GB645736A - Improvement in preparation of propylenediamine - Google Patents

Abstract

1,2-Propanediamine (propylenediamine) is obtained by reacting 1-aminopropanol-2 with ammonia in the presence of a hydrogenation catalyst. The reaction is preferably effected at between 125 DEG and 250 DEG C., and especially at 170 DEG to 200 DEG C., and the preferred pressure range is from 400 to 2000 pounds per square inch. Specified hydrogenation catalysts are nickel, cobalt, copper chromite, and especially finely-divided nickel or cobalt prepared by dissolving other metals out of their alloys with nickel or cobalt. The reaction may be carried out in the presence of hydrogen which may be admitted to the reactor to an initial pressure of 250 to 600 lbs. per square inch at room temperature, but on heating the final pressure may be allowed to reach 1000 to 2000 lbs. per square inch. In examples: (1) 1-aminopropanol-2, anhydrous ammonia and Raney nickel are heated under hydrogen pressure in a rocking autoclave at 180 DEG C. for 5 1/2 hours. The propylenediamine is separated by releasing the pressure and distilling the products. Some 2,5-dimethyl piperazine is also formed; (2) the procedure of (1) is repeated except that the mixture is heated for about eight hours at 185 DEG C.; (3) monoisopropanolamine, ammonia and Raney nickel are heated at 174 DEG C. for about five hours, the maximum pressure developed being 675 lbs. per square inch. The propylene diamine is separated by distillation. In a comparative example, a mixture of 1,2-propylene glycol, anhydrous ammonia and Raney nickel is heated at 180 DEG C. for 6.5 hours under an initial hydrogen pressure of 400 lbs. per square inch. On releasing the pressure and distilling a low yield of 2-amino-propanol-1 is obtained.