Elements of
Chemical Reaction Engineering
6th Edition



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Essentials of
Chemical Reaction Engineering
Second Edition

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Chapter 14: External Diffusion Effects on Heteregeneous Reactions

Example: Relative Rates of Diffusional Transport

What are the relative rates of transport of a through a stagnant gas and equal molar counter diffusion for the same concentration boundary conditions. Recall the relative concentration profiles were

EMCD

Stagnant film

Ratio of transport rates

Let yAs = 0 @ surface (e.g., infinite reaction)

We now will compare the relative rates as a function of the mole fraction, yAb, of the diffusing species, A, at the upper boundary z = 0.

y Ao

0.999

0.99

0.90

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

R

6.91

4.65

2.56

2.01

1.72

1.53

1.39

1.28

1.19

1.12

1.65

yAo


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