US3036909A - Process of preparing nickel-aluminum or cobalt-aluminum alloys starting from raney catalysts - Google Patents

Description

United States Patent Gfitice Pgemd M33222? 3,036,909 PROCESS OF PREPARING NICKEL-ALUMINUM R COBALT-ALUMINUM ALLOYS STARTING FROM RANEY CATALYSTS Henri J. H. Simon, Gelecn, Netherlands, assignor to Stamicarbon N.V., Heerlen, Netherlands N0 Drawing. Filed Feb. 9, 1959, Ser. No. 791,817 Claims priority, application Netherlands Feb. 14, 1058 1 Claim. (Cl. '75-2'7) The present invention relates to a process of preparing nickelaaluminum or cobalt-aluminum alloys starting from Raney catalysts. By Raney catalysts are here to be understood both Raney nickel and Raney cobalt cata lysts, powdery as well as in lumps (the so-called forarninate catalysts).

When such a catalyst is spent, i.e. when the catalyst has been used so long that its decreased activity makes further use or regeneration, e.g. by treatment with an alkali, ineffective, it is advantageous to recover the nickel or cobalt contained therein and convert the same into nickel-aluminum or cobalt-aluminum alloys from which in active Raney catalyst may then be prepared again by treatment with alkali. US. Patent No. 2,139,602 describes a process for effecting the foregoing by oxidizing the spent Raney catalyst with air to obtain the corre sponding oxide, and subsequently subjecting the oxidized catalyst, according to the thermite process, to the action of aluminum powder, to obtain an aluminum alloy. The latter may then be used to prepare an active Raney catalyst in the well-known manner mentioned above, i.e. by treatment with alkali.

However, the process of U.S. Patent 2,139,602 has the drawback that the thermite treatment of the resulting oxide with aluminum powder does not proceed very satisfactorily. In some cases the reaction fails to start and in others the alumina slag formed in the thermite process is difficult to separate off, particularly if metallic nickel or cobalt, or an aluminum alloy of these substances, has been added to the mixture. This addition of metallic nickel or cobalt is desirable from time to time, because the extra quantity of alloy formed from the added material compensates for Raney catalyst losses which are unavoidable in a large-scale hydrogenation process. An additional disadvantage of said prior process is that nickel oxide or cobalt oxide which is formed under such oxidation conditions that the thermite treatment fails to produce satisfactory results, cannot thereafter be brought into a state in which it can be successfully treated in the thermite process even if a lengthy oxidation treatment is applied, e.g. heating in air at 600 C. for 24 hours.

The principal object of the present invention is to provide a novel process of carrying out oxidation of the spent Raney catalyst. Another object of the invention is the provision of a process whereby the abovementioned prior art difficulties are avoided. A further object of the invention is to provide improvements in the process of U.S. Patent 2,139,602. A more specific object of the invention is the provision of a process for preparing nickelalurninum or cobalt-aluminum alloys from spent Raney catalysts by oxidation of the catalyst and subsequent treatment with aluminum in the thermite process, the oxidation being carried out in such a way that the resulting oxide, with or without the addition of nickel or cobalt, can be subjected to the thermite treatment with highly desirable results. Other objects will also be apparent herein.

According to the present invention, the preparation of nickel-aluminum or cobalt-aluminum alloys from a Raney catalyst by oxidizing the Raney catalyst to nickel oxide or cobalt oxide, and subsequently treating the oxide with aluminum in the thermite process, is carried out in such a way that the oxidation step is performed, partially or completely, by adding a nitrate to the Raney catalyst, preferably in the presence of water, and heating the resulting mixture.

The presence of Water is advantageous, because it facilitates proper mixing of the nitrate and the catalyst. Adequate mixing is of particular importance if the reaction tends to proceed violently. The desired amount of water may be obtained either by using an aqueous suspension, paste or the like of the Raney catalyst or, for example, by adding the nitrate as an aqueous solution to the catalyst.

If desired, sufiicient nitrate may be used to effect the oxidation completely by means of the nitrate. In such event, addition of the nitrate and subsequent heating should be carried out with great caution. Preferably, however, the process is carried out in such a way that the oxidation is only partially carried out by heating with nitrate and is completed by the action of a gas containing oxygen, e.g. air.

Typically, the oxidation may be carried out as follows: An aqueous solution of nitrate is added, with stirring, to an aqueous suspension of spent Raney catalyst, and the mass is subsequently evaporated to dryness. This causes partial oxidation of the catalyst. Thereafter, the resulting dry powder is heated in air at, for example, 600 C. for some hours, typically 3 to 5 hours. In this way, all of the nickel or cobalt in the catalyst is converted into the corresponding oxide. This product is particularly suitable for further treatment in the therrnite process, even if metallic nickel or cobalt is added thereto.

