Intrinsic Kinetics of Dibenzyltoluene Hydrogenation over a Supported Ni Catalyst for Green Hydrogen Storage

As an effective initiative to avoid the fluctuation of renewable energy sources, hydrogen energy storage technology is an important link between hydrogen production and utilization, where liquid organic hydrogen carriers (LOHCs) offer the advantages of high hydrogen storage density and available storage conditions. Dibenzyltoluene (DBT) is a promising LOHC, but the hydrogenation reaction pathways and kinetic parameters guiding reactor design and catalyst performance evaluation are not clear. Here, we systematically investigated the kinetics of DBT hydrogenation over a commercial Ni/Al2O3 catalyst. DBT hydrogenation reaction follows a two-step series reaction from DBT to 12H-DBT and another one-step reaction from 12H-DBT to 18H-DBT. Increasing the hydrogen pressure and temperature can improve the reaction rate, while the stirring speed has no obvious influence. The reaction order for each hydrogenation step (i.e., DBT to 6H-DBT, 6H-DBT to 12H-DBT, and 12H-DBT to 18H-DBT) approximates 1 with respect to reactant concentration (1.06, 0.976, and 1.36, respectively), whereas the reaction order with respect to H2 pressure is approximately equal (0.79, 0.74, 0.745, respectively). The activation energies of each step are 59.254, 56.061, and 64.641 kJ·mol–1, respectively, revealing that 12H-DBT hydrogenation is the rate-determining step. This work is expected to provide a new understanding of the nature of DBT hydrogenation reactions, which is meaningful for the evaluation of catalyst performance and for reactor design.