A refueling oiler, on the left, fuels a naval ship at sea. The University of Rochester Porosoff research group has shown that a potassium-promoted molybdenum carbide catalyst can help the US Navy achieve its goal of converting seawater into fuel, effectively eliminating the need from traditional refueling operations. Credit: US Navy
For the first time, Rochester chemical engineers have demonstrated the potential of a ‘potassium promoted’ catalyst for use on an industrial scale.
Now, the Navy’s quest to propel its ships by turning seawater into fuel is closer to fruition.
This OxEon Energy reactor was used to validate the effectiveness of the potassium promoted molybdenum carbide catalyst on an industrial scale. Credit: OxEon Energy
Chemical engineers at the University of Rochester, in collaboration with researchers from the Naval Research Laboratory, the University of Pittsburgh, and OxEon Energy, have shown that a potassium-promoted molybdenum carbide catalyst efficiently and reliably converts carbon dioxide into carbon monoxide, a critical step in turning seawater into fuel.
“This is the first demonstration that this type of molybdenum carbide catalyst can be used on an industrial scale,” says Marc Porosoff, an assistant professor in the Rochester Department of Chemical Engineering. In an article in the newspaper Energy and Environmental SciencesThe researchers describe an exhaustive series of experiments they conducted on a molecular, laboratory, and pilot scale to document the suitability of the catalyst for amplification.
If navy ships could create their own fuel from the seawater they travel through, they could remain in continuous operation. In addition to a few nuclear-powered aircraft carriers and submarines, most navy ships must periodically line up alongside tankers to replenish their fuel, which can be difficult in adverse weather conditions.
In 2014, a team from the Naval Research Laboratory led by Heather Willauer announced that it had used a catalytic converter to extract carbon dioxide and hydrogen from seawater, and then converted the gases to liquid hydrocarbons at an efficiency rate of 92 percent.
Since then, the focus has been on increasing the efficiency of the process and expanding it to produce fuel in sufficient quantities.
A key step in the process of converting seawater into fuel
Carbon dioxide extracted from seawater is extremely difficult to convert directly to liquid hydrocarbons with existing methods. Therefore, it is necessary to first convert carbon dioxide to carbon monoxide through the reverse water-gas exchange reaction (RWGS). Carbon monoxide can be converted to liquid hydrocarbons through the Fischer-Tropsch synthesis.
Madeline Vonglis ’20, who did an internship with Porosoff’s research group last summer, conducted many of the laboratory-scale experiments to characterize the potassium-promoted molybdenum carbide catalyst, and is the second author in the article by Energy and Environment Science. She will begin her doctorate in chemical engineering this fall at Pennsylvania State University. Credit: University of Rochester / J. Adam Fenster
Typically, RWGS catalysts contain expensive precious metals and are rapidly deactivated under reaction conditions. However, the potassium modified molybdenum carbide catalyst is synthesized from low-cost components and showed no signs of deactivation during the continuous operation of the 10-day pilot scale study. That is why this demonstration of the molybdenum carbide catalyst is important.
Porosoff, who began working on the project while working as a postdoctoral researcher associated with the Willauer team, found that adding potassium to a molybdenum carbide catalyst supported on a gamma alumina surface could serve as a low-cost, stable, and highly selective. to convert carbon dioxide to carbon monoxide during RWGS.
Potassium reduces the energy barrier associated with the RWGS reaction, while grooved and pored, sponge-like gamma alumina helps ensure that molybdenum carbide catalyst particles remain dispersed, maximizing the surface area available for the reaction, says Porosoff.
To determine if potassium-promoted molybdenum carbide could also be useful for capturing and converting carbon dioxide from power plants, the research group will conduct further experiments to test the stability of the catalyst when exposed to common contaminants found in combustion gases such as mercury, sulfur, cadmium, and chlorine.
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Reference: “Assessing the Feasibility of K-Mo2C for Reverse Expansion of Water-Gas Change: Molecular to Laboratory at Pilot Scale” by Mitchell Juneau, Madeline Vonglis, Joseph Hartvigsen, Lyman Frost, Dylan Bayerl, Mudit Dixit, Giannis Mpourmpakis , James R. Morse, Jeffrey W. Baldwin, Heather D. Willauer and Marc D. Porosoff, July 7, 2020, Energy and Environmental Sciences.
DOI: 10.1039 / D0EE01457E
Rochester’s co-authors include lead author Mitchell Juneau, a PhD student in Porosoff’s research group, and Madeline Vonglis ’20, a former undergraduate researcher.
An award from the Office of Naval Research supported this project.
