Ni, V, and Porphyrinic V Distribution and Its Role in Aggregation of Asphaltenes.

Information on distribution of metals and metalloporphyrins can help to understand molecular interaction presented by metals and asphaltenes and possible participation of metals in aggregation of asphaltenes. Therefore, contents of metals and metalloporphyrins were determined in three asphaltene subfractions separated based on solubility. Compositions of the subfractions were confirmed by elemental analysis, vapor pressure osometry molecular weight, and1H NMR, and molecular structures were simulated. The correlation between distribution of metals and metalloporphyrins and molecular composition was discussed. It indicates that metals interacting loosely with asphaltenes tend to be preferentially extracted into lighter fractions and present as metalloporphyrins, while a great portion of metals concentrates into the heavier fraction and presents as metal-nonporphyrins apparently due to strong interaction with asphaltenes. This suggests that distribution of metals plays a key role in determining the polarity and solubility of subfractions, and thus affects aggregation of asphaltenes. [ABSTRACT FROM AUTHOR]