Autothermal reforming of methane on rhodium catalysts: Microkinetic analysis for model reduction

•Hierarchical model reduction of methane autothermal reforming is carried out.•Reaction path analysis yield insights to major pathway: dissociative activation of methane.•33% reduced microkinetic mechanism and one step rate equation is derived.•Results from reduced mechanism and one-step rate agree with full mechanism.

Methane autothermal reforming has been studied using comprehensive, detailed microkinetic mechanisms, and a hierarchically reduced rate expression has been derived without apriori assumptions. The microkinetic mechanism is adapted from literature and has been validated with reported experimental results. Rate determining steps are elicited by reaction path analysis, partial equilibrium analysis and sensitivity analysis. Results show that methane activation occurs via dissociative adsorption to pyrolysis, while oxidation of the carbon occurs by O(s). Further, the mechanism is reduced through information obtained from the reaction path analysis, which is further substantiated by principal component analysis. A 33% reduction from the full microkinetic mechanism is obtained. One-step rate equation is further derived from the reduced microkinetic mechanism. The results show that this rate equation accurately predicts conversions as well as outlet mole fraction for a wide range of inlet compositions.

Graphical abstractResults from reduced mechanism and one step rate equation show excellent agreement with each other for a wide range of steam to carbon ratios and oxygen to carbon ratios.Figure optionsDownload full-size imageDownload as PowerPoint slide