CAREER: Thermophysical Effects of Sub- and Supercritical CO2 on Plastics and Their Impact on Catalytic Hydrocracking Pathways

More than 6 million metric tons of polypropylene (PP) is produced annually in the U.S. It is the second most produced plastic in the U.S. Less than 1% of this PP is recycled because common recycling methods are inefficient and often produce low-quality material. Instead of recycling PP, a special chemical process with catalysts can break down PP into useful products, turning plastic waste into valuable materials. However, when PP melts, it becomes thick and sticky, which makes it hard to heat and mix evenly during processing. This CAREER project will study how carbon dioxide at certain temperatures and pressures (called subcritical and supercritical conditions) can help make melted PP less thick and easier to process. By examining how carbon dioxide changes the properties of different types of PP during these reactions, the research will develop better technologies for reducing plastic waste. The project will also include hands-on lessons for middle school students in Kansas to teach them about reducing plastic waste and inspire interest in science and engineering. This CAREER project will investigate how subcritical and supercritical carbon dioxide-containing media influence the catalytic conversion of structurally diverse polypropylene (PP) substrates, using catalytic hydrocracking as a model system to elucidate the underlying reaction and transport mechanisms. The study will systematically evaluate how carbon dioxide at varying temperatures and pressures modifies PP thermophysical properties and how these changes affect reaction kinetics, pathways, product selectivity, and coke formation and deposition within catalyst pores. In addition, the project will examine how variations in PP characteristics - such as molar mass, degree of branching, and tacticity - govern the extent to which subcritical and supercritical carbon dioxide alter reaction rates, selectivity, and catalyst recyclability. These insights are critical for rigorously defining the role of carbon dioxide as a reaction medium and for overcoming transport limitations in catalytic plastic upcycling. The resulting mechanistic and methodological framework is expected to be broadly applicable to other catalytic systems, including hydrogenolysis and pyrolysis, as well as to other highly viscous or structurally complex feedstocks that exhibit transport limitations, such as lignocellulosic biomass. 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. NSF Award ID: 2543124 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Ana Colaco Morais | Institution: University of Kansas Center for Research Inc, LAWRENCE, KS | Award Amount: $500,000 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2543124 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2543124.html