engleski

Concentration dependence of asphaltene aggregation monitored by DOSY NMR

Asphaltenes are the heaviest, most polar and least reactive molecules in crude oil, primarily consisting of carbons and hydrogens, some heteroatoms, such as sulfur, nitrogen, oxygen and traces of transition metals. They may aggregate during the downstream and upstream processes and cause many problems in production, refining and transportation. Asphaltene aggregation highly depends on the chemical nature of the crude oil, temperature and pressure. In this research, concentration dependent diffusion measurements were carried out to determine the lowest aggregation concentration of Middle Eastern asphaltenes and to study how the addition of V(IV), Fe(III) and Ni(II) affects the aggregation process. Asphaltene components were separated by DOSY NMR technique according to their diffusion properties. The influence of T1 relaxation on average diffusion coefficients was investigated by inversion recovery experiments. Changes in diffusion coefficients reflected the formation of different asphaltene types. It is expected that the presented results could throw more light into the asphaltene aggregation mechanism.

asphaltene aggregation ; diffusion coefficients ; DOSY NMR spectroscopy

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