CAS: Deconstructing Mixed Plastic, Biomass and Food Waste via Organosulfur Chemistry

With the support of the Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry, Dr. Rhett C. Smith of Clemson University will investigate a new method for converting agricultural and plastic waste into useful materials through a process called thiocracking, where sulfur and heat are used to break down organic molecules. This research will address challenges in waste disposal, including plastics, agricultural residues, and mixed-material waste, while using excess sulfur, a byproduct of fossil fuel refining. Thiocracking could transform these waste streams into recyclable materials for construction and infrastructure, reducing landfill waste, and benefiting the U.S. economy. The project will also support education by training graduate and undergraduate students, collaborating with primarily undergraduate institutions, and sharing findings with the public through social media and open-access publications where possible. The project will specifically explore a two-step thiocracking-desulfurization sequence to break down complex waste streams and recover valuable organic products. In the first step, thiocracking will be used to induce depolymerization and conversion into polymeric composites. These composites will then be assessed for mechanical properties and recyclability, with a focus on their potential applications as structural materials. The second step will employ catalytic hydrodesulfurization to remove sulfur and recover hydrocarbons. This process will be optimized for catalyst performance, reaction conditions, and product distribution. Mechanistic studies will provide insight into sulfur-carbon bond formation / cleavage, advancing the fundamental understanding of thiocracking chemistry. If successful, this research would lead to an innovative, energy-efficient, and scalable strategy for repurposing waste plastics and biomass, offering a transformative solution to waste management through chemistry and materials science. 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.