Study on Synthesis and Purification of D,L-Lactide

D,L-lactide was prepared from D,L-lactic acid with dibutyltin oxide as catalyst.Effects of catalyst quantity,dehydration temperature as well as addition of diluent on yield of lactide were studied.Crude lactide was purified through recrystallization.Lactide with high yield and high purity was obtained and identified by melting point,IR and ()~1H NMR spectrum.The proper amount of catalyst used was 1.5%,proper dehydration temperature was 140 ℃,and addition of diluent to reaction system at depolymerization stage could increase yield of crude lactide obviously(yield of crude lactide was up to 70.1%).Ethanol was an appropriate solvent for recrystallization,with which the total yield of purified lactide reached 37.3%.IR and ()~1H NMR spectrum proved the structure of the expected lactide.