Anisotropic reaction–diffusion modeling and computational fluid dynamics of packed beds with three‐dimensional Weibull‐distributed catalyst properties

Abstract An anisotropic reaction–diffusion model is developed to describe ethylene epoxidation over Ag/Al 2 O 3 quadrilobe catalyst particles. In the anisotropic model, the spatial variation of physical properties (e.g., pore size and porosity) is represented by a three‐dimensional Weibull distribution. The generation of water within the catalyst suppresses the reaction rate inside the particle, thereby lowering the internal effectiveness factor. To account for particle‐scale heterogeneity and translate the model to the reactor scale, an anisotropic reaction–mass transfer–heat transfer model is established using a particle‐resolved computational fluid dynamics framework. The internal effectiveness factor of the catalyst particle within the packed bed exhibits a progressive increase along the flow direction. Compared with the isotropic model, where the parameters are treated as constants and the contour profiles of reaction rate, mass flux, and heat flux within the catalyst particles are smooth, the anisotropic model exhibits random fluctuations in these contour profiles.