(569bi) Detailed Kinetics Study of Methylcyclohexane Dehydrogenation on Pt/Al2O3 Catalyst

Liquid organic hydrides are efficient media for hydrogen storage, facilitating easy and safe transportation. The dehydrogenation-hydrogenation cycles between methylcyclohexane (MCH) and toluene has emerged as a viable means for hydrogen transport over long distances, especially by ships. Amongst the various industry-relevant catalysts for the MCH-toluene cycles, Pt/Al₂O₃ catalysts are widely regarded as the most commercially viable. Here, the kinetics of the dehydrogenation of methylcyclohexane on a Pt (1 wt%)/Al₂O₃ catalyst, prepared by impregnation, were studied in a fixed-bed reactor. Kinetics measurements were carried out in strictly surface chemistry-controlled regimes, with dominating partial pressures of MCH, toluene, or hydrogen, which ranged from 0.8 to 2.4 bar. The apparent reaction order is positive with respect to MCH, and negative with respect to hydrogen and toluene. In addition, the apparent activation energy is greatly increased when the partial pressure of hydrogen and toluene, suggesting that product desorption are slow compared to MCH adsorption. Rate equations derived from Langmuir-Hinshelwood-Hougen-Watson (LHHW) models were discriminated by the experimental data and also validated against first-principle calculations. We found the desorption of the second hydrogen molecule is the most likely rate-controlling step.