Chemical Engineering - Chemical Reaction Engineering - Discussion

@Ryzer

No, in a CSTR, reactant concentration is low, because there is continuous mixing. Whereas in a PFR, concentration is high only at the beginning and decreases along the length of the reactor. Therefore, we want to use a PFR here to maximize the conversion since it starts at a high CA. So D is correct.

No, I think option A is the correct answer.

There are a few types here, the actual given should be:

A --> R, rR = K1.CA^2; E1 = 80 KJ/mole.
A --> S, rS = K2.CA; E2 = 120 KJ/mole.

Solving for the selectivity:

S_R/S = rR/rS = K1 * CA^2/K2 * CA = (K1/K2) * CA.

The selectivity is directly proportional to CA. As CA increases, the selectivity S_R/S increases. Therefore, to maximize the selectivity of R, we need to maximize CA. We know that in a CSTR, the initial concentration inside the reactor is immediately at CA, while for a PFR the initial concentration at the inlet starts from 0 until it reaches CA along the length of the reactor. Therefore, we want to use a CSTR here to maximize the conversion since it starts at a high CA.


@Usman.

As you mentioned the Higher temperature favours the reaction with a higher activation energy, and we don't want that (since E1 < E2) so the temperature should be low, but not too low.

Therefore, the answer should be (A) low temperature in a CSTR.

I think the right answer is C.

Yes, the answer is C.

E (u) >E (d), the reaction should be carried out at low temperature to maximize the selective of the desired product. But not so low that the desired reaction does not proceed to any reasonable extent.

The answer must be 'c'.

Because --- selectivity=R/S=k1ca/k2.
So, conclusion is - we require a high concentration of A means we required PFR.
we require lower temperature.

Yes, the answer should be C.

High temperature favors reaction with high activation energy so it should be C.