Chemistry Reference
In-Depth Information
(a)
Processes in space
P
el
Active zone
Passive zone
Reactants
T
e
>>
T
g
T
e
≈
T
g
Stable
products
A
1
A
2
A
1
A
2
Hot electrons
A
k
Elementary reactions
Dissociation
excitation,
etc.
Recombination
de-excitation,
etc.
A
k
A
l
P
el
Active phase
Time τ
Passive phase
Processes in time
(b)
FIGURE 1.2
Operation scheme of a nonthermal plasma chemical flow reactor (a) and of a
closed reactor (b), with
P
el
electrical power,
T
e
kinetic temperature of electrons, and
T
g
gas
temperature.
The subject of this topic is the
plasma chemistry in nonthermal plasmas
.Inthis
case, the reaction mixture is far from the thermal equilibrium. The chemical conver-
sions are initiated by the high temperature (
T
e
≥
10
4
K) of free electrons at relative low
gas temperature (
T
g
≤
10
3
K) (plasma electrical conversion). The processes take place
under highly nonequilibrium conditions of all plasma species. Hot electrons, ener-
getic ions, cold excited species, free atoms, and radicals are produced in the so-called
active zone (phase) of the different kinds of nonthermal (electrical) gas discharges. In
the passive zone (phase), the electrons cool down fast. The unstable plasma compo-
nents change to stable reaction products by volume and wall reactions. The operation
scheme of nonthermal plasma chemical reactors is illustrated in Figure 1.2.
1.4 SPECIFICS OF NONTHERMAL PLASMA CHEMISTRY
Two important advantages of the application of nonthermal plasma chemistry have
to be emphasized. First, because of the high electron temperature of 10
4
-10
5
K
