Compared with thermal cracking of vacuum residue, catalytic cracking typically produces what notable difference in the gasoline (petrol) product slate and quality?

Introduction:
Refineries convert heavy vacuum residues into lighter, high-value products using cracking. Catalytic cracking (e.g., FCC) is preferred over thermal cracking because of both yield and quality advantages for the gasoline pool.

Given Data / Assumptions:

• Feed: residue of vacuum distillation.
• Processes compared: thermal cracking vs catalytic cracking (FCC).
• Focus: gasoline yield and quality outcomes.

Concept / Approach:
Catalytic cracking employs acidic zeolite catalysts to promote selective carbon–carbon bond scission, isomerization, and aromatization, producing more gasoline with higher octane numbers versus purely thermal routes.

Step-by-Step Solution:
1) Identify target product metric: gasoline yield and quality.2) Recognize FCC selectivity: higher gasoline yield and higher octane than thermal cracking.3) Select the statement that matches these known outcomes.

Verification / Alternative check:
Standard refinery textbooks and FCC operating data consistently show improved gasoline make and octane with catalytic pathways compared to thermal cracking for similar feeds.

Why Other Options Are Wrong:
Produces lower octane number petrol: Incorrect; FCC gasoline typically has higher octane.Increases sulphur content: Not inherently true; sulphur is feed-dependent and often reduced downstream (e.g., hydrotreating).Increases gum-forming materials: Modern FCC gasoline stability is managed; the statement is misleading.Reduces LPG make by half: Not a standard rule; LPG yield depends on severity and catalyst activity.

Common Pitfalls:
Assuming thermal and catalytic cracking have similar selectivity; ignoring the octane benefit from isomerization/aromatization pathways in FCC.

Final Answer:
Gives higher yield of petrol (gasoline).