. 

We have utilized this reaction path with some modifications (scheme 3). The diketene addition to 4-chloro-2-nitroaniline occurred spontaneously at room temperature with traces of 4-dimethylaminopyridine. Cyclisation and reduction were then completed in a one-pot procedure in a mixture of isopropanol and water. This allow the use of only 2.2 equivalents of sodium hydroxide instead of 5 to 6 in water and to control the temperature of the cyclisation at "65 C. Various catalysts, particularly Raney nickel or palladium on charcoal (8) were known to be efficient for the hydrogenation of the N-oxide. Eventual overreduction to the 3,4-dihydro-2(lH)-quinoxalinone could be smoothly compensated by reoxidising with hydrogen peroxide or air (9). 

Similarly to the zeolite modifications with Fe + and Co +, Ni-zeolites produced via SSIE were also tested as catalysts for NO decomposition and/or reduction. Varga et al. [ 114,121 ] investigated by IR the adsorption behavior and transformation of NO on the resulting Ni-ZSM-5 and showed that this material is indeed a good catalyst for NO decomposition. In their study on selective catalytic reduction of NO by Raney-nickel-supported Cu-ZSM-5, Ma et al. [187] observed that the NO conversion decreased only at low temperatures but remained constant or even improved at high temperatures. The authors ascribed this effect to a migration of Ni cations into the zeolite matrix via SSIE that led to a stabilization of the lattice. 

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