Asphaltene Molecular Structure and Chemical Influences on the

Energy & Fuels 2006, 20, 1227-1234

1227

Asphaltene Molecular Structure and Chemical Influences on the Morphology of Coke Produced in Delayed Coking M. Siskin,* S. R. Kelemen, C. P. Eppig, L. D. Brown, and M. Afeworki ExxonMobil Research and Engineering Company, Corporate Strategic Research Laboratories, 1545 Route 22 East, Clinton Township, Annandale, New Jersey 08801 ReceiVed NoVember 22, 2005. ReVised Manuscript ReceiVed February 27, 2006

The average chemical structure of asphaltenes present in a vacuum resid feed is related to the morphology of the coke that is produced in a delayed coker (shot coke vs sponge coke). A combination of solid-state 13C NMR, X-ray photoelectron spectroscopy (XPS), and elemental abundance was used to characterize the average chemical structure of several n-heptane asphaltenes from shot-coke- and sponge-coke-producing vacuum resid feeds. The chemical structural properties of the asphaltenes are discussed in relation to the coke morphology produced from the parent resid. The average asphaltene aromatic carbon per cluster size is between 14 and 22 carbon atoms, which corresponds to three-to-five-ring average clusters. When the ratio of aromatic carbon to unreactive (i.e., heterocyclic aromatic) nitrogen and sulfur in asphaltenes is