Insight into the formation of the tert-butyl cation confined inside H-ZSM-5 zeolite from NMR spectroscopy and DFT calculations

Abstract

Solid-state NMR experiments and DFT calculations have been carried out to determine the complex structures of coadsorbed ¹³C-labeled tert-butanol and NH₃ in acidic H-ZSM-5 zeolite. It is found, besides the physically adsorbed tert-butanol/NH₄⁺ complex on Brønsted acid sites, the tert-butylamine cation is formed as well, confirming the presence of the tert-butyl cation confined in zeolite channels. Furthermore, ¹³C–²⁷Al double-resonance solid-state NMR spectroscopy is adopted to determine the host/guest interaction between the carbocation and the zeolite framework.