The size distribution of sulfur,
vanadium, and nickel was determined
for four crude oils and their distillation cuts using gel permeation
chromatography (GPC) coupled to inductively coupled plasma high-resolution
mass spectrometry (ICP HR MS). The results show a trimodal distribution
of vanadium and nickel compounds in the crude oils, the atmospheric
residues, and the vacuum residues and, for sulfur compounds, either
a mono- or bimodal distribution depending upon the distillation cut
considered. A correlation exists between the sulfur fraction retention
times and the temperature cuts of the distillation for a temperature
below 560 °C and also between the viscosity of the crude oils
and the proportion of trapped sulfur compounds in a higher boiling
temperature fraction. The thermic treatment applied for the distillation
increases the aggregation of low- and medium-molecular-weight compounds
of vanadium and nickel into higher molecular weight aggregates between
the crude oil on the one hand and the atmospheric residue and vacuum
residue on the other hand, especially when the crude oil has a high
total sulfur content.
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