A NONTHERMAL MODEL FOR CATALYTIC SURFACE REACTION OF THE TYPE A2+B2→2AB: A MONTE CARLO SIMULATION STUDY

Abstract

The kinetics of irreversible dimer–dimer reaction of the type A2+B2→2AB has already been studied through Monte Carlo simulation via a model based on Langmuir–Hinshelwood (thermal) mechanism. The results of this study are well known. There is single transition point (yC) at yB=0.5 (where yBis partial pressure of B2dimer in gas phase), which separates the two poisoned states from each other. Here, we have studied this reaction on the basis of a nonthermal model, which involves the precursor motion of B2molecule. The most interesting feature of this model is that it yields a steady reactive window. The phase diagram is similar to the ZGB model. The reactive window is separated by continuous and discontinuous irreversible phase transitions. The width of the reactive window depends upon the mobility of the precursors. The dependence of production rate on partial pressure of B2is shown by simple mathematical equations in our model. Some interesting results are observed when reaction between precursors and chemisorbed B atoms is considered.