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

US7108770B2 · kind B2 · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Marcus Paul Grün · Shanghai, CN
• Bill Brady · Goldkronach, DE
• Berthold Keggenhoff · Krefeld, DE
• Kai Verkerk · Hilden, DE
• Hans-Peter Schal · Dormagen, DE

Key dates

• Filing date: Oct 16, 2003
• Grant date: Sep 19, 2006
• Expiry date: Jul 21, 2024

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S203/11
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

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.