Peri-condensed asphaltenes

Asphaltenes can exist in various structural forms such as peri-condensed and kati-condensed rings. Upon heating, peri-condensed asphaltenes in crude oil have been shown to rearrange into kati-condensed asphaltenes. 

The stability of the products from coal-derived syncrudes must be examined carefully. Many unique compounds are present in these syncrudes peri-condensed aromatics and naphthenes, oxygen compounds, and asphaltene-like hydrocabons. Traces of these compounds may remain in the hydrotreated product and their effect on jet, thermal, and oxidation stabilities cannot be predicted from the behavior of petroleum products. 

The value of ring condensation index (3), ring compactness (7), and the extent of condensation of unsubstituted aromatic clusters (4) all indicate a skeleton of a peri-condensed system in the aromatic portion of this asphaltene. 

The aromatic ring systems within petroleum-derived asphaltene are much more condensed (Haru/Car = 0.3-0.5, which is peri) than those of coal-derived asphaltene (Haru/Car = 0.5-0.7, which is kata). 

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