Insights into the Self-Aggregation of Porphyrins and Their Influence on Asphaltene Aggregation

Despite the studies on asphaltene aggregation throughout few decades, the formation of asphaltene aggregates and subsequent deposition are still the biggest challenges in the oil industry. Especially, the role of porphyrins existing in oil naturally on asphaltene aggregation is not completely understood due to asphaltene's and porphyrin's special structures. Herein, we investigated the influence of tetraphenylporphyrin (TPP), nickel tetraphenylporphyrin (NiTPP), and vanadium tetraphenylporphyrin (VOTPP) on asphaltene aggregation by a multiscale approach, which provides an in-depth understanding of the role of porphyrins on asphaltene aggregation. UV-vis spectroscopy and fluorescence spectroscopy were performed to examine the self-aggregation of TPP, NiTPP, and VOTPP and the influence of porphyrins on the aggregation of asphaltene. The changes of stacking structures, microscopic structures, and particle size distributions of co-aggregates of asphaltenes with porphyrins were analyzed in detail via X-ray diffraction, inverted fluorescence microscopy, and granulometric distribution, respectively. The characterization results indicated that the aggregation ability of the porphyrins (TPP, NiTPP, and VOTPP) was stronger than that of asphaltene and porphyrins can promote the aggregation of asphaltene, which leads to the increase of the average aromatic sheet number, aggregation morphology, and particle size of asphaltene aggregates. Based on experimental analysis, the possible mechanism by which porphyrins promoted asphaltene aggregation was elucidated. This research provided new insights into the aggregation and disaggregation of asphaltenes.