High conversion of methane to methyl ester at 298 K

• Published in: Catalysis science & technology Vol. 14; no. 8; pp. 2244 - 2249
• Main Authors: Xu, Lai, Mei, Chong, Zhao, Mengdi, Lu, Wenjun
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 22.04.2024
• Subjects: Methane; Methanol; Oxidation; Reaction mechanisms; Reagents; Room temperature; Sodium nitrite
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/d4cy00048j

To establish an aerobic oxidation of methane to produce methanol with a high yield under ambient conditions is one of the dreams of researchers in academia and industry. However, although a lot of progress has been made on methane functionalization for several decades, it is still a great challenge to break through the selectivity-conversion limit in the aerobic oxidation of methane to methanol or methyl ester especially at room temperature. Herein, we report a simple visible-light driven reaction of CH 4 /O 2 with CF 3 CO 2 H (HTFA) to CH 3 -O-COCF 3 (MTFA) at 298 K, just using catalytic NaNO 2 in an aqueous HCl/HTFA solution. In a batch reaction of CH 4 /O 2 (1 : 5, 0.4 MPa), the yield of MTFA is over 90%. In a 7-day continuous experiment using CH 4 /O 2 (2 : 1, 0.1 MPa), the MTFA selectivity and methane conversion are over 90% based on the methane input. The turnover frequency (TOF) is 2.5 mol MTFA  mol NaNO 2 −1  h −1 , and the turnover number (TON) is over 400. A reasonable reaction mechanism is suggested and partially confirmed by experiments, involving NOCl as a crucial species in the two-phase aerobic oxidation of methane to methyl ester. Methanol could be obtained with a commonly used hydrolysis of MTFA at 298 K. Neither metal catalysts nor special reagents are necessary in this two-step conversion of methane to methanol. An aerobic oxidation of methane with trifluoroacetic acid, based on methane under visible-light at room temperature, produces methyl trifluoroacetate (MTFA) with an 90% yield.