ANS:A - Amyl nitrate

Among the options provided, Amyl nitrate is an additive that is known to improve the cetane number of diesel fuel. Here’s why:

• Cetane Number: The cetane number is a measure of the ignition quality of diesel fuel during compression ignition (diesel) engines. It indicates how readily the fuel ignites when injected into the engine cylinder.
• Amyl Nitrate: Amyl nitrate is sometimes used as a cetane improver in diesel fuel. It works by promoting more rapid ignition and combustion of the fuel, similar to how octane improvers (like tetraethyl lead in gasoline) enhance the octane number.
• Other Additives:
  • Ethyl Mercaptan: This compound is not used to improve cetane number; it is primarily used as an odorant in natural gas and propane to detect leaks.
  • Naphthenic Acid: Naphthenic acids are not used as cetane improvers; they are typically found in crude oil and can cause corrosion in engines if not properly neutralized.
  • Tetra Ethyl Lead: This is used as an octane enhancer in gasoline, not for diesel fuel.