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Metal catalysts can be valuable, even when they aren't precious

Transforming trash to treasure might sound like alchemy, but in some industries it's already happening. For example, furfural, an abundant plant byproduct, is regularly converted to tetrahydrofuran (THF)-based compounds that are highly valued as pharmaceutical intermediates and solvents.

This conversion process isn't easy though. An efficient conversion requires either expensive precious metal catalysts, like ruthenium and palladium, or non-precious metal catalysts that demand harsh conditions.

Now, a research team from the University of Osaka has set out to address this issue. As detailed in their study in ACS Sustainable Chemistry & Engineering, the team sought to develop a cost-effective catalyst for furfural conversion under mild conditions.

The team previously found that nickel carbide nanoparticles, which are particles with a diameter of less than one hundred nanometers, can act as an effective catalyst in chemical conversions. In the present study, nickel carbide nanoparticles were supported on alumina to provide an effective catalyst for accessing THF compounds from furfural through hydrogenation, which involves the reaction of furfural with hydrogen molecules.

"Our catalyst readily converts furfural to the important synthetic intermediate tetrahydrofurfuryl alcohol through hydrogenation even at ambient hydrogen pressure," says lead author Taiki Kawakami. "Such high yield under mild conditions has not previously been realized using non-precious metal catalysts."

Promisingly, the nickel-based catalyst achieved 90% conversion of furfural despite the low hydrogen pressure. The catalyst was very effective under mild conditions because of its strong ability to react with hydrogen molecules.

"The catalyst nanoparticles readily react with hydrogen to form polar hydrogen species that reduce furfural," explains senior author Tomoo Mizugaki. "In addition, the nanoparticles interact with the alumina support in a manner that further promotes furfural reduction."

The combined effects of the catalyst components led to the high-yielding synthesis of useful THF-based materials from the abundant starting material furfural under easily achievable conditions. Overall, the developed catalyst represents a major step toward the economically feasible, energy-efficient synthesis of valuable chemicals from waste biomass in biorefineries worldwide.