13C and 1H MAS NMR Study of Benzene and p-Xylene in Zeolites and a Mesoporous Material FSM-16

• Published in: Bulletin of the Chemical Society of Japan 1997-01, Vol.70 (1), p.97-105
• Main Authors: Satozawa, Masatoshi, Kunimori, Kimio, Hayashi, Shigenobu
• Format: Article
• Language: English
• ISSN: 0009-2673; 1348-0634
• DOI: 10.1246/bcsj.70.97

13C and 1H MAS NMR spectra have been measured at room temperature for benzene and p-xylene adsorbed in H-ZSM-5, Na-, and H-type mordenites with different Si/Al2 ratios, H-Y, Na-Y, Na-X, and FSM-16 to study the dynamics of the guest species in the host materials. The second moments M2 evaluated from the SSB intensity in 13C CP/MAS NMR spectra were used to predict the motion of the guest species. Benzene molecules rotate about the C6 axis freely, and reorientation of the C6 axis takes place in H-ZSM-5. The para axis of p-xylene molecule is fixed in H-ZSM-5. The reorientations of the guest species become isotropic in the faujasite-type zeolites, Na-Y, H-Y, and Na-X. In FSM-16, translation diffusion takes place in addition to the isotropic rotation like in the liquid state. The mobilities of benzene molecules are in the following order, mordenite < H-ZSM-5 < Na-Y < Na-X < H-Y < FSM-16, while those of p-xylene molecules are in the following order. H-ZSM-5 < mordenite < Na-Y < Na-X ≈ H-Y < FSM-16. There is a good correlation between the pore size and the mobility of the guest species, with the exception of the mordenite/benzene systems.