Study on Optimization of Synthesis and Purification of L-Lactide

L-Lactide was prepared from L-lactic acid with stannous octoate as catalyst by means of condensation polymerization and depolymerization.Effects of catalyst amount,dehydration temperature,depolymerization temperature on yield of L-lactide and its purity were studied.Crude L-lactide was obtained by improved synthesis process.Purification of L-lactide by recrystallization with the combined method of alternating solvents and concentration gradient was carried out.Both total yield and purity of L-lactide were raised.The L-lactide with high purity was identified by melting point,specific rotation,infrared spectroscopy,hydrogen spectrum of nuclear magnetic resonance.