Catalytic cracking fundamentals: Which catalyst type is characteristically used to crack heavier hydrocarbons into lighter gasoline-range molecules?

Introduction / Context:
Catalytic cracking is a core conversion process in refineries to transform heavier feeds into gasoline, LPG, and lighter distillates. The catalyst determines activity, selectivity, and stability under high temperature and metal/steam exposure.

Given Data / Assumptions:

• We are referring to conventional catalytic cracking (e.g., FCC) principles.
• Options include materials used in other processes or as supports.
• Exam-style focus is on classic catalyst families.

Concept / Approach:
Historically, amorphous silica–alumina catalysts were used. Modern FCC catalysts are zeolite-based (Y-type) supported on silica–alumina matrices. In basic petroleum exams, “silica–alumina” is the expected umbrella answer for catalytic cracking catalysts.

Step-by-Step Solution:

Verification / Alternative check:
Process texts consistently describe FCC catalysts as zeolitic on silica–alumina supports—validating “silica–alumina” as the family descriptor.

Why Other Options Are Wrong:

• Silica gel: A desiccant/adsorbent; not a cracking catalyst.
• Vanadium pentoxide: Typical in SOx conversion or oxidation catalysts; not FCC.
• Nickel: A hydrogenation/dehydrogenation metal; in FCC feed it is actually a poison that promotes dry gas formation.

Common Pitfalls:
Confusing supports/adsorbents with active acidic cracking catalysts; ignoring that zeolites ride on silica–alumina matrices.

Final Answer:
Silica–alumina