Across common crude fractions, identify which cut generally contains the maximum sulphur under typical refinery slates: diesel, gasoline, naphtha, or atmospheric residue.
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AGasoline
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BDiesel
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CNaphtha
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DAtmospheric residue
Answer
Correct Answer: Atmospheric residue
Explanation
Introduction / Context:Sulphur is naturally present in crude oil as organosulphur compounds. Its distribution varies by boiling range; heavier fractions typically carry higher sulphur and more complex species, challenging desulphurization.Given Data / Assumptions:
- Fractions compared: gasoline, naphtha, diesel, atmospheric residue.
- Modern refineries often hydrotreat light streams to very low sulphur.
- Crude slate and processing affect absolute values but not the general trend.
Concept / Approach:Heavier fractions (residua) hold larger, more refractory sulphur compounds (e.g., polyaromatics with sulphur). Light fractions can be upgraded to ultra-low sulphur via hydrotreating, while residue remains sulphur-rich unless subjected to deep conversion (coking, resid hydrodesulphurization).Step-by-Step Solution:
1) Rank sulphur by boiling range: residue > diesel > naphtha ~ gasoline (post-hydrotreating).2) Identify the fraction with the highest sulphur: atmospheric residue.3) Select “Atmospheric residue.”Verification / Alternative check:Assay data consistently show higher sulphur content in residua compared with lighter cuts.
Why Other Options Are Wrong:
Gasoline/naphtha: normally hydrotreated to very low sulphur.Diesel: contains sulphur pre-treating, but typically far less than residue.Common Pitfalls:Assuming retail diesel sulphur levels reflect untreated streams; finished diesel is hydrotreated to spec.
Final Answer:Atmospheric residue