Recycling of Polyurethane via Mechanocatalytic Methanolysis/Hydrolysis

Polyurethane (PU) is the 6th most produced plastic on a global basis, and thus one of the most important targets in the field of recycling of plastic waste. The glycolysis of PU is currently considered the most promising pathway toward industrial implementation. However, the energy consumption during the process, the cost of the excess glycol relative to PU, and the potentially reduced quality of polyol products resulting from glycol residues may still limit the speed of implementation of PU chemical recycling processes from lab to the pilot plant scale. Therefore, an alternative route for PU depolymerization is explored using mechanochemistry and catalysis. In this work, recovery of up to 86% of soluble polyol by mechanocatalytic methanolysis/hydrolysis of NaOH-impregnated commercial PU product (household sponge), with a Cu/MgAlO_x co-catalyst below 100 °C, is described. The recycled polyol can serve as new raw material and has been successfully used as feedstock for the resynthesis of PU. The low reaction temperature, reduced volume of solvent, and easy separation of products could make this novel chemical recycling methodology an attractive alternative to the conventional solvolysis pathways.

In this article published in ChemSusChem, a novel low-temperature mechanocatalytic methanolysis/hydrolysis method using NaOH and a Cu/MgAlOx co-catalyst is presented for the efficient depolymerization of commercial polyurethane, enabling up to 86% recovery of reusable polyol with potential advantages over conventional solvolysis techniques.

Authors: Bolun Wang, Joel Britschgi, Nguyen Khang Tran, Ivana Jevtovikj, Piyush Ingale, Cansu Mai, Stephan Andreas Schunk, Ferdi Schüth