C-13 NMR spectroscopy of methane adsorbed in SAPO-11 molecular sieve

Static C-13 and C-13-{H-1} NMR spectra of carbon-13 enriched methane ((CH4)-C-13) adsorbed into SAPO-11 molecular sieve were recorded at variable temperatures. Moreover, the corresponding MAS NMR spectra were measured. These experiments reveal a temperature-dependent, anisotropic and asymmetric C-13 nuclear shielding tenser. Ab initio model calculations of methane in the field of a positive point charge suggest that the deformation of the shielding tensor may be related to the interaction between the methane molecule and the charge-compensating protons. A comparison with existing Xe data is made.