The use of transient methods to discriminate heterogeneous catalytic models was demonstrated for the catalytic epoxidn. of C2H4 on Ag and for the catalytic acetoxylation of C2H4 to vinyl acetate on a Pd catalyst. In sep. expts. the sorption kinetics on the carrier and the Pd catalyst were detd. and used to describe the dynamic behavior of the reactor. The proposed kinetic models described quant. both steady-state and the dynamic behavior of the reaction. [on SciFinder (R)]