Connecting Polymerization Physics to Macromolecular Deconstruction Product Distributions and Process Kinetics

Approaches that valorize plastics waste have continued to emerge over recent years. One common strategy is deconstruction, whereby polymers are degraded into smaller molecules by various reaction pathways. The dynamics of these complex systems of molecules, with evolving molecular weights and molecular weight distributions that span the range from monomer up to commodity polymer, are a strong function of process technology. Hence, efficient development of plastics deconstruction technologies will benefit from simple and descriptive models that link process parameters (e.g., reaction time) to physical properties (e.g., kinetic rate, solubility) and product distribution. In this work, we demonstrate a simple mathematical model containing modular components that describes the physical phenomena apparent in experimental results—for instance, a partitioning module was developed to simulate poor mixing between deconstruction products and the input polymer. We use this model in combination with well-described polymerization kinetics and experimentally measured molecular weight distributions to understand catalytic deconstruction more quantitatively. As one example, we highlight the role of polyolefin structure (i.e., branch content) on hydrotreatment product composition. This work demonstrates the ability to parameterize plastics valorization strategies, enabling detailed interpretation of experiments and informing the development of comprehensive models, and it could lead to the potential optimization of industrial deconstruction processes.