J. Braz. Chem. Soc., Vol. 00, No. 00, 1-7, 2012
The Influence of Asphaltenes Subfractions on the
Stability of Crude oil Model Emulsions
Siller O. Honse, Claudia R. E. Mansur and
Elizabete F. Lucas*
Instituto de Macromoléculas, Universidade Federal do Rio de Janeiro,
Av. Horácio Macedo, 2030, Ilha do Fundão, 21941-598 Rio de Janeiro-RJ, Brazil
Abstract
Crude oil is produced as water-in-oil emulsion,
and asphaltenes have been considered the main responsible by their
stabilization. The aim of this work was to evaluate the influence of the
asphaltenes subfractions on the stability of petroleum model emulsions and on
the efficiency of demulsifiers. Model water-in-oil emulsions were prepared:
aqueous phase of brine and oil phase of asphaltenes in toluene. Different
asphaltenes fractions were used. The emulsions’ stability was assessed by the
bottle test, with and without adding demulsifier. The results show that a
sample of asphaltenes with broad polarity distribution promotes greater
emulsion stability than a sample with narrow distribution and intermediate
polarity. Besides this, the efficiency of demulsifiers in separating the
emulsions is directly related to the original stability of the emulsion.
Measurements of the interfacial tension revealed the efficiency of displacement
of the asphaltenes by the demulsifiers, which occurred more efficiently for the
emulsions containing asphaltenes fractions with narrow distribution and
intermediate polarity.
Introduction
Among the properties desired of demulsifiers are high adsorption speed at the
water-oil interface, displacement of the natural emulsifiers that stabilize the
emulsions and formation of thin and fragile films at the water-oil interface,
facilitating coalescence of the droplets.
The aim of this work was to study the influence of crude oil asphaltenes
subfractions, obtained and characterized previously, on the stability of
water-in-oil (W/O) emulsions. The measurements were performed by the bottle
test, with and without the addition of a demulsifier.
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