ABSTRACT
The chain mechanism is complicated when two hydrocarbons are oxidized simultaneously.
Russell and Williamson [1,2] performed the first experiments on the co-oxidation of
hydrocarbons with ethers. The theory of these reactions is close to that for the reaction
of free radical copolymerization [3] and was developed by several researchers [4-9]. When
one hydrocarbon R1H is oxidized in the liquid phase at a sufficiently high dioxygen
pressure chain propagation is limited only by one reaction, namely, R1OO .þR1H. For
the co-oxidation of two hydrocarbons R1H and R2H, four propagation reactions are import-
ant, viz,
R1OO . þR1H ! R1OOHþR .1 (kp11)
R1OO . þR2H ! R1OOHþR .2 (kp12)
R2OO . þR2H ! R2OOHþR .2 (kp22)
R2OO . þR1H ! R2OOHþR .1 (kp21)
In addition to cross-propagation reactions, one cross-termination reaction is introduced in
addition to two self-termination reactions, viz,
R1OO . þR1OO. ! Termination (kt11)
R1OO . þR2OO. ! Termination (kt12)
R2OO . þR2OO. ! Termination (kt22)
When the kinetic chain length is high, the rate of total oxygen consumption is
dD[O2]
dt ¼ (r1[R
1H]2 þ 2[R1H] [R2H]þ r2[R2H]2) ffiffiffivip
1H]2 þ fr1r2d1d2[R1H] [R2H]þ r22d22[R2H]2)1=2 (5:1)
where
r1 ¼ kp11 kp12
; r2 ¼ kp22 kp21
; d1 ¼ ffiffiffiffiffiffiffiffiffiffi
2kt11 p kp11
; d2 ¼ ffiffiffiffiffiffiffiffiffiffi
2kt22 p kp22
and f ¼ kt12ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi kt11kt22 p :
Figure 5.1 illustrates the effect of hexamethylbenzene that produces a secondary peroxyl
radical on the oxidation of cumene [9].
