Micro-kinetic modeling study of dry reforming of methane over the Ni-based catalyst

Dry reforming of methane (DRM) creates an opportunity to produce syngas using the shale gas and CO2. In the present work, a comprehensive and thermodynamically consistent micro-kinetic modeling was carried out for the DRM reaction under different reaction conditions. In order to reveal the complicated kinetics evolution, a rigorous descriptor (H2O/H-2) and a rough descriptor (CO2/CH4) were identified due to their correlations with the theta(o)/theta(*) ratio, dominant reaction pathway (DRP) and kinetically relevant steps (KRS). Moreover, the evolution of DRP and KRS along the descriptors under different reaction conditions were elucidated using the combined analyses of reaction pathway, sensitivity and partial equilibrium. It shows that at the high temperature, DRM is predominated by the first C-H bond rupture via the direct and/or O*-assisted mode; CO2 adsorption becomes kinetically relevant at the low descriptor. At the high total pressure, (CH2* + *) and (CH4* + O* would become the KRS at the low and high descriptors, respectively. In the end, hierarchical chemistry reduction gave two reduced mechanisms and an overall kinetics equation, with which main kinetics features could be predicted. Concept of descriptors seems to be generalized into other oxidation chemistries (e.g., steam reforming, RWGS and oxidative dehydrogenation) and provides insights into the reactor design and reaction optimization.