Low-cost catalyst helps turn seawater into fuel at scale

Date:
July 15, 2020
Source:
University of Rochester
Summary:
The Navy's quest to power its ships by converting seawater into fuel
is one step nearer fruition. Chemical engineers have demonstrated
that a potassium-promoted molybdenum carbide catalyst efficiently
and reliably converts carbon dioxide to carbon monoxide, a critical
step in the process.



FULL STORY ==========================================================================
The Navy's quest to power its ships by converting seawater into fuel is
one step nearer fruition.


========================================================================== University of Rochester chemical engineers, in collaboration with
researchers at the Naval Research Laboratory, the University of
Pittsburgh, and OxEon Energy, have demonstrated that a potassium-promoted molybdenum carbide catalyst efficiently and reliably converts carbon
dioxide to carbon monoxide, a critical step in the process.

"This is the first demonstration that this type of molybdenum carbide
catalyst can be used on an industrial scale," says Marc Porosoff,
assistant professor of chemical engineering at Rochester. In a paper in
Energy & Environmental Science, the researchers describe an exhaustive
series of experiments they conducted at molecular, laboratory and pilot
scales to document the catalyst's suitability for scale-up.

If Navy ships could create their own fuel from the seawater they travel through, they could remain in continuous operation. Other than a few
nuclear- powered aircraft carriers and submarines, most Navy ships must periodically align themselves alongside tanker ships to replenish their
fuel oil, which can be difficult in rough weather. In 2014, a Naval
Research Laboratory team led by Heather Willauer announced it had used a catalytic converter to extract carbon dioxide and hydrogen from seawater
and then converted the gases into liquid hydrocarbons at a 92 percent efficiency rate.

Since then the focus has been on increasing the efficiency of the process
and scaling it up to produce fuel in sufficient quantities.

The carbon dioxide extracted from seawater is extremely difficult to
convert directly into liquid hydrocarbons with existing methods. So,
it is necessary to first convert carbon dioxide into carbon monoxide via
the reverse water-gas shift (RWGS) reaction, which can then be converted
into liquid hydrocarbons via Fischer-Tropsch synthesis (FTS). Typically, catalysts for RWGS contain expensive precious metals and deactivate
rapidly under reaction conditions.

However, the potassium-modified molybdenum carbide catalyst is synthesized
from low-cost components and did not show any signs of deactivation
during continuous operation of the 10 day pilot-scale study.

That's why this demonstration of molybdenum carbide catalyst is important.

Porosoff, who first began working on the project while serving as a postdoctoral research associate with Willauer's team, discovered that
adding potassium to a molybdenum carbide catalyst supported on a surface
of gamma alumina could serve as a low-cost, stable, and highly selective catalyst for converting carbon dioxide into carbon monoxide during RWGS.

The potassium lowers the energy barrier associated with the RWGS reaction, while the gamma alumina -- marked with grooves and pores, much like a
sponge - - helps ensure that the molybdenum carbide catalyst particles
remain dispersed, maximizing the surface area available for reaction,
Porosoff says.

To determine whether potassium-promoted molybdenum carbide might also
be useful for capturing and converting carbon dioxide from power plants,
the lab will conduct further experiments to test the catalyst's stability
when exposed to common contaminants found in flue gas such as mercury,
sulfur, cadmium and chlorine.


========================================================================== Story Source: Materials provided by University_of_Rochester. Original
written by Bob Marcotte. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Mitchell Juneau, Madeline Vonglis, Joseph Hartvigsen, Lyman Frost,
Dylan
Bayerl, Mudit Dixit, Giannis Mpourmpakis, James R. Morse, Jeffrey W.

Baldwin, Heather D. Willauer, Marc D. Porosoff. Assessing the
viability of K-Mo2C for reverse water-gas shift scale-up: molecular
to laboratory to pilot scale. Energy & Environmental Science,
2020; DOI: 10.1039/ d0ee01457e ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200715123120.htm

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