Kinetics and mechanism of the macromolecular part of crude oil

A phase-separation kinetic model for coke formation

“…However, kinetic models that contain such sequences of direct chemical reaction to coke fail to predict the induction period before coke formation begins. This induction period has been observed experimentally by many previous investigators (Levinter et al, 1966(Levinter et al, ,1967Magaril and Akseneva, 1968;Valyavin et al, 1979;Takatsuka et al, 1989a) as well as making visbreaking and the Eureka processes possible. Magaril et al (1968Magaril et al ( , 1970Magaril et al ( ,1971 were the first to postulate that coke formation is triggered by the phase separation of asphaltenes.…”

Molar Kinetics and Selectivity in Cracking of Athabasca Asphaltenes

“…The coke yield showed a 10 min induction time and then increased sharply. Such an induction period for coke formation has been reported by many workers. ,− At lower reaction temperatures, below 400 °C, the formation of coke was much less significant. For example, at 370 °C the liquid yield was 98% after 1 h of reaction.…”

Inference of reaction kinetics for supercritical water heavy oil upgrading with a two‐phase stirred reactor model

“…Ample evidence for the dominance of such reactions in the thermolytic upgrading process can be found in experimental studies of both model hydrocarbon compounds 16 and crude oil fractions 12 Initial accumulation of the highly aromatic asphaltene cores in the oil phase , stabilized in solution by the heavy maltenic fractions and prevented from forming higher molecular weight asphaltene cores by hydrogen donation from the heavy maltenic species which inhibits the combination reaction pathways. Phase separation of asphaltene cores triggered once the concentration of AS + in the oil phase exceeds a specific solubility limit, followed by rapid molecular weight growth of the asphaltene cores in the new phase lean in hydrogen donating and dispersing heavy maltenic solvent molecules, resulting in the formation of solid coke precipitated in the reactor , as illustrated in Figure 3. Owing to the above features, the Wiehe LR kinetics model 14,15 is able to capture important characteristics of the batch reactor experimental data for VR and heavy oil thermolysis like: (i) the coke induction period (wherein no solid coke precipitation is observed in the reactor until a specific reaction time instant) observed in both, Wiehe's extensive experimental work 14,15 as also in other earlier experimental studies reported in the literature, 17–24 and (ii) the maximum in asphaltene concentration in the reactor at the onset of coke formation. In fact, the hypothesis of coke formation triggered by phase separation was first postulated by Magaril et al 19,25,26 and was employed in earlier LR kinetic models for VR hydroconversion by Sosnowski et al 27 and Takatsuka et al 28 A detailed discussion of the important chemical pathways and characteristic features of the thermolysis of heavy oils and VR is taken up in Section 2 of Appendix S1.…”