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Photocatalyst Splits Tough C-F Bonds

Sept. 28, 2020
Use could reduce cost and energy involved in breaking fluorine-containing compounds

Engineers from Rice University, Houston, and collaborators have created a light-powered catalyst that can break carbon-fluorine (C-F) bonds. The process has potential for applications in high-value chemical transformations, as well as in abatement of chlorofluorocarbon, hydrofluorocarbon and perfluorocarbon pollution, say the researchers.

"The hardest part about remediating any of the fluorine-containing compounds is breaking the C-F bond; it requires a lot of energy," says Naomi Halas, a Rice University engineer and chemist whose Laboratory for Nanophotonics specializes in creating and studying nanoparticles that interact with light.

Based on the antenna-reactor photocatalyst platform technology developed by Halas’ lab, the catalyst uses tiny spheres of aluminum speckled with palladium to break C-F bonds via hydrodefluorination, a catalytic process that replaces a fluorine atom with a hydrogen one.

Syzygy Plasmonics has licensed the photocatalyst technology from the Halas lab and will focus on scale up and commercialization.

“In the past few years we have achieved a dramatic scale up and improvement in efficiency. We are even in the design stages for our first micro chemical plant based on the technology,” says Trevor Best, the firm’s CEO.

Best adds: “When applying the antenna-reactor to a chemical process using Syzygy’s reactor we are seeing a dramatic reduction in the operating pressure and temperature of the reactor. We are able to achieve the same conversion, etc., but while operating at hundreds of degrees Celsius lower temperature. This allows us to build our reactors out of aluminum, glass, and plastic, which dramatically reduces our costs. Also, because we are powering the reaction with light that can be generated with renewable electricity, we no longer need to burn fuel to power many of these reactions. This results in a dramatic reduction in carbon emissions.”

Furthermore, scaling up the catalyst manufacturing process has been remarkably simple, notes Best.

Applying the antenna-reactor technology to industry involves a few steps. “First, we created the photocatalytic cell and surrounding reactor enclosure. This reactor uses high efficiency artificial lights to drive the chemical reactions. … the company … is now working on constructing multi-cell reactors. Finally, after the multi-cell is complete then we will combine many of those together into the final chemical systems that make product at scale…We have even automated the process to take out the potential for human error. We have a solid plan to produce catalyst at any scale,” he explains.

The catalyst also shows good stability in terms of its light response. “There are many different types of antenna-reactor photocatalyst. In general, we have seen that they are highly resistant to many forms of catalyst decay including coking, oxidation and sintering. However, they are susceptible to sulfur poisoning so sulfur must be removed from the feedstock gas,” cautions Best.

The company’s future work focuses on two segments: the platform itself and the reaction.

“The next steps for the platform are to continue scaling up and optimizing the photocatalytic reactor that Syzygy is working on. We are currently at a large bench scale unit in our lab and plan an integrated demonstration as part of a hydrogen production system in the next few years.

Best says Syzygy will assess market interest in the C-F breaking catalyst, and how it compares against other options. If there is significant commercial interest, the company will commit resources to scaling up the reaction.

"This general reaction may be useful for remediating many other types of fluorinated molecules," Halas believes.

“… Because the antenna-reactor photocatalyst is a platform, and it has now shown capability with flouromethane, it is very possible it can be adapted to break other types of C-F bonds. This would allow it to be applied in different ways in industry,” Best adds.

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