Toward Separation and Characterization of Asphaltene Acid and Base Fractions

Abstract

Chemical inhibition of asphaltene deposition is considered a cost-effective way to prevent the harsh consequences of asphaltene instability in the produced crude. Thus, a careful screening of asphaltene inhibitors is crucial for an efficient prevention. However, the characteristics of asphaltenes such as their acid-base properties will influence the selection of an asphaltene inhibitor and the inhibition mechanism. Therefore, improved knowledge on asphaltene acidic and basic fractions is important. In this work, the separation of asphaltenes into acid, base, neutral, and amphoteric fractions was performed. Among the existing techniques to fractionate asphaltenes, the method of Ramljack was adopted and applied on a light oil extracted asphaltene. However, this oil was sampled from one of the wells in the Hassi Messaoud field in Algeria that experienced a recurring deposition of asphaltenes. The results of asphaltene fractionation reveal that the half composition of this heavy part of crude oil is active functions gathered acid and base components. However, the main contribution is reported to the neutral fraction. The characterization results of infrared and elementary analyses show that both active fractions are aromatic and polar. Moreover, the acid fraction contains in its structure carboxylic acids, phenols, sulfoxide groups, and aliphatic chains, while the structure of the base fraction contains amines, sulfoxide groups, and aliphatic chains.