Kinetic instabilities in heterogeneously catalyzed reactions—I: Rate multiplicity with langmuir-type kinetics

The question under which conditions kinetic instabilities can be described by Langmuir type kinetics is studied using a fairly general model for the surface reactionpA + qB → C. This paper is concerned with the occurrence of rate multiplicities (ignition-extinction phenomena). It is shown that rate multiplicity can be caused by the competing chemisorption of A and B upon the same active sites of the catalyst. Rate multiplicity can occur if at least one of the chemisorption or reaction steps is of second order. No rate multiplicity can be expected, if either A or B reacts via an Eley-Rideal type mechanism.