Fractal aspects in the catalytic reforming of naphtha

An industrial catalytic reforming unit was simulated, accounting for the fractal morphology of the internal surface of the porous PtRe/Al2O3 catalyst. The reaction network consists of 86 reactions, with Hougen-Watson kinetics, between 29 lumps. Diffusion and reaction inside the catalyst particles was rigorously simulated, solving the complete set of continuity equations and Stefan-Maxwell equations for multicomponent diffusion by orthogonal collocation. The influence of the fractal morphology on the Knudsen diffusivities was calculated using a fractal perturbation technique. Reactor profiles, as well as intraparticle profiles, are simulated within a reasonable CPU time, so that approximations using the generalized Thiele modulus are unnecessary. Comparison between the results for smooth and fractally rough catalyst surfaces shows convincingly that the fractal surface morphology has a significant impact on the yields and product distribution.