Abstract
In the catalytic oxidation of ethane on platinum-containing monoliths, the high rates of the surface reactions coupled with their high exothermicities lead to a very large axial temperature gradient over a distance comprising only a minor fraction of the reactor length. The temperature reaches a level such that homogeneous gas-phase reactions occur rapidly enough to make a large contribution to the overall conversion occurring in the remainder of the reactor. The gas temperatures generated by the surface reactions are high enough so that ignition delay times for the gas-phase reactions are small compared to total residence times in the reactor. For a quantitative assessment of the extent to which homogeneous gas-phase reactions contribute to the overall conversion, the most important considerations are having a reliable estimate of the temperature gradient generated by the surface catalyzed reactions at the front of the reactor and being careful to utilize a kinetic scheme for the gas-phase reactions that is appropriate for the reaction conditions.