Probing the active sites for methane activation on Ga/ZSM-5 zeolites with solid-state NMR spectroscopy

Ga-modified zeolites represent the most effective catalyst for catalytic transformation of light alkanes to aromatics. GaO⁺ ions and GaO_x clusters on Ga/ZSM-5 zeolites are probed by solid-state NMR. These two types of Ga species show strong Lewis acidity and are quantitatively correlated with the catalytic activity of Ga/ZSM-5 for methane C-H bond activation. The interaction between the surface Ga species and zeolite is characterized by using double-resonance solid-state NMR spectroscopy, which provides direct spectroscopic evidence for the location and distribution of active Ga species. These results provide new insight into the understanding of the nature and role of Ga species in Ga-modified zeolites for the conversion of light alkanes.