Understanding homogeneous and heterogeneous contributions to the platinum-catalyzed partial oxidation of ethane in a short-contact-time reactor

This paper describes a computational study of the partial oxidation of etha ne to ethylene in a short-contact-time reactor, using a two-dimensional com putational fluid dynamics model with full heat and mass transport. Detailed heterogeneous and homogeneous chemical kinetic mechanisms are employed to describe the chemistry. Rate constants for elementary surface reactions are determined from literature sources or by fitting model predictions to expe rimental data. Simulations using these mechanisms suggest that platinum-cat alyzed heterogeneous chemical processes are responsible for the oxidation o f surface carbon and hydrogen, resulting in localized heat release into the gas phase. This heat release drives endothermic homogeneous and heterogene ous cracking of ethane to ethylene and H-2. The proportion of homogeneous a nd heterogeneous contributions depends strongly upon the reactor operating conditions. In addition to predictions of ethane conversion and ethylene se lectivity, the model also predicts the production of all other major produc ts: H2O, H-2, CH4, CO, and CO2. A good fit is obtained between model predic tions and experimental data for ethane/oxygen mixtures. The model is applie d to ethane/ hydrogen/oxygen mixtures and good agreement with this set of e xperimental. data is also obtained. (C) 2000 Academic Press.