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Summer 2019

A Whole New World of Catalysts

Uncovering new oxygen-removing catalysts using a toolkit created from one catalyst

Elvis Ebikade

To turn corn stover or other biomass into fuels, you need to upcycle furfural to 2 methylfuran. Scientists delved into how ruthenium oxide catalyst works and extrapolated their findings to determine the most promising catalysts. Image courtesy of Nathan Johnson, Pacific Northwest National Lab

Ever tried baking bread? You need flour, sugar, butter and a baking pan. However, if no yeast is added, the bread doesn’t rise! A catalyst within yeast  converts the sugars in flour to carbon dioxide that fills thousands of balloon-like bubbles in the dough, giving the loaf its airy texture. In that vein, catalysts are materials that speed up the rate of a reaction that otherwise would take an extraordinarily long time to occur

A class of catalysts called metal oxides excel at breaking carbon-oxygen bonds found in plant-based feedstock such as corn stover and fast-growing plants like grass. However, the challenge with the molecules from these plants is that they possess excessive oxygen compared to gasoline or other fuels. Therefore, scientists must break certain carbon – oxygen bonds to remove some of the excess oxygen to upgrade these plant-derived molecules to fuels.

Recently, a catalyst that is composed of the metal ruthenium and oxygen, (RuOx, in this case) split the carbon – oxygen bonds, converting two biomass compounds to precursors for fuels or chemicals: 5-hydroxymethylfurfural and furfural, into 2,5-dimethylfuran and 2-methylfuran (2MF), respectively. Both products can serve as environmentally friendly replacements of gasoline. But the question remains: Could other metal oxide catalysts perform similarly or better?

“Cooking up” the best catalyst

Chemical engineers at the Catalysis Center for Energy Innovation (CCEI) Energy Frontier Research Center have taken on this question and provided a new, improved descriptor to predict the performance of potential catalysts. Exploring diverse catalysts is easier said than done, though, as experimentally synthesizing catalysts can be time consuming. Therefore, researchers at CCEI developed a tool that can predict the properties of new catalysts for this oxygen removal reaction and other reactions. This tool uses the knowledge of a known catalyst material (RuO2), then extrapolates its properties to many others, leading to the discovery of an entire new class of catalysts.

Combining knowledge of catalyst physical properties, experimental data and computer aided modeling, researchers demonstrated that the series of reaction steps using RuO2 for C–O bond breaking is generally applicable over many metal oxides. Their calculations also indicate that the performance of a catalyst depends on its ability to form oxygen vacancies, like empty potholes on the catalyst surface, for trapping molecules for reaction, while remaining stable under the reaction conditions. Too many of these potholes cause the catalyst to lose its activity and become a metal!

A taste of what’s to come

The researchers’ fundamental findings about the need for vacancies on the catalyst surface and their role in the increased reaction rate opens the door to new processes for synthesizing bio-based fuels and chemicals. The properties of different catalysts useful in chemical reactions can be predicted without tedious experiments using knowledge of their formation energy. These research efforts manifest how new catalyst can be discovered by extrapolating fundamental insights established on one catalyst (RuO2). While ruthenium oxide isn’t significantly cheaper than catalysts made from noble metal elements, the work could be extended to other less expensive catalysts that remove oxygen from biomass molecules. Researchers expect these results to guide further developments in catalyst design and inform explorations of new applications of these catalysts.

More Information

Goulas KA, AV Mironenko, GR Jenness, T Mazal, and DG Vlachos. 2019. “Fundamentals of C–O Bond Activation on Metal Oxide Catalysts.” Nature Catalysis 2:269. DOI: 10.1038/s41929-019-0234-6

Acknowledgments

This material is based on work supported as part of the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the Department of Energy (DOE), Office of Science, Basic Energy Sciences. Portions of this work were performed at the DuPont–Northwestern–Dow Collaborative Access Team located at Sector 5 of the Advanced Photon Source, a DOE Office of Science user facility. Several characterization and computations facilities were also instrumental in conducting this work.

About the author(s):

  • Elvis Ebikade is a Ph.D. candidate in chemical and biomolecular engineering at the University of Delaware. He is a member of the Catalysis Center for Energy Innovation (CCEI) Energy Frontier Research Center working under the guidance of Dionisios Vlachos, Director of CCEI. His research focuses on process design and development of novel food waste valorization technologies towards producing bio-based commodity products.

Speeding Up Catalyst Selection

Insights from ruthenium-based oxide catalyst help pick promising options to turn biomass into fuels

To turn corn stover into fuels, scientists need to upcycle furfural. Researchers delved into how ruthenium oxide catalyst works and accurately extrapolated their findings to determine the most promising catalysts for further study. Image courtesy of Nathan Johnson, Pacific Northwest National Lab

It’s a common DIY project on YouTube. Take an ugly outfit, cut it, and stitch it back together into something new. In a way, the same upcycling effort happens in making fuels from designer crops. Scientists cut out oxygen atoms from the starting blocks extracted from the plant matter. To do that, they use a catalyst that speeds up oxygen removal. But which catalyst? That’s a tough question. Chemical engineers at the Catalysis Center for Energy Innovation (CCEI) devised a way to sort through options without expensive and time-consuming lab work. The CCEI team figured out how one popular oxygen-clipping catalyst worked. Then, they found a way to extend their findings to other metal oxide catalysts. They’ve created a way to sort through options to pick out the most promising. The University of Delaware leads CCEI, an Energy Frontier Research Center.

More Information

Goulas KA, AV Mironenko, GR Jenness, T Mazal, and DG Vlachos. 2019. “Fundamentals of C–O Bond Activation on Metal Oxide Catalysts.” Nature Catalysis 2:269. DOI: 10.1038/s41929-019-0234-6

Disclaimer: The opinions in this newsletter are those of the individual authors and do not represent the views or position of the Department of Energy.