Consider a CSTR (continuous stirred-tank reactor) with a slurried catalyst where a first-order reaction

is taking place. The catalyst is subject to deactivation which follows a first-order law. Thus the catalyst activity,

, obeys the governing equation

with

.
This Demonstration plots the dimensionless concentration,

, versus time for user-set values of the reactor's residence time, catalyst deactivation, and first-order reaction rate constants. Here the feed concentration of species

to the reactor and its initial concentration in the reactor are both taken equal to

. You can observe the behavior of catalyst activity versus time, which depends solely on the catalyst deactivation rate constant. It is found that the dimensionless concentration,

, goes through a minimum when there is deactivation; it reaches a steady state value when

(the case of no deactivation) as displayed in the second snapshot.