Preferably, the process of the invention is carried out in such a way that the heating with nitrate takes place with simultaneous passage of air or other oxygen containing gas through the mass. As a result of this passage of gas through the mass, the oxidation reaction is brought about with a resulting substantial temperature rise. Prefera bly, care should be taken, by control of the air supply, to maintain the temperature no higher than 900 C., otherwise there is a danger that the catalyst particles might be sintered together. After cooling, an oxide is obtained which reacts exceedingly violently in the thermite process. This oxide is of such quality that metallic nickel or cobalt may without objection be added to the thermite mixture. An additional advantage of this preferred embodiment of the invention is that the heat needed to bring the nickel or the cobalt to a temperature at which the oxidation by means of molecular oxygen proceeds well, is produced by the reaction itself.

The invention may be carried out with any nitrate which does not leave undesirable metals in the alloy to be formed. Thus, it is possible to use such inorganic nitrates as aluminum nitrate, nickel nitrate, and cobalt nitrate. Use also may be made of alkali metal and alkaline earth metal nitrates, such as sodium, potassium and calcium nitrate. Preferably, however, the process of the invention is carried out with ammonium nitrate, as this compound does not leave foreign metals in the alloy to be formed and is readily available at low cost and in large quantities in a pure form.

The amount of nitrate, typically ammonium nitrate, utilized according to the invention may be varied but preferably amounts to more than 10% by weight of the spent Raney catalyst. However, smaller amounts may also be effectively used. Thus, in some cases, 5% by weight or less is effective to produce a mixture which can be subjected to the thermite process with good result. Generally, the use of nitrate in amounts greater than 50% by weight of the Raney catalyst does not produce any extra improvement. In some cases, the catalyst may advantageously be washed with a solution of nitrate prior to being oxidized to its oxide. After such washing less nitrate is needed for oxidizing the catalyst to obtain an oxide that can be successfully thermite-treated, while on addition of the nitrate a less violent reaction is produced.

The invention is further illustrated, but not limited, by the following examples.

Example 1 300 kg. of a Raney nickel paste which contains about 35% by weight of water and which has been used for hydrogenating phenol, is cautiously mixed in an open steel tank with 45 kg. of ammonium nitrate dissolved in 60 litres of water. The mass is then evaporated to dryness, during which evaporation no NO or N is formed. The dry powder is heated in air at 600 C. and maintained at this temperature for 4 hours. If desired, this heat treatment may be carried out at any temperature within the range of 500 to 900 C. for 1 to hours.

The resulting nickel oxide is cooled down and then thermite-treated in known manner (e.g. as described in US. Patent 2,139,602) by mixing with 80% by weight of aluminum. This mixture is ignited by means of a primer. The thermite reaction proceeds excellently, even after addition of 4% by weight of metallic nickel and 4% by Weight of aluminum. The resulting nickel-aluminum alloy may be satisfatcorily used to prepare new Raney catalyst by treatment with alkali, in known manner.

Example 2 kg. of a paste of spent Raney nickel containing about by weight of Water, which has been used for hydrogenating e-aminocapronitrile and has been washed with a solution of ammonium nitrate is mixed in a steel tank with 4.5 kg. of ammonium nitrate and further treated as described in Example 1. The result of the thermite process is the same as given in Example 1.

Example 3 With stirring, a solution of 4 kg. of nickel nitrate in 6 litres of water is added to 30 kg. of a paste of spent Raney nickel catalyst containing 35% of water and used for the hydrogenation of phenol. The mass is then treated as indicated in Example 1. The result of the thermite process is the same as described in Example 1.

Example 4 To 15 kg. of a paste of Raney nickel catalyst containing 35% by weight of water, which has been used for the hydrogenation of phenol, and is contained in a steel tank, there is added 3 kg. of ammonium nitrate in 6 litres of Water; this mixture is evaporated to dryness by heating it initially to about 150 C. while air is being fed into it through a feed conduit opening into the bottom of the tank and provided with a distributor head. After the evaporation is completed, the temperature rises quickly and by a proper control of the air supply and a proper mixing of the mass the temperature is maintained at about 800 C. After cooling, a nickel oxide is obtained which lends itself excellently to being treated in the thermite process. It is even possible to add large amounts of metallic nickel and additional aluminum (8 and 8% by weight, respectively) with satisfactory results.

Example 5 After having been washed with a solution of ammonium nitrate, 10 kg. of a paste of Raney nickel catalyst containing about 35 by Weight of water, which has been used for the hydrogenation of e-aminocapronitrile, is treated as described in Example 4. The result of the thermite process is the same as given in Example 4. In none of the experiments mentioned in the examples does formation of NO or N0 occur.

Having described the invention, what is claimed as new is:

In the preparation of an alloy selected from the group consisting of nickel-aluminum and cobalt-aluminum alloys from a Raney catalyst by oxidizing the catalyst to an oxide selected from the group consisting of nickel oxide and cobalt oxide and thereafter treating the resulting oxide with aluminum in the thermite process, the improvement which comprises carrying out said oxidation by mixing the catalyst with ammonium nitrate in the presence of water, evaporating the resulting mixture to dryness and thereafter heating the resulting dry powder while passing air therethrough at a temperature not exceeding 900 C., the amount of nitrate being between 10 and by weight of the catalyst.

Manhes Aug. 27, 1889 Raney Dec. 6, 1938