Catalysts used in the hydrogenation processes of heavy feedstocks deactivate due to coke deposition. Although the mechanism for coke formation is not fully understood, condensation reactions of polycyclic aromatic compounds present in the feeds are a key aspect. The effect of coke deposition on catalyst performance is typically modelled using accelerated aging agents comprising model coke precursors. Mixtures employed in such studies include polycyclic aromatic compounds such as anthracene as a coke precursor, and long chain alkanes such as hexadecane as a diluent. It is shown in this thesis that binary and pseudo binary mixtures of polynuclear aromatic compounds and n-alkanes present TYPE II, TYPE IV, or TYPE III phase behaviour according to the van Konynenburg and Scott (1980) phase projection classification. Incubation periods and the apparent autocatalytic effects associated with batch coke deposition experiments in such systems are explained through a combination of high temperature phase equilibrium experiments and computations with the model systems anthracene + n-alkane + hydrogen, pyrene + n-alkane + hydrogen, and hexaphene + n-alkane.
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