How catalytic mechanisms reveal themselves in multiple steady-state data: I. Basic principles

Multiple steady states are often observed in isothermal continuous flow sti rred tank reactors (CFSTRs) involving heterogeneous catalysis. At least, wh en certain physical conditions prevail, even fragmentary multiple steady-st ate data can be used to help determine the operative catalytic mechanism. T his article describes theory that can ascertain both whether a given candid ate mechanism has the capacity to support multiple steady states and, more importantly, whether the mechanism has the capacity to support a particular pair of steady states observed experimentally. In this article, hypothetic al examples are used to illustrate the scope, purpose and methodology of th is theory. The examples also demonstrate the way in which even partial mult iple steady-state data provide a basis for highly refined discrimination be tween very similar mechanisms. In a companion article, actual multiple stea dy-state data are used to discriminate between proposed mechanisms for ethy lene hydrogenation on rhodium. A public computer program is available that will allow the user to apply the theory described in this article without k nowledge of any underlying theory. (C) 2000 Elsevier Science B.V. All right s reserved.