Raney iron catalyst

Ethylamines. Mono-, di-, and triethylamines, produced by catalytic reaction of ethanol with ammonia (330), are a significant outlet for ethanol. The vapor-phase continuous process takes place at 1.38 MPa (13.6 atm) and 150—220°C over a nickel catalyst supported on alumina, siUca, or sihca—alumina. In this reductive amination under a hydrogen atmosphere, the ratio of the mono-, di-, and triethylamine product can be controlled by recycling the unwanted products. Other catalysts used include phosphoric acid and derivatives, copper and iron chlorides, sulfates, and oxides in the presence of acids or alkaline salts (331). Piperidine can be ethylated with ethanol in the presence of Raney nickel catalyst at 200°C and 10.3 MPa (102 atm), to give W-ethylpiperidine [766-09-6] (332). 

In addition to the Raney nickel catalysts, Raney catalysts derived from iron, cobalt, and copper have been examined for their action on pyridine. At the boiling point of pyridine, degassed Raney iron gave only a very small yield of 2,2 -bipyridine but the activity of iron in this reaction is doubtful as the catalyst was subsequently found to contain 1.44% of nickel. Traces of 2,2 -bipyridine (detected spectroscopically) were formed from pyridine and a degassed, Raney cobalt catalyst but several Raney copper catalysts failed to produce detectable quantities of 2,2 -bipyridine following heating with pyridine. 

Table III. Iron and Carbon Content of Raney Nickel Catalyst Grids after Experiment HGR-10...

A third way to increase both the active surface area and the number of oxygenated species at the electrode surface is to prepare alloy particles or deposits and then to dissolve the non-noble metal component. This technique, which is similar to that used to prepare Raney-type catalysts, yields very high surface area electrodes and hence some improvements in the electrocatalytic activities compared with those of pure platinum. However, it is always difficult to be sure whether the mechanism of enhancment of the activities is due to this effect or the possible presence of remaining traces of the dissolved metal. Results with PtyCr and PtSFe were encouraging, although the effect of iron is still under discussion. From studies in a recent work on the behavior of R-Fe particles for methanol electrooxidation, it was concluded that the electrocatalytic effect is due to the Fe alloyed to platinum. ... 

The Raney nickel process applied to alloys of aluminum with other metals produces Raney iron, Raney cobalt, Raney copper and Raney zinc, respectively. These catalysts are used very rarely and for special purposes only. 

Raney-nickel catalysts are barely sensitive to catalyst poisoning (as are Pt-activated cathodes), e.g., by iron deposition, but they deteriorate due to loss of active inner surface because of slow recrystallization—which unavoidably leads to surface losses of 50% and more over a period of 2 years. A further loss mechanism is oxidation of the highly dispersed, reactive Raney nickel by reaction with water (Ni + 2H20 — Ni(OH)2 + 02) under depolarized condition, that is, during off times in contact with the hot electrolyte after complete release of the hydrogen stored in the pores by diffusion of the dissolved gas into the electrolyte. 

It is well known, even from old literature data (ref. 1) that the presence of metal promotors like molybdenum and chromium in Raney-nickel catalysts increases their activity in hydrogenation reactions. Recently Court et al (ref. 2) reported that Mo, Or and Fe-promoted Raney-nickel catalysts are more active for glucose hydrogenation than unpromoted catalysts. However the effects of metal promotors on the catalytic activity after repeated recycling of the catalyst have not been studied so far. Indeed, catalysts used in industrial operation are recycled many times, stability is then an essential criterion for their selection. From a more fundamental standpoint, the various causes of Raney-nickel deactivation have not been established. This work was intended to address two essential questions pertinent to the stability of Raney-nickel in glucose hydrogenation namely what are the respective activity losses experienced by unpromoted or by molybdenum, chromium and iron-promoted catalysts after recycling and what are the causes for their deactivation ... 

Other Raney catalysts have been prepared. Raney cobalt has been described by several authors (28,29). The active cobalt has been claimed to be especially suitable for the reduction of nitriles. The preparation of an active copper has been described by Faucounau (30). Paul and Hilly (31) have described the preparation of Raney iron. It is claimed that Raney iron reduces acetylenic bonds to ethylenic bonds with no further hydrogenation occurring. 

Iron catalysts have found only limited use in usual hydrogenations, although they play industrially important roles in the ammonia synthesis and Fischer-Tropsch process. Iron catalysts have been reported to be selective for the hydrogenation of alkynes to alkenes at elevated temperatures and pressures. Examples of the use of Raney Fe, Fe from Fe(CO)5, and Urushibara Fe are seen in eqs. 4.27,4.28, and 4.29, respectively. 

Haloanilines are obtained from halonitrobenzenes preferably by the iron-acid reduction procedure. Nuclear halogenation occurs during the reduction of nitrobenzene by stannous chloride in the presence of acetic anhydride a quantitative yield of p-chloroacetanilide is obtained. Hydrogenation of halonitrobenzenes over Raney nickel catalyst is possible provided that the temperature is kept below 150°, at which point... 

Incorporation of copper chloride in about 10% of the molar quantity of nickel before the borohydride reduction step further improved the selectivity of the Ni(B) catalysts. Copper improves the selectivity of Raney nickel catalysts in phenylacetylene semihydrogenation but not to the extent obtained using the copper-modified Ni(B) catalysts. The Cu-Ni(B) catalysts were more selective than the Cu(B) catalysts prepared by the borohydride reduction of copper chloride. Adding zinc or iron salts to a Ni(B) catalyst had only a slight effect on phenylacetylene semihydrogenation selectivity. ... 

A special type of catalyst which is typified by Raney Nickel is prepared by leaching out one component from a binary alloy leaving a skeletal structure of the desired catalyst. Raney Nickel itself is made by leaching out aluminium from an aluminium-nickel alloy with sodium hydroxide. Cobalt and iron catalysts have also been prepared in this manner. 

Hydrogenation of Dinitrotoluene to Toluenediamine. The hydrogenation of the dinitrotoluene mixture to toluenediamines is once again a standard process in aromatic synthesis. This reaction can be carried out with iron and aqueous hydrochloric acid like the reduction of nitrobenzene, but catalytic hydrogenation is preferred (e.g., in methanol with a Raney nickel catalyst at about 100°C and over 50 bars, or with palladium catalysts). 

By another procedure palladium-charcoal catalysts are used with iron(n) sulfate.133 Use of Raney nickel catalysts generally leads to hydrogenolysis of the N-N bond, but hydrogenation of nitrosamines with Raney nickel is nevertheless possible if the nitrosamine is stirred for an hour with the catalyst at atmospheric pressure and the hydrogen is admitted later.134... 

The reduction of 6-chloro-2(IH)-hydroxyquinoxaline-4-oxides can be completed by chemical reduction or catalytic hydrogenation. The successful chemical reduction has been reported using triphenylphosphine alone or in conjunction with iron, zinc, tin, sodium arsenite, ammonium sulfide, or sodium dithionite under alkaline conditions. This route is fairly expensive and gives low yields, large aqueous wastes and product isolation difficulties. A similarly expensive process employs hydrazine in the presence of Raney nickel catalyst in alkaline conditions. The reported yields range from 88 to 96%. Additional work with Raney nickel uses very low pressures of hydrogen in place of hydrazine. The yields are comparable. 

Raney iron and palladium on strontium carbonate also have been used as catalysts in reducing certain acetylenes to olefins. 

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