Analysis of consecutive adsorption mechanisms

Let us examine one more simple three-step mechanism whose steady-state characteristics are also of the hysteresis type. In what follows we will show that their type differs considerably from the previous one. It is the mechanism including steps of consecutive adsorption one gas-phase substance is adsorbed on unoccupied sites and is then joined by a second gaseous substance, whereupon the two intermediates interact. In the general form this 

This mechanism is a constituent of the mechanisms for various catalytic reactions, e.g. for NH3 oxidation [233]. 

A kinetic model of mechanism (30) for the subsystem of the intermediates AZ, ABZ, and Z, assuming constant concentrations of the observed sub- 

The simplest mechanism type (30) admitting a multiplicity of steady states is represented as [223, 232] 

In the simplest case, when k x = k 2 = 0, the fulfilment of (33) is necessary and sufficient for the fact that, along with a boundary steady state, the system has two internal steady states with a non-zero reaction rate W = k3x2y. Finally, we obtain the simple expression 

---