Surface structure and thermodynamics of coals. Quarterly report, October 1, 1989--December 31, 1989
Our work has been the determination of the average micropore diameter of an Argonne Illinois No. 6 coal and a spherocarb sample by {sup 129}Xe NMR. {sup 129}Xe NMR spectroscopy has been used to determine pore sizes and surface characteristics in zeolites. The chemical shift of {sup 129}Xe was measured as a function of pressure and the average micropore diameter was calculated using established techniques. For the spherocarb, the calculated pore diameter of 15.4 CA agrees well with the 0 manufacturer`s reported value of 15{Angstrom}. The Illinois No. 6 coal gave two {sup 129}Xe peaks. Extrapolation of the pressure dependent peak gave a micropore diameter of 5.2{Angstrom}. The other peak was not pressure dependent and is tentatively assigned to Xe dissolved in the coal. The NMR chemical shift of {sup 129}Xe is a useful probe of micropore (<20 {Angstrom} diameter) size and surface characteristics. This application was developed principally by Fraissard and coworkers to determine pore size distributions and the degree of crystallinity in zeolites. The observed {sup 129}Xe NMR chemical shift can be attributed to 4 factors: (1) the number of Xe-Xe collisions; (2) the electric field established by neighboring ions` in the solid sample, found to be negligible for monovalent cations in zeolites; (3) the number of Xe-wall collisions; and (4) the nature of the interaction of Xe with the pore wall. The chemical shift due to Xe-wall collisions can be determined by extrapolation of {sup 129}Xe NMR resonances to 0 Xe pressure.
- Research Organization:
- Lehigh Univ., Bethlehem, PA (United States). Dept. of Chemistry
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC22-89PC89757
- OSTI ID:
- 10174196
- Report Number(s):
- DOE/PC/89757-1; ON: DE92040023
- Resource Relation:
- Other Information: PBD: [1989]
- Country of Publication:
- United States
- Language:
- English
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