Long-Range Water Transport and Self-Diffusion in Zeolite 4A Powder Beds
✍ Scribed by P.D.M. Hughes; P.J. McDonald; E.G. Smith
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 139 KB
- Volume
- 121
- Category
- Article
- ISSN
- 1064-1858
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✦ Synopsis
The diffusion of water in industrial-grade sodium zeolite 4A
Small-molecule diffusion in zeolites has long been of conpowder beds has been visualized using broad-line gradient-echo siderable scientific and technological interest because of the magnetic-resonance imaging. Profiles of the equilibration of hyindustrial importance of these materials as molecular sieves drated beds contacting dehydrated beds have been compared with (1). Nuclear magnetic resonance has long played an imhydrated beds contacting beds hydrated with D 2 O in order to portant part in elucidating transport mechanisms, although compare hydration-gradient-driven water-transport diffusion with most work has concentrated on intraparticle processes and self-diffusion. Although the equilibration rates are very different short-range diffusion, using bulk relaxation and pulsed-fieldin the two cases, they are both in agreement with a model of gradient spin-echo diffusion methods (2, 3). Magnetic-resocoupled intraparticle liquid and interparticle vapor diffusion exnance imaging has been used to study long-range transport tended to incorporate the tracer experiments. The extended model in a limited number of systems (4, 5).
is further tested by studies at elevated temperature, reduced hydration levels, and in ammonium-substituted material. ᭧ 1996 Academic In a recent study (6), we showed how broad-line mag-Press, Inc.
netic-resonance imaging could be used to follow long-range water-transport diffusion in beds of industrial-grade zeolite 4A powder. Total water-concentration profiles of the equilibration of dehydrated beds placed in contact with hydrated † To whom correspondence should be addressed.