Molecular structure characterization of asphaltene in the presence of inhibitors with nanoemulsions

Molecular structure characteristics and morphological features of asphaltene can be significantly influenced by the addition of asphaltene inhibitors (AI). We have recently developed a novel concept of using nanoemulsions (NE) as carriers for controlled release of asphaltene inhibitors, which could prohibit the precipitation problem with reduced AI quantity. In this work, X-ray diffraction (XRD) was utilized to investigate the changes in the stacking behaviour of asphaltenes in the presence of three cases: (i) strong organic acids (dodecyl benzene sulfonic acid, DBSA), (ii) nanoemulsions (blank NEs), and (iii) nanoemulsion loaded DBSA (DBSA NEs). Based on the XRD and transmission electron microscopy (TEM) analyses, the stacking distance between aromatic rings of asphaltene was found to be increased by 22.2%, suggesting that the modification of the pi system over the aromatic zone prevented the ultimate pi-pi interactions between asphaltene sheets. The evidence of multiple intermolecular interactions quantitatively obtained from Fourier-transform infrared spectroscopy (FTIR) supported our proposed mechanism for controlled release effect and long-term asphaltene stability, i.e., the decrease of the aromaticity and the reduction in the aliphatic side chains of asphaltene. The refractory nature of asphaltenes was examined by thermogravimetric analysis (TGA), which showed that the asphaltene structure was improved considerably and the coke yield was decreased by 62% due to the decrease of the cluster size and the increase of the stacking distance.