MODELING AND SIMULATION OF TRANSIENT ADSORPTION AND REACTION IN VACUUM USING THE TEMPORAL ANALYSIS OF PRODUCTS REACTOR

For determining rate constants of catalytic processes (adsorption, des orption, and reaction) from the evaluation of transient experiments in vacuum applying the temporal-analysis-of-products (TAP) reactor, suit able models were developed taking into account the gas-phase transport of the molecules and the surface processes. On the basis of simulatio n results, it is shown that by applying the TAP technique absolute val ues for rate constants of adsorption and desorption can be derived wit hin a ''window'' of their order of magnitudes. It is shown that differ ent types of adsorption (Langmuir, Temkin, Freundlich, and dissociativ e) result in different simulated response signals. Models were develop ed accounting for reactions including the simulation of experiments wi th sequential pulsing of two gases in order to study the reaction of a dsorbed and gaseous species. The specific position of the catalyst-bet ween two inert layers in the TAP reactor has to be considered because it-influences the response in the case of adsorption/desorption proces ses and results in a partial back-diffusion of a reaction product to t he reactor inlet thus enhancing consecutive reactions.