A study on asphaltene adsorption onto two mineral adsorbents in the presence and absence of anionic and ionic inhibitors

Abstract

ABSTRACT Asphaltenes pose several problems in petroleum industry. Therefore, finding new reliable methods and materials to address this issue is of vital importance. In this study, asphaltene adsorption onto two mineral adsorbents, lightweight expanded clay aggregates (LECA) and Perlite, in the presence and the absence of two different inhibitors (Dodecilebenzenesulfonic acid or DBSA and coconutdiethanolamide or CDEA) was studied. The results were fitted to three different adsorption isotherms to understand the nature of the adsorptions. Overall, in the absence of inhibitors, Perlite adsorbed more asphaltenes, while the asphaltene adsorption per surface area for LECA was greater than that of Perlite. However, in low asphaltene concentrations, the adsorption is independent of the adsorbent type, as the adsorption behavior of the adsorbents starts to differ in higher asphaltene concentrations. The adsorption data were not fitted to the Henry’s isotherm, while they were successfully fitted to the Freundlich and the Langmuir isotherms. It was concluded that the adsorption process onto both adsorbents were heterogeneous and monolayer while the process for Perlite was more heterogeneous. Given the satisfactory adsorption isotherm parameters for both LECA and Perlite, it is concluded that both LECA and Perlite are good asphaltene adsorbents. Moreover, it was shown that increasing the inhibitor to asphaltene ratio not always causes a reduction in asphaltene adsorption. In fact, there is an optimum ratio (2:1) for both inhibitors where the least asphatene is adsorbed. In both cases of the adsorbents, DBSA had a better performance in lowering the adsorption of asphaltene on the surface of the adsorbents.