Unlocking Hydrogen Storage Potential: Ni/Al2O3-Catalysed Hydrogenation of Dibenzyltoluene (DBT) for a Liquid Organic Hydrogen Carrier (LOHC) System

Abstract

Liquid organic hydrogen carriers (LOHCs) offer a safe and scalable solution for hydrogen storage and transportation, overcoming many of the limitations of conventional compressed and liquefied hydrogen systems. Among the available LOHCs, the dibenzyltoluene/perhydro-dibenzyltoluene (DBT/18H-DBT) pair is particularly attractive due to its high theoretical hydrogen storage capacity (6.2 wt.%) and favourable handling characteristics. This study investigates the hydrogenation of DBT over a cost-effective 13 wt.% Ni/Al2O3 catalyst using a multiphysics modelling approach developed in COMSOL Multiphysics. A zero-dimensional (0D) kinetic model, assessed against available experimental data, was employed to investigate the effects of temperature and hydrogen pressure on conversion, intermediate formation, and selectivity, and was subsequently extended to a two-dimensional (2D) predictive modelling framework to evaluate reactor behaviour under continuous-flow conditions. The simulations identified an optimum operating window of 505–515 K and 2 MPa, achieving complete DBT conversion and 95–97% selectivity towards the fully hydrogenated product, 18H-DBT, while higher pressures provided only marginal additional benefits. The 2D reactor model further predicted a final 18H-DBT selectivity of 96.8%, confirming the suitability of these conditions for continuous hydrogenation. The developed modelling framework provides valuable insight into reactor-scale performance and offers a robust tool for the design and optimisation of efficient, economically viable LOHC hydrogenation systems based on nickel catalysts.