Impact of Iron Tallate on the Kinetic Behavior of the Oxidation Process of Heavy Oils

Abstract

Copyright © 2019 American Chemical Society. 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 iron-containing 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.