Scientists at Washington State University have taken a major initial step toward the affordable conversion of plant materials into fuels—preventing iron from rusting.
They have found out how to prevent iron from rusting in key chemical reactions required to transform plant materials to fuels, implying that the low-cost and readily available element could be utilized for economical biofuels conversion.
Under the guidance of Yong Wang, Voiland Distinguished Professor in the Gene and Linda Voiland School of Chemical Engineering and Bioengineering, and Shuai Wang from the State Key Laboratory for Physical Chemistry of Solid Surfaces at Xiamen University, the team has described the study on the cover of the July issue of ACS Catalysis.
Scientists have been attempting to identify more efficient methods to make chemicals and fuels from renewable plant-based resources, for example, from crop waste, algae, or forest residuals.
However, such bio-based fuels are more costly and exhibit less energy density compared to fossil fuels. A major obstacle in the use of plant-based feedstocks for fuel is the need to eliminate oxygen from them before they are put to use.
You want to use the cheapest catalyst to remove the oxygen. Iron is a good choice because it’s super abundant.
Jean-Sabin McEwen, Study Co-Author and Associate Professor, Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University
Iron-based catalysts exhibit great potential to eliminate oxygen. However, since the plant materials also include oxygen, the iron tends to get oxidized, or rusts, at the time of the reaction, following which the reaction tends to stop. The clue is to make the iron to eliminate the oxygen from the plants without using so much oxygen that the reaction terminates.
In the study, a carbon structure altered to hold nitrogen was used to anchor the iron catalyst.
The properties of the iron are modified by the structure so that it interacts less with oxygen while it still performs the essential work of eliminating oxygen from the plant material. The nitrogen was used as a kind of control dial to tweak the interaction of iron with oxygen.
In another paper recently published in the Chemical Science journal and led by Yong Wang and Junming Sun, a research assistant professor in the Gene and Linda Voiland School of Chemical Engineering and Bioengineering, the research team found a strong iron-based catalyst with a thin carbon graphene layer around it.
The graphene layer shielded the iron while cesium ions enabled the team to customize its electronic properties for the preferred reaction.
We dialed down the oxygen reaction. By protecting iron and tuning its properties, these works provide the scientific basis for using earth abundant and cost-effective iron as catalysts for biomass conversion.
Junming Sun, Research Assistant Professor, Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University
Currently, the team is working to gain better insights into the chemistry of the reactions, which would help them further enhance the reactivity of the iron catalysts. They must also try their catalysts with real feedstocks rather than the model compounds that have been utilized for the study.
The feedstocks gathered from farm fields will be more complex in their compositions, including a lot of impurities, and the team must also integrate their catalyst into a range of steps employed in the process of conversion.
We are trying to make the conversion as economically as possible. The key is trying to find robust catalysts based on low-cost, earth abundant elements. This is a first step in that direction.
Yong Wang, Voiland Distinguished Professor, Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University
The study was financially supported by the National Science Foundation and the Department of Energy.
Yang, Y., et al. (2020) Controlling the Oxidation State of Fe-Based Catalysts through Nitrogen Doping toward the Hydrodeoxygenation of m-Cresol. ACS Catalysis. doi.org/10.1021/acscatal.0c00626.