engleski

CRUDE OIL AND THEIR PRODUCTS CHARACTERIZATION BY SEC

Oil and oil fractions are complex mixtures containing normal, branched and cyclic alkanes, alkenes, aromatics, asphaltenes and polars component in wide molecular mass ( MM ) range ( 100-10000 Da ). MM is one of the basic and bulk properties of oil and oil fractions and is indicative for molecular size and structure. Generally, there are three methods that are widely used to measure MM. These are cryoscopy, the vapour pressure method and size-exclusion chromatography ( SEC ) method. SEC has long been used as a method for polymeric MM distribution ( MMD ) determination but SEC characterization is also used in oil and petrochemical field especially at heavy fractions and asphaltenic component. MMD is quite often correlated to boiling point distribution. For polymer SEC application polystyrene standards are used for calibration but due to structural differences they are not applicable to oil and oil fractions characterization. It was determined that considering hydrocarbon molecules consisting mainly of alkyl chain, aromatic rings and combination of both it is possible to construct specific calibrations based on n-alkanes, polyaromatics and alkyl benzenes. Taking into account a group type determination obtained by analytical NPHPLC a corresponding calibration a more real results can be suggested. A different oil sample and oil fractions were characterised by SEC and NPHPLC and results obtained by different calibrations were correlated. An original SEC chromatograms were used for „ fingerprints“ comparison for different sort of oils.

crude oil characterization; MM of crude oil; SEC of crude oil

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