Kinetic model and reaction mechanism of lean methane regenerative thermal oxidation: A combined ReaxFF MD and DFT study

GL Li and W Gao and HP Jiang and ZC Huang and XY Si and RJ Si and GC Wen, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 150, 16077-16093 (2025).

DOI: 10.1007/s10973-025-14840-2

Regenerative thermal oxidation (RTO) of lean methane is an environmentally friendly technology for harnessing heat energy. To ensure the safe and effective utilization of lean methane, the mechanism of its RTO process is studied via utilizing the ReaxFF simulation and DFT calculation. The threshold concentration of lean methane from RTO to explosion at a range of 600 similar to 1000 degrees C is also determined by experiments and modeling simulations. The potential energy surface (PES) of main pathways in lean methane RTO is established at M06-2X/6-31 + G**//CCSD(T)/cc-PVTZ level, and the rate constants are obtained by TST/VTST. The identified pathways and rate constants are integrated to a novel kinetic model named MRTO, with an accuracy of 97.59%. The analysis of production rate of key radicals and temperature sensitivity is conducted based on MRTO model. Modeling simulation results indicate that the primary pathways in the threshold process of lean methane from RTO to explosion are: CH4 -> CH3 -> CH3O(/CH2O) -> CH2O -> HCO -> CO -> CO2. Onset of explosion occurs at the initial oxidation phase, transitioning from fuel-rich to fuel-lean, the explosion initiation changes from the generation or consumption of CH3 to CH2O consumption.

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