Achieving a circular plastics economy via catalytic upcycling is challenged by the chemical heterogeneity of waste plastics, which often contain both polyolefin and aromatic-rich oxygenated polymers. Additionally, emerging depolymerization approaches like hydrogenolysis face uncertainties due to the evolving cost and intermittency of green hydrogen. To address both challenges, we propose an adaptive catalytic reactor scheme capable of converting diverse plastic waste streams into liquid organic hydrogen carriers (LOHCs) or value-added fuels, depending on hydrogen availability. The key to this adaptability is a molybdenum-based catalyst encapsulated within a Brønsted-acidic zeolite framework. Prior work has shown that the catalytic phase of the molybdenum has a profound effect on its metallic and acidic character, thereby shifting its selectivity for C-C or C-O bond cleavage. We aim to leverage these properties by alternating between two operating modes: (1) a hydrogen-rich mode where catalytic hydrodeoxygenation converts aromatic-rich oxygenated species (e.g., polycarbonate) into saturated cyclic LOHCs, and (2) a hydrogen-lean mode where polyolefins are depolymerized and aromatized into high-value liquid aromatics, which can either be sold directly or hydrogenated further when hydrogen availability increases. To experimentally evaluate this concept, we have performed reaction testing in both pressurized batch and ambient pressure flow reactors at varying temperatures and hydrogen atmospheres using benzyl acetate and dodecane as model compounds for the first and second modes, respectively. These experimental results were used to inform a rigorous technoeconomic analysis (TEA) of a hypothetical waste plastic to LOHC refinery modeled using Aspen. While initial economic projections suggest commercial promise for this process, investigation is ongoing to demonstrate the reversible phase control of the molybdenum-based catalysts using regeneration strategies tailored to each operating mode.
