Intra-particle diffusion limitation for steam methane reforming over a Ni-based catalyst

Abstract

This work aims to evaluate the diffusion limitation for the steam methane reforming process over spherical catalyst particles (Ni/α-Al2O). Numerical calculations based on a CFD model were conducted to determine the intrinsic and actual reaction rates. The CFD model was validated using experimental results, and good agreement was achieved. The effectiveness factor for the reaction rates was used to express the effect of diffusion limitation within the porous catalyst particle. The effectiveness factor was determined for a wide range of operational parameters, including a temperature range of 800–1300 K and a steam-to-methane ratio of 1–5. The analysis was performed for spherical catalyst particles with diameters up to 3.42 mm, and the effectiveness factor as a function of catalyst particle diameter, temperature, and steam-to-methane ratio was established. The results show that the effectiveness factor is inversely proportional to the diameter of the catalyst particle and that an increase in reaction temperature and steam-to-methane ratio leads to an increase in diffusion limitation. The limitations of the analysis are discussed and justified. The final expression for the effectiveness factor can be used in a pseudo-homogeneous steam methane reformer model where the effectiveness factor varies depending on the position in the packed bed.