Crude Oil

Crude oil is the primary input to the refinery:

Crude oil assays evaluate the physical and chemical composition of crude oil feedstock. Each type of crude oil has unique chemical characteristics that are important to refiners, oil traders and producers globally. Crude oil measurements can vary from a simple yield determination to a complex evaluation of the quality of the crude oil and all of its refined fractions. These evaluations are critical to control corrosion in the refinery and greatly impact the profitability of all refining operations given the potential for significant loss in crude investments and disruptions in the refining process that influence yield, quality, production and environment.

Regulatory Requirements and Applications

Total Acid Number by ASTM D8045
Acid Number (AN) is a critical quality control parameter for crude oil and petroleum products. The accuracy of the AN results has significant influence on the commercial value of crude oil and the profitability of a refinery. Moreover, acidic compounds lead to corrosion in petroleum refining and transportation infrastructure, therefore accurate AN measurements are necessary for safe operation. Given the commercial and corrosion impact of acidic compounds monitored by AN titrations, new method ASTM D8045 is critical to quality control laboratories throughout the industry.

ASTM D8045 uses thermometric titration and improves upon the traditional D664 analysis technique by utilizing a sensor that is unaffected by difficult matrices, requires lower solvent volumes, and completes sample analysis in often less than two minutes.

Total Acid Number by ASTM D664

Even though it is not as effective or reliable as ASTM D8045, many laboratories still measure Acid Number using ASTM D664. Metrohm has proven potentiomentric systems that yield the most accurate results from D664 and provide a high level of automation for worry free analysis.

Chloride by ASTM D6470 & D3227

Chlorides in crude oil form areas of salt accumulation in processing units. These salt accumulations corrode key equipment, especially those that run in low-temperature ranges where hydrogen chloride forms. Refineries constantly optimize the production process to improve the yield of high value products. They lose their profit due to the corrosion to the level of 1 billion per year. Protecting plants against the corrosion caused by sulfur, chloride and other organic acids is important in the context of safety and profitability.

Chloride in crude oil is determined by potentiometric and conductometric methods in accordance with ASTM methods.

Organic Halides by Combustion IC

Combustion IC enables the sulfur and halogen content in combustible solids, liquids, and gases to be determined by combining combustion digestion (pyrolysis) with subsequent ion chromatography. Combustion IC can detect of individual halides without the interference that is encountered in any of the competing detection methods for ASTM D4929

Organic Chlorides by ASTM D4929

Organic chlorides in crude oil are known to cause severe corrosion in crude tower overhead systems, therefore, most refineries allow no more than 1 ppm (mg/L) organic chlorides in the crude charge. There are two alternative test methods for determination of organic chloride in washed naphtha fraction; sodium biphenyl reduction measured with potentiometry or combustion and evaluation by microcoulometry. Metrohm Combustion Ion Chromatography can be used instead of microcoulometry for this measurement.

Water Content by ASTM D4377 & D4928

The determination of the amount of water in crude oil and petroleum products has always been important. Karl Fischer (KF) titration is the best water determination method due to its excellent reproducibility and accuracy as well as its ease of use. For these reasons, KF is called out in numerous international standards. Water is not homogeneously distributed in these products, which means that the petroleum samples must be homogenized before analysis. Furthermore, crude and heavy oils contain tars that can contaminate electrodes and titration cells leading to frequent reagent exchange and titration cell cleaning. These additional steps add time and complexity to these measurements. To ensure that the sample completely dissolves, solubility promoters are added to the methanol.

Metrohm offers both volumetric and coulometric KF titrators for moisture determination in crude oil samples.