(576a) Leveraging Polymer Characterization to Gain Key Insights into Polyolefin Deconstruction Processes

New technologies to mitigate the accumulation of plastics waste provide an opportunity to better utilize valued carbon resources. The diversity of valorization, recycling, and upcycling strategies has spearheaded research that optimizes variables, such as (bio)catalyst type or features, product selectivity, and process design. Unfortunately, critical concepts (e.g., transport phenomena, thermodynamics) and experimental characterization (e.g., rheology, calorimetry) for macromolecules often are not integrated into end-of-life plastics management. In this work, we present two case studies that connect polymer physics and methodology to the deconstruction products obtained from plastics waste. In the first study, we demonstrate the effect of polyethylene architecture on conversion via hydrotreatment. We show that the fundamental kinetic and transport parameters associated with deconstruction reactions can be explained using rheological measurements of the polymer melt. Although at the monomeric level all polyethylenes are functionally equivalent, we show that fundamental polymer features (e.g., branches, entanglements) are responsible for important differences in catalytic performance in deconstruction processes. In the second case study, we highlight the importance of large molecular weight (polymeric) products generated by the catalytic deconstruction of polyolefins and polystyrene in understanding the overall valorization process. Using detailed mathematical analysis of gel permeation chromatography data, we quantify product species that are often hidden by unreacted polymer, providing insight into kinetic and transport mechanisms associated with polymer deconstruction. Overall, this work presents a framework for important assessments of waste plastic conversion strategies using first principles to drive meaningful innovations in plastics waste valorization.