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N2 speeds up hydrogenation on Ru surface

‘Inert’ gas catalyzes transformation of p-cresol into toluene

by Leigh Krietsch Boerner
November 3, 2019 | A version of this story appeared in Volume 97, Issue 43


Illustration of how N<sub>2</sub> catalyzes the hydrodeoxygenation reaction of p-cresol to toluene over Ru/TiO<sub>2</sub>. N<sub>2</sub> attaches to the Ru surface, and H<sub>2</sub> hydrogenates it. This then helps transform p-cresol into toluene.
Credit: Nat. Catal./C&EN
N2 catalyzes the hydrodeoxygenation of p-cresol to toluene over Ru/TiO2.

Gaseous nitrogen is a bit of a chemical wallflower. While high temperatures and pressures such as those used in the Haber-Bosch process can convince the compound to react, gaseous N2 rarely acts as an active catalytic species. Now a group of international researchers has found that adding N2 gas to a ruthenium-based catalyst speeds up the hydrodeoxygenation of p-cresol into toluene by over 400%; it’s a reaction that could have applications in converting bio-oils into useful chemicals (Nat. Catal. 2019, DOI: 10.1038/s41929-019-0368-6). Led by Jun Li from Tsinghua University and Edman Tsang and Dermot O’Hare from the University of Oxford, the researchers stumbled across this chemistry when trying to pressurize their reactor with an inert gas, O’Hare says. They added gaseous N2 to a solid-state titanium oxide–supported Ru catalyst, with hydrogen gas and p-cresol, and found that the Ru surface activates the N2 to form either N2H or N2H2. These acidic hydrogens help boot the –OH groups off the p-cresol, shifting the rate-determining step from –OH hydrogenation to N2 hydrogenation. The group found that the reaction worked well over multiple supports, including Al2O3, ZrO2, and active carbon. This work shows chemists that N2 “cannot be simply viewed as an inert bystander,” Li says.


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