H, 2H, and 13C Solid-State NMR Studies of Methanol Adsorbed on a Series of Acidic Microporous Zeotype Materials

Adsorption of 13 CH 3 OH, CH 3 OD, CD 3 OH, and CD 3 OD on well characterized H-ZSM-5, H-M, H-SAPO-5, FAU type H-Y, and EMT type H-Y microporous materials at various coverages has been studied by using 1 H and 13 C MASNMR. At low methanol coverages the more acidic molecular sieves are able to protonate methanol molecules producing adsorbed methoxonium ions. In less acidic materials hydrogen bonding occurs involving the Brønsted acid site. As the coverage increases methanol clusters form and the bonding within these clusters weakens as demonstrated by the 1 H MASNMR chemical shift trends. This bond weakening gives rise to an increase in mobility of methanol molecules adsorbed within H-ZSM-5 channels and is confirmed by 2 H static wide-line spectra of CH 3 OD adsorbed on D-ZSM-5.