Process for separating dimethyl isophthalate and dimethyl orthophthalate from their mixture with dimethyl terephthalate

US4683034A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Rolf Bader · Riehen, CH
• Hartmut Last · Augsburg, DE
• Manfred Mayer · Niedernhausen, DE
• Siegbert Rittner · Mörfelden, DE
• Edgar Wetzel · Heusenstamm, DE

Key dates

• Filing date: Aug 16, 1985
• Grant date: Jul 28, 1987
• Expiry date: Aug 16, 2005

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C67/54
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

The invention relates to a process for separating dimethyl isophthalate (DMI) and dimethyl orthophthalate (DMO) and other by-products from their mixture with dimethyl terephthalate (DMT), formed in the oxidation of p-xylene followed by esterification with methanol, by crystallization from the melt. Initially, the esterification product is here distilled once or several times. The DMT-rich fraction obtained is then subjected wholly or partially to one or several crystallizations from the melt, and the DMI-DMO fraction thus obtained is at least partially removed from the system. As an alternative, the DMT-rich fraction is first recrystallized from methanol, the methanol is then evaporated from the mother liquor and the remaining residue is subjected to one or several crystallizations from the melt. The DMI-DMO fraction thus obtained is again at least partially removed from the system.