| 摘要 |
PROBLEM TO BE SOLVED: To provide an improved method for recovery and purification of toluene diisocyanate (TDI). SOLUTION: The method for purification of the TDI is carried out 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 toluylene diisocyanate feed containing less than 20% by weight of solvent and (b) separating the crude toluylene diisocyanate feed containing less than 20% by weight of solvent in a dividing-wall distillation column into four product fractions P1-P4. The 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 comprising TDI and P4 is a TDI product stream lean in low-boiler, high-boilers and reaction residues. COPYRIGHT: (C)2004,JPO
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