Question

Which of the following statement(s) is/are NOT correct while comparing continuously stirred tank reactor (CSTR) and plug flow reactor (PFR)?

• A. CSTR and PFR are normally operated under steady state condition.
• B. There is complete homogeneity in the CSTR while there are concentration variations within the PFR.
• C. The overall reaction carried out in a PFR is always higher than that in a CSTR for the same total volume.
• D. Reaction kinetics do not play any role in choosing between a CSTR and PFR.

Hint:

Reactor choice depends strongly on reaction order: PFR is superior only for reactions of order greater than one.

Answer 1

The Correct Option is C, D

Statement (A) is correct because both CSTR and PFR typically operate under steady state conditions.
Statement (B) is correct because CSTR is perfectly mixed while PFR has axial concentration gradients. 
Statement (C) is NOT correct: a PFR is only more efficient for reactions of order $>1$. For zero-order or first-order reactions, performance may be equal; hence it is not “always” higher. 
Statement (D) is NOT correct: reaction kinetics play a crucial role in selecting between CSTR and PFR, especially the reaction order and rate. 
Final Answer: (C), (D)