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 ethane to ethylene in a short-contact-time reactor, using a two-dimensional computational 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 experimental data. Simulations using these mechanisms suggest that platinum-catalyzed heterogeneous chemical processes are responsible for the oxidation of surface carbon and hydrogen, resulting in localized heat release into the gas phase. This heat release drives endothermic homogeneous and heterogeneous cracking of ethane to ethylene and H2. The proportion of homogeneous and heterogeneous contributions depends strongly upon the reactor operating conditions. In addition to predictions of ethane conversion and ethylene selectivity, the model also predicts the production of all other major products: H2O, H2, CH4, CO, and CO2. A good fit is obtained between model predictions and experimental data for ethane/oxygen mixtures. The model is applied to ethane/hydrogen/oxygen mixtures and good agreement with this set of experimental data is also obtained.