TAP-2: An interrogative kinetics approach

The TAP-2 reactor system and the theoretical basis of TAP pulse response experiments are discussed. On the basis of the TAP system, an alternative to the traditional kinetic approach in heterogeneous catalysis is developed. This new approach, termed 'interrogative kinetics' involves a combination of two types of kinetic experiments called 'state-defining' (friendly) and 'state-altering' (typical) experiments. The state defining kinetic parameter, or 'kinetic parameter of the catalyst' (KPC) is proposed and compared with the kinetic characteristic 'turnover number'. The theory of TAP pulse response experiments is developed. Two deterministic models based on partial-differential equations are analyzed for the cases of diffusion, irreversible adsorption/reaction and reversible adsorption. The 'standard diffusion curve' that can be used for distinguishing the Knudsen flow regime is described, and simple criteria of the Knudsen regime are proposed. The concept of relative flow is described, and different fingerprints of TAP kinetics for irreversible adsorption/reaction and reversible adsorption are presented. TAP-2 experimental results on the selective oxidation of n-butane are used to illustrate the methodology of interrogative kinetics.