Top-down kinetic modeling from power law to elementary steps using KASTER: A methane steam reforming case study

A top-down methodology for kinetic model construction including regression against experimental data is proposed using “KASTER.” As a case study, it is applied in the assessment of methane steam reforming (MSR) including water–gas shift (WGS) on a Ni catalyst at 923 K. The degree of detail in the reaction mechanism and the corresponding model is gradually enhanced, typically ranging from a simple power law to a microkinetic model. The reactor equations are solved transiently, preventing the numerical challenges encountered in the steady-state solution, particularly for microkinetic models. The microkinetic variant indicated that CH₄ dissociative adsorption and CO formation are kinetically relevant steps in MSR, while COOH formation is rate-determining in WGS. However, the model providing the best balance between detail accounted for and parameter significance corresponded to a Langmuir–Hinshelwood–Hougen–Watson (LHHW) mechanism accounting for dissociative adsorption, with CO formation and COOH formation as rate-determining steps for MSR and WGS, respectively.