Definition check in petroleum terminology In refinery and crude assay language, a “sour crude” refers to a crude oil that contains appreciable amounts of which class of compounds?

Introduction / Context:
Crudes are broadly classified as “sweet” or “sour,” a distinction that drives refinery processing severity, hydrogen demand, and product sulphur specifications. Recognising what makes a crude “sour” is essential for understanding hydrotreating loads and corrosion management.

Given Data / Assumptions:

• The term “sour” is a standard industry descriptor.
• We seek the primary chemical reason behind the label.
• Other heteroatom compounds may be present but are not the defining feature for “sour.”

Concept / Approach:
“Sour” denotes significant sulphur-containing species (e.g., hydrogen sulphide, mercaptans, sulphides, thiophenes). These compounds raise corrosion risk, poison catalysts, and necessitate desulphurisation. While asphalt (asphaltenes), wax (long-chain paraffins), and nitrogen compounds influence processing, they do not define the “sour” classification.

Step-by-Step Solution:

Verification / Alternative check:
Crude specs list total sulphur wt% as the headline measure for sweetness; many trading contracts price based on sulphur grade.

Why Other Options Are Wrong:

• Asphalt / Wax: Affect viscosity, pour point, and residue yield, not “sourness.”
• Nitrogen compounds: Important for catalyst poisoning and color, but not the naming basis.

Common Pitfalls:
Equating dark color or high viscosity with sourness; a crude can be heavy yet sweet if sulphur is low.

Final Answer:
Sulphur compounds