Kinetic phase transitions in dimer–dimer irreversible catalytic surface reactions of the type: A2+xB2→2ABx

The kinetics of irreversible dimer–dimer surface reactions of the type A2+xB2→2ABx (x takes values 1, 2 and 3), with desorption of dimer B2, has been investigated by means of Monte Carlo simulation. For a desorption probability (P) of B2 equal to zero, a single discontinuous transition separating one saturated state from another is obtained at a point where feed concentration is exactly related to the stoichiometry of the particular reaction. With the increase in P, a steady reactive state which is separated from the poisoned states by two transitions is obtained for each reaction scheme. The position of the transition points depends upon the value of P. For P equal to one, a single continuous transition point separates a poisoned state from a steady reactive state for each reaction scheme. The window width, which defines the steady reactive state, shows an exponential behaviour with P.