Modeling a transport phenomena limited reactivity in short contact time catalytic partial oxidation reactors

The present paper describes a computational study of the short contact time catalytic partial oxidation of methane in fixed-bed reactors employing a rhodium-based catalyst. A monodimensional model was developed, and its validation was carried out on the basis of two experimental sets of literature data. Transport phenomena limited conditions and a local equilibrium reactivity along the catalytic bed were assumed. The last assumption provided an acceptable simplification to describe the complex microkinetic reactions taking place on the catalyst surface. The model results were satisfactorily in agreement with the measured values of conversion, product selectivity, and solid-phase temperature profiles along the fixed bed, at different space velocities and catalyst particle sizes. The numerical analysis, which allowed one to highlight the principles governing the system, also pointed out the existence of a local solid-gas temperature difference occurring within the catalytic bed. This difference dropped to zero when the reactions were completed. Finally, particular attention was devoted to the relationship between the reactor performance and transport phenomena, emphasizing the role of thermal conductivity and radiation within the fixed bed.