Demonstration of a Chemical Recycling Concept for Polybutylene Succinate Containing Waste Substrates via Coupled Enzymatic/Electrochemical Processes

Abstract

Chemical recycling of polymer waste is a promising strategy to reduce the dependency of chemical industry on fossil resources and reduce the increasing quantities of plastic waste. A common challenge in chemical recycling processes is the costly downstream separation of reaction products. For polybutylene succinate (PBS) no effective recycling concept has been implemented so far. In this work we demonstrate a promising recycling concept for PBS, avoiding costly purification steps. We developed a sequential process, coupling enzymatic hydrolysis of PBS with an electrochemical reaction step. The enzymatic step efficiently hydrolyses PBS in its monomers, succinic acid and 1,4-butanediol. The electrochemical step converts succinic acid into ethene as final product. Ethene is easily separated from the reaction solution as gaseous product, together with hydrogen as secondary product, while 1,4-butanediol remains in the aqueous solution. Both reaction steps operate in aqueous solvent and benign reaction conditions. Furthermore, the influence of electrolyte components on the electrochemical step was unraveled by applying molecular dynamic simulations. The final coupled process achieves a total ethene productivity of 91 μmol/cm² over a duration of 8 hours, with 1110 μmol/cm² hydrogen and 77 % regained 1,4-butanediol as valuable secondary products.