Dual functionality of LaNi5 metal hydride as a catalyst for toluene hydrogenation

Abstract

In this study, we demonstrate that LaNi5 metal hydride serves both as a hydrogen reservoir and an effective catalyst for the hydrogenation of toluene to methylcyclohexane (MCH). Hydrogenation reactions were performed at 348-393 K under 3 MPa hydrogen pressure, achieving a conversion rate of 99.9 % at temperatures exceeding 383 K. Pressure-Composition-Temperature (PCT) measurements revealed that LaNi5 undergoes dehydrogenation under these conditions, releasing stored atomic hydrogen to promote the hydrogenation reaction. Even below the dehydrogenation threshold, LaNi5 exhibited moderate catalytic activity, attributed to surface elemental nickel stabilized by lanthanum oxide species. Compared to pure nickel catalysts, LaNi5 showed superior performance across all tested temperatures, highlighting the synergistic role of its hydrogen storage capability and surface microstructure. These findings establish LaNi5 as a novel dual-functional material, simultaneously serving as a hydrogen storage material and an effective catalyst for liquid organic hydrogen carrier (LOHC).