In heterogeneous catalytic reactions, the rate of adsorption often falls extremely rapidly with increasing coverage. The reason can be a strong inhibition by a reactant or an increasing activation energy with coverage. Adsorption/desorption models based on those assumptions predict a considerable rate improvement for cyclic operation. This was demonstrated by exptl. study of the heterogeneous catalytic addn. of HOAc to C2H4. [on SciFinder (R)]