Octane quality from two-stage fluidised catalytic cracking (FCC)\nGasoline produced via a two-stage FCC process typically has an octane number closest to ______.

Introduction / Context:
FCC is a primary refinery conversion unit producing high-octane gasoline rich in isoparaffins and aromatics. Two-stage or enhanced-severity FCC configurations aim for improved octane and yield profiles.

Given Data / Assumptions:

• Octane number refers to research octane (RON) range commonly cited for FCC gasoline blends before further treating.

Concept / Approach:
Typical FCC gasoline exhibits high RON (low 90s) due to isomerization and aromatisation reactions over acidic zeolite catalysts. Two-stage FCC or high-severity modes can push octane further than simple cracking but not generally to the extreme upper 90s without additional reformate blending. Hence, 92 is a representative value among the options listed.

Step-by-Step Solution:

Verification / Alternative check:
Plant data and textbooks report FCC gasoline RON typically around 90–95 depending on severity and feed; 92 is a standard benchmark figure.

Why Other Options Are Wrong:

• 80/87 are low for FCC gasoline.
• 97 is unusually high for straight-run FCC gasoline without reformate/oxygenates.

Common Pitfalls:
Confusing pool octane (after blending) with individual stream octane.

Final Answer:
92