Theor. anal. of the reactor performance under unsteady-state conditions was carried out. The reactions are described by two kinetic models, which involve the participation in catalytic reaction of two types of active sites. The kinetic model I assumes the blocking of one of the active sites by a reactant, and the kinetic model II suggests a transformation of active sites of one type into another under the effect of the reaction temp. The unsteady-state conditions on the catalyst surface are supposed to be created (i) by forced oscillations of temp. and concn. in the reactor inlet (periodic operation of reactor) and (ii) by catalyst circulation between two reactors in a dual-reactor system (spatial regulation). The effect of various parameters like concn. of reactant, cycle split, length of period of forced oscillations, temps. and the ratio of catalyst vols. in the dual-reactor was investigated with respect to the yield of the desired product. It is shown that for both cases of unsteady-state conditions (periodic reactor operation as well as in a dual-reactor system), a mean reaction rate predicted by the kinetic model I was up to two times higher than the steady-state value. The kinetic model II shows a 20% increase of the selectivity towards the desired product. [on SciFinder (R)]