Reaction system and method for preparing lactide from lactic acid

Abstract

The invention provides a reaction system and method for preparing lactide from lactic acid. The reaction system comprises a lactic acid oligomerization reaction kettle, a first reactive distillation tower, a lactide synthesis kettle and a second reactive distillation tower which are connected in sequence; the first reactive distillation tower comprises a first tower kettle reboiler, a purification section and a deep oligomerization dehydration reaction section, the purification section and the deep oligomerization dehydration reaction section are arranged from top to bottom, and a first feed port is formed in the tower section between the purification section and the deep oligomerization dehydration reaction section and used for introducing a product of the lactic acid oligomerization reaction kettle into the first reactive distillation tower. According to the reaction system provided by the invention, by uniformly integrating rectification and deep synthesis reaction, the reaction route is optimized, the reaction separation efficiency is improved, the product quality and yield are further improved, and in addition, the effects of saving the equipment cost and saving the occupied area of the equipment are also achieved.

Description

technical field [0001] The invention relates to the field of lactide preparation, in particular to a reaction system and method for preparing lactide from lactic acid. Background technique [0002] The production, development and utilization of lactide have been paid more and more attention in recent years, mainly because the ring-opening polymerization of lactide is an effective method for preparing high molecular weight polylactic acid. Polylactic acid is a promising biodegradable material. Because the final products of its decomposition in the natural environment are carbon dioxide and water, it is non-toxic and harmless to the environment, and has good biocompatibility and biodegradability. It is an excellent medical polymer material due to its excellent mechanical properties and easy processing and molding. The ring-opening polymerization of lactide is an effective method to prepare high-molecular-weight polylactic acid, and the molecular weight of the polymerization p...

AI Technical Summary

Problems solved by technology

[0009] Among them, the oligomerization reaction process in the first step is dehydration between lactic acid molecules. Since the oligomerization reaction itself is a reversible reaction, the presence of water will dilute the reaction materials and affect the reaction rate, thereby affecting the normal progress of the reaction process.

[0010] The efficiency of the separation system of the lactide synthesis reaction in the second step is low. Due to the high viscosity of the system and the small separation interface, the generated lactide cannot be taken out in time to make the esterification reaction reach an equilibrium state, causing the oligomer to proceed in the direction of the polymerization reaction. , reducing the lactide product yield

Long residence time in the reaction process leads to more by-products and indirectly affects the quality of the product

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