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

Abstract

Chabazite-type Cu-SSZ-13 zeolites can catalyze the continuous selective oxidation of methane (CH 4 ) to methanol (CH 3 OH) under mild conditions using molecular oxygen (O 2 ) 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 CH 3 OH yield by 138% and 68%, respectively, in the continuous CH 4 -to-CH 3 OH 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 Cu 2+ sites to [Cu(OH)] +, the precursor to the binuclear [Cu( trans -μ-1,2-O 2 )Cu] 2+ species, which is highly active for the CH 4 -to-CH 3 OH oxidation.