EFRI E3P: Hydrogenolysis for upcycling of polyesters and mixed plastics

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Using plastics has tremendous benefits for humanity; however, the lifetime of plastic products is long, creating an enormous accumulation of plastic wastes. Upcycling of plastics involves transforming plastic waste into new materials with high economic and environmental value. One of the major challenges for plastics upcycling efforts is the complexity of the feed stream. The various polymers in plastic wastes have diverse molecular structures, and plastic wastes typically contain significant levels of additive and contaminants. Methods that allow processing of mixed plastic wastes can reduce costs associated with sorting, but these methods will require robust process technology capable of handling highly heterogeneous waste streams. Development of such processes requires new experimental and computational tools to understand how the various components of plastic wastes interact with the catalysts that are used to drive such processes. This project combines a variety of closely coupled, experimental and computational modeling tools and approaches to probe interfaces between plastics and catalysts in complex environments. The investigators will also address how key plastic additives and contaminants complicate the interfacial chemistry, using technoeconomic analysis to identify the most important opportunities for reducing upcycling cost and environmental impact. The project will lead to cross-disciplinary training of a diverse group of students in plastic waste conversion technology. Faculty and students on the project will engage in multiple forms of outreach, including both in-person workshops aimed at K-12 school children and development of electronic resources aimed at life-long learners. The overall goal of this project is to develop technologies that allow simultaneous or sequential processing of mixed plastic wastes to desirable monomers. Achieving this goal will require understanding how polymer deconstruction is influenced by different polymer, monomer, catalyst, and gas phases, as well as by the presence of plastics additives and contaminants. The proposed work will identify ways to manipulate the interactions between the various components and phases to achieve efficient deconstruction of single plastics components and binary mixtures of condensation polymers and polyolefins. Catalytic hydrogenolysis will be employed as a robust technique for deconstruction of diverse plastics, using both simultaneous (one-pot) and sequential depolymerization of plastic mixtures. Methods for controlling the reaction environment will be investigated by an interdisciplinary team of researchers with expertise in natural polymers deconstruction, chemical catalysis, advanced in situ characterization, materials synthesis and surface modification, and computation. The transformative aspect of the research lies in the focus on multiphase reaction engineering, with an explicit focus on both reaction kinetics and mass transfer limitations in catalytic plastics deconstruction. Experimentally validated models will be used in conjunction with techno-economic analysis to design processes that convert mixtures of waste plastics to valuable monomers through appropriate synthesis of optimal catalysts, temperature programs, and reactor designs. The methods for studying polymer-catalyst interfaces can be applied beyond the hydrogenolysis and will be useful in addressing fundamental science problems related to the interaction of macromolecules with catalytic materials.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.