Efficient Synthesis\nof Lactide with Low Racemization\nCatalyzed by Zinc Lactate and Creatinine and Polycondensation Kinetics

l-Lactide is an important intermediate for the\nindustrial\nproduction of polylactic acid (PLA). However, several serious issues\nstill remain to be solved, including low yield and low purity induced\nby racemization. In this work, we developed a new catalytic system\nof zinc lactate (Zn(La)<sub>2</sub>) and creatinine (CR) for lactide\nsynthesis. At a depolymerization cyclization temperature of 240 °C,\nthe yield of crude lactide reaches 98.12%, and after purification,\nthe yield of l-lactide reaches 77.09% with a purity of up\nto 98.00%. Furthermore, a second-order pseudo-homogeneous kinetic\nmodel was established for the polycondensation process, and the model\nfitting was in good agreement with experimental data in the temperature\nrange of 393.15 to 423.15 K.