General Selection Methodology for Multiphase Reactors

The oil shale reactor selection can now be generalized to the general case of multiphase reactors (gas-liquid, gas-solid, gas-liquid-solid, 

Reactor Subset I—(Volume/Surface Area) Selection 

For multiphase reactors, the first important decision to be made concerns the choice of the (volume/surface area) ratio for each of the phases 

The solid phase could be a reactant, product, or catalyst. In general the decision on the choice of the particle size rests on an analysis of the extra-and intra-particle transport processes and chemical reaction. For solid-catalyzed reactions, an important consideration in the choice of the particle size is the desire to utilize the catalyst particle most effectively. This would require choosing a particle size such that the generalized Thiele modulus gen, representing the ratio of characteristic intraparticle diffusion and reaction times, has a value smaller than 0.4 see Fig. 13. Such an effectiveness factor-Thiele modulus analysis may suggest particle sizes too small for use in packed bed operation. The choice is then either to consider fluidized bed operation, or to used shaped catalysts (e.g., spoked wheels, grooved cylinders, star-shaped extrudates, four-leafed clover, etc.). Another commonly used procedure for overcoming the problem of diffu-sional limitations is to have nonuniform distribution of active components (e.g., precious metals) within the catalyst particle. 

Often an important reason to avoid intraparticle diffusion resistances is from selectivity considerations. To maximize the intermediate product in a consecutive reaction scheme, we should avoid intraparticle diffusional resistances. For butene dehydrogenation it can be seen in Fig. 14 that 

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