FMSG: ECO: Towards Circular Manufacturing of Hydrocarbon Feedstocks from Plastic Waste

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Plastics present our society with a complex dilemma. We can efficiently and inexpensively produce a fantastic array of polymer products, yet the resulting waste is one of the greatest environmental challenges of our time. It also presents an enormous opportunity for manufacturing; there are literally millions of tons of reduced carbon feedstocks going to landfills and waterways every year. If our plastic waste could be converted into a more processible form and we if we could find markets large enough to accommodate the product materials, we may unlock a wide range of new manufacturing opportunities. The modern petrochemical industry is one of the few markets large enough to accommodate our annual plastic waste. Re-integrating waste plastic into the petrochemical supply chain would take advantage of enormous economies of scale and develop a circular plastics economy while simultaneously reducing our annual petroleum consumption. This project seeks to address this problem by developing the fundamental chemistry, engineering, and economics needed to convert waste plastic into “poly-crude”, a material that can be dropped into the existing petrochemical supply chain. A complementary techno-economic analysis will help direct the project towards economically viable products and process considerations. This impact is further buoyed by an integrated workforce development plan that aims to broaden participation by recruiting future scientists and engineers from underrepresented groups, while also providing interdisciplinary research and leadership training that will ensure their success in future manufacturing roles. Through this fundamental science, we will help to train a wide range of the future workforce (graduate students, undergraduates, and high school students) in the technical and critical thinking skills necessary for 21st century manufacturing. This work seeks to develop the fundamental chemistry and engineering to help develop a plastics manufacturing platform by which plastic waste is converted to valuable chemical feedstocks. Benefits include alleviating demand on natural petrochemical resources, enabling future manufacturing based upon a circular plastics economy, and addressing critical societal, environmental, and economic needs. Catalytic methods using polymer melts are encumbered by slow diffusion and process inefficiencies associated with batch reactors. This project aims to elucidate the fundamental thermodynamic factors inherent in competitive transport and size-selective adsorption of polyolefins on metal oxide catalysts. Using (i) size-specific polyolefins, (ii) neutron scattering techniques, and (iii) competitive adsorption measurements in flow reactors, we will develop adsorption models that will help us probe the deeply interconnected polymer-solvent-surface interactions that govern competitive adsorption in these systems and drive polymer adsorption from solution to favor longer chain polymers. This will, in turn, be used to improve both catalytic activity and selectivity, as it will provide a means of getting around critical mass transport barriers by dissolving polyolefins in appropriate hydrocarbon solvents and employing flow reactors to study polyolefin adsorption onto catalyst surfaces from solution. Isotopic substitution and advanced neutron scattering techniques to distinguish between different polymers and solvents provide compelling advantages. Understanding these interrelated factors will allow us to develop the fundamental knowledge necessary to design processes (temperature, solvent, catalyst) that minimize the production of low-value products during catalytic hydrocracking of plastic waste streams. By controlling these parameters, we postulate selective polymer adsorption on a catalytic surface can be intelligently biased to control the product distribution. This Future Manufacturing award was supported by co-funding from the Chemical, Biological, Environmental Engineering and Transport Systems and the Civil, Mechanical and Manufacturing Innovation Divisions in the Directorate for Engineering and the Division of Chemistry in the Directorate for Mathematical and Physical Sciences.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.