Adsorption complexes of methanol on zeolite ZSM-5

Abstract

Infrared spectroscopy, ¹H MAS NMR and thermogravimetric analysis have been used to study the chemistry of methanol adsorbed on zeolites H-ZSM-5, Na-ZSM-5 and K-ZSM-5. On H-ZSM-5, methanol forms the CH₃OH⁺ ₂ methoxonium ion at low coverages. At higher coverages, large protonated clusters of strongly hydrogen-bonded molecules associated with the Brønsted-acid sites are present. In zeolites Na-ZSM-5 and K-ZSM-5 methanol is coordinatively adsorbed on the cation and forms weakly hydrogen-bonded clusters at higher equilibrium pressures.