| Summary: | The gradual decline in conventional oil production combined with an increasing world energy demand has made the production and upgrading of heavy and extra heavy oil feedstocks crucial for the future of the global energy market. Properties of heavy oil such as high viscosity and high specific gravity as well as the high percentage of asphaltenes, heteroatoms and metals cause severe problems during extraction and refining processes. As a result, traditional upgrading technologies are not suitable as a standalone method to process these feedstocks. This makes necessary the development of alternative or complementary technologies to process heavy oil feedstocks in a more efficient and environmentally friendly way. This work is aimed to study an alternative heavy oil upgrading process that takes advantage of the unique properties of water at near-critical and supercritical conditions as reaction medium to perform the oxidative cracking of heavy oil feedstocks. The process consists of three main stages including the partial oxidation, cracking of the molecule, and removal of part of the oxygen incorporated from the final product. The process was studied using phenanthrene and methyl naphthalene as heavy oil model compounds and also Maya oil vacuum residue as real feedstock. This was performed in a purposely built microbomb batch reactor and an oxidative cracking flow reactor. The effect of the main process variables and the potential reaction pathways were studied with model compounds. Then the process was tested with real feedstock and the inclusion of a zeolite based catalyst to enhance yields to light oil was considered. It was found that process conditions have an important influence in the yield and selectivity to different product fractions. Optimum conditions to maximize the production of organic soluble products were determined. It was observed that polycyclic aromatic hydrocarbons were not reactive in the absence or at low concentration of reactive oxygen species. However, oxygenated intermediates continued to react in water alone. In addition, it was observed that intermediate products were mainly oxygenated compounds and that the oxygenation proceeded preferentially through central rings. A hydrogen rich gas product was obtained. Experiments with vacuum residue showed that high yields to liquid products with low boiling point are obtained keeping low yields to coke at most conditions studied. The addition of a zeolite based catalyst showed improvement in the process, increasing the yield to light oil and reducing the average molecular weight of the product. Heteroatoms and metals present were mainly removed as coke and showed to be relatively stable.
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