The steady-state diffusion and flow of ternary mixtures of non-adsorbe
d gases through porous substrates cut from commercial pellets of nicke
l-based catalysts have been studied in a Wicke-Kallenbach cell. The ra
tes of transport were obtained from the rates of flow of pure gases an
d composition measurements were obtained by gas chromatography. In sev
eral experiments a predetermined pressure difference across the cell w
as applied so that the measured rates of transport reflected the effec
t of transition-range diffusion and superimposed viscous flow, The eff
ective binary diffusivities, Knudsen diffusivities, and the Darcy cons
tant for viscous flow were estimated from the experimental measurement
s. A knowledge of these parameters is a prerequisite for modelling of
the reactive catalyst.