GB797483A - Improvements in or relating to catalytic hydrogenation of nitrosamines - Google Patents

Abstract

Hydrazines are produced by reacting a nitrosamine with hydrogen at a pressure above atmospheric and in the presence of particulate catalytic material comprising a Group 8 metal selected from palladium, platinum, rhodium, nickel, cobalt and iridium, said catalytic material having a specific surface area of at least 15 square metres per gram, said nitrosamine being of sufficiently high purity to thereby undergo reaction with hydrogen to form said hydrazine. Preferably a hydrogen pressure of between about 50 and 10,000 p.s.i.g. and a temperature of from about 20 DEG to 75 DEG C. will be employed. Palladium supported on carbon, alumina, silica, silica-alumina, or titania, is the preferred catalyst, but platinum employed as platinum oxide or platinum supported on carbon is nearly as effective. The nitrosamine starting materials may be produced by nitrosation of the corresponding secondary amines with nitric oxide as described in Specification 789,702. The nitrosamines may be dialkyl, diaryl, mixed alkylaryl or heterocyclicnitrosamines, or the nitrosamine may contain more than one nitroso group in which case the dihydrazine product can be obtained. The nitrosamine may also contain carboxyl, hydroxyl or ester groups. A list of suitable nitrosamines is given. The starting material may be purified by fractionation, solvent extraction, or recrystallization. It is preferred to fractionate the material in a column having at least four theoretical plates. The hydrogenation is preferably effected in an inert solvent such as water, hydrocarbons such as toluene, chlorinated hydrocarbons, or alcohols such as ethanol. In examples: 17 to 74 grams of nitrosamine is charged into a pressure vessel (either a Parr shaker bottle or a rocking autoclave) and agitated under various conditions of temperature and pressure, the catalyst being a supported catalyst comprising 5 per cent by weight of the metal. The starting materials and catalysts are as follows: dimethyl nitrosamine with platinum oxide, Raney cobalt, Raney nickel, palladium on carbon, platinum/carbon, rhodium/carbon, and palladium/calcium carbonate; diethylnitrosamine with palladium/carbon; nitrosopiperidine with palladium/carbon; diamylnitrosamine with palladium/carbon; dinitrosopiperazine with palladium carbon. Ruthenium and potassium perrhenate are shown to be inoperative as catalysts, and comparative examples in which the catalytic materials have a specific surface of below 15 square metres per gram are described. Example (49) describes a continuous process using a palladium-on-alumina catalyst which is supported in a layer of toluene which floats on a water layer in a stainless steel reactor; dimethylnitrosamina is continuously introduced at the top of the reactor, hydrogen at 300 p.s.i.g. is continuously introduced and the water layer containing the products of reaction, dimethylhydrazine, dimethylamine and ammonia is continuously removed.