SOLID-STATE NMR-STUDIES OF ADSORPTION COMPLEXES AND SURFACE METHOXY GROUPS ON METHANOL-SORBED MICROPOROUS MATERIALS

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