SusChEM: Surface Active Site Design for Selective Deoxygenation

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

Many chemical processes require the ability to make or break carbon-oxygen bonds in a compound without affecting other bonds. The conversion of biomass to fuels and chemicals requires carbon-oxygen bond dissociation (or "deoxygenation") reactions to improve the compatibility of biomass-derived compounds with the existing refining infrastructure. Unfortunately, catalysts that are effective for deoxygenation also often catalyze other, undesired reactions that lead to the loss of carbon. The ability to design solid materials that specifically remove oxygen from a feedstock is thus a goal of modern catalysis research. In this project, Dr. J. Will Medlin of the University of Colorado Boulder is investigating how interactions between oxygen-containing reactants on catalyst surfaces can be tuned to allow for specific removal of oxygen from a feedstock. Dr. Medlin is also investigating the role that catalyst nanostructure plays in favoring oxygen removal reactions over those that remove carbon. The project integrates scientific outreach and training within the research program. These outreach activities include summer research opportunities for undergraduate students, as well as expansion of an annual chemistry and chemical engineering "Field Day" activity that is focused on hands-on science experiments for middle school students. With funding from the Chemical Catalysis Program of the Chemistry Division, Dr. J. Will Medlin of the University of Colorado Boulder is developing an understanding of the mechanism for deoxygenation reactions of alcohols on metal surfaces. Selective activation of carbon-oxygen bonds is important in many applications, including the conversion of biomass-derived compounds to fuels and chemicals. It is especially important to identify catalysts that are selective for carbon-oxygen bond activation, since cleavage of carbon-carbon bonds generally results in carbon loss and reduced efficiency. Although certain metal surfaces have been identified as being unusually active and selective for deoxygenation, the relationship between surface properties and deoxygenation performance is not well understood, hampering efforts to design improved catalysts. In this project, Dr. Medlin is employing a combination of experimental studies using model surfaces, density functional theory calculations, and experiments with supported catalysts to systematically investigate factors that have previously been associated with high deoxygenation selectivity. In this project, isotope tracing studies are employed to systematically investigate the mechanism for the critical hydrogen transfer step during deoxygenation. Deoxygenation selectivity and kinetics are measured for a variety of palladium surfaces to identify the geometric structures associated with efficient deoxygenation. The goal of this project is to identify simple catalyst descriptors that can inform design of efficient catalysts. This project emphasizes STEM education through the research training of students across multiple levels, as well as through an annual "Field Day" activity for middle school students organized by Dr. Medlin's group.