Tandem Catalysis for Selective Oxidation of Methane to Oxygenates Using Oxygen over PdCu/Zeolite

Selective oxidation of methane to oxygenates with O-2 under mild conditions remains a great challenge. Here we report a ZSM-5 (Z-5) supported PdCu bimetallic catalyst (PdCu/Z-5) for methane conversion to oxygenates by reacting with O-2 in the presence of H-2 at low temperature (120 degrees C). Benefiting from the co-existence of PdO nanoparticles and Cu single atoms via tandem catalysis, the PdCu/Z-5 catalyst exhibited a high oxygenates yield of 1178 mmol g(Pd)(-1) h(-1) (mmol of oxygenates per gram Pd per hour) and at the same time high oxygenates selectivity of up to 95 %. Control experiments and mechanistic studies revealed that PdO nanoparticles promoted the in situ generation of H2O2 from O-2 and H-2, while Cu single atoms not only accelerated the activation of H2O2 for the generation of abundant hydroxyl radicals (OH)-O-center dot) from H2O2 decomposition, but also enabled the homolytic cleavage of CH4 by (OH)-O-center dot to methyl radicals ((CH3)-C-center dot). Subsequently, the (OH)-O-center dot reacted quickly with the (CH3)-C-center dot to form CH3OH with high selectivity.

Automated summary

A bimetallic catalyst PdCu/Z-5 was developed for the selective oxidation of methane to oxygenates at low temperature, achieving high yield and selectivity through the synergistic effect of PdO nanoparticles and Cu single atoms.