Abstract
Polymers are involved in countless products ranging from high-tech materials used in areo-space industry, car parts, electronics to simple consumer goods such as clothing, sports gear, carpets, and various packing materials. As a result, humanity currently produces a previously unmatched amount of plastic waste. A lot of this waste is currently dumped in landfills or “mismanaged”. In order to counter-act the pollution of the environment as well as to conserve natural resources several strategies have been proposed and developed for the recycling of polymeric materials. Depolymerization and mechanical recycling are being the most applied one. Both approaches have in common that it is very difficult for them to be cost competitive with the production of the virgin polymers. A solution to this dilemma could be “chemical upcycling”. In this approach a polymer is converted to a new material or higher valuable commodity. In the case of polyesters, we could show that in the presence of a homogenous ruthenium catalyst and Lewis acids polyesters can be hydrogenated to polyether polyols. The type of Lewis acid and its ratio with respect to the ruthenium proofed to crucial. Based on mechanistic investigations it was shown that this reaction proceeds via a tandem hydrogenation/etherification process. The obtained polyether polyols are in the right molecular weight range for the use in adhesives.
Highlights
A lot of plastic waste is currently dumped in landfills or “mismanaged”
We developed a homogenous hydrogenation protocol in the presence of Lewis acids that enables the synthesis of polyether polyols from polyesters
The nature of the Lewis acid as well as the ratio to the ruthenium catalyst was found to be crucial for the selective formation of ether bonds
Summary
A lot of plastic waste is currently dumped in landfills or “mismanaged”. Due to natural erosion phenomena this waste is transported by rivers and from there to the oceans,[1] where it forms “islands” that can reach three times the size of France.[2] plastics are directly dumped from ships to the waters.[3] There it causes great harm to aquatic life and in the form of micro plastic makes its way into the animal and human food sources.[4] The estimate of the amount of plastic marine debris circulating in 2020 ranges from 50 to 150 million tons.[1] The damage to the ecosystem and the possible negative health effects for humans led to the development of various concepts for solving this problem. The most applied concepts are mechanical recycling and depolymerization.
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