2025 AIChE Annual Meeting

(43d) Improved Kinetic and Thermodynamic Modeling of PLA Depolymerization Processes

Authors

Troy Gustke, Virginia Tech
Y. Liu, Virginia Tech
Polylactic acid (PLA) is a biologically derived polyester that has seen increasing use in consumer goods and medical applications. Production of PLA is complicated by underlying stereochemistry of the material and the difficulty to directly produce PLA from the monomer lactic acid. Many PLA production pathways form lactide from lactic acid and take advantage of differing properties of lactide diastereomers refine lactide and produce high molecular weight, stereopure PLA. The circularity of PLA can be enhanced by developing chemical recycling technologies to recycle PLA waste taking advantage of the reversible esterification chemistry.

There are different methods to chemically recycle PLA, and proper evaluation requires the consideration of integration of the recycling process into PLA production supply chains. There are presently no methods available to model the production of PLA from lactic acid through the lactide polymerization pathway that consider reaction kinetics and product stereochemistry. Developing a detailed process model for PLA production is a necessary step in evaluating the potential of PLA chemical recycling.

In this work, we define and estimate properties of relevant components in separation such as the diastereomers of lactide and oligomers of lactic acid necessary for modeling crystallization and distillation operations. We also develop the first model incorporating the parallel ring opening and condensation reactions, derived from the foundation nylon 6 kinetic model. Finally, we introduce catalyzed and uncatalyzed kinetic factors for racemization of lactic acid derivatives to estimate changes in stereochemistry from reactions. This work can be used for the development and improvement of processes to refine PLA derivatives and is particularly useful for understanding how chemically recycled PLA of mixed stereopurity can be refined into stereopure products.