Mn-catalyzed oxidation of the Ashalcha heavy oil in porous media was examined. We used manganese(III) tris(acetylacetonate) as a convinient oil-soluble precatalyst that decomposes to catalytically active species during the temperature ramping. Reaction kinetics in the heavy oil oxidation with air indicated that the presence of the manganese ions changes the mechanism of the oxidation process, especially in the high-temperature region. To study precatalyst transformations in detail, we suggested the approach of combining X-ray powder diffraction (XRPD), thermal analysis, non-isothermal kinetic methods, and electron paramagnetic resonance (EPR). A comprehensive study of the decomposition of pure manganese(III) tris(acetylacetonate) and the subsequent comparison of its behavior to that in porous media in the presence of the oil allows us to shed light on some aspects of the mechanism of catalytic oxidation.
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.
There is still considerable controversy surrounding the mechanisms, thermodynamics, and kinetics of heavy oil aquathermolysis and pyrolysis processes. The present paper aims to widen our knowledge about the effect of iron tallates on pyrolysis and aquathermolysis of Cuban heavy oil. The obtained SARA (S: saturates, A: aromatics, R: resins, A: asphaltenes) analysis has shown a significant increase in light hydrocarbon content during aquathermolysis. Moreover, the elemental analysis has indicated an increase in C and H content by almost 4% and 6%, respectively, with a significant decrease in S and O content by up to 23% in the presence of iron tallates. These results have been further confirmed by infrared spectrometry. The obtained IR data indicated that asphaltene and resin compounds transform into light hydrocarbons after aquathermolysis. On another hand, the activation energy of heavy oil pyrolysis decreased in the presence of the utilized catalyst; meanwhile, the reaction rate increased, especially in the temperature range of 200–480 °C, which may validate a significant effect of the used catalyst in real conditions. Moreover, the obtained thermodynamic data showed a decrease in the enthalpy and entropy of activation of oil pyrolysis in the presence of iron tallates. Our results are encouraging in terms of energy consumption, optimization, and process control and should be validated by a larger sample size.
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.
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