Multiple Methane Activation Pathways on Ga‐modified ZSM‐5 Zeolites Revealed by Solid‐State NMR Spectroscopy
Xingling Zhao, Jun Xu, Yueying Chu, Guodong Qi, Qiang Wang, Wei Gao, Shenhui Li, Ningdong Feng, Feng Deng
Abstract
Abstract Methane activation on Ga‐modified ZSM‐5 zeolites (Ga/ZSM‐5) was studied by solid‐state NMR spectroscopy. Two types of Ga species, namely highly dispersed oxides and cationic Ga species, were determined by 71 Ga QCPMG NMR. The activation of methane on Ga/ZSM‐5 was explored by using 13 C and 1 H MAS NMR. Four types of Ga‐CH 3 species along with Ga‐OH groups were observed on Ga/ZSM‐5, evidencing different pathways for heterolytic cleavage of C−H bond of methane. Two‐dimensional (2D) 1 H‐ 1 H correlation NMR experiments provide detailed information on the location and local environment of the Ga‐CH 3 species by correlating the protons in Ga‐CH 3 with those in Ga‐OH and other hydroxyls on zeolite. The structures of different Ga‐CH 3 species were further determined by 2D 1 H‐ 13 C heteronuclear correlation NMR experiments, which were supported by theoretical calculations. The activation routes of C−H bond in methane were proposed on Ga/ZSM‐5 zeolite.