EFRI E3P: Tuning Catalyst Design to Recycle Mixed Polymer Streams

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This project aims to develop a new approach to upgrade and recycle multilayer polymer films. Multilayer films generally perform better and require much less plastic material in applications such as packaging, but their complexity makes them far more challenging to recycle than other simpler forms of plastic like rigid bottles. The investigators in this project aim to develop catalysts that selectively target and convert components of the multilayer films, allowing the remaining polymer to be recycled using conventional methods. This catalytic targeting will be accomplished by modifying the surface of several promising catalyst supports and incorporating active sites on their surface to allow selective targeting and conversion of polymers or impurities of interest. Three families of catalysts will be evaluated based on their effectiveness for targeting and converting the components of interest, ease of separation from the multilayer polymer mixture, and effective re-use. A model will be constructed to determine the cost-effectiveness of each approach to refocus efforts on families of catalysts that exhibit the greatest potential for economically recycling multilayer films. The scientific and engineering research will be accompanied by public perception surveys and education interventions aimed at communicating the importance of this problem to the general public and thereby increasing public awareness, acceptance, and participation. Ultimately, this proposal will lay the groundwork for the cost-effective recycling of more advanced multilayered plastics. This will ideally enable the technological advantages that accompany multilayer plastics such as longer food shelf lives without sacrificing the ability to effectively recycle the plastics involved.Because multilayer films typically consist of very diverse sets of polymers, as well as trace amounts of tie layers, they are not compatible with traditional recycling technologies focused on a specific chemistry. Common approaches for their conversion are delamination or dissolution-precipitation using costly solvent-based processes that can easily become cost prohibitive when multiple streams are present. This proposal aims to develop a set of catalytic particles that target specific families of polymers in these multi-component films such that the nonpolar residue can be readily recycled. Polar polymers will be selectively targeted by manipulating external functional groups on three families of catalysts - carbon nanotubes, silica particles, and zeolites. These families are chosen based on their ease of introducing surface functionalities, effectiveness in targeting molten polymers, recovery, and regeneration after conversion of polar components. The team will further test the hypothesis that trace amounts of added water can serve to remotely activate some polar molecules through remote polarization and protonation, further extending the rates and selectivity activation of polar molecules in these blends. Resulting kinetic data will be incorporated into a techno-economic model to compare this approach with solvent-based approaches. This technical component of the research will be carried out in parallel with public perception surveys to guide improved public education regarding the importance of this problem, with this information being incorporated into the team’s outreach efforts. Outreach activities involving middle and high school students will be developed, while also creating research opportunities for undergraduate and graduate students spanning the diverse fields of Chemical Engineering and Psychology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.