A sensitivity study of the oxidation of compressed natural gas on platinum

This paper presents a sensitivity study for the oxidation of methane (CH4) over platinum (Pt). Some dominant reactions in the CH4-Pt surface chemistry were identified and the rates of these reactions were subsequently modified to enhance the calculations. Initially, a range of CH4-Pt surface mechanisms available in the literature are used, along with the relevant detailed gaseous chemistry to compute the structure of premixed compressed natural gas (CNG)/air flames co-flowing around a flat, vertical, unconfined, rectangular, and platinum plate. Comparison with existing measurements of surface temperature and species concentrations revealed significant discrepancies for all mechanisms. Sensitivity analysis has identified nine key reactions which dominate the heterogeneous chemistry of methane over platinum. The rates of these reactions were modified over a reasonable range and in different combinations leading to an “optimal” mechanism for methane/air surface chemistry on platinum. The new mechanism is then used with the same flow geometry for different cases varying the temperature of the incoming mixture (Tjet), its equivalence ratio (Ф) and the Reynolds number (Re). Results from the modified surface mechanism demonstrate reasonably good agreement with the experimental data for a wide range of operating conditions.