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Development of a continuous PET depolymerization process as a basis for a back-to-monomer recycling method

Development of a continuous PET depolymerization process as a basis for a back-to-monomer... AbstractThis study presents a new approach for the recycling of bilayered PET waste in an efficient, continuous process with a depolymerization degree >97%. The complex PET waste was converted by chemolysis into its monomers ethylene glycol (EG) and the corresponding salt of terephthalic acid (TA) in a twin-screw extruder (TSE). Via this method, the starting materials for PET production were recovered, and highly contaminated PET waste and PET composite materials were transformed into valuable starting materials. The PE layer of the composite PET/PE material remained inert under depolymerization conditions and could be separated by filtration. An increase in the rotational speed by 200 rpm in the TSE reduced the residence time, but the degree of depolymerization was not affected in a proportional manner. Thus, the results indicate that a shorter residence time can be compensated with intensified mechanical agitation due to higher rotational speeds to obtain a similar degree of depolymerization. These results support the potential of this recycling concept to substantially contribute to the implementation of a circular PET economy. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Green Processing and Synthesis de Gruyter

Development of a continuous PET depolymerization process as a basis for a back-to-monomer recycling method

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References (40)

Publisher
de Gruyter
Copyright
© 2021 Lars Biermann et al., published by De Gruyter
ISSN
2191-9550
eISSN
2191-9550
DOI
10.1515/gps-2021-0036
Publisher site
See Article on Publisher Site

Abstract

AbstractThis study presents a new approach for the recycling of bilayered PET waste in an efficient, continuous process with a depolymerization degree >97%. The complex PET waste was converted by chemolysis into its monomers ethylene glycol (EG) and the corresponding salt of terephthalic acid (TA) in a twin-screw extruder (TSE). Via this method, the starting materials for PET production were recovered, and highly contaminated PET waste and PET composite materials were transformed into valuable starting materials. The PE layer of the composite PET/PE material remained inert under depolymerization conditions and could be separated by filtration. An increase in the rotational speed by 200 rpm in the TSE reduced the residence time, but the degree of depolymerization was not affected in a proportional manner. Thus, the results indicate that a shorter residence time can be compensated with intensified mechanical agitation due to higher rotational speeds to obtain a similar degree of depolymerization. These results support the potential of this recycling concept to substantially contribute to the implementation of a circular PET economy.

Journal

Green Processing and Synthesis – de Gruyter

Published: Jun 29, 2021

Keywords: depolymerization; alkali hydrolysis; PET waste; chemical recycling; circular economy

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