The phase behavior of heavy oils at high temperature and the reactive formation of formation of mesophase in heavy oil is a complex phenomenon which has been studied by many different methods including polarized microscopy [1], X-ray diffraction [2], transmission electron microscopy [3], and high-temperature ~1H-nuclear magnetic resonance spectroscopy [4]. Mesophase is important in the formation of coke during thermal cracking, and in fouling reactor internals and catalyst particles during hydroconversion. The prior studies indicated the presence of multiple bulk phases over a range of temperatures. Unlike the coal-derived liquids that have dominated the published work on mesophase [2-4], the vacuum residue and asphaltene fractions of petroleum are much richer in aliphatic carbon and much more susceptible to addition reactions [5,6]. High temperature reactions add to the complexity of the mixture, and can prevent reversible phase behavior.
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