G. Ozkan et G. Dogu, A DYNAMIC STUDY ON AXIAL-DISPERSION AND ADSORPTION IN CATALYTIC MONOLITHS, Industrial & engineering chemistry research, 36(11), 1997, pp. 4734-4739
A dynamic procedure was used for the measurement of the axial dispersi
on coefficient, as well as the adsorption equilibrium and rate constan
ts of CO, O-2, CH4, and C3H6 tracers on a monolithic catalyst washcoat
ed by Pt-Al(2)O3. Using a transient axial dispersion model, moment exp
ressions were derived for the inert and adsorbing tracers. From the se
cond central moment of inert tracer response peaks, an average value o
f the axial dispersion coefficient was determined as 2.65 x 10(-4) m(2
)/s for a ceramic monolith containing cells with square cross section.
The results indicated that axial dispersion in such a monolith is hig
her than the corresponding value in a circular tube. The adsorption eq
uilibrium constants of the adsorbing tracers (CO, O-2, CH4, C3H6) and
the heat of adsorptions were determined from the time delay of the res
ponse curves measured in the temperature range of 76-300 degrees C, wh
ile the adsorption rate parameters were evaluated from the second cent
ral moments, A detailed analysis of the results indicated that pore di
ffusion resistance in the Pt-Al2O3 layer is negligible and also that f
ilm mass-transfer resistance is much smaller than the adsorption resis
tance.