In the studies on enhancing the yield of MTFA, we found that in the reaction of CH4/O2 (2:1, 0.1MPa) the yield of MTFA could be over 30% in 48 hours (Table ). But after that, it increased slowly with the reaction time and/or with the amount of CH4/O2 consumed in the reactor. It is reasonable to believe that both the amount and ratio of NaNO2 (as a catalytic species)/CH4/O2 in a reactor can affect not only the product yield and selectivity but also the reaction rate and lifetime especially in a long reaction time. For example, in the presence of 2.4 mol% NaNO2 (23 μmol) with CH4/O2 (1:5, 35 mL, 0.4 MPa), the yield of MTFA was 91.3% based on methane after 3 days. The methane conversion was 100%, and the byproducts were CH3Cl (7.3%), CH2Cl2 (0.2%) and HCO2H (2%). (Table ). In this case, both more NaNO2 and O2 could enhance the yield of MTFA with a high selectivity. Under the similar conditions, the feed gases containing an inert gas such as nitrogen (CH4/air O2/air N2, 1:5:19) or carbon dioxide (CH4/O2/CO2, 1:5:1) could also produce MTFA in over 73% yield with over 90% selectivity. (Figure , Table ) However, other alkanes such as ethane or cyclohexane are not available in this aerobic oxidation. Over 10% ethane in methane (C2H6/CH4, 1:10) would block the reaction. However, ethane in the mixed gases (C2H6/CH4, 3:7) could be converted to ethyl bromides almost completely by an aerobic bromination system (catalytic NaNO2/HBr/solvent) under visible-light at room temperature, and methane was just lost in less than 5% at the same time. The remaining gas like pure CH4 could undergo the aerobic oxidation smoothly to produce MTFA in 85.4% yield based on methane (Figure ). For the reactions under low pressure, keeping the liquid-phase out of the light was beneficial to reduce byproducts (Table ), which means the aerobic oxidation proceeds in the gas-phase and radical reactions of products may occur in the liquid-phase.