Title : Catalytic potential and practical limitations of N-doped nanomaterials in plastic depolymerization
Abstract:
Chemical depolymerization of polyethylene terephthalate (PET) offers a robust pathway for sustainable plastic recycling, yet traditional glycolysis remains energy-intensive and restricted by the separation challenges of homogeneous catalysts. This study explores the catalytic potential and operational limitations of heterogeneous, nitrogen-doped transition metal nanocatalysts (Mn, Co, Zn and Fe) for PET glycolysis.
To systematically evaluate performance, the catalysts were synthesized via the pyrolysis of metal-ligand complexes (using 1,10-phenanthroline) across three distinct carbonaceous supports: activated carbon, carbon nanofiber, and Vulcan XC72. Furthermore, the study presents a critical comparative analysis of two thermal activation methods: conventional heating and microwave-assisted depolymerization, to assess their respective impacts on reaction kinetics and energy efficiency.
Among the tested variations, the Mn-based nanocatalyst demonstrated superior catalytic activity. The N-doping mechanism proved crucial for stabilizing the highly dispersed metal active sites. Under conventional heating, the Mn/activated carbon system achieved an 87% yield of high-purity bis(2-hydroxyethyl) terephthalate (BHET) monomer at 200 °C within 2 hours. Notably, microwave-assisted glycolysis significantly accelerated the reaction rate compared to conventional methods, highlighting a promising pathway to reduce overall energy consumption. These finding demonstrate that the selection of catalyst supports for microwave-assisted PET chemolysis cannot be directly extrapolated from conventional thermal catalysis. Instead, optimal supports depend on the interplay between its dielectric properties, metal-support interactions, and the reaction mechanism governing bond cleavage.
This evaluation provides essential insights into optimizing support architecture and heating modalities, structuring a clear framework for the development of highly efficient, scalable, and reusable catalytic systems to advance the circular plastic economy.
