Chemical and structural changes of resins during the catalytic and non-catalytic aquathermolysis of heavy crude oils

Resins are important molecules for colloidal system (maintaining asphaltenes dispersed) of heavy oils and are responsible of their high viscosity (together with asphaltenes). The results of characterization of resins before and after aquathermolysis by molecular weight, elemental analysis, Fourier transform infrared, nuclear magnetic resonance, and ultraviolet fluorescence were collected and analyzed to highlight the changes in chemical and structural properties. The discussion is based on the transformations that resin molecules undergo via hydrogenation, deoxygenation, desulfurization, cracking, ring opening, dealkylation and pyrolysis reactions at steam injection conditions. Some correlations were developed between properties of resins. It was found that the type of ligand plays an important role for catalytic aquathermolysis besides the type of active metal since a synergic effect of these factors produces diverse results in the properties of resins. The molecular weight of resins is greater improved using oil-soluble catalysts compared with water-soluble catalysts and non-catalytic aquathermolysis. Mo-based catalysts usually exhibit higher hydrogenation capability and sulfur removal than other active metals, while Fe-based catalysts commonly improves dealkylation and pyrolysis of side chain reactions of resins.