Dynamics of diffusion and adsorption in a single catalyst pellet

Exposing one face of a catalyst pellet to a pulse of tracer gas and analyzing the response at the opposite and provides a dynamic method for measuring the effective diffusivity of porous catalysts. The first and second moments of the response peak are shown to be a function of only De and the geometry of the pellet and detector chamber for a nonadsorbing, tracer‐carrier system. Data obtained for alumina pellets of different densities ilustrate the method. For an adsorbing tracer, the first moment is a function of both De and the adsorption equilibrium comstant. Measurements for an unconsolidated assembly of nickel/Kieselguhr particles, using the D2‐H2 system, show that first‐moment data are sufficient to calculate reasonably accurate values of the equilibrium adsorption. However, it appears to be difficult to obtain adsorption rate constants by this method.