First-Principles-Based Microkinetic Modeling of Methane Steam Reforming with Improved Description of Product Desorption

The method combining density functional theory (DFT) calculations with microkinetic modeling has attracted increasing attention in obtaining a deeper understanding of catalytic reactions. While product desorption is conventionally regarded as an equilibrated process in the microkinetic modeling, it might be influential to product selectivity when competing reactions should be considered. In this work, a complex reaction network is established first for the methane steam reforming reaction using the equilibrium and immobile models over Ni, Pd, and Pt surfaces. This provides a basis to further investigate the reaction mechanism and kinetic modeling results. The results show that when different desorption models are considered, the total activity regarding methane conversion and the coverage and DRC value of the main species at the steady state are the same on each surface. In contrast, the mechanism of CO2 formation is varied based on different desorption models. Consequently, the rate and selectivity of CO2 generation on each metal catalyst are significantly improved when the barrier of CO desorption is considered in the microkinetic modeling compared with the modeling only with barrierless CO desorption.