C-13 NMR of methane in an AlPO4-11 molecular sieve: Exchange effects and shielding anisotropy

C-13 NMR spectra of (CH4)-C-13 in an A1PO(4)-11 molecular sieve reveal exch ange effects between adsorbed and nonadsorbed methane gas. An application o f pulsed field gradients is introduced to decrease nonadsorbed and exchangi ng gas signals in order to extract the chemical shift anisotropy line shape of the adsorbed gas. The resulting C-13 Shielding anisotropy of methane is compared to existing value for methane in related SAPO-II material. Less a nisotropic shielding is observed in AIPO(4)-11, most likely due to the lack of charge compensating cations. [S0163-1829(98)00746-2].