Efficient Synthesis of Lactide with Low Racemization Catalyzed by Zinc Lactate and Creatinine and Polycondensation Kinetics

l-Lactide is an important intermediate for the industrial production of polylactic acid (PLA). However, several serious issues still remain to be solved, including low yield and low purity induced by racemization. In this work, we developed a new catalytic system of zinc lactate (Zn(La)2) and creatinine (CR) for lactide synthesis. At a depolymerization cyclization temperature of 240 °C, the yield of crude lactide reaches 98.12%, and after purification, the yield of l-lactide reaches 77.09% with a purity of up to 98.00%. Furthermore, a second-order pseudo-homogeneous kinetic model was established for the polycondensation process, and the model fitting was in good agreement with experimental data in the temperature range of 393.15 to 423.15 K.