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

摘要

Toluene diisocyanate is recovered from a crude distillation feed containing less than 2% by weight of phosgene by (a) fractionating the crude distillation feed containing less than 2% by weight of phosgene to remove the solvent and optionally the reaction residues to produce a crude toluene diisocyanate feed containing less than 20% by weight of solvent and (b) separating the crude toluene diisocyanate feed containing less than 20% by weight of solvent in a divided-wall distillation column into four product fractions P1-P4. P1 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 containing toluene diisocyanate and P4 is a toluene diisocyanate product stream lean in low-boilers, high-boilers and reaction residues.