Page 50 - Modeling of Chemical Kinetics and Reactor Design

20 Modeling of Chemical Kinetics and Reactor Design

Chain transfer

CH + C H  → CH + C H * 5 (1-82)

*
k 2
2
4
2
3
6
Propagation
CH → CH + H * (1-83)

*
k 3
2 5 2 4
H + C H  → H + C H * 5 (1-84)

*
k 4
2
6
2
2
Termination
H + C H  → C H 6 (1-85)

*
*
k 5
5
2
2
High temperatures, electromagnetic radiation, ionizing radiation, or
highly reactive chemical initiators often generate active centers.
POLYMERIZATION KINETICS
Many polymerization reactions proceed by free radical mechanisms.
The following is a sequence of elementary steps for the polymeriza-
tion reaction:
1. Dissociation of initiator (I) into two radical fragments

I → R + R * (1-86)
*
k D
2. Addition of initiator monomer M

R + M  → RM * (1-87)
*
k i
3. Chain propagation

RM + M  → RMM * (1-88)

*
k P
RMM + M  → RMMM * (1-89)

*
k p
RMMM + M  → RMMMM * (1-90)

*
k P