Methane Activation on In-Modified ZSM-5 Zeolite. Solid-State NMR Characterization of the Pathways of the Alkane Transformation to Surface Species.
In this paper, we have analyzed in situ the kinetics of H/D exchange of methane with Brønsted acid sites of zeolite H-ZSM-5 modified with indium (In+/H-ZSM-5 and InO+/H-ZSM-5) by 1H MAS NMR and compared this kinetics with the kinetics on the pure acid form of zeolite H-ZSM-5. Surface species formed from methane at elevated temperature have been monitored with 13C CP/MAS NMR spectroscopy. This approach to the study of methane activation on heterogeneous catalysts allowed us to establish some peculiarities of methane activation by Brønsted acid sites and by indium species of In+/H-ZSM-5 and InO+/H-ZSM-5 zeolites, identify reaction intermediates and clarify the pathway of methane involvement in the reaction of ethylene aromatization or the alkylation of benzene with methane.