Feed selection for catalytic reforming: Rank the following naphtha sources in order of preference as feedstock to a catalytic reformer (best first), considering octane gain potential and contaminants: virgin naphtha, catalytic naphtha, coking naphtha.

Introduction / Context:
Catalytic reforming raises gasoline octane by aromatization and isomerization of naphtha. Feed selection affects catalyst life, hydrogen production, and octane uplift. Naphthas differ by origin: straight-run (virgin), catalytic (already processed), and coker (olefinic/contaminant-prone).

Given Data / Assumptions:

• Reformer uses Pt/acid bifunctional catalysts.
• Desulfurized, denaphthenized, and dried feed is assumed but relative quality still matters.
• Preference is judged by octane response and fouling propensity.

Concept / Approach:
Virgin naphtha (especially naphthenic) responds best, giving large octane increase with manageable coke. Catalytic naphtha has already undergone conversion; its residual reforming potential is lower, making it second choice. Coker naphtha often contains diolefins, sulfur/nitrogen, and gum precursors, which poison catalysts and increase coke—least preferred.

Step-by-Step Solution:

Verification / Alternative check:
Reformer design texts emphasize straight-run feeds with significant naphthene content for best aromatization and lowest fouling, while coker naphtha requires severe hydrotreating and still underperforms.

Why Other Options Are Wrong:

Common Pitfalls:
Equating high olefin content with reforming benefit; reformers prefer paraffinic/naphthenic feeds, not unstable olefinic streams.

Final Answer:
virgin naphtha → catalytic naphtha → coking naphtha