Patent ID: 11926608
Assignee: NANJING UNIVERSITY
Field: Chemical engineering (Chemistry)
Classification: CPC C  B | IPC B  C

Claim 10:
11. A method for producing a lactide with the synthesis device of claim 1 comprising the following steps
(i) in the oligomer preparation system (I), using L-lactic acid, D-lactic acid, or DL-lactic acid as a raw material, carrying out a polymerization synthesis reaction at 100° C. to 180° C. under an absolute pressure of 1 KPa to 100 KPa, improving a yield by recovering lactic acid from a light component, and improving a molecular weight of oligolactic acid through reflux a heavy component, so as to obtain oligolactic acid with a weight-average molecular weight of 500 Da to 3,000 Da;
(ii) in the oligomer purification system (II), purifying the oligolactic acid obtained in step (1) to remove unreacted lactic acid and water;
(iii) in the oligomer depolymerization system (III), depolymerizing the oligolactic acid purified in step (2) under an action of a catalyst at 200° C. to 260° C. under an absolute pressure of 0.1 KPa to 1 KPa, purifying and collecting the light component to obtain the crude lactide, and refluxing and depolymerizing the heavy component again;
(iv) in the lactide purification system (IV), performing heat exchange for the crude lactide with a tubular heat exchanger of 0.1-0.25 m2 at the temperature between 20° C. and 60° C. to obtain the lactide product and the by-product; and
(v) in the recovery system (V), performing heat exchange for the by-product with a shell-and-tube heat exchanger of 0.1-0.25 m2 at the temperature between −20° C. and 40° C. to obtain a recovery liquid.