Oxidation of <i>n</i>‑Alkane (<i>n</i>‑C₈H₁₈) under Reservoir Conditions in Response to Gas Mixture Injection (CO₂/O₂): Understanding Oxygenated Compound Distribution

CO₂ geosequestration [carbon capture and storage (CCS)] and enhanced oil recovery (EOR) by CO₂ injection in hydrocarbon-depleted reservoirs could limit the CO₂ atmospheric accumulation. In the case of CO₂ capture by oxy-combustion, the main annex gas associated with CO₂ is O₂. O₂ that remains in the flue gas for injection can induce the oxidation of the hydrocarbons contained in the reservoirs. The effect of O₂ must be studied in terms of benefit and/or risk for CCS or EOR. To investigate the mechanism of hydrocarbon oxidation, it is essential to analyze the distributions of the formed oxygenated compounds. That is why experiments have been performed with a model compound (<i>n</i>-octane) in a closed reactor under high pressure at different temperatures and with different oxygen concentrations. The product distribution suggests two pathways of <i>n</i>-alkane oxidation, with (i) the preservation of the aliphatic chain length of the initial <i>n</i>-alkane, which generates oxygenated products with the same number of carbon, and (ii) the breakdown processes of the initial <i>n</i>-alkane, which generates low-molecular-weight oxygenated products. The new understanding of the mechanism of <i>n</i>-alkane oxidation could be incorporated into the detailed kinetic model of our previous study, which is specific to the reservoir conditions