Chemistry Reference
In-Depth Information
6
4
CECD
CEEC
2
1g (
K
e
)
0
-2
-4
-6
*10
-3
K
-1
0
2
4
6
8
10
1 /
T
FIGURE 4.4
The constant
K
e
(
T
g
)
for the quasi-equilibrium states CEEC and CECD in the
closed reactor. Rate constants as in Table 4.1 and in Figure 4.2.
k
5
γ
2
n
.
K
∞
(
T
g
)
=
K
0
(
T
g
)
=
K
e
(
T
g
)
≈
(4.12)
The conditions of the coincidence of the chemical compositions of the two quasi-
equilibria is of considerable interest. Surprisingly, numerous experimental results
confirm the suggestion that this is a more general case: Nonthermal plasma chemical
conversion tends to reach CEEC
CECD.
The kinetic background of the chemical quasi-equilibrium states has been
extensively studied for different nonthermal plasma chemical systems, consid-
ering all relevant species and elementary reactions (see [2,4,5]) Generally, for
CEEC
=
=
CECD the following conditions must be fulfilled:
•
The gain and loss processes for stable final products are determined at
vanishing power input (
P
→
0) only by the collisions of neutral particles.
The most important role of electron collisions is the generation of unstable
intermediate particles (atoms, radicals, excited species) which influence the
gain and loss of the final products, e.g.,
O
2
+
e
→
O
+
O
+
e
,
O
+
O
2
+
M
→
O
3
+
M
and
O
3
+
O
→
2O
2
.
e
.
•
Quadratic processes of unstable intermediate products are of minor
importance, e.g.,
Disturbing process for the equalization: O
3
+
e
→
O
2
+
O
+
O
+
O
+
M
→
O
2
+
M
,
O
−
+
O
→
O
2
+
e
and
2O
2
(
a
1
g
)
+
O
2
→
2O
3
.
