Designing and characterizing highly selective heterogeneous catalysts for hydrodeoxygenating bio-oils

Barnard College, New York NY

Investigators

Abstract

The majority of waste streams, including industrial timber by products and municipal solid waste, are generally environmentally and economically burdensome; yet they have the potential to serve as starting materials from which fuels, medicines and other consumer products can be made. However, a number of chemical reactions are required to transform these waste materials into something useful. Among the most challenging chemical changes needed are reactions that remove excess oxygen atoms from the waste material. Our team designs catalysts, materials that aid in a reaction by improving speed, selectivity and/or energy requirements, but do not themselves become consumed in the reaction. We are actively developing, characterizing and testing catalysts that use hydrogen gas to remove excess oxygen from oils made from these waste streams. Our team combines expertise in making catalysts and controlling their structure at the molecular level, identifying the type of reaction products that result, optimizing the reactor process for greater efficiency, and theoretical modeling to understanding the behavior of solid catalysts and the reactions they control. Together, we are able to design and study a wide range of catalysts selected to test specific ideas about how optimal catalysts for this reaction work and also to lead us towards the design of better and more environmentally friendly catalysts that use earth-abundant metals. Broader impacts of the research include environmental benefits of eliminating waste and economic benefits of producing a chemical fuel and feedstock source from waste products. All members of our team are committed to diversifying the scientific workforce and are engaged in activities to recruit and retain in our laboratories members of groups historically underrepresented in scientific fields. We engage in active curriculum reform, and cases drawn from current scientific efforts to improve the sustainability of energy production form the foundation of the newly redesigned General Chemistry course at Barnard College, an all-women's college in New York City. In this research program, Drs. Austin, Frederick, Grabow, and Schwartz are supported by the Macromolecular, Supramolecular and Nanochemistry Program at NSF to test the hypothesis that catalytic materials suitable for highly selective hydrodeoxygenation (HDO) reactions that cleave C-O bonds require: (1) a metal that can adsorb and split H2; and (2) an amphoteric support that can serve as a proton shuttle from the metal to the substrate to weaken the C-O bond. If confirmed, the results from this work could alter the current paradigm invoking support reducibility rather than its amphoteric character. A series of supported metal catalysts is being synthesized and characterized using a variety of experimental and computational methods. These catalysts are used to catalyze HDO reactions of phenol-derived model compounds, including some isotopically-labeled substrates, with hydrogen gas. The products of the HDO reactions are analyzed by gas chromatography-mass spectrometry (GC-MS) measurments. Density functional theory (DFT) is used to calculate reaction energy profiles, which are then compared to experimental data to propose detailed catalytic reaction mechanisms. Broader impacts of the research include environmental benefits of eliminating waste and economic benefits of producing a chemical fuel and feedstock source from waste products. Student exchange between four very different labs: a computational lab at the University of Houston, a chemical engineering lab and a physical chemistry lab both at the University of Maine, and an inorganic catalysis lab at an all women's liberal arts college in New York City, will facilitate the broad development of students working on this project. Significant curriculum development, using cases from this work and from other research on sustainable energy development, forms the basis of a problem-based general chemistry course that serves approximately 150 female Barnard College students each year.