Alkali-free ZSM-5 membranes: Preparation conditions and separation performance
Alkali-free, H-ZSM-5 membranes were synthesized by in-situ crystallization on porous {alpha}-alumina, {gamma}-alumina, and stainless steel tubular supports. Membranes prepared from different Si sources were characterized by X-ray diffraction, scanning electron microscopy, and electron probe microanalysis. Membranes prepared under different conditions were also characterized by single-gas permeances of H{sub 2}, N{sub 2}, n-C{sub 4}H{sub 10}, i-C{sub 4}H{sub 10}, and SF{sub 6} and by separation selectivities of n-C{sub 4}H{sub 10}/i-C{sub 4}H{sub 10} mixtures from 300 to 473 K. The effects of preparation procedure, crystallization time and temperature, number of synthesis layers, gel dilution, Si source, and type of support were studied. The permeation and separation properties of the membranes depend strongly on the preparation procedure. Permeating synthesis solution into the pores of the support before hydrothermal treatment allows zeolites crystal growth within those pores. Increasing the crystallization time and temperature increases the n-C{sub 4}H{sub 10}/i-C{sub 4}H{sub 10} separation selectivities, whereas increasing the number of synthesis layers and gel dilution decreases the selectivities. Membranes were prepared with high ideal and separation selectivities for n-C{sub 4}H{sub 10}/i-C{sub 4}H{sub 10}. The highest separation selectivity for n-C{sub 4}H{sub 10}/i-C{sub 4}H{sub 10} is 111, which was obtained at 429 K, and the highest separation selectivity at 473 K is 36. Ideal selectivities do not correlate with mixture selectivities for n-butane/i-butanes at low temperature, but they correlate at 473 K.
- Research Organization:
- Univ. of Colorado, Boulder, CO (US)
- OSTI ID:
- 20000976
- Journal Information:
- Industrial and Engineering Chemistry Research, Journal Name: Industrial and Engineering Chemistry Research Journal Issue: 10 Vol. 38; ISSN IECRED; ISSN 0888-5885
- Country of Publication:
- United States
- Language:
- English
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