Catalyst selection and thermal kinetics of oligomeric PGA depolymerization process

Several metal oxides and their salts are used as catalysts to study the depolymerization of polyglyolic acid( PGA) oligomers. It is found that the temperature of depolymerization reaction decreases obviously under the catalysis of Zn( acac)2. At the same time,the coking is reduced in the process of preparing glycolide with the improved yield of glycolide. Zn( acac)2is also applied in the solution depolymerization of PGA,and thermal degradation of the azeotropic solvent is prevented at high temperature. It proves that Zn( acac)2can enhance the efficiency of depolymerization and the higher catalytic activity is thought to correlate to the coordination-insertion mechanism. The experimental results show that PGA oligomer is depolymerized at lower temperature( 200℃) under Zn( acac)2catalyst with a mass fraction of 0. 4%.The yield of glycolide reaches 95%. The activation energy value in process of oligomer depolymerization is lower in the presence of Zn( acac)2than the other catalysts,enhancing the efficiency of depolymerization.