Patent ID: 6486346
Filing Date: 2002-11-26
Classification: C07C

Abstract:
A process for the production of 2,3,5,6-tetramethyl-1,4-diisocyanatobenzene comprising:a) reacting 1,2,4,5-tetramethylbenzene with nitric acid in the presence of sulfuric acid to form 2,3,5,6-tetramethyl-1,4-dinitrobenzene, b) diluting liquid reaction mixture from a) with water to form a suspension, c) intensively mixing the suspension from b) with an aprotic organic solvent that is substantially immiscible with water and inert with respect to hydrogen to dissolve 2,3,5,6-tetramethyl dinitrobenzene present in the suspension and to form two liquid phases, d) separating the liquid phases from c) to recover a solution of 2,3,5,6-tetramethyl dinitrobenzene in organic solvent, e) hydrogenating the 2,3,5,6-tetramethyl-1,4-dinitrobenzene in the presence of a Raney catalyst, a palladium catalyst or a platinum catalyst to form 2,3,5,6-tetramethyl-1,4-diaminobenzene, f) removing water and the Raney catalyst, palladium catalyst or platinum catalyst from the hydrogenated mixture to obtain a solution of 2,3,5,6-tetramethyl-1,4-diaminobenzene, and g) phosgenating the 2,3,5,6-tetramethyl-1,4-diaminobenzene solution from f) to form 2,3,5,6-tetramethyl-1,4-diisocyanatobenzene.