Patent GB-718615-A (GB)
Title: Catalytic hydrogenation of aromatic nitro compounds to amines
IPC: B01J27/043
Filed: 1951-11-29
Abstract: Aromatic nitro compounds are hydrogenated in liquid or vapour phase to the corresponding amine, particularly nitrobenzene to aniline, by carrying out the reaction in the presence of a catalyst comprising nickel sulphide as the sole metal sulphide associated with activated or amorphous alumina.  The hydrogenation, preferably in the vapour phase, may be effected at 250-350 DEG  C., peak bed temperatures, however, rising to 400-450 DEG  C. 1 to 1 1/2 times the theoretical quantity of hydrogen is preferred corresponding to 4 1/2 to 15 mols. per mol. of nitrobenzene.  The catalyst may be employed as a fixed or fluidized bed and may be prepared by (a) impregnating active alumina with soluble thermally decomposable nickel salts; (b) precipitation or coprecipitation of nickel and aluminium hydroxide or (c) coignition of nickel and aluminium salts, the resulting product in each case, optionally after reduction with hydrogen, being sulphided with hydrogen sulphide or carbon disulphide.  The alumina may constitute from 2 to 90 per cent by weight of the catalyst, and, if the alumina does not act as such, additional carriers such as silica, clays, activated alumina, corundum or charcoal may be incorporated before sulphiding. Regeneration may be effected by removing organic material with air or oxygen at 300-500 DEG  C., followed by reduction with hydrogen at the same temperature (as in Specification 702,018). According to examples: (1) activated alumina is impregnated with nickel nitrate employing alternating reduced and atmospheric pressure to assist impregnation, heated to convert the nickel nitrate to oxide, sulphided with hydrogen sulphide and cooled and stored in an oxygen-free atmosphere.  9 mols. of hydrogen per mol. of nitrobenzene are passed over the catalyst at 300 DEG  C. in a converter as described in Specification 144,614, [Class 2 (iii)], at a rate of 300 grams of nitrobenzene per volume of catalyst per hour.  The aniline is recovered by condensation.  Regeneration is effected by passing air and steam over the catalyst at 400 DEG  C., followed by hydrogen and steam, and finally by pure hydrogen.  (2) As in (1) above except that an hourly rate of 1760 grams of nitrobenzene per litre of catalyst is employed.  (3) Activated alumina is impregnated with nickel acetate in aqueous acetic acid, the slurry saturated with hydrogen sulphide, mixed with ammonium hydroxide and resaturated. The catalyst is dried and ignited in hydrogen at 350 DEG  C; 10.2 mols. hydrogen/mol. nitrobenzene are passed over the catalyst at 300 DEG  C. at an hourly rate of 430 grams nitrobenzene per litre of catalyst.  (4) Ammonium carbonate is added to a mixed aluminium and nickel nitrate solution, the slurry dried and the resulting cake crushed.  The powder is sulphided at 330 DEG  C. and reduced at 345 DEG  C.  An hourly rate of 300 grams nitrobenzene/litre of catalyst is employed in a hydrogenation at 300 DEG  C.  (5) A slurry is prepared as in (4), filtered, washed and reslurried.  The aqueous mixture is heated to 100 DEG  C. for 18 hours, thereby forming a proportion of hydrated nickel aluminate.  The slurry is filtered and the solid dried, ignited and sulphided as before.  (6) A catalyst is prepared by coignition by replacing the activated alumina of (1) by "Alundum" and replacing 2-25 mol. per cent of the nickel nitrate by aluminium nitrate and treating the solid as in (1). Specification 599,252 also is referred to.ALSO:Aromatic nitro-compounds are hydrogenated in liquid or vapour phase to the corresponding amine, particularly nitrobenzene to aniline, by carrying out the reaction in the presence of a catalyst comprising nickel sulphide as the sole metal sulphide associated with activated or amorphous alumina.  The hydrogenation, preferably in the vapour phase, may be effected at 250-350 DEG C., peak bed temperatures however rising to 400-450 DEG C. One to 1 1/2 times the theoretical quantity of hydrogen is preferred corresponding to 4 1/2 to 15 mols. per mol. of nitrobenzene.  The catalyst may be employed as a fixed or fluidized bed and may be prepared by (a) impregnating active alumina with soluble thermally decomposable nickel salts (b), precipitation or coprecipitation of nickel and aluminium hydroxide or (c) coignition of nickel and aluminium salts, the resulting product in each case, optionally after reduction with hydrogen, being sulphided with hydrogen sulphide or carbon disulphide.  The alumina may constitute from 2 to 90 per cent. by weight of the catalyst, and if the alumina does not act as such, additional carriers such as silica, clays, activated alumina, corundum or charcoal may be incorporated before sulphiding. Regeneration may be effected by removing organic material with air or oxygen at 300-500 DEG C. followed by reduction with hydrogen at the same temperature (as in Specification 702,018). According to examples, 1 activated alumina is impregnated with nickel nitrate employing alternating reduced and atmospheric pressure to assist impregnation, heated to convert the nickel nitrate to oxide, sulphided with hydrogen sulphide and cooled and stored in an oxygen free atmosphere, 9 mols. of hydrogen per mol. of nitrobenzene are passed over the catalyst at 300 DEG C. in a converter as described in Specification 144,614, [Class 1 (i)], at a rate of 300 grams of nitrobenzene per volume of catalyst per hour.  The aniline is recovered by condensation.  Regeneration is effected by passing air and steam over the catalyst at 400 DEG C. followed by hydrogen and steam and finally by pure hydrogen. 2 as in 1 above except that an hourly rate of 1760 grams of nitrobenzene per litre of catalyst is employed 3 activated alumina is impregnated with nickel acetate in aqueous acetic acid, the slurry saturated with hydrogen sulphide, mixed with ammonium hydroxide and resaturated. The catalyst is dried and ignited in hydrogen at 350 DEG C.; 10.2 mols. hydrogen/mol. nitrobenzene are passed over the catalyst at 300 DEG C. at an hourly rate of 480 grams nitrobenzene per litre of catalyst, 4 ammonium carbonate is added to a mixed aluminium and nickel nitrate solution, the slurry dried and the resulting cake crushed.  The powder is sulphided at 350 DEG C. and reduced at 345 DEG C. An hourly rate of 300 grams nitrobenzene/litre of catalyst is employed in a hydrogenation at 300 DEG C. 5 a slurry is prepared as in 4, filtered, washed and reslurried.  The aqueous mixture is heated to 100  DEG C. for 18 hours thereby forming a proportion of hydrated nickel aluminate.  The slurry is filtered and the solid dried, ignited and sulphided as before.  6 a catalyst is prepared by coignition by replacing the activated alumina of 1 by alundum and replacing 2-25 mol. per cent. of the nickel nitrate by aluminium nitrate and treating the solid as in 1.  Specification 599,252 also is referred to.