Lactide Synthesis Using ZnO Aqueous Nanoparticles as Catalysts
2023
Shirley Duarte | Axel Dullak | Francisco P. Ferreira | Marcelo Oddone | Darío Riveros
The increasing global consumption of conventional plastics has led to significant environmental challenges due to their resistance to degradation and dependency on petroleum, a volatile resource. In this context, polylactic acid (PLA) has emerged as a promising biopolymer alternative, offering excellent physical and mechanical properties while being derived from renewable resources. The synthesis of PLA involves the production of lactide, a crucial cyclic monomer. This study focuses on lactide synthesis using zinc oxide (ZnO) nanoparticles as catalysts. The synthesis process consists of three stages: the dehydration of lactic acid, oligomerization to obtain a PLA oligomer, and depolymerization with simultaneous distillation to produce lactide. The ZnO nanoparticle catalyst proved to be highly efficient in regulating the molecular weight of the oligomer during depolymerization, which directly impacts the molecular weight of the PLA. The lactide purification using ethyl acetate resulted in an average purity of 90.0 ± 1.79%, demonstrating the effectiveness of the purification process. The quantification of lactide through high-performance liquid chromatography (HPLC) showed excellent linearities, allowing for the accurate determination of lactide content. The lactide synthesis yielded 77–80%, and the stability of the synthesized lactide was confirmed through a second purity determination after four months, with only a 1.7% loss in lactide content. Overall, this study showcases the feasibility of lactide synthesis using ZnO nanoparticles as catalysts and contributes valuable insights into producing high-quality lactides for PLA manufacturing.
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