Page 36 - Modeling of Chemical Kinetics and Reactor Design

6 Modeling of Chemical Kinetics and Reactor Design

SULFUR DIOXIDE OXIDATION

The overall stoichiometric equation is:

SO + 1 O [ SO (1-8)
2 2 2 3

Mechanism

Vanadium pentoxide, V O , is used as a catalyst in the oxidation
2
5
of sulfur dioxide. The mechanism involves oxidation-reduction of V O 5
2
that exists on the support at operating conditions in the molten state.
The mechanism of reaction is:

2−
1. SO + 2 V 5+ + O [ SO + 2 V 4+ (1-9)

3
2
2 [
1 V [ 5+ −
4+
2. O + V + O 2] (1-10)
2
2 [
1 − 4+ 5+ 2O ]
−
3. O + V [ V + (1-11)
2
+
−
4. O + V [ V 5 + + O 2 − (1-12)
4

AMMONIA SYNTHESIS
The overall stoichiometric equation is:
1 3
N + H → NH (1-13)
2 2 2 2 3
Studies of ammonia synthesis on iron catalyst suggest that the
reaction occurs through surface imine radicals.

Mechanism

The following elementary steps are:

1. N → 2N (1-14)
2(g) (ads)
2. H → 2H (1-15)
2(g) (ads)
3. N + H → NH (1-16)
(ads) (ads) (ads)