Diffusion and reaction on nonpermeable catalysts

In the steady state, the rate of diffusion to the surface equals the rate of reaction on the catalytic surface, 

A relation of special interest is the ratio of the rate of reaction under external diffusional conditions to the rate in the absence of diffusional resistance. This is called the external effectiveness, r)e. and may be written 

Then the rate of reaction in terms of the bulk fluid concentration may be written 

Solutions for T)e with several power law equations are developed in P7.03.14 and for an L-H rate equation in P7.03.15. 

For diffusion with reaction in uniform pores in a sphere, the steady material balance is 

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