Multistage Chemical Recycling of Polyurethanes and Dicarbamates: A Glycolysis–Hydrolysis Demonstration

Pegah Zahedifar, Lukasz Pazdur, Christophe M. L. Vande Velde and Pieter Billen
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Pegah Zahedifar: Faculty of Applied Engineering, iPRACS, University of Antwerp, 2020 Antwerp, Belgium
Lukasz Pazdur: Faculty of Applied Engineering, iPRACS, University of Antwerp, 2020 Antwerp, Belgium
Christophe M. L. Vande Velde: Faculty of Applied Engineering, iPRACS, University of Antwerp, 2020 Antwerp, Belgium
Pieter Billen: Faculty of Applied Engineering, iPRACS, University of Antwerp, 2020 Antwerp, Belgium

Sustainability, 2021, vol. 13, issue 6, 1-13

Abstract: The use of polyurethanes and, therefore, the quantity of its scrap are increasing. Considering the thermoset characteristic of most polyurethanes, the most circular recycling method is by means of chemical depolymerization, for which glycolysis is finding its way into the industry. The main goal of polyurethane glycolysis is to recover the polyols used, but only limited attempts were made toward recovering the aromatic dicarbamate residues and derivates from the used isocyanates. By the split-phase glycolysis method, the recovered polyols form a top-layer phase and the bottom layer contain transreacted carbamates, excess glycol, amines, urea, and other side products. The hydrolysis of carbamates results in amines and CO 2 as the main products. Consequently, the carbamates in the bottom layer of polyurethane split-phase glycolysis can also be hydrolyzed in a separate process, generating amines, which can serve as feedstock for isocyanate production to complete the polyurethane material cycle. In this paper, the full recycling of polyurethanes is reviewed and experimentally studied. As a matter of demonstration, combined glycolysis and hydrolysis led to an amine production yield of about 30% for model systems. With this result, we show the high potential for further research by future optimization of reaction conditions and catalysis.

Keywords: recycling; chemical recycling; polyurethanes; carbamates; glycolysis; hydrolysis (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
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