A catalytic reaction mechanism for methane partial oxidation at short contact times, reforming, and combustion, and for oxygenate decomposition and oxidation on platinum

Hydrogen production from fuel processing and its utilization in fuel cell technology is recognized as a promising route to future power generation. Reliable chemistry models are necessary to improve the hydrogen generation processes via optimal reactor design. With this objective, here, we present a predictive microkinetic model for CH4 (C-1) partial oxidation, combustion, and reforming, as well as oxygenate (CH3OH and CH2O) decomposition and oxidation on platinum, consisting of 104 elementary-like steps. A hierarchical multiscale approach is used in the parameter estimation of bottom-up mechanism building. Thermodynamic consistency is ensured in the C-1 mechanism. Important kinetic parameters are identified via sensitivity analysis for various experimental systems, using diverse operating conditions, and only a limited number of important kinetic parameters are refined (four for CH4). The C-1 mechanism is extensively validated against several additional experimental data and is observed to be fairly predictive (within the uncertainty of measurements in catalyst surface area, temperature, etc.). Analysis shows spatial zones in catalytic methane oxidation at short contact times, viz., an oxidation zone near the reactor entrance, followed by a reforming zone, where mainly steam reforming and, to a lesser extent, dry reforming occur. Thus, methane oxidation follows the indirect pathway (i.e., total oxidation products are first formed), followed by reforming to generate the partial oxidation ones, in agreement with modeled experimental data.