Quasicatalytic and Catalytic Oxidation of Methane to Methanol by Nitrous Oxide over FeZSM-5 Zeolite
Доклады на конференциях
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 alfa-oxygen, CH4 + (FeIII-O•–)alfa, migrated from alfa-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