Page 87 - Modeling of Chemical Kinetics and Reactor Design

Reaction Mechanisms and Rate Expressions 57

Propagation


*
3. CH → CH + H * (1-247)
k 3
2
4
2
5

*
*
*
k 4
4. H + C H  → C H + H 2 (1-248)
5
2
6
2
Termination
*
*
5a. CH + CH  → C H (1-249)
k a5
2 5 2 5 4 10
5b. CH + CH  → CH + CH 6 (1-250)
*
*
k b5
4
2
5
2
2
5
2
Applying the steady state approximation gives
( +r ) = dC CH 3 ∗
CH 3 ∗ dt
dC *
= 2 kC − k C C = 0 (1-251)
CH 3 2
2
2
dt a 1 C H 6 2 CH 3 * CH 6
( +r ) = dC CH 5 ∗
2
2
CH 5 ∗ dt
dC *
CH 5 = kC C − k C + k C C
2
2
2
dt 2 CH 3 * CH 6 3 CH 5 * 4 H * CH 6
2
− ( 2 k + k )C 2 = 0 (1-252)
5a 5b CH * 5
2
and
( +r H ∗ ) = dC H ∗
dt
dC
H * = kC − k C C =0 (1-253)
2
dt 3 CH 5 * 4 H * CH 6
2