Purification of\nNitrous Oxide via Thermal Decomposition\nwith the Assistance of Methane: Mechanistic Study of By-Reactions

Efficient and economical purification of nitrous oxide\n(N<sub>2</sub>O), one of the most abundant greenhouse gases, is urgently\nneeded\nto prevent global warming, especially from exhaust emissions produced\nduring adipic acid production. This study investigates the N<sub>2</sub>O thermal decomposition process via high-temperature incineration\n(800–1400 °C), as well as the effects of oxygen (O<sub>2</sub>) and methane (CH<sub>4</sub>) on <i>de</i>N<sub>2</sub>O efficiency and nitrogen selectivity. Under sufficient reaction\nconditions, <i>de</i>N<sub>2</sub>O efficiency reached 100%\nat ∼1000 °C. The introduction of CH<sub>4</sub> was found\nto significantly enhance <i>de</i>N<sub>2</sub>O efficiency,\nwith the addition of 5% CH<sub>4</sub> resulting in complete N<sub>2</sub>O removal at <900 °C. Additionally, the influences\nof O<sub>2</sub> and CH<sub>4</sub> on the products nitric oxide and\nnitrogen dioxide (NO<sub>2</sub>) were analyzed via temperature-programmed\nreaction monitoring. Combined with the energy barriers obtained from\ndensity functional theory calculations, the reaction pathway network\nof N<sub>2</sub>O decomposition with and without CH<sub>4</sub> was\nestablished. Moreover, the reaction rate equation for the crucial\nbyproduct NO<sub>2</sub> was derived from the elementary steps in\nthe reaction network.