Structure–Reactivity Relationships for Petroleum Asphaltenes
2022
Gray, Murray R. | Chacón-Patiño, Martha L. | Rodgers, Ryan P.
The role of archipelago asphaltene structure in the reactions of petroleum asphaltenes was investigated by comparing yields of products from the conversion of archipelago-rich heavy oils and bitumen to the yields from a sample with predominant island-type structures. The archipelago content of the asphaltenes was positively correlated with the yield of liquid products boiling below 524 °C. The yield of coke solids increased with the fraction of island structures in the asphaltenes. Furthermore, catalytic hydroconversion of Athabasca bitumen gave a residual asphaltene fraction that was highly enriched in weakly aggregating components, on the basis of extrographic separation, and very low content of archipelago structures. High-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis showed that the heteroatom polydispersity of the asphaltenes after conversion was dramatically reduced, and the range of double-bond equivalents and carbon number was close to the limiting boundary of planar polynuclear aromatic hydrocarbons (PAHs). The radical cations from the converted asphaltenes showed significant concentration of high-ring-number/known PAH structures. The results highlight the existence of a positive correlation between the amount of archipelago structural motifs in asphaltenes and the yield of products with a range of boiling points below 524 °C. Moreover, the data demonstrates that advanced hydroconversion methods can be used to obtain asphaltene fractions with decreased polydispersity in terms of heteroatom content, alkyl-substitution, and molecular structure, which could be eventually exploited for material science applications.
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