Polyesters Catalytic Chemical Recycling in Continuous Flow Reactors

Establishing a circular economy requires the development of plastic chemical catalytic recycling (CCR) processes, where catalysts are employed to produce high-value compounds from waste plastic streams. Polyesters such as polyethylene terephthalate (PET), polylactic acid (PLA), and polyhydroxybutyrate (PHB) are among the most abundant plastic wastes, primarily from packaging. However, current CCR methodologies are either poorly selective, resulting in low-value mixtures used as fuel, or are conducted in discontinuous operations that are difficult to scale. To address this, conducting CCR in continuous flow systems with selective and active heterogeneous catalysts has the potential to unlock new valorisation pathways. Here I will propose the first proof-of-concept for a liquid-phase, heterogeneously catalysed continuous flow CCR process for three polyesters (PET, PLA, PHB). The aim is the selective and sustainable depolymerization of common polyesters into reusable chemicals using unconventional, innovative bifunctional monolithic catalyst. This will be pursued through two complementary objectives: the synthesis of interconnected, hierarchically porous 3D-shaped solid bifunctional catalysts composed of metal nanoparticles supported on acidic mixed oxides, and the demonstration of the hydrogenative depolymerization of these three polyesters (PET, PLA, PHB) in a continuous flow system using the catalyst. Ultimately, this CCR methodology will provide an innovative technology that advances existing processes and contributes to establishing new recycling pathways for waste plastics. Eventually, it will support the development of a circular economy for plastics and help reducing the societal environmental impact.