Gasoline quality and reforming chemistry: Pick the incorrect statement regarding octane behavior, reforming objectives, feed selection, and catalysts used in modern gasoline reforming.
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ALower boiling paraffins have higher octane number than higher paraffins.
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BDehydrogenation of naphthenes to aromatics is a desirable reaction in reforming.
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CThe most ideal feedstock for thermal reforming is dearomatised kerosene.
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DCatalyst used in catalytic reforming is platinum on silica-alumina base.
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EIsomerization of normal paraffins to isoparaffins raises octane.
Answer
Correct Answer: The most ideal feedstock for thermal reforming is dearomatised kerosene.
Explanation
Introduction / Context: Gasoline reforming improves octane by rearranging and dehydrogenating hydrocarbons. Understanding correct vs. incorrect statements about octane trends, desired reactions, suitable feeds, and catalysts is essential in refining practice.
Given Data / Assumptions:
- Focus on conventional process knowledge: thermal vs. catalytic reforming.
- Paraffinic/naphthenic naphtha ranges are typical feeds.
- Platinum on bifunctional supports is the standard catalyst family.
Concept / Approach: Lower boiling (shorter chain) paraffins typically show higher octane than heavier normal paraffins; dehydrogenation of naphthenes to aromatics increases octane; Pt on silica-alumina (often chlorided alumina) is standard for catalytic reforming. "Dearomatised kerosene" is not an ideal thermal reforming feed; reforming targets naphtha—not kerosene—with significant naphthene content for octane uplift.
Step-by-Step Solution:
1) Validate (a): octane decreases with increasing straight-chain length in normal paraffins; thus (a) is true.2) Validate (b): converting naphthenes to aromatics is a classic desired reforming reaction raising octane and producing hydrogen.3) Validate (d): platinum on acidic support is canonical for catalytic reforming.4) Evaluate feed claim (c): kerosene boiling range is too heavy; thermal reforming of kerosene is neither "most ideal" nor standard compared to naphtha feeds.Verification / Alternative check: Refining textbooks specify straight-run naphtha (naphthenic/paraffinic) as reforming feed; catalytic reforming replaced thermal reforming due to selectivity and octane gains.
Why Other Options Are Wrong:
(a) True — hence not the incorrect statement.(b) True — desired reaction pathway.(d) True — common catalyst base.(e) True — isomerization improves octane by increasing branching.Common Pitfalls: Confusing reforming with hydrocracking; reforming chiefly rearranges and dehydrogenates, not deep cracking of kerosene feeds.
Final Answer: The most ideal feedstock for thermal reforming is dearomatised kerosene.