Purification of Nitrous Oxide via Thermal Decomposition with the Assistance of Methane: Mechanistic Study of By-Reactions

Efficient and economical purification of nitrous oxide (N2O), one of the most abundant greenhouse gases, is urgently needed to prevent global warming, especially from exhaust emissions produced during adipic acid production. This study investigates the N2O thermal decomposition process via high-temperature incineration (800–1400 °C), as well as the effects of oxygen (O2) and methane (CH4) on deN2O efficiency and nitrogen selectivity. Under sufficient reaction conditions, deN2O efficiency reached 100% at ∼1000 °C. The introduction of CH4 was found to significantly enhance deN2O efficiency, with the addition of 5% CH4 resulting in complete N2O removal at <900 °C. Additionally, the influences of O2 and CH4 on the products nitric oxide and nitrogen dioxide (NO2) were analyzed via temperature-programmed reaction monitoring. Combined with the energy barriers obtained from density functional theory calculations, the reaction pathway network of N2O decomposition with and without CH4 was established. Moreover, the reaction rate equation for the crucial byproduct NO2 was derived from the elementary steps in the reaction network.