Temporal analysis of products

In a typical TAP pulse-response experiment, very small (~10⁻⁹ mol) and narrow (~100 μs) gas pulses are introduced into the evacuated (~10⁻⁶ torr) microreactor containing a catalytic sample. While the injected gas molecules traverse the microreactor packing through the interstitial voids, they encounter the catalyst on which they may undergo chemical transformations. Unconverted and newly formed gas molecules eventually reach the reactor's outlet and escape into an adjacent vacuum chamber, where they are detected with millisecond time resolution by the QMS. The exit-flow rates of reactants, products and inert molecules recorded by the QMS are then used to quantify catalytic properties and deduce reaction mechanisms. The same TAP instrument can typically accommodate other types of kinetic measurements, including atmospheric pressure flow experiments (10⁵ Pa), Temperature-Programmed Desorption (TPD), and Steady-State Isotopic Transient Kinetic Analysis (SSITKA).

The general methodology of TAP data analysis, developed in a series of papers by Grigoriy (Gregory) Yablonsky ^{[3] [4]} ,^[5] is based on comparing an inert gas response which is controlled only by Knudsen diffusion with a reactive gas response which is controlled by diffusion as well as adsorption and chemical reactions on the catalyst sample. TAP pulse-response experiments can be effectively modeled by a one-dimensional (1D) diffusion equation with uniquely simple combination of boundary conditions.