Determination of Damaging Compounds in Fuels

Sulfur compounds in petroleum products not only have an unpleasant odor, they are also environmentally damaging and promote corrosion. Fuels also contain mercaptans which are oxidized by iodine and thus falsely indicate a water content that is too high.

Metrohm has many years of experience determining various compounds in Jet Fuel and Kerosene. We’ll make sure that your values are accurate.

Regulatory Requirements and Applications

Total Acid Number by ASTM D3242
The acid and base number may also be determined by photometric titration with color indication of the equivalence point. Metrohm offers a unique optical electrode called the Optrode, a new sensor for photometric titration. It is 100% solvent resistant thanks to its inert glass shaft. Another key advantage of the Optrode is its capacity for automation.

Water Content in Jet Fuel by ASTM D4377 & D4928
Fuels contain mercaptans that are oxidized by iodine and can falsely indicate a high water content. The problem is addressed by adding N-ethylmaleimide,  which causes the SH groups of the mercaptan to add to the double bond of N-ethylmaleimide. Normally the water content in fuels is determined by coulometric titration. With volumetric titration, a solubility promoter must be added to the methanol.

Hydrogen Sulfide & Mercaptans by ASTM D3227
Sulfur compounds in petroleum products not only have an unpleasant odor, they are also environmentally damaging and promote corrosion. For determining hydrogen sulfide and mercaptans in gasoline, kerosene, naphtha, and similar distillates, the sample is titrated with a silver nitrate solution. In this titration silver sulfide (Ag₂S) and silver mercaptide are produced and two pronounced potential jumps occur. The first endpoint corresponds to hydrogen sulfide (H₂S), the second to the mercaptans. The indicator electrode for the titration is the Ag-Titrode with Ag₂S coating. Since both H₂S and mercaptans are oxidized by atmospheric oxygen and the arising oxidation products cannot be determined titrimetrically, work must be carried out under nitrogen atmosphere.

Organic Halides and Sulfur by Combustion IC
The burning of sulfur-containing fuel leads to the emission of air-polluting sulfur oxides into the atmosphere. Furthermore, high sulfur concentrations have an adverse effect on the ease of ignition of fuels and their stability during storage. Halogen concentrations in the refinery process must also be analyzed due to the corrosion risk. As a result, a fast and reliable method for determining the halogen and sulfur contents is required.

The Combustion IC method is captivating, not only due to its outstanding precision, but also because it has higher sample throughput.

Jet Fuel Testing by Near-IR Spectroscopy
Monitoring jet fuel properties is important because the fuel used in aircrafts must meet rigorous specifications. Near-infrared spectroscopy (NIR) is a fast method for fuel analysis. Metrohm developed a unique calibration solution for jet fuels testing in the laboratory.

The parameters that can be determined by NIR include:
• API gravity
• Density at 15°C
• Aromatic content
• Cetane index
• Boiling profiles at 10%, 20%, 50% and 90% recovery
• Flash point
• Freeze point
• Hydrogen content
• Viscosity at -20 °C