Closing the Loop: Greener and Efficient Hydrolytic Depolymerization for the Recycling of Polyesters Using Biobased Eutectic Solvents

abstract

The imperative for achieving circularity in the realm of postconsumer polymers predominantly hinges upon the adoption of efficient recycling methodologies with a greener footprint. As such, this study introduces an innovative and eco-friendly depolymerization process for recycling highly consumed poly(ethylene terephthalate) (PET) and innovative bioderived poly(ethylene 2,5-furandicarboxylate) (PEF) which is easily extrapolated to other polyesters. This study demonstrates the pivotal role of eutectic solvents based on biobased phenols with safe design to efficiently mediate the hydrolytic depolymerization, under alkaline conditions, of these recalcitrant polymers into terephthalic acid (TPA) or 2,5-furandicarboxylic acid (FDCA). Additionally, optimization through a design of experiments approach yields TPA and FDCA with over 90% and 80% recovery, respectively, under mild conditions of temperature, below 150 °C, and not exceeding 5 h of reaction time. Structural characterization analyses confirm the chemical nature and the high purity of the recovered products, while eutectic solvent reuse assessments underscore its potential for multiple cycles with minimal loss of catalytic activity, reducing process waste. A proof-of-concept for monomer repolymerization demonstrates feasibility. Green metrics align with the fine chemicals industry, indicating promising market potential for this low-energy eutectic solvent-based approach to enhance circularity in polyester waste management.

authors

Vinícius de Paula, Simão V. Pandeirada, Paulo J. A. Ribeiro-Claro, Armando J. D. Silvestre, Andreia F. Sousa

Groups

G4 - Renewable Materials and Circular Economy
G6 - Virtual Materials and Artificial Intelligence

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

Rede Nacional de Ressonância Magnética Nuclear (PTNMR)

European network of FURan based chemicals and materials FOR a Sustainable development (FUR4Sustain)

acknowledgements

This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 (DOI 10.54499/UIDB/50011/2020), UIDP/50011/2020 (DOI 10.54499/UIDP/50011/2020), and LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020), financed by national funds through the FCT/MCTES (PIDDAC). This research is also sponsored by FEDER funds through the program COMPETE─Programa Operacional Factores de Competitividade─and by national funds through the FCT under Project UID/EMS/00285/2020. The NMR spectrometers are part of the National NMR Network (PTNMR) and are partially supported by Infrastructure Project N° 022161 (cofinanced by FEDER through COMPETE 2020, POCI and PORL and FCT through PIDDAC). The FCT is also acknowledged for the research contract to A.F.S. (CEECINSTLA/00002/2022) and for the Ph.D. grant to S.V.P. (2023.01628.BD). This publication is supported by COST Action FUR4Sustain─European network of FURan based chemicals and materials FOR a Sustainable development, CA18220, supported by COST (European Cooperation in Science and Technology).