Hydrogenation of the LOHC Compound Monobenzyl Toluene over ZrO2-supported Ru Nanoparticles: A Consequence of Zirconium Hydroxide's Surface Hydroxyl Group and Surface Area

Monobenzyl toluene (H-0-MBT) is an interesting material as a liquid organic hydrogen carrier, which is commercially available as heat transfer oil. In H-2 storage of H-0-MBT via the hydrogenation reaction, supported Ru catalysts were reported to show superior performance. Herein, ZrO2-supported Ru nanoparticles were synthesized by using triruthenium dodecarbonyl Ru-3(CO)(12) as Ru precursor and precipitated zirconium hydroxide subjected to different ageing periods. Although the extended ageing resulted in a larger BET surface area of Ru/ZrO2, the hydrogenation activity and Ru dispersion turned out to be in a volcano-shaped dependence on the ageing period. The characterization work on zirconium hydroxide revealed that the relative number of surface to bridging oxygen species decreased upon prolonged ageing and the hydroxylation degree largely affected the interaction with CO ligand of adsorbed Ru species. Consequently, the hydrogenation activity trend of the present Ru/ZrO2 was a combined consequence of the surface OH content and surface area of zirconium hydroxide.