Fuels – Paraffins, aromatics, naphthenes, olefins

Acidity in petroleum products as per ASTM D8045

View of an oil refinery

ASTM D8045, released in 2016, describes the determination of the acid number in crude oil and petroleum products with thermometry. This method offers a variety of advantages over potentiometric titration:

  • Analyses yield a well-defined end point, thus improving reproducibility of results
  • Analyses are much faster
  • Sensor maintenance is not required

> Learn more about thermometry and ASTM D8045

In step with international standards

Standards
The importance of fossil fuels is reflected by the large number of standards relating to them. Metrohm as a leading manufacturer of analytical instruments offers long-standing application know-how for quality control of fossil fuels.

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Acid and base numbers – Important quality parameters

Industrial plant at dusk
In the same way as the base number (BN) is a sum parameter for alkaline compounds, the acid number (AN) is a measure for acidic compounds. Both parameters are crucial to assure the quality of the oil.

Potentiometric titration

Both parameters are determined by potentiometric titration in nonaqueous solvents or solvent mixtures. Titrimetric determinations can be completely automated – from the addition of solvents to the reproducible cleaning of the electrode. Oil samples can even be weighed in fully automatically before titration. This guarantees complete traceability.

Photometric titration in line with ASTM D974

AN and BN may also be determined by photometric titration with color indication of the equivalence point according to ASTM D974. For this application, Metrohm offers the 100% solvent-resistant Optrode with the possibility to automate photometric titration.







Related products

Fast thermometric titration

Acid number determination can be done easily and quickly in accordance with ASTM D8045 using thermometric titration. Electrode maintenance is not an issue when using thermometric titration. Contamination and matrix influences do not impair the sensor. It also works without rehydration. In comparison to potentiometric titration, thermometric titration is approximately three times faster and can be fully automated, as shown in the TAN determination of the titration curve. 

> Learn more about thermometric titration (as per ASTM D8045)

> Learn more about the Titrotherm instrument for thermometric titration

Solvotrode easyClean: a combined pH glass electrode that can be easily cleaned even of strong contamination.

Optrode: Sensor for titration with photometric endpoint recognition.

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Water determination in petroleum products

Petrochemical plant
Water occurs as a contaminant in virtually all petroleum products.

It reduces lubricant properties, promotes microbial oil degradation, leads to sludge formation in the tank, and promotes corrosion.

Therefore, it is very important to know the water content of petroleum products. Karl Fischer (KF) titration, owing to its excellent reproducibility and accuracy as well as its ease of use, ranks amongst the most important water determination methods and accordingly figures in numerous international standards. Because of the low water content in petroleum products, KF coulometry is usually applied.

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Halogen and sulfur in fuels by Combustion Ion Chromatography (CIC)

Combustion IC diagram
Adverse effects of halogen- and sulfur-containing fuels

The burning of sulfur-containing fuels leads to the emission of air-polluting sulfur oxides into the atmosphere. Additionally, high sulfur concentrations negatively impact engine performance. Similarly, the presence of corrosive halogens must be minimized, in particular with regard to the refining process.

Combustion IC

Combustion IC is a fully automated method for the pyrohydrolytic determination of individual halogen and sulfur in a multitude of petro products, regardless of whether they are in liquid, solid, or gaseous form. CIC excels in terms of sample throughput, measuring range, and precision as well as accuracy.

The image above shows the Combustion IC method. The gaseous combustion products that exit the oven are fed into an oxidizing absorption solution and detected as sulfate and halide by way of subsequent ion chromatography.

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NIRS for optimizing blending and refinery processes

NIRS Process image of the RON
Straightforward blending process with NIRS

During the blending process, different fractions of the crude oil distillation are mixed together so as to produce the ready-to-sell diesel or gasoline grades. This is most economical when it is carried out in process systems that work online and can be automated. The endpoint of the blending process is reached when the required fuel specifications are achieved. Key characteristics which indicate the progress of the blending process are the cetane number for diesel blends and one of the octane ratings for gasoline blends. NIRS sensors located directly in the process enable the entire process to be controlled and ensure a high-quality end product. Additional parameters can be monitored in parallel.
To refine crude oil and natural gas into diverse petrochemical products, complex processes are required, from crude oil distillation, cracking, and desulfurization to reforming. All these processes are controlled by near-infrared spectroscopy (NIRS) – whether to determine characteristics or the composition of petroleum products.

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Process image (image on the left side) of the Research Octane Number (RON) and Reid vapor pressure control parameters determined during the blending process of gasoline using NIRS. Both parameters can be tracked simultaneously via the live view on the control panel (the black/green section between the two trend curves).

Read more Process Analytics applications

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Further applications

Autolab cell and PGSTAT204

Corrosion

In the petrochemical and biofuel industry, corrosion is a common problem that threatens man and machine and that generates significant production costs. It has been reported that in the USA alone pipeline corrosion accounts for over 20 million US dollars per year. Metrohm Autolab offers a complete product range for investigating the corrosion properties of materials, both for pure and applied research.

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Testimonial: CEPSA Research Center

"For over 30 years, our laboratories have had Metrohm equipment, such as titrators to measure surfactants in detergents and the bromine number in olefins as well as the oxidation stability of FAMES and diesel oil. They are all very useful and reliable pieces of equipment."

Cepsa is a Spanish energy company active in the oil and gas sector. They use numerous Metrohm instruments for the characterization of oils and fuels.