Effect of Ligand Structure on the Kinetics of Heavy Oil Oxidation: Toward Biobased Oil-Soluble Catalytic Systems for Enhanced Oil Recovery

In recent years, protection of the environment from activities associated with enhanced oil recovery has been considered a crucial priority for decision-makers in the international community. The in situ combustion process as a promising thermal enhanced oil recovery method has been attracting considerable interest in terms of improving oil production and environmental protection. However, this technique is not yet well studied. This paper outlines a new approach to improve the process of heavy oil oxidation by designing new biobased oil-soluble catalysts that are able to maintain and stabilize the combustion flame front of the in situ combustion process. A comprehensive theoretical and experimental study including thermal analysis (thermogravimetry/differential scanning calorimetry, TG/DSC) and quantum calculations was used to shed light on the effect of the ligand structure in the oil-soluble catalytic system on the heavy oil oxidation process. The obtained accurate results proved that metal interaction with the designed ligands increased, which led to a decrease in the energy of activation and an increase in the heavy oil oxidation reaction rate. Besides, the obtained DSC curves showed one peak in the presence of Cu and biobased ligands, contrary to the curves obtained for heavy oil oxidation reported with other ligands and metals. In other words, the obtained catalysts merged low-temperature- and high-temperature oxidation regions into one region. These findings reveal that the structure of ligands can significantly affect their interaction with metals in oil-soluble catalysts, and therefore the efficiency of catalysts is dramatically improved. We believe that our work could be usefully employed for further studies to clarify the mechanism of the in situ combustion behavior of heavy oil for a better impact on the environment.