No abstract

Atmospheric residues from four representative crude oils were subjected to thermal cracking kerosene and gas oil, were obtained in yields up to 15-25wt% on the feed. Significant changes in the physicochemical properties of the cracked residue such as the lowering of pour point, viscosity and average molecular weight were observed.

Atmospheric residue from Iranian Heavy crude was subjected to thermal cracking at 420-The presence of hydrogen or tetralin suppressed the yields of distillates at low cracking temperature but enhanced them at high temperature. However, the effect of diluents was not so pronounced as in the case of Arabian Heavy. The feed and the product residues were separated into six fractions which were analyzed according to Speight's method. Visbreaking reaction was inferred to be initiated by unimolecular decomposition of "polymeric aromatics" producing fairly large amounts of distillates, followed by scission of alkyl side-chains in the aromatics, concurrent with polymerization and/or condensation of the aromatics. The last undesirable reactions leading to coke formation seem to be less significant provided as large amount of naphthenes is present as in the Iranian Heavy atmospheric residue.