F-33 Concept Study to Confirm Thermolysis-induced Asphaltene Precipitation Hypothesis
This initial study experimentally confirmed that asphaltenes can chemically transform at elevated temperatures (asphaltene thermolysis) and precipitate. A single sample of crude oil 23 was subjected to batch heating at 350 °C for six hours, allowing uniform thermal exposure. Asphaltenes were fractionated into four solubility-defined groups using n-pentane, n-hexane, n-heptane, and n-octane. CHNS elemental analyses were performed on the pentane-insoluble (C5+) and octane-insoluble (C8+) fractions, both before and after heating, as well as on solids generated during the process. Post-heating results showed a notable change in the relative amounts of carbon and hydrogen and a significant rise in the undetermined (non-CHNS) amount. These chemical shifts suggest that, in addition to thermal degradation, oxidation or corrosion phenomena may be contributing to chemical changes in the oil system. Time-dependent behavior was investigated with two tests carried out with durations of two and three hours. These tests substantiated the progressive nature of solid formation and compositional changes in the oil, reinforcing the hypothesis of thermally driven transformations. Furthermore, the results indicate that the concept of residence time distribution is important in assessing fouling potential. The implications of these results will be evaluated in further development of a fouling model and test protocols.