Oxidation behavior and kinetics of Iranian crude oil samples using thermal analysis (TA)

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ABSTRACT In-situ combustion is a thermal enhanced recovery method which has been considered by many researches in recent years. In this study, six samples of Iranian crude oil were selected to investigate crude oil oxidation in in-situ combustion. To study crude oil oxidation, thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) were performed on the crude oils at heating rates of 1°C/min up to 800 °C in air atmosphere. Then, based on the experimental results, crude oils oxidation mechanisms for each sample were evaluated to know better about reactions that happen in oxidation process. Investigation of TG, DSC and Differential Thermogravimetric (DTG) curves, indicated that oxidation process can be divided into three main reaction regions, low-temperature oxidation (LTO) (<400°C), (middle temperature oxidation (MTO) (370–477°C) and high temperature oxidation (HTO) (480–660°C). On the basis of DTG peaks, the starting point of reaction for each region was determined. Then, for each region, Coats-Redfern analysis was used to calculate kinetic parameters. It observed that the heaviest crude oil sample has higher values of activation energy than other samples. Calculated enthalpy values for HTO intervals showed that, the heaviest crude oil sample has higher enthalpy compared to lighter samples, and the minimum value of enthalpy was for the lightest sample.