WOLFRAM|DEMONSTRATIONS PROJECT

Driving a Reaction by Chemical Coupling

​
temperature (K)
900
pressure (atm)
1
1,3-Butadiene can be produced by the gas-phase catalytic dehydrogenation of 1-Butene by the reaction
C
4
H
8
⇌
C
4
H
6
+
H
2
. To suppress the reverse reaction, an inert gas (e.g. steam) can be added to the feed stream of the reactor. Instead, we choose here to add
CO
2
to the reactor. Assume a suitable catalyst is present for the water-gas shift reaction
CO
2
+
H
2
⇌CO+
H
2
O
; this second reaction consumes
H
2
. Therefore, in accordance with Le Chatelier's principle, higher conversion for the dehydrogenation should be achieved. This Demonstration illustrates how one can drive a chemical reaction (i.e. the dehydrogenation reaction) by coupling to a second reaction.
The coupling factor is equal to the number of moles of carbon dioxide added per mole of 1-Butene. The Demonstration computes the equilibrium conversion versus the coupling factor using the Gibbs free energy minimization method. You can set values of the temperature
T
in kelvin as well as the pressure
P
in atm. Here, only low to moderate values of pressure are allowed. Thus, the gas mixture can be assumed to be ideal.
In accordance with Le Chatelier's principle, you can verify that:
1. The conversion is greater when more carbon dioxide is added to the reactor.
2. The conversion is greater when you increase the temperature. Indeed, this reaction is endothermic (
Δ
o
H
298.15
=109.780kJ/mole
, where
H
is the enthalpy).
3. The forward reaction is favored by low pressures. Indeed, there are more moles of product than reactant (
Δ
ν
i
=+1
, where
ν
i
is the stoichiometric coefficient of species
i
).