Semi-continuous process for obtaining amino compounds

In a process for the production of a water-soluble aromatic amine compound by the reduction of a corresponding nitro compound selected from the group consisting of nitrobenzene, 2-nitro-4-methylsulphonyl-phenol, 2-nitro-2'-sulpho-4,4'-dichloro-diphenyl ether, 4,4'-dinitro-stilbene-2,2'-disulphonic acid, nitrobenzenedisulphonic acid-2,5,3-nitrobenzenesulphonic acid, 6-nitro-2-naphthol-4-sulphonic acid or 2-chloro-5-nitrobenzoic acid, with iron in acidic aqueous medium, the improvement comprising, a semi-continuous process comprising the steps of

• (1) providing an aqueous solution or suspension of the aromatic nitro compound in a first vessel,
• (2) providing an acidic aqueous suspension of iron particles in a second vessel,
• (3) introducing a less-than-stoichiometric amount of the suspension of the aromatic nitro compound from the first vessel into the second vessel,
• (4) allowing the acidic suspension of iron to react with the aromatic nitro compound to yield to aromatic amine compound and iron oxide, at about 50.degree. C. to about 110.degree. C.,
• (5) substantially separating the unreacted iron particles from the reaction mixture by removal of a substantial portion of the iron oxide, water and aromatic amine compound from the second vessel, while leaving the unreacted iron particles therein,
• (6) repeating steps (3), (4) and (5) while maintaining the acidity and the stoichiometric excess of unreacted iron in the reaction mixture.