Preparation and separation properties of silicalite composite membranes
- Univ. of Colorado, Boulder, CO (United States); and others
Silicalite-alumina composite membranes were prepared by an in-situ zeolite synthesis method using an alumina membrane tube with 5-nm diameter pores as a substrate. Both single gas permeations of H{sub 2}, Ar, n-C{sub 4}H{sub 10}, i-C{sub 4}H{sub 10} and SF{sub 6}, and mixture gas separations of H{sub 2}/i-C{sub 4}H{sub 10} and H{sub 2}/SF{sub 6} were carried out to characterize the silicalite membrane properties. These measurements were made from room temperature up to 723 K. For comparison, the alumina membrane without a silicalite layer was also studied. The alumina composite membrane showed T{sup -1/2} temperature dependence expected for Knudsen diffusion, and the separation selectivities were slightly less then values expected from Knudsen diffusion. The permeance of Ar was a factor of 8 lower on the silicalite membrane than on the alumina membrane, but the silicalite composite membrane showed dramatically different behavior. The permeances of all components studied were activated, and activation energies ranged from 8.5 to 16.2 kJ/mol. The ratio of single gas permeances was as high as 170 for H{sub 2} to SF{sub 6}, permeated at 298 K. Separation experiments were performed by either maintaining a pressure drop across the membrane or using an inert sweep gas. The best separation results were obtained by maintaining a pressure drop across the membrane. Separation selectivities were significantly above Knudsen diffusion limitation, but lower than ratios of single gas permeances. The largest permeance ratio for separation was 12.8 for H{sub 2}/i-C{sub 4}H{sub 10} at 583 K.
- OSTI ID:
- 213120
- Report Number(s):
- CONF-940713--
- Country of Publication:
- United States
- Language:
- English
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