Nickel of Raney

The nickel of Raney is a solid Catalyseur used in many processes Industrie ls consisted of a fine gray Poudre of a Alliage of Nickel and Aluminum. It was developed in 1926 by the American Engineer Murray Raney like replacement solution with catalysts used at that time in industry for the Hydrogénation of the plant oils. More recently, it is used like heterogeneous Catalyseur for a large variety of reactions of the Organic chemistry, generally for hydrogenations. In 1939, Leopold Ruzicka and Adolph Butenandt obtain the Nobel Prize of chemistry to have synthesized male hormones starting from cholesterol by using the nickel of Raney like catalyst.

The nickel of Raney is produced by treating a piece of alloy nickel-aluminum by the concentrated soda . During this treatment called “activation”, the major part of the aluminum of alloy is dissolved. The porous structure which results from it has a very important Surface specific, which contributes to its effectiveness in catalysis. The catalyst generally consists of 85 % of nickel (in Masse), which corresponds roughly to two Atome S of nickel for an aluminum atom. The aluminum which is not dissolved assistance to preserve the porous structure of catalyst on a macroscopic scale.

Even if name “Raney” is most current, it is a registered trademark of W.R. Grace and Company, and only that produced by division Grace Davison can bear this name. For catalysts having of the physical properties and chemical similar to those of the nickel of Raney, the terms most usually used are names coloured such as “ spongy nickel ” or “ skeletal nickel ” qui illustrates very well the structure of this solid.

Development of catalyst

Murray Raney obtained its diploma for the occupation of engineer in Mécanique of the Université of Kentucky in 1909. In 1915, he is engaged by the company Lookout Oil and Refining Company with the Tennessee, company in which he is responsible for the installation of the cells of electrolyzes intended for the production of hydrogen for the hydrogenation of plant oils. At that time, the catalyst used in industry for this hydrogenation is containing Oxide nickel II. Raney thinking that it is possible to use a more effective catalyst, it starts to undertake independent research starting from 1921 whole while continuing to work for Lookout Oil. In 1924, it produces an alloy Nickel - Silicium in equal proportions, which proves after treatment soda five times more effective than best catalyst used then for the hydrogenation of the seed oil of Coton. In December 1925, it deposits a Brevet for this discovery.

Just after this first discovered, Raney manufactures a new alloy nickel-aluminum in equal proportions, while following the same procedure as that used for the alloy nickel-silicon, in particular the treatment soda. The tests carried out show whereas this new catalyst is even more effective, and Raney fills a request of patent filling in 1926.

Manufacture

Manufacture of alloy

The alloy is prepared industrially by fusion nickel (in the case of the nickel of Raney, but it is possible to also prepare catalysts of the Raney type from others metals like the Fer or the Cuivre) and of aluminum in a Creuset. The alloy still in fusion undergoes a Trempe. The solid mixture obtained is then finely crushed. The powder can then be filtered to obtain a range of sizes of particles controlled, according to the application for which the catalyst is manufactured.

The initial composition of alloy is a big factor because hardening produces many different phases nickel-aluminum which have distinct properties of leaching, which has an important influence on the porosity of catalyst at the end of the process. The alloys most usually used in industry contain at the beginning the same quantity of nickel as of aluminum (in mass), which corresponds besides to the ratio used by Murray Raney during the development of catalyst.

During the stage of hardening, minor amounts of the third metal, like the Zinc or the Zirconium, can be added. This addition makes it possible to increase the catalytic capacity, so that the third metal “Promoteur is generally called”. This decrease is due to structural rearrangements within alloy, similar to the effects of a Frittage: the various particles constituting alloy start to adhere the ones to the others when the temperature increases, and it results a reduction from it from the porosity of the structure.

Before its storage, the catalyst can be washed with Eau distilled with the room temperature so as to eliminate the possible traces from sodium aluminate. It is preferable to use water deoxygenized for storage so as to avoid the Oxydation catalyst. This one accelerates its ageing indeed and tends to decrease its catalytic capacity. It inter alia is used for the reduction of organic compounds with multiple connections like the Alcyne S, the Alcène S, the nitriles, the Diène S, the aromatic compounds or the Carbonyle S. In addition, the nickel of Raney makes it possible to reduce bonds heteroatom-heteroatom as in the grouping nitro and the Nitrosamine S. It is also usable for the reducing Alkylation of the amine S or the Amination of the alcohols.

A practical example of the use of the nickel of Raney in industry is shown in the following reaction, during which the Benzène is tiny room in Cyclohexane. The reduction of the aromatic structure of benzene is extremely difficult to implement without catalyst, but can be realized without major difficulty by using the nickel of Raney. Other heterogeneous catalysts can be also used for this reaction, like in particular those using of the elements of the group of the Platine, but they are much more expensive to produce. After this reaction of reduction, cyclohexane can be used for example for the synthesis of Adipic acid, a precursor used in the manufacture of the Polyamide S like the Nylon.

During the reduction of a double connection Carbon - Carbon with use of nickel of Raney, the addition of the two hydrogen atoms is done in a geometry Syn. It makes it possible for example to reduce the Thioacétal S in Hydrocarbure S.

Appendices

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