Ozone-Assisted Catalytic Alkane Oxidation over Mn/Hydroxyapatite Catalyst at a Precisely-Controlled Total Pressure

Abstract

Ozone-assisted catalytic oxidation (OzCO) and conventional catalytic oxidation (CCO) of alkanes such as propane and methane were investigated over Mn/Hydroxyapatite at 50–450 °C using the innovative LoPOx setup, which enables precise control of the reactor total pressure. Utilizing ozone as the oxidant decreased the required oxidation temperature by up to 300 °C compared to CCO, enabling full propane conversion below 100 °C, with a maximum CO₂ selectivity amounting to 85%. Kinetic analysis revealed distinct propane OzCO stages, transitioning from OzCO-driven conversion (<100 °C) to gas-phase ozonation (100–200 °C), followed by gas-phase ozonation and CCO (200–400 °C), and ultimately CCO (>400 °C). A comparative assessment of propane and methane oxidation revealed that, despite the presence of highly reactive oxygen species, the high C–H bond dissociation energy of methane significantly limited its oxidation. Consequently, although the presence of O₃ effectively enabled low-temperature propane oxidation, it was insufficient for methane abatement under similar conditions.