Supercritical fluid technology for chemical recycling of bio-based polyesters
A supercritical fluid solvolysis method that uses supercritical CO2 as a co-solvent to depolymerize biodegradable aliphatic polyesters such as PLA and PHA, enabling catalyst-free recovery of high-quality monomers for circular-economy plastics recycling.
Overview
This research proposes a novel chemical recycling approach for bio-based and biodegradable polyesters, including polylactic acid (PLA) and polyhydroxyalkanoate (PHA), using binary supercritical fluid (SCF) solvolysis. Conventional polyester recycling relies on alcoholysis of C-O bonds, but traditional catalytic methods introduce purification challenges. By leveraging the unique solubility and zero surface tension properties of supercritical fluids, this technology achieves full polymer depolymerization without catalysts, producing high-purity monomers suitable for repolymerization. The approach supports circular-economy goals for sustainable plastics and can accommodate mixed plastic waste streams.
Technical specifications
- Supercritical fluid solvolysis as the primary depolymerization mechanism for aliphatic polyesters
- Supercritical CO2 (scCO2) as a co-solvent to lower critical temperature and pressure requirements, reducing energy demands
- Catalyst-free process that eliminates contamination and simplifies monomer purification
- Temperature/pressure-dependent solubility control enabling an integrated separation process for monomer recovery
- Feedstock flexibility allowing processing of mixed plastic waste, including commercial PLA and PHA
- Builds on prior validated subcritical methanolysis/ethanolysis achieving greater than 99% monomer conversion and approximately 96% polymer recovery
- Developed collaboratively at Florida State University and the University of Konstanz, combining expertise in polymer crystallization and high-pressure supercritical fluid processing
Technology readiness level
This technology is at an early-stage proof-of-concept phase (TRL 2-3). The proposed validation comprises three phases: (a) experimental setup development using high-pressure vessel expertise, (b) theoretical assessment of critical conditions for the fluid mixture across varying temperature, pressure, and molar ratios, and (c) proof-of-concept depolymerization and product separation experiments guided by process optimization. Prior foundational work on subcritical alcoholysis of aliphatic polyesters has been demonstrated, providing a strong technical basis. Further development is needed to scale the process and validate performance with commercial-grade PLA and PHA feedstocks.
About Florida State University
Florida State University is a comprehensive public research university in Tallahassee serving a large, diverse student body and combining broad academic breadth with intensive research. Industry engages through a research and technology park adjacent to campus that co‑locates university labs with companies and offers shared core facilities and high‑performance computing. The College of Medicine’s statewide clinical partnerships enable translational collaborations and community‑based studies. Research is supported by competitive federal funding from the National Science Foundation, National Institutes of Health, Department of Energy, and Department of Defense, plus State of Florida and industry support. A dedicated technology transfer office manages IP, licensing, and startup formation, with incubator and prototyping space available in the park.
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