Thermodynamic Insights Into Direct Methane to Methanol Conversion Using O₂ and CO₂ Oxidants

The direct conversion of methane to methanol is a promising alternative for natural gas valorization but remains limited by thermodynamic and kinetic constraints. This study presents a computational thermodynamic analysis of the partial oxidation of methane to methanol performed using Aspen Plus software, comparing O₂ and CO₂ as oxidants. The analysis assesses the effects of temperature (25-600°C), pressure (1, 15, and 30 bar), and oxidant type on key performance metrics, including methane conversion, methanol yield, and methanol selectivity. Results indicate that the optimal operating conditions lie between 300°C and 450°C and at 15 bar, where a balance between conversion and selectivity is achieved. While O₂ enables higher conversion and methanol yield compared to CO₂, it also increases the risk of total oxidation and safety issues. CO₂, although thermodynamically less favorable, offers environmental benefits and greater process control. Coupled reactions involving H₂O₂ as an additional oxidant were evaluated as a strategy to overcome the thermodynamic limitations of CO₂, showing potential to enhance conversion and methanol selectivity under controlled conditions. Overall, these findings define the optimal thermodynamic boundaries for methane-to-methanol conversion and underscore the critical need for tailored catalyst design to overcome kinetic barriers, providing clear guidance for future process integration.