Solid-state NMR studies of adsorption complexes and surface methoxy groups on methanol-sorbed microporous materials

摘要

Multinuclear solid-state NMR has been used to study the structure of surface-bonded methanol structures before and after reaction on zeolite K-ZSM-5 and zeotype H-SAPO-34. The results reveal that at low loadings, up to one methanol per acid site, the methanol is adsorbed in two hydrogen bonded configurations. At higher coverages the results suggest methanol clustering with the involvement of one methoxonium ion. After reaction at ca 500 K a variety of surface methoxy groups are observed on both catalysts. NMR is able to differentiate at least four methoxy groups on H-ZSM-5 and the motion of these species is discussed. (C) 1998 Academic Press. [References: 51]