Tailoring polyethylene ethenolysis to obtain higher alpha-olefins

Polyethylene is a common and useful plastic. It is an inexpensive material that is manufactured, used, and discarded in vast quantities every year. This project aims to find a new way to recycle waste polyethylene by adding enough value for recycling to be economically viable at scale. The aim is to disassemble long polyethylene molecules into much smaller molecules that can be used as chemical building blocks. The challenge is to use a carefully timed sequence of chemical reactions to break some of the strong bonds in polyethylene molecules selectively. The speed at which each reaction proceeds must be known and controlled so that the various steps work seamlessly together. The speed of each reaction will be controlled by designing a catalyst that directs the reactions and the rates at which they proceed. The resulting knowledge will allow polyethylene to be converted into molecules whose intrinsic value to the chemical industry will pay for collection, sorting, and processing of waste plastic. The project will target molecules used to make new plastics, lubricants, motor oils, and surfactants. The project will investigate the empirical and microkinetic rate laws for the two key steps in polyethylene disassembly to higher olefins: olefin metathesis and olefin isomerization. The relative rates of these two reactions determine the average chain length of the product olefins. Both reactions will be catalyzed simultaneously by a bifunctional heterogeneous catalyst. Kinetic profiles will be recorded to extract reaction orders, rate constants, and activation barriers for productive and unproductive reaction steps, using global analysis. Multiparameter models will be built and tested to identify and predict the conditions (e.g., pressure, temperature, catalyst concentration) for selective polyethylene depolymerization to olefins of any desired chain length. The predictions will be tested by performing the reaction and assessing the product distribution, and the results will be used to further refine the model. 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: 2533904 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Susannah Scott | Institution: University of California-Santa Barbara, SANTA BARBARA, CA | Award Amount: $470,000 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2533904 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2533904.html