SEDIMENT FORMATION DURING HEAVY OIL UPGRADING

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Abstract
A soft coke-like substance often forms In the liquid product of visbreaking and hydrocracking processes for upgrading vacuum residue of heavy crude oil. This material usually limits the severity, or conversion of the process because it accumulates in downstream equipment. Although the amount of such material produced depends on the crude oil, it has not been possible before to correlate its production rate to chemical characteristics of the vacuum residue in a quantitative manner. In this 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: the degree of condensed polynuclear aromaticity, the average number of alkyl-groups substituting the polynuclear aromatics, the ratio of heptane insolubles to pentane insoluble-heptane solubles, and the H/C ratio of the latter fraction. The correlation coefficient is 0.95