A Spectroscopic Paradox: The Interaction of Methanol with ZSM-5 at Room Temperature

Abstract The adsorption of methanol in HZSM-5 at low temperatures has long been regarded as an associative process involving hydrogen bonding to the acidic zeolite hydroxyl groups. Recent studies employing inelastic neutron scattering spectroscopy (INS) have reported that complete dissociation methoxylate occurs 298 K, and infrared evidence for a partial K also described. Here we investigate apparent contradictions between different techniques, using combination INS, solid-state NMR spectroscopy, including isotopic substitution experiments. Different possible explanations are proposed considered; conclude room temperature is very largely associatively adsorbed, although presence some small extent (>1%) methoxylation cannot be ruled out.