Abstract

The catalytic interconversion between methylcyclohexane (MCH) and toluene is highly promising for utilization as a liquid organic hydrogen carrier (LOHC) system. However, the inevitable isomerization of MCH promoted over the Pt/Al₂O₃ catalyst yields undesirable five-membered ring compounds such as dimethylcyclopentanes (DMCPs) and ethylcyclopentane (ECP). In this study, we developed a method for the preparation of Ir-encapsulated silicalite-1 catalyst for the selective hydrogenolysis of methylcyclopentane (MCP), a model compound of five-membered ring isomers, in the presence of excess MCH. Irⁿ⁺/silicalite-1 was synthesized hydrothermally using tetra-n-propylammonium (ⁿPr₄N⁺) hydroxide as the organic structure-directing agent. The as-prepared sample was treated under H₂ flow at 400 °C to promote the reduction of cationic Ir to highly dispersed Ir⁰ clusters in the micropores, and the Ir⁰ clusters then catalyze the hydrogenolysis of the ⁿPr₄N⁺ molecules inside the micropores, yielding Ir⁰/silicalite-1 catalyst with adequate microporosity. The diffusion coefficient of MCP in the 10-ring channels is two orders of magnitude greater than that of MCH, resulting in the molecular-sieving effect for the mixture of MCP and MCH over the silicalite-1 particles. Therefore, Ir⁰/silicalite-1 catalyst prepared in this study promoted selective hydrogenolysis of MCP even in the presence of excess MCH at 200 °C and showed lower deactivation, making it highly promising for the removal for DMCPs and ECPs from MCH to enable its use as an LOHC in hydrogen transportation.

Graphical Abstract

Selective hydrogenolysis of methylcyclopetane with excess methylcyclohexane over Ir^0/silicalite-1 catalyst

Credit: Inagaki et al., Applied Catalysis A: General, 707, 120517 (2025), https://doi.org/10.1016/j.apcata.2025.120517. © 2025 The Authors. Licensed under CC BY 4.0.