Kinetics of Methane Nonoxidative Aromatization over Ru−Mo/HZSM-5 Catalyst

Kinetic study of oxygen-free methane dehydrogenation and aromatization over Ru−Mo/HZSM-5 was carried out in a fixed-bed differential reactor under atmospheric pressure. The reaction temperature was varied between 873 and 973 K, and the methane feed fraction ranged from 50 to 90% v/v. A plausible reaction pathway involved in oxygen-free methane dehydrogenation and aromatization over Ru−Mo/HZSM-5 was proposed. Different models based on Langmuir−Hinshelwood−Hougen−Watson reaction mechanisms were tested to correlate the kinetic data. Among these models, the one postulating that the surface dehydrogenation reaction of adsorbed methane is rate-determining was successful in terms of physical likeliness (thermodynamic and kinetic parameters) and statistical goodness of fit. The activation energy, adsorption enthalpy, and entropy frequency were evaluated by means of Arrhenius or Van't Hoff relationships.