Heat transfer and reaction kinetics in porous reacting media for steam methane reforming: a critical review and thermodynamic analysis

Steam methane reforming (SMR) remains the dominant industrial route for hydrogen production; however, accurate modeling continues to be constrained by the intricate coupling of reaction kinetics, multicomponent diffusion, and multi-mode heat transfer within high-temperature porous catalytic media. These challenges intensify when part of the produced hydrogen is combusted to supply the required heat, creating strong radiative and convective interactions that must be resolved to predict reactor performance reliably. This review provides a comprehensive assessment of the mathematical and computational fluid dynamics (CFD) models used to simulate SMR across pore-scale, mesoscale, and reactor-scale configurations. Homogeneous and pore-scale modeling approaches are examined, including local thermal equilibrium (LTE), local thermal non-equilibrium (LNTE), discrete element CFD coupling, and solid-particle methods. Various radiative heat transfer models, mass-diffusion formulations, and momentum closures are reviewed and evaluated for their suitability in SMR applications. A detailed comparison of chemical kinetic models is presented, highlighting the Langmuir–Hinshelwood–based Xu–Froment mechanism as the most widely adopted framework for SMR simulations. A thermodynamic analysis based on Gibbs free-energy minimization is also performed to quantify equilibrium species distributions across a range of temperatures, pressures, and steam-to-carbon ratios. This review offers a unified perspective by integrating thermodynamic analysis, reaction kinetics, diffusion models, radiation treatment, and multi-scale CFD approaches within one cohesive framework, while also identifying major gaps in current SMR modeling practices such as inconsistent diffusion and effectiveness factor treatments, limited application of radiation models, and the scarcity of industrial-scale validation studies, thereby outlining clear research directions for improving future SMR simulations.