Experimental and theoretical study of the influence of solvent on asphaltene-aggregates thermo-oxidation through high-pressure thermogravimetric analysis

Abstract

This study is focused on the understanding of n-C7 asphaltene-aggregates oxidative behavior under high-pressure conditions. For this aim, different asphaltene model solutions were prepared using three asphaltene concentrations (0.1, 1.0, and 10 wt%) on three xylene isomers. The experimental results revealed that the asphaltene aggregate size increase in the order o-xylene < m-xylene < p-xylene. Also, molecular dynamics (MD) simulations were carried out to explain the aggregation differences. It was found that the –CH3 location in the xylene has a substantial impact on the aggregation state. The o-xylene molecules surrounding the asphaltene aggregates oriented them –CH3 groups towards the aggregates, increasing their interaction energy and reducing the aggregation size. Further, the oxidative experiments of the aggregates showed that the oxygen chemisorption decreased as the asphaltene aggregate size increased, reducing their reactivity. Contrasting the xylene isomers, for concentrations >1.0 wt%, the mass gained by oxygen chemisorption increased in the order: p-xylene < m-xylene < o-xylene. This study improves our understanding of the relationship between the aggregation and thermal oxidation of crude oils, characterizing the physical behavior to propose alternatives that reduce asphaltene aggregation and improve the oxidative kinetic.