Diesel ignition quality improvers Which additive is commonly used to increase the cetane number of diesel fuel in refinery blending or aftermarket treatment?

Introduction / Context:
Cetane number indicates the ignition quality of diesel fuel—the higher the cetane, the shorter the ignition delay and the smoother the combustion. Refiners and blenders sometimes add cetane improvers to meet specifications, especially when feedstocks or seasonality reduce natural cetane.

Given Data / Assumptions:

• The question asks for a typical cetane improver used in practice.
• Leaded gasoline additives (tetraethyl lead, tetramethyllead) relate to octane, not cetane.
• We focus on the generic compound class, not a specific brand.

Concept / Approach:
Nitrate-based additives (e.g., ethyl nitrate, 2-ethylhexyl nitrate) are widely used cetane improvers. They decompose to yield radicals that promote low-temperature pre-flame reactions, thereby reducing ignition delay. Tetraethyl lead and tetramethyllead are historical anti-knock agents for spark-ignition gasoline, not diesel cetane boosters, and are phased out for environmental reasons.

Step-by-Step Solution:

Verification / Alternative check:
Fuel additive references list nitrate esters as the go-to cetane improvers, with typical treat rates in ppm to low thousands depending on base fuel quality.

Why Other Options Are Wrong:

• Tetraethyl lead / Tetramethyllead: Gasoline octane improvers, environmentally restricted; not used for diesel cetane.
• None of these: Incorrect because a valid cetane improver is listed.

Common Pitfalls:
Confusing octane (spark-ignition anti-knock) with cetane (compression-ignition ignition quality).

Final Answer:
Ethyl nitrate