American Chemical Society
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Disaggregation of Asphaltene Aggregates in Solutions Depending upon Affinity Indices of the Hansen Solubility Parameter Using Ultrasmall‑, Small‑, and Wide-Angle X‑ray Scattering

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journal contribution
posted on 2022-08-18, 20:20 authored by Takeshi Morita, Masato Morimoto, Satoshi Shibuta, Hiroshi Imamura, Hideki Yamamoto, Rik R. Tykwinski, David E. Scott, Jeffrey M. Stryker, Teruo Suzuki, Ryuzo Tanaka
Disaggregation of asphaltene aggregate in solution is investigated using ultrasmall-, small-, and wide-angle scattering of X-rays up to 300 °C under isobaric conditions. Wide-angle scattering profiles indicate that the longer range structure of asphaltene aggregates in toluene collapses around 150 °C. A further increase in the temperature to 300 °C, however, leads to a slight reversion to the aggregated state. This specific behavior in solution is discussed in terms of the transition of asphaltene from a solid to a melted state around 200 °C and the corresponding change in affinity indices of the Hansen solubility parameter (HSP) at elevated temperatures. Ultrasmall- and small-angle scattering profiles of samples in solution clearly show the correlation of asphaltene aggregation with the HSP indices. To understand a deeper insight into key aspects of asphaltene aggregation behavior, small-angle scattering of model compounds in toluene is measured. The scattering intensities of model compounds are classified into two groups: suggesting and confirming molecular structures contributing to enhanced aggregation and heteroaromatics containing sulfur, peri-condensed aromatic rings, and porphyrin.