Remarkably fast low-temperature hydrogen storage into aromatic benzyltoluenes over MgO-supported Ru nanoparticles with homolytic and heterolytic H2 adsorption

Hydrogen storage into aromatic compounds under mild conditions is a stringent issue in liquid organic hydrogen carrier (LOHC) systems. Herein, we report a highly active Ru/MgO catalyst in the hydrogenation of monobenzyltoluene and dibenzyltoluene at low temperatures. When MgO with basic surface oxygen was employed as a support, Ru/MgO showed a faster H-2 storage rate and superior kinetic parameters than the other supported Ru catalysts. The better catalytic performance of Ru/MgO was explained by the results of characterization and control experiments. Ru/MgO could adsorb the large amounts of monobenzyltoluene and hydrogen with higher strength. Particularly, homolytic and heterolytic hydrogen adsorption modes were identified in Ru/MgO, unlike Ru/Al2O3 showing homolytic H-2 adsorption. Density functional theory calculations confirmed heterolytic H-2 dissociation near the Ru-MgO interface, which assured the hydrogenation efficiency of Ru/MgO. Consequently, Ru/MgO is highly recommended for fast hydrogen storage into aromatic LOHC compounds at low temperatures.

Automated summary

This study introduced a highly active Ru/MgO catalyst for hydrogenation of monobenzyltoluene and dibenzyltoluene at low temperatures, exhibiting faster storage rate and superior kinetic parameters compared to other supported Ru catalysts. The better catalytic performance is attributed to the strong adsorption capability of monobenzyltoluene and hydrogen by Ru/MgO, as well as the heterolytic H-2 dissociation near the Ru-MgO interface confirmed by DFT calculations.