Oxidation Kinetics of Methane and Methane/Methanol Mixtures in Supercritical Water

Methanol-assisted oxidation of organic compoundsin supercritical water (SCW) is of interest for wastewatertreatment. To provide better predictive tools for this process, itis important to develop kinetic models. This paper investigated theoxidation kinetics of methane and methane/methanol mixtures inSCW. A detailed chemical kinetic model was established, drawingon the analogy between oxidation chemistry in SCW and the gasphase. The model performance was evaluated against experimentaldata from the literature. Species measurements in supercriticalwater oxidation (SCWO) of methane and methane/methanolmixtures were reproduced satisfactorily by the model. A sensitivityanalysis indicated that hydrogen abstraction from water by HO2and CH3OO, of minor importance in the gas phase, was importantin the SCWO of methane. Compared to the gas phase, SCW facilitated the oxidation of methane by enhancing the production ofOH radicals. Addition of methanol promoted methane oxidation, especially at low temperature, by enhancing the production ofreactive radicals but had little influence on the reaction pathways of the SCWO of methane. Both the present model andAramcoMech 3.0 well predicted the experimental trends, but AramcoMech 3.0 underpredicted the methane oxidation rate atelevated temperature, partly due to the omission of the reaction of CH3OO with H2O in the mechanism

Automated summary

This paper investigated the oxidation kinetics of methane and methane/methanol mixtures in supercritical water and established a detailed chemical kinetic model. The results showed that oxidation reactions in supercritical water have different characteristics compared to the gas phase. The addition of methanol promoted the oxidation of methane, while supercritical water facilitated the oxidation process by enhancing the production of reactive radicals.