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

Methane oxidation by N 2 O 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, CH 4  + (Fe III –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.