GB799871A - Hydrogenation catalysts and process - Google Patents

Abstract

Organic nitro compounds are reduced to amino compounds in the presence of a hydrogenation catalyst comprising 0.1 to 10 per cent by weight of platinum and/or palladium deposited on the surface of an oleophilic carbon support having an oil absorption factor of at least about 200 (see Group III). In examples: (a) an aqueous solution of 2,4-dinitrotoluene is reduced with hydrogen under pressure to 2,4-diaminotoluene in the presence of a palladium catalyst; (b) nitrobenzene is reduced at 140-160 DEG C. and a hydrogen pressure of 200-1000 p.s.i.g. to form aniline in the presence of a palladium or palladium-iron catalyst; (c) 2,6-dinitrotoluene is reduced by hydrogen to 2,6-diaminotoluene, using a water slurry of palladium-iron catalyst; (d) 2-nitropropane is reduced to 2-aminopropane at 75 DEG C. under hydrogen pressure of 500 p.s.i.g. in the presence of an aqueous slurry of palladium-iron catalyst; (e) nitrobenzene is reduced to aniline at above 170 DEG C. at a hydrogen pressure of 250 p.s.i.g. in the presence of a palladium-iron catalyst, the reaction mixture being maintained water-free; (f) nitrocyclohexane is reduced by hydrogen to cyclohexylamine at 70 DEG C. and 500 p.s.i.g. pressure in the presence of platinum-palladium-iron catalyst; (g) nitrocyclohexane is reduced by hydrogen to cyclohexylamine and cyclohexanone oxime at 125 DEG C. and 250 p.s.i.g. pressure in the presence of a palladium-iron catalyst; (h) 2,4-dinitrotoluene is reduced to 2,4-diaminotoluene at 125-150 DEG C. and a hydrogen pressure of 400 p.s.i.g. in the presence of a palladium-iron catalyst; (i) nitrobenzene is reduced by hydrogen to a mixture of p-aminophenol and aniline at 100 DEG C. in the presence of a platinum catalyst, C-cetyl betaine, and sulphuric acid; (j) trinitrotoluene is reduced with hydrogen at 25-30 DEG C. in the presence of a platinum-palladium-iron catalyst to form triaminotoluene. Other reductions referred to are b -nitronaphthalene to b -aminonaphthalene, p-nitroanisole to p-anisidine, the sodium salt of dinitrostilbene disulphonic acid to the corresponding diaminostilbene compound, the sodium salt of p-nitrobenzoic acid to p-aminobenzoic acid, and 5-nitroquinoline in methanol to 5-aminoquinoline.ALSO:A hydrogenation catalyst comprises 0.1 to 10 per cent by weight of platinum and/or palladium deposited on the surface of an oleophilic carbon support having an oil absorption factor of at least about 200. The catalyst may be activated with minor amounts of an oxide, hydroxide, or carbonate of iron, nickel, cobalt, magnesium, aluminium, manganese, chromium, vanadium or tungsten, or fluorides of boron and/or silicon. The carbon support is preferably non-porous, with a surface area of 20-100 square meters per gm.; acetylene black is suitable. In examples of the preparation of the catalyst, (a) a solution of sodium bicarbonate is added to an aqueous slurry of acetylene black, followed by a solution of palladium chloride or chloroplatinic acid; the mixture is heated to 95 DEG C., reduced with formaldehyde solution, cooled, filtered, and washed; (b) acetylene black, sodium bicarbonate, platinous potassium chloride, and water are stirred at 95 DEG C., and the paste is filtered and reduced with hydrogen; (c) a solution of ferric chloride is added to an aqueous suspension of acetylene black, followed by a sodium carbonate solution to precipitate basic iron carbonate; sodium bicarbonate solution and palladium chloride solution are then added, and the mixture heated and reduced with formaldehyde; the ferric chloride and sodium carbonate solutions may be replaced by solutions of magnesium sulphate and sodium hydroxide to form a magnesium-containing catalyst; (d) ferric chloride solution and sodium bicarbonate solution are mixed to precipitate basic ferric carbonate and then a mixture of palladium chloride solution and sodium bicarbonate solution is added, followed by acetylene black; (e) sodium bicarbonate is added to a suspension of acetylene black, followed by solutions of palladium chloride and ferric chloride; (b) a solution containing palladium chloride and ferrous chloride is added to a mixture of acetylene black, sodium bicarbonate, and water; (g) palladium chloride is added to a solution of sodium chloride and stirred to form a chloropalladite solution; water, ferric chloride, and acetylene black are then added, followed by sodium bicarbonate; (h) acetylene black is stirred with sodium bicarbonate solution, and a solution of ferric or ferrous chloride added, followed by a solution of palladium chloride and chloroplatinic acid; (i) palladium chloride and chloroplatinic acid are added to a sodium chloride solution, followed by ferric chloride solution and carbon black; sodium bicarbonate is then added. Catalyst containing a smaller amount of active metal may be prepared by dilution of a concentrate with more of the carrier. Reducing agents other than formaldehyde and hydrogen which may be used are glucose, hydrazine, alcohol, and glycerine. The catalysts may be used in the reduction of organic nitro compounds to amino compounds (see Group IV (b)).