Intraparticle‐forced convection effect in catalyst diffusivity measurements and reactor design

Intraparticle forced convection was considered in order to explain experimentally observed changes in effective diffusivity (apparent) with flowrate, when measures are carried out in fixed beds. A complete model taking into account intraparticle diffusion and forced convection together with film diffusion is derived in order to analyze diffusivity measurements by physical methods, both in perfectly mixed reactors and fixed beds. The experiments were carried out with hydrogen tracer in a partial oxydation catalyst. Implications of the use of such “apparent” effective diffusivities in reactor design are discussed, showing that errors of 100% can be made.