In a catalytic reactor, at least two substances are brought into contact with each other. One is a substance that we would like to change in some chemical way; and the other substance is the catalyst that is supposed to bring this change about. The two substances are mixed and heated to provide the energy for the change. It is also necessary to provide the plumbing for the substances to enter the reactor and for the end product to leave the reactor. Some parts that are not converted have to be re-cycled back for a second round (and possibly third and more rounds) through the reactor until all of the original substance has finally been transformed. One example for this process is the breaking down of the long molecular chains of crude oil in the effort to make gasoline.
As already indicated, the catalyst performs its work upon the substance and brings about a change. However, by doing so, it ages over time and thereby exhausts its potential to cause the change. This degradation of the catalyst is the primary problem in operating such a reactor continuously over the long term. The catalyst must therefore be re-activated in some fashion and at some time.
For complete details on this case study, go to: Catalytic Reactors in Chemistry and Petrochemistry