Combustion behavior of aromatics and their interaction with n-alkane in in-situ combustion enhanced oil recovery process: Thermochemistry

[Display omitted] •Tetracosane (C24) shows only LTO, p-quaterphenyl and thioxanthone show only HTO.•Pyrene shows a unique continuous middle-high temperature oxidation (M-HTO).•p-Quaterphenyl and thioxanthone don’t shift C24’s LTO but reduce its heat release.•C24 shifts the HTO of p-quaterphenyl and thioxanthone by strong interaction.•Strong interaction between C24 and pyrene induces a new explosive oxidation. The combustion behavior of aromatics (p-quaterphenyl, thioxanthone, pyrene) and their interaction with n-alkane (tetracosane) were investigated by high-pressure differential scanning calorimetry (HP-DSC). Tetracosane only showed low-temperature oxidation (LTO), while p-quaterphenyl and thioxanthone only showed high-temperature oxidation (HTO). Pyrene exhibited a unique middle-high temperature oxidation (M-HTO). Tetracosane significantly promoted the HTO of p-quaterphenyl and thioxanthone, and shifted their HTO into lower temperatures. While p-quaterphenyl and thioxanthone did not significantly affect the occurrence of the LTO of tetracosane, but they did reduce the heat release and reaction rate of the LTO of tetracosane. The co-oxidation of tetracosane and pyrene triggered an intense interaction that exerts a strong inhibition on the LTO of tetracosane, and induces an explosive oxidation reaction followed by a mild oxidation from 280 to 325 °C. The intense interaction also significantly promoted the HTO of the pyrene. In general, the interaction strength is in turn pyrene + tetracosane > thioxanthone + tetracosane > p-quaterphenyl + tetracosane. Due to the strong interaction between the alkane and aromatics during their co-oxidation, the additivity of heat release in both LTO and HTO cannot be applied in terms of reaction process as well as total heat release.