Abrégé

This invention relates to a method for the continuous production of optically pure lactide comprising a first reactive distillation system, a second reactive distillation system, a main distillation system and the side-draw refluxer. For each of the four systems a novel horizontally top-mounted condenser is used in order to decrease its total pressure drop and thus reduce side-reactions associated with high bottom temperature. In addition, a wiped film evaporator, a short path evaporator or a combination thereof is utilized for the concentration of the purge stream from the second reactive distillation, in a purpose of removing the metal contaminants contained in the purge stream and depolymerizing the contained unconverted lactic acid oligomers to crude lactide, all of which give additional advantages for the lactide production.

Classes IPC  ?

• C07D 319/12 - Dioxanes-1, 4Dioxanes-1, 4 hydrogénés non condensés avec d'autres cycles
• B01D 3/00 - Distillation ou procédés d'échange apparentés dans lesquels des liquides sont en contact avec des milieux gazeux, p. ex. extraction
• B01D 3/14 - Distillation fractionnée
• B01D 5/00 - Condensation de vapeursRécupération de solvants volatils par condensation

Abrégé

This invention relates to a process for the continuous production of optically pure lactide from an aqueous solution of lactic acid by means of two reactive distillations followed by a main distillation column with a side-draw refluxer. The first reactive distillation is used for the preparation of lactic acid oligomers and the second reactive distillation used for the depolymerization of the thus obtained lactic acid oligomers to lactide. The crude lactide generated from the second reactive distillation is further purified in the main distillation column with a side-draw refluxer being connected to.

Classes IPC  ?

• C07D 319/12 - Dioxanes-1, 4Dioxanes-1, 4 hydrogénés non condensés avec d'autres cycles

Abrégé

This invention relates to a method for the continuous production of optically pure lactide comprising the first reactive distillation, the second reactive distillation, the main distillation and the side-draw refluxer. For each of the four systems a novel horizontally top-mounted condenser is used in order to decrease its total pressure drop and thus reduce side-reactions associated with high bottom temperature. In addition, a wiped film evaporator, a short path evaporator or a combination thereof is utilized for the concentration of the purge stream from the second reactive distillation, in a purpose of removing the metal contaminants contained in the purge stream and depolymerizing the contained unconverted lactic acid oligomers to crude lactide, all of which give additional advantages for the lactide production.

Classes IPC  ?

• C07D 319/12 - Dioxanes-1, 4Dioxanes-1, 4 hydrogénés non condensés avec d'autres cycles
• B01D 5/00 - Condensation de vapeursRécupération de solvants volatils par condensation

Abrégé

This invention relates to a method for the continuous production of optically pure lactide comprising the first reactive distillation, the second reactive distillation, the main distillation and the side-draw refluxer. For each of the four systems a novel horizontally top-mounted condenser is used in order to decrease its total pressure drop and thus reduce side-reactions associated with high bottom temperature. In addition, a wiped film evaporator, a short path evaporator or a combination thereof is utilized for the concentration of the purge stream from the second reactive distillation, in a purpose of removing the metal contaminants contained in the purge stream and depolymerizing the contained unconverted lactic acid oligomers to crude lactide, all of which give additional advantages for the lactide production.

Classes IPC  ?

• C07C 59/08 - Acide lactique
• C07D 319/12 - Dioxanes-1, 4Dioxanes-1, 4 hydrogénés non condensés avec d'autres cycles

Abrégé

This invention relates to a process for the continuous production of optically pure lactide from an aqueous solution of lactic acid by means of two reactive distillations followed by a main distillation column with a side-draw refluxer. The first reactive distillation is used for the preparation of lactic acid oligomers and the second reactive distillation used for the depolymerization of the thus obtained lactic acid oligomers to lactide. The crude lactide generated from the second reactive distillation is further purified in the main distillation column with a side-draw refluxer being connected to.

Classes IPC  ?

• C08G 63/08 - Lactones ou lactides
• C07D 319/12 - Dioxanes-1, 4Dioxanes-1, 4 hydrogénés non condensés avec d'autres cycles
• C07B 57/00 - Séparation de composés organiques optiquement actifs
• B01D 3/34 - Distillation ou procédés d'échange apparentés dans lesquels des liquides sont en contact avec des milieux gazeux, p. ex. extraction avec une ou plusieurs substances auxiliaires
• C08G 63/78 - Procédés de préparation

Abrégé

The present invention relates to a method for the separation of meta-phenylenediamine from the ortho-phenylenediamine and para-phenylenediamine by means of distillation, wherein the distillation may be performed in one stage, i.e. a main distillation stage or in two stages, i.e. a secondary distillation stage prior to a main distillation stage. In any case, a divided wall column is used in the main distillation stage.

Classes IPC  ?

• C07C 211/51 - Phénylènediamines
• C07C 209/86 - Séparation