Stowers Laboratory Research
The Stowers laboratory takes an interdisciplinary approach towards research of carbon dioxide activation and reactivity through principles of inorganic, physical and organic chemistry. Our interest is in developing new catalysts that will decrease the energy and waste required to synthesize commodity chemicals through new pathways. Some commodity chemicals of interest are using CO2 to form esters or alcohols, as well as using bio-based feedstocks, such as glycerol, as alternative starting points to get to these products. Determining the principles necessary for the activation of CO2 towards C-C bond formation will be achieved using a variety of tools and techniques.
Using Carbon Dioxide as a Feedstock
Carbon dioxide is an undesired byproduct of combustion. Finding ways to manage and use carbon dioxide is an important strategy for keeping emissions low without affecting the economy. Although it is often seen as kinetically unreactive, recently a number of catalysts have been shown to overcome this barrier for the production of higher-value chemicals. Glycerol is another waste stream that has a high density of functionality that can be converted to platform chemicals such as propanediols, allyl alcohol and propylene. Catalyst selectivity and efficiency are paramount for maximizing the conversion of glycerol.
Inorganic synthesis of Heterogeneous Catalysts
Heterogeneous catalysts can provide good separation from the starting materials and products thus decreasing waste. Synthesizing and characterizing new nanoparticle and supported catalysts allow us to determine how reagents interact with the surface and ultimately react to form products. One strategy for synthesizing small nanoparticles is through the use of templates such as metal organic frameworks or MOFs. These can be pyrolized to obtain small nanoparticles within a carbon matrix. We study a variety of metal catalysts including Ni, Cu, Cr and Mn among others for oxidation reactions such as oxidative dehydrogenation and alcohol oxidation. Students working on these projects synthesize inorganic catalysts, determine the catalyst structure by X-ray crystallography, scanning electron microscopy (SEM) and XPS, and test the catalysts for catalytic activity in organic reactions.
Gas-phase Reactivity of Carbon Dioxide
Large amounts of CO2 are produced every year through modern agricultural and industrial developments. These large amounts of environmentally unfriendly gases have created the need for CO2 capture or conversion into less harmful byproducts. Recent research has shown CO2 to be a good soft-oxidant, allowing CO2 to be implemented in a process called oxidative dehydrogenation, a reaction which converts alkanes into alkenes and CO2 into H2O and CO. Alkenes are important organic compounds in modern synthesis that are typically created through fossil fuel cracking and steam treatment, two environmentally detrimental products. We are focusing on improving promising catalysts to decrease the energy needed in this reaction and to increase selectivity to alkenes.
Ethane can react with oxygen to form the olefin ethylene, water, and carbon dioxide. Ethylene is a desirable product, as it is used to make common plastic products. Nickel oxide supported on alumina (aluminum oxide) provides a successful catalyst for this reaction, and is selective to ethylene over carbon dioxide as a product. We hope to fully develop and characterize a catalyst for this reaction that will work at low temperatures. Catalyzing this reaction at low temperatures will allow for the more economic production of ethylene in industry.
Mechanistic Studies on Catalyst Surfaces
Heterogeneous catalysts are becoming easier to study with new spectroscopy techniques that allow characterization of the mechanism at the surface of the material. The goals of this project will be to study catalysts in ultra-high vacuum in order to understand active sites, activation, deactivation and poisoning. We also use and study intermediates of reaction mechanisms in efforts to optimize and develop catalysts and reactions for C-C bond formation using carbon dioxide. Students working on this project will analyze reactions on catalysts surfaces via in-situ X- ray photoelectron spectroscopy (XPS) and temperature-programmed reaction spectroscopy (TPRS) in ultra-high vacuum and develop new reactions.