In petroleum refining, what is the typical straight-run yield of diesel obtained directly from crude oil atmospheric distillation (i.e., before any cracking or conversion processes)?

Introduction:
Diesel obtained directly from atmospheric (straight-run) distillation of crude oil forms a modest portion of the barrel before any conversion units like cracking or hydrocracking are applied. Knowing this typical yield helps in preliminary refinery material balance and economics.

Given Data / Assumptions:

• Straight-run means no cracking or conversion has been performed.
• Typical mixed crude slate (not an extreme light or heavy crude).
• We are estimating a representative percentage range rather than an exact constant.

Concept / Approach:
The atmospheric column separates crude by boiling range. Straight-run diesel cuts (roughly 180 to 360 C range) usually emerge in the high-teens to ~20s percent by volume for many common crudes. Conversion units later boost diesel pool volumes, but those are not counted here.

Step-by-Step Solution:
1) Identify product of interest: straight-run diesel only.2) Use typical refinery heuristics: SR diesel yield commonly lies around the high-teens to low-20s percent of crude.3) Compare with options and select the nearest representative percentage.

Verification / Alternative check:
Industry planning heuristics and refinery textbooks often cite SR diesel yields near ~15–25 percent depending on crude. A mid-teens to high-teens figure is a conservative representative choice for a generic crude mix.

Why Other Options Are Wrong:
8 percent: Too low for typical mixed crudes.28 percent: More characteristic of diesel after conversion blending, not just straight-run.35 percent: Unusually high for SR alone.None of the above: Not applicable because a plausible typical value is listed.

Common Pitfalls:
Confusing total diesel pool (after cracking/hydrocracking) with straight-run diesel only can inflate the expected number. Crude type variability also misleads if a single fixed value is assumed.

Final Answer:
18 percent