Patent ID: 6803483
Filing Date: 2004-10-12
Classification: C07C

Abstract:
Process for the purification of toluenediisocyanate by fractionating a crude distillation feed comprising toluenediisocyanate, an organic solvent and less than 2% by weight of phosgene in a heat integrated system comprising an upstream distillation column, an interchanger and a downstream distillation column which are connected in series,wherein the vapor which is recovered from the upstream distillation column is used to reboil the bottoms product of the downstream distillation column or the feed to the downstream distillation column in the interchanger, and wherein the crude distillation feed comprising less than 2% by weight of phosgene is fractionated into three product fractions P1-P3 and optionally a fourth fraction P4, wherein P1 is a noncondensible gas stream enriched with phosgene and/or low-boilers, P2 is a solvent-enriched product, P3 is a high boiler enriched bottoms product comprising toluenediisocyanate and P4 is a toluenediisocyanate enriched stream lean in highboilers and reaction residues.