Cu-Erionite Zeolite Achieves High Yield in Direct Oxidation of Methane to Methanol by Isothermal Chemical Looping

We herein report that a copper-ion-exchanged erionite zeolite (Cu-ERI) exhibited a methanol yield as high as 147 μmol/g-zeolite, equaling 0.224 μmol/μmol-Cu, in the direct oxidation of methane to methanol. Moreover, this high methanol yield was achieved using an isothermal chemical looping with both oxygen activation and reaction with methane carried out at 300 °C, in contrast to the conventional stepwise protocol where activation is performed at a high temperature (450 °C and above) and the methane reaction at a lower temperature (typically 200 °C). Under isobaric conditions (1 bar), the Cu-ERI still gave a high yield of 80 μmol/g-zeolite after a single aqueous extraction of methanol. Such improvements indicate that high yields can be obtained over Cu-ERI in the direct conversion of methane to methanol by chemical looping without any temperature or pressure swing.