J. Will Medlin
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I’m working to develop selective metal oxide catalysts for solid acid catalysis. I’m using two strategies to impact selectivity: 1) poisoning either Bronsted or Lewis acid sites, and 2) coating catalysts with self-assembled monolayers. My current project is focused on the dehydration of glycerol, a byproduct in the production of biodiesel, to acrolein, a polymer precursor that could be made into materials such as diapers.
My research focuses on improving the selectivity of supported metal catalysts by modifying them with alkanethiol self-assembled monolayers (SAMs). Alkanethiol modified catalysts have been shown to dramatically increase the hydrogenation selectivity of 1-epoxy-3-butene, fatty acids, and a,b-unsaturated aldehydes through a combination of ligand specific and non-specific modifications to the near surface environment. Current work is focused on rational design of supported metal catalysts by tuning the surface modifiers to meet specific reaction goals.
Transition metal surfaces are widely used to catalyse chemical transformations, but designing or screening surfaces is difficult. Since adsorption strength is a good predictor of catalytic performance, my work focuses on understanding and predicting adsorption strength to aid in catalyst design.
Biomass pyrolysis is an attractive route for renewable fuel and chemical production but it results in a complex mixture of multifunctional oxygenates. Selective deoxygenation reactions are critical to upgrading of these compounds. Using bimetallic catalysts containing a hydrogenation metal and oxophilic metal modifier have shown promising selectivity for these reactions. We are using a combination of surface science techniques as well as heterogeneous catalysis studies to better understand this bimetallic system to make improved materials for biomass upgrading applications.
Recent work in the group has showed that alkanethiol self-assembled monolayers (SAMs) can be applied to catalyst modification, which dramatically improved the reaction selectivity. Basically, these reactions were low temperature hydrogenation of oxygenated compounds. Based on previous work, my research will explore the performance of SAMs in harsher environments, especially under oxidizing conditions.
The goal of my research is to investigate the effect of thiol SAM-coated palladium on the reaction of molecules with multiple functional groups. The results will contribute to an understanding of the effect of SAMs on catalysts and help develop catalysts with high selectivity.
My research focuses on utilizing adsorption/surface orientation as a means of controlling reaction selectivity of biomass-derived molecules such as furfural on Pd surfaces and catalysts. Control of surface orientation can be achieved through catalyst surface modification or alloying with less reactive metals.
Catalytic oxidation reactions on transition metals often occur in the presence of molecular oxygen, but oxygen’s surface-level effects on complex reactants have yet to be explored. My work includes using surface science techniques (TPD, HREELS) to understand the effects of oxygen on these mechanisms when they take place on palladium catalysts. The complex reactants of interest are biomass-derived intermediates such as aromatic alcohols and aldehydes.
Spring 2014 commencement
Self-assembled monolayers (SAMs) have been shown to improve catalytic performance in several cases, but questions about their stability remain. April's work focuses on understanding and improving the stability of SAMs.
(Now at Intel) The aim of Carolyn's research is to develop synthetic catalysts with a biomimetic surface environment in order to achieve desired selectivity outcomes for practical applications. The strategy involves varying thiol self-assembled monolayers to tune the near-surface environment on supported catalysts. Preliminary results suggest that alkanethiols provide a favorable environment for selective binding of nonpolar functional groups. Longer Description.
(Now at the Boston Museum of Science) Understanding proton behavior at interfaces is critical to the development of several electrochemical devices, such as batteries, fuel cells, and sensors. One aspect of this project focuses on studying how various factors of the electrocatalytic interface influence reactions, such as the oxygen reduction reaction and the hydrogen oxidation reaction, that take place on this surface. This research utilizes High Resolution Electron Energy Loss Spectroscopy (HREELS) and Density Functional Theory (DFT) as a two-pronged experimental and theoretical approach to studying this complex interface. The second aspect of this project focuses on understanding proton behavior in yttrium-doped barium cerate (BCY), a perovskite material that exhibits extremely rapid proton conduction. Using DFT we will study BCY hydration and model the basic mechanism of proton transport within and at the interface of this material.
(Now at Intel) The goal of my research is to identify sulfur resistant Ni catalysts for the reforming of biomass tars. We use density functional theory to identify sulfur resistant Ni bimetallic catalysts. The theoretical results are validated by studying syngas reforming over these bimetallic catalysts in a packed bed reactor system. We characterize the reduced and post reaction catalyst samples using to various techniques -TPR, SEM, EXAFS and XRD - to understand the surface structure and catalyst behavior.
(Now at Cree) To develop catalysts for the production of advanced biofuels, we must further understand the relationship between physical catalysts properties & reactivity. Current research is focusing on understanding the role of facets or defects of Ni catalysts in the activity and selectivity of hydrogenolysis of biofuel molecules. Synthesizing smaller catalysts particles can induce these defects, and so current efforts are aimed at using novel techniques to create & control the size of catalyst particles & relate these induced defects to catalytic activity.
(Now at the National Renewable
Energy Lab) Mike's work focuses on understanding the interactions between polyols and palladium surfaces. Polyols can be derived from biomass and converted into a variety of useful products such as fuels, pharmaceuticals, and chemicals. Understanding how they react on metals such as palladium provides the insight necessary to develop highly active and selective catalytic systems.
(Now at Phillips 66) Steve's work explores the use of self-assembled monolayers (SAMs) formed from alkanethiols to improve the selectivity of catalytic materials. We have used SAMs to improve chemoselectivity in the conversion of unsaturated epoxides that can be derived from biomass and to improve the detection of transformer fault gases by metal-insulator-semiconductor sensors. This work incorporates aspects of numerous fields including heterogeneous catalysis, surface science, and chemical sensing.