ASPHALTENES (HEPTANE INSOLUBLES) IN CRUDE PETROLEUM AND PRODUCTS: ASTM D6560
EXPLANATION
Asphaltenes in crude oils may give problems during storage and handling if the suspension of asphaltene molecules is disturbed through excess stress or incompatibility. They are also the last molecules in a product to combust completely, and thus may be one indicator of black smoke propensity. Their composition normally includes a disproportionately high quantity of the sulfur, nitrogen, and metals present in the crude petroleum or petroleum product.
This test method gives a procedure for the determination of the heptane insoluble asphaltene content of gas oil, diesel fuel, residual fuel oils, lubricating oil, bitumen, and crude petroleum that has been topped to an oil temperature of 260° C. Oils containing additives may give erroneous results.
TEST SUMMARY
A portion of the sample is mixed with heptane and the mixture heated under reflux, and the precipitated asphaltenes, waxy substances, and inorganic material are collected on a filter paper. The waxy substances are removed by washing with hot heptane in an extractor.
After removal of the waxy substances, the asphaltenes are separated from the inorganic material by dissolution in hot toluene, the extraction solvent is evaporated, and the asphaltenes weighed.
TEST PRECISION
Repeatability: 0.1 A
Reproducibility: 0.2 A
Where A is the average result in % m/m.
No bias can be assigned since the heptane insoluble asphaltenes are defined by this test method.
