Collaborative Research: Elucidation of descriptors that control heterogeneous olefin metathesis site creation through reduction

Tulane University, New Orleans LA

Investigators

Abstract

Plastics are everywhere in our daily lives, but disposing of them responsibly is a huge challenge. Making new plastics and fuels from petroleum uses large amounts of energy and generates greenhouse gases. A promising solution to both problems is to convert waste plastics or renewable materials into useful chemicals using a special kind of chemical reaction called olefin metathesis. Olefin metathesis is a catalytic reaction that takes two molecules, cuts them each in half, and stitches them back together so that the two new molecules are made from half of each of the starting molecules. For olefins such as ethylene and propylene, this is an important pathway to make precursor molecules that are incorporated in to polymers and plastics that everyone uses. Metathesis reactions are enabled solid catalysts containing W and Mo metals; however, while these materials work well, how they function during the reaction is not well understood. This collaborative project between Oregon State University and Tulane University aims to better understand and improve these catalysts. Efforts will focus on how the catalytic active sites, the place where the chemical reaction occurs, are created. The research team will use a combination of experiments and computer simulations to study how different chemicals, called “soft reductants,” can convert the catalysts from inactive to activate form by changing the oxidation state of metal atoms on their surface. Understanding this process could lead to more effective and reusable catalysts for turning plastic waste or renewable materials into valuable products. This project will discover specific ways to control the process of creating active sites through the lens of reductive chemistry. Preliminary work shows how the activity of a catalyst can be increased several thousand fold, with tunable populations based on the structure of a reducing agent. Techniques and tools like custom gas phase reactors, temperature programmed studies, in-situ and operando spectroscopy using DRIFTS, Raman, UV-Vis, ambient-pressure x-ray photoelectron spectroscopy (AP-XPS) will be closely integrated with computation. These tools will help identify the features of the reductant and the mechanistic steps needed to create and maintain the activity of these catalysts. The results of this research will not only improve olefin metathesis but also benefit other chemical processes that depend on similar catalysts, such as creating renewable plastics, fuels, and other materials. The project will support training of future scientists and engineers and develop innovative educational tools, including virtual reality experiences and methods to 3D-print educational models of catalysts, to make this complex science more accessible and engaging for students and researchers alike. 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.