Transition-Metal-Promoted Cu-SSZ-13 Catalysts for Continuous Selective Oxidation of Methane to Methanol Using Molecular Oxygen

Chabazite-type Cu-SSZ-13 zeolites can catalyze the continuous selective oxidation of methane (CH4) to methanol (CH3OH) under mild conditions using molecular oxygen (O2) as the oxidant. Here, we demonstrate that the addition of Fe and Zn into the Cu-SSZ-13 zeolite led to an increase in space–time CH3OH yield by 138% and 68%, respectively, in the continuous CH4-to-CH3OH oxidation reaction. Comparative investigations were conducted over the pristine and Fe-loaded Cu-SSZ-13 zeolites using various ex situ and in situ methods, including X-ray absorption spectroscopy, infrared spectroscopy, ultraviolet–visible spectroscopy, Raman spectroscopy, etc., and revealed that Fe promoted the transformation of Cu2+ sites to [Cu(OH)]+, the precursor to the binuclear [Cu(trans-μ-1,2-O2)Cu]2+ species, which is highly active for the CH4-to-CH3OH oxidation.