Synthesis method and device for rapidly producing lactide at high yield

摘要

The invention discloses a synthesis method and device for rapidly producing lactide at high yield. The method comprises the steps: adding a lactic acid single component or lactic acid into a catalystdouble component, enabling the mixture to enter an oligomer preparation system through a mixer, increasing the residence time through bottom circulation, synthesizing oligomeric lactic acid, and enabling a gas-phase component to pass through a rectification system, so as to improve the yield of oligomeric lactic acid; removing unreacted lactic acid and water from the oligomeric lactic acid througha purification device; and adding a catalyst into the light-component-removed oligomeric lactic acid, allowing the mixture to pass through a mixer, allowing the mixture to enter a depolymerization reactor, depolymerizing so as to obtain lactide, allowing heavy components to enter the depolymerization reactor again through reflux, and allowing light components to pass through a purification and recovery system so as to obtain the lactide product. With the adoption of the device, lactide can be efficiently synthesized, crude lactide with the yield of 94-98% can be obtained within short residence time of 0.5-5 minutes, the molecular weight of the heavy-component polylactic acid is slowly increased, and the heavy-component polylactic acid can be returned for depolymerization; after the lightcomponents pass through a simple purification system, the content of L-lactide, D-lactide or DL-lactide in the lactide product is 94%-98%, and the content of meso-lactide is 0.5%-5.5%.