Reaction with Diffusion in Complicated Pore Structures

9 Reaction with Diffusion in Complicated Pore Structures  

Most of the previous discussion was based on taking the Iid catalyst pellet to have a simple pore structure—one average pore radius. For the case of a micromacro pore size distnbution, Mingle and Smith [137] and Carberry [92] have derived expressions for the overall effectiveness fiictor for both micro and macro diffusioo. As a simple example, consider a first-order reaction, with intrinsic rate constantil[,per surfacearea of catalyst Then the massbalancefor the micropores is  

It is undmtood, of course, that the size of the micropores, L , is the volume/ external surfece of the micro particle. 

the effect of the microparticles b to possibly have an effectiveness factor, less than unity, based on microparticle properties, Eq. 3.9,a-3. The overall effectiveness factor then consists of the product of n, and a macroeffcctivcness factor, and the latter b based on macropeUet properties plus the micro effectiveness factor—Eq. 3.941-5. Often the microparticles are sui iently small so that a 1.0 recall from above that there is usually not any micropore diffusional limitations unless these exist for the macropores. 

This was extended to complex consecutive reactions by Gtrberry [138]. The result, neglecting external transport, was similar to Eq. 3.8-5, but with the same type of changes noted above  

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