Kinetic analysis of dibenzyltoluene hydrogenation on commercial Ru/Al2O3 catalyst for liquid organic hydrogen carrier

Abstract

The hydrogenation kinetics of dibenzyltoluene was studied to utilize LOHC (Liquid Organic Hydrogen Carriers) as a hydrogen storage medium. The hydrogenation of dibenzyltoluene was experimentally performed at various temperature and pressure conditions with commercial Ru/Al2O3 catalyst at a batch reactor. It showed that the reaction rate increased with increasing temperature and pressure. Analysis of the concentrations of dibenzyltoluene (H0-DBT) and hydrogenated forms (H6-DBT, H12-DBT, H18-DBT) using GC–MS showed that the concentrations were only a function of DoH (Degree of Hydrogenation) regardless of temperature and pressure. Based on the experimental observations, the Langmuir-Hinshelwood model is applied with the assumptions that the hydrogenation reaction occurs sequentially up to fully hydrogenated form and the surface irreversible reaction is a rate determining step following assumptions. 1. Hydrogenation occurs sequentially. 2. Surface reaction was irreversible rate determining step. 3. Hydrogen adsorption behavior is non-competitive. The small adsorption constant of H12-DBT explained that H12-DBT was accumulated by H0-DBT and H6-DBT. Consequently, the hydrogenation of dibenzyltoluene is important for the adsorption behavior of the reactants on the catalyst surface. Dibenzyltoluene hydrogenation was calculated by using regression equations as a function of DoH and a kinetic model. Calculation result has an error within 20% in most of degree of hydrogenation. In particular, the simulation has a less than 10% error high accuracy at above of 70% degree of hydrogenation or more than 60 bar. Consequently, the final model approximates the actual behavior of dibenzyltoluene hydrogenation over a wide range of temperature (130–170 °C) and pressure (40–80 bar). © 2023