FORMATION DURING HEAVY OIL UPGRADING

A soft coke-like substance often forms in the liquid product of visbre aking and hydrocracking processes for upgrading vacuum residue of heav y crude oil. This material usually limits the severity, or conversion of the process because it accumulates in downstream equipment. Althoug h the amount of such material produced depends on the crude oil, it ha s not been possible before to correlate its production rate to chemica l characteristics of the vacuum residue in a quantitative manner. In t his work we show that the amount of sediment produced per unit weight of vacuum residue feed in laboratory hydrotreating experiments can be correlated with four chemical characteristic of the vacuum residue: th e degree of condensed polynuclear aromaticity, the polynuclear aromati cs, the ratio of heptane insolubles to pentane insoluble-heptane solub les, and the H/C ratio of the latter fraction. The correlation coeffic ient is 0.95.