Asphaltene fractionation based on adsorption onto calcium carbonate: Part 1. Characterization of sub-fractions and QCM-D measurements

• New procedure developed to fractionate asphaltenes.
• Asphaltene sub-fractions differ in amount of carbonyl, carboxylic acid or derivative groups present in them.
• Higher adsorption on stainless steel observed for sub-fractions with more carbonyl, carboxylic acid or derivative groups.
• Interaction between sub-fractions limits adsorption of unfractionated asphaltenes.

A new fractionation procedure was developed based on adsorption of asphaltenes onto calcium carbonate. The fractions obtained were characterized by elemental analysis, Fourier Transform Infrared Spectroscopy (FTIR) and Quartz Crystal Microbalance with Dissipation (QCM-D). FTIR analysis indicated that the sub-fractions obtained differed in the amount of carbonyl, carboxylic acid or derivative groups present in them. The adsorption of these fractions on stainless steel was studied by QCM-D. While the unfractionated asphaltenes exhibited a maximum saturation adsorption (Γmax) of 3.4 mg/m2, the sub-fractions did not however show a Γmax within the concentration range tested (0.01–1.5 g/l). The asphaltene fraction with highest concentration of carbonyl, carboxylic acid or derivative groups formed visco-elastic layers on stainless steel and also exhibited maximum adsorption (around 8 mg/m2). Finally, results obtained from QCM-D measurement suggest that the interaction of the asphaltene sub-fractions tend to prevent an adsorption of unfractionated asphaltenes onto stainless steel.

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