Impact of Functional Group Methylation on the Disaggregation Trend of Asphaltene: A Combined Experimental and Theoretical Study

Asphaltenes have a tendency toward aggregation, leading to a series of problems (e.g., coking) in the field of refining or other oil utilization and making the development of a disaggregation method an urgent need. We employed functional group methylation experiments combined with molecular dynamics simulations and quantum chemical calculations to reveal the disaggregation mechanism of asphaltenes based on the chemical alteration method. Here, the experimental results show that the intersheet distances in the asphaltene aggregate increase after the methylation reaction, and the asphaltene molecules are not prone to reaggregation after methylation, which was demonstrated by an increase in the critical aggregation concentration in toluene. These disaggregation effects can be explained by the theoretical study results; that is, they can be attributed to the reduction of the electrostatic interaction, which is derived from the disappearance of the hydrogen bonds after methylation. However, a thorough disaggregation cannot be achieved only by methylation because the van der Waals force is always the dominant force in both raw and methylated asphaltenes, outweighing the electrostatic force. Asphaltene molecules with very short side chains containing more than one terminal polar group could obtain a better disaggregation effect by the methylation reaction, whereas those with long chains could not. Our results provide the underlying insights for the proposal of an effective method for asphaltene disaggregation to prevent coking.