Catalytic vs thermal cracking: Which statement is incorrect regarding cracking behaviour and heat effects in petroleum refining?

Introduction:
This question compares kinetic and thermal aspects of thermal and catalytic cracking. The goal is to identify the statement that does not align with established refining science.

Given Data / Assumptions:

• Cracking can be thermal or catalytic.
• Iso-paraffins vs n-paraffins show different cracking tendencies.
• Catalyst regeneration burns coke and is exothermic.
• Olefins are highly reactive on acidic catalysts due to hydrogen transfer and oligomerization pathways.

Concept / Approach:
Acidic cracking catalysts (e.g., zeolites) lower activation energies and accelerate reactions at lower temperatures than thermal processes. Olefins are particularly reactive under catalytic conditions because of carbocation mechanisms and hydrogen transfer reactions.

Step-by-Step Solution:

Verification / Alternative check:
Refining texts consistently note rapid olefin conversion over acidic catalysts, improving gasoline stability by reducing olefin content.

Why Other Options Are Wrong:

• Option A: Correct relationship; not the incorrect statement.
• Option B: Correct heat accounting for cracking vs regeneration.
• Option D: Invalid because C is already incorrect.
• Option E: True statement about hydrogen transfer.

Common Pitfalls:
Assuming “faster at higher temperature” (thermal) automatically beats catalysis; overlooking the role of hydrogen transfer in catalytic systems.

Final Answer:
Decomposition of olefins in catalytic cracking is slightly slower than in thermal cracking.