NL300533A - - Google Patents

Abstract

Unsymmetrical dialkylhybrazines are prepared by the reduction of dialkylnitrosamines in the liquid phase with hydrogen at a hydrogen pressure of below 50 atmospheres gauge and at a temperature between - 20 DEG C. and +50 DEG C. in a reaction medium rendered alkaline by the addition of an alkali metal hydroxide in sufficient quantityto give the medium a content of 0.001 to 5.0 moles of dissolved hydroxide per dm.3 of reaction medium or made ionic by adding thereto soluble metallic salts or alkaline earth metal hydroxide in a quantity of 0.001 to 5.0 moles of dissolved electrolyte per dm.3 of reaction medium, the reduction being effected in the presence of Raney nickel catalyst obtained by an attack of an aqueos solution of caustic alkali on a Ni-Al alloy or alloys, the ratio by weight of catalyst to dialkylnitrosamine being between 0.001 and 1.0 and the ratio by weight of catalyst to reaction medium being between 0.001 and 0.50. The catalyst may be dehydrogenated before use and if stored may be dipped into aqueous alkali metal hydroxide first prior to use.ALSO:Raney-Nickel catalyst is obtained by heating a Ni-Al alloy or alloys, preferably those which pass a sieve No. 26 AFNOR, at about 100 DEG C. with a 250 g/litre solution of sodium hydroxide in such quantity that the weight of dissolved sodium hydroxide is equal to the weight of alloys used, decanting, again treating the alloy or alloys with sodium hydroxide under identical conditions to the first treatment, discarding the sodium hydroxide solution and washing the alloy or alloys with water. The catalyst so obtained may be dehydrogenated by contacting the catalyst metal with an anode resistant to alkaline electrolyte and traversing the catalyst metal with an electric current of below 500 milli amperes/cm2 (see Patent No. 1,010,187) or by immersing the catalyst in an electrolytic cell and traversing it by an electric current without it being in contact with either of the electrodes (see Patent No. 1,007,174). Preferred Ni-Al alloys have the composition 40-55% by weight Ni; 60-38% Al, 0-1% Cu and 0-6% Fe and a specially preferred alloy has the composition 47.5% by weight Ni, 49% Al, 0.5% Cu and 3% Fe. Catalysts which have been stored may be dipped into aqueous alkali metal hydroxide just prior to use.