Quasicatalytic and catalytic oxidation of methane to methanol by nitrous oxide over FeZSM-5 zeolite

•CH4 oxidation by N2O was studied in quasicatalytic and catalytic modes.•The reaction in both modes proceeds with participation of α-oxygen.•In quasicatalytic mode methanol and dimethyl ether are extracted from the surface.•In catalytic reaction mode, water strongly increases selectivity for methanol.•Quasicatalytic study provides valuable information on the mechanism of catalysis. Methane oxidation by N2O at 200°C and below was shown to proceed in a quasicatalytic mode resulting in product accumulation on FeZSM-5 surface. Methanol that formed via methane oxidation by α-oxygen, CH4+(FeIII–O−)α, migrated from α-sites, initiating new reaction cycles. At 200°C, a 4-h run provided turnover number close to 7. Methanol and dimethyl ether (DME) were the products extracted from the surface. At above 200°C, the reaction moved to conventional catalytic mode with product desorption into gas phase. Water strongly increased methanol selectivity, which attained 62% at 275°C (accounting coke). Contrary to expectations, DME was not detected among the gas-phase products being converted to coke. Comparison of quasicatalytic and catalytic data can provide new information on the reaction mechanism including a possibility of identifying potential intermediates invisible under catalytic conditions. Mechanistic scheme presenting main steps of both reaction modes was suggested.