Vacuum distillation heavy gas oil (VGO): What is the principal refinery use of VGO produced from the vacuum unit?

Introduction / Context:
Vacuum distillation separates high-boiling atmospheric residue into vacuum gas oils and vacuum residue. Vacuum gas oil (VGO) is a critical intermediate for conversion units that upgrade heavy molecules into lighter, high-value transportation fuels.

Given Data / Assumptions:

• VGO boiling range: roughly 340–560°C (indicative).
• Downstream conversion paths include FCC and hydrocracking.
• Objective: maximize gasoline/diesel yield from heavy fractions.

Concept / Approach:
The FCC unit catalytically cracks VGO into gasoline, LPG, light cycle oil, and other products. VGO properties (CCR, metals, sulfur) are tailored via vacuum cut points. While some VGO may be hydrocracked, the canonical destination in a catalytic cracking refinery is the FCC.

Step-by-Step Solution:
Identify stream → VGO from vacuum distillation.Match to unit → FCC is the standard cracking route.Conclude primary use → FCC feedstock.

Verification / Alternative check:
Refinery flow schemes show VGO routed to FCC or hydrocracker; FCC is the most common in gasoline-oriented configurations.

Why Other Options Are Wrong:

• Kerosene/gasoline blending: VGO is too heavy; would fail volatility specs.
• “None of these”: incorrect since FCC is correct.
• Lube base oil: requires severe hydroprocessing and dewaxing; VGO alone is not directly suitable.

Common Pitfalls:
Confusing VGO with vacuum residue; residue often goes to coking or asphalt, not FCC.

Final Answer:
As feedstock to the fluid catalytic cracking (FCC) unit