Exchange is controlled by bulk diffusion into the support

Exchange is controlled by bulk diffusion into the support 

When the rate of diffusion in the support network becomes significant, Eq. (31) can no longer describe the kinetics of exchange. Kakioka et a/.[2 23) have developed a model based on the following assumptions  

In this case, the kinetics of diffusion in the solid follows Eq. (32) 

This type of exchange corresponds to an equilibration of two isotopomers at the catalyst surface according to the reaction 

In most cases, this reaction is much more rapid on the metal than on the support. Those metals which cannot catalyse equilibration are poor X donors for exchange with the support. In what follows, we will consider the case where homoexchange occurs at a significant rate only on the metal. 

---