US Patent 7307190 Process for the preparation of toluenediamine

Toluenediamine is produced and separated from by-products of the reaction by:a) hydrogenating dinitrotoluene in the presence of a catalyst,b) separating the catalyst, water and optionally solvent from the hydrogenation reaction mixture to give crude toluenediamine, andc) separating by distillation the crude toluenediamine in a separating wall column into at least four product streams P1, P2, P3 and P4. The product stream P1 is a stream containing low boilers. The product stream P2 is a stream containing o-toluenediamine. The product stream P3 is a stream containing m-toluenediamine. The product stream P4 is a stream containing high boilers and m-toluenediamine.