Re. Hayes et al., INTRAPHASE DIFFUSION AND INTERPHASE MASS-TRANSFER EFFECTS DURING THE CATALYTIC-OXIDATION OF CO IN A TUBE WALL REACTOR, Proceedings - Royal Society. Mathematical and physical sciences, 448(1933), 1995, pp. 321-334
Chemical kinetics of catalytic reactions are often obscured by intraph
ase diffusion and interphase mass transfer effects. Such complexities
are especially true of catalytic combustion reactions effected within
multichannel monoliths whose channel walls are coated with a catalyst
layer. Assessment of the extent of intraphase and interphase resistanc
es to the catalytic conversion of low concentrations of carbon monoxid
e in air were achieved by conducting experiments in a tube wall reacto
r, the walls of which were coated with a platinum-alumina deposit. Res
ults indicated that, for a 1.34% CO in air mixture, kinetics below 610
K were less than first order with an activation energy of 30.4 kJ mol
-1. Above 610 K there was strong evidence of both intraphase and inter
phase resistances to catalytic conversion, the overall kinetics displa
ying an apparent activation energy of 11.7 kJ mol-1. Near to the react
or tube entrance where the temperature was about 650 K, the mass trans
fer resistance from fluid to tube wall was only one-sixth that of the
diffusive resistance within the thin catalyst washcoat, increasing to
one half of the diffusive resistance at the tube exit where the temper
ature was about 820 K. Computer estimations of the performance of the
tube wall reactor, using measured kinetic data for a small element of
reactor containing catalyst deposited on the wall and interphase heat
and mass transfer data estimated from first principles assuming lamina
r flow, are in satisfactory agreement with the measured performance of
the whole tube wall reactor.