Lactide

the important intermediate for synthesis of poly lactic acid

was prepared from D

L-lactic acid with ionic liquid as catalyst. High purity lactide was obtained by recrystallization

and identified with melting point measurement and infrared ray spectroscopy. The influence factors

such as the type and dosage of ionic liquid on the yield of lactide were discussed in the preparation of lactide. The results showed that ionic liquid as catalyst was feasible and could lower the viscosity of the reaction system for preparation of lactide under mild reaction conditions

and the optimum conditions for using ［NH (C2H5)3］［HSO4］ catalyst were that the dosage of catalyst was 5%(mass)

oligomerization and depolymerization temperature were in the range of 110—140℃ and 190—250℃ respectively.