Process for the purification of toluenediisocyanate incorporating a dividing-wall distillation column for the final purification

摘要

The invention is directed to a process for the purification of toluenediisocyanate from a crude distillation feed comprising less than 2% by weight of phosgene bya) fractionating the crude distillation feed comprising less than 2% by weight of phosgene to remove the solvent and optionally the reaction residues to produce a crude toluylenediisocyanate feed comprising less than 20% by weight of solvent and 'b) separating the crude toluylenediisocyanat feed comprising less than 20% by weight of solvent in a dividing-wall distillation column into four product fractions P1 - P4, wherebyP1 is a vapor phase low-boiler and solvent-enriched gas stream,P2 is a low-boiler and solvent-enriched product,P3 is a high boiler enriched bottoms product comprising toluenediisocyanat andP4 is a toluenediisocyanate product stream lean in low-boilers, high-boilers and reaction residues.