This research is intended to reveal the difference and connection of oxidation behavior between crude oil and its SARA fractions. Thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques were used to characterize oxidation behavior. The results showed that the oxidation behavior of individual SARA components exhibited an obvious difference. Saturates showed a weak high-temperature oxidation (HTO) region. Asphaltenes generated more heat in HTO than in the low-temperature oxidation (LTO) region. Aromatics showed intense exothermic activity in both LTO and HTO regions. Heat release and mass loss showed a good correspondence in the HTO region for all SARA fractions, which means heat release and mass loss were caused by the same reaction mechanism that is believed to be the coke combustion as it is the only significant reaction in the HTO region. However, the good correspondence did not exist in the LTO interval where the reactions are more complicated and a multiple-step mechanism should be considered. In addition, it is not quite reasonable to determine the reactivity of SARA fractions only by TG data as little mass loss does not mean reactants are inactive. Kinetic parameters of LTO and HTO reactions were determined by Friedman and Ozawa–Flynn–Wall isoconversional methods. In general, for the crude oil and each fraction, the activation energies of HTO were higher than that of LTO. The additivity of DSC data could be applied quite well in the LTO region. However, the predicted curve seriously deviated from the actual situation after 350 °C, which implies the exothermic reaction process of individual components was influenced by the presence of other components. Nevertheless, the total heat release of the measured and predicted values was similar, which makes it possible to predict the heat effect of crude oil from individual SARA components.

Metal tallates are generating considerable interest as catalysts for thermally enhanced oil recovery. Meanwhile, in situ combustion is considered a promising thermally enhanced oil recovery method. It is still viewed as a complicated process as a result of its multiphasic, multicomponent, and multistep reactions occurring within it. In this study, we investigated the impact of Mn@Cu tallate on the heavy oil oxidation process to highlight its effect on stabilizing the combustion front using differential scanning calorimetry combined with an isoconversional principle for calculating the kinetic parameters of the process. The obtained data have showed that Mn@Cu tallate can play an important role in stabilizing the combustion front of in situ combustion, where it decreased the energy of activation of low-and high-temperature oxidation regions. As a result, the effective reaction rate constants in both regions increased as well.

Oxidation of heavy and extra-heavy oils is recognized as a complicated process due to the heterogeneous nature of its reaction medium and the lack of knowledge concerning its reaction mechanisms. The next decade is likely to witness a considerable rise in the use of in situ combustion to extract heavy and extra-heavy oils. However, a major issue of the in situ combustion is the instability of the combustion front. For this reason, application of catalysts was viewed as a way to initiate the process early and stabilize the resultant combustion front. In this study, we have synthesized an efficient precursor of ironcontaining catalyst, studied its effect on heavy-oil oxidation by estimating the heat-flow-rate changes occurring during the oxidation process as a function of heating at different rates using differential scanning calorimetry, and investigated its transformation throughout the oxidation process by estimating its mass loss with heating at the rate of 10 °C min −1 using thermogravimetric analysis. In addition, we studied the morphology and size of the final product of oxidation obtained at 500 °C using scanning electron microscopy. At the end of the study, we compared its effect to that of the previously studied manganese tallate on heavy-oil oxidation. The kinetic parameters of the processes have been obtained by means of applying Kissinger method (isoconversional principle). Interestingly, iron tallate has been found to decrease the activation energy of both low-temperature and high-temperature oxidation regions. In addition, the values of effective reaction rate constants of both regions (low-temperature oxidation and high-temperature oxidation) increased in the presence of iron tallate as well. Moreover, it has been suggested that the iron oxide nanoparticles formed in situ are responsible for the resulting catalytic effect.

A remarkable feature of heavy oil oxidation during the in situ combustion process is the difficulty in maintaining combustion front to flow throughout the reservoir. Recent developments suggest the use of catalysts regarding this issue. Previous works have been limited by the catalyst choice. Moreover, many research works have failed to provide a catalyst that meets the requirements of efficiency, low-cost, and positive impact on the surrounding. This paper presents new type of catalysts based on tallate, each combined with nickel and cobalt, respectively, as highly efficient catalysts for the oxidation of heavy oil. We have compared the effect of each catalyst using differential scanning calorimetry to highlight kinetic parameters of each process by the Kissinger method. In addition, we employed thermogravimetric analysis and scanning electron microscopy to investigate the behavior of catalysts during the process. The obtained results showed a similar high efficiency of both precatalysts by decreasing the activation energy of the high-temperature oxidation region, increasing the preexponential factors of both high- and low-temperature oxidation regions, and increasing their reaction rate constants. Moreover, the precatalysts used transformed in situ to nanoparticles during the heavy oil oxidation process.

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