摘要
Abstract
A series of rare earth composite solid super acidic catalysts SO2-4/ZnO-ZrO2/La3+ were prepared by precipitation titration and characterized by means of FTIR and SEM. The results showed that the SO2-4 ions were bound with the Zr and Zn on the ZnO and ZrO2 crystal surfaces by either chelating or bidentate bridging. Prismatic ZnO and cubic ZrO2 crystals with superacidity were observed in the SO2-4/ZnO-ZrO2/La3+. The obtained SO2-4/ZnO-ZrO2/La3+ was used in synthesis of D,L-lactide from D,L-lactic acid. The effects of n (Zn2+ ) : n(Zr4+ ) in SO2-4VZnO-ZrO2/La3+ and thecatalyst dosage on the catalyst activity in the synthesis were investigated. Under the optimal conditions of n(Zn2+ ):n(Zr4+ ) 2 : 1 in S02VZn0-Zr02/La3+, D,L-lactic acid 60 g, catalyst dosage 1. 0% (based on the D,L-lactic acid mass), vacuum degree of dehydration 0.050 -0.060 Mpa, dehydration temperature 140 ℃, dehydration time 2.0 h, vacuum degree of depolymerization 0.085 -0.095 Mpa, depolymerization temperature 200℃ and termination temperature of the depolymerization 245 ℃, the crude D,L-lactide yield could reach 82.7%.关键词
稀土复合固体超强酸催化剂/D,L-乳酸/D,L-丙交酯/镧Key words
rare earth composite solid super acidic catalyst/D, L-lactic acid/D, L-lactide/lanthanum分类
化学化工
