Diesel ignition quality improvers: Which additive is commonly used to increase the cetane number of diesel fuels (thereby shortening ignition delay in compression-ignition engines)?

Introduction / Context: Cetane number reflects how readily diesel auto-ignites under compression. Higher cetane numbers reduce ignition delay and promote smoother combustion. Chemical additives can boost cetane where base fuel quality is insufficient.

Given Data / Assumptions:

• Focus on compression-ignition (CI) diesel engines.
• Consider classical improvers used at ppm–low thousands ppm dosages.
• Distinguish from gasoline octane improvers.

Concept / Approach: Nitrate/nitrite esters (e.g., amyl nitrate, 2-ethylhexyl nitrate) act as cetane improvers by decomposing to yield radicals that facilitate low-temperature oxidation, thereby shortening ignition delay. TEL raises octane for SI engines and does not improve diesel cetane. Mercaptans are odorants; naphthenic acids are part of crude chemistry and are not cetane improvers.

Step-by-Step Solution:

Verification / Alternative check: Fuel additive references list 2-ethylhexyl nitrate and amyl nitrate as standard cetane improvers with strong response in poor-ignition gasoils.

Why Other Options Are Wrong:

Common Pitfalls: Mixing octane improvers (SI) with cetane improvers (CI); they target opposite ignition behaviours.

Final Answer: Amyl nitrate