Comparison of Select Properties and Sulfur and Nitrogen Species in Low and Ultra Low Sulfur Diesel Fuel

Aromatics, cetane number, density, and lubricity of a large number of retail diesel fuel samples were compared before, during, and after the switch from low sulfur to ultra low sulfur diesel fuel. Also, sulfur and nitrogen speciation was done on a small set of samples to determine the changes in heterocyclic compounds as refiners made the switch. For ultra low sulfur fuel, total aromatics decreased substantially, density decreased slightly, cetane number increased by about 1 - 2 numbers, and lubricity (wear scar) improved slightly relative to low sulfur diesel fuel. Speciation results showed that hydrotreating eliminated thiophenes and benzothiophenes from the fuel. The only sulfur species remaining were dibenzothiophenes, and these were present at very low part per million levels. Nitrogen compounds in the form of carbazoles were either eliminated or reduced to low part per million levels.